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Origins of Biodiversity > Chordates > Flashcards

Chordates Flashcards

Lectures 20-23

1
Q

What are the 5 unique traits for chordates?

A

Notochord
Dorsal nerve cord that is hollow
Pharyngeal slits
Muscular post anal tail

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2
Q

What is a notochord?

A
  • Longitudinal flexible rod between nerve cord and digestive tube.
  • Provides support and flexibility
  • Replaced by vertebral column in higher vertebrates
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3
Q

What is the dorsal nerve cord?

A
  • Develops by invagination (closing) of dorsal ectoderm)
  • Develops into central nervous system
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4
Q

What is a Pharyngeal slit?

A
  • Allow water to exit body without going through digestive tract
  • In primitive chordates this is used for filter feeding and in lower chordates it is modified for gas exchange (gills)
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5
Q

What is the post anal tail?

A
  • Non chordates digestive tract extends throughout body
  • Provides propelling force in aquatic species
  • Causes concentration of sensors in opposite end
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6
Q

When and what were the earliest chordates?

A

Pikaia and Cathamymyrus, 540 mya.

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7
Q

Give a summary of Urochordata.

A
  • Sea squirts
  • Sessile filter feeder
  • Only have pharyngeal slits but LARVA have nerve cord, notochord and tail
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8
Q

Give a summary of Cephalochordates.

A
  • Lancelets
  • Plankton feeders who bury into sand
  • Swollen nerve cord in anterior tip (brain sort of)
  • On continental shelves
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9
Q

Give a summary of Craniata and the groups within it.

A
  • Pharyngeal slit modified into gills
  • Cephalophised
  • Include Haikouella (which have eyes & brains, no skull) and Myxini (Hagfishes)
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10
Q

Give a summary of Myxini.

A
  • Hagfishes
  • cartilaginous skull but no jaws or vertebrate
  • Have a notochord
  • Feed on sick/dead fish
  • Produce slime
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11
Q

What are the main differences between Vertebrata and Crianates?

A
  • More extensive skull
  • Vertebrate either partially or completely replaced notochord
  • Fins stiffed by rays
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12
Q

Give a summary of Cephalaspidomorphi.

A
  • Lampreys
  • Parasitic to fish
  • Cartilaginous skeleton and pipe around notochord which partially closes nerve cord
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13
Q

Give a summary of Conodonts and Agnathes

A
  • First examples of mineralisation
  • We have extensive tooth fossils of Conodonts from late Cambrian to Triassic
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14
Q

What are Gnathostomata?

A
  • Have a jaw
  • Anterior gull split supports are modified to the jaws
  • Increased mineralisation
  • Two sets of paired fins
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15
Q

Describe the two major extinct early gnathostomes.

A

Placoderms: Massive with big bony heads, first evidence of internal fertilisation.
Acanthodians: Smaller, less armoured.

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16
Q

Give a summary of Chondrichthyes.

A
  • Sharks, ratfish, rays
  • Cartilage and calcium skeleton
  • Helicoprion is a strange extinct shark with a spiral jaw to be able to grow new teeth.
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17
Q

Give a summary of Actinopterygii.

A
  • Ray finned fish
  • Fully mineralised
  • Homologous lungs and swim bladder
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18
Q

Give a summary of Sarcopterygii.

A
  • Lobe finned fish
  • Rod shaped bones surrounded by muscles in fins
  • Include Actinistia (Coelacanth) and Dipnoi (Lungfish which can breathe air)
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19
Q

Give a summary of Tetrapoda.

A
  • Have limbs and feet
  • Gill slit supports modified into eat bones
20
Q

What is the first Tiktaalik fossil?

A
  • 375 mya, structure between sarcopterygian and tetrapod fish
  • Gogonasus was found 380 mya
21
Q

What were the issues with conquesting land?

A
  • Cant breathe
  • Drying out
  • Fertilisation of eggs
  • Body weighs more on land
22
Q

Give a summary of Amphibia.

A
  • Larvae live in water, adults live on land and breathe through skin and lungs.
23
Q

Give a summary of Amniota.

A
  • Reptiles and mammals
  • Breathe through land
  • Embryo developed in membranes (eggs or internal) so no need for water stage.
  • Scales to protect against dessication.
  • Appeared 354 mya (Carboniferous)
24
Q

What are the scientific names for the groups of snakes, lizards and crocodiles?

A

Snakes/lizards = Lepidosauria
Crocodiles = Crocodilia

25
Q

Give a summary of Mammalia.

A
  • Produce milk for offspring
  • Endothermic
  • Skin covered in hair
  • Viviparous (embryo develops in parent)
26
Q

Give a summary of Synapsida.

A
  • Mammal like reptiles
  • No hair and oviparous
  • Dominant during Permian, only few survived the Permian extinction and they have become mammals.
27
Q

Give a summary of Monotremata.

A
  • Have hair and produce milk but no nipples
  • Oviparous
  • Platypus n that
28
Q

Give a summary of Marsupialia

A
  • Viviparous but tiny when born. Most of development is done in pouch latched onto nipple.
29
Q

Give a summary of Eutheria.

A
  • Placental mammals who are viviparous
  • Success credit to endothermy allowing independence from environment
  • Large brain sizes allow behavioural adaptation
  • Differentiation of teeth
30
Q

What are the five feeding groups of Eutheria?

A

Carnivores
Piscivores
Herbivores
Insectivores
Omnivores

31
Q

What is the most morphologically variable animal species on earth?

A

Dogs. Due to human breeding, not natural selection.

32
Q

Did feathers or scales evolve first?

A

Scales. Feathers evolved from scales, first for insulation and then for flight.

33
Q

Were dinosaurs endothermic?

A
  • Debated but we are sure of at least one group that were.
  • Evidence such as bone structure
34
Q

How did fish shape of mammals evolve?

A
  • Convergent evolution
35
Q

Give a summary of the order Primates.

A
  • Lemurs, monkeys, apes etc
  • Ancestors were small insectivores
  • Adapted for grasping with hands, feet and large brain.
  • Forward facing eyes
  • Omnivorous diet
36
Q

When did hominoids/ hominids first appear?

A

Oids: Candidates 20-15 mya. Key hominoid trait is lack of tail but this is hard to ell when the only fossil you have is a skull.
Ids: 76 mya, again not great fossils.

37
Q

What is the difference between hominids and hominoids?

A

HominOIDS: Gibbons, gorillas, chimps, human etc
HominIDS: All species more closely related to humans than chimps (Big brain and bipedal possibly due to forests being replaced by savannah)

38
Q

Give a summary of Ardipithecus.

A
  • 4.4 mya and 1.2m tall
  • Small brain size (3-400cm3)
  • Upright, grasping hands and feet
  • Possible direct ancestor
39
Q

Give a summary of Australopithecus.

A
  • 4 to 2.5 mya and 1.2-1.4m tall.
  • Brain size 4-500cm3
  • Fully bipedal so it evolved before large brain size.
  • Includes fossil Lucy
40
Q

Give a summary of Paranthropus.

A
  • 2.5 mya
  • 1.3-5m tall.
  • Big teeth and strong bones, probably herbivore. Brain size 550cm3.
41
Q

Give a summary of Homo habilis.

A
  • 2.5 mya
  • 600+cm3 brain size
  • First evidence of tool making/use
  • Later forms known as H. Ergaster (900cm3 brain size)
42
Q

Give a summary of H. erectus.

A
  • 2mya
  • 1100cm3
  • Descended from H. habilis and ergaster
  • First to migrate out of Africa.
43
Q

Give a summary of H. Neanderthalensis.

A
  • 350-200,000 years ago
  • Descended from H. erectus
  • Bigger brain than us (1500cm3+) and really heavy/muscular.
44
Q

What are the two models of how H. Sapiens populated the world?

A

Multiregional: One wave out of Africa and into Eurasia
Out of Africa Model: Descended from H. erectus/ergaster in Africa, with H. sapiens leaving Africa and replacing erectus in Asia/Neanderthals in Europe.

45
Q

Give a summary of H. floresiensis and ‘luzonensis’.

A
  • 1m tall, 400cm brain
  • 50-100,000 years ago
  • Evidence of fire and tools, as well as island dwarfism
    luzonensis: Discovered in 2019, we have no skull so not much info. Roughly same size as floresiensis.
46
Q

What are the costs of a big brain?

A
  • 18% of energy budget
  • Forces premature birth
  • Practical and social skills

Origins of Biodiversity (9 decks)

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