5-5-Life on Land: From the Cambrian to the Cretaceous.

what is marine radiation of fishes?

talk about fish…

a)during the Cambrian 

b)during the silurian diversification

c)talk about the duplication of hox genes from early chordates 

- diversification of fishes in the sea

-cambrian saw the origin or chordates which have a backbone/spinal cord

• (eg. Agnathas = jawless fish)

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Siluran diversification of fishes (major diversification of fish)

• Gnathostomata appeared (jawed vertebrates with paired limbs )

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-early chordates had 2 genome duplication events

• this means the entire set of genes were copied twice 

• early chordates had a single hox gene cluster (decide where the head/tail/limbs develop)

• 1-first duplication 2 hox clusters

• 2-second duplication 4 hox clusters

• this made the development of jaws/complex body structures

DEVONIAN

why did life not occur on land before?

-no ozone layer so UV made land inhospitable

-ozone forms when O2 split by UV and them combines with molecular oxygen

• O2=O+O

• O2+O=O3

-As oxygen rose to 20% ozone layer formed

how did land plant life evolve?

-land plants evolved from green algae called charophytes

-algae have alternative generations

• haploid stage (DOMINANT) (n) producing gametes

• diploid stage (2n) producing spores

-Land plants have a more dominant diploid stage

what is an example of an early land plant ?

-bryophytes (mosses/liverworts)

• long haploid phase

• no vascular tissue (xylem/phloem)

• no soil needed

• rhizoids (tiny roots cling to surfaces)

-mosses evolved stomata

DEVONIAN

how did fungi form?

-ancestors were aquatic forms

-on land they had a symbiotic relationship with mychorrihazea (fungi gave water/minerals,plant gave sugars)

how did soil form?

-mosses/liverworts die/decay they add humus to rock

-this allowed plants/fungi/microbes to grow

a)what are key features of vascular plants?

b)what are the consequences when a vascular plant grows?

-phloem/xylem lead to…

• bifurcating (branching)

• lignification (inc size/strength from lignin)

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• roots must be deeper (degrades rock/minerals release in rock)

• phosphate/nitrate can cause eutrophication (first Devonian extinction)

how did land plant evolution accompany terrestrial arthropods?

-first insects were flightless and derived from crustaceans (silueran period )

-in the Devonian period winged species /spiders/millepedes formed

what is the carbinefrous period?

why did it occur within this Time period?

what are the consequences of this (carbon sink)

-all coal formed

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-tall/woody plants became dominant 

-became tall due to lignin and this makes it a slow decomposer (no lignanases to break down)

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• lead to a rise in O2 

• carbon was locked away in coal and not returned as CO2 in the atmosphere

how did the carboniferous lead to the radiation of tetrapods 

-TETRAPODS (vertebrates with 4 limbs)

-warm,wet climate, green terrestrial environment (moved out of water)

-amphibian-like (laid eggs in water)

what is the the permian period

what adaptations do reptiles have ?

-dry period/hot climate (favouring reptiles)

-large landmass (Pangea)

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-amniotic eggs

• egg with shell/membrane to prevent drying out

• 1-allows gas exchange and is waterproof

• 2-no need to lay eggs in water so reptiles find drier environments

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-have scales (water insoluble)

-uric acid secretion (minimal water loss)

-internal fertilisation

what occurred during the permian mass extinction?

-largest mass extinction in fossil record

-high volcanic activity

• CO2/SO2 release

• ocean acidification

• reduced primary productivity

• death of consumers

the mesozoic (age of dinosaurs)

a)how do we study dinosaurs (behaviour/evolution)

b)how can we determine the biology of extinct species 

c)are dinosaurs cold/warm blooded?

-study remains and compare to other known species/genera 

-comparisons are made between these and living animals (recontruct skeleton/lifestyle)

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-movement/running speed

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-ectothermic (cold blooded uses environment)

-endothermic (warm blooded uses metabolism)

-dinosaurs in the middle?

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talk about features of hadrocodium

-hadrocodium (closest relative class of mammalia)

-nocturnal,less chances being eaten (had endothermic responses to aid this )

-good hearing due to having males-incus-stapes

how did birds evolve

-evolved from theropod dinosaur

-two legged,meat eating

when did flowering plants (angiosperm) evolve

-fast growing compared to gymnosperm

-initially wind pollinated

-insect pollination dominant

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-massive plant diversification

1- gymnosperm loss

2-diversification of beetles