weeks 1 and 2

Question 1

order the periods of the paleozoic age from most far away to most recent

Answer 1

Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian

Question 2

what were the key extinction events in the mesozoic era?

Answer 2

1. pangea broke up and CO2 levels increased
2. KT extinction event wiped out dinosaurs and 40% of tetrapods

Question 3

what happened in the triassic, jurassic and cretaceous periods?

Answer 3

1. triassic - gymnosperms appear, dinosaurs evolve and radiate
2. jurassic - dinoasurs most prominent
3. cretaceous - angiosperms appear, dino’s extinct at end

Question 4

key features of hemichordates

Answer 4

• marine, inter-tidal
• gill pores
• dorsal nerve chord
• buccal diverticulum
• open circulatory system (glomerulus)

Question 5

key features of chordates

Answer 5

• notochord
• dorsal nerve chord
• post anal tail
• pharynx (throat)

Question 6

in cephalochordates, what is the hatschek pit and buccal cirri?

Answer 6

hatscheks pit - secretes mucus
buccal cirri - stops sediment from entering

Question 7

when did mineralised tissues appear? what was astrapis and its adaptations

Answer 7

• mineralised tissues appeared late cambrian period
• astrapis was a fish with mineralised tissues. It had a torpedo shape, gills, a bony plating and was jawless

Question 8

what were conodonts? give an adaptation

Answer 8

apatite microfossils seen between the cambrian and start of triassic.
* no gills

Question 9

give a feature of ostracoderms and suggest how it relates to their feeding habits

Answer 9

moveable mouth plates - good for filter feeding and eating soft bodied prey

Question 10

summarise the steps from jawless to jawed

Answer 10

• ancestral agnathans had unjointed branchial arches
• evolved into jointed arches to increase ventilation
• the mouth then closed the ventillory jaws - became jaws

Question 11

why did jawed fish have better movement, circulatory and sensory systems?

Answer 11

2nd hox gene duplication occurred and led to increased brain size and evolution of lateral line system

Question 12

give 3 features of the physiology of placoderms

Answer 12

hinged mobile jaw plate, bone and cartilaginous skeleton, seen during in Devonian period

Question 13

what were hybodonts?

Answer 13

hybodonts are extinct shark-like creatures which had terminal mouths and heterodont teeth

Question 14

how did sharks evolve to be better adapted through the mesozoic era? what stayed the same?

Answer 14

pectoral fins were rotated and became flexible. However they still had an amphyistilic jaw, terminal mouth, notochord and multi-cusped teeth

Question 15

what are ceratotrichia?

Answer 15

curvable fins made of protein allowing lift and stability to be generated

Question 16

in elasmobranchs, the teeth are modified from what?

Answer 16

teeth are modified from placoid scales

Question 17

what is the lateral line system and how does it work?

Answer 17

lateral line of pores from the snout to the tail. Allows sharks and fish to sense pressure changes using mechanoreceptors which trigger an anction potential

Question 18

what are the ampullae of lorenzini and how to they work?

Answer 18

ampullae of lorenzini are electroreceptors on the skin which detect miniscule differences in the electromagnetic field. Mostly found on the head. They are deep tubes with non-conductive walls but contain a conductive glycoprotein.