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Oxford - Diversity Of life > Mammals > Flashcards

Mammals Flashcards

1
Q

Synapsids

A
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2
Q

When did mammals originate?

A

Palaeozoic
Permian
(Pelycosaurs and therapsids)

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3
Q

When did mammals radiate

A

Triassic

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4
Q

When was the tertiary radiation of mammals?

A

Cenozoic

Tertiary

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5
Q

When was the megafaunal extinction?

A

Cenozoic

Quaternary

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6
Q

What was the megafaunal extinction?

A

The end of the Pleistocene which was distinguished by extinction of many large mammals such as mammoths, mastodons and ground sloths

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7
Q

Pelycosaurs

A

Late Paleozoic synapsids, excluding the therapsids and their descendants.

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8
Q

What is the earliest non mammalian synapsid (Pelycosaur)

A

Archeothryis

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9
Q

Non mammalian synapsid

A

Pelycosaur, therapsids, cynodont therapsids

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10
Q

Mammals

A

Monotremes
Marsupials
Eutherians

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11
Q

What is the defining feature of the synapsids

A

The temporal fenestra

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12
Q

Therapsids

A

Increased metabolic rate
Flexible neck
Teeth differentiation
Found mainly in Gondwana

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13
Q

ORIGINS

A

Therapsids

Pelycosaurs

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14
Q

Pelycosaurs

A

No evidence of metabolic rate or high locomotor capacity

Generalised amniotes

Found mainly in Laurasia

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15
Q

Pelycosaurs are more primitive than

A

Therapsids

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16
Q

When did therapsids appear in the fossil record?

A

Late Permian

250-290mya

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17
Q

What is the temporal fenestra

A

Allows the expansion of jaw musculature beyond the adductor chamber

Accommodâtes a larger bite

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18
Q

Features of the earliest Mesozoic mammals

A 
Tiny
Lactation and suckling evolution
Hair 
Special Harderian gland - insulates fur 
Derived features of the skull reflecting larger brain and inner ear
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19
Q

When did mammals diversify into larger, more specialised forms?

A

After the extinction of dinosaurs - Cenozoic tertiary period

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20
Q

LSRLHBE

Mammalian characteristics

A 
Locomotion (improved) 
Sensory systems (improved)
Reproduction
Lactation
Hair
High blood pressure, o2 uptake, metabolic rate, water regulation (loop of Henle)
Endothermic
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21
Q

What does lactation allow?

A

Reproduction at any time of the year

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22
Q

How has lactation increased mammalian diversity?

A

It gave rise to differentiation of teeth. Mammals diversified to exploit a greater range of food and feeding strategies.

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23
Q

Diphyodonty

A

Mammals with two successive sets of teeth: deciduous set and then the permanent set

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24
Q

What does lactation mean for newborn mammals

A

They do not need teeth

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25
Q

Why did lactation (milk) evolve?

A

Molecular evidence suggests it may have evolved for immunity and then nutritious advantages came later

26
Q

Advantages of lactation

A
  1. Newborn mammals don’t need teeth
  2. Allows production of offspring to be temporally separated from the season food supply
  3. Young can be born at a relatively young age and then cared for outside of the uterus
27
Q

Suckling

A

X

28
Q

Suckling

A

X

29
Q

4 purposes of hair

A

Insulation
Camouflage
Communication
Sensation via vibrissae

30
Q

What are mammalian brains like

A

Exceptionally large brains, neocortex

31
Q

What do mammals rely on for sensing

A

More reliant on hearing and olfaction rather than vision.

32
Q

What are mammalian retinas like?

A

Largely rod cells with high sensitivity to light

33
Q

Non cursorial (non running) mammal example

A

Tree shrew

34
Q

Non cursorial mammals

A

Increased agility and ability to keep breathing whilst running

35
Q

X

A

X

36
Q

X

A

X

37
Q

X

A

C

38
Q

Fossorial (digging) mammal example

A

European mole

Short limb bones
Muscle attachments well away from the joint

39
Q

Cursorial (running) mammal example

A

Horse

40
Q

5 specialised form of locomotion

A 
Saltatorial (Kangaroo)
Aerial
Aquatic
Arboreal (Sloth)
Bipedalism (humans)
41
Q

What are the three main modern mammal lineages?

A

Monotremata
Marsupialia
Placentalia

42
Q

How do monotremes reproduce?

A

Lay eggs

43
Q

Cloaca

A

Single posterior opening in monotremes which is for excretion and reproduction

44
Q

Meroblastic cleavage

A

Occurs in eggs with a high amount of yolk and leads to partial cleavage

45
Q

Characteristics of monotreme development

A

Mereoblastic cleavage

Eggs: uterus secretes porous shell layer around the embryo

Small egg develops to form a rapidly dividing outer layer that then envelops the egg

46
Q

What does male platypus have on the heels of their hind legs?

A

Male platypus have a venom spur on the heels of their hind legs. It may be used in premating to combat rights for females

47
Q

What are marsupials?

A

Characterised by presence of a pouch to carry the young (marsupials are mammals)

48
Q

Metatherians

A

Mammalian clade including mammals more closely related to marsupials than to placentals

49
Q

Where do marsupials occur

A

South America

Australasia

50
Q

Egg size of marsupials

A

Intermediate between monotremes and placentals

51
Q

Marsupial shoulder girdle

A

Shoulder girdle that allows them to get to the nipple by wriggling bodies using front claws as holdfast

52
Q

How does marsupial lactation compare to placental lactation

A

Not complex milk; it’s composition changes and lactation lasts longer

53
Q

Placentals are characterised by

A

Fetus being carried in the uterus of the mother

54
Q

How does where placentals reproduce from differ from mammals?

A

Placentals have a larger opening at the base of the pelvis than other mammals (large live young)

55
Q

What has the placental invasion of different environments (water, air, land) meant?

A

Aided diversification because exploitation of these environments meant new sensory systems evolved

56
Q

Example of vision in a placental mammal

A

Elephant seals feed at depths of 300-700m and have eyes that adapt to poor light faster than any other mammal tested.

57
Q

Example of touch in a placental mammal

A

Harbour seals have vibrissae whiskers that track hydrodynamic trails left by fish

58
Q

Example of use of sound by placental mammals

A

Echolocation in the bottle nosed dolphin

Echolocation in bats. Convergent evolution in different lineages of bats has occurred.

59
Q

Coevolutionary arms race between bats and moths

A

Bats evolved long ears (P. auritus) to listen for moth movements

Moths co-evolved to recognise the clicks of bats during echolocation. Aartiid moths produce own sounds to disturb the bats radar using a tymbal organ.

60
Q

What are the reproductive differences between

Monotremes
Marsupials
Placentals

A

Monotremes - lay eggs and have a cloaca instead of a uterus or vagina
Marsupials - offspring born in the embryonic stage and then crawl into mothers pouch where they continue to develop
Placentals - give birth to live young rather than laying eggs

Oxford - Diversity Of life (39 decks)

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