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VERTEBRATES > Intro and origins of verts > Flashcards

Intro and origins of verts Flashcards

1
Q

What percentage of all species are vertebrates?

A

4%

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2
Q

Two main groups of vertebrates

A
  1. Non-amniotes
  2. Amniotes

Both share some traits that have evolved individually (e.g. birds and mammals both evolved endothermy)

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3
Q

What groups of animals are non-amniotes and what are their similar features?

A
  • Bony fish, Lampreys & amphibians
  • Membranes come from the digestive tracts of the female
  • Tend to be aquatic
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4
Q

What groups of animals are amniotes and what features do they share?

A
  • Sauropsids and synapsids
  • Membranes come from the embryo: Extraembryonic
  • Tend to be terrestrial
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5
Q

What group are Vertebrates under? and what is their sister group?

A
  • Vertebrates are Chordates
  • Urochordates (sea squirts) are the sister group withing chordates.
  • Both are Deuterostomes
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6
Q

What is unusual about reptile phylogeny?

A

Not monophyletic

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7
Q

Examples of Convergent evolution

A
  • Pentadactyl limbs (5 digits)
  • Some have lost digits over time - horse
  • Loss usually due to evolution of fast running etc
  • Fusiform: Shape of porpoise, shark and ichthyosaur all simialr but evolved seperately.
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8
Q

Differences in amount of orders within the amniotes

A
  • Mammals 27
  • Birds 41
  • Reptiles 4
  • Amphibians 3
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9
Q

Earth’s period of fragmentation

A
  • During this fragmentation was when birds and mammals were diversifying
  • Fragmentation caused formation of many orders
  • Relationship between highly diverse habitat and diversity of tetrapods
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10
Q

What is a possible cause for the diversification of birds and mammals?

A

1. Extiction of dinosaurs

  • loss of main predators allowed them to move into new niches and diversify

2. Endothermy

  • Able to exploit cold environments
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11
Q

Size variation in vertebrates

A
  • Paedocypris (small fish) 7.9mm
  • Paedophryne amauensis (frog) 7mm
  • Male angler fish - sexual parasitism - 6mm (can’t live independently)
  • Blue whale = largest vert
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12
Q

How is the female angler fish is adapted to the sexual parasitism of the male?

A
  • Does not elicit an immune repsonse to male lacthing on
  • Change in gene allows with adaptation
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13
Q

Why is the killifish is specialised?

A
  • Fasted growth rate (reproduce at 17 days old)
  • Live in pools that can dry up
  • Eggs live in resting stage
  • As soon as there’s water they rapidly grow
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14
Q

Mimic octopus jaw fish adaptation

A

mimics the octopus (lives with the octopus)

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15
Q

Most vertebrates are large

A

High energetic existence

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16
Q

Most verts have jaws

A

Gulper eel - massive modified jaw

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17
Q

Many vertebrates are extinct

A
  • Tasmanian wolf (thylacine) - driven to extinction
  • Chytrid fungus - causing extinctions of frogs & toads
  • Possibly transmitted by humans - molecular makeup is the same across the world.
  • Cave catfish - very endangered. Only found in one cave in Namibia
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18
Q

Verbrate phylogeny

A
  • Deuterostomes
  • Within the chordate group
  • Urochordates (sea squirts) and cephalochordates also in this group
  • More closely related to the urochordates than the cephalochordates
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19
Q

Chordate features

A
  • Notochord
  • Dorsal hollow nerve cord
  • Pharyngeal gill slits - used for respiration (if retained)
  • Post-anal tail
  • Endostyle - structure found in pharynx. Believed to be homologous to the thyroid gland (concentrate iodine)

Have these at some point in their lifecycle

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20
Q

Lamprey endostyle

A

In larval stage is used for feeding (produces mucus), in adult form it metamorphoses into thyroid gland

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21
Q

What makes the vertebrates different from the inverts that have similar structures?

A
  • Vertebrae
  • Cranium
  • Embryological features: Duplication of hox genes
  • Development of the neural crest
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22
Q

Vertebrae

vertebrates are different from the inverts that have similar structures

A
  • Usually replaces notochord (has centrum and neural canal)
  • Notochord can still remain as intervertebral discs found between vertebrae
23
Q

Acceptions of fully formed vertebrae

A
  • Hagfish and lampreys: don’t have fully formed vertebrae.
  • Instead have rudimentary vertebral precursors (arcualia)
  • Lampreys – along body & dorsal
  • Hagfishes – tail region & ventral
  • Ancestor – dorsal & ventral
24
Q

Cranium

vertebrates are different from the inverts that have similar structures

A
  • Can be bony, cartilaginous or fibrous
  • Vertebrae and cranium make up the endoskeleton
  • Cartilaginous in early verts
25
Q

Embryological features

Duplication of hox genes

vertebrates are different from the inverts that have similar structures

A
  • Duplication of hox gene complex (homeobox genes)
  • Inverts chordates only have one hox gene cluster.
  • Ancestral jawless verts have 2 hox gene clusters.
  • Further duplication associated with the evolutions of other features e.g. jaw
  • 4 clusters = evolution of the jaw
  • Bony fish (teleost) - third duplication 7 clusters (one cluster lost)
  • Salmonids fourth duplication - 13 clusters (another cluster lost)
  • Duplication of hox genes may add to the complexity seen in verts
26
Q

Main hox gene duplication events

A
  • Origin of verts (2 clusters)
  • Jaws (4 clusters)
  • Teleosts (7 clusters)
  • Salmonids (13 clusters)
27
Q

Development of the neural crest

vertebrates are different from the inverts that have similar structures

A
  • Cells are migratory and multipotent - can move around the body and form in to any cell
  • Responsible for new structures (especially head)
  • Another germ layer - quadroblastic (4 body layers)
28
Q

Possible precursors of the neural crest in invertebrates chordates

A
  • Similar genes expressed in the 2 invertebrate chrodates during neural plate formation
  • Migratory cells in tunicates form pigment cells
29
Q

Placodes

vertebrates are different from the inverts that have similar structures

A

Give rise to complex sense organs
Unique to vertebrates
Homologs (similar genes) in invertebrate chrodates

30
Q

Brain

vertebrates are different from the inverts that have similar structures

A
  • Brain of verts is larger and has 3 parts (forebrain, midbrain & hindbrain).
  • Brain of amphioxus (invert chordate) is not divided but genes are similar except the front forebrain.
31
Q

Vertebrates have increased in body size, how has this effected them ?

A
  • Can’t rely on ciliary action or diffusion
  • Need organs systems to respire and process food etc
  • Higher metabolic rate than non-vert chordate
  • Can sustain anaerobic respiration for short periods of time
  • Allows rapid movement when needed (e.g. escaping predator)
  • Transition from filter feeding to active predaceous mode of life
32
Q

What do Mineralised tissues contain?

A
  • Didn’t appear early within the vertebrates
  • Contain hydroxyapatite (calcium and phosphorus) - more resistant to lactic acid after anaerobic respiration
  • Mineralised tissues – collagen fibres, proteinaceous tissue matrix and hydroxyapatite
33
Q

Types of mineralised tissue

A
  1. Mineralised Cartilage
  2. Bone
  3. Enamel, Enameloid and Dentine
  4. Cementum
34
Q

Mineralised Cartilage

Types of mineralised tissues

A
  • Cartilage that’s become mineralised
  • Tougher than cartilage
  • 70% mineralised
35
Q

Bone

Types of mineralised tissue

A
  • Highly vascularised (can be repaired)
  • Dermal bone (grown in skin).e.g. skull
  • Endochondral (forms within body)
  • only found in tetrapods and bony fish
  • Cartilage is replaced by bone.
  • 70% mineralised
36
Q

Enamel, Enameloid and Dentine

Types of mineralised tissues

A
  • Teeth
  • Exoskeleton
  • Dermal scales of cartilaginous fishes
  • 90-96% mineralised (tougher).
  • Teeth are stronger than bones.
37
Q

Cementum

Types of mineralised tissues

A
  • fastens teeth in sockets
  • 45% mineralised
38
Q

Origin of bone and other mineralised tissues

A

No mineralised tissues at the start of vertebrate evolution

  • There were basic units in early verts - Odontodes (dermal). found on skin of early verts
  • SIMILAR to Denticles - found in skin of sharks
39
Q

Why did mineralised tissues evolve?

A
  • Defensive structure
  • & Dermal armour - ostracoderms
  • Protected electroreceptors - more efficient at detecting prey.
  • Storage /regulation of phosphorus and calcium.

No one really knows - above are some theories.

40
Q

Earliest vertebrates

A
  • Conodonts - toothlike structures (look like mineralised tissues) - lots of debates regarding these (fossils of teeth like structures found within the throat). Current accepted theory is that it was more convergent evolution with verts
  • Ostracoderms - jawless verts, thought to be the oldest group of verts until recently.
41
Q

Environment of early vertebrate evolution: Originated in marine environment, how do we know this?

A
  • Paleontological - earliest fossil found in marine sediments.
  • Comparative physiology - invert chordates (and other deuterostomes).
  • Closest relatives were marine - suggests they were also marine.
  • Marine and body fluids isotonic to marine water.
  • Primitive verts (hagfish) marine and isotonic to marine water.
42
Q

Chordate features?

A
  • Notochord
  • Dorsal, hollow nerve cord
  • Pharyngeal (gill) slits
  • Post-anal tail
  • Endostyle
43
Q

What became modified to form the jaw?

A

The mandibular arch (enlarged)

44
Q

How many hox gene clusters are seen in ancestral jawless fish?

A

Two clusters
First duplication event

45
Q

What does 2 hox gene duplication events give rise to?

A
  • Evolution of the jaw
  • 4 hox gene clusters
46
Q

What did the third hox gene duplication event give rise to?

A
  • Teleost fish
  • 7 Clusters
  • One cluster lost
47
Q

What did the fourth hox gene duplication event give rise to?

A
  • Salmonids
  • 13 clusters
  • another cluster lost
48
Q

why are vertebrates referred to as quadroblastic?

A
  • 4 body layers
  • endoderm, ectoderm, mesoderm and neural crest
49
Q
A
50
Q

Differences in body structure between a generalised non-vert chordate and a generalised vertebrate

A

Vertebrates have:

  • More developed heart
  • Muscularised gut
  • Cranuim
  • Sensory organs
  • Endostyle into thyroid
  • Well developed muscle blocks in tail region
  • Muscularised pharynx
  • More developed organs
  • Gill slits supported by gill bars
51
Q

Evolution of mineralised tissue

Mineralised tissue

A
  1. Lampreys - unmineralised endoskeleton
  2. Ostracoderms (armored fish) - Exoskeleton (origin of mineralised skeleton).
  3. Bony fish - Mineralised endoskeleton. Retain exoskeleton (scales, Ray fins etc).
  4. Tetrapods - Reduction of exoskeleton in the trunk. Retained in the head (skull). Contains mineralised endoskeleton.
52
Q

Age of earliest vertebrate fossil?

A

530 mya

53
Q

How do we know that the oldest vert fossil is a vertebrate?

A
  • No mineralised tissue
  • Skull and skeletal elements made of cartilage
  • Dorsal fin
  • Sensory structures
54
Q
A

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