exam 2 study guide - mammals

What do perissodactyls and artiodactyls have in common?

Hooves, herbivorous diets, and cursorial adaptations for running.

What is a cannon bone?

Fusion of two metapodial bones forming a single weight-bearing structure.

Name characteristics that ungulates possess associated with cursorial locomotion.

Long metapodials, calcaneum not articulating with fibula, adaptations for speed.

Differentiate between perissodactyls and artiodactyls.

Perissodactyls: lophodont teeth, mesaxonic (weight on middle toe). Artiodactyls: selenodont teeth, paraxonic (weight on two middle toes).

Differentiate the types of 'headgear' ungulates possess.

Rhino horn (keratin), giraffe ossicones, deer antlers (shed), pronghorn horns (shed sheath), bovine horns (permanent).

Which Artiodactyl family is the sister taxon to the cetaceans?

Hippopotamidae.

Does use of the common name 'deer' outline a monophyletic group?

No, 'deer' includes convergent species; only Cervidae is monophyletic.

Differentiate oviparity from viviparity.

Oviparity: ancestral, eggs laid externally with moderate yolk. Viviparity: evolved, embryo develops internally; high maternal energy demand.

What are the structures of male mammalian reproductive anatomy?

Testes produce sperm through spermatogenesis where spermatogonia matures to sperm and testosterone; may be abdominal, inguinal, or scrotal; seasonal descent in some species.

What are the structures of female mammalian reproductive anatomy?

Ovaries produce ova; fertilization in oviduct; embryo develops in uterus; cervix and vagina form reproductive tract.

Compare male reproductive anatomy across subclasses.

Monotremes: bifid penis, abdominal testes.

Marsupials: bifid/single penis, anterior scrotum, baculum (penis bone) in some species.

Placentals: single penis, posterior scrotum, baculum in some.

Compare female reproductive anatomy across subclasses.

Monotremes: cloaca, paired uteri.

Marsupials: two uteri/vaginas, common urogenital sinus (urinary and vaginal track fused, one opening for both).

Placentals: fused uteri, single vagina.

Compare development of newborns in subclasses.

Monotremes: egg-laying, highly altricial.

Marsupials: embryonic young, develop in pouch.

Placentals: complete young, variable maturity.

What is the estrous cycle?

The cyclic period of heat and receptivity controlled by hormones and environmental cues.

How is the estrous cycle different from a menstrual cycle?

Menstrual: uterine lining shed if no fertilization. Estrous: lining reabsorbed.

What is the difference between monestrous and polyestrous?

Monestrous: one heat per year. Polyestrous: multiple cycles yearly.

When and where does ovulation and fertilization occur?

Ovulation in ovaries during estrus; fertilization in fallopian tubes.

Match hormones to source and phase.

LH (pituitary) regulates estrus; estrogen (ovary) peaks before ovulation; progesterone (corpus luteum) maintains luteal phase.

Difference between spontaneous and induced ovulation?

Spontaneous: without copulation. Induced: triggered by mating stimulus.

What is the placenta and its function?

Connection between mother and fetus; nutrient/waste exchange; hormone production; immune suppression.

Which infraclass shows most placenta variation? What class has higher level of mom/fetus contact?

Eutheria.

Describe types of placenta by villi shape/distribution.

Choriovitelline: yolk sac based, minimal villi.

Chorioallantoic: vascular, with villi—more efficient exchange.

Why do newborn marsupials rely on cutaneous respiration?

Lungs underdeveloped; skin assists in early oxygen exchange.

Compare lactation in marsupials vs placentals.

Marsupials: long lactation, milk composition changes. Placentals: shorter lactation, stable milk.

Which infraclass has lower reproductive energy cost?

Eutherians; more efficient than marsupials and monotremes.

Why is reproductive timing controlled?

To ensure births occur during favorable environmental conditions (temperature, food, energy).

Name mechanisms altering reproductive sequence.

• Delay fertilization - store sperm when hibernating and delay fertilization until spring

  • Sperm nourished by female uterine lining, viable for 198 days

• Delay implantation - development arrested at blastocyst stage

• Delay development (embryonic diapause) - embryonic development delayed after implantation (up to 4 months), development resumes in spring

Which characteristics are unique to Cetacea?

• Dorsal fin

• Blowhole

• Telescoping skull

• Odontocetes: asymmetrical skull + melon for echolocation

• Mysticetes: baleen (filter feeder)

Why are cetaceans so large?

Blubber and buoyancy allow massive size; aquatic environment supports weight.

Morphological aquatic adaptations in cetaceans.

Streamlined body, flippers, no hindlimbs, blubber insulation, internal testes, tail propulsion.

What is a telescoped skull?

Bones compressed and overlapped; blowhole shifted to top of head.

How do mysticetes use baleen?

Filter-feed by taking in water and expelling it through baleen, trapping prey.

Characteristics linked to echolocation in odontocetes.

Melon focuses sound; fatty jaw receives echoes.

Difference between rorquals and right whales.

Right whales have larger baleen and arched skull; rorquals have shorter skull and throat pleats.

Are river dolphins monophyletic?

No, evolved convergently from different odontocete ancestors.

Differentiate dolphins and porpoises.

Dolphins: conical teeth, beak, curved dorsal fin.

Porpoises: spade teeth, blunt snout, triangular fin.

Characteristics uniting Paenungulata.

No clavicle, mammae between forelegs, bicornuate uterus, abdominal testes.

Which paenungulates show horizontal tooth replacement?

Sirenia and Proboscidea.

What is graviportal limb structure?

Massive columnar limbs supporting heavy body weight.

Difference between browser and grazer.

Grazer: eats grass, broad snout. Browser: eats leaves, narrow face, reaches high foliage.

Where is bacterial fermentation in non-ruminants?

Cecum or large intestine; larger in high-fiber diets.

Foregut vs hindgut fermentation differences.

Foregut (ruminant): efficient, slow, less water need. Hindgut: faster, less efficient, more water-dependent.

Is coprophagy found in ruminants or non-ruminants?

Non-ruminants; improves nutrient absorption.

Adaptations for myrmecophagy.

Strong claws, elongated skull, reduced teeth, long tongue, thick skin for protection.

Why do myrmecophagous mammals have scales/spines?

Defense from insect bites.

Which feeding groups have tongues attached to sternum?

Myrmecophages (for long tongue extension).

Why do granivores cache food?

Store seeds for winter survival.

Which herbivores aid plant reproduction?

Granivores (seed dispersal), Frugivores (pollination), Mycophages (spore dispersal).

Characteristics of sanguinivores.

Feed on blood; sharp incisors, grooved tongue, anticoagulant saliva.

Differentiate aquatic carnivore dentition.

Krill-eaters: baleen.

Molluscivores: flat teeth.

Piscivores: pointed teeth.

Which clades have low metabolic rates?

Xenarthra (Cingulata, Pilosa) — limits distribution to warm climates.

Which group shows cranial kinesis?

Lagomorpha — allows skull flexibility during feeding.

Differences between rabbits and hares.

Rabbits: altricial (helpless) young in burrows. Hares: precocial young in open forms.

Which order shows suspensorial locomotion?

Pilosa — sloths hang from trees.

Myrmecophageous adaptations preventing bites.

Thick skin, long sticky tongues, no teeth.

Differentiate Cingulata vs Pholidota armor.

Cingulata: bony plates covered in keratin scales, rigid. whole body

Pholidota: keratin scales, flexible. only on back

Which human disease do armadillos carry?

Leprosy.

Aardvark prey protection.

Thick skin, closable nostrils, long hair around eyes/nose.

What is a type specimen?

Reference specimen that defines a species for identification and taxonomy.

Differentiate poikilothermy, homeothermy, and heterothermy.

Poikilothermy: variable body temp based on environment.

Homeothermy: constant temp via endothermy.

Heterothermy: mix of both. Can be regional to pards of body, or vary based on time of day/year

Why regulate temperature internally?

Allows independence from ambient temperature extremes and efficient physiology.

What is the thermoneutral zone?

Temperature range with minimal metabolic effort.

What factors determine mammal energy needs?

Activity level and environmental conditions.

• For mammals living in extreme cold, what are their two major needs?

• Sufficient food

• Produce heat fast to counteract heat lost

How does countercurrent heat exchange help cold survival?

Warm arterial blood transfers heat to cool venous blood, conserving body warmth.

Continuum of heterothermic responses.

• Temporarily abandon homeothermy

  • Allow base temp to drop as a response to cold

• Larger mammals have shallow hibernation called winter lethargy, base temp regulated within 10c of normal

• Deep hibernation base temp falls to 1c away from ambient, reduced O2 consumption, apnea, markedly reduced heart rate: weeks to months

  • Largest mammal is genus Marmota

• Occurs in all 3 subclasses

• Different species respond to different stimuli for torpor

  • Ambient temp, decreasing food supply - chipmunks

  • Endogenous physiological cues (obligate hibernation) like marmots and ground squirrels

Phases of torpor and body size effects.

Entry, maintenance, arousal; larger mammals enter longer torpor and arouse slower.

How do mammals prepare for seasonal torpor?

Increase fat reserves for energy during inactivity.

• If it’s so cold, and mammals don’t have space heaters, how do they warm up? Be sure to describe both the function and the position of brown adipose tissue in your answer.

• Non-shivering thermogenesis

  • Metabolize brown adipose tissue, which has many fat droplets per cell (rather than 1 in white fat cells) which is well vascularized and innervated with lots of mitochondria) 

  • Cellular respiration in BAT produced heat instead of ATP

  • BAT can produce heat 10x muscle contraction

Why is it good that BAT is well vascularized?

Distributes heat quickly, supplies oxygen and nutrients.

Countercurrent exchange in small cetaceans.

• Countercurrent heat exchange, keep fins cool and body warm (tongue/palate as well in baleen)

• Keep body temp and testes stable and at optimal temp

• Vascular specializations in blubber

Countercurrent exchange in dolphin fins.

Heat-conserving (cold water) vs heat-dissipating (warm water) systems; maintains homeothermy.

How does countercurrent exchange in blubber vary?

Retains heat in cold water, releases heat in warm water.

How do mammals balance water intake and loss?

Drink water, metabolize food, reduce evaporation; maintain homeostasis.

Difference between metabolic and drinking water.

Metabolic water produced by food oxidation; major source for desert species.

Which kidney structure concentrates urine?

Longer loop of Henle increases concentration power, water reabsorbed in collecting tubules

Evaporative cooling methods.

Sweating (salt loss), panting (efficient), saliva spreading, urination, vasodilation.

How does respiratory heat exchange conserve water?

Cools exhaled air to condense moisture before expiration. makes less water be evaporated

How does countercurrent exchange protect the brain?

Cools blood entering the brain, preventing overheating.

How does vasodilation help dissipate heat?

Increases blood flow to skin to release heat.

Difference between estivation and hibernation temperatures.

Hibernation: low temp dormancy; Estivation: high temp dormancy for heat avoidance.

• Granivores

• - gnawing seeds nuts, some hide food underground

  • rats/mice

• Folivores

• - eat leaves stems and buds, toxic compounds inactivated by liver

  • koala

• Frugivores

• - fruit eater - teeth adapted for piercing/crushing

  • bats

• Nectarivores

• - pollen/flower nectar - elongated skull with underdeveloped jaw muscles, brush tipped tongues

  • bats

• Mycophages

• - fungi eater

  • primates, rodents, marsupials

• Gummivores

• - resin/sap - claws for clinging to trees, gum digested in cecum

  • marmosets

• Afrotheria

• Tubulidentata

  • Aardvark

  • monotypic

• Xenarthra

• Cingulata - armadillo

• Pilosa - sloths, anteaters

  • Low metabolic rate for body size

• Euarchontoglires

• Lagomorpha

  • Cranial kinesis

• Laurasiatheria

• Philodota - pangolin

• Body size

• - be big

• Insulation

• - fur and fat

  • most direct method of decreasing heat lost

• Coloration

• - glogers rule, lighter color in colder climates

  • Some are year round

  • Some controlled by neuroendocrine to respond to day length changes

• Microclimate modification

• - group thermoregulation / huddling in elaborate nests

• Food hoarding

• - helps conserve energy and avoid competition+predators

• Reduction of body mass

• - general decline in body mass in small mammals over winter 

  • Dehnel’s phenomenon

• Dormancy -

• period of inactivity which reduces metabolic rate

• Temporal hyperthermia

• - temporarily abandon homeothermy, allow base temp to drop as a response to cold

• Arousal

• Alarm arousal - ambient temp drops beyond animals ability to compensate

• Periodic arousal - arousal in absence of external cues, happens many times across hibernation

  • Short but energetically costly

  • 1-2 days at normal temp