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STUDY GUIDE- EVOLUTION
Evolution: the process by which species change over time. (requires thousands or millions of years)
Individuals do NOT evolve, populations do!
Artifical Selection : when humans breed animals to have certain desired traits. (ex. Dogs)
Natural Selection : survival of the fittest: the driving force behind evolution
1. Over Production of Offspring : more offspring produced than can survive (increases competition)
2.Variation: (diversity) Some traits are more favorable than others
3. Selection for Adaptations : organisms that are better adapted:
+ will survive
+ will reproduce
+ will pass on their adaptation
4.Descent with Modifications: more individuals will have successful traits in following generations.
Fitness: measures how much a trait will contribute to reproductive success. Survive and Reproduce!
Microevolution: evolution on a small scale, with a population
Macroevolution: evolution on a large scale, involved many different species
Genetic Variability: a variety of genotypes and phenotypes that can lead to evolution - Causes:
1. Genetic drift: rare alleles disappear from a population
2. Gene Flow: alleles enter and exit a population (immigration and emigration)
3. Natural Selection: traits that increase fitness are selected for, unhealthy traits are selected against
4. Mutation: errors or changes in DNA (Important for genetic diversity!)
5. Non-random mating: mates are chosen due to specific qualifications (ex. Peacock feathers)
Speciation: forming a new species from a pre-existing one (species = able to breed together, same gene pool)
1. Behavioral Isolation – different mating rituals (dance vs sing)
2. Temporal Isolation – different mating seasons (spring vs summer)
3. Geographic Isolation – separated by a mountain range or river
4. Reproductive Isolation – the sex cells are incompatible
Patterns of Evolution
Gradualism: gradual change in a species over time (Ex. Giraffe)
Punctuated Equilibrium: abrupt and quick change in a species, due to environmental pressure
(Ex. Dark and Light moths due to factory pollution)
Divergent Evolution
Species diverge (split off) from a common ancestor
Similar characteristics that help them survive in a different niche
Homologous structures
Ex. Trunk on an elephant and trunk on a Wooly Mammoth
Homologous structures: similar traits resulting from common ancestry
(ex. similar bones in limbs of different animals)
Convergent Evolution
Develop similar characteristics due to similar environments
They are NOT closely related , no common ancestor
Develop analogous structures
Analogous structures: structures similar in function, but with different evolutionary origins
(Ex. Wings of a bat and wings of a butterfly)
Coevolution: when 2 species evolve together. (Ex. Faster lion = faster zebra)
Evidence of Evolution
Anatomy
Analogous structures due to convergent evolution (no common ancestor)
Homologous structures due to divergent evolution (common ancestor)
Vestigial structures - structures with little or no function to the organism.
(Ex. Wings on an ostrich, appendix in a human)
Embryology – the study of embryonic (pre-birth) development
Similarities are more evident in earlier forms of the zygote
More similarities in embryos = the more closely related the organisms.
Paleontology – the study of pre-historic life
Fossil records = see a pattern of gradual change.
The fossil record is NOT complete, many organisms do not form fossils.
The older the fossil, the less resemblance there is to modern species
Transitional fossils – show links between groups of organisms
Biochemistry study of genes and proteins
More similar the DNA and amino acid sequence (protein) = more closely related
Example:
102 103 104 105 106 107 108 109 110 111 112 113 114 115 116
Human
Chimp
Gorilla
Rhesus
Horse
Kangaroo
ASN
ASN
ASN
ASN
ASN
ASN
PHE
PHE
PHE
PHE
PHE
PHE
ARG
ARG
LYS
LYS
ARG
LYS
LEU
LEU
LEU
LEU
LEU
LEU
LEU
LEU
LEU
LEU
LEU
LEU
GLY
GLY
GLY
GLY
GLY
GLY
ASN
ASN
ASN
ASN
ASN
ASN
VAL
VAL
VAL
VAL
VAL
ILE
LEU
LEU
LEU
LEU
LEU
ILE
VAL
VAL
VAL
VAL
ALA
VAL
Human and Chimp = 0 amino acid differences
(most related)
Human and Gorilla = 1 amino acid difference
Human and Kangaroo = 6 amino acid differences (least related)
CYS
CYS
CYS
CYS
LEU
ILE
VAL
VAL
VAL
VAL
VAL
CYS
LEU
LEU
LEU
LEU
VAL
LEU
ALA
ALA
ALA
ALA
ALA
ALA
HIS
HIS
HIS
HIS
ARG
GLU