Transcript The Origins of Life & Cladistics

The Evolutionary Story
A story of life...
At the beginning
• Atmosphere of carbon monoxide, carbon
dioxide, nitrogen, methane, hydrogen,
ammonia, water vapour and little or no
oxygen
• Active volcanoes, lightning and UV radiation
from the sun were all very intense
How did life begin?
• Primary Abiogenesis
– Theory hypothesized in the 1920’s by both
Alexander Oparin and JBS Haldane
independently
– States that the first living things on Earth
arose from non-living material (organic
molecules).
1. Formation of Organic Molecules
Life beginnings cntd...
• 2) Small molecules joined into large ones such
as proteins and nucleic acids.
• 3) Molecules that could copy themselves
arose providing a basis for inheritance of
molecular info
• 4) The molecules became packaged within
mebranes (pre-cells).
Under the sea...
• Earth’s surface was too hot for pre-cells to
survive.
• Deep-sea hydrothermal vents probably best
place to supply energy and chemical raw
materials required for origin of life.
The oldest fossils
• Prokaryotic bacteria that could function without
oxygen (anaerobic).
• Chemoautotrophs- synthesize organic
molecules from inorganic materials without
needing light energy.
• Some chemoautotrophs must have released
oxygen as a by-product (Free Oxygen becomes
available).
• As raw chemicals are used up, an organism that
can photosynthesize and then use the byproduct to release energy evolved and became
adapted (aerobic).
• Stromatolites- thin layers of sediment bound
together into rocks by photosynthetic
prokaryotes (3.5 billion yrs ago)
The Prokaryotes
• Gave rise to first Archaebacteria and Eubacteria.
Endosymbiotic Theory:
How Eukaryotes Evolved?
•
Some prokaryotes lost their cell walls.
•
Engulfed another aerobic heterotrophic bacteria (but did not digest).
Support for Endosymbiosis
Mitochondria and chloroplasts are different
from other organelles
• Surrounded by 2 membranes
• Have their own DNA
• Replicate their own DNA and undergo division
independently from host cell
Continental Drift
1) Formation of Pangea
–
250 mill yrs ago plate movements brought all
land masses together into one
supercontinent (Pangaea).
–
Caused many environmental changes which
lead to the extinction of a number of species
2) Breakup of Pangea
–
180 mill yrs ago continents drifted apart and
each became a separate and isolated
evolutionary arena
–
Species on different continents diverged as
they adapted on the now separate continents
In Context
Phylogenetic Relationships
• Phylogeny- The evolutionary development or
history of a species or group.
• Phylogenetic Tree- A branching diagram that
represents the evolutionary relationships
among species or groups.
• Taxonomy- The science concerned with
classifying organisms.
Constructing a phylogenetic tree
• Structural Anatomy of organism’s body. Use
Homologous structures to establish
relationships.
• Molecular data. Compare genes (DNA) and
proteins expressed across organisms.
• Best trees are constructed by using supporting
evidence from multiple sources.
Constructing a Phylogenetic Tree
Cladistics
• Each evolutionary branch in a phylogenetic tree is
called a clade.
• Clades can nest within larger clades.
• All organisms within a clade must share
homologous structures (also called derived
characters) that do not occur outside the clade.
A Cladogram
• A phylogenetic diagram that specifies the
derived characters of clades.
Primate Phylogeny
• Primate: have grasping hands and feet with
opposable first digits.
Primate Phylogeny cntd.
• Hominoids- Large brains, no tails and swinging arms.
• Hominids- Ancestral species and humans that arose after
split from chimpanzees.
• Bipedalism- ability to walk on two feet.
Meet the family!