Mammology Exam 1

Identify the morphological traits shared by all living mammals (fossil/skeletal/dental)

• double occipital condyle and atlas/axis complex

• single lower mandible bone/dentary-squamosal joint

• three middle ear bones

• heterodont and multicuspidate dentition

• complete secondary palette

• large jaw muscles

• muscular diaphragm and regional specialization of vertebral column

• upright posture

• relatively large brain with neocortex

homeothermy

the ability to maintain a stable temperature regardless of environmental conditions

how has homeothermy contributed to mammal diversification?

• ecological expansion

• nocturnal

  • 3 ear bones for better hearing

• cold climates

  • larger bodies, smaller appendages

  • insulation i.e fur

double occipital condyle and atlas/axis complex

move head up and down, and side to side which is useful for more foraging options and vigilance

single lower mandible bone/dentary-squamosal joint

better food processing

three middle ear bones

better hearing which allowed for expansion into nocturnal

heterdont teeth and multicuspdate dentition

could process a larger variety of foods

• incisors-gnawing and snipping

• canines-tearing, shearing, and holding

• premolars and molars-grinding tough foods

• diphyodont-two sets of teeth

upright posture

• more limb mobility

• control over individual limbs

• less energy to move

Complete secondary palate

nasal cavity is now fully separate from oral cavity

• more efficient airflow

• suckling can occur (contains supply of oxygen even when eating)

large jaw muscles

more Temporalis muscle makes chewing efficient and allows for chewing harder things

muscular diaphragm and regional specialization of vertebral column

• more flexible spine from regional specialization means more options to move

• can now compress and extend which creates negative and positive pressure improving oxygen intake

relatively large brain with neocortex

more advanced brain functions

Identify the morphological traits shared by all living mammals (soft tissue)

• hair/fur

• mammary glands

• viviparity

• four-chambered heart with functional left aortic arch

• enucleated red blood cells

• endothermy

• sweat/sebaceous glands

hair/fur

• insulation

• tactile

• defense/aggression

• balance

• locotory

sweat and sebaceous glands

• apocrine-social communication

  • ancestral

• eccrine-keep friction surfaces moist and temp regulation

• sebaceous glands secrete sebum

  • protects skin and hair

enucleated red blood cells

more surface area available for oxygen carrying capacity

viviparity

live birth

• endothermic egg retention → placenta

  • eggs started hatching inside eventually evolving into placenta

four chambered heart with functional left aortic arch

• oxygenated and deoxygenated blood never mixes, maximizing the amount of oxygen present

mammary glands

• monotreme—oozes

• eutherian and marsupial—contained, suckling

muscular diaphragm

creates a vacuum which draws in more oxygen

endothermy

the ability to generate body heat internally through metabolism

• can live in colder environments

• can maintain greater activity

• more niches

requires:

• more nutrients

• more efficient metabolism

what are the 2 superorders of Atlantogenata

Xenartha and Afrotheria

Atlantogenata origins

southern mammalian clade which separated from northern clade, its suborders split when South America and Africa did

biological significance of sexual reproduction to genetic diversity and evolutionary fitness

3 main modes of reproduction

• monotremes

• marsupials

• eutherians

monotremes

• oviparous (egg laying)

• paired uteri and ovaries

• eggs are leathery and incubated externally

• no nipples (lappers)

marsupials

• viviparous but short gestation

• altricial young (helpless) complete development in the marsupium (pouch)

• chorioviteline (yolk sac) placenta

• paired uteri Lutheran e

When did the Great Dying happen (years and era), what group survived?

252 mya, end of Permian era

Therapsids

how did Therapsids survive the Great Dying?

they were end-homeothermic so they could resist the climatic changes

Mammalian evolution order and traits

Amniotes

• pan-reptiles and pan-mammals

• shelled egg with amniotic membrane

Synapsids

• single temporal opening

• weakly heterodont teeth

• forming canines

Therapsids

• heterodont dentition

• Thecodont (bipedal)

• upright posture

• enlarged canines

• enlarged temporal opening

• secondary palate

Cyanodonts

• complete secondary palete

• more upright posture

• differentiated vertebrae

• strong heterodont dentition

  • tricuspid and double rooted cheek teeth

  • front teeth were most important while cheek teeth were relatively weak compared to early mammals

• larger temporal opening and brain

• larger dentary bone and smaller post-dentary bones

  • denture-squamosal joint

  • ear ossicles

  • larger masseter muscles

  • atlas/axis complex

  • limbs beneath body

  • muscular diaphragm

• Theria (marsupials and eutherians) vs Prototheria (monotremes)

what bones forms the secondary palate

maxillary and palatine

the unique features of mammal sex and reproduction

• lactation

• internal fertilization

• extended parental care

eutherian reproduction

• long gestation so the young are born more developed

• chorioallantoic placenta with varying degrees of intimacy

how have gestation lengths contributed to mammalian diversity

sex determination

Therians

• male sex is determined by SRY on Y chromosome (0 in some bats/rats), this initiates testis formation

Monotremes

• male sex is determined by Y-localized anti-mullerian hormone gene

Estrous

Period of female sexual receptivity and advertisement shortly before and after ovulation. It is affected by food availability.

• Monoestrous

  • one estrous cycle a year

• Polyestrous

  • several estrous cycles a year

spontaneous vs induced ovulation

• spontaneous ovulation is when the egg is naturally released (like humans or farm animals)

• induced ovulation occurs when copulation is happening (like animals in Africa)

4 different types of uterines

These different types of uteri reflect the transition from laying eggs to placenta

• duplex

  • two cervixes and uteri

• bipartite

  • horns are partially fused

• bicornate

  • most common

  • horns are separate

• simplex

  • horns completely fused