3 Cambrian to Cretaceous

Question 1

Marine Radiation of Fishes - Paleozoic

Answer 1

Cambrian saw the origin of Chordates

450-420MYA - jawed fish radiation ‘Gnathostomata’

Fish are split into 2 main groups - chrondricthyes = cartilaginous fish / osteichthyes = bony fish (sub groups - actinopterygii = lobe finned fish / sarcopterygii = lung fish)

Question 2

Enabling feature for jawed fish radiation - genome duplication

Answer 2

Early chordates had 2 genome duplication events

4 Hox gene clusters

Enables morphological complexities (jaws, limbs) —> Devonian

Question 3

Jawless fish to jawed fish timeline

Answer 3

100 MYA of stasis as ‘jawless fish’

Genome duplication enables complexity

Radiation of jawed fish and later tetrapods

Question 4

The Greening of the Land - Paleozoic

Answer 4

Land plant life cycle evolved from algal plants

In algae most of their life is spent in the diploid cell

Large change is the diploid phase

Question 5

Bryophytes - the early land plants (liverworts and mosses)

Answer 5

Long haploid phase, short diploid

No vascular tissue

Don’t requre soil

Evidence by fossilised sporangia

Mosses also evolves stomata (gas and water regulation)

Question 6

Land plants accompanies by terrestrial fungi

Answer 6

Evolution of desiccation-resistant fungal hypha from aquatic form

Hypothesised fungi enabled plant life on land through symbiosis

Fungal plant interactions essential for many bryophytes

Question 7

Plant death —> organic bearing terrestrial soil

Answer 7

Creates soil = breakdown of plant matter (fungal, microbial action) / soil enables the growth of larger plants

Bryophytes don’t need soil but do create soil

Paleo soil in the Devonian

Question 8

Vascular Plants (Devonian)

Answer 8

Phloem / xylem transport system

Bifurcating (branching) growth / increased size through lignification

Leaves and fronds —> above ground photosynthetic surfaces / evolved on multiple occasions

Vascular plants result in richer soil - PO4 / NO3 are fuel for plant growth (but may have poisoned oceans via eutrophication)

Question 9

Devonian Mass Extinction

Answer 9

75% in 3 million years (many taxa disappear)

Question 10

Land plant evolution accompanies by terrestrial arthropods

Answer 10

First insects - flightless / derived from Crustacea (in silurian)

Devonian - winged formed (+ millipedes / aranaea spiders)

Question 11

The Carboniferous - Paleozoic (age of coal)

Answer 11

Carboniferous rocks —> appearance of organic rich deposits

Coal beds have abundant plant and other fossils - large woody plants appear, alongside large ferns / derived from lowland marsh and wetland

Question 12

Paleozoic - Why did the increased deposition of organic carbon occur

Answer 12

Tall woody plants had become dominant —> wood Is rigid and plants can grow tall due to lignin = complex carbohydrate, decomposes much more slowly which results in more organic carbon buried and coal strata

Question 13

Palaeozoic - Impacts of high oxygen levels

Answer 13

Biological consequences —> insect giganticism (aerobic respiration is more efficient —> more growth)

O2 limits body size where diffusion supports gas exchange —> O2 content of water increases with latitude and decreases in saltwater —> larger fish found in cooler oceans

Fire - 10-20% of coal beds are charcoal based (common) wildfires

Question 14

Paleozoic- Carboniferous also saw radiation of tetrapods

Answer 14

Warm, wet climate, green terrestrial biome enables movement out of water

Amphibian lifestyle - still linked to laying eggs in water

Closest ancestors - lobe finned fish

Giganticism also seen in amphibian - dominated predators of the Carboniferous

Question 15

The Permian

Answer 15

Rise of reptiles and the Permian mass extinction

End of the Carboniferous / eaely Permian saw a period of drying —> one large land pass (Pangea)

This drying makes a poor environemnt for amphibians —> selection for water retention

Question 16

Adaptations of reptiles for life away from water (4)

Answer 16

1. Amniotic egg
2. Keratinous scales
3. Alteration in excretion
4. Internal fertilisation

Question 17

Adaptations of reptiles for life away from water - amniotic egg

Answer 17

zygote in fluid filled cavity / chorion and shell - able to gas exchange but retains water

Question 18

Adaptations of reptiles for life away from water - keratinous scales

Answer 18

water impermeable skin

Question 19

Adaptations of reptiles for life away from water - alteration in excretion

Answer 19

uric acid / utilise arid landscape areas

Question 20

Adaptations of reptiles for life away from water - internal fertilisation

Answer 20

Reproduction on land necessitates transition to internal fertilisation

Question 21

Permian also saw the rise of metamorphosing insects

Answer 21

1. Hemimetabolous development
2. Holometabolous development

Question 22

The Permian mass extinction

Answer 22

End of the Permian saw largest mass extinction event in fossil record ‘The Great dying’

Question 23

Causes of the Permian Mass Extinction

Answer 23

1. Occurred at the same time as very high volcanic activity in Siberia
2. Massive SO2, CO2 release
3. Ocean acidification
4. Reduced primary productivity
5. Death of consumers

Question 24

Does mass extinction hit evenly

Answer 24

No - in general large things die out more than small things and non-motile things die out more than motile things

Question 25

The Mesozoic

Answer 25

Age of dinosaurs origins of birds, mammals (and flowers)

252-66 MYA

Question 26

Why cant DNA be used to reconstruct biology of dinosaurs

Answer 26

The DNA is decomposed

Question 27

Scientists study the new remains to determin relationshios to other known species and genera

Answer 27

Comparisons are made between these and living animals —> reconstruct skeleton and lifestyle

Aspects such as size, movement, weight and shape can also be determined

Can also look at trackways of footprints and use principles of anatomy and biomechanics -> movement and running speed

Question 28

Thermal biology

Answer 28

SA/V ratio - retained heat - can’t tell behaviour (eg. Basking or metabolism) - try to use species today to infer what their behaviour was likely to be

Current idea is that dinosaurs were both endothermic and edothermic

Question 29

What does brain size indicate

Answer 29

Indicates cognitive complexity - birds and mammals have complex cognitive capacity

Question 30

Origin of mammals

Answer 30

220 MYA

Derived from synapsids (non-dinosaur reptiles, no living examples) / mammals remained a minor taxa during the age of the dinosaurs

Question 31

Origin of birds

Answer 31

160 MYA

Evolved from theropod dinosaurs during the Jurassic (165-150MYA)

Classic small, lightweight, feathered and winged body plan —> evolved over tens of millions of years of evolution rather than one burst of innovation

Many non-avian dinosaurs had feathers

Question 32

Origin of Angiosperm (flowering plants)

Answer 32

130 MYA

First fossils 130MYA —> fast growing compared to gymnosperms (conifers)

Initially wind pollinated / insect pollination (110 MYA)

Question 33

Origin of Plant and insect diversification

Answer 33

Massive plant diversification 100-70MYA —> resulted in 250k species today

Loss of gymnosperms in the tropics

Diversification in beetles

Question 34

Plants and their herbivores escape and radiate process

Answer 34

Plant group —> novel defences —> escaped herbivores colonise new niches —> radiates —> herbivore that establishes onto that group (creates large number of new niches that then radiate again and REPEAT)