the evolutionary story. a story of life... at the beginning atmosphere of carbon monoxide, carbon...
TRANSCRIPT
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 by-product 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 Drift1) 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!