Chapter 20: Mammals

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Class Mammalia

Class Mammalia

• Hair

• Mammary glands to nourish newborns

• Large brain with neocortex

• Diaphragm

• Good sense of smell

• Most are placental

• Specialized teeth

• Most have an upright gait

6,399 living species of mammals

Diverse size, shapes, forms, and functions

Range from 2 grams hog nosed bats to 170 metric ton blue whales \n many are endangered

have evolved features that support a high metabolic rate, have turbinate bones, strong jaws, heterodont teeth for different foods, secondary palate to allow breathing while suckling, loss of lumbar ribs for flexibility and diaphragm

Hair

evolved in a mammalian common ancestor, adapted for concealment, waterproofing, buoyancy, signaling, sensory function, and thermal insulation, some have evolved to have less hair like whales and humans

Mammary Glands

glands that produce a “milk” or substance that provides nutrients to babies, active in women

Neocortex

complex brain structure found in mammals that deals with sensory perception, emotions, and cognition

Diaphragm

Muscle found in mammals that separates the thoracic cavity and abdominal cavity, allows for more mobility in the torso

Endothermic

warm-blooded, animals that have a complete separation of blue and red blood

Synapsids

this means they have a pair of openings in temporal region of skull, openings associated with attachment of mandibular muscles, early synapsids were herbivores and carnivores

Turbinate Bones

bones in the nasal cavity along with mucosal tissues to regulate airflow and warm and humidify inhaled air

Secondary Palate

the bony palate in the mouth that separates the nose from the mouth, allows for eating (suckling) while breathing

Diphyodont Dentition

two sets of teeth, first set is in the young ages for suckling, adult teeth come in for larger diets

Polyphyodont

Animal that has teeth that are constantly being replaced, seen in sharks and crocodile

Pelage

word for a coat of fur, hair, or wool

Undercoat

allows for more insulation in the winter, can be shed for warmer months

Guard Hairs

waterproofing and provide color, insulation

Vibrissae

"whiskers", sensory hairs that provide information to the nervous system

Molt

another term for shedding, some mammals “molt” the undercoat during warmer temperatures.

Vibrissae

“whiskers” they are sensory hairs that provide information to the nervous system

Quills

hairs that evolved to be hardened and sharpened, found on porcupines and hedgehogs

Horns

occur in antelopes, sheep, and cattle, hollow sheaths of keratinized epidermis, not shed and are usually branched, continue to grow and occur in both sexes, different horns can be found in giraffes, rhinos, and other mammals

Antler

found in deer family, made of solid bones with a velvet, during mating season they will scrape these to spread sent, sheds in the winter, calcium salts are used to grow from vegetables

Rhino Horn Trade

rhino horns have been used in traditional Chinese medicine and has caused poachers to nearly wipe out rhino populations, other eastern cultures use their horns for ceremony and special handles

Sweat Glands

sudoríferos glands, excretes water (sweat) for temperature regulation

Scent Glands

exocrine glands, excrete pheromones and “scents” that are used for mating, marking territories, and other functions

Sebaceous Glands

gland in the skin that secretes an oil found in hair or fur, provides waterproofing and moisture to skin

Linda Buck & Richard Axel

won the Nobel prize in the 70s for work on the genes of smells found in mammals

Specialists

a person who studies or works with a specific part or species of the animal kingdom. A specialist would only study water-nose dolphins.

Generalists

a person who studies a group or non-specific part of the animal kingdom. A generalist would study dolphins or aquatic mammals.

Homodont Dentition

animals whose teeth are all of the same type, ex. reptiles

Heterodont Dentition

animals that have different kinds of teeth, found in most mammals

Incisors

teeth with sharp edges for snipping or biting

Canines

teeth that are specialized for piercing

Premolars

compressed crowns with one or more sups, made for tearing and grinding food

molars

compressed crowns with one or more sups, made for chewing and grinding food

Deciduous Teeth

the “baby” teeth, first set of teeth that comes in as baby and begins to be replaced by permanent teeth

Permanent Teeth

the “adult” teeth, set that replaces the deciduous teeth

Insectivores

eat insects and small invertebrates, seen in anteaters, bats, and others

Carnivores

eat meat/other vertebrates aquatic carnivores have nearly homodont dentition, allows to not need food constantly, have mostly canines

Omnivores

feed on plants and animal tissue, include humans, racoons, bears, dietary opportunists that can change what they eat depending on food available

Herbivores

grazers, browsers, and gnawers, have a different GI tract to absorb and digest the plant matter, some have specialized fecal pellets that helps preserve nutrients, will re-eat it for nutrients, have to keep eating

Ungulates

Clade of mammals that have hooves instead of toes, horses, mules, goats, ect.

Ruminants

hoofed herbivorous grazing or browsing mammals, cows, goats, sheep, ect.

Gnawers

mainly rodents, take small bites or scrap parts of food off at a time while eating, mainly eat seeds and nuts

Cecotropes

pellets that are a product of the cecum, some of these animals will eat these after passed in order to pass the nutrients through twice for digestion, seen in rabbits

Migration

some mammals like caribous migrate in order to have a better food source, found more in marine mammals and bats

Flying

some mammals can fly through wings like bats

Gliding

some mammals are capably of gliding through connected webbing between the appendages, we see this in Flying squirrels who spread their arms and legs out and produce a kite-like structure

Echolocation

the location of objects by reflected sound, in particular that used by animals such as dolphins and bats.

Estrus

known as “heat”, a cycle found in female animals that is meant to induce reproduction, Females are usually are receptive only during a brief part of the estrus cycle

Monotremes

lay eggs, very few in the mammal world, platypus

Marsupials

have pouches where they are still embryos when born and need lots of milk and have a longer milk supply (longer lactation time)

Placentals

are viviparous and have a long gestation period, have a placenta that holds nutrients and cycles them from the mom to the young

Delayed Implantation

lengthens the gestation period of many mammals, this allows for the young to be born at a time of year for the best of their survival

Torpor

state of reduced activity and decreased metabolic rate, allows for long periods of sleep

Hibernation

a deep state of torpor where body temperatures drop to nearly ambient temperature and allow for animals to sleep nearly all winter

Primates

• Most are arboreal

• Flexible limbs are essential for tree-dwellers

• Highly developed senses

• monkeys

• humans evolved from this

New World Monkeys

howler monkeys, spider monkeys, tamarins, have a grasping tail

Old World Monkeys

baboons, mandrills, colobus, lack a grasping tail, have a close set nostrils, better and opposable grasping thumbs, two premolars in each jaw half

Apes

gibbons, orangutans, chimpanzees, bonobos, gorilla, and humans, larger cerebrum, loss of tail

Hominids

family that includes all Homoidae including humans and great apes

Hominin

Hominoids that are completely bipedal, only humans

Foramen Magnum

opening found at the base of the skull of human and chimpanzee, supports bipedalism

Homo sapiens

species of humans, arose in Africa abut 200,000 years ago, likely outcompeted the Neanderthals

Neanderthals

species of Hominid that were out competed by Homo sapiens, had a large skull that suggested a large brain, found to be alive with Homo sapiens

Sea otters (Enhydra lutris)

have the thickest fur of any mammal with up to 1 million hairs per square inch

Reindeer

both males and females have antlers but females never shed their antlers

Olfaction

mammals have one of the best senses of smell, olfactory receptors are at the surface of the nasal cavity and is processed in the cerebral cortex, have a Jacobson's organ, 1,000 olfactory genes have been discovered and make up 3% of the human genomes

Trophic Levels

1. producers (plants)

2. primary consumers, herbivores (insects, bunny)

3. Secondary consumers, carnivores (frogs, spiders, fish)

4. tertiary consumers, secondary carnivores (snakes, wolves)

5. apex predators (vultures, eagles, lions)

Therapsids

common ancestor of all mammals, disappeared in the great extinction