Mammal Exam 1

Traits of mammals

Mammary Glands & Milk, Hair, Endothermy (not diagnostic), Complext dentition

Live birth

Viviparity - NOT a defining factor, happens in nonmammals and monotremes lay eggs/

Mammary Glands & Milk - composed of (7) + example

composed of fats, proteins, vitamins, minerals, water, stem cells, and microbes. Seals have high fat concentration to help their babies form blubber and stay warm.

Hair

insulation, camouflage, communication, and sensory whiskers (vibrissae) - can be modiifed (porcupine spikes and pangolin scales

Where a dormant ancestral genetic pathway or trait is reactivated

atavism, can happen with milkline nipples

Hormonal regulation

Progesteron and estradiol during pregnancy to prime/enlarge mammory tissue.

Prolactin triggers milk production

Oxytocin when infant suckles to signal for release of milk into the ducts.

Weaning and adaptation

Hooded seals take only 4 days due to high fat in milk, while orangutans take years.

Secondary pallate/ seperate mouth and nose for suckling/ eating while breathing.

Melanin

Eumelanin (black/brown), pheomelanin (reds and yellows). Low levels of both gives blond.

Melanism = extra eumelanin, Albinism = none

Hair types (2) + length/thickness bc of size

Pelage (guardhairs and underfur), vibrissae. Smaller mammals tend to have more fur due to their SA to volume ratio while larger mammals have sparser fur.

Teeth

Heterodonty, Regional differentiation, tribophenic (complex cusps), diphyodont, double/triple rooted cheek teeth, occlusion.

Correct terminology for shared and new traits

Ancestral/pleisiomorphic and derived/apomorphic

Clades of amniotes (2 + their defining factor)

Diapsyids and synapsids (mammal lineage), destinguished by their # of temporal fenestra

First synapsid (1)

Pelycosaur: like lizards with canines (heterodonty)

Second synapsid group (1)

Therapsids: within pelycasaur, have semi-erect posture. reduced side to side motion, allowing animals to run and breath simultaneously (freed from carrier’s constraint).

Late synapsids (5)

Cynodonts: small (bc dinos), less priority on vision- more hearing, smell, and whiskers. secondary palate. likely endothermic. multi-cusped cheek teeth.

Jaw

Nonmammals: articular and quadrate bones.move to middle ear bones in mammals

First true mammal

Morganucodon - kept dinos from getting little

Fossils vs molecular clock

Traditional view: recognizable mammals showed up around 10my after asteriod - open land allowed for rapid diversification

DNA: mutation rates place much of this diversitification during dinos

Modern synthesis: the diversification happened while mammals were still tiny, and just allowed for faster radiation once the dinos were gone

Monotreme reproduction

10 sex chromosomes, lay eggs (echinda keeps in skin fold, platypus keeps in burrow near riverbank). Males have venomous spurs (convergent evolution w snakes, used for GLP1 peptide!)

Monotreme sensing

Electroreceptors and mechanoreceptors (platypuses have more of both)

Marsupial miscellaneous facts (3)

Only half have pouches (wombats backwards so they don’t get dirt in).

They have placentas.

Bifurcated Reproductive System: females possess two lateral vaginae leading to two separate uteri and males possess a forked penis positioned in behind the scrotum/testicles (monotremes have 4 heads)

Kangaroo reproduction

One female can support three young at different developmental stages simultaneously.

Young Joey: Outside the pouch, returning to nurse from a specific teat.

Newborn: Attached to a second teat inside the pouch.

Diapaused Blastocyst: A 70–100 cell embryo held in suspended animation inside the uterus

(chemically distinct milk for each baby)

Marsupial inferiority Arguments

Shorter gestation = altricial young + smaller brains.

GABI (great american biotic interchange) —> NA placentals knocked out SA marsupials

Counter arguments to marsupial inferiority

Extended lactation with short gestation is a low upfront investment strategy (helps in unpredictable environments — if baby dies it’s less of a waste of energy)

Virginia opossum success (prehensile tail, playing dead, 1-2yr lifespan)

Australian Marsupials (4)

Dasyurids, Peramelamorphia, Diprotodontia, Notoryctomorphia

Dasyurids (6 species)

CARNIVOROUS

Quoll: endangered

Tasmanian Devil: transmissable face cancer, big mouth, loud, dumb

Thylacine: Extinct b/c dingos + sheep farmers scapegoated them

Numbat: long tongue + narrow muzzle

Marsupial mouse

Antechinus: Mouse-like carnivore that exhibits extreme semelparity

Peramelamorphia (2)

Bandicoots & Bilbies (ecosystem engineers, placental-like placenta)

Diprotodontia (4)

HERBIVORES - Diprotodont dentition (large, forward-pointing lower incisors) and syndactyly

Koala

Wombat (those 2 have fingerprints)

Possums

Kangaroos/wallabies

Notoryctomorphia (1)

Marsupial mole

SA Marsupial clades

Dideltomorphia, Paucituberculata, Microbiotheria

Dideltomorphia

Fat-tailed opossum, wooly opossum, yapok/water opossum

Paucituberculata

Shrew/rat opossum

Microbiotheria

monito del monte -most related to australians

Extinct SA marsupials

Argyrolagus (like kangaroo rats, eaten by terror birds), thylacosmilus (saber tooth), borhyaenids (slow, stocky bear/wolf like carnivores)

The Overkill Hypothesis

Human disruption caused extinction of megafauna (lines up chronologically). African megafauna still exist bc they evolved alongside humans.

Whale pelvic bone

Muscles attach to these bones to move and control the male’s penis or females clitoris. Promiscuous species with high sperm competition possess larger, structurally more complex pelvic bones.

Vestigial traits

Still may be useful, just sometimes repurposed! Whale pelvis, human appendix (safehouse for gut microflora during illness), etc.

Whale skulls/back

Telescoped Skull: The skull bones at the back are squished together, and the front bones are stretched way out.

Blowhole: The nostril(s) moved to the top of the head so the whale can breathe at the surface without lifting its whole head out of the water.

Vertebrae move the tail up and down.

Baleen whale feeding methods (4) with examples

Skimming (swimming near surface w open mouth)

Lunge-feeding: Swimming up with a huge open mouth, expanding, then pushing the water out through the baleen (e.g., Blue Whales).

Bubble Net Feeding: Blowing a ring of bubbles to trap prey inside before lunging up through them (e.g., Humpback Whales)

Bottom Scooping: Diving to the sea floor to scoop up mud and filter out worms/clams (e.g., Gray Whales, which usually use the right side of their head).

Evidence Baleen Whales Evolved from Toothed Ancestors

The earliest fossil whales all had teeth.

Transitional Fossils show suction feeding evolved before baleen.

Embryos temporarily grow tiny tooth buds that disappear before birth.

Baleen whales still carry deactivated genes for making tooth enamel in their DNA.

Whale relatives

DNA closest to hippos, double-pulley ankle bone in fossil whales

Whale ancestors (3)

Small + not aquatic ancestors.

Pakicetus: A 4-legged land predator, but had whale-like ear bones.

Ambulocetus: Semi-aquatic, paddled with webbed feet, sealion like.

Basilosaurus: A 17-meter fully aquatic sea animal with tiny, non-walking back legs.

Whale diving adaptations (5)

Non-compressible bones,

Lungs collapse on purpose so nitrogen doesn’t enter the blood stream and cause “the bends”

Extra capillaries in lungs

Blood carries more oxygen (myoglobin modified)

Brachycardia (slow heart) + blood is shunted

Deepest diving whales

cuvier’s beaked whale (3000m deep, 138min).

also sperm whales.

Whale social behavior + brains

Many live in groups

Baleen whales make sound in larynx - humpbacks sync their songs

Play behavior (blowing bubbles, carrying leaves)

Teamwork + problem solving (humpbacks protecting other species from orcas, dolphins herding fish to the shore, orcas make waves)

Large brains - dolphins carry sea sponges over their snouts to protect them while digging in the seafloor for food.

Whale conservation status

whale processing ships.

Used baleen for corsets, meat, blubber + junk=oil, spermaceti (smokeless candles and soaps), abergris (fixitive in perfume).

hit by ships + tangles in fishing nets

hunting is illegal but we’re removing their resources.

Foregut fermenters

Chambers: the rumen, reticulum (food is chewed again), then on to the omasum and abomasum

Extract more nutrients but much slower.

Hindgut fermenters

Happens inside an enlarged cecum or large intestine.

Less efficient at extracting nutrients, but food passes quickly

Perissodactyls

Rhinos (3 toes), horses (one toe), tapirs (4 in front, 3 in back + flexible nose/trunk)

Horse evolution

Eohippus (fox-sized, crouched position, lower molars, toes like tapirs)

Eventually, they got bigger, teeth got taller, and toes reduced, (NOT LINEAR!)

Pronghorns

60+mph, both male and females have horns (not true horns bc keratin sheath is shed)

Giraffe neck

Long for foraging, males have longer necks and thicker ossicones (necking). Only 7 cervical vertebrae.

The nerve controlling the larynx goes from the brain, loops down into the chest around a main blood vessel near the heart, and comes back up to the throat (15ft) bc of evolutionary development constraint (in ancestral fish, this nerve passed under a blood vessel next to the gills)

When are females larger?

When males don’t need to compete, or when large body size provides an advantage to produce healthier young/defend them.

Groups of artiodactyls (7)

Tylopoda, pigs, whippomorpha, ruminatia, cervidae, moschidae, bovidae

Tylopoda

Camels: originated in NA then moved to Asia and went extinct here.

Sunia

Pigs! Males have tusks (peccary, babirusa)

Whippomorpha (3)

Whales and hippos.

2 hippo species=most dangerous in Africa (huge canines, feed at night, 5 tons).

Secrete red liquid as UV protection.

Herbivores but will eat meat opportunistically.

Ruminantia (6)

Herbivores

Open habitats

Social

Highly diverse

Common ancestor similar to mouse deer (Tragulidae)

Includes Antilocapridae, Tragulidae, cervids, and bovids

Cervidae (2)

Deer (white tailed, muntjac, moose, etc)

Antlers or tusks

Moschidae

Musk deer

Small (18kg)

Musk glands near genital/bowel (desirable for perfumes and traditional medicine)

Bovidae (5)

Highly diverse

Grazers and browsers

Pair of true horns (mostly males)

Horns vary in shape (sexual selection and species recognition)

Africa, Eurasia, NA

Bovid habitats

Dense vegetation = smaller groups, smaller animals bc higher quality + sparse food

Open = larger, weaponed, larger groups bc lower nutritional value in foods so more plentiful.

Conditions for evolution (3)

Variation, heritability, variants differ in reproductive success. (NOT about the good of the species)

Components of fitness (3)

Survival, mating success, fecundity (# offspring per reproductive event)

Causes of sexual dimorphism

Resource differentiation

Related to reproductive role (I.e. larger males to protect group or larger female pelvises for bearing offspring)

Sexual selection (inter, intra)

Intersexual selection goals (4)

Parental investment, territory/resources, not diseased, good genes (finding food, living long etc.)

Intrasexual selection (2)

Multiple mating= sperm competition

Weaponry/ornamentation

Sexual conflict

Insects → males give females hormones to make them less likely to mate with others

Spines on penis

Why should females mate multiple times? (4)

parental confusion, genetic variability, quality offspring (more fit=more sperm), in case one is sterile

Glires (groups-2 and traits 3)

Rodents and Lagomorphs

Hypsolodont incisors

Ever sharpening incisors (no enamel on the back)

Diastema (no canines)

Lagomorph defining feature

Rabbits + hares + pikas, two sets of upper incisors (rodents only have one)

Hares vs rabbits

All hares are rabbits, but live above ground rather than digging burrows.

Rabbits have shorter gestations and give birth to altricial young

Pikas (3)

short legs and ears, live on rocky mountain slopes + in meadows and forests, population specific dialects

Rodent overview

2300+ species (almost half of all mammals)

Diverged from lagomorphs

Jaw joints are offset so incisors and molars don’t touch simultaneously

Ground dwellers (3 species + fact)

Rats, mice, agouti

Carnivory has occured in some

Tree dwellers (Sciuridae) 3ish traits

Squirrels!

almost 300 species

padded feet

large tail for balance

Ankles twist around to cling upside-down

Gliders (1)

Flying squirrels - extra wrist cartilage to support wing (patagium)/steer/brake

Burrowers (2 types, adaptations)

NMR, moles

Either elaborated incisors or flatter heads

Incisors outside of mouth

Naked mole rats (4)

Eusocial (reproductive division of labor w/ queen, workers, and cooperative brood care - queens secrete ester pheramone)

Haplodiploidy (females diploid, males haploid so sisters more related than parents to children)

Live up to 30 yrs

Can’t get cancer

Aquatic Rodents (1 main + 4)

Beavers (ecosystem engineers)

Muskrats, nutria, capybara, aussie water rat

Rock dweller (1)

Gundi - stocky w short legs

Bipedal hoppers (4 species, 1 trait)

jerboa, kangaroo rat, hopping mouse, springhare

expanded auditory bullae

African crested rat

poisonous (eats bark and spreaks chemicals on back, which have hollow hairs that soak up the poison)

Ardi traits (4.4mya) - 5

foramen magnum underneath

longer ischium (pelvis) for climbing extension (crushed, reconstruction)

grasping foot

ape-like hands (short thumbs)

basic tool use

Aust. Afarensis (Lucy, 3.2 mya) - 4

valgus angle to knee joint

adducted hallux in footprints

human-like hand proportions

tool use

spine structure

humans have s shape and pyramidal configuration (larger lower bones) to protect against lower back strain + make COM over limb joints

Homo erectus (Turkana boy) - 4

Larger brain

Smaller teeth

Advanced stone tools

Human-like arches? (plantar fascia)

Homo sapiens! (4 times)

200kyr in Africa, 100kyr expansion, 50kyr cultural explosion, 10kyr agriculture

DNA evidence, related to neaderthals

Denisovans

Homo floresiensis

60-100kyr, related to homo erectus but smaller (island effect)

Homo naledi

7 indivuduals 1500 bones in cave (found by women in south africa)

Small brain + curved fingers

Like mix between homo and australopith

On races

there is more variation within “races” than between, so no biological basis for them.

closest clade to primates

dermoptera (flying lemurs)