Explain how homologous structures provide evidence of evolution.
Homologous structures show that they have one trait, usually used for different functions, that is from one common ancestor.
If there are 2 different alleles for a gene that determine a trait, and the frequency of the dominant allele in the gene pool of a population is 0.45, what is the frequency of the recessive allele?
0.55
Describe how gene flow leads to changes in allele frequencies of a population (i.e., what is gene flow?).
Gene flow is when a species goes to a new area, spreading its genes. This decreases the allele frequencies as the animals adapt to their new environment.
Falling sea levels separate a species of fish into two populations that are divided by land. This is an example of ____________ isolation.
geographic
genetic change in living things over generations
Evolution:
the time it takes for half of the atoms in a sample to decay into another element
Half-life:
inherited characteristics that increase the fitness of individuals in a SPECIFIC environment
Adaptation:
all genes/alleles in a population
Gene Pool:
migration of individuals b/w populations
May reduce genetic differences in populations
Gene Flow:
populations are separated by a geographic barrier (river, mountain, ocean, etc)
Geographical Isolation:
unrelated organisms evolve similar adaptations (analogous structures) in response to similar selection pressures
Convergent Evolution:
Explain how vestigial structures provide evidence of evolution.
Vestigial structures give evidence for evolution as they do not have a function, showing that one of their previous ancestors did need them.
Identify FOUR causes of microevolution in a population.
Four causes of microevolution are natural selection, genetic drift, gene flow, and mutations.
Explain why darker skin is an adaptation in humans near the equator.
People who live closer to the equator have the adaptation of darker skin to protect them from UV radiation.
According to the fossil record, there have been several mass extinction events in the history of life on Earth in which a majority of species went extinct. Explain why they led to adaptive radiation in the surviving species.
The surviving species filled the niches that were left over from the extinct species.
similar structures/features inherited from a common ancestor
Changes over time resulted from exposure to dif environmental selection pressures
Ex: forelimbs in 4-limbed vertebrates,
Homologous structures:
spp tend to be more similar to other spp living nearby than to spp living in similar environments
Suggests descent from a more recent common ancestor
Biogeography:
the ability to survive & reproduce
Fitness:
number of times an allele occurs in a gene pool compared to other alleles for the same gene/trait
Allele Frequency:
Directional/Stabilizing/ Disruptive Selection
differences in reproductive strategies
Behavioral Isolation:
2 species evolve in response to their interactions w/ each other
Ex: predator & prey, flowers & pollinators
Coevolution:
Explain why fossils, especially transitional fossils, provide evidence of evolution.
These fossils show changes from ancestral species to their modern species.
Highlight the correct answer: Genetic drift INCREASES / DECREASES genetic variation in a population.
DECREASES
Explain why lighter skin is an adaptation far away from the equator.
People who live farther from the equator have the adaptation of lighter skin as there is much less UV radiation.
Explain how convergent evolution has led to analogous structures in species that are distantly related and did not inherit them from a common ancestor.
If the species are faced with similar selection pressures they might evolve into similar adaptations.
similar structures used for the same function that evolved independently from different ancestral species (spp) who faced similar selection pressures
Ex: wings of bats & birds, fins of sharks and whales
Analogous structures:
hypothesized that evolution results from inheritance of acquired characteristics developed thru use and disuse during an organism’s life
Jean-Baptiste Lamarcke:
an environmental factor that causes certain traits to be more or less advantageous, leading to changes in the frequency of those traits over generations.
(e.g., weather patterns, food scarcity, number/type of predator/prey)
Selection Pressure:
change in allele frequencies due to chance – can lead to reduced genetic variation
Genetic Drift:
selective breeding of plants & animals by humans
Artificial selection:
reproduce at different times of day/year
Temporal Isolation:
Molecular evidence is the most reliable source of evidence of evolution. Describe how DNA, RNA, and proteins can be analyzed to determine how closely related organisms are.
The more DNA, RNA, or AA that two species have in common usually indicates more closely related species.
Describe the bottleneck effect.
The bottleneck effect results from a big decrease in the size of a population.
Natural selection for a polygenic trait can lead to directional, stabilizing, or disruptive/diversifying selection. Each type of selection can cause the normal distribution of phenotypes (a bell curve) in the original population to change based on which individuals in the population have the highest fitness in response to a selection pressure, as seen in the figure below. Use the figure to answer the questions to a-c.
Which shell color(s) had the highest fitness in the population that underwent stabilizing selection?
Which shell color(s) had the highest fitness in the population that underwent directional selection?
Which shell color(s) had the highest fitness in the population that underwent diversifying (disruptive) selection?
What is ALWAYS necessary in order for two populations to undergo speciation?
Which shell color(s) had the highest fitness in the population that underwent stabilizing selection?
The medium brown shell color.
Which shell color(s) had the highest fitness in the population that underwent directional selection?
The darker brown shell color.
Which shell color(s) had the highest fitness in the population that underwent diversifying (disruptive) selection?
The light and dark brown shell color (not the medium).
During speciation, it is necessary to have reproductive isolation.
Identify TWO examples of coevolution in which two species evolve in response to one another.
Predators and prey.
Flowers and pollinators.
have no function, suggesting they were inherited from an ancestral spp in which they did have a function
They remain in today’s spp because they do not decrease the ability to survive & reproduce
Ex: pelvic bones of whales
Vestigial structures:
In 1859, ______________ presented his case for natural selection in his book, ______________.
Charles Darwin
The Origin of Species
individuals better suited to their environment survive & reproduce most successfully
Natural Selection (survival of the fittest) –
results from a drastic decrease in population size
Bottleneck Effect:
formation of new species
Results after a pop. splits into 2 populations that evolve differently
Speciation:
large-scale evolutionary patterns that result in speciation
Macroevolution:
What is the benefit to having genetic variation among members of a species?
Genetic variation makes adaptations become more likely, which gives a species a better chance of survival.
Describe the founder effect.
The founder effect results from a small group of the population colonizing a new area.
Two species of frogs look almost identical and live in the same area but do not interbreed because the mating calls of the male frogs of each species are of different frequencies and only attract females of the same species. This is an example of _____________ isolation.
behavioral
This series of pictures shows natural selection occurring in a population of cacti over a period of several months.
Identify the selection pressure for the cactus population.
Identify the adaptation in the cactus population.
Describe how natural selection occurred in the population of cacti over time in THREE STEPS.
1. Animals eat the cacti.
2. Cacti with spikes on them.
3. 1) Cacti with spikes were more likely to survive. 2) Cacti with spikes reproduced more successfully. 3) Cacti with spikes over time became more common.
fill in gaps that exist in the fossil record, helping us acquire a greater understanding of how modern species have changed over time from ancestral species
Transitional fossil:
a group of interbreeding individuals of the same spp
Population:
any change in allele frequencies in a pop. over time
Microevolution:
results from a small number of individuals colonizing a new area
Founder Effect:
no interbreeding b/w populations (geographic, behavioral, temporal)
Reproductive Isolation:
rapid diversification of species into newly available habitats & ecological opportunities (niches)
Adaptive Radiation: