Evolution of mammals and mammalian diversity Flashcards
(89 cards)
1
Q
Describe the origins of mammals
A
Pelycosaurs and therapsids
2
Q
Describe the Pelycosaurs
A
- Pelycosaurs more primitive than therapsids
- mainly in Laurasia (N. hemisphere)
- sailbacks; not all had sails
- generalised amniotes
- no evidence of high locomotor capacity or metabolic rate
- non-mammalian synapsid
3
Q
Describe Archeothyris
A
- earliest pelycosaur
4
Q
Describe the Synapsids
A
- temporal fenestra
5
Q
Describe fenestral implications
A
- larger temporal fenestra indicates greater volume of jaw muscles
- implies more food eaten per day
6
Q
Describe Dimetrodon
A
- carnivorous pelycosaur
- most derived pelycosaur
- arched palate: first step towards separation of mouth and nasal passages
- elongation of neural spines into sail: evolved in dependently in two groups of
dimetrodon - no sexual dimorphism
7
Q
Describe therapsids
A
- more derived than pelycosaurs
- Gondwana
- increased metabolic rate
- trough in roof of mouth: airway separate from rest of oral cavity
- differentiation of teeth types
- flexible neck
8
Q
List some therapsids
A
- Titanophoneus
- Gorgonopsian
9
Q
Describe Massetognathus
A
- advanced cynodont
- enlarged infraorbital foramen: highly innervated face and maybe sensitive muzzle
- whiskers
10
Q
List the evolutionary trends of the Synapsida
A
- Larger temporal fenestra
- Greater teeth specialisation
- Development of bony secondary palate
- Limb position
- Dual gait locomotion
- Loss of lumbar ribs suggests diaphragm – higher rate of
respiration - Increasing ability to regulate internal temps and
chemical environments accurately
11
Q
Summarise the origin of the mammals
A
- pelycosaurs and therapsids
- radiation of Mesozoic mammals
- Dinosauria ascendancy
- Tertiary radiation
- Quaternary Megafaunal extinction
12
Q
Cenozoic
A
age of mammals
13
Q
Mesozoic mammals
A
= diverse taxonomically, homogenous in body form
14
Q
Most of mammal history is characterised by (2/3)
A
radiation in the Mesozoic
15
Q
Describe Mesozoic mammals
A
- tiny
- derived features: skull;
larger brain and inner ear - evolution of lactation and suckling
- hair
- special Harderian gland insulates fur (important for size)
16
Q
Give an example of a Mesozoic mammals
A
Megazostrodon, one of the earliest mammals
17
Q
After extinction of dinosaurs mammals
A
diversify into larger, more specialised forms
18
Q
List some Tertiary mammals:
A
- Moeritherium (Proboscidea)
- Brontotherium
- Phenacodus ‘condylarthran’
- Eocene whales
19
Q
Give some megafauna
A
- Megaceros (giant Irish elk)
- Smilodon
- Megatherium
- Phoberomys
- Procoptodon
20
Q
Describe Phoberomys
A
- 700kg
- 3 metres
- rodent
- South America, Miocene of Venezuela
21
Q
Describe Procoptodon
A
- 3m
- Pleistocene
- giant short-faced grazing kangaroo
22
Q
List some mammalian characteristics
A
- endothermy
- reproduction
- lactation
- hair
- high blood pressure
- high oxygen uptake
- high metabolic rate,
- water regulation (loops of Henle)
- improved locomotion
- improved sensory systems
23
Q
Describe lactation
A
- early innovation
- milk: antimicrobial, immunity; nutrition later
- young can be born at relatively undeveloped stage and cared for outside uterus
- reproduction at any time of year (not linked to food supply)
- complex teeth
24
Q
Describe lactation and teeth
A
- newborn mammals do not need teeth
- shift from continual replacement of teeth to diphyodonty
- occlusion
- diversified to exploit a
greater range of food and feeding strategies than seen in any group of vertebrate
25
Describe suckling
- uniquely mammalian
- fleshy seals formed against the bony hard palate with the tongue and the epiglottis
- isolates functions of breathing and swallowing
- changes in bony anatomy of palate and surrounding areas occurred in only the most derived cynodonts
- facial muscles = characteristic
26
Describe mammalian hair functions
- insulation
- camouflage
- communication
- sensation via vibrissae
27
Describe mammalian hair
- epidermis
- dermal papillae
- nerve endings
- capillaries
- arrestor pili muscle
- sebaceous gland
- hair root
- sweat gland
- group of fat cells
- dermis
- hair shaft
- free length of hair exterior to skin
28
Discuss mammalian sensory systems
- exceptionally large brain: neocortex
- reliant on hearing and olfaction (less on vision than other amniotes)
- evolved as nocturnal animals; visual sensitivity more important than acuity
- retinas largely rod cells (high sensitivity to light but poor acuity)
- cone fovea allows acute vision
29
Describe the Anthropoid primates
unique in having a brain specialised for visual sensory mode
30
Describe primitive, non-cursorial mammals
- basic mode of mammalian locomotion
- small body size over bumpy ground
- neither faster nor more efficient than in a similar sized reptile
- increased agility and an ability to keep breathing while running
- e.g. tree shrew
31
Describe the morphology of primitive, non-cursorial mammals
- cervical
- thoracic
- lumbar
- sacral
- caudal
- pelvis
- fibula
- tibia
- femur
- ulna
- radius
- humorous
- scapular
32
Describe the forelimb
- smaller than hindlimb
- rotation of loosely attached scapula on the rib cage
- no net thrust
33
scapula
shoulder girdle
34
Describe the hindlimb
- larger, pelvic girdle fixed rigidly to the sacral vertebrae
- foot: extra extensible unit
- provides all the thrust
35
Describe the morphology of fossorial mammals - the basics
- short limb bones
- stout
- muscle attachments well away from the joints
- powerful (slow) movement of the limbs
- e.g. European mole
36
Describe the morphology of fossorial mammals - the specifics
- origin of teres major
- insertion of teres major
- keeled manubrium
- groove and tunnel for bicep tendon
- origin of deep flexor
- olecranon
- falciform sesamoid broadens foot
- phalanges: short, broad
37
keeled manubrium
origin of pectoralis
38
Describe Echidna morphology
- sesamoids under distal phalanges
- carpus and metacarpus short
- large median epicondyle: origin of pronators and flexors
39
Describe cursorial mammal morphology
...
40
fossorial
digging
41
cursorial
running
42
Describe horse morphology
- tendon stretched as body moves forward over the leg
- shortens as foot leaves the ground
- springing action: additional propulsive force
- fetlock joint
- coffin joint
43
Describe cheetah locomotion
- hind leg rotation
- spine extension
- bounding action (body unsupported)
44
Who locomotes saltatorially
- kangaroo (Macropus)
- kangaroo rat (Dipodomys)
- springhare (Pedetes)
45
Who uses aerial locomotion?
- Coluga; flying lemur (Cynocephalus, Dermoptera)
46
Who uses aquatic locomotion
- eared seal (colonies)
- Pygmy Killer Whales
47
Describe some specialised forms of locomotion
- aquatic
- arboreal
48
Who uses arboreal locomotion?
- sloth: below the branches
- gibbon
49
How do gorilla locomote?
knuckle walking
50
Describe human bipedalism morphology
- ventral position of occipital condyles and foramen magnum
- S-shaped spinal curvature
- relatively short arms
- shorter iliac blade
- relatively long legs
- more compact feet
51
Discuss mammalian diversity
- reflects isolation of different groups on different land masses
- changing climates of higher latitudes in Cenozoic
- different habitats and associated adaptations (grassland etc)
52
List the 3 mammalian Subclasses
- Monotremata
- Marsupialia (Metatherians)
- Placentalia
53
Gives example of Monotremata
- Ornithorhynchus (duck-billed platypus)
54
Give an example of Marsupialia
- Didelphis virginiana (Virgin opossum)
55
Give an example of Placentalia
- Chrysochlorida (Golden Mole)
56
Describe the Monotremes
- egg-laying mammals
57
Give the two Monotremata Families
- platypus, Family Ornithorhynchidae
- echidna; spiny anteater: Family Tachyglossidae
- occur only in Australia and New Guinea.
58
Describe Monotreme reproduction
- cloaca
- lay eggs (ancestral)
- young have reptile-like egg tooth to escape
59
cloaca
single posterior opening for excretion and reproduction
60
Monotreme literally means
one holed
61
Describe Monotreme development
- small egg develops to form a rapidly dividing outer layer (envelops the egg)
- uterus secretes double-layered porous shell
- grows
- meroblastic cleavage
62
Monotreme egg
- amnion
- shell
- allantois
- yolk sac
- embryo
- mesoderm
- bilaminar yolk sac
63
Describe sex determination in the platypus
- multiple sex chromosomes
- male has 5X and 5Y
64
Describe the Platypus genome
large expansion of natural killer receptor proteins, certain antimicrobial peptides, and other components of the innate immune system
65
Describe Platypus venom
- venom spur on the heels of their hindlegs
- premating, defence
- gene duplication, divergence and neofunctionalisation
66
Describe the morphology that facilitates Platypus venom
- curved and hollow spur
- connected by ducts to venom gland under thigh muscles
67
Describe Platypus electrolocation
- determine the direction of an electric source by comparing differences in signal strength across the sheet of electroreceptors
- cortical convergence of electrosensory and tactile inputs: determining the distance of prey items
68
Describe Marsupials - the basics
- c.500 spp.
– South America (didelphid oppossums, caenolesdid shrew-opposums)
– Australasia (carnivore - Tasmanian devil, bandicoots (Peramelines), a single marsupial mole and many diprotontid herbivores (kangaroos, wallabies, possums, koalas etc)
69
Describe Marsupial development
- chorio-vitelline "placenta"
- allantois
- bilaminar yolk sac
- foetal membranes of wallaby
- mesoderm
- amnion
- uterus
- cervix
- bilaminar blastocyst
- e.g. wallaby
70
Describe Marsupial reproduction
- egg size intermediate between montremes and placentals
- development of jaws, facial muscles and tongue advanced
- CNS retarded
71
Describe Marsupial neonate girdles
- novel
- shoulder: allows them to get to nipple
- front claws holdfast
- shoulder arch brace
- crawling locomotion
- limits subsequent development
72
Describe Marsupial lactation
- complex
- lasts much longer
- oligosaccharides, proteins, fats, monosaccharides
73
List some South American marsupials (opossums)
- woolly opossum
- yapok, or water opossum
- Sarcophilus: the Tasmanian devil (carnivore)
- Phascolarctos: Koala (herbivore)
- Notoryctes: marsupial mole
- Burramys: the pygmy possum
- Petaurus: sugar glider
- Petauroides volans – better glider
- Petauroides - best glider
74
Describe Placetalia (Eutheria)
- Laurasiatheria
- Euarchontoglires
- Xenarthra
- Afrotheria
75
List some Afrotheria
- Hyracoidea (roch hyraxes)
- Sirenia (dugongs and manatees)
- Proboscidea (elephants)
- Chrysochlorida (golden mole)
- Tenrecida (tenrecs)
- Tubulidentata (aardvark)
- Macroscelidea (elephant shrews)
76
Which Placentalia have a Northern Hemisphere origin?
- Laurasiatheria
- Euarchontoglires
77
Which Placentalia have a South American origin?
Xenarthra
78
Which Placentalia have an African origin
Afrotheria
79
Describe Placentalia development
- placental bilaminar trophoblast
- inner cell mass -> embryo
- allantois
- placental foetal membranes
- amnion
- uterine epithelium
- choric-allantoic placenta
80
Describe Placentalia reproduction
- larger opening at base of pelvis than other mammals
- large live young
81
Describe the Placentalia return to water
- denser, more viscous than air
- light readily absorbed, suspended particles (turbidity); visibility poorer
- sound travels further, faster
82
Describe elephant seal vision
- 300–700 m
- adapt to poor light faster (6 mins to 20: humans)
83
Describe touch in harbour seals (Phoca vitulina)
- vibrissae
- rely solely whiskers to track hydrodynamic trails left by fish
84
Describe echolocation in bottlenosed dolphin (Tursiops truncatus)
- blow-hole
- melon
- auditory bulla
- oil-filled cavity in lower jaw
- sound in
- click out
85
Describe humpback whale communication (Megaptera novaeangliae)
- song structure
- local dialects in different populations
86
Describe mechanoreceptors
- sub- terrestrial adaptation
- Star nosed mole (Condylura cristata)
- 11 rays moved by tendons attached to facial muscles
- each ray contains hundreds of mechanoreceptive Elmer’s organs innervated by infraorbital nerve
87
Describe bat echolocation
- independent evolution
- frequency, bandwidth, duration and pulse interval
88
Where has echolocation evolved?
- bats
- shrews
- toothed aquatic mammals
89
Describe the long-eared bat (Plecotus auritus) and moth coevolution
ong-eared bat , listens for moth movement. Filters out other sounds.
* Uses echolocation to navigate obstacles, and then “stealth mode” to catch moth.
