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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
Why did lactation (milk) evolve?
Molecular evidence suggests it may have evolved for immunity and then nutritious advantages came later
26
Advantages of lactation
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
Suckling
X
28
Suckling
X
29
4 purposes of hair
Insulation Camouflage Communication Sensation via vibrissae
30
What are mammalian brains like
Exceptionally large brains, neocortex
31
What do mammals rely on for sensing
More reliant on hearing and olfaction rather than vision.
32
What are mammalian retinas like?
Largely rod cells with high sensitivity to light
33
Non cursorial (non running) mammal example
Tree shrew
34
Non cursorial mammals
Increased agility and ability to keep breathing whilst running
35
X
X
36
X
X
37
X
C
38
Fossorial (digging) mammal example
European mole Short limb bones Muscle attachments well away from the joint
39
Cursorial (running) mammal example
Horse
40
5 specialised form of locomotion
``` Saltatorial (Kangaroo) Aerial Aquatic Arboreal (Sloth) Bipedalism (humans) ```
41
What are the three main modern mammal lineages?
Monotremata Marsupialia Placentalia
42
How do monotremes reproduce?
Lay eggs
43
Cloaca
Single posterior opening in monotremes which is for excretion and reproduction
44
Meroblastic cleavage
Occurs in eggs with a high amount of yolk and leads to partial cleavage
45
Characteristics of monotreme development
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
What does male platypus have on the heels of their hind legs?
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
What are marsupials?
Characterised by presence of a pouch to carry the young (marsupials are mammals)
48
Metatherians
Mammalian clade including mammals more closely related to marsupials than to placentals
49
Where do marsupials occur
South America | Australasia
50
Egg size of marsupials
Intermediate between monotremes and placentals
51
Marsupial shoulder girdle
Shoulder girdle that allows them to get to the nipple by wriggling bodies using front claws as holdfast
52
How does marsupial lactation compare to placental lactation
Not complex milk; it’s composition changes and lactation lasts longer
53
Placentals are characterised by
Fetus being carried in the uterus of the mother
54
How does where placentals reproduce from differ from mammals?
Placentals have a larger opening at the base of the pelvis than other mammals (large live young)
55
What has the placental invasion of different environments (water, air, land) meant?
Aided diversification because exploitation of these environments meant new sensory systems evolved
56
Example of vision in a placental mammal
Elephant seals feed at depths of 300-700m and have eyes that adapt to poor light faster than any other mammal tested.
57
Example of touch in a placental mammal
Harbour seals have vibrissae whiskers that track hydrodynamic trails left by fish
58
Example of use of sound by placental mammals
Echolocation in the bottle nosed dolphin Echolocation in bats. Convergent evolution in different lineages of bats has occurred.
59
Coevolutionary arms race between bats and moths
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
What are the reproductive differences between Monotremes Marsupials Placentals
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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