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History of the Earth:DiversityMODULE 02: HISTORY OF THE EARTH: DIVERSITYUNIT 1: BIODIVERSITY

Objectives

At the end of this series of lectures you should be able to: Define terms.

Understand diversification and mass extinction events over geologic time.

Understand how climate change affects diversity over time.

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Fossil Record

Our guide to the biodiversity of the past. An imperfect guide:

Incomplete in time

Incomplete in space

Taxonomic bias

Ecological bias

Incompletely revealed

General Trends

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General Trends

Diversity of species on the planet has generally increased over geological time until the spread of humans 30,000 years ago Periods of increase

Periods of stasis

Periods of decrease

Diversification

Diversification is not equal in all taxonomic groups. (Evenness) One group tends to dominate

Replacement Mosses Ferns Conifers Flowering plants

Amphibians Reptiles Mammals

Often due to chance climate events, not necessarily competitive superiority

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Geologic Time Scale

Temperature over Time

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Precambrian

Procaryotic and Eucaryotic life arose Bacteria

Stromatolites

Vendian fauna

Fossilized embryos

Photosynthesis

Cambrian

First fishes, chordates

All major animal phyla (except Bryozoa).

Plants not as well represented mainly red and green algae

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Ordovician

Ocean Life Teems Cephalopods , mollusks, fishes,

trilobites, red and green algae.

Bryozoans first appear

Plant spores invade land (End Ordovician)

Mass Extinction Event 49% of higher taxa lost

Decrease of ocean levels due to glaciation of Gondawana

Gamma ray burst

Silurian

Coral reefs appear

Rapid radiation of fish Wide distribution of jawless fish

Appearance & radiation of jawed fish

Relatives of land centipedes and spiders appear

First vascular land plants

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Devonian

Age of Fishes Vascular plants diversify

Ferns, horsetails, and seed plants appear

First amphibians Wingless insects appear End Devonian- Mass Extinction Event

22% of families, 57% of genera, 75% of species lost

Drop in temperatures, sea levels, increased glaciation Initiated by bolide impact or

eutrophication?

Carboniferous

Diversification of insects

Amphibians dominate

Development of the amniotic egg

First reptiles

Tree ferns dominate tropical & temperate floras.

Conifers develop

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Permian

Amphibians dominate early Reptiles diversify

Therapsids (mammal-like reptiles) dominate late

Conifers diversify

End Permian- “The” Mass Extinction Event 90-95% of marine species lost, most

Therapsids lost Decreased ocean levels & increased

glaciation Bolide impact Increased volcanism

Triassic

First dinosaurs appear

True mammals appear

Turtles appear

Flowering plants appear during this period?

End Triassic- Mass Extinction Event 20% of families lost

Glaciation

Triggered by the release of gases from the Atlantic Ocean?

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Jurassic

Dinosaurs dominate & diversify

Cycads and conifers continue to dominate

Fish & ammonites are common in sea

Birds appear

Cretaceous

Dinosaurs continue to dominate and diversify.

Modern groups of mammals, insects, and birds appear.

First flowering plants appear and diversify.

Pterosaurs and birds probably competing

Primates appear

End Cretaceous – Mass Extinction Event 35-60% of families lost (lots of variation

among taxa)

Dinosaurs lost

Good evidence for bolide impact.

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Tertiary

Very diverse period post dinosaurs Good fossil record from this time

period.

Climatic shifts.

Modern orders of birds and mammals appear.

Modern families of flowering plants appear. First grasslands form.

Quaternary

Biota very similar to today’s biota.

Characterized by large mammals & birds.

Humans evolve & spread Diversity has been decreasing

since spread of humans