Bio 2 Lecture 20

transition from dinosaurs to birds

key translational fossils with both dinosaur and avian features (with faint impressions of feathers)

class aves → diversity

26 orders → 166 families → 9600 species

beak shape and size predicts feeding ecology

class aves

birds have many characteristics that reveal reptilian ancestry → share air sack (septate) lungs

air sacs: efficient breathing

reduction of organs: single ovary, no urinary bladder

feathers: modified scales keep birds warm and enable flight

lightweight skeleton: thin, hollow, honeycombed

comparative biology of breathing

air sacs produce unidirectional flow where air enters and exits at the same rate, contasts with lungs of other tetrapods such as mammals where they have tidal ventilation

mammals

appeared about 225 mya, evolved from amniote ancestors earlier than dinosaurs, flourished after extinction of dinosaurs

range of sizes and body forms unmatched

mammals → important characteristics

hair and mammary glands that secrete milk

teeth shape and size predicts feeding ecology

vertebrates with specialized teeth

enlarged skull

chewing jaws

some but not all mammals have

horns (bony outgrowth of skull surrounded by keratin) and antlers (entirely of bone)

mammals → ruminants stomach

some but not all mammals digest plants using symbiotic bacterias

subclass prototheria → order monotremata

platypus and echidnas

lay eggs, lack placenta, poorly developed nipples

subclass theria → clase metatheria

7 orders

once widespread, now mostly confined to australia

opossum found in north america

very undeveloped young must make it to marsupium to finish development

subclass theria → clade eutheria

placental mammals: long-lived complex placenta with prolonged gestation

mammals → primates

primarily tree-dwelling species that evolved about 85 mya

defining characteristics:

grasping hands with opposable thumbs

large brain

some digits have flat nails (no claws)

complex social behavior and well-developed parental care

primates (2 groups)

stepsirrhi and haplorrhini

primates | strepsirrhini

bush babies, lemurs, loris

wet noses, no fur at tip, generally nocturnal and smaller-brained

primates → arthropoidea

“simians”

new world monkeys, old world monkeys, and apes

(dry noses, fully furred noses)

primates → haplorrhini

tarsiers: small, nocturnal, and insectivorus

primates → new world monkeys

5 families of primates found in Central and South America

distinction is nose (flat, narrow, and side facing nostrils)

prehensile tails for grasping, holding

primates → old world monkeys

native to africa and asia

most have tails: non-prehensile

differ from apes by dentition shape

many omnivorous

primates → hominoids

gibbons, gorillas, orangutans, chimpanzees, and humans

no tails, brachiation (swinging movement in trees), usually larger

family hylobatidae: lesser apes or gibbons

family hominidae: greater apes

all hominoids share a

common ancestor

subfamily ponginae: orangutans

subfamily homininae: tribe gorillini (gorillaas)

tribe panini (chimpanzees)

tribe hominini: humans and their ancestors

primates → genomic similarity

human and chimpanzee genome comparisons

differ by only 1.23% → 10 times less than mouse and rat genome