Download Evidence for Evolution

Evidence for Evolution
Evidence from dead organisms
Evidence from living organisms
Fossils – remains of dead organism
Preserved remains of organisms that lived a long
time ago
•Fossilized hard parts (most common) ex. Bones,
teeth, shells, spores, seeds etc
•Traces of fossils (indirect evidence), footprints,
leaf prints, tracks, burrows.
How does Fossilization occur?
• Organism becomes
buried in ash or
sediments
• Rapid burial and a lack
of oxygen aid in
preservation
• The organic remains
become infused with
metal and mineral ions
What Do Fossils Tell Us?
• Evidence for change through time
• Oldest fossil found – heterotrophic
bacteria 3.5 BYO
• Older fossils in lower layers of rock
Ancestor of the whale walked on land
• Younger fossils in higher layers
Evidence from Biogeography
Continental Drift
• Idea that the continents were once joined
and have since “drifted” apart
• Pangea: theoretical supercontinent:
Explains the worldwide distribution of
more ancient life 500-200MYA
• Laurasia and Gondwanaland: Explains
why certain life forms exist in the
northern land and some only in the
southern lands 180-200MYA
Evidence from Biogeography
 Antarctica has fossils of plants
and animals that shows that is
was once a warmer land
 The continents in the south have
unique life forms and fossils form
that of the Northern continents
 Why are kangaroos only found in
Australia
 Why are flightless birds only on S.
America, Africa and Australia
Evidence from Living things
Comparative Morphology
• Homologous features
• Analogous features
• Vestigial structure
Morphological
Divergence or
Adaptive Radiation
3
from a common
ancestor (so similar in
structure) but has
changed (different
environmental
pressures) to serve
different functions
1
PTEROSARUR
4
1
2
CHICKEN
3
Homologous
structures: evolved
2
2
STEM
1
2
REPTILE
3
4
3
PENGUIN
1
5
2
3
4
5
PORPOISE
1
2
BAT
3
1
3
4
4
5
2
5
HUMAN
Morphological Convergence
Convergent evolution
body wall (exoskeleton)
Analogous
structures: evolved
from different
ancestor (not similar
in structure) but
serves the same
purpose (same
environmental
pressures)
strong membrane
(extension of wall)
wing veins
Vestigial Structures
 Structures that were present
in the ancestor and had a
function – but is no longer
functional in the modern
organism
 Example snakes have tiny
pelvic bones shows that the
ancestor of the snake could
walk
 Humans have a tail bone,
appendix which were
functional in the ancestors
Comparative Development
• During development, each animal or
plant proceeds through a series of
changes in form
• Similarities in these stages are clues to
evolutionary relationships
Comparative Development
Comparative Biochemistry
• Kinds and numbers of biochemical traits
that species share is a clue to how closely
they are related
• All life contains DNA, makes proteins
using RNA and similar biochemical
processes
• More similarity means species are more
closely related
Comparing Proteins
• Compare amino acid sequence of proteins
produced by the same gene
• Human cytochrome c (a protein)
– Identical amino acids in chimpanzee protein
– Chicken protein differs by 18 amino acids
– Yeast protein differs by 56
Speciation & Natural
Selection
• Natural selection can lead to speciation
• Speciation can also occur as a result of
other microevolutionary processes
– Genetic drift
– Mutation
“Species are groups of interbreeding natural
populations that are reproductively isolated
from other such groups.” Ernst Mayr