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:08 PM 3/17/06 1:06:08 PM How do ionic bonds form? Recall that atoms do not have an electric charge. Also recall that an atom is most stable when its outer energy level is either empty or full. To become more stable, an atom might give up electrons to empty its outer energy level. Or, the atom might accept electrons to...
electric charge if the atom gives up an electron. 7. Identify the substances that are held together by van der Waals forces. (Circle your answer.) a. atoms b. molecules 58 Chapter 6 Chemistry in Biology. 055-068 GHSB RESG-874600.indd 58 055-068 GHSB RESG-874600.indd 58 3/17/06 1:06:12 PM 3/17/06 1:06:12 PM 6 section ●...
-874600.indd 59 3/17/06 1:06:14 PM 3/17/06 1:06:14 PM ■ ■ ■ Picture This 2. Label the subscripts and the coefﬁ cients in this equation after you read the discussion on this page. Take Notes Make a three-tab Foldable from a sheet of notebook paper. As you read, record what you learn about reactants, products, and the en...
the activation energy. For example, a candle will not burn until you light the wick. The ﬂ ame from a match provides the activation energy for the candle wick to react with oxygen in the air. Some reactions need higher activation energy than others 60 Chapter 6 Chemistry in Biology Reading Essentials 055-068 GHSB RESG...
and temperature affect enzyme activity. 3. Explain why the energy of the product might be lower than the energy of the reactants. Picture This 4. Label each of the three parts of this process with a brief description of what the part shows biologygmh.com Chapter 6 Chemistry in Biology 61 055-068 GHSB RESG-874600.indd ...
having two opposite poles, or ends. A magnet has polarity. When the opposite poles of a magnet are close to each other, they attract. In the same way, when oppositely charged regions of polar molecules are close together, they attract each other. In water, the attraction is called a hydrogen bond. A hydrogen bond is a...
easily in water. The human body is about 70 percent water and contains many solutions. When a substance containing hydrogen is dissolved in water, the substance might release a hydrogen ion (H+), as illustrated in the ﬁ gure below. Substances that release hydrogen ions when dissolved in water are called acids. The mor...
, notice that carbon has four electrons in its outer energy level. Recall that the second energy level can hold eight electrons. Therefore, a carbon atom can form four covalent bonds with other atoms. Carbon atoms can bond with each other, forming a variety of organic compounds. These organic compounds can take the for...
and hydrogen. Fats, oils, and waxes are all lipids. The main function of lipids is to store energy. A lipid called a triglyceride (tri GLIH suh rid) is a fat when solid and an oil when liquid. Plant leaves are coated with lipids called waxes to prevent water loss. Picture This 2. Draw Conclusions To what group of macr...
-068 GHSB RESG-874600.indd 67 055-068 GHSB RESG-874600.indd 67 3/17/06 1:06:37 PM 3/17/06 1:06:37 PM 6. Draw Conclusions What protein function listed here suggests that most enzymes are proteins? Picture This 7. Circle each nucleotide grouping in the nucleic acid on the right of the ﬁ gure. Protein Function Proteins ar...
7 section ● Cellular Structure and Function Cell Discovery and Theory 1 The microscope led to the discovery of cells. What You’ll Learn the principles of the cell theory how compound light microscopes differ from electron microscopes how prokaryotic and eukaryotic cells differ Focus As you read, underline or highlight...
listed in the table below. Picture This 2. Highlight the principle in the cell theory that resulted from the discoveries of Matthias Schleiden and Theodor Schwann. The Cell Theory Principle 1. All living organisms are made up of one or more cells. Explanation An organism can have one or many cells. Most plants and ani...
electron microscope (STM), can magnify living cells. Basic Cell Types Cells have different sizes, shapes, and functions, but all cells have a plasma membrane. A plasma membrane is a boundary that helps control what enters and leaves the cell. Some basic functions are common to most cells. For example, most cells have ...
you will learn about a cell structure that has the same basic function. On the lines below, list some things you think would be allowed to pass into a cell and some things that would be kept out. Make Flash Cards Make a ﬂ ash card for each question heading in this section. On the back of the ﬂ ash card, write the answ...
is also polar. The nonpolar tails, made of the fatty acids, are repelled by water. The phospholipid bilayer is arranged so that the polar heads can be closest to the water that is inside and outside the cell. Likewise, the nonpolar tails are farthest from the water because they are inside the phospholipid bilayer, as ...
identify chemical signals from the environment. For example, carbohydrates in the plasma membrane might help disease-ﬁ ghting cells identify and attack a potentially harmful cell. What is the ﬂ uid mosaic model? All the components of the plasma membrane are in constant motion. Phospholipids can move sideways within th...
keleton. Microtubules are long, hollow protein cylinders that form a ﬁ rm skeleton for the cell. They assist in moving substances within the cell. Microﬁ laments are thin protein threads that help give the cell shape and enable the entire cell or parts of the cell to move. Cell Structures All chemical processes of a ty...
. Which organelle produces proteins? Ribosomes produce proteins and are made of two components—RNA and protein. Ribosomes are produced in the nucleolus, a structure located inside the nucleus. Some ribosomes ﬂ oat freely in the cytoplasm. They produce proteins that will be used by other cells. Other ribosomes attach to...
12:47 PM What makes up a centriole? Centrioles are organelles made of microtubules that function during cell division. They usually are found near the nucleus of the cell. Plant cells do not contain centrioles. Which organelle produces energy? Cells need energy to survive. The organelles that convert fuel particles suc...
elles found in eukaryotic cells. Picture This 6. Highlight the organelle to which ribosomes attach. Cell Structure Function Cell wall Centriole protects and supports plant cells important in cell division Chloroplast site where photosynthesis occurs Cilia aids in moving the cell and moving substances along the surface ...
you read this section, write quiz questions based on what you have learned. After you write the questions, answer them. Record Information Make a three-pocket Foldable from an 11 17 sheet of paper. As you read, record information about cellular transport on quarter sheets of notebook paper and store them in the approp...
. Diffusion of water and facilitated diffusion of ions and small molecules occur without additional energy because the particles are already moving. When no energy is added, the transport is referred to as passive transport. Osmosis: Diffusion of Water Water passes in and out of the cell through the plasma membrane. Th...
loss of water in plant cells causes wilting. Active Transport Substances might need to move from an area of lower concentration to an area of higher concentration. Transport proteins help move substances across the plasma membrane against the normal ﬂ ow. This movement against the normal ﬂ ow requires energy and is ca...
can change form, but it cannot be created or destroyed. For example, your body changes the energy in food into chemical energy. Also, when you run, your body changes the energy into mechanical energy. The second law of thermodynamics states that systems change from states of order to states of disorder on their own. T...
the energy needs of cells. How is energy changed during photosynthesis? Photosynthesis is a series of reactions that change light energy from the Sun into chemical energy that can be used by the cell. During photosynthesis, light energy, carbon dioxide, and water are changed into organic molecules and oxygen. The ener...
section ● Cellular Energy Photosynthesis 2 Light energy is trapped and converted into chemical energy during photosynthesis. What You’ll Learn the two phases of photosynthesis how a chloroplast works during light reactions how electron transport works Before You Read Plants change energy from sunlight into energy that...
thylakoids are arranged in stacks called grana. The ﬂ uid-ﬁ lled space outside the grana is the stroma. Phase one takes place in the thylakoids. Phase two takes place in the stroma. What is the role of pigments in photosynthesis? Thylakoids contain light-absorbing colored molecules known as pigments. Different pigment...
, and oxygen as a waste product. The excited electrons move from photosystem II and move along a series of electron-carriers to photosystem I. Photosystem I absorbs more light, and the excited electrons move along electroncarriers again. Finally, the electrons are moved to NADP, forming the energy-storage molecule NADP...
grow in hot, dry environments. Many plants in extreme climates have evolved other photosynthesis pathways. Tropical plants such as sugar cane and corn use the C4 pathway. Instead of the 3-carbon molecules of the Calvin cycle, C4 plants ﬁ x carbon dioxide into 4-carbon molecules. Less water is lost in the C4 pathway. T...
O energy Cellular respiration begins with glycolysis, a process in which glucose is broken down into pyruvate. Glycolysis is an anaerobic process, meaning it does not need oxygen. Glycolysis is followed by aerobic processes, which require the presence of oxygen. During aerobic respiration, pyruvate is broken down and A...
a series of proteins. Electrons and protons are released from NADH and FADH2 into the mitochondria. Protons and electrons are transferred to oxygen to make water. Electron transport makes 24 ATP molecules. Overview of Cellular Respiration 1. Identify In the Krebs cycle, what is pyruvate converted to? Picture This 2. I...
known as alcohol fermentation. These organisms use pyruvate to make ethyl alcohol and carbon dioxide. Photosynthesis and Cellular Respiration Photosynthesis and cellular respiration are important ways that cells get and use energy. These processes are related in important ways. The products of photosynthesis—oxygen an...
area is now 24 µm2, and the volume is 8 µm3. The ratio of surface area to volume is 3:1. Notice that the ratio of the larger cell is lower than that of the smaller cell. Cells grow until they reach their size limit, then they either stop growing or divide. What You’ll Learn why cells are small the stages of the cell c...
the cell cycle varies depending on the type of cell. A typical animal cell takes 12–24 hours to complete the cell cycle. Some cells might complete the cycle in eight minutes. Other cells might take as long as a year to complete one cycle. Picture This 3. State Complete the table by writing the number of cells present ...
, cell division is complete, and the original cell has become two daughter cells How do prokaryotic cells divide? The cell cycle you have just learned about—interphase, mitosis, and cytokinesis—occurs in eukaryotic cells. As you have learned, prokaryotic cells are simpler cells. They reproduce by a method called binary...
Follow the diagram as you read about each stage 96 Chapter 9 Cellular Reproduction Reading Essentials 093-102 GHSB RESG-874600.indd 96 093-102 GHSB RESG-874600.indd 96 3/17/06 1:22:20 PM 3/17/06 1:22:20 PM ■ ■ What happens during prophase? The ﬁ rst and longest stage of mitosis is called prophase. Before prophase, DNA...
poles of the cell. One spindle ﬁ ber connects the centromere to one pole of the cell. The other spindle ﬁ ber connects the centromere to the opposite pole of the cell. This ensures that each new cell gets one copy of the DNA. How are the chromosomes arranged? During the second stage of mitosis, metaphase, the chromati...
a rigid cell wall. During cytokinesis, plant cells form a new structure, called the cell plate, between the two daughter nuclei. New cell walls then form on either side of the cell plate, dividing the cell into two identical daughter cells. How is cell division different in prokaryotic cells? Prokaryotic cells undergo...
cellular reproduction process. Proteins called cyclin bind to enzymes called cyclin-dependent kinases (CDKs) in the stages of interphase and mitosis to trigger the various activities that take place in the cell cycle, as shown below 100 Chapter 9 Cellular Reproduction Reading Essentials 093-102 GHSB RESG-874600.indd 1...
can help reduce the risk of cancer. Federal laws protect people from exposure to carcinogens in the workplace and in the food supply. People can reduce their risk of cancer by avoiding all tobacco (including secondhand smoke and smokeless tobacco) and by using sunscreen to protect their skin from ultraviolet radiation...
, organs, and organ systems. Stem-cell research could lead to the treatment of many human diseases and conditions. Embryonic stem-cell research is controversial. Ethical issues about the source of embryonic stem cells limit their availability to researchers. Adult stem cells are found in various tissues in the body. Th...
RESG-874600.indd 103 3/18/06 1:50:00 PM 3/18/06 1:50:00 PM ■ ■ ■ What are homologous chromosomes? The chromosomes that make up a pair, one from each parent, are called homologous (huh MAH luh gus) chromosomes. Homologous chromosomes are the same length and have the centromere in the same place. They also carry genes f...
Gametes are formed during a process called meiosis. Meiosis is a kind of cell division that reduces the number of chromosomes by half through the separation of homologous chromosomes. Meiosis takes place in the reproductive organs of plants and animals. During meiosis, there are two cell divisions. They are called mei...
ers attach to the centromere of each homologous chromosome. What happens during anaphase I? Next is anaphase I. During anaphase I, each homologous chromosome is guided by the spindle ﬁ bers toward opposite poles of the cell. When this happens, the chromosome number is reduced from 2n to n. Notice that the sister chroma...
� bers, and the sister chromatids are pulled to the opposite poles of the cell. In telophase II, the chromosomes reach the poles, and the nuclear membrane and nuclei reform. Cytokinesis, or cell division, occurs. The result is four haploid cells, each with n number of chromosomes. MEIOSIS II 6 Prophase II 10 Products 8...
? Sexual Reproduction v. Asexual Reproduction Asexual reproduction occurs when the organism inherits all of its chromosomes from one parent. The new organism is genetically identical to its parent. Asexual reproduction does not involve meiosis. Bacteria reproduce by asexual reproduction. Plants and some simple animals ...
not understand. After you have read the section, reread the parts you have highlighted. 1. Deﬁ ne What is a true- breeding plant? Reading Essentials Chapter 10 Sexual Reproduction and Genetics 109 103-114 GHSB RESG-874600.indd 109 103-114 GHSB RESG-874600.indd 109 3/18/06 1:50:16 PM 3/18/06 1:50:16 PM ■ ■ What did Men...
1:50:19 PM 4. Predict What would be the phenotype of a heterozygous, recessive (yy) pea plant? 5. Apply True-breeding yellow-seeded and greenseeded plants are crossed and produce yellow-seeded offspring. Which of these plants is a hybrid? How does dominance work? When written, the dominant allele is represented by a c...
9:3:3:1—9 yellow round seeds, 3 green round, 3 yellow wrinkled, and 1 green wrinkled. From experiments with dihybrid crosses, Mendel developed the law of independent assortment, which states that alleles distribute randomly when gametes are made Reading Essentials Chapter 10 Sexual Reproduction and Genetics 111 103-11...
genetics. A cross might not give a perfect 3:1 or 9:3:3:1 ratio. The larger the number of offspring, the more closely the results will match the ratio predicted by the Punnett square 112 Chapter 10 Sexual Reproduction and Genetics biologygmh.com 103-114 GHSB RESG-874600.indd 112 103-114 GHSB RESG-874600.indd 112 3/18/...
/18/06 1:50:26 PM 3/18/06 1:50:26 PM ■ ■ ■ Gene Linkage Chromosomes contain many genes. Genes that are located close together on the same chromosome are said to be linked. This means they usually travel together during gamete formation. Linked genes do not segregate independently. They are an exception to Mendel’s law ...
50:29 PM 11 section ● 1 Complex Inheritance and Human Heredity Basic Patterns of Human Inheritance Before You Read A family tree shows how people in a family are related. On the lines below, list people who might appear in a family tree. Then read the section to learn how scientists trace inheritance through several ge...
liosides build up in the brain of people with Tay-Sachs disease? What is cystic ﬁ brosis? Cystic ﬁ brosis is a recessive genetic trait. Chloride ions are not absorbed into cells but are excreted in sweat. Without the chloride ions in cells, water does not diffuse from cells. This causes the secretion of a thick mucus t...
115-126 GHSB RESG-874600.indd 116 115-126 GHSB RESG-874600.indd 116 3/17/06 1:24:57 PM 3/17/06 1:24:57 PM What happens in Huntington’s disease? Huntington’s disease is a dominant genetic disorder that affects the nervous system. It is rare. Symptoms occur when the person is between 30 and 50 years old. Symptoms are gr...
disorder. The pedigree shows that two parents who do not have Tay-Sachs disease can have a child who has the disorder. Picture This 5. Calculate What percentage of the children in this family inherited Tay-Sachs disease? How is the inheritance of a dominant disorder shown on a pedigree? The pedigree below shows the in...
On the lines below, describe differences you have seen in the coats of cats. Then read the section to learn more about complex inheritance patterns. Read to Learn Incomplete Dominance Not all traits follow Mendel’s rules. Some traits are not dominant or recessive. Sometimes, the heterozygous organism has a mixed pheno...
ozygous for the sickle-cell trait are resistant to malaria. Because the sickle-cell gene helps people resist malaria, they are more likely to pass the sickle-cell trait on to their offspring. Multiple Alleles So far you have learned about traits that result from a gene with two alleles. Some traits are controlled by a ...
occurs when one allele hides the effects of another allele. Coat color in Labrador retrievers is a trait controlled by epistasis. Labrador coats vary from yellow to black. Two different genes control coat color. The dominant allele E determines whether the coat will have dark pigment. A dog with genotype ee will not h...
rst observed inactivated X chromosomes, now known as Barr bodies. Barr bodies appear as dark objects in the cell nuclei of female mammals. Sex-Linked Traits Traits controlled by genes on the X chromosome are called sex-linked traits or X-linked traits. Males who have only one X chromosome are affected more than female...
, but diet and exercise also strongly inﬂ uence the disease. An organism’s actions are considered part of the environment because they do not come from genes. Twin Studies Scientists can learn about inheritance patterns by studying twins. Twin studies often reveal how genes and the environment affect phenotype. Identic...
4600.indd 124 115-126 GHSB RESG-874600.indd 124 3/17/06 1:25:17 PM 3/17/06 1:25:17 PM ■ ■ ■ Telomeres Telomeres are protective caps at the ends of chromosomes. They are made of DNA and proteins. Scientists have discovered that telomeres might be involved in both aging and cancer. Nondisjunction During cell division, th...
Circle the pictures that show a trisomy in the sex chromosomes. 5. State the purpose of fetal testing. Fetal Testing A couple with a genetic disorder in the family might want to know if the developing baby, known as a fetus, has the disorder. Older couples might want to know the chromosome number of the fetus. Many fe...
) because colonies of bacteria appear smooth. Another strain did not have a sugar coat and did not cause pneumonia. It was called rough (R) because its colonies have rough edges. Follow along with Grifﬁ th’s study described on the next page. Identify People As you read this section, underline the name of each scientist...
Who proved that DNA was the genetic material? In spite of Avery’s result, many scientists still questioned whether proteins or DNA were the genetic material. In 1952, Alfred Hershey and Martha Chase published results of an experiment proving that DNA was the genetic material. Hershey and Chase did an experiment with b...
gure below shows the structure of a nucleotide. Adenine (A) and guanine (G) are double-ringed bases, which are called purine bases. Thymine (T), cytosine (C), and uracil (U) are single-ringed bases, which are called pyrimidine bases. Erwin Chargaff discovered that the amount of guanine is almost equal to the amount of...
anine, thymine paired with adenine. What is the structure of DNA? Imagine DNA as a twisted ladder. The rails of the ladder are made of alternating deoxyribose and phosphates. The pairs of bases (cytosine—guanine or thymine—adenine) form the rungs. The rungs are always the same width because a purine base always binds t...
each original strand. What You’ll Learn the role of enzymes in the copying of DNA how leading and lagging DNA strands are made Identify Main Ideas As you read, underline or highlight the main ideas in each paragraph. 1. List the three phases of semiconservative replication. Before You Read DNA is the instruction manua...
inds and nucleotides are added to its 3' end. The other strand, called the lagging strand, becomes longer as small pieces called Okazaki fragments are added in the 3' to 5' direction. How are the fragments joined? DNA polymerase removes RNA primers and replaces them with DNA nucleotides. When the last RNA primer has be...
of events is called the central dogma of biology: DNA codes for RNA, which guides the making of proteins. What are the types of RNA? RNA, like DNA, is a nucleic acid. RNA nucleotides contain the sugar ribose instead of deoxyribose and the base uracil instead of thymine. RNA usually exists in single strands. Cells cont...
In the 1960s, scientists discovered that the DNA code is a three-base code called a codon. Each codon is transcribed into the mRNA code. The genetic code for all 64 codons is shown in the table at the top of the next page. Three codons—UAA, UAG, and UGA—do not code for an amino acid. They are called stop codons becaus...
00.indd 136 3/17/06 1:29:27 PM 3/17/06 1:29:27 PM How does translation work? Transcription takes place in the nucleus. Translation occurs in the cytoplasm. Follow along with the picture below. You will see how the ribosome translates the mRNA code into a chain of amino acids, called a polypeptide. Picture This 5. Ident...
on the mold Neuorspora. The mold spores they studied were mutated by exposure to X rays. Their experiments showed that a gene can code for an enzyme. Based on the results of their experiments, Beadle and Tatum proposed that each gene makes one enzyme, the “one gene—one enzyme” hypothesis. How has the one gene—one enzy...
contains ﬁ ve genes (trpA through trpE) needed to make the amino acid tryptophan. When tryptophan levels are low, RNA polymerase binds to the operator, turning on the transcription of the ﬁ ve enzyme genes needed for tryptophan synthesis. Restate the Main Point Highlight the main point in each paragraph. State each ma...
140 3/17/06 1:29:38 PM 3/17/06 1:29:38 PM Eukaryote Gene Regulation Eukaryotes have many more genes than prokaryotes. They also use different, more complex methods of gene regulation. How do eukaryotes control transcription? Proteins called transcription factors control when a gene is turned on and how much of that pr...
mutations? Insertions and deletions occur when a nucleotide is added or lost. Insertions and deletions can cause a frameshift mutation, causing the ribosome to misread the codons. THE BIG FAT CAT ATE THE WET RAT becomes THE BIG ZFA TCA TAT ETH EWE TRA. Cystic ﬁ brosis and Crohn’s disease are both caused by frameshift ...
874600.indd 142 127-142 GHSB RESG-874600.indd 142 3/17/06 1:29:43 PM 3/17/06 1:29:43 PM 13 section ● Genetics and Biotechnology Applied Genetics 1 Before You Read Imagine that you could design the perfect dog. What color would it be? Would it be big or small? On the lines below, describe the traits your dog would have....
another example of selective breeding. Inbreeding occurs when two closely related organisms that both display the desired trait are bred. Inbreeding can be used to ensure that the desired trait is passed on. Inbreeding can also eliminate traits that are not desired. Purebred animals are created by inbreeding. Clydesda...
-grapefruit tree is crossed with a red-grapefruit tree. The orchard owner uses a Punnett square to understand the results of the cross. The ﬁ gure below shows a Punnett square for the test cross if the white-grapefruit tree is homozygous, meaning it has two dominant genes (WW). All the offspring from the test cross wil...
of an organism by inserting extra DNA or inserting DNA from another organism. One example of genetic engineering uses green ﬂ uorescent protein (GFP). GFP is a protein made naturally in jellyﬁ sh. GFP causes jellyﬁ sh to turn green under ultraviolet light. Scientists have inserted the DNA for making GFP into other org...
compared to the patterns of known DNA fragments for identiﬁ cation. The ﬁ gure below shows a gel in which DNA has been separated by electrophoresis. Explain Why can two different fragments of DNA cut with EcoRI be joined? Picture This 3. Analyze Use the ﬁ gure to explain to a partner how gel electrophoresis works Read...
00.indd 148 143-156 GHSB RESG-874600.indd 148 3/18/06 2:41:04 PM 3/18/06 2:41:04 PM What is DNA sequencing? DNA sequencing involves ﬁ nding out the exact order of the nucleotides that make up an organism’s DNA. Knowing the DNA sequence of an organism gives scientists clues about how that organism’s genes work. Scientis...
Doctors use PCR to detect diseases such as AIDS. What are the steps of PCR? Follow the ﬁ gure below as you read the steps of PCR. Step 1 Four things are mixed in a small tube: the DNA fragment to be copied, DNA polymerase, the four DNA nucleotides—A, G, C, and T—and two short, single-stranded pieces of DNA called prim...
protein during surgery. Several species of ﬁ sh have been genetically engineered to grow faster. In the future, transgenic animals might be used as a source of organs for organ transplants in people. How are transgenic plants used? Transgenic crops are grown around the world. Farmers in at least 18 countries grow tran...
cards to review what you have learned. 1. Calculate What percentage of human DNA is not made of genes? The Human Genome Project A genome is all of the genetic information in a cell. The human genome is all of the genetic information in a human cell. The Human Genome Project (HGP) was an enormous project. One goal was ...
by gel electrophoresis. The pattern of the fragments from the sample is compared with DNA samples from known sources, such as a suspect or a victim in a crime. Identifying Genes Once the genome has been sequenced, the next step is to identify the genes and determine their functions. Organisms, such as bacteria and yea...
microarray can contain thousands of genes. Scientists use DNA microarrays to study the expression of a lot of genes at once. DNA microarrays are used to study when and where genes are expressed. Microarrays can reveal how gene expression changes under different conditions. Microarrays can be used to compare cancer cel...
areas of the world. The HapMap project will enable scientists to take advantage of how SNPs and other genetic variations are organized on chromosomes. This will help scientists ﬁ nd genes that cause different types of disease. The HapMap will also help scientists ﬁ nd mutations that affect how a person responds to med...
study plants and other organisms, such as rice, mice, fruit ﬂ ies, and corn, whose genomes have been sequenced. Genes are important because they are the way cells store information. Proteins are important because they are the machines that make cells run. Proteomics is the large-scale study and cataloging of the struc...
surface. The crust was made mostly of lighter elements. From clues found in rocks, scientists infer that Earth’s early surface was hot. Volcanoes erupted and meteorites hit the surface. It is not likely that life could have survived the heat. Identify Deﬁ nitions As you read each section, highlight or underline the de...
. 158 Chapter 14 The History of Life Reading Essentials 157-168 GHSB RESG-874600.indd 158 157-168 GHSB RESG-874600.indd 158 3/17/06 1:32:59 PM 3/17/06 1:32:59 PM What can scientists learn from studying fossils? A paleontologist (pay lee ahn TAH luh jist) is a scientist who studies fossils. Paleontologists use fossils a...
is a commonly used isotope. The decay of carbon-14 is shown in the graph below. The half-life of carbon-14 is 5730 years. After 5730 years, half of the original carbon-14 will remain. The other half will have decayed to nitrogen-14. At the half-life, there is a one-to-one ratio, or equal amounts, of carbon-14 and nitr...
�s history occurred. It began with the formation of Earth, 4.6 billion years ago, and ended about 542 million years ago with the beginning of the Paleozoic era. Many important events occurred during the Precambrian. Earth formed and life ﬁ rst appeared. Autotrophic prokaryotes, such as bacteria that make organic compou...
157-168 GHSB RESG-874600.indd 161 3/17/06 1:33:06 PM 3/17/06 1:33:06 PM What is the evidence of a meteor striking Earth? Then, a meteorite struck Earth. The evidence for the meteorite comes from a layer of material between rocks of the Cretaceous (krih TAY shus) period and rocks of the Paleogene period. Scientists cal...
included present-day humans? Picture This 13. Label Circle the era when Pangaea broke apart into individual continents. How did life change during the Cenozoic era? The Cenozoic (sen uh ZOH ihk) era is the most recent era. Mammals became the dominant animals on land. At the beginning of the era, most mammals were smal...
? In 1668, an Italian scientist named Francesco Redi tested the idea that ﬂ ies arose spontaneously from rotting meat. He hypothesized that ﬂ ies, not meat, produced other ﬂ ies. Redi placed rotting meat in ﬂ asks that were opened and in ﬂ asks that were covered. Redi observed that maggots, the larvae of ﬂ ies, appeare...
organic molecules could have been made from simple reactions involving those gases in the early oceans. UV light from the sun and lightning might have provided the energy for the reactions. Oparin thought that these organic molecules would eventually lead to life. Picture This 2. Describe What did Pasteur do that allo...
can separate just as easily. Proteins might have formed when an amino acid stuck to a particle of clay. Clay would have been a common sediment in early oceans. Clay could have provided a framework for protein assembly. Explain What ocean sediment might have helped protein chains to form? What was the ﬁ rst genetic cod...
ago. Any oxygen that appeared earlier probably bonded with free iron ions. Scientists hypothesize that eventually early Earth’s free iron was bonded with oxygen so oxygen could accumulate in the environment. Scientists think that prokaryotes, called cyanobacteria, that could perform photosynthesis evolved about 3.5 bi...
they seek answers to understand what led to life on Earth. Take Notes Make a four-door Foldable, as shown below. As you read, take notes and organize what you learn about the endosymbiont theory. Who? Lynn Margulis What? Endosymbiont Theory W h y? H o w? Picture This 8. Highlight the name of the structure that cyanoba...
. 1. Name an observation Charles Darwin made. Reading Essentials Chapter 15 Evolution 169. 169-182 GHSB RESG-874600.indd 169 169-182 GHSB RESG-874600.indd 169 3/17/06 1:36:15 PM 3/17/06 1:36:15 PM ■ ■ 2. Identify Where are the Galápagos Islands? Picture This 3. Explain Each of the Galápagos islands had different types ...

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