Evolution
Definition: Process of change through time
Theory of Evolution Provides an explanation for the
differences in structure, function, and behavior among life forms
Evolution is based on COMMON ANCESTORY!
One Common Ancestor - Protozoa
Evidence of Evolution
Fossils: Remains of organisms preserved in
sedimentary rock, amber, ice, or tar
Upper Strata – more complex organisms/youngest
Lower Strata – less complex/oldest
Comparative Cytology
The cell is the unifying structure for all living things
Organelles similar in most organisms
Comparative Biochemistry
Nucleic Acids similar in all organisms (DNA/RNA)
Similar proteins (enzymes, hormones) More similarities More closely related
Comparative Anatomy
Similarity in bone structure Homologous Structure: Same
structure different function EX. Arms of humans, flippers of whales,
wings of bat
Homologous Structures
Notice that the types and number of bones are relatively the same.
Comparative Embryology
Similar embryological structure
Common ancestry
***Mature growth is very different from embryological growth.
Comparative Embryology
Notice that as organisms develop they become more and more distinguishable from one another.
Parts that no longer serve a purpose
Structures were used in the past
Genes still produce these structures
Ex. Appendix, tail bone (coccyx)
Vestigial Structure:
Charles Darwin Origin of Species written in 1859
Studied finches, found differences on the Galopogos Islands
Theory of Evolution - evolution based on variation and natural
selection
**Natural Selection: evolution is controlled by nature rather than by people.
Theory of Evolution Based theories on species variation and natural
selection.- (There are 5 points to natural selection)
1.Overproduction- within a population more offspring are born than can possibly survive.
2. Competition- depends on number of individuals in a population struggle for survival
- compete for food, shelter, living space
Darwin (cont.)
3. Survival of the fittest- the “strongest” or best adapted to its environment will survive.
4. Reproduction- individuals that survive will reproduce and transmit favorable traits and variations to offspring.
Darwin (cont.)
5. Speciation- new species have evolved from a COMMON ANCESTOR
Weakness of Darwin’s Theory
Even though Darwin was able to tell us that there were many variations of all living things on the planet…..
-He could not explain why.
-Did not explain how variations arose.
Darwin’s Theory
Hugo DeVries
Hugo DeVries-
- Found that something called a mutation were the source of variation in a population.
- Favorable mutations among competing species resulted in modern species.
Modern Evolutionary Theory
The Modern Evolutionary Theory supports Darwin's theory of variation and natural selection but incorporates the reason for the variation (mutation).
What Produces Variation?
1. Variation: mutation and natural selection.
2. Mutations: spontaneous
3. Sexual reproduction - sorting and recombination of alleles.
Examples of Evolution in Modern Times
1. Peppered Moth: light vs. dark (industrialization
influence) Moth was originally light
in color a mutation occurred moth turned black at same time the trees were getting darker
because of industrialization, those that were dark blended into the trees better and
SURVIVED
2. Insect resistance to insecticide:
Insect gets a mutation and becomes resistant to the
insecticide Resistance is not in
response to insecticide.
(Insecticide=spray that kills insects)
3. Bacteria resistant to penicillin:
One bacteria becomes resistant to PCN bacteria reproduce
ASEXUALLY offspring are also resistant
Modern Evolutionary Theory (cont.)
-involves the struggle of organisms to survive and reproduce in a given environment.
Good traits will passed on and will increase in frequency within a population
Bad traits will decrease in frequency within a population
Geographic Isolation
Favors speciation (development of new species) by segregating a small group from the main population. Ex. Mountains, deserts, cities, bodies of
water.
Reproductive Isolation
As a result of geographic isolation, organisms become so different they cannot mate and produce fertile offspring therefore a new species evolves
2 Theories of Evolution Rate
Gradualism: - evolutionary change is slow, gradual and
continuous.
Punctuated Equilibrium: - long periods of stability interrupted by
significant change.
Gradualism Punctuated Equilibrium