Mammals

Question 1

Describe mammalian size

Answer 1

Range in size

Most species are small

Question 2

Describe mammalian ecology

Answer 2

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

Question 3

Describe mammalian parental care

Answer 3

Elaborate parental care systems

- all provide care + nourishment for offspring

Question 4

Describe mammalian social lives

Answer 4

Cooperative hunting & foraging groups in carnivores + primates

Parent-child relationships

Herds e.g. horses

Question 5

Describe mammalian intelligence

Answer 5

Most intelligent of all animals

–> makes them adaptable + allows them to work cooperatively, communicate + use tools

Question 6

What are the derived anatomical features (synapomorphies) of mammals?

Answer 6

> 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

Question 7

Compare primitive tetrapod dentition to mammalian

Answer 7

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

Question 8

How is the mammalian visual system modified?

Answer 8

Most have lost colour-sensitive cone cells from retina

= only have rod cells (sensitive to all wavelengths of light)

Question 9

What other systems are elaborated in mammals for noturnality/low-light systems?

Answer 9

Vibrissae = whiskers
Ears
Nose

Question 10

How does being endoderms benefit mammals?

Answer 10

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

Question 11

How could being endothermic negatively impact mammals?

Answer 11

Limited ability to reduce metabolism

-> vulnerable to seasonal food shortages

Question 12

Describe parental care in mammals

Answer 12

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)

Question 13

What are mammary glands homologous to?

Answer 13

Eccrine glands

Question 14

Why do mammals have muscular lips + cheeks?

Answer 14

Adaptation for suction feeding (nursing)

Question 15

Describe parental instincts in mammals

Answer 15

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

Question 16

What are the major groups within mammalia?

Answer 16

Monotremes

Therians:

• marsupials
• placentals

Question 17

What are the primitive features of monotremes?

Answer 17

> Lay eggs
Secrete milk from mammary glands
Cloaca
Low body temp

Question 18

What are the specialised features of monotremes?

Answer 18

> Lack teeth

>Electroreceptors in snout

Question 19

What are the derived characters of theria?

Answer 19

>Nipples
>Vagina in females
>Reduced eggshell + egg hatches in uterus
>Ear flaps
>Tribosphenic molars

Question 20

What are the characteristics of marsupials?

Answer 20

> Care for young in pouch
Males have 2-pronged penis + females have a dual vagina
Tiny, poorly developed young
Small brains compared to placentals

Question 21

What are the characteristics of placentals?

Answer 21

> Separate openings for reproduction, excretion + urination in females
Young nourished via placenta
Extended gestation + large young
Large brains

Question 22

What are the major groups within placentals?

Answer 22

Xenarthra
Afrotheria
Boreoeutheria:
- Laurasiatheria
- Earchontoglires

Question 23

What are perissodactyls?

Answer 23

Odd-toes hoofed mammals

Question 24

What are artidodactyls?

Answer 24

Even-toed hoofed mammals

Question 25

What are the features of primates?

Answer 25

Nails instead of claws
2 nipples
Intensive parental care
Long lifespan
High intelligence

Question 26

Describe the origins of mammals

Answer 26

1. Tetrapods colonise land early Carboniferous
2. Mammal-like reptiles 50my later
3. Larger mammal-like reptiles dominate Permian
4. End-permian extinction
5. Proto-mammals are small + have parental care
6. Small true mammals 1st appear in Jurassic after Triassic extinction
7. Chicxulub/K-T extinction impact selects against large animals
8. Rapid size increase in vertebrates

Question 27

What explains the odd grouping of ecologically dissimilar animals e..g golden moles, elephants + sea cows?

Answer 27

This is the result of insectivores + omnivores survive the K-T extinction
-> then they move into new niches