Download Evidence for Evolution

EVIDENCE FOR
EVOLUTION
Evidence
from dead
organisms
Evidence
from living
organisms
FOSSILS – REMAINS OF DEAD ORGANISM
Recognizable evidence of ancient life
•Fossilized hard parts (most common) ex.
Bones, teeth, shells, spores, seeds etc
•Traces of fossils (indirect evidence),
footprints, leaf prints, tracks, burrows.
Fossilization
• 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?
• As a result of mutations, natural
selection, and drift, each species is a
mosaic of ancestral and novel traits
• All species that ever evolved are related
to one another by way of descent
• Differences and similarities between
fossils and living
How old are the fossils?
Radiometric Dating
parent isotope in
newly formed rock
after one half-lives
after two half-lives
Continental Drift
Evidence from Biogeography
Continental Drift
• Idea that the continents were once joined and
have since “drifted” apart
• Initially based on the shapes
• 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 180200MYA
EVIDENCE FROM BIOGEOGRAPHY
Evidence from Living things
Comparative Morphology
Comparing body forms and structures of
major animals and plants
• Morphological divergence
• Morphological convergence
• Vestigial structures
Divergent evolution
due to
Adaptive Radiation
3
1
PTEROSARUR
4
1
2
CHICKEN
3
Seen in Homologous
structures: evolved
from a common
ancestor (so similar
in structure) but has
changed (different
environmental
pressures) to serve
different functions
2
2
STEM REPTILE
3
2
3
PENGUIN
1
4
1
5
2
3
4
5
PORPOISE
1
2
BAT
3
1
2
3
4
5
4
5
HUMAN
MORPHOLOGICAL CONVERGENCE DUE TO
CONVERGENT EVOLUTION
Evidence in Analogous
structures
 Evolved from different
ancestors
 But serves the same
purpose
 Different ancestry but
similar function
Q: Which structures
here show convergent
evolution and which
show divergent?
VESTIGIAL STRUCTURES
Body parts that had
a function in the
ancestor but not
anymore
Evidence of descent
from a ancestor that
used those parts.
Ex. Pelvic bones in
snakes
Human appendix
etc.
Comparative Development
• During development, each animal or plant
proceeds through a series of changes in
form
• Similarities in these stages may be clues
to evolutionary relationships
• Mutations that disrupt a key stage of
development are selected against
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