variation/adaptation
What is genetic variation
Differences in DNA and traits among individuals in a population
Does evolution happen to individuals or populations?
Populations
What is an allele frequency?
The percentage of a specific allele in a population.
What is a selective pressure?
An environmental factor that affects survival and reproduction.
What is a mutation?
A change in the DNA sequence.
What are 2 main ways variation is created in a population
2. Sexual reproduction
What is natural selection?
The process where organisms with helpful traits survive and reproduce more successfully.
If a population has 20 total alleles and 5 are recessive, what is the recessive allele frequency?
25% or 0.25.
Give one example of a selective pressure.
Predators, disease, climate, or food availability.
How does crossing over during meiosis increase variation?
It exchanges DNA between homologous chromosomes, creating new allele combinations.
What is an adaptation?
A trait that helps an organism survive and reproduce in its environment
Why do helpful adaptations become more common over time?
Organisms with those traits survive longer and produce more offspring that inherit the trait.
If the dominant allele frequency is 0.7 (70%), what is the recessive allele frequency?
0.3 (30%)
How can predators act as a selective pressure?
Organisms with traits that help them avoid predators survive and reproduce more often.
Why is genetic variation important in a population?
It increases the chance that some individuals can survive environmental changes.
What is evolutionary fitness
A trait that helps an organism survive and reproduce in its environment.
Can a trait that was once an adaptation stop being helpful? Explain.
Yes. If the environment changes, a previously helpful trait may no longer improve survival or reproduction.
Why do scientists study allele frequencies when studying evolution? (how does it connect?)
Because changes in allele frequencies over time show that evolution is occurring in a population.
A cold environment favors animals with thick fur. What will likely happen to the population over many generations?
More individuals with thick fur will survive and reproduce, making thick fur more common.
Why can’t an individual organism evolve during its lifetime?
An individual’s genes do not change in a way that affects allele frequencies; evolution happens through changes across generations in populations.
A population of insects is mostly green, but some are brown. After a drought, the environment becomes mostly brown dirt and rocks. Explain how natural selection could change the population over time.
Brown insects would be better camouflaged, making them more likely to survive and reproduce. Over time, the brown trait would become more common in the population.
Explain the four main steps of natural selection. (basically how does natural selection occur overtime?
A population has 40 total alleles for a gene. 30 are dominant (A) and 10 are recessive (a). Calculate the frequency of each allele.
A disease kills most plants without a certain resistance mutation. Explain how this affects allele frequencies in the population over time.
Plants with the resistance mutation survive and reproduce more, increasing the frequency of the resistance allele in future generations.
Explain how mutations, sexual reproduction, and natural selection work together to drive evolution.
Mutations create new alleles, sexual reproduction mixes alleles into new combinations, and natural selection increases the frequency of helpful traits over time, causing populations to evolve.