Mammalian Characteristics And Evolution Flashcards
How many extant species of monotremes are there?
3
What are monotremes?
Egg laying mammals with extended maternal care: incubation followed by lactation from tufts of hair
What are the reproductive characteristics of the platypus?
1 species
Nests in a burrow and produces 2 eggs from a single functional left ovary
16 weeks of maternal care and the young have temporary molars
What are the reproductive characteristics of the Echidna?
2 species
Lays a single egg and incubates it in a pouch- homoplastic with the marsupial condition
How many extant species of marsupials are there?
334
70% in Australia
How are marsupials distinct to monotremes?
Separate anus and urinogenital sinus
Testes in scrotum outside the body wall
Paired lateral virginae and bifid (forked) penis
They have a placenta and gestational period
Discrete mammary glands with teats
How does a kangaroo have 3 offspring developing at different stages?
Kangaroo out of the pouch suckling
A joey on the teat in the pouch
Blastocyst in diapause
What do all marsupials develop?
A choriovitelline (yolk sac) placenta, which provides enough nutrients up to a certain developmental stage
What is the gestation period for marsupials?
10-20 days
Where does birth take place in marsupials?
Through the medial canal
What are the teeth like in opossum?
Heterodonty is very evident and they have a high dental formula
They have no tympanic bulla around the ear- allowing more teeth around the jaw area
What is the structure/function of bunodont teeth?
Flattened for crushing in omnivores
What is the structure of Lophodont teeth?
Ridged with grinding surfaces- the cement, dentine and enamel are all exposed
What is the structure of selenodont teeth? What species is it common in?
Crescent shaped molars, convergent with hypsodonty- typical in deer species
What is the function of sectorial cheek teeth?
Great for slicing and chewing up meat
Associated with tight jaw articulation
What are hypselodont teeth?
Open rooted teeth for continuous growth
What are the specialisations of incisors?
Gnawing, self-sharpening
What are ruminants?
Animals specialised to break down cellulose when they eat grass
What type of ruminants are a horse and a goat?
Horses: hindgut fermenter
Goats: foregut fermenter
What happens during digestion for the foregut ruminants?
They chew their food more than once and they pass through their different stomachs that have different functions for breaking down their food
Takes 80hrs
What happens during digestion for the hindgut fermenters?
Absorption takes place in the colon rather than the stomach and the rate of absorption is a lot faster- 40hrs
Name the one bone in the upper (proximal) part of each limb:
Humerus (fore)
Femur (hind)
What are the two distal bones articulated with them (humerus and femur) in each limb?
Radius and ulna (fore)
Tibia and fibula (hind)
What are the extremities in limb structure?
Carpi, metacarpi (fore)
Tarsi, metatarsi (hind)
Phalanges (digits)
What is plantigrade?
The stance where feet are on the ground with flexion at the wrist/ankle
What is digitigrade?
The stance where metatarsi/carpi are off the ground
Creates more power and acceleration
What is unguligrade?
The terminal phalanges (digits) and hooves support their weight
What is a Perissodactyla?
Odd toed ungulates
What is a Artiodactyla?
Even toed ungulates
What are cursorial herbivores?
Herbivores specialised for running
What are the two hypotheses on the evolution of cursorial herbivores?
- An evolutionary arms race between predators and prey
2. Low productivity grasslands replaced high productivity woodlands, requiring wider ranging to obtain food
What are fossorial adaptations?
They have short, massive limbs and specialised claws and teeth- useful for burrowing
E.g mole
What are arboreal adaptations?
Gripping feet and claws and a tail for balance
Opposable thumbs
What are Volant forms?
Animals with a patagium (flight membrane), which allows them to glide between trees
E.g flying lemur, flying squirrel
How many species of Chiroptera/bats are there?
986
What are the adaptations of amphibious forms?
Tail is used as propeller and rudder
They have webbed feet and paraxial swimming
E.g. beaver
What are some examples of mainly aquatic forms?
Pinnipedia and phocidae
What are the groups of completely aquatic mammals?
Cetacea
Odontoceti
Mysteciti
Dugong and manatee
What group makes up the largest proportion of mammals?
Rodents
Second is bats
What two phenomena have affected mammalian distribution?
- Vicariance: earth history and continental drift
2. Dispersal movements: the ability of animals to move from one continent to another when they’re joined together
