Address Resolution protocol - wikipedia

 Address Resolution protocol

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 The Address Resolution Protocol ( ARP ) is a communication protocol used for discovering the link layer address , such as a MAC address , associated with a given network layer address , typically an IPv4 address . This mapping is a critical function in the Internet protocol suite . ARP was defined in 1982 by RFC 826 , which is Internet Standard STD 37 .

 ARP has been implemented with many combinations of network and data link layer technologies , such as IPv4 , Chaosnet , DECnet and Xerox PARC Universal Packet ( PUP ) using IEEE 802 standards , FDDI , X. 25 , Frame Relay and Asynchronous Transfer Mode ( ATM ) . IPv4 over IEEE 802.3 and IEEE 802.11 is the most common usage .

 In Internet Protocol Version 6 ( IPv6 ) networks , the functionality of ARP is provided by the Neighbor Discovery Protocol ( NDP ) .

 Contents

 ( hide )

 1 Operating scope

 2 Packet structure

 3 Example

 4 ARP probe

 5 ARP announcements

 6 ARP mediation

 7 Inverse ARP and Reverse ARP

 8 ARP spoofing and Proxy ARP

 9 Alternatives to ARP

 10 ARP stuffing

 11 Standards documents

 12 See also

 13 References

 14 External links

 Operating scope ( edit )

 The Address Resolution Protocol is a request - response protocol whose messages are encapsulated by a link layer protocol . It is communicated within the boundaries of a single network , never routed across internetworking nodes . This property places ARP into the link layer of the Internet protocol suite .

 Packet structure ( edit )

 The Address Resolution Protocol uses a simple message format containing one address resolution request or response . The size of the ARP message depends on the upper layer and lower layer address sizes , which are given by the type of networking protocol ( usually IPv4 ) in use and the type of hardware or virtual link layer that the upper layer protocol is running on . The message header specifies these types , as well as the size of addresses of each . The message header is completed with the operation code for request ( 1 ) and reply ( 2 ) . The payload of the packet consists of four addresses , the hardware and protocol address of the sender and receiver hosts .

 The principal packet structure of ARP packets is shown in the following table which illustrates the case of IPv4 networks running on Ethernet . In this scenario , the packet has 48 - bit fields for the sender hardware address ( SHA ) and target hardware address ( THA ) , and 32 - bit fields for the corresponding sender and target protocol addresses ( SPA and TPA ) . Thus , the ARP packet size in this case is 28 bytes . The EtherType for ARP is 0x0806 . ( This appears in the Ethernet frame header when the payload is an ARP packet . Not to be confused with PTYPE below , which appears within this encapsulated ARP packet . )

 Internet Protocol ( IPv4 ) over Ethernet ARP packet

 octet offset

 0

 0

 Hardware type ( HTYPE )

 Protocol type ( PTYPE )

 Hardware address length ( HLEN )

 Protocol address length ( PLEN )

 6

 Operation ( OPER )

 8

 Sender hardware address ( SHA ) ( first 2 bytes )

 10

 ( next 2 bytes )

 12

 ( last 2 bytes )

 14

 Sender protocol address ( SPA ) ( first 2 bytes )

 16

 ( last 2 bytes )

 18

 Target hardware address ( THA ) ( first 2 bytes )

 20

 ( next 2 bytes )

 22

 ( last 2 bytes )

 24

 Target protocol address ( TPA ) ( first 2 bytes )

 26

 ( last 2 bytes )

 Hardware type ( HTYPE )

 This field specifies the network protocol type . Example : Ethernet is 1 .

 Protocol type ( PTYPE )

 This field specifies the internetwork protocol for which the ARP request is intended . For IPv4 , this has the value 0x0800 . The permitted PTYPE values share a numbering space with those for EtherType .

 Hardware length ( HLEN )

 Length ( in octets ) of a hardware address . Ethernet addresses size is 6 .

 Protocol length ( PLEN )

 Length ( in octets ) of addresses used in the upper layer protocol . ( The upper layer protocol specified in PTYPE . ) IPv4 address size is 4 .

 Operation

 Specifies the operation that the sender is performing : 1 for request , 2 for reply .

 Sender hardware address ( SHA )

 Media address of the sender . In an ARP request this field is used to indicate the address of the host sending the request . In an ARP reply this field is used to indicate the address of the host that the request was looking for . ( Not necessarily address of the host replying as in the case of virtual media . ) Switches do not pay attention to this field , particularly in learning MAC addresses . The ARP PDU is encapsulated in Ethernet frame , and that is what Layer 2 devices examine .

 Sender protocol address ( SPA )

 Internetwork address of the sender .

 Target hardware address ( THA )

 Media address of the intended receiver . In an ARP request this field is ignored . In an ARP reply this field is used to indicate the address of the host that originated the ARP request .

 Target protocol address ( TPA )

 Internetwork address of the intended receiver .

 ARP protocol parameter values have been standardized and are maintained by the Internet Assigned Numbers Authority ( IANA ) .

 Example ( edit )

 Two computers in an office ( computer 1 and computer 2 ) are connected to each other in a local area network by Ethernet cables and network switches , with no intervening gateways or routers . Computer 1 has a packet to send to Computer 2 . Through DNS , it determines that Computer 2 has the IP address 192.168. 0.55 . To send the message , it also requires Computer 2 's MAC address . First , Computer 1 uses a cached ARP table to look up 192.168. 0.55 for any existing records of Computer 2 's MAC address ( 00 : eb : 24 : b2 : 05 : ac ) . If the MAC address is found , it sends an Ethernet frame with destination address 00 : eb : 24 : b2 : 05 : ac , containing the IP packet onto the link . If the cache did not produce a result for 192.168. 0.55 , Computer 1 has to send a broadcast ARP message ( destination FF : FF : FF : FF : FF : FF MAC address ) , which is accepted by all computers , requesting an answer for 192.168. 0.55 . Computer 2 responds with its MAC and IP addresses . Computer 2 may insert an entry for Computer 1 into its ARP table for future use . Computer 1 caches the response information in its ARP table and can now send the packet .

 ARP probe ( edit )

 An ARP probe is an ARP request constructed with an all - zero sender IP address ( SPA ) . The term is used in the IPv4 Address Conflict Detection specification ( RFC 5227 ) . Before beginning to use an IPv4 address ( whether received from manual configuration , DHCP , or some other means ) , a host implementing this specification must test to see if the address is already in use , by broadcasting ARP probe packets .

 ARP announcements ( edit )

 ARP may also be used as a simple announcement protocol . This is useful for updating other hosts ' mappings of a hardware address when the sender 's IP address or MAC address has changed . Such an announcement , also called a gratuitous ARP message , is usually broadcast as an ARP request containing the sender 's protocol address ( SPA ) in the target field ( TPA = SPA ) , with the target hardware address ( THA ) set to zero . An alternative way is to broadcast an ARP reply with the sender 's hardware and protocol addresses ( SHA and SPA ) duplicated in the target fields ( TPA = SPA , THA = SHA ) .

 The gratuitous ARP request message and the gratuitous ARP reply messages are standards - based methods , but the `` ARP Request '' is preferred . Some devices may be configured for the use of either of these two types of GARP .

 An ARP announcement is not intended to solicit a reply ; instead it updates any cached entries in the ARP tables of other hosts that receive the packet . The operation code may indicate a request or a reply because the ARP standard specifies that the opcode is only processed after the ARP table has been updated from the address fields .

 Many operating systems perform gratuitous ARP during startup . That helps to resolve problems which would otherwise occur if , for example , a network card was recently changed ( changing the IP - address - to - MAC - address mapping ) and other hosts still have the old mapping in their ARP caches .

 Gratuitous ARP is also used by some interface drivers to provide load balancing for incoming traffic . In a team of network cards , it is used to announce a different MAC address within the team that should receive incoming packets .

 ARP announcements can be used to defend link - local IP addresses in the Zeroconf protocol ( RFC 3927 ) , and for IP address takeover within high - availability clusters .

 ARP mediation ( edit )

 ARP mediation refers to the process of resolving Layer 2 addresses through a Virtual Private Wire Service ( VPWS ) when different resolution protocols are used on the connected circuits , e.g. , Ethernet on one end and Frame Relay on the other . In IPv4 , each Provider Edge ( PE ) device discovers the IP address of the locally attached Customer Edge ( CE ) device and distributes that IP address to the corresponding remote PE device . Then each PE device responds to local ARP requests using the IP address of the remote CE device and the hardware address of the local PE device . In IPv6 , each PE device discovers the IP address of both local and remote CE devices and then intercepts local Neighbor Discovery ( ND ) and Inverse Neighbor Discovery ( IND ) packets and forwards them to the remote PE device .

 Inverse ARP and Reverse ARP ( edit )

 Inverse Address Resolution Protocol ( Inverse ARP or InARP ) is used to obtain Network Layer addresses ( for example , IP addresses ) of other nodes from Data Link Layer ( Layer 2 ) addresses . It is primarily used in Frame Relay ( DLCI ) and ATM networks , in which Layer 2 addresses of virtual circuits are sometimes obtained from Layer 2 signaling , and the corresponding Layer 3 addresses must be available before those virtual circuits can be used .

 Since ARP translates Layer 3 addresses to Layer 2 addresses , InARP may be described as its inverse . In addition , InARP is implemented as a protocol extension to ARP : it uses the same packet format as ARP , but different operation codes .

 The Reverse Address Resolution Protocol ( Reverse ARP or RARP ) , like InARP , translates Layer 2 addresses to Layer 3 addresses . However , in ARP the requesting station queries the Layer 3 address of another node , whereas RARP is used to obtain the Layer 3 address of the requesting station itself for address configuration purposes . RARP is obsolete ; it was replaced by BOOTP , which was later superseded by the Dynamic Host Configuration Protocol ( DHCP ) .

 ARP spoofing and proxy ARP ( edit )

 A successful ARP spoofing attack allows an attacker to perform a man - in - the - middle attack . Main article : ARP spoofing Main article : Proxy ARP

 Because ARP does not provide methods for authenticating ARP replies on a network , ARP replies can come from systems other than the one with the required Layer 2 address . An ARP proxy is a system which answers the ARP request on behalf of another system for which it will forward traffic , normally as a part of the network 's design , such as for a dialup internet service . By contrast , in ARP spoofing the answering system , or spoofer , replies to a request for another system 's address with the aim of intercepting data bound for that system . A malicious user may use ARP spoofing to perform a man - in - the - middle or denial - of - service attack on other users on the network . Various software exists to both detect and perform ARP spoofing attacks , though ARP itself does not provide any methods of protection from such attacks .

 Alternatives to ARP ( edit )

 Each computer maintains a database of the mapping of Layer 3 addresses ( e.g. , IP addresses ) to Layer 2 addresses ( e.g. , Ethernet MAC addresses ) , which is maintained primarily by the reception of ARP packets form the local network link . Thus , it is often called the ARP cache . Traditionally , other methods were also used to maintain this table , such as static configuration files , or centrally maintained lists .

 Since at least the 1980s , networked computers have a utility called ' arp ' for interrogating or manipulating this table .

 ARP stuffing ( edit )

 Embedded systems such as networked cameras and networked power distribution devices , which lack a user interface , can use so - called ARP stuffing to make an initial network connection , although this is a misnomer , as ARP is not involved .

 This is a solution to an issue in network management of consumer devices , specifically the allocation of IP addresses of ethernet devices where :

 the user does n't have the ability to control DHCP or similar address allocation protocols

 the device does n't have a user interface to configure it with

 the user 's computer ca n't communicate with it because it has no suitable IP address .

 The solution adopted is as follows :

 The user 's computer has an IP address stuffed manually into its address table ( normally with the arp command with the MAC address taken from a label on the device )

 The computer sends special packets to the device , typically a ping packet with a non-default size .

 The device then adopts this IP address

 The user then communicates with it by telnet or web protocols to complete the configuration .

 Such devices typically have a method to disable this process once the device is operating normally , as it is vulnerable to attack .

 Standards documents ( edit )

 RFC 826 - Ethernet Address Resolution Protocol , Internet Standard STD 37 .

 RFC 903 - Reverse Address Resolution Protocol , Internet Standard STD 38 .

 RFC 2390 - Inverse Address Resolution Protocol , draft standard

 RFC 5227 - IPv4 Address Conflict Detection , proposed standard

 See also ( edit )

 ARP spoofing

 Arping

 Arptables

 Arpwatch

 Bonjour Sleep Proxy

 Cisco HDLC

 Neighbor Discovery Protocol

 Proxy ARP

 References ( edit )

 Jump up ^ David C. Plummer ( November 1982 ) . `` RFC 826 , An Ethernet Address Resolution Protocol -- or -- Converting Network Protocol Addresses to 48. bit Ethernet Address for Transmission on Ethernet Hardware '' . Internet Engineering Task Force , Network Working Group .

 Jump up ^ Braden , R. ( October 1989 ) . `` RFC 1122 - Requirements for Internet Hosts -- Communication Layers '' . Internet Engineering Task Force .

 Jump up ^ IANA ARP - `` Protocol Type ''

 Jump up ^ IANA - Ethertype values

 Jump up ^ RFC 5342

 Jump up ^ `` IANA ARP parameter assignments '' . IANA. 2009 - 04 - 24 .

 Jump up ^ Chappell , Laura A. and Tittel , Ed . Guide to TCP / IP , Third Edition . Thomson Course Technology , 2007 , pp. 115 - 116 .

 Jump up ^ Cheshire , S. ( July 2008 ) . `` RFC 5227 - IPv4 Address Conflict Detection '' . Internet Engineering Task Force .

 Jump up ^ Perkins , C. ( November 2010 ) . `` RFC 5944 - IP Mobility Support for IPv4 , Revised '' . Internet Engineering Task Force . A gratuitous ARP MAY use either an ARP Request or an ARP Reply packet . ( ... ) any node receiving any ARP packet ( Request or Reply ) MUST update its local ARP cache with the Sender Protocol and Hardware Addresses in the ARP packet ( ... )

 Jump up ^ Perkins , C. ( October 1996 ) . `` RFC 2002 - IP Mobility Support '' . Internet Engineering Task Force .

 Jump up ^ Cheshire , S. ( July 2008 ) . `` RFC 5227 - IPv4 Address Conflict Detection '' . Internet Engineering Task Force . Why Are ARP Announcements Performed Using ARP Request Packets and Not ARP Reply Packets ?

 Jump up ^ `` FAQ : The Firewall Does not Update the Address Resolution Protocol Table '' . Citrix. 2015 - 01 - 16 . ( ... ) garpReply enabled ( ... ) generates ARP packets that ( ... ) are of OPCODE type REPLY , rather than REQUEST .

 Jump up ^ Gratuitous ARP in DHCP vs. IPv4 ACD Draft Archived October 12 , 2007 , at the Wayback Machine .

 Jump up ^ RFC 2002 Section 4.6

 Jump up ^ RFC 2131 DHCP -- Last lines of Section 4.4. 1

 Jump up ^ Shah , H. ; et al. ( June 2012 ) . `` RFC 6575 Address Resolution Protocol ( ARP ) Mediation for IP Interworking of Layer 2 VPNs '' . Internet Engineering Task Force .

 Jump up ^ T. Bradley ; et al. ( September 1998 ) . `` RFC 2390 - Inverse Address Resolution Protocol '' . Internet Engineering Task Force .

 Jump up ^ Finlayson , Mann , Mogul , Theimer ( June 1984 ) . `` RFC 903 - A Reverse Address Resolution Protocol '' . Internet Engineering Task Force . CS1 maint : Uses authors parameter ( link )

 Jump up ^ Steve Gibson ( 2005 - 12 - 11 ) . `` ARP Cache Poisoning '' . GRC .

 Jump up ^ Sun Microsystems . `` SunOS manual page for ethers ( 5 ) file '' . Retrieved 2011 - 09 - 28 .

 Jump up ^ University of California , Berkeley . `` BSD manual page for arp ( 8C ) command '' . Retrieved 2011 - 09 - 28 .

 Jump up ^ Canonical . `` Ubuntu manual page for arp ( 8 ) command '' . Archived from the original on 2012 - 03 - 16 . Retrieved 2011 - 09 - 28 .

 Jump up ^ Apple Computer . `` Mac OS X manual page for arp ( 8 ) command '' . Retrieved 2011 - 09 - 28 .

 Jump up ^ Microsoft . `` Windows help for arp command '' . Retrieved 2011 - 09 - 28 .

 Jump up ^ Axis Communication . `` Axis P13 Network Camera Series Installation Guide '' ( PDF ) . Retrieved 2011 - 09 - 28 .

 Jump up ^ American Power Corporation . `` Switched Rack Power Distribution Unit Installation and Quick Start Manual '' ( PDF ) . Retrieved 2011 - 09 - 28 .

 This article is based on material taken from the Free On - line Dictionary of Computing prior to 1 November 2008 and incorporated under the `` relicensing '' terms of the GFDL , version 1.3 or later .

 External links ( edit )

 Wikiversity has learning resources about Address Resolution Protocol

 ARP Sequence Diagram ( pdf )

 Gratuitous ARP

 ARP - SK ARP traffic generation tools

 Sample Capture file from WireSharkWiki

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Question: the arp request is sent to which of the following layer 2 destination addresses


Central London Property Trust Ltd v. High Trees House Ltd - wikipedia

 Central London Property Trust Ltd v. High Trees House Ltd

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 High Trees case

 Court

 King 's Bench Division

 Decided

 18 July 1946

 Citation ( s )

 ( 1947 ) KB 130 ; ( 1956 ) 1 All ER 256 ; 62 TLR 557 ; ( 1947 ) LJR 77 ; 175 LT 333

 Court membership

 Judge ( s ) sitting

 Denning J

 Keywords

 Promissory estoppel

 Central London Property Trust Ltd v High Trees House Ltd ( 1947 ) KB 130 ( or the High Trees case ) is an English contract law decision in the High Court . It reaffirmed and extended the doctrine of promissory estoppel in contract law in England and Wales . However , the most significant part of the judgment is obiter dicta as it relates to hypothetical facts ; that is , the landlord did not seek repayment of the full wartime rent .

 Denning J held estoppel to be applicable if ...

 ... a promise was made which was intended to create legal relations and which , to the knowledge of the person making the promise , was going to be acted on by the person to whom it was made and which was in fact so acted on .

 Contents

 ( hide )

 1 Facts

 2 Judgment

 3 Significance

 4 See also

 5 References

 Facts ( edit )

 In 1937 , High Trees House Ltd leased a block of flats in Clapham , London , for a rate £ 2500 / year from Central London Property Trust Ltd . Due to the conditions during the beginning of World War II occupancy rates were drastically lower than normal .

 In January 1940 , to ameliorate the situation , the parties made an agreement in writing to reduce rent by half . However , neither party stipulated the period for which this reduced rental was to apply . Over the next five years , High Trees paid the reduced rate while the flats began to fill , and by 1945 , the flats were back at full occupancy . Central London sued for payment of the full rental costs from June 1945 onwards ( i.e. for last two quarters of 1945 ) .

 Judgment ( edit )

 Based on previous judgments as Hughes v Metropolitan Railway Co , Denning J held that the full rent was payable from the time that the flats became fully occupied in mid-1945 . However , he continued in an obiter statement that if Central London had tried to claim for the full rent from 1940 onwards , they would not have been able to . This was reasoned on the basis that if a party leads another party to believe that he will not enforce his strict legal rights , then the Courts will prevent him from doing so at a later stage . Being obiter dicta and in a court of first instance this was doubly not a binding precedent , yet it essentially created the doctrine of promissory estoppel .

 If I were to consider this matter without regard to recent developments in the law , there is no doubt that had the plaintiffs claimed it , they would have been entitled to recover ground rent at the rate of £ 2,500 a year from the beginning of the term , since the lease under which it was payable was a lease under seal which , according to the old common law , could not be varied by an agreement by parol ( whether in writing or not ) , but only by deed . Equity , however stepped in , and said that if there has been a variation of a deed by a simple contract ( which in the case of a lease required to be in writing would have to be evidenced by writing ) , the courts may give effect to it as is shown in Berry v. Berry ( 1929 ) 2 K.B. 316 . That equitable doctrine , however , could hardly apply in the present case because the variation here might be said to have been made without consideration . With regard to estoppel , the representation made in relation to reducing the rent was not a representation of an existing fact . It was a representation , in effect , as to the future , namely , that payment of the rent would not be enforced at the full rate but only at the reduced rate . Such a representation would not give rise to an estoppel , because , as was said in Jorden v. Money ( 1854 ) 5 H.L.C. 185 , a representation as to the future must be embodied as a contract or be nothing .

 But what is the position in view of developments in the law in recent years ? The law has not been standing still since Jorden v. Money ( 1854 ) 5 H.L.C. 185 . There has been a series of decisions over the last fifty years which , although they are said to be cases of estoppel are not really such . They are cases in which a promise was made which was intended to create legal relations and which , to the knowledge of the person making the promise , was going to be acted on by the person to whom it was made and which was in fact so acted on . In such cases the courts have said that the promise must be honoured . The cases to which I particularly desire to refer are : Fenner v. Blake ( 1900 ) 1 Q.B. 426 , In re Wickham ( 1917 ) 34 T.L.R. 158 , Re William Porter & Co. , Ld. ( 1937 ) 2 All E.R. 361 and Buttery v. Pickard ( 1946 ) W.N. 25 . As I have said they are not cases of estoppel in the strict sense . They are really promises - promises intended to be binding , intended to be acted on , and in fact acted on . Jorden v. Money ( 1854 ) 5 H.L.C. 185 can be distinguished , because there the promisor made it clear that she did not intend to be legally bound , whereas in the cases to which I refer the proper inference was that the promisor did intend to be bound . In each case the court held the promise to be binding on the party making it , even though under the old common law it might be difficult to find any consideration for it . The courts have not gone so far as to give a cause of action in damages for the breach of such a promise , but they have refused to allow the party making it to act inconsistently with it . It is in that sense , and that sense only , that such a promise gives rise to an estoppel . The decisions are a natural result of the fusion of law and equity : for the cases of Hughes v. Metropolitan Ry. Co. ( 1877 ) 2 App . Cas. 439 , 448 , Birmingham and District Land Co. v. London & North Western Ry. Co. ( 1888 ) 40 Ch . D. 268 , 286 and Salisbury ( Marquess ) v. Gilmore ( 1942 ) 2 K.B. 38 , 51 , afford a sufficient basis for saying that a party would not be allowed in equity to go back on such a promise . In my opinion , the time has now come for the validity of such a promise to be recognized . The logical consequence , no doubt is that a promise to accept a smaller sum in discharge of a larger sum , if acted upon , is binding notwithstanding the absence of consideration : and if the fusion of law and equity leads to this result , so much the better . That aspect was not considered in Foakes v. Beer ( 1884 ) 9 App . Cas. 605 . At this time of day however , when law and equity have been joined together for over seventy years , principles must be reconsidered in the light of their combined effect . It is to be noticed that in the Sixth Interim Report of the Law Revision Committee , pars. 35 , 40 , it is recommended that such a promise as that to which I have referred should be enforceable in law even though no consideration for it has been given by the promisee . It seems to me that , to the extent I have mentioned , that result has now been achieved by the decisions of the courts .

 I am satisfied that a promise such as that to which I have referred is binding and the only question remaining for my consideration is the scope of the promise in the present case . I am satisfied on all the evidence that the promise here was that the ground rent should be reduced to £ 1,250 a year as a temporary expedient while the block of flats was not fully , or substantially fully let , owing to the conditions prevailing . That means that the reduction in the rent applied throughout the years down to the end of 1944 , but early in 1945 it is plain that the flats were fully let , and , indeed the rents received from them ( many of them not being affected by the Rent Restrictions Acts ) , were increased beyond the figure at which it was originally contemplated that they would be let . At all events the rent from them must have been very considerable . I find that the conditions prevailing at the time when the reduction in rent was made , had completely passed away by the early months of 1945 . I am satisfied that the promise was understood by all parties only to apply under the conditions prevailing at the time when it was made , namely , when the flats were only partially let , and that it did not extend any further than that . When the flats became fully let , early in 1945 , the reduction ceased to apply .

 In those circumstances , under the law as I hold it , it seems to me that rent is payable at the full rate for the quarters ending September 29 and December 25 , 1945 .

 If the case had been one of estoppel , it might be said that in any event the estoppel would cease when the conditions to which the representation applied came to an end , or it also might be said that it would only come to an end on notice . In either case it is only a way of ascertaining what is the scope of the representation . I prefer to apply the principle that a promise intended to be binding , intended to be acted on and in fact acted on , is binding so far as its terms properly apply . Here it was binding as covering the period down to the early part of 1945 , and as from that time full rent is payable .

 I therefore give judgment for the plaintiff company for the amount claimed .

 Significance ( edit )

 Advances have been made in promissory estoppel since its inception in High Trees to create a new inroad into the rule in Pinnel 's case that an agreement to accept part payment of a debt in full satisfaction of it is unenforceable for want of consideration . Denning commented that such an agreement should now be enforceable under the doctrine of promissory estoppel , and indeed the plaintiff did not seek the full debt on the basis of what was fair and , perhaps , thought was the law . However , the courts were at first reluctant to overrule or distinguish cases like Pinnel 's case and Foakes v Beer having formed part of the common law for so long . Lady Justice Arden in Collier v P & MJ Wright ( Holdings ) Ltd ( 2007 ) accepted in principle that High Trees could be used to extinguish a creditor 's right to full payment of a debt in such circumstances .

 In Amalgamated Investment Co v Texas Bank it was decided that proprietory estoppel can act as a sword and not merely as a shield ( that is , it can be used as a cause of action rather than merely providing a defence to an action ) .

 See also ( edit )

 English contract law

 Estoppel

 Promise

 References ( edit )

 Jump up ^ Collier v P & MJ Wright ( Holdings ) Ltd ( 2007 ) EWCA Civ 1329

 Jump up ^ Amalgamated Investment Co v Texas Bank , ( 1982 ) EWHC 84 ( QB ) .

 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Central_London_Property_Trust_Ltd_v_High_Trees_House_Ltd&oldid=837737647 '' Categories :

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Question: central london properties v high trees house 1947


New Earswick - wikipedia

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 New Earswick

 New Earswick New Earswick shown within North Yorkshire

 Population

 2,737 ( 2011 )

 OS grid reference

 SE609555

 Civil parish

 New Earswick

 Unitary authority

 City of York

 Ceremonial county

 North Yorkshire

 Region

 Yorkshire and the Humber

 Country

 England

 Sovereign state

 United Kingdom

 Post town

 YORK

 Postcode district

 YO32

 Dialling code

 01904

 Police

 North Yorkshire

 Fire

 North Yorkshire

 Ambulance

 Yorkshire

 EU Parliament

 Yorkshire and the Humber

 UK Parliament

 York Outer

 List of places

 UK

 England

 Yorkshire

 53 ° 59 ′ 31 '' N 1 ° 04 ′ 21 '' W  /  53.992020 ° N 1.072380 ° W  / 53.992020 ; - 1.072380 Coordinates : 53 ° 59 ′ 31 '' N 1 ° 04 ′ 21 '' W  /  53.992020 ° N 1.072380 ° W  / 53.992020 ; - 1.072380

 New Earswick is a model village and civil parish in the unitary authority of City of York in North Yorkshire , England , near the River Foss , north of York and south of Haxby . According to the 2001 census the parish had a population of 2,812 , reducing to 2,737 at the 2011 Census . Before 1996 it had been part of the Ryedale district .

 Contents

 ( hide )

 1 History

 2 Governance

 3 Community

 4 Geography

 5 Economy

 6 Transport

 7 Education

 8 Religious sites

 9 Sport

 10 Gallery

 11 References

 12 External links

 History ( edit )

 The village of New Earswick was built as a genuine mixed community . There was housing for both workers and managers , in a green setting with gardens for each home with its own 2 fruit trees . It was founded by the York philanthropist , Joseph Rowntree , who was quoted as saying , `` I do not want to establish communities bearing the stamp of charity but rather of rightly ordered and self governing communities '' . The first 28 houses were built between 1902 and 1904 by the architect Raymond Unwin , after which the Joseph Rowntree Village Trust ( now the Joseph Rowntree Housing Trust ) was established to continue building and manage the new village . The Joseph Rowntree Housing Trust is part of the Joseph Rowntree Foundation .

 The village had contemporaries such as Bournville , Saltaire , Port Sunlight and others . This was in sharp contrast to the slums that had developed in York and other cities during the previous century , the deprivation of which had been revealed in Seebohm Rowntree 's report of 1901 , entitled Poverty : a study of town life . It revealed appalling statistics of dark , overcrowded and insanitary housing .

 As a result of the report , Joseph Rowntree 's conviction that it must be possible to provide better housing for people on low incomes led him to acquire 150 acres of land near the village of Earswick , two and a half miles to the north of the centre of York . The planner Raymond Unwin and the architect Barry Parker were commissioned to produce an overall plan for a new ' garden ' village and the detailed designs for its first houses . They also designed the garden cities of Letchworth and Welwyn Garden City .

 The building of New Earswick created a balanced village community where rents were kept low , but still represented a modest commercial return on the capital invested . Houses were open to any working people , not just Rowntree employees . The village was to be a demonstration of good practice .

 The Trust Deed of the Joseph Rowntree Village Trust , which was set up in 1904 to build and manage New Earswick , safeguarded generous open green space . All the grass verges were planted with trees after which almost all the roads are named . The village was built with bricks that were made in the brickworks on the outskirts of New Earswick . From 1950 the brickyard , which closed down in the 1930s , was developed into a nature reserve .

 Due to their religious beliefs , The Rowntree family decreed there would not be a public house in the village . There never has been , although the Sports Club obtained a drink 's license in the 1980s .

 Governance ( edit )

 New Earswick is part of the Huntington & New Earswick Ward of the City of York Council . As of 2010 it is represented by Keith Hyman , Keith Orrel and Carol Runciman who are all members of the local Liberal Democrat Party .

 A Parish Council was created in 1934 consisting of ten elected councillors and a clerk .

 Community ( edit )

 There is a local community centre , the Folk Hall , which hosts activities such as keep - fit , yoga , snooker , and a junior youth club . New Earswick has recreational facilities , including a swimming pool ( due for closure without public consultation ) , tennis courts and football , rugby and cricket pitches at the New Earswick Sports and Social Club . There were two open access play areas close to the Folk Hall , including a hard surface play area which have recently been bulldozed for a development of houses . There is a library based in the Integrated Children 's Centre at the local primary school , a doctor 's surgery and a range of shops , including two general stores , a pet shop and Post Office . As of 2017 the Post Office is situated within the Folk Hall .

 The village has 36 allotments in two areas , Willow Bank and Sleeper Path .

 In the 1960s , the Folk Hall was a live music venue featuring the likes of Procol Harum and Pink Floyd .

 Geography ( edit )

 The River Foss runs along the eastern boundary of New Earswick with the York to Scarborough Line running to the west . The Nestle factory and grounds mark the southern border with the northern border being the A1237 York Outer Ring Road . The village was built using bricks from the brickworks on the outskirts of the village . From 1950 the brickyard was developed into a nature reserve . The reserve is the home of New Earswick Angling Club , which was formed in 1948 .

 Economy ( edit )

 Unlike the villages of Port Sunlight , Saltaire and Bournville the village was not designed specifically for the workforce of the nearby Joseph Rowntree Cocoa Works although some do earn their living at the factory which was taken over by Swiss firm , Nestle .

 Transport ( edit )

 Transdev York operate a bus service that stops in the village as part of the Askham Bar to Clifton Moor route . First Group operate two bus services that stop in the village as part of the Wigginton to Acomb and Haxby to York City Centre routes .

 New Earswick was served by Earswick railway station on the York to Beverley Line between 1847 and 1965 .

 Education ( edit )

 There are both primary and secondary schools in New Earswick . New Earswick Primary School was built in 1912 . The primary school is one of eight Integrated Children 's Centres in York . Joseph Rowntree School is a secondary school and was built in 1941 . In 2006 , the Joseph Rowntree School secured £ 27million for a complete rebuild that was completed in late 2009 . The catchement area for the secondary school is from the village itself , Huntington , The Groves and the villages of Haxby and Wigginton .

 Religious sites ( edit )

 In 1914 the Anglican church of St. Andrew 's was built on the edge of the parish . The church was extended in 1939 to cater for the new housing in South Huntington just across the River Foss . A Methodist chapel and meeting house for the Society of Friends were added later . St. Andrew 's Church is now part of the ecclesiastical parish of Huntington and New Earswick .

 Sport ( edit )

 New Earswick Cricket Club play at the recreation ground on White Rose Avenue . As of 2014 their two teams will play in Division 3 ( South ) and Division 4 ( Central ) of the York and District Senior Cricket League .

 The recreation ground is shared with New Earswick All Blacks , an open age rugby league club that was founded in the 1980s and currently play in The Pennines Amateur Rugby League competition , in 2013 / 4 , playing in the Championship ( the second tier ) .

 Steve Webster , 10 times FIM Sidecar World Championships , world champion was born and raised in the village. .

 Gallery ( edit )

 Views of New Earswick

 The Folk Hall in New Earswick

 White Rose Avenue in New Earswick

 Westfield Beck behind housing on the west of New Earswick

 References ( edit )

 Jump up ^ `` Civil Parish population 2011 '' . Neighbourhood Statistics . Office for National Statistics . Retrieved 19 February 2016 .

 Jump up ^ `` Village History '' . Retrieved 12 December 2010 .

 Jump up ^ `` Village planning '' . Retrieved 12 December 2010 .

 Jump up ^ `` New Earswick : a village of new ideas '' . BBC . Retrieved 29 March 2014 .

 Jump up ^ `` Couoncillors '' . Retrieved 12 December 2010 .

 ^ Jump up to : `` Village Information '' ( PDF ) . Archived from the original ( PDF ) on 4 October 2013 . Retrieved 12 December 2010 .

 Jump up ^ `` Procol Harum and Pink Floyd play New Earswick '' . Archived from the original on 30 March 2014 .

 Jump up ^ `` Transdev Bus Service '' . Retrieved 12 December 2010 .

 Jump up ^ `` First Bus Services '' . Retrieved 12 December 2010 .

 Jump up ^ Butt , R.V.J. ( 1995 ) . The Directory of Railway Stations : details every public and private passenger station , halt , platform and stopping place , past and present ( 1st ed . ) . Sparkford : Patrick Stephens Ltd . ISBN 978 - 1 - 85260 - 508 - 7 . OCLC 60251199 .

 Jump up ^ `` Primary School '' . Retrieved 12 December 2010 .

 Jump up ^ `` Catchment Area '' ( PDF ) . Retrieved 12 December 2010 .

 Jump up ^ `` Cricket '' . Retrieved 16 March 2014 .

 Jump up ^ `` New Earswick All Blacks '' . Archived from the original on 16 January 2008 .

 Jump up ^ Havard , Jane ( 1992 ) . A Bit On The Side . Menoshire . p. 1 . ISBN 0947981667 .

 External links ( edit )

 `` New Earswick , York '' . The Joseph Rowntree Housing Trust . Retrieved 4 March 2017 .

 Retrieved from `` https://en.wikipedia.org/w/index.php?title=New_Earswick&oldid=826057861 '' Categories :

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Question: who designed the garden city of new earswick


Now That I 've Found You : a Collection - wikipedia

 Now That I 've Found You : a Collection

 Jump to : navigation , search

 Now That I 've Found You : A Collection

 Compilation album by Alison Krauss

 Released

 February 7 , 1995

 Genre

 Bluegrass / Country

 Length

 42 : 31

 Label

 Rounder

 Producer

 Alison Krauss & Union Station

 Alison Krauss chronology

 I Know Who Holds Tomorrow ( 1994 ) I Know Who Holds Tomorrow 1994

 Now That I 've Found You : A Collection ( 1995 )

 So Long So Wrong ( 1997 ) So Long So Wrong 1997

 Singles from Now That I 've Found You : A Collection

 `` Baby , Now That I 've Found You '' Released : 1995

 `` Oh , Atlanta '' Released : 1995

 Professional ratings

 Review scores

 Source

 Rating

 Allmusic

 Robert Christgau

 A −

 Rolling Stone

 Now That I 've Found You : A Collection is an album by Alison Krauss , released February 7 , 1995 . It is a retrospective of the early part of Krauss ' recording career . It includes songs that appeared on her solo albums , albums by Alison Krauss & Union Station , and some that appeared on an album by Alison Krauss & the Cox Family . It also contains some new material .

 The album features the hit country single `` When You Say Nothing at All '' , sold over two million copies earning double platinum RIAA certification . The title single `` Baby , Now That I 've Found You '' won the Grammy Award for Best Female Country Vocal Performance and `` When You Say Nothing at All '' was named Single of the Year by the Country Music Association .

 Contents

 ( hide )

 1 Track listing

 2 Personnel

 3 Chart performance

 3.1 Album

 4 References

 Track listing ( edit )

 `` Baby , Now That I 've Found You '' ( Tony Macaulay , John MacLeod ) -- 3 : 49

 ( Previously Unreleased )

 `` Oh , Atlanta '' ( Mick Ralphs ) -- 4 : 41

 ( Previously Unreleased )

 `` Broadway '' ( Sidney & Suzanne Cox ) -- 3 : 57

 ( Previously Unreleased )

 `` Every Time You Say Goodbye '' ( John Pennell ) -- 3 : 13

 ( From the Album `` Every Time You Say Goodbye '' by Alison Krauss & Union Station )

 `` Tonight I 'll Be Lonely Too '' ( Sidney Cox ) -- 3 : 25

 ( From the Album `` I 've Got That Old Feeling '' by Alison Krauss )

 `` Teardrops Will Kiss the Morning Dew '' ( Paul Craft ) -- 3 : 38

 ( From the Album `` Two Highways '' by Alison Krauss & Union Station )

 `` Sleep On '' ( Nelson Mandrell ) -- 2 : 23

 ( From the Album `` Too Late to Cry '' by Alison Krauss )

 `` When God Dips His Pen of Love in My Heart '' ( Cleavant Derricks ) -- 2 : 26

 ( From the Album `` Everybody 's Reaching Out for Someone '' by The Cox Family )

 `` I Will '' ( John Lennon , Paul McCartney ) -- 4 : 04

 ( From the Album `` Within Reach '' by Tony Furtado )

 `` I Do n't Believe You 've Met My Baby '' ( Autry Inman ) -- 3 : 10

 ( From the Album `` Slide Rule '' by Jerry Douglas )

 `` In the Palm of Your Hand '' ( Ron Block ) -- 3 : 24

 ( From the Album `` I Know Who Holds Tomorrow '' by Alison Krauss & The Cox Family )

 `` When You Say Nothing at All '' ( Paul Overstreet , Don Schlitz ) -- 4 : 21

 ( From the Album `` Keith Whitley : A Tribute Album '' performed by Alison Krauss & Union Station )

 Personnel ( edit )

 Alison Krauss : Vocal , Fiddle , Viola

 Ron Block : Vocal , Acoustic & Electric Guitars , Banjo

 Russ Barenberg , Mike Marshall , Scott Nygaard , Tim Stafford : Guitars

 Jerry Douglas : Guitars , Dobro

 Sam Bush , Brent Truitt : Mandolin

 Stuart Duncan : Fiddle , Harmonica , Cymbals

 Adam Steffey : Mandolin & Mandola

 Pete Wasner : Piano

 Chart performance ( edit )

 Album ( edit )

 Chart ( 1995 )

 Peak position

 Canadian RPM Country Albums

 U.S. Billboard 200

 13

 U.S. Billboard Top Country Albums

 References ( edit )

 Jump up ^ Allmusic review

 Jump up ^ Robert Christgau review

 Jump up ^ Rolling Stone review

 ^ Jump up to : Alison Krauss Artist Chart Position at Billboard

 Now That I 've Found You for Rounder Records . Retrieved August 28 , 2010 .

 Alison Krauss bio for CMT.com . Retrieved June 7 , 2006 .

 Now That I 've Found You on Amazon . Retrieved June 7 , 2006 .

 Preceded by The Woman in Me by Shania Twain

 RPM Country Albums number - one album October 30 - November 5 , 1995

 Succeeded by Starting Over by Reba McEntire

 ( hide )

 Alison Krauss & Union Station

 Alison Krauss

 Barry Bales

 Ron Block

 Jerry Douglas

 Dan Tyminski

 John Pennell

 Jeff White

 Brent Truitt

 Mike Harman

 Adam Steffey

 Tim Stafford

 Studio albums

 Different Strokes

 Too Late to Cry

 Two Highways

 I 've Got That Old Feeling

 Every Time You Say Goodbye

 I Know Who Holds Tomorrow

 So Long So Wrong

 Forget About It

 New Favorite

 Lonely Runs Both Ways

 Paper Airplane

 Windy City

 Compilation albums

 Now That I 've Found You : A Collection

 Live

 A Hundred Miles or More : A Collection

 Essential Alison Krauss

 With Robert Plant

 Raising Sand

 Singles

 `` When You Say Nothing at All ''

 `` Baby Now That I 've Found You ''

 `` Baby Mine ''

 `` The Lucky One ''

 `` Missing You ''

 `` Please Read the Letter ''

 `` Rich Woman ''

 Featured singles

 `` Teach Your Children ''

 `` Somewhere in the Vicinity of the Heart ''

 `` It 's Not Over ''

 `` Buy Me a Rose ''

 `` Whiskey Lullaby ''

 Related articles

 Discography

 Awards and nominations

 Alison Brown

 Robert Plant

 Viktor Krauss

 Up ! Close and Personal

 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Now_That_I%27ve_Found_You:_A_Collection&oldid=808197945 '' Categories :

 1995 compilation albums

 Alison Krauss & Union Station albums

 Rounder Records compilation albums

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 This page was last edited on 1 November 2017 , at 13 : 34 .

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Question: alison krauss now that i've found you album


Evolution of the eye - wikipedia

 Evolution of the eye

 Jump to : navigation , search Major stages in the evolution of the eye in vertebrates .

 The evolution of the eye is attractive to study , because the eye distinctively exemplifies an analogous organ found in many animal forms . Complex , image - forming eyes have evolved independently several times . The evolutionary geneticist Walter Gering holds a different opinion . According his theory , the genes engaged with photoreceptor cells ( so called Pax 6 genes ) appeared probably at once in the life history , at a very early stage of the evolution . Probably , the complex , image forming kinds of eyes are at least five : Chidaria - lens eye , complex eye ; Molluscs - lens eye , everse retina ; Annelids - lens eye , everse retina ; Arthropods - facet eye ; Vertebrate - lens eye , inverse retina

 Complex eyes appeared first within the few million years of the Cambrian explosion . From before the Cambrian , no evidence of eyes has survived , but diverse eyes are known from the Burgess shale of the Middle Cambrian , and from the slightly older Emu Bay Shale . Eyes are adapted to the various requirements of their owners . They vary in their visual acuity , the range of wavelengths they can detect , their sensitivity in low light , their ability to detect motion or to resolve objects , and whether they can discriminate colours .

 Contents

 ( hide )

 1 History of research

 2 Rate of evolution

 3 One origin or many ?

 4 Stages of eye evolution

 4.1 Early eyes

 4.2 Lens formation and diversification

 4.3 Other developments

 4.3. 1 Color vision

 4.3. 2 Polarization vision

 4.3. 3 Focusing mechanism

 4.3. 4 Location

 5 Evolutionary baggage

 6 Footnotes

 7 See also

 8 References

 9 Further reading

 10 External links

 History of research ( edit )

 The human eye , showing the iris

 In 1802 , philosopher William Paley called it a miracle of `` design '' . Charles Darwin himself wrote in his Origin of Species , that the evolution of the eye by natural selection seemed at first glance `` absurd in the highest possible degree '' . However , he went on that despite the difficulty in imagining it , its evolution was perfectly feasible :

 ... if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist , each grade being useful to its possessor , as is certainly the case ; if further , the eye ever varies and the variations be inherited , as is likewise certainly the case and if such variations should be useful to any animal under changing conditions of life , then the difficulty of believing that a perfect and complex eye could be formed by natural selection , though insuperable by our imagination , should not be considered as subversive of the theory .

 He suggested a stepwise evolution from `` an optic nerve merely coated with pigment , and without any other mechanism '' to `` a moderately high stage of perfection '' , and gave examples of existing intermediate steps . Darwin 's suggestions were soon shown to be correct , and current research is investigating the genetic mechanisms underlying eye development and evolution .

 Biologist D.E. Nilsson has independently theorized about four general stages in the evolution of a vertebrate eye from a patch of photoreceptors . Nilsson and S. Pelger estimated in a classical paper how many generations are needed to evolve a complex eye in vertebrates . Another researcher , G.C. Young , has used the fossil record to infer evolutionary conclusions , based on the structure of eye orbits and openings in fossilized skulls for blood vessels and nerves to go through . All this adds to the growing amount of evidence that supports Darwin 's theory .

 Rate of evolution ( edit )

 The first fossils of eyes found to date are from the lower Cambrian period ( about 540 million years ago ) . The lower Cambrian had a burst of apparently rapid evolution , called the `` Cambrian explosion '' . One of the many hypotheses for `` causes '' of the Cambrian explosion is the `` Light Switch '' theory of Andrew Parker : It holds that the evolution of eyes started an arms race that accelerated evolution . Before the Cambrian explosion , animals may have sensed light , but did not use it for fast locomotion or navigation by vision .

 The rate of eye evolution is difficult to estimate , because the fossil record , particularly of the lower Cambrian , is poor . How fast a circular patch of photoreceptor cells evolve into a fully functional vertebrate eye has been estimated based on rates of mutation , relative advantage to the organism , and natural selection . However , the time needed for each state was consistently overestimated and the generation time was set to one year , which is common in small animals . Even with these pessimistic values , the vertebrate eye would still evolve from a patch of photoreceptor cells in less than 364,000 years .

 One origin or many ? ( edit )

 Whether the eye evolved once or many times depends on the definition of an eye . All eyed animals share much of the genetic machinery for eye development . This suggests that the ancestor of eyed animals had some form of light - sensitive machinery -- even if it was not a dedicated optical organ . However , even photoreceptor cells may have evolved more than once from molecularly similar chemoreceptor cells . Probably , photoreceptor cells existed long before the Cambrian explosion . Higher - level similarities -- such as the use of the protein crystallin in the independently derived cephalopod and vertebrate lenses -- reflect the co-option of a more fundamental protein to a new function within the eye .

 A shared trait common to all light - sensitive organs are opsins . Opsins belong to a family of photo - sensitive proteins and fall into nine groups , which already existed in the urbilaterian , the last common ancestor of all bilateral symmetrical animals . Additionally , the genetic toolkit for positioning eyes is shared by all animals : The PAX6 gene controls where eyes develop in animals ranging from octopuses to mice and fruit flies . Such high - level genes are , by implication , much older than many of the structures that they control today ; they must originally have served a different purpose , before they were co-opted for eye development .

 Eyes and other sensory organs probably evolved before the brain : There is no need for an information - processing organ ( brain ) before there is information to process .

 Stages of eye evolution ( edit )

 The stigma ( 2 ) of the euglena hides a light - sensitive spot .

 The earliest predecessors of the eye were photoreceptor proteins that sense light , found even in unicellular organisms , called `` eyespots '' . Eyespots can only sense ambient brightness : they can distinguish light from dark , sufficient for photoperiodism and daily synchronization of circadian rhythms . They are insufficient for vision , as they can not distinguish shapes or determine the direction light is coming from . Eyespots are found in nearly all major animal groups , and are common among unicellular organisms , including euglena . The euglena 's eyespot , called a stigma , is located at its anterior end . It is a small splotch of red pigment which shades a collection of light sensitive crystals . Together with the leading flagellum , the eyespot allows the organism to move in response to light , often toward the light to assist in photosynthesis , and to predict day and night , the primary function of circadian rhythms . Visual pigments are located in the brains of more complex organisms , and are thought to have a role in synchronising spawning with lunar cycles . By detecting the subtle changes in night - time illumination , organisms could synchronise the release of sperm and eggs to maximise the probability of fertilisation .

 Vision itself relies on a basic biochemistry which is common to all eyes . However , how this biochemical toolkit is used to interpret an organism 's environment varies widely : eyes have a wide range of structures and forms , all of which have evolved quite late relative to the underlying proteins and molecules .

 At a cellular level , there appear to be two main `` designs '' of eyes , one possessed by the protostomes ( molluscs , annelid worms and arthropods ) , the other by the deuterostomes ( chordates and echinoderms ) .

 The functional unit of the eye is the photoreceptor cell , which contains the opsin proteins and responds to light by initiating a nerve impulse . The light sensitive opsins are borne on a hairy layer , to maximise the surface area . The nature of these `` hairs '' differs , with two basic forms underlying photoreceptor structure : microvilli and cilia . In the eyes of protostomes , they are microvilli : extensions or protrusions of the cellular membrane . But in the eyes of deuterostomes , they are derived from cilia , which are separate structures . However , outside the eyes an organism may use the other type of photoreceptor cells , for instance the clamworm Platynereis dumerilii uses microvilliar cells in the eyes but has additionally deep brain ciliary photoreceptor cells . The actual derivation may be more complicated , as some microvilli contain traces of cilia -- but other observations appear to support a fundamental difference between protostomes and deuterostomes . These considerations centre on the response of the cells to light -- some use sodium to cause the electric signal that will form a nerve impulse , and others use potassium ; further , protostomes on the whole construct a signal by allowing more sodium to pass through their cell walls , whereas deuterostomes allow less through .

 This suggests that when the two lineages diverged in the Precambrian , they had only very primitive light receptors , which developed into more complex eyes independently .

 Early eyes ( edit )

 The basic light - processing unit of eyes is the photoreceptor cell , a specialized cell containing two types of molecules in a membrane : the opsin , a light - sensitive protein , surrounding the chromophore , a pigment that distinguishes colors . Groups of such cells are termed `` eyespots '' , and have evolved independently somewhere between 40 and 65 times . These eyespots permit animals to gain only a very basic sense of the direction and intensity of light , but not enough to discriminate an object from its surroundings .

 Developing an optical system that can discriminate the direction of light to within a few degrees is apparently much more difficult , and only six of the thirty - some phyla possess such a system . However , these phyla account for 96 % of living species .

 The planarian has `` cup '' eyespots that can slightly distinguish light direction .

 These complex optical systems started out as the multicellular eyepatch gradually depressed into a cup , which first granted the ability to discriminate brightness in directions , then in finer and finer directions as the pit deepened . While flat eyepatches were ineffective at determining the direction of light , as a beam of light would activate exactly the same patch of photo - sensitive cells regardless of its direction , the `` cup '' shape of the pit eyes allowed limited directional differentiation by changing which cells the lights would hit depending upon the light 's angle . Pit eyes , which had arisen by the Cambrian period , were seen in ancient snails , and are found in some snails and other invertebrates living today , such as planaria . Planaria can slightly differentiate the direction and intensity of light because of their cup - shaped , heavily pigmented retina cells , which shield the light - sensitive cells from exposure in all directions except for the single opening for the light . However , this proto - eye is still much more useful for detecting the absence or presence of light than its direction ; this gradually changes as the eye 's pit deepens and the number of photoreceptive cells grows , allowing for increasingly precise visual information .

 When a photon is absorbed by the chromophore , a chemical reaction causes the photon 's energy to be transduced into electrical energy and relayed , in higher animals , to the nervous system . These photoreceptor cells form part of the retina , a thin layer of cells that relays visual information , including the light and day - length information needed by the circadian rhythm system , to the brain . However , some jellyfish , such as Cladonema , have elaborate eyes but no brain . Their eyes transmit a message directly to the muscles without the intermediate processing provided by a brain .

 During the Cambrian explosion , the development of the eye accelerated rapidly , with radical improvements in image - processing and detection of light direction .

 The primitive nautilus eye functions similarly to a pinhole camera .

 After the photosensitive cell region invaginated , there came a point when reducing the width of the light opening became more efficient at increasing visual resolution than continued deepening of the cup . By reducing the size of the opening , organisms achieved true imaging , allowing for fine directional sensing and even some shape - sensing . Eyes of this nature are currently found in the nautilus . Lacking a cornea or lens , they provide poor resolution and dim imaging , but are still , for the purpose of vision , a major improvement over the early eyepatches .

 Overgrowths of transparent cells prevented contamination and parasitic infestation . The chamber contents , now segregated , could slowly specialize into a transparent humour , for optimizations such as colour filtering , higher refractive index , blocking of ultraviolet radiation , or the ability to operate in and out of water . The layer may , in certain classes , be related to the moulting of the organism 's shell or skin . An example of this can be observed in Onychophorans where the cuticula of the shell continues to the cornea . The cornea is composed of either one or two cuticular layers depending on how recently the animal has moulted . Along with the lens and two humors , the cornea is responsible for converging light and aiding the focusing of it on the back of the retina . The cornea protects the eyeball while at the same time accounting for approximately 2 / 3 of the eye 's total refractive power .

 It is likely that a key reason eyes specialize in detecting a specific , narrow range of wavelengths on the electromagnetic spectrum -- the visible spectrum -- is because the earliest species to develop photosensitivity were aquatic , and only two specific wavelength ranges of electromagnetic radiation , blue and green visible light , can travel through water . This same light - filtering property of water also influenced the photosensitivity of plants .

 Lens formation and diversification ( edit )

 Light from a distant object and a near object being focused by changing the curvature of the lens

 In a lensless eye , the light emanating from a distant point hits the back of the eye with about the same size as the eye 's aperture . With the addition of a lens this incoming light is concentrated on a smaller surface area , without reducing the overall intensity of the stimulus . The focal length of an early lobopod with lens - containing simple eyes focused the image behind the retina , so while no part of the image could be brought into focus , the intensity of light allowed the organism to see in deeper ( and therefore darker ) waters . A subsequent increase of the lens 's refractive index probably resulted in an in - focus image being formed .

 The development of the lens in camera - type eyes probably followed a different trajectory . The transparent cells over a pinhole eye 's aperture split into two layers , with liquid in between . The liquid originally served as a circulatory fluid for oxygen , nutrients , wastes , and immune functions , allowing greater total thickness and higher mechanical protection . In addition , multiple interfaces between solids and liquids increase optical power , allowing wider viewing angles and greater imaging resolution . Again , the division of layers may have originated with the shedding of skin ; intracellular fluid may infill naturally depending on layer depth .

 Note that this optical layout has not been found , nor is it expected to be found . Fossilization rarely preserves soft tissues , and even if it did , the new humour would almost certainly close as the remains desiccated , or as sediment overburden forced the layers together , making the fossilized eye resemble the previous layout .

 Compound eye of Antarctic krill

 Vertebrate lenses are composed of adapted epithelial cells which have high concentrations of the protein crystallin . These crystallins belong to two major families , the α - crystallins and the βγ - crystallins . Both were categories of proteins originally used for other functions in organisms , but eventually were adapted for the sole purpose of vision in animal eyes . In the embryo , the lens is living tissue , but the cellular machinery is not transparent so must be removed before the organism can see . Removing the machinery means the lens is composed of dead cells , packed with crystallins . These crystallins are special because they have the unique characteristics required for transparency and function in the lens such as tight packing , resistance to crystallization , and extreme longevity , as they must survive for the entirety of the organism 's life . The refractive index gradient which makes the lens useful is caused by the radial shift in crystallin concentration in different parts of the lens , rather than by the specific type of protein : it is not the presence of crystallin , but the relative distribution of it , that renders the lens useful .

 It is biologically difficult to maintain a transparent layer of cells . Deposition of transparent , nonliving , material eased the need for nutrient supply and waste removal . Trilobites used calcite , a mineral which today is known to be used for vision only in a single species of brittle star . In other compound eyes and camera eyes , the material is crystallin . A gap between tissue layers naturally forms a biconvex shape , which is optically and mechanically ideal for substances of normal refractive index . A biconvex lens confers not only optical resolution , but aperture and low - light ability , as resolution is now decoupled from hole size -- which slowly increases again , free from the circulatory constraints .

 Independently , a transparent layer and a nontransparent layer may split forward from the lens : a separate cornea and iris . ( These may happen before or after crystal deposition , or not at all . ) Separation of the forward layer again forms a humour , the aqueous humour . This increases refractive power and again eases circulatory problems . Formation of a nontransparent ring allows more blood vessels , more circulation , and larger eye sizes . This flap around the perimeter of the lens also masks optical imperfections , which are more common at lens edges . The need to mask lens imperfections gradually increases with lens curvature and power , overall lens and eye size , and the resolution and aperture needs of the organism , driven by hunting or survival requirements . This type is now functionally identical to the eye of most vertebrates , including humans . Indeed , `` the basic pattern of all vertebrate eyes is similar . ''

 Other developments ( edit )

 Color vision ( edit )

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 Five classes of visual opsins are found in vertebrates . All but one of these developed prior to the divergence of Cyclostomata and fish . The five opsin classes are variously adapted depending on the light spectrum encountered . As light travels through water , longer wavelengths , such as reds and yellows , are absorbed more quickly than the shorter wavelengths of the greens and blues . This creates a gradient of light as the depth of water increases . The visual opsins in fish are more sensitive to the range of light in their habitat and depth . However , land environments do not vary in wavelength composition , so that the opsin sensitivities among land vertebrates does not vary much . This directly contributes to the significant presence of communication colors . Color vision gives distinct selective advantages , such as better recognition of predators , food , and mates . Indeed , it is thought that simple sensory - neural mechanisms may selectively control general behavior patterns , such as escape , foraging , and hiding . Many examples of wavelength - specific behaviors have been identified , in two primary groups : Below 450 nm , associated with direct light , and above 450 nm , associated with reflected light . As opsin molecules were tuned to detect different wavelengths of light , at some point color vision developed when the photoreceptor cells used differently tuned opsins . This may have happened at any of the early stages of the eye 's evolution , and may have disappeared and reevolved as organisms became predator or prey . Similarly , night and day vision emerged when photoreceptor cells differentiated into rods and cones , respectively .

 Further information : Evolution of color vision Polarization vision ( edit )

 As discussed earlier , the properties of light under water differ from those in air . One example of this is the polarization of light . Polarization is the organization of originally disordered light , from the sun , into linear arrangements . This occurs when light passes through slit like filters , as well as when passing into a new medium . Sensitivity to polarized light is especially useful for organisms whose habitats are located more than a few meters under water . In this environment , color vision is less dependable , and therefore a weaker selective factor . While most photoreceptors have the ability to distinguish partially polarized light , terrestrial vertebrates ' membranes are orientated perpendicularly , such that they are insensitive to polarized light . However , some fish can discern polarized light , demonstrating that they possess some linear photoreceptors . Additionally , cuttlefish are capable of perceiving the polarization of light with high visual fidelity , although they appear to lack any significant capacity for color differentiation . Like color vision , sensitivity to polarization can aid in an organism 's ability to differentiate surrounding objects and individuals . Because of the marginal reflective interference of polarized light , it is often used for orientation and navigation , as well as distinguishing concealed objects , such as disguised prey .

 Focusing mechanism ( edit )

 By utilizing the iris sphincter muscle , some species move the lens back and forth , some stretch the lens flatter . Another mechanism regulates focusing chemically and independently of these two , by controlling growth of the eye and maintaining focal length . In addition , the pupil shape can be used to predict the focal system being utilized . A slit pupil can indicate the common multifocal system , while a circular pupil usually specifies a monofocal system . When using a circular form , the pupil will constrict under bright light , increasing the focal length , and will dilate when dark in order to decrease the depth of focus . Note that a focusing method is not a requirement . As photographers know , focal errors increase as aperture increases . Thus , countless organisms with small eyes are active in direct sunlight and survive with no focus mechanism at all . As a species grows larger , or transitions to dimmer environments , a means of focusing need only appear gradually .

 Location ( edit )

 Prey generally have eyes on the sides of their head so to have a larger field of view , from which to avoid predators . Predators , however , have eyes in front of their head in order to have better depth perception . Flatfish are predators which lie on their side on the bottom , and have eyes placed asymmetrically on the same side of the head . A transitional fossil from the common symmetric position is Amphistium .

 Evolutionary baggage ( edit )

 Vertebrate Octopus Vertebrates and octopodes developed the camera eye independently . In the vertebrate version the nerve fibers pass in front of the retina , and there is a blind spot where the nerves pass through the retina . In the vertebrate example , 4 represents the blind spot , which is notably absent from the octopus eye . In both vertebrates and octopodes , 1 represents the retina , 2 represents the nerve fibers , and 3 represents the optic nerve . Main article : Evolutionary baggage

 The eyes of many animals record their evolutionary history in their contemporary anatomy . The vertebrate eye , for instance , is built `` backwards and upside down '' , requiring `` photons of light to travel through the cornea , lens , aqueous fluid , blood vessels , ganglion cells , amacrine cells , horizontal cells , and bipolar cells before they reach the light - sensitive rods and cones that transduce the light signal into neural impulses , which are then sent to the visual cortex at the back of the brain for processing into meaningful patterns . '' While such a construct has some drawbacks , it also allows the outer retina of the vertebrates to sustain higher metabolic activities as compared to the non-inverted design . It also allowed for the evolution of the choroid layer , including the retinal pigment epithelial ( RPE ) cells , which play an important role in protecting the photoreceptive cells from photo - oxidative damage .

 The camera eyes of cephalopods , in contrast , are constructed the `` right way out '' , with the nerves attached to the rear of the retina . This means that they do not have a blind spot . This difference may be accounted for by the origins of eyes ; in cephalopods they develop as an invagination of the head surface whereas in vertebrates they originate as an extension of the brain .

 Footnotes ( edit )

 Jump up ^ David Berlinski , an intelligent design proponent , questioned the basis of the calculations , and the author of the original paper refuted Berlinski 's criticism .

 Berlinski , David ( April 2001 ) . `` Commentary magazine '' .

 Nilsson , Dan - E. `` Beware of Pseudo-science : a response to David Berlinski 's attack on my calculation of how long it takes for an eye to evolve '' .

 `` Evolution of the Eye '' on PBS

 Jump up ^ The precise number varies from author to author .

 See also ( edit )

 Ocelloid

 References ( edit )

 Jump up ^ `` '' An important cue for understanding eye evolution is the distinction between different types of photoreceptor cells . Salvini - Plawen and Mayr ( 1977 ) noted a remarkable diversity of photoreceptor cell morphology across the animal kingdom , and suggested that photoreceptors evolved independently numerous times . '' - Land , M.F. and Nilsson , D. - E. , Animal Eyes ( 2 - nd ed . ) , Oxford University Press , Oxford ( 2012 ) , p. 7 .

 Jump up ^ `` '' About 65 % of genes expressed in the retina of the fruit fly are also active in the retina of the mouse '' - Glaeser G. , Paulus H.F. - The Evolution of the Eye , Springer ( 2015 ) , ch. 7 , Pax and homology : the third act in the history of evolution - p. 148

 Jump up ^ `` Glaeser G. , Paulus H.F. - The Evolution of the Eye , Springer ( 2015 ) , ch. 7 , Pax and homology : the third act in the history of evolution - p. 149

 Jump up ^ Lee , M.S.Y. ; Jago , J.B. ; Garcia - Bellido , D.C. ; Edgecombe , G.E. ; Gehling , J. G ; Paterson , J.R. ( 2011 ) . `` Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia '' . Nature . 474 : 631 -- 634 . doi : 10.1038 / nature10097 . PMID 21720369 .

 ^ Jump up to : Darwin , Charles ( 1859 ) . On the Origin of Species . London : John Murray .

 Jump up ^ Gehring WJ ( 2005 ) . `` New perspectives on eye development and the evolution of eyes and photoreceptors '' . J. Hered. 96 ( 3 ) : 171 -- 84 . doi : 10.1093 / jhered / esi027 . PMID 15653558 .

 Jump up ^ Nilsson , D. - E. ( 2013 ) . `` Eye evolution and its functional basis '' . Visual Neuroscience. 30 : 5 -- 20 . doi : 10.1017 / s0952523813000035 .

 ^ Jump up to : Nilsson , D. - E. ; Pelger , S. ( 1994 ) . `` A pessimistic estimate of the time required for an eye to evolve '' . Proceedings of the Royal Society B : Biological Sciences . 256 : 53 -- 58 . doi : 10.1098 / rspb. 1994.0048 . PMID 8008757 .

 Jump up ^ Young , G.C. ( 2008 ) . `` Early evolution of the vertebrate eye -- fossil evidence '' . Evo Edu Outreach. 1 : 427 -- 438 . doi : 10.1007 / s12052 - 008 - 0087 - y .

 Jump up ^ Parker , A.R. ( 2009 ) . `` On the origin of optics '' . Optics & Laser Technology . 43 ( 2 ) : 323 -- 329 . Bibcode : 2011OptLT ... 43 ... 323P . doi : 10.1016 / j. optlastec. 2008.12. 020 .

 Jump up ^ Parker , Andrew ( 2003 ) . In the Blink of an Eye : How Vision Sparked the Big Bang of Evolution . Cambridge , MA : Perseus Pub . ISBN 0 - 7382 - 0607 - 5 .

 ^ Jump up to : Nilsson , D-E ; Pelger S ( 1994 ) . `` A pessimistic estimate of the time required for an eye to evolve '' . Proceedings of the Royal Society B. 256 ( 1345 ) : 53 -- 58 . doi : 10.1098 / rspb. 1994.0048 . PMID 8008757 .

 Jump up ^ Nilsson , D.E. ( 1996 ) . `` Eye ancestry : old genes for new eyes '' . Current Biology . 6 ( 1 ) : 39 -- 42 . doi : 10.1016 / S0960 - 9822 ( 02 ) 00417 - 7 . PMID 8805210 .

 Jump up ^ Zinovieva , R. ; Piatigorsky , J. ; Tomarev , S.I. ( 1999 ) . `` O - Crystallin , arginine kinase and ferritin from the octopus lens '' . Biochimica et Biophysica Acta ( BBA ) - Protein Structure and Molecular Enzymology. 1431 ( 2 ) : 512 -- 517 . doi : 10.1016 / S0167 - 4838 ( 99 ) 00066 - 7 .

 ^ Jump up to : Scotland , R.W. ( 2010 ) . `` Deep homology : A view from systematics '' . BioEssays. 32 ( 5 ) : 438 -- 449 . doi : 10.1002 / bies. 200900175 . PMID 20394064 .

 Jump up ^ Ramirez , MD ; Pairett , AN ; Pankey , MS ; Serb , JM ; Speiser , DI ; Swafford , AJ ; Oakley , TH ( 26 October 2016 ) . `` The last common ancestor of most bilaterian animals possessed at least 9 opsins '' . Genome Biology and Evolution : evw248 . doi : 10.1093 / gbe / evw248 .

 Jump up ^ Yoshida , Masa - aki ; Yura , Kei ; Ogura , Atsushi ( 5 March 2014 ) . `` Cephalopod eye evolution was modulated by the acquisition of Pax - 6 splicing variants '' . Scientific Reports . nature.com. 4 . Bibcode : 2014NatSR ... 4E4256Y . doi : 10.1038 / srep04256 . PMC 3942700 . PMID 24594543 . Retrieved June 30 , 2014 .

 Jump up ^ Halder , G. ; Callaerts , P. ; Gehring , W.J. ( 1995 ) . `` New perspectives on eye evolution '' . Current Opinion in Genetics & Development . 5 ( 5 ) : 602 -- 609 . doi : 10.1016 / 0959 - 437X ( 95 ) 80029 - 8 . PMID 8664548 .

 Jump up ^ Halder , G. ; Callaerts , P. ; Gehring , W. ( 1995 ) . `` Induction of ectopic eyes by targeted expression of the eyeless gene in Drosophila '' . Science . 267 ( 5205 ) : 1788 -- 92 . Bibcode : 1995Sci ... 267.1788 H . doi : 10.1126 / science. 7892602 . PMID 7892602 .

 Jump up ^ Tomarev , S.I. ; Callaerts , P. ; Kos , L. ; Zinovieva , R. ; Halder , G. ; Gehring , W. ; Piatigorsky , J. ( 1997 ) . `` Squid Pax - 6 and eye development '' . Proceedings of the National Academy of Sciences of the United States of America . 94 ( 6 ) : 2421 -- 2426 . Bibcode : 1997PNAS ... 94.2421 T . doi : 10.1073 / pnas. 94.6. 2421 . PMC 20103 . PMID 9122210 .

 ^ Jump up to : Gehring , W.J. ( 13 January 2005 ) . `` New Perspectives on Eye Development and the Evolution of Eyes and Photoreceptors '' ( Full text ) . Journal of Heredity . Oxford Journals. 96 ( 3 ) : 171 -- 184 . doi : 10.1093 / jhered / esi027 . PMID 15653558 . Retrieved 2008 - 04 - 26 .

 ^ Jump up to : MF Land ; RD Fernald ( 1992 ) . `` The Evolution of Eyes '' . Annual Review of Neuroscience. 15 : 1 -- 29 . doi : 10.1146 / annurev. ne. 15.030192. 000245 . PMID 1575438 .

 Jump up ^ Autrum , H ( 1979 ) . `` Introduction '' . In H. Autrum . Comparative Physiology and Evolution of Vision in Invertebrates - A : Invertebrate Photoreceptors . Handbook of Sensory Physiology . VII / 6A . New York : Springer - Verlag . pp. 6 -- 9 . ISBN 3 - 540 - 08837 - 7 .

 Jump up ^ Arendt , D. ; Tessmar - Raible , K. ; Snyman , H. ; Dorresteijn , A.W. ; Wittbrodt , J. ( 29 October 2004 ) . `` Ciliary Photoreceptors with a Vertebrate - Type Opsin in an Invertebrate Brain '' . Science . 306 ( 5697 ) : 869 -- 871 . doi : 10.1126 / science. 1099955 . PMID 15514158 .

 Jump up ^ Eye - Evolution ? Archived 15 September 2012 at the Wayback Machine .

 ^ Jump up to : Fernald , Russell D. ( 2001 ) . The Evolution of Eyes : How Do Eyes Capture Photons ? Karger Gazette 64 : `` The Eye in Focus '' .

 Jump up ^ Conway - Morris , S. ( 1998 ) . The Crucible of Creation . Oxford : Oxford University Press .

 Jump up ^ Dawkins , Richard ( 1986 ) . The Blind Watchmaker .

 ^ Jump up to : Schoenemann , B. ; Liu , J.N. ; Shu , D.G. ; Han , J. ; Zhang , Z.F. ( 2008 ) . `` A miniscule optimized visual system in the Lower Cambrian '' . Lethaia. 42 ( 3 ) : 265 -- 273 . doi : 10.1111 / j. 1502 - 3931.2008. 00138. x .

 Jump up ^ Ali , M.A. and M.A. Klyne. 1985 . Vision in vertebrates . New York : Plenum Press

 Jump up ^ Fernald , Russell D. ( 2001 ) . The Evolution of Eyes : Why Do We See What We See ? Karger Gazette 64 : `` The Eye in Focus '' .

 Jump up ^ Fernald , Russell D. ( 1998 ) . Aquatic Adaptations in Fish Eyes . New York , Springer .

 Jump up ^ Fernald RD ( 1997 ) . `` The evolution of eyes '' . Brain Behav . Evol. 50 ( 4 ) : 253 -- 9 . doi : 10.1159 / 000113339 . PMID 9310200 .

 ^ Jump up to : Slingsby , C. ; Wistow , G.J. ; Clark , A.R. ( 2013 ) . `` Evolution of crystallins for a role in the vertebrate eye lens '' . Protein Science . 22 : 367 -- 380 . doi : 10.1002 / pro. 2229 .

 Jump up ^ Fernald , Russell D. ( 2001 ) . The Evolution of Eyes : Where Do Lenses Come From ? Karger Gazette 64 : `` The Eye in Focus '' .

 Jump up ^ Burgess , Daniel S. ( 2001 ) . Brittle Star Features Calcite Lenses , Photonics Spectra

 Jump up ^ Ali , Mohamed Ather ; Klyne , M.A. ( 1985 ) . Vision in Vertebrates . New York : Plenum Press . p. 1 . ISBN 0 - 306 - 42065 - 1 .

 ^ Jump up to : Osorio , D ; Vorobyev , M ( 2005 ) . `` Photo - receptor spectral sensitivities in terrestrial animals : adaptations for luminescence and color vision '' . Proc. R. Soc . B .

 Jump up ^ Gühmann , Martin ; Jia , Huiyong ; Randel , Nadine ; Verasztó , Csaba ; Bezares - Calderón , Luis A. ; Michiels , Nico K. ; Yokoyama , Shozo ; Jékely , Gáspár ( August 2015 ) . `` Spectral Tuning of Phototaxis by a Go - Opsin in the Rhabdomeric Eyes of Platynereis '' . Current Biology . 25 ( 17 ) : 2265 -- 2271 . doi : 10.1016 / j. cub. 2015.07. 017 . PMID 26255845 .

 Jump up ^ Menzel , Randolf ( 1979 ) . `` Spectral Sensitivity and Color Vision in Invertebrates '' . In H. Autrum . Comparative Physiology and Evolution of Vision in Invertebrates - A : Invertebrate Photo - receptors . Handbook of Sensory Physiology . VII / 6A . New York : Springer - Verlag . pp. 504 -- 506 ; 551 -- 558 . ISBN 3 - 540 - 08837 - 7 .

 ^ Jump up to : Cronin , T ; Shashar , N ; Caldwell , R ; Marshall , J ; Cheroske , A ; Chiou , T ( 2003 ) . `` Polarization vision and its role in biological signaling '' . Integr . Comp. Biol .

 Jump up ^ Mäthger , Lydia M. ; Barbosa , Alexandra ; Miner , Simon ; Hanlon , Roger T. ( 2006 - 05 - 01 ) . `` Color blindness and contrast perception in cuttlefish ( Sepia officinalis ) determined by a visual sensorimotor assay '' . Vision Research . 46 ( 11 ) : 1746 -- 1753 . doi : 10.1016 / j. visres. 2005.09. 035 . PMID 16376404 .

 Jump up ^ Malstrom , T ; Kroger , R ( 2006 ) . `` pupil shape and lens optics in the eyes of terrestrial vertebrates '' . The Journal of Experimental Biology .

 Jump up ^ `` Carnivores '' . U.S. Department of the Interior , Bureau of Land Management . 2009 - 12 - 14 . Retrieved 2011 - 03 - 28 .

 Jump up ^ Boroditsky , Lera ( 1999 - 06 - 24 ) . `` Light & Eyes : Lecture Notes '' . Lecture Notes . Stanford . Retrieved 11 May 2010 .

 Jump up ^ Dr. Michael Shermer , as quoted by Christopher Hitchens in his book `` God is Not Great '' ( pg. 82 )

 Jump up ^ Reichenbach A , Bringmann A. ( 2010 ) . Müller cells in the healthy and diseased retina . New York : Springer . pp 15 - 20 .

 Jump up ^ http://www.photobiology.info/Rozanowska.html

 Jump up ^ Diagrammatic representation of disc shedding and phagosome retrieval into the pigment epithelial cell. ( 1 )

 Jump up ^ Serb , Jeanne M. ; Eernisse , Douglas J. ( 2008 - 09 - 25 ) . `` Charting Evolution 's Trajectory : Using Molluscan Eye Diversity to Understand Parallel and Convergent Evolution '' . Evolution : Education and Outreach. 1 ( 4 ) : 439 -- 447 . doi : 10.1007 / s12052 - 008 - 0084 - 1 . ISSN 1936 - 6426 .

 Further reading ( edit )

 Lamb TD , Collin SP , Pugh EN ( December 2007 ) . `` Evolution of the vertebrate eye : opsins , photoreceptors , retina and eye cup '' . Nat. Rev. Neurosci. 8 ( 12 ) : 960 -- 76 . doi : 10.1038 / nrn2283 . PMC 3143066 . PMID 18026166 . Illustration . Review

 Lamb , TD ( 2011 ) . `` Evolution of the Eye '' ( PDF ) . Scientific American . 305 : 64 -- 69 . doi : 10.1038 / scientificamerican0711 - 64 .

 Land , Michael F. ; Nilsson , Dan - Eric ( 2012 ) . `` The origin of vision '' . Animal Eyes ( 2 ed . ) . Oxford : Oxford University Press . pp. 1 -- 22 . ISBN 978 - 0199581146 .

 Journal Evolution : Education and Outreach Volume 1 , Number 4 / October 2008 . Special Issue : The Evolution of Eyes . 26 articles , free access .

 Ivan R. Schwab ( 2012 ) . Evolution 's Witness : How Eyes Evolved . New York : Oxford University Press . ISBN 9780195369748 .

 Hayakawa S , Takaku Y , Hwang JS , Horiguchi T , Suga H , Gehring W , et al. ( 2015 ) . `` Function and evolutionary origin of unicellular camera - type eye structure '' . PLoS ONE . 10 ( 3 ) : e0118415 . Bibcode : 2015PLoSO ... 1018415H . doi : 10.1371 / journal. pone. 0118415 . PMC 4348419 . PMID 25734540 .

 Greuet , C ( 1968 ) . `` Organisation ultrastructurale de l'ocelle de deux Peridiniens Warnowiidae , Erythropsis pavillardi Kofoid et Swezy et Warnowia pulchra Schiller '' . Protistologica. 4 : 209 -- 230 .

 Gregory S. Gavelis , Shiho Hayakawa , Richard A. White III , Takashi Gojobori , Curtis A. Suttle , Patrick J. Keeling , Brian S. Leander ( 2015 ) . `` Eye - like ocelloids are built from different endosymbiotically acquired components '' . Nature . 523 : 204 -- 7 . Bibcode : 2015Natur. 523 ... 204G . doi : 10.1038 / nature14593 . PMID 26131935 . CS1 maint : Uses authors parameter ( link )

 Oakley , Todd H. ; Speiser , Daniel I. ( 2015 ) . `` How Complexity Originates : The Evolution of Animal Eyes '' . Annual Review of Ecology , Evolution , and Systematics. 46 : 237 -- 260 . doi : 10.1146 / annurev - ecolsys - 110512 - 135907 .

 Ed Young ; photographs by David Liittschwager ( February 2016 ) . `` Inside the Eye : Nature 's Most Exquisite Creation '' . National Geographic . 229 ( 2 ) : 30 -- 57 .

 External links ( edit )

 `` Evolution of the Eye '' . WGBH Educational Foundation and Clear Blue Sky Productions . PBS . 2001 .

 Creationism Disproved ? Video from the National Center for Science Education on the evolution of the eye

 Evolution : Education and Outreach Special Issue : Evolution and Eyes volume 1 , number 4 , October 2008 , pages 351 - 559 . ISSN 1936 - 6426 ( Print ) 1936 - 6434 ( Online )

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Question: what is the first step in the evolution of the eye