Lecture #34 - Mammals/Primates

250 million years ago

Mammals evolved from therapsids

Important characteristics of mammals

a.) Specialized teeth

b.) Mammary glands/Milk for offspring

c.) Hair and skin made from alpha-keratin

d.) Four-chambered heart

e.) Have a diaphragm

f.) Warm-blooded/Endothermic

g.) Neocortex region of brain

h.) Sweat glands

i.) Three middle ear bones used in hearing

Alpha - Keratin Protein

Found in all vertebrates. Makes hair, horns, nails, claws, and hooves in mammals. Non digestible

Nocturnal Bottleneck Hypothesis

Placental mammals were largely nocturnal starting with their origin 250 million years ago until the K-T extinction 60 million years ago

Nocturnal Adaptations in Mammals

a.) Acute hearing and smell

b.) Large Ears

c.) Whiskers

d.) Limited color vision

e.) No photolyase enzyme activity in placental mammals

f.) Brown Fat

g.) Fur

Diurnal

Active during day, sleep at night

Nocturnal

Activity at night, sleep during day

Crepuscular

Active at dawn and dusk

Vespertine

Active at dusk

Matutinal

Active at dawn

Cathemerality

Organism is active throughout the 24 - hour cycle. Also called polyphasic

Monotremes

Platypuses and echidnas. The male platypus has leg spurs that produces a mild venom/

Unique Features

Only mammals that lay eggs. Females produce milk but have no nipples

Cloaca

One opening for digestive, urinary, and reproductive tracts, like birds and reptiles

Marsupials

Opossum, kangaroo, koala, etc. Great Diversity is found in Australis, though they are also found in Australasia and in North, Central, and South America. Fossil diversity in greatest in Asia

Unique Features

In many species, young complete development in a pouch (marsupium). Different nipple size as offspring grow

Eutherian

Have placenta. Most living species of mammals. Very successful and diverse group

Unique Features

Placenta connects female to fetus. Three separate openings for digestion, urine, and reproduction

Corpus Callosum

In the brain that allows the right and left sides to communicate

Why do humans study rats an mice?

Because they are closest living relatives to the primates

Rodenta

Mice, rats, beavers, squirrels, prairie dogs, other gnawing mammals

What is specific about their teeth?

Front top and bottom teeth (incisors) keep growing

Chiroptera

Bats. Most species insect or fruit eaters (only three species of vampires).

Megachiroptera

Large, mostly diurnal/crepuscular. Good eyesight during day. Make loud calls. Must eat fruit or nectar

Microchiroptera

Small, mostly nocturnal. Use echolocation to find food at night. Can not make loud noises

Bats as disease reservoirs

Bats can carry rabies

White - Noise Syndrome

A fungal infection that dehydrates hibernating bats, causing them to wake too early in search of water and food, and they die

Soricomorpha

Shrews and mols. Includes smallest mammals with the highest metabolic rates.

Primates

About 500 - 600 species

Cetaritiodactyla

Even - toed hoofed mammals. Whales, hippos, deer, giraffe, cows, pigs, bison

Family Cervidae

Have antlers (deer, elk, moose): Antlers are bone, always shed. Velvet is hair/skin with blood supply to help bone grow. Only males have antlers, except for reindeer

Family Bovidae

Have Horns (Cows, buffalo, sheep, goat, antelope, gazelle): Bony cove with keratin sheath an outside, never shed. All males have horns and often females

Foregut Fermentation

Multi - chambers stomach (where bacteria digest food) is found before the small intestine (where nutrients are absorbed). Efficient system found in cows and other ruminants

Hindgut Fermentation

Fermentation chamber (caecum or appendix) is found after small intestine absorbs nutrients. Not as efficient. Found in horses, elephants, koala, humans, rabbits

Coprophagy

Send food through digestive system twice

Perissodactyla

Odd - toed hoofed mammals. Horses, tapirs, rhinoceros. Only about 17 total species

Carnivora

Dogs, cats, bears, seals, racoons, etc. Specialized shearing teeth called carnassial evolved in different groups, often from different sets of starting teeth

Arboreal

Adapted for living in the trees

Primate characteristics

a.) Big toe separated from other toes, except in humans

b.) Thumb is separate from fingers

c.) Very good 3D vision

d.) Large brains and short jaws

e.) Flat nails (fingernails) on fingers and toes. No claws

Prosimians

Lemurs, lorises, pottos, tarsiers of Asia, Africa, and Madagascar, Old World. Build nests for sleeping and reproduction

Anthropoids

Monkeys, apes, and humans both New and Old Worlds

New World Monkeys

All species are arboreal. Nostrils open to the side. Do not nest> May have prehensile tail

Old World Monkeys

Include arboreal and terrestrial species. Lack prehensile tails. Nostrils open downward. Do not nest

Ape

Arboreal and terrestrial. Old World. No tails. Nostrils open downward. Most build nests for sleeping only, except gibbons that do not make nests of any kind