Natural Selection (7.1-7.3)
What is evolutionary fitness?
The ability of an organism to survive and reproduce fertile offspring
List 2 types of evidence used to support the theory of evolution
Molecular
Geological
Geographical
Morphological
Fossils
State what each variable represents in the following equation:
p2 + 2pq + q2 = 1
p2 = frequency of homozygous dominant genotype
2pq = freq. Of heterozygous genotype
q2 = freq. Of homozygous recessive genotype
What is a phylogeny and is it always constant?
A phylogeny is a branched diagram showing the evolutionary relationships between lineages.
It is a hypothesis and can change due to new evidence.
Explain how greater variation allows for survival of a population against environmental stressors
More variation allows for the environment to have more traits to select upon. This means that when there are stressors in the environment there is a better chance that some individuals will possess a trait to help them survive
Name 2 biotic factors and 2 abiotic factors that can affect the rate of evolution
Biotic: predators, humans, pathogens
Abiotic: sun, temperature, pH, salinity, habitat
List the 3 pieces of evidence that support common ancestry in eukaryotes
Membrane-bound organelles
Linear chromosomes
Genes with introns
What are the conditions for a population to be at Hardy Weinberg equilibrium?
No gene flow
No genetic drift (large pop.)
No mutations
No natural selection
Random mating
What is allopatric vs. sympatric speciation?
Allopatric- speciation caused by a geographic barrier & exposure to different selective pressures
Sympatric- speciation NOT due to a geographic barrier
How old is Earth? When did life begin to form and what did the early atmosphere look like?
Earth is 4.6 bya
Life about 3.6 bya
Early atmosphere was hostile with very little oxygen (mostly ammonia, methane, and hydrogen gas)
Compare and contrast natural selection & artificial selection
Natural selection is where the environment selects traits that are more fit (reduced variation) whereas artificial selection is when humans select desired traits (increase or decrease variation)
Explain how antibiotic resistance provides evidence of continuing evolution
As bacteria are exposed to an antibiotic, they may randomly have a mutation that gives them resistance. These bacteria will be more fit, leave offspring, and the resistance gene becomes more common in the population.
A dominant allele is present in 72% of the population. What is the frequency of heterozygotes?
p= 0.72
q= 0.28
2pq= 2*0.72*0.28= 0.403
40.3%
Which group would be the descents from the ancestor at node A?
We expect all of these descendents to possess what from their common ancestor?
All descendants have shared derived characteristics from their common ancestor
If a red beetle is most fit for an environment made of lava rocks, would this beetle be fit in a lush environment? Explain how a trait can be beneficial to 1 environment but deleterious to another
The red beetle will most likely not be very fit in the lush environment. This means while this trait is beneficial in the lava rocks environment, if the environment were to change, the red beetle may not survive.
Explain how variation within molecules in cells connects to fitness of an organism
If one cell has a protein that another cell does not, and this protein is more advantageous, this cell will be more fit and thus this organism will be more successful
Provide 2 pieces of evidence that supports common ancestry of ALL organisms
All organisms have:
Describe the conditions under which allele frequencies would change in a population
Genetic drift (small pop.)
Mutations
Gene flow (migration)
Sexual selection
Natural selection
Explain how these 2 models illustrate the different rates of evolution
Model A shows gradualism (small changes over time)
Model B shows punctuated equilibrium (long periods of stasis followed by rapid change)
Explain the 3 assumptions of the RNA World Hypothesis
Genetic continuity was assured by replication of RNA
Base-pairing is necessary for replication
Genetically encoded proteins were not involved as catalysts
Describe the importance of phenotypic variation in a population
Phenotypic variation allows for all organisms to have unique traits and the environment can select which are more fit. If there was no phenotypic variation → no natural selection → no evolution
Explain the difference between homologous and analogous structures
Homologous structures are inherited from a common ancestor
Analogous structures have similar function but are not from a common ancestor (result of convergent evolution)
Why is the Hardy Weinberg Equilibrium principle used as a null hypothesis?
It provides a model under which evolution is not occurring. This can be used as a comparison to test whether evolution is happening in a population or changes are due to random chance.
Describe 4 of the mechanisms that drive speciation
Prezygotic barriers:
Postzygotic barriers:
Give 1 example of how plants are adapting to the changing climate
Flowering earlier
Conserving water
Opening stomata during the night to conserve water