The nature of a particular protein depends on the types, number and sequence of amino acids from which it is made. Functions of Proteins
As structural materials proteins-
Are the basic building structures of protoplasms. Proteins in conjunction with lipid form the cell membrane. Examples of structural proteins include:
Keratin (in hair, nails, hoofs, feathers and wool)
Silk in spider's web. Elastin forms ligaments that join bones to each other. Protective proteins. Antibodies that protect the body against foreign antigens. Fribrogen and thrombin are involved in clot formation, preventing entry of micro-organisms when blood vessel is cut. As functional chemical compounds. Examples are hormones and enzymes that act as regulators in the body. Respiratory pigments. Examples are haemoglobin that transports oxygen in the blood and myoglobin that stores up oxygen in muscles. Contractile proteins - make up muscles, i.e. myosin and actin. Proteins combine with other chemical groups to form important substances e.g. mucin in saliva. Source of energy. Proteins are a source of energy in extreme conditions when carbohydrates and fats are not available e.g. in starvation. Enzymes
Enzymes are biological catalysts that increase the rate of chemical reaction in the body. They are all produced inside cells. Some are intracellular and they catalyse reactions within the cells . Others are extracellular and are secreted out of the cells where they work. e.g. digestive enzymes. Properties of Enzymes
Enzymes are protein in nature. Enzymes are specific to the type of reaction they catalyse. This is referred to as substrate specificity. Enzymes work in very small amounts. They remain unchanged after the reaction. They catalyse reversible reactions. They work very fast (high turnover numbers) e.g. the enzyme catalase works on 600 thousand molecules of hydrogen peroxide in one second. Naming of enzymes
Enzymes are named by adding the suffix -ase to:
Name of substrate that they work on e.g. carbohydrates - carbohydrases e.g.sucrase. Starch (amylose) - amylase
Protein - proteinase (protease)
Lipids -lipases
Type of chemical reaction catalised e.g.


Naming of enzymes
Enzymes are named by adding the suffix -ase to:
Name of substrate that they work on e.g. carbohydrates - carbohydrases e.g.sucrase. Starch (amylose) - amylase
Protein - proteinase (protease)
Lipids -lipases
Type of chemical reaction catalised e.g. Oxidation - oxidase
Reduction - reductase
Hydrolysis - hydrolase
Factors Affecting Enzyme Action
Temperature
Enzymes are sensitive to temperature changes. Generally, the rate of an enzymecontrolled reaction doubles with every 10OC increase in temperature. However, temperatures above 40°C do not favour enzyme reaction. This is because enzymes are denatured by high temperatures. pH
Every enzyme has a particular pH range over which it works best. Some enzymes work best in acidic media while others function better in alkaline media. Many enzymes function well under neutral conditions. Enzyme Concentration
Under conditions where the substrate is in excess, the rate of an enzyme-controlled reaction increases as the enzyme concentration is increased. Substrate Concentration
If the concentration of the substrate is increased while that of the enzyme remains constant, the rate of the reaction will increase for sometime and then become constant. Any further increase in substrate concentration will not result in corresponding increase in the rate of the reaction. Enzyme Inhibitors
These are substances that either compete with substrates for enzyme active sites or combine with enzymes and hence they inhibit the enzyme reaction. e.g. certain drugs, cyanide and nerve gas. Co-factors
Most enzymes require the presence of other compounds known as co-factors which are non-proteins. There are three groups of co-factors. Inorganic ions - e.g. iron, magnesium, copper and zinc. Complex organic molecules known as prosthetic groups are attached to the enzyme
e.g. flavin adenine dinucleotide (FAD) derived from vitamin B2 (riboflavin). Co-enzymes e.g. coenzyme A is involved in respiration. All co-enzymes are derived from vitamins. Nutrition in Animals=Heterotrophism
Meaning and Types of Heterotrophism
This is a mode of nutrition whereby organisms feed on complex organic matter from other plants or animals. All animals are heterotrophs.


All co-enzymes are derived from vitamins. Nutrition in Animals=Heterotrophism
Meaning and Types of Heterotrophism
This is a mode of nutrition whereby organisms feed on complex organic matter from other plants or animals. All animals are heterotrophs. Their mode of feeding is also said to be holozoic to distinguish it from other special types of heterotrophic nutrition namely:
saprophytism
parasitism. Saprophytism/saprotrophysim- occurs in most fungi and some forms of bacteria. Saprophytes feed on dead organic matter and cause its decomposition or decay. Parasitism is a mode of feeding whereby one organism called the parasite feeds on or lives in another organism called the host and harms it. Modes of Feeding in Animals
Animals have developed various structures to capture and ingest food. The type of structures present depend on the method of feeding and the type of food. Carnivorous animals feed on whole animals or portions of their flesh. Herbiverous animals feed on plant material. Omnivorous animals feed on both plants and animal materials. Feeding in Mammals
The jaws and teeth of mammals are modified according to the type of food eaten. Mammals have different kinds of teeth. Each type of teeth has a particular role to play in the feeding process. Feeding in Mammals
The jaws and teeth of mammals are modified according to the type of food eaten. Mammals have different kinds of teeth. Each type of teeth has a particular role to play in the feeding process. This condition is described as heterodont. The teeth of reptiles and amphibians are all similar in shape and carry out the same function. They are said to be homodont. Types of Mammalian Teeth
Mammals have four kinds of teeth. The incisors are found at the front of the jaw. They are sharp-edged and are used for biting. The canines are located at the sides of the jaw. They are pointed and are used for tearing and piercing. The premolars are next to the canines and the molars are at the back of the jaw. Both premolars and molars are used for crushing and grinding. Teeth are replaced only once in a lifetime. The first set is the milk or deciduous teeth. These are replaced by the second set or the permanent teeth.


Teeth are replaced only once in a lifetime. The first set is the milk or deciduous teeth. These are replaced by the second set or the permanent teeth. Dentition refers to the type of teeth, the number and their arrangement in the jaw. A dental formula shows the type and number of teeth in each half of the jaw. The number of teeth in half of the upper jaw is represented above a line and those on the lower jaw below the line. The first letter of each type of teeth is used in the formula i.e. i = incisors, c = canines, pm = premolars and m = molars. The total number is obtained by multiplying by two (for the two halves of each jaw). Adaptation of Teeth to Feeding
In general, incisors are for cutting, canines for tearing while premolars and molars are for grinding. However, specific modifications are observed in different mammals as an adaptation to the type of food they eat. Teeth of Herbivores
Incisors are long and flat with a sharp chisellike edge for cutting. The enamel coating is thicker in front than at the back so that as the tooth wears out, a sharp edge is maintained. Canines are reduced or absent. If absent, the space left is called the diastema. The diastema allows the tongue to hold food and push it to the grinding teeth at the back of the mouth. Premolars and molars:
These are transversely ridged. The ridges on the upper teeth fit into grooves on the lower ones. This gives a sideways grinding surface. The teeth of herbivores have open roots i.e., wide opening into the pulp cavity. This ensures a continued adequate supply of food and oxygen to the tooth. In some herbivores, such as rabbits and elephants, the incisors continue to grow throughout life. Teeth of Carnivores
Incisors are reduced in size and pointed. They are well suited for grasping food and holding prey. Canines are long, pointed and curved. They are used for piercing and tearing flesh as well as for attack and defence. Premolars and molars: In general, they are long and longitudinally ridged to increase surface area for crushing . Carnassial Teeth: These are the last premolars on the upper jaw and the first molars on the lower one. They are enlarged for cutting flesh. They act as a pair of shears. They also crush bones.


They are enlarged for cutting flesh. They act as a pair of shears. They also crush bones. The teeth of carnivores have closed roots i.e., only a very small opening of the pulp cavity to allow food and oxygen to keep teeth alive. Once broken, no re-growth can take place. Teeth of Omnivores
Incisors have a wide surface for cutting. Canines are bluntly pointed for tearing. Premolars and molars have cusps for crushing and grinding. The premolars have two blunt cusps while the molars have three to four. Internal Structure of tooth
The tooth consists of two main parts:
Crown: The portion above the gum; it is covered by the enamel. Root: The portion below the gum; it is covered by the cement. The tooth has two roots. Neck: Is the region at the same level with the gum. It forms the junction between the crown and the root. It is covered by enamel. Incisors and canines have one root only. Premolars have one or two roots while molars have two to three roots each. Internally, the bulk of the tooth is made up of dentine which consists of living cells and extends to the root. It is composed of calcium salts, collagen and water. It is harder than bone but wears out with use. This is why it is covered by enamel which is the hardest substance in a mammal's body. Pulp Cavity: Contains blood vessels which provide nutrients to the dentine and remove waste products. It also contains nerve endings which detect heat, cold and pain. Cement: Fixes the tooth firmly to the jaw bone. Common Dental Diseases
Dental Carries
Dental carries are the holes or cavities that are formed as acid corrodes enamel and eventually the dentine. Causes
This is caused by bacteria acting on the food left between teeth and on the cusp. Acids are formed that eventually corrode the enamel. The pulp cavity is eventually reached. A lot of pain is experienced then. The bacteria then infect the pulp cavity and the whole tooth decays. Treatment
Treatment depends on the extent of the dental caries:
Extraction of Tooth. Filling - this involves replacing the dentine with amalgam, a mixture of hard elements e.g. silver and tin. Root Canal Treatment - This involves surgery and reconstruction. It saves severely damaged teeth. The nerves in the root canal are surgically severed. The tooth is cleaned and filled up with amalgam.


It saves severely damaged teeth. The nerves in the root canal are surgically severed. The tooth is cleaned and filled up with amalgam. Periodontal Diseases
These are diseases of the gum. The gum becomes inflamed, and starts bleeding. Progression of the disease leads to infection of the fibres in the periodontal membranes and the tooth becomes loose. This condition is known as pyorrhoea. The diseases are caused by poor cleaning of the teeth. The accumulation of food particles leading to formation of plaque, lack of adequate vitamin A and C in the diet. Treatment
Nutrition - by taking adequate balanced diet rich in vitamins A and C. Antibiotics are used to kill bacteria. Anti-inflamatory drugs are given. Antiseptic is prescribed to use in cleaning the mouth daily to prevent further proliferation of bacteria. The plaque is removed-drilled away - a procedure known as scaling. Care of Teeth
In order to maintain healthy teeth the following points should be observed:
A proper diet that includes calcium and vitamins, particularly vitamin D is essential. The diet should also contain very small quantities of fluorine to strengthen the enamel. Large quantities of fluorine are harmful. The enamel becomes brown, a condition known as dental flourosis. Chewing of hard fibrous foods like carrots and sugar cane to strengthen and cleanse the teeth. Proper use of teeth e.g. not using teeth to open bottles and cut thread. Regular and thorough brushing of teeth after meals. Dental floss can be used to clean between the teeth. Not eating sweets and sugary foods between meals. Regular visits to the dentist for checkup. Washing the mouth with strong salt solution or with any other mouth wash with antiseptic properties. Digestive System and Digestion in Humans
Organs that are involved with feeding in humans constitute the digestive system. Digestive System and Associated Glands
Human digestive system starts at the mouth and ends at the anus. This is the alimentary canal. Digestion takes place inside the lumen of the alimentary canal. The epithelial wall that faces the lumen has mucus glands (goblet cells). These secrete mucus that lubricate food and prevent the wall from being digested by digestive enzymes. Present at specific regions are glands that secrete digestive enzymes. The liver and pancreas are organs that are closely associated with the alimentary canal. Their secretions get into the lumen and assist in digestions. Digestive system consists of:
Mouth.


The liver and pancreas are organs that are closely associated with the alimentary canal. Their secretions get into the lumen and assist in digestions. Digestive system consists of:
Mouth. Oesophagus. Stomach. Small intestines - consist of duodenum, the first part next to the stomach, ileum - the last part that ends up in a vestigial caecum and appendix which are nonfunctional. Large intestines consist of: colon and rectum that ends in the anus. Ingestion, Digestion and Absorption
Feeding in humans involves the following processes:
Ingestion: This is the introduction of the food into the mouth. Digestion: This is the mechanical and chemical breakdown of the food into simpler, soluble and absorbable units. Absorption: Taking into blood the digested products. Assimilation: Use of food in body cells. Mechanical breakdown of the food takes place with the help of the teeth. Chemical digestion involves enzymes. Digestion in the Mouth
In the mouth, both mechanical and chemical digestion takes place. Food is mixed with saliva and is broken into smaller particles by the action of teeth. Saliva contains the enzyme amylase. It also contains water and mucus which lubricate and soften food in order to make swallowing easy. Saliva is slightly alkaline and thus provides a suitable pH for amylase to act on cooked starch, changing it to maltose. The food is then swallowed in the form of semisolid balls known as boluses. Each bolus moves down the oesophagus by a process known as peristalsis. Circular and longitudinal muscles along the wall of the alimentary canal contract and relax pushing the food along. Digestion in the Stomach
In the stomach, the food is mixed with gastric juice secreted by gastric glands in the stomach wall. Gastric juice contains pepsin, rennin and hydrochloric acid. The acid provides a low pH of 1.5-2.0 suitable for the action of pepsin. Pepsin breaks down protein into peptides. Rennin coagulates the milk protein casein. The stomach wall has strong circular and longitudinal muscles whose contraction mixes the food with digestive juices in the stomach. Digestion in the Duodenum
In the duodenum the food is mixed with bile and pancreatic juice. Bile contains bile salts and bile pigments.


The stomach wall has strong circular and longitudinal muscles whose contraction mixes the food with digestive juices in the stomach. Digestion in the Duodenum
In the duodenum the food is mixed with bile and pancreatic juice. Bile contains bile salts and bile pigments. The salts emulsify fats, thus providing a large surface area for action of lipase. Pancreatic juice contains three enzymes:
Trypsin which breaks down proteins into peptides and amino acids,
Amylase which breaks down starch into maltose, and
Lipase which breaks down lipids into fatty acids and glycerol. These enzymes act best in an alkaline medium which is provided for by the bile. Digestion in ileum
Epithelial cells in ileum secrete intestinal juice, also known as succus entericus. This contains enzymes which complete the digestion of protein into amino acids, carbohydrates into monosaccharides and lipids into fatty acids and glycerol. Absorption
This is the diffusion of the products of digestion into the blood of the animal. It takes place mainly in the small intestines though alcohol and some glucose are absorbed in the stomach. The ileum is adapted for absorption in the following ways:
It is highly coiled. The coiling ensures that food moves along slowly to allow time for its digestion and absorption. It is long to provide a large surface area for absorption. The epithelium has many finger-like projections called villi (singular villus). They greatly increase the surface area for absorption. Villi have microvilli that further increase the surface area for absorption. The wall of villi has thin epithelial lining to facilitate fast diffusion of products of digestion. Has numerous blood vessels for transport of the end products of digestion. Has lacteal vessels; for absorption of fatty acids and glycerol and transport of lipids. Absorption of Glucose and Amino Acids
Glucose and other monosaccharides as well as amino acids are absorbed through the villi epithelium and directly into the blood capillaries. First they are carried to the liver through the hepatic portal vein, then taken to all organs via circulatory system. Absorption of Fatty Acids and Glycerol
Fatty acids and glycerol diffuse through the epithelial cells of villi and into the lacteal.


Absorption of Glucose and Amino Acids
Glucose and other monosaccharides as well as amino acids are absorbed through the villi epithelium and directly into the blood capillaries. First they are carried to the liver through the hepatic portal vein, then taken to all organs via circulatory system. Absorption of Fatty Acids and Glycerol
Fatty acids and glycerol diffuse through the epithelial cells of villi and into the lacteal. When inside the villi epithelial cells, the fatty acids combine with glycerol to make tiny fat droplets which give the lacteal a milky appearance. The lacteals join the main lymph vessel that empties its contents into the bloodstream in the thoracic region. Once inside the blood, the lipid droplets are hydrolysed to fatty acids and glycerol. Absorption of Vitamins and Mineral Salts
Vitamins and mineral salts are absorbed into the blood capillaries in' the villi. Water is mainly absorbed in the colon. As a result the undigested food is in a semi-solid form (faeces) when it reaches the rectum. Egestion: This is removal of undigested or indigestible material from the body. Faeces are temporarily stored in the rectum then voided through the anus. Opening of the anus is controlled by sphincter muscles
Assimilation: This is the incorporation of the food into the cells where it is used for various chemical processes. Carbohydrates
used to provide energy for the body. Excess glucose is converted to glycogen and stored in the liver and muscles. Some of the excess carbohydrates are also converted into fat in the liver and stored in the adipose tissue' (fat storage tissue), in the mesenteries and in the connective tissue under the skin, around the heart and other internal organs. Proteins
Amino acids are used to build new cells and repair worn out ones. They are also used for the synthesis of protein compounds. Excess amino acids are de-aminated in the liver. Urea is formed from the nitrogen part. The remaining carbohydrate portion is used for energy or it is converted to glycogen or fat and stored. Lipids
Fats are primarily stored in the fat storage tissues. When carbohydrates intake is low in the body, fats are oxidised to provide energy. They are also used as structural materials e.g.


Lipids
Fats are primarily stored in the fat storage tissues. When carbohydrates intake is low in the body, fats are oxidised to provide energy. They are also used as structural materials e.g. phospholipids in cell membrane. They act as cushion, protecting delicate organs like the heart. Stored fats under the skin act as heat insulators. Summary of digestion in humans
Importance of Vitamins, Mineral Salts, Roughage and Water in Human Nutrition
Vitamins
These are organic compounds that are essential for proper growth, development and functioning of the body. Vitamins are required in very small quantities. They are not stored and must be included in the diet. Vitamins Band C are soluble in water, the rest are soluble in fat. Various vitamins are used in different ways. Mineral Salts
Mineral ions are needed in the human body. Some are needed in small amounts while others are needed in very small amounts (trace). All are vital to human health. Nevertheless, their absence results in noticeable mulfunction of the body processes. Water
Water is a constituent of blood and intercellular fluid. It is also a constituent of cytoplasm. Water makes up to 60-70% of total fresh weight in humans. No life can exist without water. Functions of Water
Acts as a medium in which chemical reactions in the body takes place. Acts as a solvent and it is used to transport materials within the body. Acts as a coolant due to its high latent heat of vaporisation. Hence, evaporation of sweat lowers body temperature. Takes part in chemical reactions i.e. hydrolysis. Vitamins, sources, uses and the deficiency disease resulting from their absence in diet
Roughage
Roughage is dietary fibre and it consists mainly of cellulose. It adds bulk to the food and provides grip for the gut muscles to enhance peristalsis. Roughage does not provide any nutritional value because humans and all animals not produce cellulase enzyme to digest cellulose. In herbivores symbiotic bacteria in the gut produce cellulase that digests cellulose. Factors Determining Energy Requirements in Humans
Age: Infants, for instance, need a greater proportion of protein than adults. Sex: males generally require more carbohydrates than females. The requirements of specific nutrients for females depends on the stage of development in the life cycle.


Factors Determining Energy Requirements in Humans
Age: Infants, for instance, need a greater proportion of protein than adults.

Sex: males generally require more carbohydrates than females.

The requirements of specific nutrients for females depends on the stage of development in the life cycle.

Adolescent girls require more iron in their diet; expectant and nursing mothers require a lot of proteins and mineral salts.

State of Health: A sick individual requires more of certain nutrients e.g.

proteins, than a healthy one.

Occupation: An office worker needs less nutrients than a manual worker.

Balanced Diet
A diet is balanced when it contains all the body's nutrient requirements and in the right amounts or proportions.

A balanced diet should contain the following:
Carbohydrates
Proteins
Lipids
Vitamins
Mineral Salts
Water
Dietary fibre or roughage
Malnutrition
This is faulty or bad feeding where the intake of either less or more than the required amount of food or total lack of some food components.

Deficiency Diseases
Deficiency diseases result from prolonged absence of certain components in the diet.

Examples are:
Marasmus:
Lack of enough food reuslts in thin arms and legs,
severe loss of fluid,
general body wasting
sunken eyes.

Kwashiorkor –
Lack of protein in the diet of children.

The symptoms of kwashiorkor include wasting of the body, red thin hair, swollen abdomen and scaly skin.

Other deficiency diseases are due to lack of accessory food factors (vitamins and mineral salts.).

Such diseases include rickets, goitre and anaemia.

Treatment of these deficiency diseases is by supplying the patient with the component missing in the diet.

THE END
Practical Activities
Experiments to show that Carbon (IV) Oxide is necessary for Photosynthesis
Experiment to Show Effect of Light on Photosynthesis
Experiment to Show the Effect of Chlorophyll on Photosynthesis
Experiment To Observe Stomata Distribution in Different Leaves
Test for Reducing Sugar
Test for non-reducing sugar
Test for Lipids;
(a) Grease Spot Test
(b) Emulsion Test
Test for Proteins -Biuret Test
Experiment To Investigate Presence of Enzyme in Living Tissue
Dissection of a Rabbit to show the Digestive System


FORM FOUR BIOLOGY
Define the term genetics
Differentiate between heredity and variation
Distinguish between continuous and discontinuous variations
Describe continuous and discontinuous variations
Observe variations in plants and animals
Describe the structure, nature and properties of chromosomes
Describe the structure, nature and properties of DNA molecule
Differentiate between DNA and RNA
Distinguish between F1 and F2 generation
Determine Mendel’s first law of inheritance
Define other terms used in inheritance such as phenotype, genotype, dominant gene, recessive gene, haploid and diploid
Demonstrate monohybrid inheritance in plants and animals
Predict outcomes of various genetic crosses
Construct and make use of pannet squares
Work out genotypic and phenotypic ratios
Predict outcomes of various crosses
Determine the unknown genotypes in a cross using a test cross
Describe albinism as an example of monohybrid inheritance in human beings
Explain the inheritance of ABO blood groups in human beings
Explain the inheritance of rhesus factor as an example of monohybrid inheritance in human beings
Predict the inheritance of blood groups human beings
Describe incomplete dominance
Describe inheritance of colour in flowers of mirabilis jalapa
Describe Inheritance of sickle cell anemia in human beings
Explain how sex is determined in human beings
Describe sex linkages in human beings
Define linkage and sex-linkage
Describe linkage in human beings e.g.colour blindness and hemophilia
Describe colour blindness as an example of sex-linked trait in human beings
Interpret pedigree of inheritance
Describe the Inheritance of hemophilia as an example of sex-linked traits in human beings
Define mutation
Differentiate between mutations and mutagens
List down causes of mutations
State the types of mutations
List down the various chromosal mutations
Describe chromosal mutations
Explain the Effects of chromosal mutations
Describe gene mutations and their effects on organisms
Describe areas in which the knowledge of genetics has been applied
Explain the practical applications of genetics
Define evolution
Explain the current concepts of the origin of life
Explain the current concepts on origin of life
Describe the study of fossils as evidence of organic evolution theory
Describe comparative anatomy as evidence of organic evolution
Describe occurrence of vestigial structures and geographical distribution of organisms as evidence of organic evolution
Describe comparative embryology, cell biology and biochemistry as evidence of organic evolution
Describe evolution of hominids
Describe Lamarck’s theory
Describe and discuss the struggle for existence and survival for the fittest
Describe and discuss new concepts of Darwin’s theory
Describe natural selection in action
Describe natural selection in nature
Describe the isolation mechanism in speciation
Describe Artificial selection in plants and animals and how it leads to speciation
Explain the importance of sexual reproduction in evolution
Define stimulus
Define irritability
Define response
Define tactic and tropic responses
List down tactic responses in plants
List down tropic responses in plants
Differentiate between tactic and tropic responses
Define geotropism
Describe geotropism in roots and shoots of plants
Differentiate between Phototropism and geotropism
Carry out experiments demonstrating both Phototropism and geotropism in a plant seedling
Carry out experiments to demonstrate tactic responses to light and water
Carry out experiments to show chemotactic response using fruit juice
Define Hydrotropism and thigmotropism
State the importance of Tactic and tropic responses
Explain the production of Plant hormones and their effects on plants
Carry out experiment to investigate hydrotropism
Carry out experiment to investigate etiolation
Demonstrate the knee jerk in a reflex action
Defined Conditioned reflex actions
Describe Conditioned reflex action using parlous dog
Compare simple and conditioned reflex actions
Explain the role of endocrine system in a human being
Explain the effect over secretion and under secretion of thyroxin and adrenaline
Isolate and list the similarities and differences between the endocrine and the nervous system
State the effects of drug abuse on human health
Draw and label the mammalian eye
State the functions of the mammalian eye
Describe how the structure of the mammalian eye is adapted to its functions
Dissect and display parts of the mammalian eye
Describe how an image is formed and interpreted in the mammalian eye
Describe Accommodation in the mammalian eye
Name and explain the Common eye defects
Describe Common eye defects and their corrections
Investigate the blind spot In the eye
Investigate which eye is used more during vision
Name and describe Common eye diseases
Draw and label the mammalian ear
Describe the mammalian ear and how it is adapted to its functions
Describe the mechanism of hearing
Discuss thick ear drum, damaged cochlea, raptured eardrum, fussed ossicles, otitis media, ostosceleross and tinnitus
Define support and movement
Describe the necessity of movement in plants and animals
Review the tissue distribution in monocotyledonous an dicotyledonous plants
Describe support in woody and non-woody stems
Describe the role of tendrils and tender stems in support
Observe prepared sections of woody and herbaceous stems
Observe a wilting plant
List the types of skeletons
Describe the role of exoskeleton in insects
Describe the role and components of endoskeleton
Describe the role of skeleton in vertebrates
Draw the structure of a finned fish (tilapia)
Calculate the tail power
Explain how locomotion occurs in fish
Name and draw the different fins and state their functions
Draw the human skeleton and identify the component parts
Identify and draw the skull
Identify bones of Axial skeleton in the vertebral column
Identify the cervical vertebrae
Identify the structures of the thoracic vertebrae
Relate the structure of the thoracic vertebrae to their functions
Identify the structures of lumbar, sacral and candal vertebrae
Show how ribs articulate with thoracic vertebrae
Draw and label Ribs and sternum
Relate the structure to their functions
Identify components of Appendicular skeleton
Draw the scapula bone and relate it to its functions
Identify the bones of the fore limbs
Draw the structure of the humerus, radius and ulna
Draw and label bones of the hand
Draw the pelvic girdle
Name the bones of The pelvic girdle
Relate the structure to their functions
Identify, draw and label the femur, tibia and tibula bones
Relate their structure to their functions
Draw and label the bones of the foot
Relate the structure of bones of the foot to their functions
Define a joint
List the three types of joints
Describe the types of joints
List examples of movable joints, hinge joints and bell and socket joints
Define Immovable joints
Name Immovable joints
Define muscles
Explain the differences between the three types of muscles
Identifying biceps and triceps in the arm movement
Genetics
Introduction
Genetics is the study of inheritance.


FORM FOUR BIOLOGY
Define the term genetics
Differentiate between heredity and variation
Distinguish between continuous and discontinuous variations
Describe continuous and discontinuous variations
Observe variations in plants and animals
Describe the structure, nature and properties of chromosomes
Describe the structure, nature and properties of DNA molecule
Differentiate between DNA and RNA
Distinguish between F1 and F2 generation
Determine Mendel’s first law of inheritance
Define other terms used in inheritance such as phenotype, genotype, dominant gene, recessive gene, haploid and diploid
Demonstrate monohybrid inheritance in plants and animals
Predict outcomes of various genetic crosses
Construct and make use of pannet squares
Work out genotypic and phenotypic ratios
Predict outcomes of various crosses
Determine the unknown genotypes in a cross using a test cross
Describe albinism as an example of monohybrid inheritance in human beings
Explain the inheritance of ABO blood groups in human beings
Explain the inheritance of rhesus factor as an example of monohybrid inheritance in human beings
Predict the inheritance of blood groups human beings
Describe incomplete dominance
Describe inheritance of colour in flowers of mirabilis jalapa
Describe Inheritance of sickle cell anemia in human beings
Explain how sex is determined in human beings
Describe sex linkages in human beings
Define linkage and sex-linkage
Describe linkage in human beings e.g.colour blindness and hemophilia
Describe colour blindness as an example of sex-linked trait in human beings
Interpret pedigree of inheritance
Describe the Inheritance of hemophilia as an example of sex-linked traits in human beings
Define mutation
Differentiate between mutations and mutagens
List down causes of mutations
State the types of mutations
List down the various chromosal mutations
Describe chromosal mutations
Explain the Effects of chromosal mutations
Describe gene mutations and their effects on organisms
Describe areas in which the knowledge of genetics has been applied
Explain the practical applications of genetics
Define evolution
Explain the current concepts of the origin of life
Explain the current concepts on origin of life
Describe the study of fossils as evidence of organic evolution theory
Describe comparative anatomy as evidence of organic evolution
Describe occurrence of vestigial structures and geographical distribution of organisms as evidence of organic evolution
Describe comparative embryology, cell biology and biochemistry as evidence of organic evolution
Describe evolution of hominids
Describe Lamarck’s theory
Describe and discuss the struggle for existence and survival for the fittest
Describe and discuss new concepts of Darwin’s theory
Describe natural selection in action
Describe natural selection in nature
Describe the isolation mechanism in speciation
Describe Artificial selection in plants and animals and how it leads to speciation
Explain the importance of sexual reproduction in evolution
Define stimulus
Define irritability
Define response
Define tactic and tropic responses
List down tactic responses in plants
List down tropic responses in plants
Differentiate between tactic and tropic responses
Define geotropism
Describe geotropism in roots and shoots of plants
Differentiate between Phototropism and geotropism
Carry out experiments demonstrating both Phototropism and geotropism in a plant seedling
Carry out experiments to demonstrate tactic responses to light and water
Carry out experiments to show chemotactic response using fruit juice
Define Hydrotropism and thigmotropism
State the importance of Tactic and tropic responses
Explain the production of Plant hormones and their effects on plants
Carry out experiment to investigate hydrotropism
Carry out experiment to investigate etiolation
Demonstrate the knee jerk in a reflex action
Defined Conditioned reflex actions
Describe Conditioned reflex action using parlous dog
Compare simple and conditioned reflex actions
Explain the role of endocrine system in a human being
Explain the effect over secretion and under secretion of thyroxin and adrenaline
Isolate and list the similarities and differences between the endocrine and the nervous system
State the effects of drug abuse on human health
Draw and label the mammalian eye
State the functions of the mammalian eye
Describe how the structure of the mammalian eye is adapted to its functions
Dissect and display parts of the mammalian eye
Describe how an image is formed and interpreted in the mammalian eye
Describe Accommodation in the mammalian eye
Name and explain the Common eye defects
Describe Common eye defects and their corrections
Investigate the blind spot In the eye
Investigate which eye is used more during vision
Name and describe Common eye diseases
Draw and label the mammalian ear
Describe the mammalian ear and how it is adapted to its functions
Describe the mechanism of hearing
Discuss thick ear drum, damaged cochlea, raptured eardrum, fussed ossicles, otitis media, ostosceleross and tinnitus
Define support and movement
Describe the necessity of movement in plants and animals
Review the tissue distribution in monocotyledonous an dicotyledonous plants
Describe support in woody and non-woody stems
Describe the role of tendrils and tender stems in support
Observe prepared sections of woody and herbaceous stems
Observe a wilting plant
List the types of skeletons
Describe the role of exoskeleton in insects
Describe the role and components of endoskeleton
Describe the role of skeleton in vertebrates
Draw the structure of a finned fish (tilapia)
Calculate the tail power
Explain how locomotion occurs in fish
Name and draw the different fins and state their functions
Draw the human skeleton and identify the component parts
Identify and draw the skull
Identify bones of Axial skeleton in the vertebral column
Identify the cervical vertebrae
Identify the structures of the thoracic vertebrae
Relate the structure of the thoracic vertebrae to their functions
Identify the structures of lumbar, sacral and candal vertebrae
Show how ribs articulate with thoracic vertebrae
Draw and label Ribs and sternum
Relate the structure to their functions
Identify components of Appendicular skeleton
Draw the scapula bone and relate it to its functions
Identify the bones of the fore limbs
Draw the structure of the humerus, radius and ulna
Draw and label bones of the hand
Draw the pelvic girdle
Name the bones of The pelvic girdle
Relate the structure to their functions
Identify, draw and label the femur, tibia and tibula bones
Relate their structure to their functions
Draw and label the bones of the foot
Relate the structure of bones of the foot to their functions
Define a joint
List the three types of joints
Describe the types of joints
List examples of movable joints, hinge joints and bell and socket joints
Define Immovable joints
Name Immovable joints
Define muscles
Explain the differences between the three types of muscles
Identifying biceps and triceps in the arm movement
Genetics
Introduction
Genetics is the study of inheritance. The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring.


FORM FOUR BIOLOGY
Define the term genetics
Differentiate between heredity and variation
Distinguish between continuous and discontinuous variations
Describe continuous and discontinuous variations
Observe variations in plants and animals
Describe the structure, nature and properties of chromosomes
Describe the structure, nature and properties of DNA molecule
Differentiate between DNA and RNA
Distinguish between F1 and F2 generation
Determine Mendel’s first law of inheritance
Define other terms used in inheritance such as phenotype, genotype, dominant gene, recessive gene, haploid and diploid
Demonstrate monohybrid inheritance in plants and animals
Predict outcomes of various genetic crosses
Construct and make use of pannet squares
Work out genotypic and phenotypic ratios
Predict outcomes of various crosses
Determine the unknown genotypes in a cross using a test cross
Describe albinism as an example of monohybrid inheritance in human beings
Explain the inheritance of ABO blood groups in human beings
Explain the inheritance of rhesus factor as an example of monohybrid inheritance in human beings
Predict the inheritance of blood groups human beings
Describe incomplete dominance
Describe inheritance of colour in flowers of mirabilis jalapa
Describe Inheritance of sickle cell anemia in human beings
Explain how sex is determined in human beings
Describe sex linkages in human beings
Define linkage and sex-linkage
Describe linkage in human beings e.g.colour blindness and hemophilia
Describe colour blindness as an example of sex-linked trait in human beings
Interpret pedigree of inheritance
Describe the Inheritance of hemophilia as an example of sex-linked traits in human beings
Define mutation
Differentiate between mutations and mutagens
List down causes of mutations
State the types of mutations
List down the various chromosal mutations
Describe chromosal mutations
Explain the Effects of chromosal mutations
Describe gene mutations and their effects on organisms
Describe areas in which the knowledge of genetics has been applied
Explain the practical applications of genetics
Define evolution
Explain the current concepts of the origin of life
Explain the current concepts on origin of life
Describe the study of fossils as evidence of organic evolution theory
Describe comparative anatomy as evidence of organic evolution
Describe occurrence of vestigial structures and geographical distribution of organisms as evidence of organic evolution
Describe comparative embryology, cell biology and biochemistry as evidence of organic evolution
Describe evolution of hominids
Describe Lamarck’s theory
Describe and discuss the struggle for existence and survival for the fittest
Describe and discuss new concepts of Darwin’s theory
Describe natural selection in action
Describe natural selection in nature
Describe the isolation mechanism in speciation
Describe Artificial selection in plants and animals and how it leads to speciation
Explain the importance of sexual reproduction in evolution
Define stimulus
Define irritability
Define response
Define tactic and tropic responses
List down tactic responses in plants
List down tropic responses in plants
Differentiate between tactic and tropic responses
Define geotropism
Describe geotropism in roots and shoots of plants
Differentiate between Phototropism and geotropism
Carry out experiments demonstrating both Phototropism and geotropism in a plant seedling
Carry out experiments to demonstrate tactic responses to light and water
Carry out experiments to show chemotactic response using fruit juice
Define Hydrotropism and thigmotropism
State the importance of Tactic and tropic responses
Explain the production of Plant hormones and their effects on plants
Carry out experiment to investigate hydrotropism
Carry out experiment to investigate etiolation
Demonstrate the knee jerk in a reflex action
Defined Conditioned reflex actions
Describe Conditioned reflex action using parlous dog
Compare simple and conditioned reflex actions
Explain the role of endocrine system in a human being
Explain the effect over secretion and under secretion of thyroxin and adrenaline
Isolate and list the similarities and differences between the endocrine and the nervous system
State the effects of drug abuse on human health
Draw and label the mammalian eye
State the functions of the mammalian eye
Describe how the structure of the mammalian eye is adapted to its functions
Dissect and display parts of the mammalian eye
Describe how an image is formed and interpreted in the mammalian eye
Describe Accommodation in the mammalian eye
Name and explain the Common eye defects
Describe Common eye defects and their corrections
Investigate the blind spot In the eye
Investigate which eye is used more during vision
Name and describe Common eye diseases
Draw and label the mammalian ear
Describe the mammalian ear and how it is adapted to its functions
Describe the mechanism of hearing
Discuss thick ear drum, damaged cochlea, raptured eardrum, fussed ossicles, otitis media, ostosceleross and tinnitus
Define support and movement
Describe the necessity of movement in plants and animals
Review the tissue distribution in monocotyledonous an dicotyledonous plants
Describe support in woody and non-woody stems
Describe the role of tendrils and tender stems in support
Observe prepared sections of woody and herbaceous stems
Observe a wilting plant
List the types of skeletons
Describe the role of exoskeleton in insects
Describe the role and components of endoskeleton
Describe the role of skeleton in vertebrates
Draw the structure of a finned fish (tilapia)
Calculate the tail power
Explain how locomotion occurs in fish
Name and draw the different fins and state their functions
Draw the human skeleton and identify the component parts
Identify and draw the skull
Identify bones of Axial skeleton in the vertebral column
Identify the cervical vertebrae
Identify the structures of the thoracic vertebrae
Relate the structure of the thoracic vertebrae to their functions
Identify the structures of lumbar, sacral and candal vertebrae
Show how ribs articulate with thoracic vertebrae
Draw and label Ribs and sternum
Relate the structure to their functions
Identify components of Appendicular skeleton
Draw the scapula bone and relate it to its functions
Identify the bones of the fore limbs
Draw the structure of the humerus, radius and ulna
Draw and label bones of the hand
Draw the pelvic girdle
Name the bones of The pelvic girdle
Relate the structure to their functions
Identify, draw and label the femur, tibia and tibula bones
Relate their structure to their functions
Draw and label the bones of the foot
Relate the structure of bones of the foot to their functions
Define a joint
List the three types of joints
Describe the types of joints
List examples of movable joints, hinge joints and bell and socket joints
Define Immovable joints
Name Immovable joints
Define muscles
Explain the differences between the three types of muscles
Identifying biceps and triceps in the arm movement
Genetics
Introduction
Genetics is the study of inheritance. The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring. Factors that determine characters (genes) are passed on from parent to offspring through gametes or sex cells.


FORM FOUR BIOLOGY
Define the term genetics
Differentiate between heredity and variation
Distinguish between continuous and discontinuous variations
Describe continuous and discontinuous variations
Observe variations in plants and animals
Describe the structure, nature and properties of chromosomes
Describe the structure, nature and properties of DNA molecule
Differentiate between DNA and RNA
Distinguish between F1 and F2 generation
Determine Mendel’s first law of inheritance
Define other terms used in inheritance such as phenotype, genotype, dominant gene, recessive gene, haploid and diploid
Demonstrate monohybrid inheritance in plants and animals
Predict outcomes of various genetic crosses
Construct and make use of pannet squares
Work out genotypic and phenotypic ratios
Predict outcomes of various crosses
Determine the unknown genotypes in a cross using a test cross
Describe albinism as an example of monohybrid inheritance in human beings
Explain the inheritance of ABO blood groups in human beings
Explain the inheritance of rhesus factor as an example of monohybrid inheritance in human beings
Predict the inheritance of blood groups human beings
Describe incomplete dominance
Describe inheritance of colour in flowers of mirabilis jalapa
Describe Inheritance of sickle cell anemia in human beings
Explain how sex is determined in human beings
Describe sex linkages in human beings
Define linkage and sex-linkage
Describe linkage in human beings e.g.colour blindness and hemophilia
Describe colour blindness as an example of sex-linked trait in human beings
Interpret pedigree of inheritance
Describe the Inheritance of hemophilia as an example of sex-linked traits in human beings
Define mutation
Differentiate between mutations and mutagens
List down causes of mutations
State the types of mutations
List down the various chromosal mutations
Describe chromosal mutations
Explain the Effects of chromosal mutations
Describe gene mutations and their effects on organisms
Describe areas in which the knowledge of genetics has been applied
Explain the practical applications of genetics
Define evolution
Explain the current concepts of the origin of life
Explain the current concepts on origin of life
Describe the study of fossils as evidence of organic evolution theory
Describe comparative anatomy as evidence of organic evolution
Describe occurrence of vestigial structures and geographical distribution of organisms as evidence of organic evolution
Describe comparative embryology, cell biology and biochemistry as evidence of organic evolution
Describe evolution of hominids
Describe Lamarck’s theory
Describe and discuss the struggle for existence and survival for the fittest
Describe and discuss new concepts of Darwin’s theory
Describe natural selection in action
Describe natural selection in nature
Describe the isolation mechanism in speciation
Describe Artificial selection in plants and animals and how it leads to speciation
Explain the importance of sexual reproduction in evolution
Define stimulus
Define irritability
Define response
Define tactic and tropic responses
List down tactic responses in plants
List down tropic responses in plants
Differentiate between tactic and tropic responses
Define geotropism
Describe geotropism in roots and shoots of plants
Differentiate between Phototropism and geotropism
Carry out experiments demonstrating both Phototropism and geotropism in a plant seedling
Carry out experiments to demonstrate tactic responses to light and water
Carry out experiments to show chemotactic response using fruit juice
Define Hydrotropism and thigmotropism
State the importance of Tactic and tropic responses
Explain the production of Plant hormones and their effects on plants
Carry out experiment to investigate hydrotropism
Carry out experiment to investigate etiolation
Demonstrate the knee jerk in a reflex action
Defined Conditioned reflex actions
Describe Conditioned reflex action using parlous dog
Compare simple and conditioned reflex actions
Explain the role of endocrine system in a human being
Explain the effect over secretion and under secretion of thyroxin and adrenaline
Isolate and list the similarities and differences between the endocrine and the nervous system
State the effects of drug abuse on human health
Draw and label the mammalian eye
State the functions of the mammalian eye
Describe how the structure of the mammalian eye is adapted to its functions
Dissect and display parts of the mammalian eye
Describe how an image is formed and interpreted in the mammalian eye
Describe Accommodation in the mammalian eye
Name and explain the Common eye defects
Describe Common eye defects and their corrections
Investigate the blind spot In the eye
Investigate which eye is used more during vision
Name and describe Common eye diseases
Draw and label the mammalian ear
Describe the mammalian ear and how it is adapted to its functions
Describe the mechanism of hearing
Discuss thick ear drum, damaged cochlea, raptured eardrum, fussed ossicles, otitis media, ostosceleross and tinnitus
Define support and movement
Describe the necessity of movement in plants and animals
Review the tissue distribution in monocotyledonous an dicotyledonous plants
Describe support in woody and non-woody stems
Describe the role of tendrils and tender stems in support
Observe prepared sections of woody and herbaceous stems
Observe a wilting plant
List the types of skeletons
Describe the role of exoskeleton in insects
Describe the role and components of endoskeleton
Describe the role of skeleton in vertebrates
Draw the structure of a finned fish (tilapia)
Calculate the tail power
Explain how locomotion occurs in fish
Name and draw the different fins and state their functions
Draw the human skeleton and identify the component parts
Identify and draw the skull
Identify bones of Axial skeleton in the vertebral column
Identify the cervical vertebrae
Identify the structures of the thoracic vertebrae
Relate the structure of the thoracic vertebrae to their functions
Identify the structures of lumbar, sacral and candal vertebrae
Show how ribs articulate with thoracic vertebrae
Draw and label Ribs and sternum
Relate the structure to their functions
Identify components of Appendicular skeleton
Draw the scapula bone and relate it to its functions
Identify the bones of the fore limbs
Draw the structure of the humerus, radius and ulna
Draw and label bones of the hand
Draw the pelvic girdle
Name the bones of The pelvic girdle
Relate the structure to their functions
Identify, draw and label the femur, tibia and tibula bones
Relate their structure to their functions
Draw and label the bones of the foot
Relate the structure of bones of the foot to their functions
Define a joint
List the three types of joints
Describe the types of joints
List examples of movable joints, hinge joints and bell and socket joints
Define Immovable joints
Name Immovable joints
Define muscles
Explain the differences between the three types of muscles
Identifying biceps and triceps in the arm movement
Genetics
Introduction
Genetics is the study of inheritance. The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring. Factors that determine characters (genes) are passed on from parent to offspring through gametes or sex cells. In fertilisation the nucleus of the male gamete fuses with the nucleus of the female gamete.


The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring. Factors that determine characters (genes) are passed on from parent to offspring through gametes or sex cells. In fertilisation the nucleus of the male gamete fuses with the nucleus of the female gamete. The offspring show the characteristics of both the male and the female. Genetics is the study of how this heritable material operates in individuals and their offspring. Variations within Plant and Animal Species
Variation
The term variation means to differ from a standard. Genetics also deals with the study of differences between organisms belonging to one species. Organisms belonging to higher taxonomic groups e.g. phyla or classes are clearly different. Although organisms belonging to the same species are similar, they show a number of differences or variations such that no two organisms are exactly the same in every respect. Even identical twins, though similar in many aspects, are seen to differ if they grow in different environments. Their differences are as a result of the environment which modifies the expression of their genetic make-up or genotype. The two causes of variations are the genes and the environment. Genes determine the character while the environment modifies the expression of that character. Continuous and Discontinuous Variation
Continuous Variations
The differences between the individual are not clear-cut. There are intermediates or gradations between any two extremes. Continuous variations are due to action of many genes e.g. skin complexion in humans. In continuous variation, the environment has a modifying effect in that it may enhance or suppress the expressions of the genes. Continuous variation can be represented in form of a histogram. Example of continuous variation in humans is weight, height and skin complexion. Linear measurements:
In humans, height shows gradation from tall, to tallest. So does the length of mature leaves of a plant. In most cases, continuous variation is as a result of the environment. Discontinuous Variations
These are distinct and clear cut differences within a species. Examples include:
Ability to roll the tongue. An individual can either roll the tongue or not. Ability to taste phenylthiourea (PTC); some individuals can taste this chemical others cannot. Blood groups - and individual has one of the four blood groups A, B AB or O. There are no intermediates. Albinism - one is either an albino or not. Discontinuous variations is determined by the action of a single gene present in an individual.


There are no intermediates. Albinism - one is either an albino or not. Discontinuous variations is determined by the action of a single gene present in an individual. Structure and Properties of Chromosomes
These are threadlike structures found in the nucleus. They are normally very thin and coiled and are not easily visible unless the cell is dividing. When a cell is about to divide, the chromosomes uncoil and thicken. Their structure, number and behaviour is clearly observed during the process of cell division. The number of chromosomes is the same in all the body cells of an organism. In the body cells, the chromosomes are found in pairs. Each pair is made up of two identical chromosomes that make up a homologous pair. However sex chromosomes in human male are an exception in that the Y-chromosome is smaller. Number of Chromosomes
Diploid Number (2n)
This is the number of chromosomes found in somatic cells. For example, in human 2n = 46 or 22 pairs (44 chromosomes) are known as autosomes (body chromosomes")
while 1 pair is known as the sex chromosomes. In Drosophila melanogaster, 2n = 8. Chromosome Structure
All chromosomes are not of the same size or shape. In human beings; each of the twenty three pairs have unique size and structure . On this basis they have been numbered 1 to 23. The sex chromosomes formthe 23rd pair. Properties of Chromosomes
Chromosomes are very long and thin. They are greatly and loosely coiled and fit within the nucleus. During cell division they shorten, become thicker and are easily observable. Each consists of two chromatids. The two chromatids are held at same position along the length, at the centromere. Chromatids separate during cell division in mitosis and in the second stage of meiosis. Chromosomes take most dyes and stain darker than any other part of the cell. This property has earned them the name "chromatin material"
Each chromosome is made up of the following components:
Deoxyribonucleic acid (DNA) - this carries the genes. It is the major component of the genetic material. Protein e.g. histones. Ribonucleic acid (RNA) is present in very small amounts. Enzymes concerned with DNA and RNA replication - these are DNA and RNA polymerases and ligases.


histones. Ribonucleic acid (RNA) is present in very small amounts. Enzymes concerned with DNA and RNA replication - these are DNA and RNA polymerases and ligases. Structure of DNA
The structure of DNA was first explained in 1953 by Watson and Crick. DNA was shown to be a double helix that coils around itself. The two strands are parallel and the distance between the two is constant. Components of DNA
DNA is made up of repeating units called nucleotides. Each nucleotide is composed of:
A five-carbon sugar (deoxyribose). Phosphate molecule. Nitrogenous base, four types are available i.e,
Adenine - (A)
Guanine - (G)
Cytosine - (C)
Thymine - (T)
The bases are represented by their initials as A, G, C and T respectively. The sugar alternates with the phosphate, and the two form the backbone of the strands. The bases combine in a specific manner, such that Adenine pairs with Thymine and Guanine pairs with Cytosine. The bases are held together by hydrogen bonds. A gene is the basic unit of inheritance consisting of a number of bases in linear sequence on the DNA. Genes exert their effect through protein synthesis. The sequence of bases that make up a gene determine the arrangement of amino acids to make a particular protein. The proteins manufactured are used to make cellular structures as well as hormones and enzymes. The types of proteins an organism manufactures determines its characteristics. For example, albinism is due to failure of the cells of an organism to synthesise the enzyme tyrosine required for the formation of the pigment melanin. First Law of Heredity
It is also known as Law of Segregation (Mendel's First Law). The characters of an organism are controlled by genes occurring in pairs known as Alleles. By definition, an allele is an alternative form of a gene controlling a particular characteristic. Of a pair of such alleles, only one is carried in each gamete. This is explained by first meiotic anaphase stage, when the homologous chromosomes are separated so that each carries one of the allelic genes. Monohybrid Inheritance
This is the study of the inheritance of one character trait that is represented by a pair of genes on homologous chromosomes. Gregor Mendel (an Austrian monk) was the first person to show the nature of inheritance.


This is explained by first meiotic anaphase stage, when the homologous chromosomes are separated so that each carries one of the allelic genes. Monohybrid Inheritance
This is the study of the inheritance of one character trait that is represented by a pair of genes on homologous chromosomes. Gregor Mendel (an Austrian monk) was the first person to show the nature of inheritance. He did this through a series of experiments using the garden pea, Pisum sativum. As opposed to others before him, the success in his work lay in the fact that:
He chose to study first a single character at a time (monohybrid inheritance). He then proceeded to study two characters at time (dihybrid inheritance) . He quantified his results by counting the number of offspring bearing each trait. Each character he chose was expressed in two clearly contrasting forms. Examples
Stem length: some plants were tall while others were short. Colour of unripe pods: some were green, others yellow. There were no intermediates. Mendel's Procedure
For each character, Mendel chose a plant that bred true. A true or pure breed continues to show a particular trait in all the offspring in several successive generations of self-fertilisation. He made one plant to act as the female by removing the stamens before the ovary was mature and protecting (e.g. by wrapping with paper). The female plant from contact with any stray pollen. When the ovary was mature, he carefully dusted pollen from the anthers of the selected male plant and transferred it to the stigma of the female plant. Observations were then made on the resulting seeds or on the plants obtained when those seeds were planted. Results
For each pair of contrasting characters he studied, Mendel obtained the same results. For example, when he crossed pure breeding tall plants with pure breeding short plants, the first offspring, known as the first filial generation (FI) were all tall. When these were selfed i.e. self-fertilisation allowed to take place, the second generation offspring also know as the second filial generation or F2 occurred in the ratio of 3 tall: 1 short. The same ratio was obtained for each of the other characters studied. From this it is clear that one character i.e. tall is dominant over the short character. A dominant character is that which is expressed alone in the offspring even when the opposite character is represented in the genotype.


From this it is clear that one character i.e. tall is dominant over the short character. A dominant character is that which is expressed alone in the offspring even when the opposite character is represented in the genotype. The unexpressed character is said to be recessive. From these results and others obtained when he studied two characters at the same time, Mendel concluded that gametes carry factors that are expressed in the offspring. These factors are what we know today as genes. Mendel put forward the following laws of inheritance:
Of a pair of contrasting characters, only one can be represented in a gamete. For two or more pairs of such contrasting characters, each factor (gene) in the gamete acts independently of the others and may combine randomly with either of the factors of another pair during fertilisation. Genetic experiments carried out to date confirm Mendel's Laws of inheritance e.g. T.H. Morgan's work on inheritance in the fruit fly Drosophila melanogaster. Terms used in Genetics
Genotype:
The genes present in an individual. The genetic constitution of an individual. It is expressed in alphabetical notation.e.g TT,Tt
Phenotype:
The observed character or appearance i.e. the expression of the genes in the structure and physiology of the organism. In some cases the phenotype is the product of the genotype and the environment. Phenotype is expressed in words.eg TALL,SHORT,RED WHITE .etc. Alleles:
These are alternative forms of the same gene that control a pair of contrasting characters e.g. tall and short. They are found at the same position or gene-locus on each chromosome in a homologous pair. Homozygous:
This is a state where the alleles in an individual are similar e.g. TT (for tall)
Heterozygous:
This is a state where the alleles are dissimilar i.e. each of the two genes responsible for a pair of contrasting characters are present
e.g. Tt. (T for tall; t for short)
Hybrid:
This is the offspring resulting from crossing of two individuals with contrasting characters. Hybrid vigour or Heterosis:
The hybrid develops the best characteristics from both parents
i.e. it is stronger or healthier, or yields more than either parent. Use of Symbols
To represent genes in the chromosomes, letters are used. It is customary to use a capital letter for the dominant characteristic and small letter for the recessive one.


it is stronger or healthier, or yields more than either parent. Use of Symbols
To represent genes in the chromosomes, letters are used. It is customary to use a capital letter for the dominant characteristic and small letter for the recessive one. The gametes are encircled. For example,a cross between a tall and a short pea plant is illustrated as follows;
Let –T- represent gene for tallness. Let -t- represent gene for shortness. Fertilization-using checker board or Punnet square
F1 genotype Tt
F1 Phenotypic ratio =All tall. F2 Genotype TT,2Tt,tt
F2 Phenotypic ratio;3 Tall;1 short
Test Cross or Back Cross
This is a eras made between the F 1 bearing the dominant trait with the homozygous recessive parent. It is called a back cross because of using the first parent. It is also a test cross because it tests the genotype of the individual. Complete Dominance
Mendel happened to choose characters that showed complete dominance,
i.e. the dominant trait completely masked the recessive one in the F1 generation. In man, certain characters are inherited in the same way
e.g. colour of the skin; normal colour is dominant to albinism (lack of skin pigment). The children are all normal but have the gene for albinism. Such individuals are referred to as carriers. Other characters that show complete dominance in humans are:
Ability to roll the tongue. Polydactyly (having more than 5 digits in one limb). Brachydactyly - having short fingers. Achondroplasia - dwarf with bow legs. Incomplete Dominance
In this kind of inheritance there is no dominant or recessive gene but the two are expressed equally in the offspring,
Resulting in blending of the characters. The gene for red colour (R) in cattle and the gene for white colour(W) show incomplete dominance or co-dominance. The offspring are neither red nor write but are intermediate between the two. They are said to be roan. In humans, the sickle cell gene and the normal gene are co-dominant. Inheritance of ABO blood groups in humans
Blood groups in human are determined by three alleles, A, B, and O. An individual can have only two of these genes. Genes A and Bare codominant, while gene 0 is recessive to A and B.


Inheritance of ABO blood groups in humans
Blood groups in human are determined by three alleles, A, B, and O. An individual can have only two of these genes. Genes A and Bare codominant, while gene 0 is recessive to A and B. These are referred to as multiple alleles. The ABO Blood Group System
Rhesus Factor
The Rhesus factor is responsible for the presence of a protein (Antigen D) in the red blood cells. If blood from a Rhesus positive (Rh+) person is transferred into a person without the Rhesus factor (Rh-);
The recipients' body produces antibodies against the Rhesus factor. This causes agglutination of red blood cells which can be fatal if subsequent transfusion with Rh+ blood is done. Sex Determination in Humans
XY type e.g. human male
In males, two types of sperms are produced. Half of then containing X chromosomes and half Y chromosomes. During fertilisation only one sperm fuses with the egg. If it is an X-carrying sperm then a female zygote is formed;
If it is a Y-carrying sperm then a male zygote is formed. It follows then that the chances of getting a boy or girl are half or fifty-fifty. Note also that it is essentially the type of sperm that fertilises the egg that determines the sex. Linkage
The term linkage describe the situation where genes or certain characters are located on the same chromosome. Offspring produced by sexual reproduction show only the parental characteristics and only sometimes few new recombinants. i.e. offspring with combinations of characteristics not found in either of the parents due to crossing over in first prophase of meiosis. Genes are said to be linked when they are located close together on the same chromosome such that they are always inherited together. Sex linked genes
These are genes that are located on the sex chromosomes. Sex-linkage - refers to carrying of the genes on the sex-chromosome. Gene for a trait may be present, yet offspring does not show the trait. This happens in human females (XX) where a gene for the trait is recessive. The female acts as a carrier. In human, sex linked characters found on the X chromosome include:
Haemophilia:
This is a disease that affects the rate of clotting of blood, leading to excessive bleeding even from a minor cut. Haemophilia is more common in males than in females.


The female acts as a carrier. In human, sex linked characters found on the X chromosome include:
Haemophilia:
This is a disease that affects the rate of clotting of blood, leading to excessive bleeding even from a minor cut. Haemophilia is more common in males than in females. A female my have the gene for haemophilia and not show the trait because the normal gene is dominant over the gene for haemophilia. Such females are referred to as carriers. If the carrier female offspring will be carriers while the other half will be normal. Half the males will be normal and the other heamophilic. Red-green colour-blindness
Red-green colour-blindness is caused by a recessive gene found on the X chromosome. It is inherited in the same way as haemophilia. More males 1:10,000, less female 1: 100 million afflicted. It is the inability to distinguish between red and green colours in humans. Genes found on y-chromosome include:
Hairy pinna and hairy nose are carried on the Y - chromosome. Premature balding. Mutations
Mutations are sudden changes in the genotype that are inherited. Mutations are rare in nature and mutated genes are usually recessive to the normal (wild type) genes. Most mutations are generally harmful and some are lethal. A somatic mutation is a genetic change in somatic cells. Somatic mutations are only inherited if asexual reproduction takes place e.g. as in plants and unicellular animals. A gene mutation is a change in genes of reproductive cells and is always inherited. The resultant individual is called a mutant. The mutant has different characteristics from the rest of the population. Types of Mutations
Chromosomal mutations - are changes in number or structure of chromosomes. Gene mutations - also called point mutations - are changes in the chemical nature of the gene. Mutagens:
These are agents that cause mutations. The include ultra-violet light, Gamma rays., x-rays and cosmic rays. Certain chemicals e.g. mustard gas and colchicines also induce mutations. Causes and consequences of chromosomal mutations
There are three main types of chromosomal mutations. Changes in the diploid number of chromosomes (allopolyploidy). The diploid number changes to 3n (triploid) or 4n (tetraploid) and so on. This results from the doubling of the chromosome number in the gamete (2n).


Changes in the diploid number of chromosomes (allopolyploidy). The diploid number changes to 3n (triploid) or 4n (tetraploid) and so on. This results from the doubling of the chromosome number in the gamete (2n). This is due to failure of the chromosome sets to separate during meiosis. The phenomenon is known as polyploidy. It is common in plant's and has been employed artificially to produce varieties of crops with hybrid vigour e.g. bread wheat is hexaploid (6n). This is allopolyploidy). Change in the total number of chromosomes involving the addition or loss of individual chromosomes (autopolyploidy). This is due to failure of individual chromosomes to separate during meiosis. One gamete gains an extra chromosome while the other loses a chromosome. The term non-disjunction is used to describe the failure of chromosomes to separate. Non-disjunction results in several disorders in humans:
Down's syndrome
The individual has 47 chromosomes due to non-disjunction of chromosome 21. It is also known as trisomy 21. The individual has slanted eyes with flat and rounded face, mental retardation and large tongue and weak muscles. Turner's Syndrome
This brings about to a sterile and abnormally short female. It is due to loss of one of the sex chromosomes
i.e. the individual has one X chromosome (44 + X) instead of two (44 + XX). Klinefelter's Syndrome
This results in a sterile male who may be mentally retarded. It is due to an additional X chromosome
i.e. the individual i.e. 47 chromosomes (44 + XXY) instead of 46 (44 + XY). Changes in the structure of a chromosome during meiosis. A portion of a chromosome may break off and fail to unite again or it may be joined in the wrong way or to the wrong chromosome. These mutations are described as follows:
Deletion:
This is the loss of a portion of a chromosome,
Deletion results in individuals born with missing body parts . e.g. limbs in the extreme of cases. Inversion:
A portion may break from a chromosome and then rejoin to it after turning though an angle-of 1800 . Translocation:
This is when a portion is joined to a non-homologous chromosome. Duplication:
A certain section of an intact chromosome replicates such that the genes are repeated.


Inversion:
A portion may break from a chromosome and then rejoin to it after turning though an angle-of 1800 . Translocation:
This is when a portion is joined to a non-homologous chromosome. Duplication:
A certain section of an intact chromosome replicates such that the genes are repeated. Gene Mutations
A gene mutation is a change in the structure of a gene. It may involve only a change in one base, e.g. adenine in place of thyamine yet the effect on the individual is profound e.g. sickle cell anemia . There are two main type of gene mutations:
Due to insertion or deletion of one or more (base) pairs. Substitution of base pairs e.g. purine for pyrimidine. Genetically inherited disorders in humans
Albinism is a mutation that alters the gene responsible for synthesis of skin pigment (melanin). The gene for albinism is recessive. Sickle cell anemia is a common condition in Kenya. Individuals with the sickle-cell gene produce abnormal haemoglobin. It is due to gene mutation caused by substitution of the base adenine for thymine. The result is the inclusion of the amino acid valine (in place of glutamic acid) in the haemoglobin synthesised. As a result the red blood cells become sickle shaped when oxygen concentration becomes low i.e. inside tissues. This leads to blockage of capillaries. Tissues do not get sufficient oxygen. Homozygous individuals are seriously anaemic and die in early childhood. Heterozygous individuals have a mixed population of normal and sickled red blood cells. They are not seriously anaemic and can lead fairly normal lives. Haemophila (bleeder's diseases) is due to lack of gene for production of proteins responsible for blood clotting. Practical Applications of Genetics
Study of genetics has been put into a wide variety of uses en-compasing plants and animals and in particular humans. Blood transfusion
Blood groups are genetically determined. As discussed earlier a person of blood group A can only get blood from another one of A or O. In case of emergencies and unavailability of blood, a patient may be given blood group A + when he/she is A-. First transfusion is fine since, by the time enough antibodies are produced most of the red blood cells of donor have completed their lifespan but a subsequent transfusion of A+ blood is fatal.


As discussed earlier a person of blood group A can only get blood from another one of A or O. In case of emergencies and unavailability of blood, a patient may be given blood group A + when he/she is A-. First transfusion is fine since, by the time enough antibodies are produced most of the red blood cells of donor have completed their lifespan but a subsequent transfusion of A+ blood is fatal. Plant and Animal breeding
Genetics is applied mostly in plant and animal breeding in order to produce varieties that are most suitable to man's needs. This is done through artificial selection. Varieties are developed that are resistant to pests, diseases or harsh climatic conditions. Genetic counselling
Genetic counselling involves advising about hereditary diseases and disorders so that they can make informed decisions. This is done through:
Taking family history. Screening for genotypes e.g. through amniocentesis. In amniocentesis, cells are obtained from amniotic fluid during pregnancy. Conditions such as Down's syndrome can be detected using microscopy. Genetic Engineering
This is a technology that involves the manipulation of the genotype of an organism to get the desired trait. It also involves the transfer of gene coding for the desired trait from one organism to another. Application of Genetic Engineering
Pharmaceutical industries:
Making of hormones e.g. Human insulin and human growth hormone. Enzymes e.g. Alph-Anti-Trypsin (AAT) used to treat emphysema. (c) Proteins. Drugs and vaccines. Agricultural industries:
Transgenic animals and plants are produced which are also called Genetically Modified Organisms (GMO's). A variety of tomato with improved paste and a longer shell life. Sheep for producing desired proteins in milk. Plants resistant to pests and diseases. Cloning
This is the making of identical copies of genes, DNA and whole organisms. Cloning is used in plants - that is tissue culture e.g. in development of various varieties of bananas and Eucalyptus trees. The first mammal to be cloned successfully was Dolly - the sheep. A nucleus from the cell obtained from the udder of the sheep was inserted in an unfertilised egg without a nucleus. This zygote was introduced into the uterus of a sheep and developed to full term. Gene therapy
Involves injecting genes into patients of certain diseases
e.g. Parkinson's diseases.


This zygote was introduced into the uterus of a sheep and developed to full term. Gene therapy
Involves injecting genes into patients of certain diseases
e.g. Parkinson's diseases. The injected gene alters metabolism to bring about the cure of the disease. Practical Activities
To demonstrate Continuous variations
Height of students
Students should work in pairs, use chalk and metre rule to mark level of top of head onto the wall
Or door as one student stands straight without shoes, next to the wall or door. The height for each student is recorded on chalk board. The frequency distribution of height is recording as the height is grouped into various classes. A histogram to represent frequency against height is drawn. The normal bell shaped curve is observed. Discontinuous variations - ability to roll tongue
The number of students who can roll their tongue is recorded as well as the number of non-tongue rollers. The ratio of tongue-rollers to non tonguerollers is worked out. Gene for the ability to roll the tongue is dominant, therefore is expected more tongue rollers. Demonstration of Mitosis and Meisosis
Mitosis
Plasticene is used to represent number and shapes of various chromosomes e.g. 8 in Drosophila melanogaster. Each stage of mitosis illustrated e.g. interphase,
Each is rolled to appear long is and coiled, prophase is each made into a ball and then shaped to the appropriate length; and split into two to represent chromatids. Centromeres for different chromosomes can be illustrated in different positions. Each stage of mitosis is illustrated and telophase can be illustrated by surrounding the "chromosomes" with a long many drawn plasticene to represent cell membrane. It is manipulated to show how telophase takes place. Meiosis
The same procedure is followed. Plasticine with contrasting colours is used to show clearly gene mixing in crossing over. Each pair of homologous chromosomes is represented by plasticene with two different colours e.g. red (paternal) blue for maternal chromosome. All the steps in the two stages of meiosis are illustrated up to the production of four haploid gametes. Human Finger Prints
The finger prints for each student's thumb, forefinger and middle fingers of the left hand is imprinted on a white paper. A rubber stamp with ink is used to and each finger -tip phalange is rolled onto the inkpad. For best results students work in pairs.


Human Finger Prints
The finger prints for each student's thumb, forefinger and middle fingers of the left hand is imprinted on a white paper. A rubber stamp with ink is used to and each finger -tip phalange is rolled onto the inkpad. For best results students work in pairs. Observations are made at all forefingers, thumb prints and differences noted. The main patterns are noted. It is also noted that no two, fingerprints are exactly similar. end
EVOLUTION
Meaning of Evolution and Current Concepts
Evolution is the development of organisms from pre-existing simple organisms over a long period of time. It is based on the similarities in structure and function that is observed in all organisms. All are made up of cells, and similar chemical compounds are present. This indicates that all organism may have had a common origin. Evolution seeks to explain the diversity of life and also to answer the question as to the origin of life, as well as its present state. The Origin of Life
Human beings have tried to explain how life began. Currently held views are listed below:
Special creation -life was created by a supernatural being within a particular time. Spontaneous generation life originated from non-living matter all at once. e.g. maggots arise from decaying meat. Steady state - life has no origin. Cosmozoan - life on earth originate from elsewhere, outer space. Bio-chemical evolution-life originated according to chemical and physical laws. Only special creation and chemical evolution will be discussed. Special Creation
The earliest idea is that of special creation which is recorded in the old testament (Genesis 1: 1-26). It states that God created the world and all living things in six days. Some hold the six days literally, while others say it may represent thousands of years. According to his theory, the earth and all organisms were created mature. Similarities in structure and function denote the stamp of a "common Designer"
Evidence for this view arises from observations of life itself. Faith explains it all. By faith we understand that the universe was created by the command of God. Several scientists hold this view and their research confirms accounts in the old testament of a universal flood explains the disappearance of dinosaurs as vegetation decreased.


Faith explains it all. By faith we understand that the universe was created by the command of God. Several scientists hold this view and their research confirms accounts in the old testament of a universal flood explains the disappearance of dinosaurs as vegetation decreased. Chemical Evolution
The following is the line of thought held in this view to explain origin of life:
The composition of atmospheric gases was different from what it is today:
There was less oxygen, more carbon (IV) oxide, hence no ozone layers to filter the ultra-violet light. The high solar energy reached the earth and brought together hydrogen, carbon (IV) oxide and nitrogen to make organic compounds. These were: hydrocarbons, amino acids, nucleic acids, sugars, amino acids and proteins. The proteins coalesced and formed colloids. Proteins and lipids formed a "cell membrane" that enclosed the organic compounds, to form a primitive cell. The cell was surrounded by organic molecules that it fed on
heterotrophically. This took place in water. From this cell progressively autotrophs evolved. That were similar to blue-green algae. They produced oxygen and as more oxygen was evolved ozone layer formed an blocked ultra violet radiation. This allowed formation of present day photo-autotrophs. Evidence for Organic Evolution
Most of the evidence for evolution is indirect . i.e. it is based on studies carried out on present-day animals and plants. Direct evidence is obtained from studying the remains of animals and plants of the past. Fossil Records
The study of fossils is called paleontology. Fossils are remains of organisms that lived in ancient times. Most fossils are remains of hard parts of the body such as bones, teeth, shells and exoskeletons. Some fossils are just impressions of the body parts, e.g. footprints, leaf-vennation patterns, etc. Fossils are usually found in sedimentary rocks which have been formed by deposition of sediments over millions of years. The deeper the layer of sediments, the older the fossils found in that layer. Modem man, Homo sapiens, evolved from ape-like creatures 25 million years ago. These evolved to upright, tool using creature called Australopithecus afarensis which had a cranial capacity of 400-500 cc. This evolved through several intermediates; Homo habilis and Homo erectus to modem day human. Homo sapiens has a cranial capacity of 1350 - 1450 cc.


These evolved to upright, tool using creature called Australopithecus afarensis which had a cranial capacity of 400-500 cc. This evolved through several intermediates; Homo habilis and Homo erectus to modem day human. Homo sapiens has a cranial capacity of 1350 - 1450 cc. Homo sapiens is more intelligent. Main features in human evolution include bipedal posture, is an omnivore and has an opposable thumb. Limitations of the Fossil Evidence
Only partial preservation was usually possible because softer parts decayed. The fossil records are therefore incomplete. Distortion - parts of organisms might have become flattened during sedimentation. Subsequent geological activities e.g. erosion, earthquakes, faulting and uplifting may have destroyed some fossils. Geographical Distribution
Until about 250 million years ago, all the land masses on earth formed a single land mass (Pangaea). This is thought to have undergone continental drift, splitting into different continents. Consequently, organisms in certain regions became geographically isolated and did not have a chance to interbreed with other organisms in other regions. Such organisms underwent evolution in isolation and have become characteristically different from organisms in other regions. For example, pouched mammals (e.g. kangaroo, wallaby, koala bear) are found almost exclusively in Australia. The opossum is the only surviving representative of the pouched mammals in North America. Comparative Embryology
During the early stages of development, the embryos of different vertebrates are almost indistinguishable. Fish, amphibian, bird and mammalian embryos have similar, features, indicating that they arose from a common ancestor. Similarities include:
Visceral clefts, segmental muscle blocks (myotomes) and a single circulation. Comparative Anatomy
Comparative anatomy is the study of organs in different species with the aim of establishing whether the organism are related. Organisms which have the same basic features are thought to have arisen from a common ancestor. The vertebrate pentadactyl limb evolved in different ways as an adaptation to different modes of life. e.g. as a flipper in whales, as a wing in bats and as a digging hand in moles. Such organs are said to be homologous, i.e. they have arisen from a common ancestor but they have assumed different functions. This is an example of divergent evolution . The wing of a butterfly and that of a bird are said to be analogous.


they have arisen from a common ancestor but they have assumed different functions. This is an example of divergent evolution . The wing of a butterfly and that of a bird are said to be analogous. i.e. they have originated from different ancestors but they perform the same function. This is an example of convergent evolution. Cell Biology
All eucaryotic cells have organelles such as mitochondria, membrane-bound nuclei, ribosomes, golgi bodies. Thus indicating that different organisms have a common ancestor. The presence of chloroplasts and cellulose cell walls indicates that green plants have a common ancestor. Blood pigments are conjugated proteins with a metal group. Similar pigments are found in different animal groups . e.g. haemoglobin is found in all vertebrates and in annelida (earthworm). This shows that all animals have a common origin. Mechanism of Evolution
The mechanism of evolution can be described as a process of natural selection acting on the heritable variations that occur among the members of a population. A population consists of a group of individuals of the same species. Each individual has a set of hereditary factors(genes). All the genes in a population constitute a gene pool. When reproduction takes place, genes pair with one another randomly. Genes which occur in great numbers in the gene pool, will occur in greater numbers in the next generation. Several theories have been proposed over the years to explain how evolution took place. Lamark’s theory
Lamark had observed that if a part of the body of an organism was used extensively, it became enlarged and more efficient;
If a part of the body was not fully used, it would degenerate. By use and disuse of various body parts, the organism would change and acquire certain characteristics. He suggested that these characteristics would them be passed on to the offspring(next generation). In 1809, lamark published his book ‘’Theory Of Evolution’’. He proposed that new life forms arise from use and disuse of parts of existing organisms and through the inheritance of acquired characteristics. Lamark’s theory has been disapproped in that although use and disuse of parts does lead to acquired characteristics, such characteristics are not inheritable since they are effects produced by the environment and not by genes. Evolution by natural selection
In 1859, charles Darwin published his theory of evolution’ in a book called origin of species by means of natural selection’.


He proposed that new life forms arise from use and disuse of parts of existing organisms and through the inheritance of acquired characteristics. Lamark’s theory has been disapproped in that although use and disuse of parts does lead to acquired characteristics, such characteristics are not inheritable since they are effects produced by the environment and not by genes. Evolution by natural selection
In 1859, charles Darwin published his theory of evolution’ in a book called origin of species by means of natural selection’. Darwin’s theory was based on the following evidence;the population of a given species remains constant over a long period of time. The number of young ones is more than the number of adults. More offsprings are produced than can possibly survive. Variation occurs withing a given population,i.e all members of the same species are not alike. On the basis of these observations. Darwin made the following conclusions;
There is a struggle for existence among individuals in a given population. Individuals who are not suitably adapted (e.i. who have unfavourable variations)are less able to pass their characteristics to the next generation. Natural selection operates on the population, selecting those individuals with favourable variations;
i.e. environment favours individuals that are more adapted. They win competition e.g. for food and survive.i.e. ‘’survival of the fittest’’. They attain sexual maturity and pass on the characteristics to their offsprings. Natural selection
Peppered moth (Industrial melanism)
The peppered moth, Biston betularia, exists in two distinct forms;
A speckled white form(the normal form) and the melanic, dark form. The moths normally rest on the tree trunks and branches wherre they are camouflaged against predators. The first melanic moths were observed in 1848 around Manchester in Britain. Since that time, their numbers has increased tremendously, out-numbering the speckled white form. The increase in the population of the melanic form is correlated with environmental changes brought about by industrialization and pollution. Smoke and soot from factories have darkened the tree trunks over the years. This has resulted in the preservation of the mutation in Biston betularia leading to the evolution of the melanic form. This form is almost invisible against the dark background of the tree trunks and is less subject to predation than the speckled form.


Smoke and soot from factories have darkened the tree trunks over the years. This has resulted in the preservation of the mutation in Biston betularia leading to the evolution of the melanic form. This form is almost invisible against the dark background of the tree trunks and is less subject to predation than the speckled form. The peppered form is more abundant in areas away from the soot and smoke of factories. This is because it is well camouflaged by the lichen-covered tree trunks against which it rests and is therefore not easily detected by predators. The existence of two or more distinct forms within a species (as exemplified by Biston betularia) is called polymorphism. Resistance to Drugs
Certain strains of organisms have developed resistance to drugs and antibiotics. Following continued use of such drugs and antibiotics, some of the individuals in a population of bacteria or other microorganisms survive and are able to pass their characteristics to the next generation. When a patient fails to take full dosage of the antibiotics prescribed the pathogen develops resistance to the drugs hence become difficult to control. Some mosquitoes have developed resistance to certain pesticides. Practical Activities
Comparison of Vertebrate Limbs
Limbs of various vertebrates are provided:
e.g. fish- Tilapia, amphibian-frog reptiles, lizard; bird - domestic fowl (chicken), mammal- rabbit. Their anatomy can be studied. The following can be noted:
That all limbs have five sets of bones;
A single upper bone- the femur in hind limb and the humerus in fore limb
Two lower limb bones -i.e. the tibia & fibula in the hind limb & ulna & radius in the forelimb. Small bones - i.e. ankle (tarsals) and wrist bones (carpals)
The bones making the foot and hand are metatarsals and metacarpals respectively. The bones of toes and of fingers i.e. phalanges
Observe the various modifications of these bones in the various animals. Limbs of different mammals e.g. rabbit, cow, donkey reveal that the anatomy is adapted to mode or type of movement . e.g. the horse has a single digit. An outdoor activity to observe various sty les of movement in different mammals can be studied. It is noted that some move on tips of toes (donkey) others on the whole leg (rabbit).


the horse has a single digit. An outdoor activity to observe various sty les of movement in different mammals can be studied. It is noted that some move on tips of toes (donkey) others on the whole leg (rabbit). Comparision of Wings of bird-and insect
Wings of birds and insects (grasshopper, butterfly or moth) are obtained. A hand lens or a dissecting microscope is used to observe the specimens. The differences in their anatomy is noted. Insect wings are membranous while those of birds are made up of feathers that interlock. Education tour to Archeological site/local Museum
Visits to the local museum yield important information that greatly supplement study of evolution. The National museum in Nairobi has many fossils. Visit to the various archeological sites that exist in Kenya is recommended. end
RECEPTION, RESPONSE AND CO-ORDINATION
IN PLANTS AND ANIMALS
Introduction
The structures involved in detecting the changes may be located far away from the ones that respond. There is need for a communication system within the body. The nervous system and the endocrine system perform this function,
i.e. linking the parts of the body that detect changes to those that respond to them. Irritability
Living organisms are capable of detecting changes in their internal and external environments and responding to these changes in appropriate ways. This characteristic is called irritability, and is of great survival value to the organism. Stimuli
A stimulus is a change in the internal or external environment to which an organism responds. Examples of stimuli include light, heat, sound, chemicals, pH, water, food, oxygen and other organisms. Response
A response is any change shown by an organism in reaction to a stimulus. The response involves movements of the whole or part of the body either towards the stimulus or away from it. It also results in secretion of substances e.g. hormones or enzymes by glands. Co-ordination
Co-ordination is the working together of all the parts of the body to bring about appropriate responses to change in the environment. Reception
Reception is the detection of changes in the environment through receptors. Irritability in Plants
Response in plants is not as pronounced as in animals. This does not in anyway diminish the importance of irritability in plants. It is as important to their survival as it is in animals. Plants respond to a variety of stimuli in their environment. These stimuli include light, moisture, gravity and chemicals.