AP Bio 8.7 Disruptions to Ecosystems

species are well-adapted to their environments

• the source of most genetic variation is mutations which are random, but selection is not

  • mutations that produce variation that provide an advantage become more frequent

  • adaptations: variations that are selected for and provide an advantage in a particular environment

• heterozygote advantage: heterozygous genotype has a higher fitness than homozygous dominant or recessive genotypes

• species are specially adapted to their environments and to the other populations in their communities

ecosystem can get disrupted too rapidly for them to adapt through natural selection

• habitat loss, especially through logging and urbanization

  • drives species extinction by drastically altering habitats

• habitat fragmentation limits exchange of genes in populations

  • decreases diversity

• invasive species exploit a new niche free of predators and competition to outcompete native species

  • intentionally or unintentionally introduced by humans to a new ecosystem

• pollution can cause biomagnification and eutrophication

  • biomagnification: accumulation of toxins in animals at high tropic levels in ecosystems

  • eutrophication: nutrients from fertilizers or sewage lead to excessive algae growth that depletes oxygen from aquatic ecosystems

    • prevent penetration of sunlight in a body of water

• climate change alters ecosystems at a high rate, especially near the poles

• natural geological and meteorological events can also impact habitat change and ecosystem distributions, leading to diversity loss

  • break up of Pangaea (continental drift), volcanic activity, and meteor strikes have all caused mass extinctions

the extinction vortex

• reduction in size of a population results in less genetic diversity, which puts a species at risk even more