3 Cambrian to Cretaceous Flashcards
Marine Radiation of Fishes - Paleozoic
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)
Enabling feature for jawed fish radiation - genome duplication
Early chordates had 2 genome duplication events
4 Hox gene clusters
Enables morphological complexities (jaws, limbs) —> Devonian
Jawless fish to jawed fish timeline
100 MYA of stasis as ‘jawless fish’
Genome duplication enables complexity
Radiation of jawed fish and later tetrapods
The Greening of the Land - Paleozoic
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
Bryophytes - the early land plants (liverworts and mosses)
Long haploid phase, short diploid
No vascular tissue
Don’t requre soil
Evidence by fossilised sporangia
Mosses also evolves stomata (gas and water regulation)
Land plants accompanies by terrestrial fungi
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
Plant death —> organic bearing terrestrial soil
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
Vascular Plants (Devonian)
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)
Devonian Mass Extinction
75% in 3 million years (many taxa disappear)
Land plant evolution accompanies by terrestrial arthropods
First insects - flightless / derived from Crustacea (in silurian)
Devonian - winged formed (+ millipedes / aranaea spiders)
The Carboniferous - Paleozoic (age of coal)
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
Paleozoic - Why did the increased deposition of organic carbon occur
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
Palaeozoic - Impacts of high oxygen levels
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
Paleozoic- Carboniferous also saw radiation of tetrapods
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
The Permian
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
Adaptations of reptiles for life away from water (4)
- Amniotic egg
- Keratinous scales
- Alteration in excretion
- Internal fertilisation
Adaptations of reptiles for life away from water - amniotic egg
zygote in fluid filled cavity / chorion and shell - able to gas exchange but retains water
Adaptations of reptiles for life away from water - keratinous scales
water impermeable skin
Adaptations of reptiles for life away from water - alteration in excretion
uric acid / utilise arid landscape areas
Adaptations of reptiles for life away from water - internal fertilisation
Reproduction on land necessitates transition to internal fertilisation
Permian also saw the rise of metamorphosing insects
- Hemimetabolous development
- Holometabolous development
The Permian mass extinction
End of the Permian saw largest mass extinction event in fossil record ‘The Great dying’
Causes of the Permian Mass Extinction
- Occurred at the same time as very high volcanic activity in Siberia
- Massive SO2, CO2 release
- Ocean acidification
- Reduced primary productivity
- Death of consumers
Does mass extinction hit evenly
No - in general large things die out more than small things and non-motile things die out more than motile things
