Glossary
Adaptations
Heritable traits that increase an organism's fitness, allowing it to survive and reproduce more successfully in its specific environment.
Example:
The thick blubber of a polar bear is an adaptation that helps it survive in extremely cold Arctic temperatures.
Allele Frequencies
The proportion of a specific allele (a variant form of a gene) within a population's gene pool.
Example:
If a population of rabbits has a gene for fur color with two alleles, brown and white, and the brown allele becomes more common over time, its allele frequency has increased.
Artificial Selection
A process where humans intentionally breed organisms with desirable traits to manipulate the phenotypic frequencies of a population or species.
Example:
A dog breeder chooses to mate two golden retrievers with the calmest temperaments, hoping to produce a litter of equally calm puppies, demonstrating artificial selection for a specific behavioral trait.
Convergent Evolution
The independent evolution of similar traits in unrelated organisms due to similar environmental pressures or ecological niches.
Example:
Dolphins (mammals) and sharks (fish) both evolved streamlined bodies and dorsal fins for efficient movement through water, despite their distant evolutionary relationship, showcasing convergent evolution.
Differential Reproductive Success
The concept that individuals with certain traits are more likely to survive and produce more offspring than others in a given environment.
Example:
A fish with a unique camouflage pattern avoids predators more effectively, allowing it to live longer and lay more eggs than its less camouflaged peers, illustrating differential reproductive success.
Environmental Pressures
Factors in an organism's surroundings that influence its survival and reproduction, driving natural selection.
Example:
A sudden drought in a grassland ecosystem acts as an environmental pressure, favoring plants that can store water more efficiently.
Natural Selection
A process where environmental pressures favor certain heritable phenotypic variations, leading to differential reproductive success among individuals in a population.
Example:
In a forest, green beetles are better camouflaged on leaves than brown beetles, so they are less likely to be eaten by birds and more likely to reproduce, increasing the frequency of the green beetle trait over generations.
Phenotypic Variations
Observable differences in the characteristics or traits among individuals within a population, which are often heritable.
Example:
In a population of sunflowers, some plants grow tall while others remain short, and some have large flower heads while others have small ones; these are all examples of phenotypic variations.
Selective Breeding
The process of choosing specific organisms with desired traits to reproduce, aiming to enhance or perpetuate those traits in future generations.
Example:
Farmers engaging in selective breeding might only allow their highest-yielding corn plants to pollinate, ensuring that the next generation of corn is more productive.
Survival of the Fittest
A phrase summarizing natural selection, meaning that individuals best adapted to their environment are more likely to survive and pass on their genes.
Example:
In a harsh desert environment, cacti with thicker waxy coatings lose less water and are more likely to survive and reproduce, embodying the principle of survival of the fittest.