Mammalian Characteristics And Evolution

Question 1

How many extant species of monotremes are there?

Answer 1

3

Question 2

What are monotremes?

Answer 2

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

Question 3

What are the reproductive characteristics of the platypus?

Answer 3

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

Question 4

What are the reproductive characteristics of the Echidna?

Answer 4

2 species

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

Question 5

How many extant species of marsupials are there?

Answer 5

334

70% in Australia

Question 6

How are marsupials distinct to monotremes?

Answer 6

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

Question 7

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

Answer 7

Kangaroo out of the pouch suckling

A joey on the teat in the pouch

Blastocyst in diapause

Question 8

What do all marsupials develop?

Answer 8

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

Question 9

What is the gestation period for marsupials?

Answer 9

10-20 days

Question 10

Where does birth take place in marsupials?

Answer 10

Through the medial canal

Question 11

What are the teeth like in opossum?

Answer 11

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

Question 12

What is the structure/function of bunodont teeth?

Answer 12

Flattened for crushing in omnivores

Question 13

What is the structure of Lophodont teeth?

Answer 13

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

Question 14

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

Answer 14

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

Question 15

What is the function of sectorial cheek teeth?

Answer 15

Great for slicing and chewing up meat

Associated with tight jaw articulation

Question 16

What are hypselodont teeth?

Answer 16

Open rooted teeth for continuous growth

Question 17

What are the specialisations of incisors?

Answer 17

Gnawing, self-sharpening

Question 18

What are ruminants?

Answer 18

Animals specialised to break down cellulose when they eat grass

Question 19

What type of ruminants are a horse and a goat?

Answer 19

Horses: hindgut fermenter

Goats: foregut fermenter

Question 20

What happens during digestion for the foregut ruminants?

Answer 20

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

Question 21

What happens during digestion for the hindgut fermenters?

Answer 21

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

Question 22

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

Answer 22

Humerus (fore)

Femur (hind)

Question 23

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

Answer 23

Radius and ulna (fore)

Tibia and fibula (hind)

Question 24

What are the extremities in limb structure?

Answer 24

Carpi, metacarpi (fore)

Tarsi, metatarsi (hind)

Phalanges (digits)

Question 25

What is plantigrade?

Answer 25

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

Question 26

What is digitigrade?

Answer 26

The stance where metatarsi/carpi are off the ground

Creates more power and acceleration

Question 27

What is unguligrade?

Answer 27

The terminal phalanges (digits) and hooves support their weight

Question 28

What is a Perissodactyla?

Answer 28

Odd toed ungulates

Question 29

What is a Artiodactyla?

Answer 29

Even toed ungulates

Question 30

What are cursorial herbivores?

Answer 30

Herbivores specialised for running

Question 31

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

Answer 31

1. An evolutionary arms race between predators and prey

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

Question 32

What are fossorial adaptations?

Answer 32

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

E.g mole

Question 33

What are arboreal adaptations?

Answer 33

Gripping feet and claws and a tail for balance

Opposable thumbs

Question 34

What are Volant forms?

Answer 34

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

E.g flying lemur, flying squirrel

Question 35

How many species of Chiroptera/bats are there?

Answer 35

986

Question 36

What are the adaptations of amphibious forms?

Answer 36

Tail is used as propeller and rudder

They have webbed feet and paraxial swimming

E.g. beaver

Question 37

What are some examples of mainly aquatic forms?

Answer 37

Pinnipedia and phocidae

Question 38

What are the groups of completely aquatic mammals?

Answer 38

Cetacea
Odontoceti
Mysteciti
Dugong and manatee

Question 39

What group makes up the largest proportion of mammals?

Answer 39

Rodents

Second is bats

Question 40

What two phenomena have affected mammalian distribution?

Answer 40

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