Lecture 1 mammals

Mammals are all at some point in development ___ (3 traits)

Hirsute - hair

lactogenic - milk production

endotherms - internal heat production

Soft anatomy traits (12)

1. Hair

2. Mammary Glands

3. Endothermy

4. Viviparity (except Monotremes)

5. 4-chambered heart

6. Enucleated red blood cells

7. Muscular diaphragm

8. No renal portal system

9. Complex integumentary structures (horns, sweat glands, etc.)

10. Nitrogenous wastes excreted as urea

11. Complex facial dermal muscles

12. Extreme expansion of the cerebral cortex of the brain

Viviparity

Live birth with the exception of monotremes. Has a placenta and amniotic egg.

4 chambered heart

Facilitates separation of blood and deoxygenated blood.

Better movement and respiration through the body.

Enucleated blood cells

Without nucleus - more surface area for oxygen to bind to = more oxygen to body and easy moving through body

Muscular diaphragm

Separates thoracic cavity from abdominal cavity = allows for more lung capacity and more oxygen

No renal portal system

No stop off at the kidneys which allows for more efficient blood movement and speeds up moving oxygen around

Complex integumentary structures

Horns, sweat glands, other glands

Waste as urea

Non toxic way of getting rid of waste - the liver allows mammals to do this

Complex facial dermal muscles

Whiskers to sense the environment and pass information to brain

Expansion of the cerebral cortex of the brain

Allowing for more coordination of movement

Soft characteristics as a whole are allowing mammals to __

be more efficient (especially oxygen transfer)

Hard anatomy traits (14)

1. Double occipital condyle

2. Epiphyseal line on long bones

3. Lower jaw in single bone on each side (= dentary bone)

4. Dentary-squamosal jaw articulation

5. 3 middle ear ossicles (= malleus, incus, and stapes)

6. Tympanic bone present

7. Teeth are restricted to the perimeter of the jaws

8. Dentition usually heterodont

9. Dentition diphyodont (only 2 sets of teeth: milk teeth and adult teeth)

10. Hard secondary palate

11. Thoracic ribs only (no lumbar ribs)

12. Calcaneus (heel bone) present (= specialized tarsal bone)

13. Phalangeal formula (finger-toe bones) reduced to 2-3-3-3-3

14. Shoulder girdle reduced to one, sometimes 2, elements

(scapula, clavicle)

Double occipital condyle

Allows organism to rotate neck - more flexible head movement

Epiphyseal line on long bones

Line where growth occurs = harden early during dev = harder to break as opposed to if growth was in the middle of the bone = stronger bones and joints

Growth is restricted to the ends of the bone

Lower jaw in single bone on each side (= dentary bone)

single bone in jaw

Dentary-squamosal jaw articulation

Jaw bone articulates with one bone in skull

3 middle ear ossicles (= malleus, incus, and stapes)

Small bones go to the ear = better hearing for mammals

Tympanic bone present

Surrounds and suspends the eardrum = separates inner ear from middle ear and houses tiny middle ear bones

Teeth are restricted to the perimeter of the jaws

One line of teeth

Dentition usually heterodont

Multiple different types of teeth

Dentition diphyodont

2 sets of teeth in a lifetime - milk and adult teeth

Hard secondary palate

Clear separation of nasal and oral cavity = eat and breathe at same time

Thoracic ribs only (no lumbar ribs)

More flexibility and ribs do not restrict us

Calcaneus (heel bone) present (= specialized tarsal bone)

increase speed

Systematics definition

Science of classifying organisms based on their evolutionary relationships - how are organisms related to each other?

Monophyletic (monophyly)

Includes all organisms descended from a single most recent common ancestor

Polyphyletic (polyphyly)

Composed of unrelated organisms descended from more than one common ancestor (does not include most recent common ancestor)

Paraphyletic (paraphyly)

Does not include all organisms descended from a common ancestor

Synapomorphy

trait shared by two or more taxa (shared derived trait)

Sympleisiomorphy

a shared ancestral character state (all have it)

homologous/homology

structures with similar evolutionary/phylogenetic origin but not with a similar function/behavior/identical structure

analogous

structures in two or more organisms that have similar function but the similarity is not the result of descent from a common ancestor

evolution

change through time in a population/lineage

evolutionary trend

directional change through time within a lineage

Convergent evolution

Evolutionary trend observed in distantly-related organisms where each lineage shows independent evolution of superficially-similar features. These lineages converge on the same trend/morphology via different developmental pathways

Parallel Evolution

Evolutionary trend observed in 2 lineages whom share a fairly recent common ancestor where each shows independent evolution of a similar feature via similar development pathways

Homoplasy

A similarity in a character in two different species that arises from evolutionary convergence or parallelism, not common ancestry (noise)

Convergent evolution examples (3)

Desert rodents - distantly related and all evolved for desert efficiency with long big legs for jumping - Desert rodents and lizards - all developed similar colors

Marsupial vs placental mammals - similar features (ex. sugar glider vs flying squirrel, Tasmanian tiger vs wolf, wombat vs groundhog)

Diastema - loss of premolars in horses, rodents, marsupials, multituberculata

Parallel evolution example

aquatic adaptations in piinipeds phocidae and otariidae - related but not sister taxa - hindlimbs

Paleozoic era major events

Permo-triassic crisis = glaciation, warming, volcanos

Greatest extinction 96% marine 70% terrestrial 57% all families 83% all genera

Synapsids

mesozoic era major events

Entering a warming period

Age of dinosaurs and mammals - diversifying after extinction

Pangea breaking = gondwana and laurasia

Land animals becoming stranded (vicariance)

Further separtion in jurassic

Late cretaceous major events

multituberculates widespread and therians

marsupials in north america dispersing south

placentals in asia dispersing west

Kpg/KT boundary

Extensive mountain building (rockies pushed up for 2nd time)

Massive extinction from dust cloud or volcanos or microbes

chicxulub crater yucutan - deccan traps in india

Cenozoic era major events

Marsupials dispersing

grasslands evolving

placentals dispersing

last glaciation (wisconsinan)

major mammal extinctions - large animals

mountains building

Future world

pangaea ultima

The position and orientation of continents affects

climate and circulation of oceans

Vicariance

The geographic isolation of populations of a once widespread species by the development of a physical barrier within the ancestral species range. Results in interrupted gene flow, genetic differentiation, and possibly speciation of isolated populations (PASSIVE)

Dispersal

the one-way movement or spreading of organisms from natal to new area (ACTIVE)

Barriers = oceans, deserts, mountains, climate

Speciation pump models

(also called cyclical vicariance model) A model that attributes the high diversity of tropical communities in South America to repeated fragmentation and reconnection of tropical forests caused by the glacial and interglacial cycles of the Pleistocene

Gondwana effect

There is higher diversity/endemicity in the south

Madagascar organisms are related to Africa and India

Types of dispersal

Corridors - connect similar habitats

Filter zones - connect different regions and habitats

Sweepstakes routes - of variable surrounding habitats

North to south

Increase in diversity as you go south (lower latitude) Could be because of climate or vegetation

West to east

Higher diversity in the west could be because of mountains, elevation, or time based

Effects of glaciers

kettle lates

ice dams - cut off rivers = big lakes

pluvial lakes

Glaciation 3 major effects

habitat

change dispersal routes

climate

-species need to move, adapt, or go extinct

Species pumps

dispersal south/north or east/west in response to glacier movement (tracked by fossil record)

Rivers are able to

facilitate or prevent dispersal

Chordata characteristics

o Bilateral Body Plan

o Notochord

o Dorsal Neural Tube

o Pharyngeal Gill Slits

o Muscular Post-Anal Tail

o Groove/Pocket in Pharynx (Endostyle – stores Iodine)

Amniotic egg

Membrane with a semi-permeable shell allowing for gas exchange with the environment. Contains yolk for nutrition and a membrane to store waste.

Can lay eggs on land and facilitate terrestrial variation

Temporal Fenestrae

Anapsid - no fenestra

Synapsid - one (synapsis/mammals)

Diapsid - two (archosaurs)

Synapsids were the first _

amniotes to radiate in terrestrial habitats

Therapsida

middle permian, replace pelycosaurs

more mammal like - temporal bar, sagittal crest, hetero/diphyodonty, hard 2ndary palate

Dinocephalia

Anomodontia

Teriodontia

Cynodontia - Galesauridae

Dinocephalia

large, incisors, pachyostasis/thickened bones (headbutting), hinge jaw movement

Anomodontia

toothless, beaked turtlelike bill/pads to smash food

temporal openings enlarged

sliding jaw articulation

permo-triassic crisis - lineages decimated

Theriodontia

land dwelling mammal like

precise dental occlusion

versatile jaw movements

moveable quadrate bone

Pelycosauria

Sphenacodontidae -Dimetrodon

paraphyletic, early permian dominant, excting by end of permian, very large

dimetrodon had heterdont dentition and a modified skull to rip prey, reflected lamina, large sail

Synapsida

small/agile

water ties

amniotic egg

dominant in permian and top preditors in triassic

Paleozoic - late perm

pangea , lots of mountain building

permo-triassic

end of permian = greatest exctinction of all time 99% of life

Cynodontia

small

nocturnal

carnivore

dentary squamosal jaw articulation

hard 2nd palate

occipital condyles

warm blooded with hair

Galesauridae

first with dentary squamosal jaw articulation

single lower jaw = inc strength

hard 2nd palate

large brains

depend on hearing and smell

2/3 of mammalian history went extinct in

the mesozoic

Jaw changes over time

1 jaw bone and small bones go to ear =improve sound transmission

we can see this in opossum development

The hard secondary palate is possibly

the origin of lactation = facilitate liquid diet - young organisms dont need teeth while growing - can lead to 2 sets of teeth

Precise occusion

allows the grinding and breaking up of food

Post cranial changes over time

legs went from splayed out like a crocodile to being under the body which allows for better locomotion for terrestrial movement

Prototherians

- Morganucodontidae/Tricodonta ex

- Docodonta ex

- Multituberculata (Subclass Allotheria) ex

- Monotremata (Subclass Prototheria)

Therians

- Symmetrodonta

• Kuehneotheriidae ex

- Eupantotheria

• Dryolestidae ex

• Peramuridae ex

• Boreosphenida ex

• Methatheria (Infraclass)

• Eutheria (Infraclass)

Prototherians

dentary squamosal

large cochlear region

2 occipital condyle

locomotion

mammalian body posture

What are the 3 extinct groups of prototherians?

Morganucodontidae/Tricodonta

• Late Triassic to mid Cretaceous

• Insectivorous/carnivorous

• Three-cusped tooth

Docodonta

• Middle Jurassic to early Cretaceous

• Descriptions based on teeth and jaws

• Omnivores

• Complex teeth – molars rectangular

• Ancestral jaw articulation (reptilian)

Multituberculata (Subclass Allotheria)

• Herbivorous

• Rodent-like incisors

• Many cusps

Multituberculata went extinct because of

competition with placental rodents (eocene/oligocene)

Monotremata

oviparous

australia/new guinea

decreased with comp with marsupials

Tribosphenic molars

upper molar - paracone, metacone, protocone
lower molar - protoconid, paraconid, metaconid

talonid heel

precise occlusion

how did tribosphenic molars evolve

Concrescence Hypothesis

• Merge teeth, and germinal buds of teeth, into 1

• Expect reduction in number of teeth

Differentiation Hypothesis

• Each tooth differentiates

• Cusps are independent of the germinal root

• Increase complexity without reduction in number of teeth

Are the origins of mammals monophyletic?

Yes theory - mammals all come from the cynodont (can see this with dentary squamosal jaw articultion)

No theory - the trait could have evolved independently

hair, lactation, endothermy, viviparity all help with _

metabolism, locomotion, terrestrial habits, nocturnal behavior, increased rate of feeding and respiration

Homeothermy

Maintaining a constant internal body temperature (e.g., modern mammals, birds, and some others)

Poikilothermic

Having a fluctuating internal body temperature depending on the local environmental conditions (e.g., typical reptiles and actinopterygiian fish

heterothermy

Oscillating between homeothermic and poikilothermic (e.g., bats, hummingbirds).

Ectothermy

Relying on the environment and behavior to regulate body temperature (e.g., typical reptiles)

Endothermy

Generating internal heat to moderate body temperature (e.g., modern birds and mammals. Independent evolution during the Mesozoic)

Endothermy is

costly! Compared to a similarly sized ectotherm (lizard), an endothermic mammal needs 10x amount of food & oxygen to generate heat

A small organism has a __ surface area to volume ratio

High ratio = lose heat

A large organism has a __ surface area to volume ratio

a low ratio = do not lose heat easily

Endotherms use __ to retain heat

insulatory structures (hair)

Why did hair and endothermy evolve?

evolved for sensory reasons first (whiskers to sense things at night) later used for insulation

Mammals are __

endothermic homeotherms

Viviparity evolved in the

cretaceous or earlier

possibly independent evolution

viviparity in marsupials vs placentals

marsupials - short gestation, long development

placentals - long gestation, short development

Metatherian ancestors are from

North america then dispersed south