UNIT 4

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

2. Early Life

a. Factors needed for early life

FACTOR 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

FACTOR What was available in the early Earth

Organizing basic organic molecules

certain types of clay converts simple carbon-based molecules to complex ones at

hydrothermal vents

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

Feb. 2007

Energy

source geothermal energy from deep sea vents;

or solar energy both provide lots of energy

FACTOR What was available in the early Earth

Protective capsule

phospholipids will spontaneously form LIPOSOMES which are double layered

membranes

Reproductive

molecule

RNA can reproduce without any enzymes because of an effect called ribozymes

[DNA can only reproduce with enzymes]

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?

THREAT How early life coped by living in ocean

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

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

endosymbiotic life with chloroplasts

multi-cellular lifeforms

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

600 my 500 my 400 my 300 my 200 my 100 my 0.0

amphibians on landtrees appear

insects appear

600 my 500 my 400 my 300 my 200 my 100 my 0.0

reptiles appear

early dinosaurs

600 my 500 my 400 my 300 my 200 my 100 my 0.0

early mammals

first birds

dinosaurs disappear

600 my 500 my 400 my 300 my 200 my 100 my 0.0

first primates

WHEN ? WHAT ? WHY ?

530 million years ago

trilobites, brachiopods mollusk, echinoderm

change in sea level occurred at this time

4. Mass extinctions

WHEN ? WHAT ? WHY ?

440 million years ago

trilobites, echinoderms and nautaloids

sea levels rose rapidly & the beginning of the glaciation

365 million years ago

70% of all species vanished mostly in the sea and lakes

climate change, in this case a global cooling, was an important factor

245 million years ago

96% of all marine species were lost

fluctuations in sea-level, a change in ocean salinity and volcanic activity plus climate change

WHEN ? WHAT ? WHY ?

208 million years ago

sponges, cephalopod, brachiopod, insects and many vertebrate groups

climate change, seems to be important and, in particular, an increase in rainfall.

Showing the extent of ice in the most recent ice age

WHEN ? WHAT ? WHY ?

65 million years ago

85% of all species including all of the dinosaurs, many fish, plankton and many plants either died out completely or suffered heavy losses

a giant meteorite crashing into the earth, severely disrupting the earth's ecosystem

or volcanic activity, climate change, environmental pollution

WHEN ? WHAT ? WHY ?

Next? 50% of species including all plants and animals

Human induced climate change