Mammals Flashcards
Describe mammalian size
Range in size
Most species are small
Describe mammalian ecology
Dominant role in terrestrial ecosystems as herbivores + predators
Also many top predators in marine food chains
Haven’t been able to reach distant islands e.g. Galapagos
Describe mammalian parental care
Elaborate parental care systems
- all provide care + nourishment for offspring
Describe mammalian social lives
Cooperative hunting & foraging groups in carnivores + primates
Parent-child relationships
Herds e.g. horses
Describe mammalian intelligence
Most intelligent of all animals
–> makes them adaptable + allows them to work cooperatively, communicate + use tools
What are the derived anatomical features (synapomorphies) of mammals?
> mammary glands + milk > young born helpless > fur > 2 sets of teeth > heterodont teeth w/ multiple cusps > warm blood (=endothermy) > muscular lips + cheeks > sophisticated smell + hearing > loss of colour vision > single bone in lower jaw
Compare primitive tetrapod dentition to mammalian
Pointy cones to poke prey vs multiple cusps
Lots of teeth vs few teeth
Little difference between teeth vs differentiation (incisors etc)
No interlocking vs upper + lower jaw interlock
Endless supply of teeth vs front teeth replaced once
How is the mammalian visual system modified?
Most have lost colour-sensitive cone cells from retina
= only have rod cells (sensitive to all wavelengths of light)
What other systems are elaborated in mammals for noturnality/low-light systems?
Vibrissae = whiskers
Ears
Nose
How does being endoderms benefit mammals?
Lets mammals forage, digest + grow when it’s cool
High speed in all temps
Permits high growth rates
Permits high reproduction rates
High metabolism
Possibly evolved for nocturnality
How could being endothermic negatively impact mammals?
Limited ability to reduce metabolism
-> vulnerable to seasonal food shortages
Describe parental care in mammals
Eggs protected - brooded in belly
Young born naked + helpless = dependent on adults
(altricial young)
Some have re-evolved young that can move soon after birth (precocial young)
What are mammary glands homologous to?
Eccrine glands
Why do mammals have muscular lips + cheeks?
Adaptation for suction feeding (nursing)
Describe parental instincts in mammals
All mammals have an extended period of care for offspring
Instinctive drive to care for juvenile mammals
H.sapiens instincts fixate on traits associated w/ immaturity
Parental attachement in juveniles
What are the major groups within mammalia?
Monotremes
Therians:
- marsupials
- placentals
What are the primitive features of monotremes?
> Lay eggs
Secrete milk from mammary glands
Cloaca
Low body temp
What are the specialised features of monotremes?
> Lack teeth
>Electroreceptors in snout
What are the derived characters of theria?
>Nipples >Vagina in females >Reduced eggshell + egg hatches in uterus >Ear flaps >Tribosphenic molars
What are the characteristics of marsupials?
> Care for young in pouch
Males have 2-pronged penis + females have a dual vagina
Tiny, poorly developed young
Small brains compared to placentals
What are the characteristics of placentals?
> Separate openings for reproduction, excretion + urination in females
Young nourished via placenta
Extended gestation + large young
Large brains
What are the major groups within placentals?
Xenarthra Afrotheria Boreoeutheria: - Laurasiatheria - Earchontoglires
What are perissodactyls?
Odd-toes hoofed mammals
What are artidodactyls?
Even-toed hoofed mammals
What are the features of primates?
Nails instead of claws 2 nipples Intensive parental care Long lifespan High intelligence
Describe the origins of mammals
- Tetrapods colonise land early Carboniferous
- Mammal-like reptiles 50my later
- Larger mammal-like reptiles dominate Permian
- End-permian extinction
- Proto-mammals are small + have parental care
- Small true mammals 1st appear in Jurassic after Triassic extinction
- Chicxulub/K-T extinction impact selects against large animals
- Rapid size increase in vertebrates
What explains the odd grouping of ecologically dissimilar animals e..g golden moles, elephants + sea cows?
This is the result of insectivores + omnivores survive the K-T extinction
-> then they move into new niches
