Vertebrates - Mammals

egan lecture 23

What are synapsids?

amniotes that include mammals

What did the jaw joint formed between denture and squamosal bones become?

incorporated into the middle ear, it transmit sounds from the ear drum to the middle ear

What did early non-mammalian synapsids have?

lacked hair

sprawling gait

laid eggs

What are derived characters of mammals? (8 of them)

1. mammary glands

2. hair and fat layer for insulation

3. kidneys

4. endothermy and high metabolic rate

5. efficient respiratory and circulatory systems

6. large brain-to-body size ratio

7. extensive parental care

8. modified teeth for shearing, crushing, or grinding

Where did mammals radiate time-wise?

after cretaceous loss of dinosaurs, pterosaurs, and marine reptiles

What three major lineages of mammals remain today?

monotremes (egg-laying)

marsupials (pouch)

eutherians (placental)

What are monotremes?

a small group of egg-laying mammals found only in Australia and New Guinea

What do females and babies do in monotremes?

Females secrete milk from glands on bellies; babies suck milk from their fur

What derived characters are shared between marsupials and eutherians?

higher metabolic rates

nipples to provide milk

birth of live young

embryonic development in the uterus

placenta for nutrient transfer form mother to embryo

How did the placenta evolve?

From fish to reptiles and birds to mammals with the amnion, chorion, and allantois of the amniotic egg and the yolk sac from fish

Compared to marsupials eutherians have:

more complex placenta and longer pregnancies

Placental mammals occupy what?

a larger morphospace and are taxonomically more diverse than marsupials

What are some primate characteristics?

Big toes and relatively moveable thumbs and enable feet/hands to grasp branches

fully opposable thumbs

enhanced depth perception and eye-hand coordination

What are the three groups of living primates?

lemurs, tarsiers, and athropoids

What are the closest living relatives to humans?

chimpanzee and bonobo, as hominid lineage diverged from chimpanzees ~7 MYA

What do apes include? (blank and four genera)

gibbons

pongo (orangutans)

gorilla (gorillas)

pan (chimpanzees and bonobos)

homo (humans)

What characteristics do other apes have? (8)

1. have arms longer than legs

2. walk upright for short distances

3. feet-like hands

4. highly social

5. sexual dimorphism (size)

6. use tools

7. hunt cooperatively

8. may have rudimentary “theory of mind” — ability to infer intentions and emotions of others

What characters distinguish humans from other apes?

upright posture and bipedal locomotion

larger brains capable of language, symbolic thought, and artistic expression

production and use of tools

reduced jawbones and jaw muscles

shorter digestive tract

How have humans skeletons evolved to support a bipedal life-style?

upright posture and fully bipedal locomotion

differing pelvis and lumbar region shape

foramen magnum shifted forward

modified feet for running

What derived characters for human hands?

shorter fingers with straighter phalanges

longer, more opposable thumbs

link to bipedalism

What derived characters for brain size?

human brain is 3x the size of other primate brains

5x relative size of most mammalian brains

When did Homo sapiens rise and are the single living species of?

200,000 years ago and hominin

What derived traits did early hominins share with humans?

reduced canine teeth

relatively flat faces

increasingly upright and bipedal

placement of foramen magnum underneath the skull

what are australopiths?

a paraphyletic assemblage of hominids that lived 4-2 million years ago

Where were australopiths geographically?

in central, eastern, and southern Africa

What is the earliest homo fossil?

homo habilis 2.4-1.6 mya

What did homo Habilis have?

shorter jaws and larger brains

What did homo ergaster have?

long, slender legs with hip joins well adapted for long-distance walking

teeth were smaller than australopiths, adapted for eating softer foods

What did neanderthals have?

thick-boned with a larger brain than modern humans

buried dead and made tools from stone and wood

What was the first homonin to migrate out of Africa?

Homo erectus at least 1.8 mya

When did human and neanderthal lineages diverge?

600,000 years ago

What features do humans fundamentally share with other organismal groups?

inheritance based on nucleic acids

genetic code (central dogma)

accumulation of other key traits through evolutionary time

When did Homo sapiens appear?

150,000-250,000 years ago in Africa

What did mitochondrial DNA indicate?

humans are closely related to neanderthals

deepest branches are from African population

When did mammalian lineages originate?

210 million years ago

When did new world monkeys rise?

~25 million years ago

When did apes arise and diverge from old world monkeys?

~35 mya, ~25-30 mya

When did Homo sapiens arise?

200,000 years ago