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Flashcards in Lecture 29 Deck (22):

What are the defining features of vertebrates?

-vertebrae (backbone) forms around notochord -internal and elaborate skeleton (cartilage or bone) -defined head with braincase (skull) and sensory organ


 When did legs and jaws evolve in vertebrates?



What did the jaws evolve from and when?

-jaws derived from gill arches of chordates -earliest jawed fishes -late Silurian (420Mya) -some had dental armour=placoderm t-he gill arches move forward= first jaws, after that evolution of teeth


What did the first legs evolve from?

-most bony fishes have fins made of long rays of bone (ray finned fishes -some fishes developed more substantial bones in the fins (lobe-finned fishes) eg. lungfish=can breathe air


Who were the first Tetrapods? (able to walk animals)

-class Amphibia -about 350 Mya some of the lobe-finned fishes, living in shallow lagoons, developed these bones to be able ˇwalkˇ(paddle in shallow water) -had both gills and lungs (lungfish) -still needed water -had unusual limbs (eight digits!)


What are the characteristics of the class reptiles (vertebrae class)?

-tetrapod vertebrates -evolved from advanced reptile-like amphibians -adapted to life on dry land -many extinct groups (dinosaurs, pterosaurs etc.) -modern reptiles inhabit all continents except Antarctica key features: -have scutes or scales -"cold-blodded" -most lay eggs -no aquatic larval stage -could do without constant access to water= the major advance in reptiles -need to warm up to move


When did the major groups of tetrapods appear? (amphibians, reptiles,mammals, dinosaurs and crocodiles, birds)

-Amphibians: 350Mya -Reptiles: 330Mya -Mammals: 190Mya (mammals lineage-mammal-like reptiles=320Mya) -Dinosaurs and crocodiles= 230Mya (after Permian extinction) -Birds= 150Mya


What lineage do the dinosaurs come from?

-same as crocodiles (archosaurs!) -but walked upright!


What is the origin of birds?

-one group of small dinosaurs= dromaeosaurs -discovered in 1861 Germany= fossil of that with feathers and wings= first evidence for evolutionary origin of birds from dinosaurs -birds are part of archosaurs -archaeopterx= what the fossil was named


How did mammals evolve?

-first mammal-like reptiles =320Mya -at first very reptile-like -many were large and carnivorous(powerful jaws) -smaller mammal like reptiles evolved (possibly with fur) -upright stance(legs tucked under body) eg. Thrinaxodon


What did it mean for mammals the change of stance?

-hip joints and upper limb bones changed in mammals and dinosaurs enabled quicker locomotion -fish move their bodies from side to side when they swim -sprawling animals like crocodiles and lizards do the same -the change =mammals move their back half of body forward and back (bend in a different plane) -dolphins and whales-mammals so move in that way too


How did the jaw evolve in mammals?

-mammal-like reptiles became more mammal-like -jaw articulation changed ---reptiles=quadrate and articular ---mammals=squamosal and dentary -cynognathus had two joints -jaw bones become ear bones


What are the characteristics of the class Mammalia?

-terrestrial, aquatic, flying, subterrean -about 5000 species -key features: ---fur ---warm-blooded ---milk ---3 inner ear bones -split into three sub-classes --Prototheria (platypus, echidna) --Metatheria (marsupials) --Eutheria (placental mammals)


What are the characteristics of the Mammalia subclass Eutheria?

-prolonged gestation period -fed internally via a placenta -massive range of body size (2g to 200 000 000g) -about 20 orders (inculding primates) -some unexpected relationships -some unexpected relationships between mammals discovered by DNA analysis elephants and dugongs to golden moles!


What are the characteristics of the order Primates?

-fourth largest order of mammals (after rodents,bats and insectivores) -includes great apes, humans - more than 250 species -most arboreal (live in trees)


What does it mean that the mammals are plantigrade?

-most mammals walk on the tips of the feet (on their toes)=digitigrade -primates walk on their entire feet, right up to the heel= plantigrade -other plantigrade animals= bears, hedgehogs


What are the advantages of primates having grasping digits?

-primates have prehensile (grabbing) digits and opposable thumbs (tail can also be considered a digit) -adaptation fro arboreal existence -important in evolution of tool use


What are the advantages of primates having binocular vision?

-forward facing eyes -often enormous -increased visual sense (including colour vision) at the expense of sense of smell -adaptation for nocturnal existence, judging distances


What are the advantages of primates having increased brain size?

-particularly in great apes and humans -visual and locomotory areas greatly enlarged


What are the advantages of primates having the shoulder anatomy they have?

-a well-develop clavicle (collar bone) -very flexible rotating shoulder joint -good for movement in trees


What are the advantages of primates having upright posture?

-most primates can sit upright -some can walk short distances on hind legs -humans do it habitually


What are the 6 key features of primates?

1. grasping digits 2. plantigrade 3.binocular vision 4.increased brain size 5. very flexible rotating shoulder joint 6.upright posture