Unit 6 Biology

What are the two types of evolution?

microevolution and macroevolution

What was believed before evolution?

1. creationism

2. catastrophism

3. gradualism

4. struggle for existence

5. uniformitarianism

6. inheritance of acquired traits

7. intelligent design

Who was Charles Darwin?

an English Naturalist that went on a voyage to the Galápagos Islands.

Saw that different species of finches/tortoises/etc lived on different islands and had specific characteristics for that island

• developed his theory of natural selection to serve as the mechanism for how evolution occurs

• survival of the fittest

What is natural selection based on?

1. overproduction of offspring

2. variation

3. adaptation

4. descent with modification

What are the sources of variation?

1. random mutations (ultimate source)

2. genetic recombination during meiosis (crossing over)

3. migration (gene flow)

What do adaptations do?

• beneficial traits (adaptation) will become more common over time because organisms should live longer and thus be able to reproduce more

• this changes the gene pool

What is descent with modification?

a change in gene frequency over time

• natural selection leads to populations with new phenotypes adapted to new situations

• their traits should come from their ancestors

Beneficial traits should become more common over time

What is the general statement of evolution?

individuals do not evolve, populations do

What is allele frequency?

each allele has a frequency in a population’s gene pool

• the higher the frequency, the greater the allele is there (and the more common the trait is)

• it shows how frequently the allele (usually dominant or recessive) appears in the gene pool

What is the equation of allele frequencies?

p+q=1

p= frequency of the dominant allele

q= frequency of the recessive allele

What are the mechanisms of microevolution?

1. mutations

2. natural selection

3. genetic drift

4. gene flow

5. non-random mating (sexual-selection)

What are the effects of mutations?

• creates new genotypes and thus new phenotypes

  • changes the allele frequency in a population

• increases variation, which is a driving force of evolution

• can be harmful, beneficial, or neutral

What are the effects of genetic drift?

• rare alleles in a population will decrease in frequency while others increase

• often results in a loss of genetic variation

• changes may be more apparent in smaller populations

What are the causes and effects of gene flow?

• occurs during migration

• results in an increase in genetic variation in the population

What are the factors where evolution will not occur?

1. population is large

2. must be random mating

3. no migration

4. no mutations

5. no natural selection

if at least one of these conditions is not met, then the population is evolving

What is the HWE population?

p²+2pq+q²=1

p²= homozygous dominant

2pq= heterozygous individuals

q²= homozygous recessive

How does speciation occur?

• some sort of isolation must occur

• gene pools gradually become different and are no longer able to reproduce

  • at this point the 2 groups are different species

What is a cause of divergent evolution?

new environments caused differences to evolve in populations

What are the 5 branches of science evolution ties together?

1. paleontology

2. morphology

3. biogeography

4. embryology

5. biochemistry

evidence has also come from direct observation

What are transitional fossils critical for?

piecing together evolutionary history

What are homologous structures?

similar structure but different function due to being used in different environments

• result of divergent evolution

What are vestigial structures?

could be leftover from an ancestor that has used the structure, and thus could provide evidence of divergent evolution

What are analogous structures?

different structurally but same functionally, due to living in similar environments

• result of convergent evolution, therefore are not related

What is evidence in biogeography?

species in nearby geographic areas often resemble each other, with variation for their specific environments

• potential evidence of divergent evolution

What does biochemistry analyze?

DNA and proteins from different species allows us to compare similarities to predict common ancestry

• closely related species would have similar DNA sequences

What do pseudogenes provide evidence of?

divergent evolution

What is evidence from direct observation?

microevolution that has been directly observed due to occurring in populations with short life cycles that reproduce quickly

What are the levels of taxonomy?

1. domain

2. kingdom

3. phylum

4. class

5. order

6. family

7. genus

8. species

Who is the father of taxonomy?

carolus linnaeus

What happened 3.5 billion years ago?

the 1st life form (a prokaryote)

What happened 2.1 billion years ago?

the first eukaryotes evolved through endosymbiosis

What does endosymbiotic theory suggest?

over time, coevolution of the two prokaryotes occurred and eventually led to speciation and the 1st eukaryotes

What does phylogeny help with?

understanding that it is believed that all organisms share a common ancestor, and phylogeny works to piece together evolutionary history of relatedness based on shared inherited characteristics

What do phylogenetic trees show?

• branch points show a new species diverging from the common ancestor

• hypotheses are based on analyzing shared morphology, genes, and behaviors

What do phylogenetic trees classify?

• organisms into major taxa (groups) based on evolutionary relationships

• classifies groups of species in the order in which they descended from a common ancestor using homologous features

• any heritable traits (DNA, proteins, anatomical structures, etc) that are the result of divergent evolution

What can we learn from a phylogenetic tree?

• which groups are most closely related

• which groups are least closely related

• which group diverged first (longest ago)