mammals and primate evo

Question 1

What defines a mammal

Answer 1

Mammals and their immediate ancestors are synapsids
First mammals appeared in the triassic, over 200 million years ago
Modern mammals consist of three lineages; monotremes, marsupials, and placental mammals

Question 2

Features of mammals

Answer 2

1)Hair: Follicles in the dermis; shaft made of keratin
For insulation, camouflage, defense, and sensory (whiskers) even whales have hair/hair follicles
2) mammary glands, females produce milk for offspring
3)Endothermy-body temp internally regulated (homeothermic with exceptions) Fat and fur provide insulation
4)Placenta(in most)-organ serves as provisional lungs, intestines, and kidneys of the fetus without mixing maternal and fetal blood (not present in monotremes or marsupials) placenta is a modification of a membrane of the amniotic egg
5) Specialized teeth; carnivore- canines herbivore-premolars and molars omnivores-molars, canines premolars and incisors
6)Hooves and horns, are all derived from keratine. Horns have a core bone surrounded by a sheath of certain, don’t shed. Antlers, made of bone and shed annually. Rhino horns are made from certain, are not attached to skull.

Question 3

Amniotic egg shift to placenta

Answer 3

Amnion remains unchanged,
yolk sac greatly reduced
allantois contributes to the umbilical cord
chorion forms the placenta

Question 4

Are saber-tooth designs homology or analogy?

Answer 4

Canines in mammals are homologous, but the saber tooth configuration is a result of convergent evolution

Question 5

homoplasy

Answer 5

convergent evolution

Question 6

homology

Answer 6

synapomorphy(evolved once)

Question 7

Marsupials (1 order)

Answer 7

-pouched mammals
-brief gestation; no implantation of the embryo in the uterus
-offspring live and feed in pouch
ex)kangaroos, koalas, opossums

Question 7

Monotremes(1order)

Answer 7

-Lay shelled eggs; young drink milk but do not suckle
-Represented by echidnas and the platypus

Question 8

Primates

Answer 8

1) Grasping fingers and toes; most with an opposable first digit; most with nails
2)binocular vision (eyes in front of the head) is good for depth perception

Question 8

Placental mammals (17 orders)

Answer 8

-long gestation period during which the embryo remains attached to the mother’s placenta to develop
Young suckle following birth

Question 9

Groups of primates

Answer 9

1)Prosimians- Primarily nocturnal;color blind (lemus, tarsiets ect)
2)anthropoids: virtual, color vision, larger brain
-monkeys-most have tails,
-Apes, no tail, gibbons, humans, gorillas chimpanzees

Question 10

Prosimians

Answer 10

primate group
1)Prosimians- Primarily nocturnal;color blind (lemus, tarsiets ect)

Question 11

anthropoids:

Answer 11

Primate group
anthropoids: virtual, color vision, larger brain
-monkeys-most have tails,
-Apes, no tail, gibbons, humans, gorillas chimpanzees
Chimp genome is 99% identical to humans

Question 12

Hominins

Answer 12

Species more closely related to humans than chimps
Brain size:
-Early hominins had chimp-sized brains,
-Brain size increased considerably with the genus homo
Bipedalism:
-4mya, preceded larger brain size 2mya

Question 13

Bipedalism; comparing apes with hominins

Answer 13

Chimps: Skull attaches posteriorly(back of skull), spine slightly curved, arms longer than legs used for walking, long, narrow pelvis, femur angled out
Hominin: skull attaches inferiorly(middle of skull), s s-shaped spine, arms shorter than legs, bowl-shaped pelvis, femur angled in