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Question 1
What are the four conditions required for natural selection to occur?
Answer: There must be variation in a trait, that variation must be heritable, individuals must struggle for existence (limited resources), and individuals with favorable traits must have greater reproductive success (differential survival/reproduction).
Question 2
What is the definition of fitness in the context of natural selection?
Answer: Fitness is the relative ability of an organism to survive and reproduce in its environment, contributing offspring to the next generation. It is always measured relative to other individuals in the population.
Question 3
Why must heritable variation exist for natural selection to produce evolutionary change?
Answer: If variation is not heritable, advantageous traits cannot be passed to offspring, so differential survival has no lasting effect on the population's gene pool across generations.
Question 4
What is the difference between natural selection and evolution?
Answer: Natural selection is a mechanism (a process) that acts on individuals, while evolution is the result — a change in allele frequencies in a population over generations. Natural selection is one of several mechanisms that can drive evolution.
Question 5
Why does natural selection act on phenotype rather than directly on genotype?
Answer: The environment interacts with an organism's physical and functional traits (phenotype), which determines survival and reproduction. Genotypes are selected indirectly because the phenotype is the expressed product of the genotype.