Glossary
Adaptation
A heritable trait that increases an organism's fitness in its specific environment, resulting from natural selection over generations.
Example:
The thick fur of a polar bear is an adaptation that helps it survive and thrive in cold Arctic environments.
Differential reproductive success
The phenomenon where individuals with certain advantageous traits produce more viable offspring than others in a given environment, leading to an increase in the frequency of those traits.
Example:
If a bird with a longer beak can access more food and thus lay more eggs than a short-beaked bird, it demonstrates differential reproductive success.
Evolution
The change in the heritable characteristics of biological populations over successive generations, driven by mechanisms like natural selection.
Example:
The evolution of antibiotic resistance in bacteria demonstrates how populations can change rapidly in response to selective pressures from medications.
Fitness
A measure of an organism's ability to survive and reproduce in its environment, contributing its genes to the next generation.
Example:
A cheetah that is faster and catches more prey, thus producing more surviving cubs, has higher fitness than a slower cheetah.
Heritable variations
Differences in traits among individuals within a population that can be passed down from parents to offspring, serving as the raw material for natural selection.
Example:
A litter of puppies having different fur colors, some brown and some black, represents heritable variations that could be favored or disfavored by their environment.
Mutation
A random change in the DNA sequence of an organism, which can introduce new traits or variations into a population.
Example:
A sudden change in a bacterial gene that makes it resistant to an antibiotic is a mutation, providing a new trait that can be selected for.
Natural Selection
The process by which environmental factors favor certain heritable traits, leading to increased survival and reproduction of individuals with those traits, and thus changes in populations over time.
Example:
In a forest with dark tree trunks, natural selection would favor dark-colored moths, making them more likely to survive and reproduce than light-colored moths.
Phenotype
Any observable trait or characteristic of an organism, resulting from the interaction of its genotype with the environment.
Example:
The blue color of a butterfly's wings is its phenotype, which might help it attract mates or deter predators.
Phenotypic variation
The range of observable traits within a population, which is essential for natural selection to occur as it provides the raw material for selection.
Example:
The different heights observed among students in a classroom represent phenotypic variation in human height.
Selective Pressure
Environmental factors that favor the survival and reproduction of individuals with certain traits over others, driving natural selection.
Example:
A severe drought creating scarce water resources acts as a selective pressure, favoring plants with deeper root systems that can access water.