Biodiversity 8: The mammals

Question 1

Describe the key features of the class mammalia

Answer 1

Endothermic vertebrates
Possess hair made of keratin, with fat = insulation
Skin glands inc mammary (modified sweat gland)
4 chambered heart → needed to support high metabolic rate

Question 2

Describe some anatomical features of mammals

Answer 2

Limbs carried beneath body
Synapsid skull (1 fenestra) with large braincase
Jaw consists of a single bone
Ear comprises 3 ossicles derived from jaw bones

Question 3

Describe the 2 types of mammalian hair

Answer 3

Thin soft under hair - insulation
Thick long guard hair - protection

Question 4

Give some examples of modified mammalian hair and their functions.

Answer 4

Porcupine quills → protects against predators
Pangolin scales →protects against predators and water loss
Puma whiskers → sensory
Rhino horn → matted hair, protection

Question 5

What are mammalian ossicles originally made from?

Answer 5

The bones originally in the jaw of the reptiles = malleus and incus

Question 6

Why is having 3 ossicles an adaptation?

Answer 6

Sound detection and distinction much more evolved

Question 7

What are the 4 types of mammalian teeth?

Answer 7

Incisors
Canines
Premolars
Molars

Question 8

What are incisors used for?

Answer 8

cutting, shearing

Question 9

What are canines used for?
In which mammals are they found?

Answer 9

piercing, ripping (absent in herbivores, dominant in carnivores)

Question 10

What are premolars used for?

Answer 10

slicing, crushing

Question 11

What are molars used for?

Answer 11

grinding (bone or coarse vegetation)

Question 12

What is the dental formula?

Answer 12

I-C-P-M

Question 13

What is the dental formula in placental mammals?

Answer 13

3-1-4-3/3-1-4-3

Question 14

What is the dental formula in humans?

Answer 14

2-1-2-3

Question 15

Which adaptations allowed Mesozoic mammals to survive the extinctions of the Cretaceous and radiate?

Answer 15

hair and fat provide insulation

Question 16

Describe the prototheria

Answer 16

‘one opening’
Reptilian characteristics:
Egg laying (egg is reptilian in structure)
Cloaca
Mammalian characteristics:
Hair
Mammaries

Question 17

What are the 2 forms of prototheria?

Answer 17

Platypus
Echidna - spiny anteater

Question 18

Describe the platypus

Answer 18

aquatic life
Webbed feet, thick fur, no ears
Bill for feeding on invertebrates (convergent evolution)
Find prey using electric pulses

Question 19

Describe the echidna

Answer 19

Long snout
Sticky tongue
Heavy claws

Question 20

Describe the metatheria

Answer 20

Egg contains yolk, shell membrane
Embryo nourishes mostly by yolk then placenta later on
Short gestation, young altricial <1% mother weight
Young are completely dependent on mother for 1st month
Young have strong forelimbs and claws, climb into marsupium (pouch) where mammaries are located
E.g Koalas, Virginia Opossum, Red Kangaroo

Question 21

Which clade do marsupials belong to?

Answer 21

Metatheria

Question 22

Which clade do placental mammals belong to?

Answer 22

Eutheria

Question 23

Describe the Eutheria

Answer 23

al mammals - Eutheria
Complete development in uterus
Most extant orders originated 50-70 mya
Phylogenetic relationships between orders are difficult to resolve as they radiated rapidly

Question 24

What are the 4 major lineages in the Eutheria?

Answer 24

Afrotheria e.g elephants
Xenarthra e.g sloths
Laurasiatheria e.g moles, bats, cats
Euarchontoglires e.g rabbits, mice

Question 25

Give some examples of species that belong to afrotheria

Answer 25

Elephants Manatees and dugongs

Question 26

Give some examples of species belonging to xenarthra

Answer 26

Sloths, anteaters, armadillos - have reduced or no teeth

Question 27

Give some orders belonging to laurasiatheria

Answer 27

Insectivores - moles, shrews, hedgehogs Bats Carnivores - cats, dogs, seals Cetaceans - whales, dophins Artiodactyles - sheep, pigs, deer Perissodactyls - horses, rhinos

Question 28

Which order is considered the most primitive of the Laurasiatheria

Answer 28

Insectivores

Question 29

Describe carnivores specialised dentition

Answer 29

Specialised for piercing (incisors) and slicing (carnassial pair)

Question 30

Describe the artiodacytes

Answer 30

sheep, pigs, deer Even toed ungulates Bunodont or selenodont teeth Elaborate ruminant stomach to digest cellulose (e.g cows chew twice) Weaponry evolved in many - Tusks - Antlers - Horns

Question 31

Describe the Perissodactyls

Answer 31

horses, rhinos Odd toed ungulates Lophodont grinding molars and incisors for cropping vegetation Simple single stomach

Question 32

Which orders belong to Euarchontoglires?

Answer 32

Lagomorphs Rodents

Question 33

Describe the lagomorphs

Answer 33

Rabbits, hares 2 pairs of rootless incisors Rootless molars, high crowned (hypsodont)

Question 34

Describe the rodents

Answer 34

Most specious mammals Rootless incisors, hypsodont molars Most pass food twice (caecotrophy)