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VERTEBRATES > Amniotes and the conquest of the land reptiles > Flashcards

Amniotes and the conquest of the land reptiles Flashcards

1
Q

What makes the amniotic egg different from other eggs?

A

Presence of 3 extraembryonic membranes (Chorion, Allantois, Amnion)

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2
Q

What are the two main groups of amniotes?

A
  • Sauropsids
  • Synapsids
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3
Q

What group gave rise to the amniotes?

A

Reptilomorphs

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4
Q

Features of the amniotic egg: Allantois

A
  • Used as a storage for waste (from embryo)
  • Vascularised for gas exchange
  • Left behind when animal hatches
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5
Q

Features of the amniotic egg: Amnion

A
  • Grows around developing embryo
  • Sac filled with amniotic fluid
  • Protects embryo
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6
Q

Features of the amniotic egg: Chorion

A
  • Surrounds entire embryo and membranes
  • Can become vascularised and used for gas exchange
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7
Q

Features of the amniotic egg: Albumin

A
  • Egg white in chicken egg
  • Source of protein and water
  • Helps keep the embryo moist
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8
Q

Features of the amniotic egg: Shell

A
  • Can be leathery (ancestral)
  • Birds have highly specialised - calcified
  • Protection
  • Some exchange from outside environment - gas/water
  • Eggs can dry out
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9
Q

Features of the amniotic egg: Yolk

A

Food source / Nutrients

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10
Q

Features of the amniotic egg: Chalaza

A
  • Stringy
  • Suspends yolk in albumin
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11
Q

What distinguishes amniotes from non-amniotes?

A

Amniotic egg

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12
Q

What groups are amniotes?

A

Birds, Reptiles and Mammals

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13
Q

What groups are non-amniotes?

A

Fish & Amphibians

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14
Q

What are the advantages of an amniotic egg?

A
  • Increased surface area for gas exchange
  • Shell provides support
  • Still unsure why the amniotic egg evolved
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15
Q

What type of fertilisation is required?

Reproduction of amniotes

A

Internal Fertilisation

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16
Q

Reproduction of amniotes

A
  • Most males have intromittent organs / penis (vast majority of birds don’t)
  • Females have clitorises/hemiclitores (snakes)
  • Link between male and female sex organs
  • Environmental sex determination - possibly ancestral.
  • No larval stage (direct development inside egg) - has to be laid on land
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17
Q

What are the skeletal characters of amniotes

Derived features of amniotes

A
  • Axis and atlas - head rotation - vertebrae found in the neck.
  • Modified in the amniotes (C1 and C2). cervical neck vertebrae
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18
Q

Reduced skin permeability

Derived features of amniotes

A
  • Thicker, keratinised, more lipids
  • Skin elaborations: scales, hair feather (all homologous - formed from epidermal placode.)
  • Alpha keratin found in all amniotes
  • Beta keratin only found in sauropsids
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19
Q

What is Costal (rib) Ventilation?

Derived features of the amniotes

A
  • Use ribs to move air in and out of lungs
  • Allows air to be drawn over a further distance - allows development of longer neck
  • More complex nerves controlling forelimb (due to longer neck)
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20
Q

What is temporal fenestration?

Derived features of the amniotes

A
  • Holes in the skull
  • Synapsid skull (one arch) / one hole
  • Diapsid (two arches) / two holes
  • Can have modified diapsid skulls - secondary adaptation - arches lost (commonly snakes)
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21
Q

How is the modern mammal skull modified?

A
  • Holes have combines to allow space for muscles
  • Muscles attach upper and lower parts of skull behind cheekbones.
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22
Q

How do amniotes and non-amniote skull shapes differ?

A
  • Non-amniotes had flat skulls - buccal pumping, abductor muscles allowed for opening and closing of mouth.
  • Amniotes - smaller domes shaped skull - differentiation of abductor muscle into two muscles - allowed for sophisticated movement of jaw.
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23
Q

How did the amniote skull change?

A
  • Muscles moved to attachment on top of skull (not on the inside roof)
  • Allowed enlargement of muscles
  • Enlargement of hole allowed for larger muscles
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24
Q

Types of skull fenestra

A
  1. Anapsid (no hole)
  2. Synapsid (1 hole)
  3. Diapsid (2 holes)
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25
Q

Example of an Diapsid

A

Crocodilian

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26
Q

Example of a synapsid

A

Mammals

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27
Q

Example of an anapsid

A

Turtle although they are actually diapsid but have lost the holes

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28
Q

What are the sauropsids?

A
  • Turtles diapsid but look anapsid (sister group to archosaurs)
  • Tuatara, snakes and lizards - lepidosaurs
  • Crocodiles, dinosaurs, pterosaurs, birds – archosaurs
  • Archosaurs diverged from lepidosaurs in Permian
  • lizards, snakes, turtles, crocodiles, and birds.
29
Q

Turtles and tortoises (Chelonia)

Sauropsids

A
  • Very derived group
  • Body made up of carapace
  • Vertebrae and ribs are fused to carapace
  • Keratin scutes on surface
  • No teeth - keratin beak-like structure - ancestral forms had teeth
  • Flexible neck
  • Plastron
30
Q

How do Chelonia breathe?

A
  • Issues with breathing
  • Movement of ribs restricted because they are fused to carapace
  • Contraction of muscles causes gut moves down
  • Lungs attached to gut via connective tissues
  • As gut is pulled down - lungs are moved down - inflated - opposite
  • Aquatic turtles use hydrostatic pressure also use pharynx & cloaca for gas exchange
31
Q

How does the chelonia carapace vary between terrestrial and aquatic forms?

A
  • Most terrestrial chelonia have domed carapace
  • Most aquatic forms have flattened / streamlined carapace
32
Q

The green turtle

A
  • Herbivorous
  • Feed and nest far apart
  • Massive migrations
  • Chemosensory info - light and wave direction / magnetism
  • Hatchlings crawl to the brightest light
  • Light over sea is brighter than light over land.
  • Issues with light pollution.
33
Q

How did chelonia evolve?

A
  • Debate as to where group developed? Water or land? May have evolved in aquatic environment - debate to this.
  • Odontochelys - ancestral type - carapace was not well developed so support for aquatic development.
34
Q

What are some features of Tortoise mating?

A

Head bobbing
Fighting
Biting / ramming
Cloaca - waste excretion and reproductive opening

35
Q

What is environmental sex determination?

A
  • Sex outcome of offspring is temperature dependent
  • E.g. females only occur at higher temps in turtles (opposite in lizard example)
  • Theory - higher temp sex = larger sized sex
  • Conservation implications
36
Q

What happened to Kemp’s ridley turtle population due to environmental sex determination ?

A
  • Conservationists were trying to re-establish population of turtles
  • They didn’t know about environmental sex determination
  • Increased incubation temps and thus increased female total
  • boosted population with more females to lay eggs
37
Q

What groups are lepidosaurs?

A

Snakes and lizards

38
Q

Tuatara: Sphenodonta adaptations

A
  • New zealand (only found in islands)
  • Nocturnal - low body temp (counterintuitive)
  • Live in burrows with sea birds - waste produced by birds attracts arthropods that tuatara feed on
  • Active at night - possible adaptation for tuatara being nocturnal
39
Q

What is different about the Tuatara skull?

A
  • Diapsid skull - lower bar is a secondary addition - lost and reformed
  • 2 rows of teeth on upper jaw
  • 1 set on lower jaw that fits in between two top
40
Q

what are Squamates?

A

Lizards and snakes (not including the tuatara)

41
Q

How are snakes and lizard skulls modified?

A
  • Modified diapsid skull
  • Lizards bottom bar is lost
  • Snakes both bars are lost
42
Q

How are squamates skulls kinetic?

A
  • flexible
  • Wide gape
  • Not a powerful bite
43
Q

What are Amphisbaenians?

A
  • Clade of lizards that are adapted for burrowing
  • Reduction or loss of limbs
  • Akinetic skull
  • Inflexible skull used for burrowing
  • Skull doesn’t move at all
44
Q

What size are the majority of lizards?

A

80% are less than 80g

45
Q

What benefit is being small for lizards diet?

A
  • Can feed on insects
  • Large lizards tend to me herbivores
  • Exceptions - monitor lizards
46
Q

Komodo Dragon

A
  • Venom glands
  • Lowers prey blood pressure
  • Also contains anticoagulant
  • Bacteria theory is disproved
47
Q

How are fast moving lizards adapted to their locomotion and ventilation conflict?

A
  • Same muscles used for running are used for ventilation
  • Gular pumping - use of throat as an adaptation to pump air into lungs
48
Q

What is gular pumping in fast moving lizards?

A
  • An adaptation to the conflict between locomotion and ventilation
  • Use throat for lung ventilation when moving fast
  • Pump air into lungs
49
Q

How are Aboreal lizards adapted to this lifestyle ?

A
  • Zygodactylous - opposable toes
  • Prehensile tail
  • Eyes move independently of each other
  • Project tongue
  • E.g. Chameleon
50
Q

How have legless lizards evolved?

A
  • Evolved many times in lizards
  • Burrowing (short tails)
  • Surface dwellers (long tails)
51
Q

When did snakes branch off from lizards ?

A

Thought to have branched in the cretaceous period

52
Q

What is the Digging Phase Theory of snakes ?

A
  • lizards became subterratean and evolved into snakes
  • Early snakes are thought to be subterranean
  • Thoguht that they almost lost their eyes when they were subterranean and reformed them when they came back up to the surface
  • Differences in snake and lizard eyes
  • E.g. lizards tend to have eyelids whereas snakes dont
53
Q

Structure of a snake skeleton

A
  • Few neck and few tail vertebrae
  • Most of the animal is thorax
  • Thorax contains ribs
  • Lack pectoral and pelvic girdles
54
Q

Why do snakes have so much thorax?

A
  • Change in gene expression leads to more thoracic vertebrae - Oct4. If this gene is altered in mice they end up with more thoracic vertebrae.
  • Leglessness : Protein ‘sonic hedgehog’ (Shh) stimulates limb formation. Controlled ZRS gene
  • ZRS mutated in snakes
55
Q

What does the fossil Eupodophis show

Snake evolution

A

Fossil shows back but no front legs

56
Q

What does the fossil Tetrapodophis show?

Snake evolution

A
  • Four small limbs
  • Debate as to whether is an actual snake
  • Features suggest it burrowed
  • Fossil discovered in a collection by accident (named unknown fossil)
57
Q

How are snakes adapted for feeding?

A
  • Very flexible jaw
  • Many points of articulation
  • Don’t dislocate jaws (myth)
  • Teeth at back on throat pull prey along
  • Swallow small prey live
58
Q

How are snakes adapted for specialised feeding habits?

A
  • Egg feeders have specialised vertebrae for crushing eggs once swallowed whole
  • Mollusc eaters can hook out mollusc with teeth
59
Q

Constriction vs Venom (snakes)

Way of subduing prey

A
  • Venom immobilises prey
  • Constriction reduces blood flow to organs of prey.
  • Constrictors can detect heartbeat of prey and know when heart has stopped and they can stop squeezing
60
Q

What groups of animals are Archosaurs?

A

Alligators, Gharials and crocodiles (crocodylia)

61
Q

How are crocodilian teeth placed?

A

Thecodont (teeth fixed in sockets)

62
Q

What is the secondary palate of crocodilians?

A
  • Separates nasal passages from mouth
  • Allows breathing through nostrils when in water whilst mouth is under water
  • Gular valve means can open mouth underwater and valve stops water flowing into throat
63
Q

What are the pressure receptors in crocs called and what are they used for?

A
  • Integumentary sensory organs
  • Very sensitive
  • Use jaws for manipulation as limbs are very small and can’t use well
  • Use jaw for parental car - moving offspring and helping hatch
  • Use jaw like we’d use our hands - needs to be sensitive
64
Q

How do some crocs use lures to catch prey ?

A

Some use sticks to lure birds

65
Q

What skull formation do crocodilians have?

A

Diapsid

66
Q

How do archosaurs move?

A
  • Swim, crawl, walk & gallop
  • Ungulate body for swimming using tail
67
Q

what do archosaurs use their liver for?

A

able to move liver to ventilate lungs

68
Q

Other notes of archosaurs

A
  • Head shape varies
  • Use sound in social behaviour (territories, mating, parental care)
  • Lay eggs - Environmental sex determination
  • Play behaviour - cost energy but has no advantage

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