The early Earth formed 4.6 billion years ago as a hot, volcanic planet bombarded by cosmic rays. Basic organic molecules could form in the atmosphere and hydrothermal vents, allowing the origin of life as early as 4 billion years ago in primitive prokaryotic cells. Early life faced threats from UV radiation and temperature extremes but adapted by living in the protective environment of oceans and using deep sea vents as an energy source. Over time, evolution led to eukaryotic cells with organelles like mitochondria, multicellular life, and eventually plants and animals colonizing land while mass extinctions periodically wiped out large portions of species diversity.

1. UNIT 2
EVOLUTION

2. A. THE ORIGIN OF LIFE

3. 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

4. 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

6. 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

7. Most hydrothermal vents spew out water at 400oC, very acid and full of
sulphur
The Lost City vents water is 28o
C 🡪 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

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

9. 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]

10. 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.

11. What was the early Earth like?

12. 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

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

14. 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-cellul
ar lifeforms

15. 600 my 500 my 400 my 300 my 200 my 100 my 0.0
shelled
invertebrates
first vertebrates
jawless fishes

16. 600 my 500 my 400 my 300 my 200 my 100 my 0.0
plants invade land
arthropods invade land
jawed fish in seas

17. 600 my 500 my 400 my 300 my 200 my 100 my 0.0
amphibians on land
trees appear
insects appear

18. 600 my 500 my 400 my 300 my 200 my 100 my 0.0
reptiles
appear
early
dinosaurs

19. 600 my 500 my 400 my 300 my 200 my 100 my 0.0
early mammals
first birds

20. dinosaurs
disappear
600 my 500 my 400 my 300 my 200 my 100 my 0.0
first
primates

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

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

24. 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.

25. Showing the extent of ice in the most recent ice age

26. 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

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