History of Life

• How did all begin??

What are the theories that explain

life?

Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

3

D . 1 . 1

Big Bang• 13,600 years ago

• Galaxies are moving away from us

• Black hole areas of intense gravitational pressure

particles collide rise in

temperature

quarksProtons

neutronselectronsatoms

H He

(hellium)

Temperature fell

Matter concentrated

temperature

cooled down

WHAT DO YOU THINK EARLY EARTH WAS

LIKE?

• HOW OLD?

• 4.5 BILLION YEARS

• BIG BANG - GRAVITY CAUSES DUST PARTICLES TO CONDENSE

• METEORS FOR MILLIONS OF YEARS - HOW HOT WOULD THE EARTH BE?

• EARTH HAS TO COOL DOWN - STEAM ESCAPES AND RAIN ALLOWS COLLECTION OF WATER -EARTH NOW HAS……

• ATMOSPHERE OF AMMONIA, METHANE, WATER VAPOR, CO2, AND NITROGEN

• WHAT IS MISSING? No O2 Too reactive

1st organic molecules didn’t

oxidize

• The energy for forming the organic

molecules was provided by:

– frequent thunder storms and lightning strikes

– volcanic activity

– meteorite bombardment

– high temperatures due to

greenhouse gases

– UV radiation

(no ozone so was extreme)

The organic molecules may have been generated on

Earth or introduced from space????

HOW WERE THE FIRST CELLS MADE?

• DOES ANYONE KNOW FOR SURE?

• SPONATEOUS GENERATION VS BIOGENESIS

Tales of Miletus/Aristotle 4 elements

• FRANCESCO REDI

• LOUIS PASTEUR’S EXPERIMENT

LOUIS PASTEUR

Pasteur filled a flask with medium, heated

it to kill all life,and then drew out the neck

of the flask into a long S.

This prevented microorganisms in the air

from entering the flask, yet allowed air to

flow freely. If the swan neck was broken,

microbes could enter the flask and grow.

BiogenesisEarth’s atmosphere was ‘reducing’ in the

early days. It did not contain oxygen gas

until after plants started photosynthesising

The atmosphere

contained: Hydrogen

Nitrogen

Water vapor

Methane

Ammonia

Hydrogen sulfide

The gases came from

abundant volcanic activity

Primitive atmosphere + radiation

ORGANIC MOLECULES

C+H+O= CARBOHYDRATES

C+H+O= LIPIDS

C+H+O+N+S= AA

• ALEXANDER OPARIN - CREATION OF MACROMOLECULES WITHOUT OXYGEN (BIOGENESIS)

• STANLEY MILLER AND HAROLD UREY EXPERIMENT

COACERVATES

With RIBONUCLEIC

ACIDS (multiplication)

ORGANIC

MOLECULES

RAIN OCEANSLIPIDS

+PROTEINS

=

MEMBRANE

• FIRST BACTERIA AROUND 3.5 BILLION YEARS AGO

• SOME ARE CYANOBACTERIA - THESE ARE

PHOTOSYNTHETIC BACTERIA

• WHAT ARE THESE BACTERIA GOING TO PRODUCE?

• ALMOST 10% ABOUT 2.5 BILLION YEARS AGO

• WHAT TYPE OF CELLS ARE BACTERIA?

• WHAT TYPE OF CELLS ARE ALL OTHER ORGANISMS?

• WHERE DID EUKARYOTIC CELLS COME FROM?

• ENDOSYMBIOSIS

ONE CELL ORGANISMS NOW!

Their own

food+ O2

PROKARIOTS

UNICELLULAR

ENDOSYMBIOSIS

BEGINNING OF THE EUKARYOTIC CELLS

• EVIDENCE FOR ENDOSYMBIOSIS

• DNA

Mammals

Flatworms

Annelids

Insects

Coelenterates

Fish

Birds

Reptiles

Crustacea

Amphibia

Single celled

organisms

Monocots Herbs Shrubs Trees

Dicots

Flowering plantsConifers

Mosses

Liverworts

Algae

Ferns

Fungi

Multicellular

plantsMulticellular

animals

Mollusc

Life introduced from outer space!!!

Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

• Panspermia- “seeds everywhere”

– Life came from space on comets

• Hydrocarbons, amino acids, water(s) and bacteria

Fixism is is the theory that says that life on earth has

always been composed by the species we have today.

Creationism is a religious form of fixism. A supernatural

being created the world the way we see it.

Fixism vs Evolutionism

Binomial nomenclature/ father of

modern taxonomy

the rules of

heredity/ genes

Lamarck’s Theory

Fixism vs Evolutionism

• First Evolutionist

• Acquired traits can be inherited NO!!!

• Use and Disuse

• Adaptation

– Organisms change as their

environment changes

Darwin’s Theory

• Published “Origin of Species”

• Traveled around the world in the Beagle

• He proposed that:

– Organisms produce more offsprings than the available

resources can support

– Organisms fight for limited resources like food, territory, and

other necessities of life. Only those who survive can produce

their own offspring

– Variation exists within species.

– Natural Selection - The environment

selects organisms with beneficial traits

EVOLUTION

NATURAL SELECTION

ADAPTATION

Gradual change from one form to

another through a period of time

The environment selects organisms with beneficial

traits

A form modified to fit a changed

environment

Lamarck's theory

- The environment induces the organisms to change.

- These changes are always positive (perfection drive)

- Use and disuse.

- Inheritance of acquired characters (ALSO SHARED BY

DARWIN!!!)

Darwin's theory

- Pre-existing variation

- Not all the variations are equally adaptative in a given

environment.

-S truggle to survive: The best adapted survive and leave more

offspring:the next generation will be better adapted (survival of

the fittest)

Evidence of Evolution

• Any preserved part or tissue of an organism that

once lived.

FOSSIL

Types of Fossils

Casts

The mold is filled with another

material

Molds

Hard body structures

Imprints

Feathers and leaves that form impressions on

rocks

Petrified Fossils

When minerals replace the hard

parts of organisms

Biochemical Evidences

• Indicate that some

organisms have similar

DNA sequences, which

suggest common ancestry

DNA

VARIATION

ADAPTIVE

RADIATION

CONVERGENT

EVOLUTION

HOMOLOGOUS ORGANSANALOGOUS ORGANS:

OTHER EVIDENCE OF EVOLUTION

– EMBRYOS

– VESTIGIAL STRUCTURE

APPENDIX- COCCYX-PLICA

SEMILUNARIS(eye)- MUSCLES OF THE

EAR- GOOSE BUMPS-PALMAR GRASP

REFLEX

• GEOGRAPHIC ISOLATION

• REPRODUCTIVE ISOLATIONWHAT IS

SPECIATION?

A SPECIES is A group of individuals with similar features that

can interbreed (exchange

genes) and produce a fertile offspring

Who can say we are not relatives??