LECTURE 23 STUDY GUIDE (MAMMALS)

what are the defining characteristics of mammals?

1. nurse young via milk produced in mammary glands

2. possess hair

which two characteristics are erroneously used to define mammals?

1. live birth

2. warm blooded

which two other characters do mammals possess?

1. diaphragm used to ventilate the lungs

2. differentiated teeth used to chew food

which characteristics do mammals share in common with birds? why?

1. endothermy/homeothermy

2. 4-chambered heart

3. increased brain development

4. sensory specialization

5. K-selection (have few babies and care for them)

they are similar because mammals and birds underwent adaptive radiation during the same time period

what is the pulmonary pattern in mammals? (circulatory system)

right ventricle —> pulmonary arteries —> lung capillaries —> pulmonary veins —> left atrium

what is the systemic pattern in mammals? (circulatory system)

left ventricle —> aorta arch

what is the inferior pattern in mammals? (circulatory system)

abdominal aorta —> systemic capillaries of abdomen and hind limbs —> inferior vena cava —> right atrium

what is the superior pattern in mammals? (circulatory system)

arteries of the aortic arch —> capillaries of head, thorax, and forelimbs —> superior vena cava —> right atrium

which kind of lungs do mammals possess: positive or negative pressure?

negative pressure

how do mammals ventilate their lungs?

through their diaphragm (contraction/relaxation)

what is inhalation?

when the volume of the pleural cavity increases as the ribcage lifts up and out while the diaphragm contracts decreasing internal air pressure that is filled by external air

what is exhalation?

when the volume of the pleural cavity decreases as the ribcage falls down and in while the diaphragm relaxes increasing the internal air pressure that forces air out of the lungs

what are incisors (front teeth) specialized for?

remove chunks of food from its source

rodents use incisors to gnaw

what are canines specialized for?

slice through flesh like a blade of scissors

what are premolars specialized for in carnivores and herbivores?

to slice food for carnivores

to grind food in herbivores

what are molars specialized for in carnivores and herbivores?

grind fibrous plant material (herbivores)

slice (carnivores)

what are herbivores?

plant eaters

either have multiples stomachs, relatively short small intestines, extensive cecums or extensive colons to harbor microbes that help digest their plant-based diet

what are carnivores?

meat eaters

have a single stomach, extensive small intestines, small cecums and relatively short colons

what are omnivores?

eat both meat and plants

have a little of both carnivore and herbivore characteristics

in which group are humans classified?

omnivores

from which lineage did mammals descend?

synapsid

how did dimetrodon differ in its locomotion therapsids that give rise to extant mammals?

3.5 m reptile-like synapsid with a side-ward jutting limbs and a sail to regulate its temperature

what do synapsids possess?

single temporal opening in the skull called a temporal fensestra

what are therapsids?

more mammal-like with limbs positioned beneath the body but were relatively small

what was the candidate for a common ancestor for mammals?

extinct family of weasel-like animals with skulls 3-6 cm

how did the skull and jaws change during synapsid evolution?

they were rearranged changing the way jaws hinged/articulated

which bones formed the hinge of the jaw in early and later mammals?

the quadrate and articular to the dentary and the squamosal

how did the modification of the skull and jaw articulation impact cranial capacity? how did this impact the size of brains?

allowed the cranium to enlarge increasing brain capacity

two bones that served as jaw hinge bones in early mammals were re-purposed. what did these bones become in modern mammals according to some researchers?

middle ear bones

articular —> malleus quadrate —> incus

what are the three groups of mammal taxa?

1. monotremes

2. marsupials

3. eutherians (placental mammals)

how do the three mammals taxa differ in regard to the maturity at which offspring hatch/born?

monotreme and marsupial mammals hatch/born at a very early stage of development

eutherians are not born until they have gone extensive embryonic development

which taxa(-on) is oviparous? which is viviparous? which taxon has the most extant species?

1. monotremes —> oviparous (5 spp.)

2. marsupials —> viviparous

3. eutherians —> viviparous (most extant with 5010 spp.)

where do monotremes live?

australia and new guinea

where does a platypus live?

in burrows dug into the banks of freshwater rivers and lakes in eastern australia

what are the two kinds of monotremes?

platypus and echidnas

how do monotreme offspring gestate?

platypus —> female lays 2-4 eggs and incubates them on her belly

echidnas —> females lay a single egg with a pouch incubating until it grows its spines

how do monotremes nurse?

they lack teats so milk is lapped off belly which are about 1/3 to ½ m long

how does a platypus differ from an echidna?

platypus are crepuscular using its snout to feed on insect larvae, worms, etc in the sediments

echidnas are nocturnal and use their snouts to locate termite and ant mounds, claw them open, and eat the inhabitants

where do marsupials live?

confined to australia with some in the americas

what likely explains the marsupials distribution?

continental drift and climate

how do marsupials offspring gestate?

born early in development but are viviparous with teats

how do marsupials nurse? which adaptations do marsupials have to foster post-birth development outside of the mother’s womb?

mom may have a pouch or folds of skin covering her teats and newborns must make their way from the vagina to the teats to complete their development by nursing off the milk

how does the urogenital anatomy of a typical marsupial compare to that of a eutherian?

most females possess 2 lateral vaginae with each containing a cervix, uterus, and oviduct, and a median vagina (often ephemeral) that serves as a birth canal

all vaginae and bladder open through a urogenital sinus to the cloaca

most males possess a retractable penis with a bifurcated tip used only to transfer sperm

urinary tract along with the anus open via cloaca (applies to males)

what is convergent evolution?

similar body plans/features but are not closely related

which marsupials and eutherians serve as examples of convergent evolution?

plantigale and deer mouse

marsupial mole and moles

sugar glider and flying squirrel

wombat and woodchuck

tasmanian devil and wolverine

kangaroo and patagonian cavy

where do eutherians live?

most common in asia but are in north america too

how do eutherians differ from other mammalian taxa?

viviparous but have long gestation times

what is an artiodactyla?

hooves with an even number of toes on each foot; herbivorous

what are examples of artiodactyla?

sheep, pigs, cattle, deer, giraffes

what is a carnivora?

sharp, pointed canine teeth and molars for shearing; carnivorous

what are examples of carnivora?

dogs, wolves, bears, cats, weasels, otters, seals, walruses

what is a cetacea?

aquatic; streamlined body; paddle-like forelimbs and no hind limbs; thick layer of insulating blubber; carnivorous

what are examples of cetacea?

whales, dolphins, porpoises

what is a chiroptera?

adapted for flight; broad skinfold that extends from elongated fingers to body and legs; carnivorous or herbivorous

what is an example of a chiroptera?

bats

what is an lagomorpha?

chisel-like incisors; hind legs longer than forelegs and adapted for running and jumping; herbivorous

what are examples of lagomorpha?

rabbits, hates, picas

what is a primate?

opposable thumbs; forward-facing eyes; well-developed cerebral cortex; omnivorous

what are examples of primates?

lemurs, monkeys, chimpanzees, gorillas, humans

what is a rodentia?

chisel-like, continuously growing incisors worn down by gnawing; herbivorous

what are examples of rodentia?

squirrels, beavers, rats, porcupines, mice

which order has the most species?

rodentia

which order inhabit the mojave desert?

rodentia

in which order are humans classified? which other biota are also classified within this order?

primates

apes, monkeys, lemurs

how do monkeys and apes differ?

monkeys have tails and apes do not