Download Origins of life on earth

ORIGINS OF LIFE ON
EARTH
Alex Bariahtaris
The First Cells on Earth

Cells can only form from other cells
 Pasteur

experiment
Claims of first cells 3.8 billion years ago
 Bacterial
 Rocks
fossils date from 1.9 billion years
in Greenland indicate presence of oxygen (3.8 billion
years ago)
Requirements of Life on Earth


Even prokaryotic cells are intricate
Four essential processes for formation of life
 Chemical
reactions>> organic molecules
 Organic molecules>> polymers
 Ability of polymers to self-replicate
 Development of membranes

Only way to produce cell-like structures
Miller and Urey Experiment


Attempted to prove spontaneous formation of life
Created conditions that were similar to those
believed to exist pre-life
 Electrical

discharges/boiling and condensing water
Organic compounds, amino acids formed
http://www.mhhe.com/cgibin/netquiz_get.pl?qfooter=/usr/we
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Prokaryotes and Eukaryotes

Membranes needed to form cells
 Phospholipids
naturally group together, form layers
 Process forms membrane bound structures known as
protobionts

Endosymbiotic theory: mitochondria and chloroplasts
evolved from prokaryotes
 Both
structures grow, divide like cells, genetic structure
http://www.ib.bioninja.c
om.au/options/optiond-evolution-2/d1origins-of-life-onearth.html
Species/Speciation

Separate, unique population capable of
interbreeding
 Controversy:

sibling species, asexual repro
Formation of a new species, isolation of gene pool
 Allopatric
(geographic separation) and Sympatric (no
interbreeding)
Evolutionary Trends

Adaptive radiation: organisms find different roles
 Different

advantage for different organisms
Divergent/Convergent Evolution
 Divergent,
species evolve very differently
 Convergent species show striking similarities

Punctuated equilibrium rate of evolution
 Consistent
with environmental conditions
http://www.rocklin.k12.ca.us/staff/
pmorrison/Biology/2007BioAgend
as2ndSemester/BioAgenda3-3108.htm
Human Origin and Evolution

Humans classified as primates, similar anatomical
features
 Grasping

limbs, mobile arms, upright posture, etc.
Homo sapiens are only existing hominid
 Fossils
have shown evolutionary trends
 Increasing brain size in relation to body
Classification/Phylogeny

Arranging organisms into groups is advantageous
 Species
Identification
 Predictive Value (other species in similar groups)
 Evolutionary links (similar ancestors)


Also artificial classification, based off of one
specific characteristic
Phylogeny compares structures of proteins and
other biochemicals
Citations

Allott, Andrew. Biology For The IB Diploma: Standard
and Higher Level.
Oxford: Oxford UP, 2007, Print.