Describe natural selection with reference to: (a) genetic variation within populations (b) production of many offspring (c) struggle for survival, including competition for resources (d) a greater chance of reproduction by individuals that are better adapted to the environment than others (e) these individuals pass on their alleles to the next generation
Describe natural selection with reference to: (a) genetic variation within populations (b) production of many offspring (c) struggle for survival, including competition for resources (d) a greater chance of reproduction by individuals that are better adapted to the environment than others (e) these individuals pass on their alleles to the next generation
Answer
Natural selection is a fundamental mechanism of evolution that explains how populations change over time. It operates through several interconnected processes that influence the survival and reproduction of individuals within a population. Here’s a detailed description of natural selection with reference to key concepts:
(a) Genetic Variation Within Populations
Genetic variation refers to the differences in DNA sequences among individuals within a population. This variation is crucial for natural selection because it provides the raw material upon which selection can act. Variations can arise from mutations, gene flow, and sexual reproduction, leading to different traits (phenotypes) among individuals. For example, in a population of beetles, some may be green while others are brown due to genetic differences.
(b) Production of Many Offspring
Most species produce more offspring than can survive to adulthood. This overproduction creates a situation where not all individuals will survive due to limited resources, predation, disease, and other environmental pressures. For instance, a single fish may lay thousands of eggs, but only a small fraction will reach maturity. This high reproductive rate increases the likelihood that some offspring will possess advantageous traits.
(c) Struggle for Survival, Including Competition for Resources
Within populations, individuals must compete for limited resources such as food, water, shelter, and mates. This competition leads to a “struggle for survival,” where only those individuals best suited to their environment are likely to survive and reproduce. For example, in an environment with limited food sources, stronger or faster animals may outcompete their peers for food, while weaker individuals may not survive long enough to reproduce.
(d) Greater Chance of Reproduction by Individuals Better Adapted to the Environment
Natural selection favors individuals with traits that provide advantages in their specific environments—these traits are referred to as adaptations. Individuals that are better adapted have a higher chance of surviving and reproducing compared to those with less advantageous traits. For example, in a population of rabbits living in snowy regions, those with white fur may be less visible to predators than those with brown fur, giving them a better chance of survival and reproduction.
(e) Passing on Alleles to the Next Generation
Individuals that successfully survive and reproduce pass on their alleles (gene variants) to the next generation. Over time, this leads to an increase in the frequency of beneficial alleles within the population. As advantageous traits become more common through successive generations, the overall genetic makeup of the population shifts. For instance, if white-furred rabbits have higher reproductive success, the allele for white fur will increase in frequency in future generations.
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