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Flashcards in Mammalian Characteristics And Evolution Deck (40)
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1
Q

How many extant species of monotremes are there?

A

3

2
Q

What are monotremes?

A

Egg laying mammals with extended maternal care: incubation followed by lactation from tufts of hair

3
Q

What are the reproductive characteristics of the platypus?

A

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

4
Q

What are the reproductive characteristics of the Echidna?

A

2 species

Lays a single egg and incubates it in a pouch- homoplastic with the marsupial condition

5
Q

How many extant species of marsupials are there?

A

334

70% in Australia

6
Q

How are marsupials distinct to monotremes?

A

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

7
Q

How does a kangaroo have 3 offspring developing at different stages?

A

Kangaroo out of the pouch suckling

A joey on the teat in the pouch

Blastocyst in diapause

8
Q

What do all marsupials develop?

A

A choriovitelline (yolk sac) placenta, which provides enough nutrients up to a certain developmental stage

9
Q

What is the gestation period for marsupials?

A

10-20 days

10
Q

Where does birth take place in marsupials?

A

Through the medial canal

11
Q

What are the teeth like in opossum?

A

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

12
Q

What is the structure/function of bunodont teeth?

A

Flattened for crushing in omnivores

13
Q

What is the structure of Lophodont teeth?

A

Ridged with grinding surfaces- the cement, dentine and enamel are all exposed

14
Q

What is the structure of selenodont teeth? What species is it common in?

A

Crescent shaped molars, convergent with hypsodonty- typical in deer species

15
Q

What is the function of sectorial cheek teeth?

A

Great for slicing and chewing up meat

Associated with tight jaw articulation

16
Q

What are hypselodont teeth?

A

Open rooted teeth for continuous growth

17
Q

What are the specialisations of incisors?

A

Gnawing, self-sharpening

18
Q

What are ruminants?

A

Animals specialised to break down cellulose when they eat grass

19
Q

What type of ruminants are a horse and a goat?

A

Horses: hindgut fermenter

Goats: foregut fermenter

20
Q

What happens during digestion for the foregut ruminants?

A

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

21
Q

What happens during digestion for the hindgut fermenters?

A

Absorption takes place in the colon rather than the stomach and the rate of absorption is a lot faster- 40hrs

22
Q

Name the one bone in the upper (proximal) part of each limb:

A

Humerus (fore)

Femur (hind)

23
Q

What are the two distal bones articulated with them (humerus and femur) in each limb?

A

Radius and ulna (fore)

Tibia and fibula (hind)

24
Q

What are the extremities in limb structure?

A

Carpi, metacarpi (fore)

Tarsi, metatarsi (hind)

Phalanges (digits)

25
Q

What is plantigrade?

A

The stance where feet are on the ground with flexion at the wrist/ankle

26
Q

What is digitigrade?

A

The stance where metatarsi/carpi are off the ground

Creates more power and acceleration

27
Q

What is unguligrade?

A

The terminal phalanges (digits) and hooves support their weight

28
Q

What is a Perissodactyla?

A

Odd toed ungulates

29
Q

What is a Artiodactyla?

A

Even toed ungulates

30
Q

What are cursorial herbivores?

A

Herbivores specialised for running

31
Q

What are the two hypotheses on the evolution of cursorial herbivores?

A
  1. An evolutionary arms race between predators and prey

2. Low productivity grasslands replaced high productivity woodlands, requiring wider ranging to obtain food

32
Q

What are fossorial adaptations?

A

They have short, massive limbs and specialised claws and teeth- useful for burrowing

E.g mole

33
Q

What are arboreal adaptations?

A

Gripping feet and claws and a tail for balance

Opposable thumbs

34
Q

What are Volant forms?

A

Animals with a patagium (flight membrane), which allows them to glide between trees

E.g flying lemur, flying squirrel

35
Q

How many species of Chiroptera/bats are there?

A

986

36
Q

What are the adaptations of amphibious forms?

A

Tail is used as propeller and rudder

They have webbed feet and paraxial swimming

E.g. beaver

37
Q

What are some examples of mainly aquatic forms?

A

Pinnipedia and phocidae

38
Q

What are the groups of completely aquatic mammals?

A

Cetacea
Odontoceti
Mysteciti
Dugong and manatee

39
Q

What group makes up the largest proportion of mammals?

A

Rodents

Second is bats

40
Q

What two phenomena have affected mammalian distribution?

A
  1. 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