biodiversity and evolution

Biodiversity and its levels

Biodiversity is the variety of all living things and their interactions. There are 3 levels of diversity: species diversity, genetic diversity, and ecosystem diversity.

  • Genetic diversity refers to the range of inherited traits within a species; high genetic diversity means many individuals with a wide variety of traits.

  • Species diversity is the number and relative abundance of species in a given area.

  • Ecosystem diversity is the variety of different habitats, communities, and ecological processes.

Evolution and Natural Selection

Evolution is any change in the heritable traits within a population across generations. Natural selection is the process by which species that are best adapted to their environment survive and reproduce, while those that are less well adapted die out. Over generations, organisms become more fit for survival and reproduction in their specific environment.

  • Darwin and Alfred Russel Wallace independently proposed natural selection as a guiding force in evolution. Nature itself acts as the selector, favoring advantageous variations.

  • Natural selection ensures that the fittest survive to pass their genes to the next generation.

Evolution examples (brief concepts)

  • Evolution involves changes in heritable traits, driven by variation and differential survival and reproduction.

  • Mutation introduces genetic variation; in DNA, mutations can lead to new traits.

  • Artificial selection examples include dog domestication: all dogs originally evolved from an ancestral group of grey wolves; selecting and breeding wolves with desirable traits produced modern dogs.

  • Mammals are proposed to have evolved from a shrew-like ancestor, illustrating deep time evolution; the process is guided by natural selection rather than deliberate breeders.

  • The idea that all mammals share a common ancestry highlights broad patterns of evolution across groups.

Humans and biodiversity: impact and threats

Human activities disrupt ecosystems and contribute to biodiversity loss. The main threats are:

  • Habitat destruction, degradation, and fragmentation

  • Exploitation of species

  • Pollution

  • Introduction of alien (invasive) species

  • Climate change

Habitat destruction, degradation, and fragmentation

  • Habitat loss occurs when natural habitats are converted to cropland, urban areas, or infrastructure (roads, dams, powerlines).

  • Habitats are degraded when their condition declines due to pollution, invasive species, and over-utilization of resources.

  • Fragmentation splits large habitat blocks into smaller pieces, often by development such as roads or housing.

Exploitation

  • Exploitation refers to unsustainable use and overharvesting of wild plant and animal species, reducing reproduction and threatening populations.

Pollution

  • Pollution is the introduction of harmful materials into the environment (pollutants), which can be natural or human-made.

  • Pollutants degrade air, water, and land quality and harm wildlife; common sources include vehicle emissions, burning fossil fuels, industrial waste, and pesticides.

Invasive (alien) species

  • Invasive species are introduced to new areas and, once established, can spread rapidly, outcompete native species, and disrupt ecosystems.

Climate change

  • Human activities (burning fossil fuels, deforestation, livestock farming) increase greenhouse gas emissions, boosting the greenhouse effect and global warming, which affects biodiversity and ecosystem function.