Evolution: The belief that species change over time.
Hardy Weinberg showed that the allelic frequencies in a population do not change unless
evolutionary forces act upon this population.
Equations:
o p2+2pq+q2=1
o p+q=1
Evolutionary forces:
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Gene flow: the movement of alleles into or out of a population because of immigration or
emigration (respectively).
Mutations: DNA replication errors that add a source of variation.
Nonrandom mating: occurs when organisms select a mate for reproduction because of a
certain trait.
Genetic Drift: a sudden change in allelic frequencies in a population. It can occur because
of the bottleneck effect (when a population is reduced and only a few individuals survive,
allelic frequencies change) or because of the founders’ effect (when a new colony is
formed by a few members of another population). Small populations are more prone to
genetic drift.
Natural selection: occurs when individuals of a population are favored in nature because
of a specific trait they possess, which gives them an advantage over other individuals,
allowing them to survive and reproduce (passing down its traits to its offspring).
www.bio.georgiasouthern.edu
Endosymbiosis Theory: States that mitochondria and chloroplasts were originally bacteria
that were in a symbiotic relationship with a proto-eukaryotic cell. The proto-eukaryote then
engulfed these bacteria and evolved into the eukaryotic cells we now know.
learn.genetics.utah.edu
Evidence for this theory:
Fossil record suggests that there have been mass extinction periods in earth’s history.
Phylogenic trees: based on fossil record and DNA comparisons, the evolutionary relationship
among organisms can be determined.
science.kennesaw.edu
Carolus Linnaeus: came up with the modern classification system for organisms.
http://www.bio.utexas.edu/faculty/sj
asper/Bio301M/originsp.html
The four kingdoms:
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Protista- Organisms that do not fit in any other kingdom that are mostly unicellular.
ex. (protozoans, algae)
Fungi- Eukaryotic heterotrophs that digest food outside of their bodies ex. (yeasts,
mushrooms)
Plantae- A eukaryotic autotroph that produces food through photosynthesis. Ex.
(Lettuce, broccoli, pines, ferns, etc)
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Animalia- Multicellular eukaryotic heterotrophs that digest food inside of their bodies
and lack a cell wall. Ex. (Humans, bears, whales)
Speciation: The formation of a new species.
Causes of Speciation:
Allopatric Speciation/Geographic Isolation: Populations are separated geographically ex.
(mountains, valleys, glaciers)
Sympatric Speciation/Reproductive Isolation: Two populations do not breed with each other
because of their geographic isolation and eventually they become so different that they
cannot breed with one another.
Gradualism: A species can change gradually until it becomes a new species.
Punctuated Equilibrium: Periods of rapid change in a species followed by periods of little or
no change.
http://www.bio.utexas.edu/faculty/sj
asper/Bio301M/originsp.html
Sexual Selection: A species could be attracted to a mate my certain characteristics such as
color or behavior. Ex. (peacock)
http://www.shangralafamilyfun.com/
peacock.html
Vestigial Structures: Homologous structures that have no use or purpose. Ex. (appendix)
Homologous Structures: Structures from different species that share a common ancestor.
“Same structure different function.”
http://itc.gsw.edu/faculty/bcarter/his
tgeol/paleo2/homol1.htm
Analogous Structure: A structure that appears similar in two unrelated species most likely
caused by convergent evolution. “Same function different structure.”
http://bio3vo.wordpress.com/evoluti
on/
Biochemistry Provides Evidence of Evolution:
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Molecules like cytochrome C and hemoglobin are used in many organisms and are
similar in structure and have a similar sequence.
All organisms use the same genetic code, DNA.