Habitat destruction is the leading cause for declining populations of species on our planet. due to human development, industry, and forestry, humans are destroying the habitat of many species at an alarming rate. consider the bald eagle. the bald eagle population was threatened in the late 60s and early 70s. to an aggressive bald eagle protection program, bald eagle numbers in the wild have soared as seen in the population graph above. the bald eagle's population very nearly reached extinction. why did the bald eagle's declining population make it more vulnerable to extinction? a) as populations decline, reproduction stops b) as populations decline, less resources are available c) as populations decline, there is less genetic diversity d) as populations decline, birds migrate farther away from other populations

The answer is C) As populations decline, there is less genetic diversity. This is called the 'founder effect'. With limited numbers of individuals in a population, it is more likely that highly-related individuals will mate. This will result in recessive and deleterious genes being manifested in the phenotype. Consider that higher organisms are diploid: they contain two complete sets of chromosomes, one from each parent. Within each chromosome, some alleles will be dominant while others will be recessive, i.e., for the recessive alleles to be manifested in the phenotype, both have to be recessive, whereas for the dominant allele, only one of the alleles has to be dominant for the allele to manifest in the phenotype. With lower genetic diversity, a higher proportion of individuals will have chromosomes containing both recessive alleles, which may manifest as lowered fitness and genetic disorders.