UNIT 2 EVOLUTION

A. THE ORIGIN OF LIFE                                                                                                          

1. The Early Earth a. the earth was formed about 4.6 billion years ago b. it was hot, volcanic and bombarded by particles & cosmic rays from space c. it took about 100 million years to settle down

a. Factors needed for early life What was available in the early Earth Basic organic molecules CO2, NH4, SO2, CH4 were in the atmosphere; in the lab, adding steam & a spark to these gases in a Miller-Urey apparatus will result in thermal protenoids & other molecules of life

What was available in the early Earth FACTOR Organizing basic organic molecules certain types of clay converts simple carbon-based molecules to complex ones at hydrothermal vents

Feb. 2007 Most hydrothermal vents spew out water at 400oC, very acid and full of sulphur The Lost City vents water is 28oC  90oC and slightly alkaline with many dissolved carbonates The Lost City vent produces more organic molecules (eg. butane) that are the basis for many molecules in cells

Energy source geothermal energy from deep sea vents; or solar energy both provide lots of energy

What was available in the early Earth FACTOR What was available in the early Earth phospholipids will spontaneously form LIPOSOMES which are double layered membranes Protective capsule RNA can reproduce without any enzymes because of an effect called ribozymes [DNA can only reproduce with enzymes] Reproductive molecule

ScienceDaily (Oct. 31, 2007) — Remarkably, a solution of highly poisonous cyanide in ammonia, frozen solid in a refrigerator for 25 years, produced adenine, a necessary component of life.

What was the early Earth like?

How early life coped by living in ocean THREAT strong UV LIGHT – no ozone water stops UV light if they avoid UV light – how do they get solar energy? use deep sea vents as source of thermal energy therefore early life has to be CHEMOAUTOTROPHIC

How early life coped by living in ocean THREAT How early life coped by living in ocean EXTREME TEMPERATURES – lots of volcanoes water absorbs temperature changes although it remains at temperatures over 70oC DESSICATION – low atmospheric pressure so air very dry water is wet

4.0 by 3.0 by 2.0 by 1.0 by 0.0 the first prokaryote life forms prokaryote with internal membranes O2 abundant in the atmosphere endosymbiotic life with mitochondria multi-cellular lifeforms endosymbiotic life with chloroplasts

600 my 500 my 400 my 300 my 200 my 100 my 0.0 shelled invertebrates first vertebrates jawless fishes

600 my 500 my 400 my 300 my 200 my 100 my 0.0 plants invade land arthropods invade land jawed fish in seas

amphibians on land trees appear insects appear 600 my 500 my 400 my 0.0 amphibians on land trees appear insects appear

early dinosaurs reptiles appear 600 my 500 my 400 my 300 my 200 my 0.0 reptiles appear early dinosaurs

600 my 500 my 400 my 300 my 200 my 100 my 0.0 first birds early mammals

dinosaurs disappear first primates 600 my 500 my 400 my 300 my 200 my 0.0 first primates dinosaurs disappear

4. Mass extinctions WHEN ? WHAT ? WHY ? 530 million years ago trilobites, brachiopods mollusk, echinoderm change in sea level occurred at this time

sea levels rose rapidly & the beginning of the glaciation WHEN ? WHAT ? WHY ? sea levels rose rapidly & the beginning of the glaciation trilobites, echinoderms and nautaloids 440 million years ago

climate change, in this case a global cooling, was an important factor WHEN ? WHAT ? WHY ? 70% of all species vanished mostly in the sea and lakes climate change, in this case a global cooling, was an important factor 365 million years ago fluctuations in sea-level, a change in ocean salinity and volcanic activity plus climate change 245 million years ago 96% of all marine species were lost climate change, seems to be important and, in particular, an increase in rainfall. sponges, cephalopod, brachiopod, insects and many vertebrate groups 208 million years ago

Showing the extent of ice in the most recent ice age

WHEN ? WHAT ? WHY ? 65 million years ago a giant meteorite crashing into the earth, severely disrupting the earth's ecosystem 85% of all species including all of the dinosaurs, many fish, plankton and many plants either died out completely or suffered heavy losses 65 million years ago or volcanic activity, climate change, environmental pollution

WHEN ? WHAT ? WHY ? Next? Human induced climate change 50% of species including all plants and animals Human induced climate change