Diversity of life prework/notes

Age of the earth

4.54 Ga

age of the oldest fossils

3.9Ga

age of oldest vertebrates

360Ma

Limitations of early life fossils

Early organisms were microscopic, rare, and unlikely to preserve due to being soft bodied. much of the fossil record is also eroded

microfossil

traces in rocks 3.9Ga supposed to be prescence of bacteria

Evidence for early life

microfossils, chemical signatures, atmospheric composition, banded iron formations

Banded iron formation

layers of iron rich sedimentary rock caused by precipitation of oxidised iron as a result of the evolution of photosynthetic organisms

abiogenesis

spontaneous generation of life (speculated until the discovery of microscopic organisms

Hadean eon

Hot, with intense volcanic activity, greenhouse like atmosphere (water vapor, CO2, CO, H, CH4,NH3

Prebiotic soup hypothesis

The hypothesis that organic compounds could be formed from inorganic ones, and replicate to form organisms. Backed up by miller-urey experiment

Miller Urey experiments

Inorganic compounds were combined in an environment reflecting early conditions on earth, demonstrating the spontaneous formation of organic compounds - amino acids, hydrocarbons

Model for early life

The assembly of self replicating RNA from formation of amino acids, with competition between polymers leading to increased chemical efficiency. Spontaneous formation of membrane bilayers around these molecules led to the development of protocells.

Uncertainties about the model for early life 

Order, location, frequency, external forces encouraging formation e.g. hydrothermal vents, aggregation, meteorites

molecular clock

A method used to estimate the timing of evolutionary events by assuming a constant rate of mutation in certain genes

geological ages

the division of earth history based on patterns of sedimentary strata and their links to fossils

Dating of rocks and strata

relative dating, absolute dating

Relative dating

dating strata byestimated rock age. This is based on the comparison or correlation of rock layers and the fossils they contain.

absolute dating

use of radioactive isotopic dating which determines the actual age of rocks and fossils in years due to the long half lives of certain isotopes

Carbon dating

only works for organic material up to a few ten thousand years old

Minimum ages

Identified fossils provide a fixed point in time when we know they lived allowing a minimum age to be identified for related groups. this can be used to calibrate molecular clocks

Continental drift

Plate tectonics allow the earths crust to move over time, thus shaping continents, causing changes in climate, coastline, upwelling, and migration

First photosynthesis 

3.5Ga. at 3Ga significant amounts of oxygen began to produce and the great oxygenation event occurred 2.5Ga

Separation of major groups

roughly 2Ga, although dating is difficult due to lack of fossils and horizontal gene transfer. Eukaryotes split latest evidenced by bacteria endosymbionts

Origin of multicellular life

Appeared multiple times in various groups, starting with red algae 1Ga and soon after worm like animals (evidenced by fossil burrows)

Origins of fungi

1Ga, colonising land at 540Ma, and primarily aquatic until 250ma

Origin of animals

first fossil evidence 600ma in the Ediacaran period, representing motile, aquatic, soft-bodied organisms.

Cambrian explosion

550mya fossils become common (especially in burgess shale beds canada) with a rapid diversification of life forms, including carapace.

Vertebrate origin 

520ma, with jawless bony fish then occuring 480ma

Movement onto land:challenges

UV, dehydration, locomotion, reproduction

benefits of terrestrial environment

abundant oxygen

First plants on land

475ma, (algae there earlier) , with evidence from fossilized liverwort like plants. Colonisation in devonian 400ma, with vascular plants developing, increasing o2 amouonts and allowing for fire

Miller-urey experimental setup

1 water chamber , vapour went to → 1 gas chamber (NH3, CH4,H20). The gas chamber had +,- electrodes simulating lightening and providing energy for the synthesis of organic compounds, which were then condensed and went back to the water chamber. 

Coacervates

are clusters of aggregated organic molecules that can form in aqueous environments, displaying properties similar to living cells, and are thought to be precursors to biological life.

Operin and haldane theory

proposed that the early Earth's atmosphere and conditions were conducive to the formation of organic compounds from simple inorganic materials, leading to the origins of life.

Monophyletic

describes a group of organisms that share a common ancestor and includes all descendants of that ancestor, indicating a single branch of the evolutionary tree. Also known as a clade

Polyphyletic vs Paraphyletic

describes groups of organisms that do not share a single common ancestor (polyphyletic) versus groups that do share a common ancestor but do not include all descendants (paraphyletic).

Origin of flowers

angiosperms appeared in the early cretaceous 130 mya

Arthropods onto land

490mya (based on trackways) - common by 415mya with body fossils.

Vertebrates onto land

tetrapods 395mya (devonian) , amphibians 50ma later

Eyrops

extinct early amphibian 295ma (permian) 

First reptiles

amniotes 340mya (carboniferous) , sauropsid - 310mya

mammal origin

200ma - triassic (lineage split 100ma earlier). Molecular clocks suggest divergence of clades 100ma (cretaceous)

Repenomamus

cretaceous 125ma 

Origin of hominids

primates diverged late cretaceous 55ma, apes diverged 20ma, oldest homonids 14ma, genus Homo 2.5ma, Homo sapiens 0.4ma , modern human 200k ago

australopithecus (lucy)

small brain, tool use - evidence bipedalism

Human migration

migration out of africa, adaptig to (and affecting) environments as they traveled 

Ice ages

several have occured creating land bridges including for early humans. Most recent 11500ya

Laurasia

a supercontinent consisting of present-day North America, Europe, and Asia.

Gondwana

a supercontinent that included present-day South America, Africa, Antarctica, Australia, and the Indian subcontinent.