Biodiversity and Evolution Notes

Biodiversity and Evolution

3.1 Biodiversity and Evolution

Biodiversity

  • Total diversity of living systems.

  • Made up of habitat diversity, species diversity, and genetic diversity.

Components of Biodiversity

  • Habitat Diversity: The range of different habitats in an ecosystem or biome; associated with the variety of ecological niches.

    • Example: Woodland with soil, rivers, trees, shrubs, ground vegetation, leaf litter, and fallen dead trees.

    • Habitat refers to the environment in which a species normally lives.

  • Species Diversity: The variety of species per unit area; includes the number of species and their relative abundance.

    • Higher species diversity indicates greater complexity.

    • Species are groups of organisms sharing common characteristics that interbreed and produce fertile offspring.

  • Genetic Diversity: The range of genetic material present in a population of a species.

    • Large gene pool indicates high genetic diversity.

    • Genes are sections of DNA in the nucleus of all cells.

    • The gene pool is all different types of genes within every individual of a species.

    • Example: Cheetahs have low genetic diversity, making them more prone to extinction.

Measuring Species Diversity

  • Richness: The number of species per sample.

    • Does not account for the number of individuals of each species.

    • Gives equal weight to species regardless of their population size.

  • Evenness: A measure of the relative abundance of different species in an area.

    • A sample where the total number of individuals is evenly distributed between species has high evenness and is considered more diverse.

Biodiversity and Resilience

  • Components of diversity contribute to the resilience of ecological systems.

  • Resilience is the ability of a system to maintain equilibrium and avoid tipping points.

  • Communities with high species diversity have complex food webs, so the loss of one species does not severely affect the community.

  • Ecosystems with many different habitats enable many niches to coexist, which enhances species diversity.

  • Genetically diverse species are more likely to survive than populations with low genetic diversity.

Biodiversity and Climate Change

  • Climate change impacts biodiversity.

  • Biodiversity can limit climate change.

  • The resilience provided by biodiversity guards against the effects of global warming.

Evolution

Evolution and Natural Selection

  • Evolution results from cumulative changes in the heritable characteristics of a population or species over many successive generations.

  • Charles Darwin's 'On the Origin of Species' describes evolution.

  • Natural selection is a key mechanism of evolution.

Evidences of Evolution

  • Older rocks contain fossils of simpler life forms, while recent rocks contain fossils of more complex forms.

Darwin's Theory

  • Darwin's observations during his HMS Beagle expedition (1831-1836) led to his theory of evolution by natural selection.

Key Observations by Darwin

  • Species tend to over-produce, leading to competition for limited resources.

  • Individuals of the same species show variation.

  • Genetic diversity gives rise to variation, with genetic mutations being beneficial, damaging, or neutral.

Natural vs. Artificial Selection

  • Natural Selection: Nature does the choosing.

  • Artificial/Selective Breeding: Humans choose animals or plants to breed based on desired characteristics.

Adaptations

  • Different species of giant tortoise on different Galapagos Islands have adaptations to local conditions, such as shell shape adapted to vegetation height.

Mechanisms of Natural Selection

  • Genetic diversity exists within a population.

  • Individuals better suited to their environment reproduce more successfully.

  • Offspring inherit advantageous genes, leading to subsequent generations also having these genes.

Speciation

  • Natural selection alone is insufficient for speciation; reproductive isolation is required.

  • If isolated populations are in different environments, natural selection will lead to speciation.

  • Example: Spotted owls in Northern America have become geographically separated, forming subspecies adapted to different climates and ecosystems.

Measuring Biodiversity

Simpson’s Reciprocal Index of Diversity

  • Species diversity is a function of both the number of different species and the relative number of individuals of each species.

  • D = \frac{N(N-1)}{\sum n(n-1)}

  • Where:

    • D = Simpson’s reciprocal index

    • N = total number of organisms of all species found

    • n = number of individuals of a particular species

  • A high D value suggests a stable and mature site; a low value suggests pollution, recent colonization, or agricultural management.

Calculating Simpson's Index (Example)

  • Ecosystem 1: N = 70, D = 3.07

Sampling Methods

  • Samples must be comprehensive to ensure all species are sampled, but certain habitats may be missed.

  • Perform a cumulative species count and note any additional species are added to species richness. Graph levels off and gives you the best estimate of the number of species in your ecosystem.

Human Impact and Conservation

Human Impacts on Biodiversity

  • Human activities significantly impact biodiversity.

Hotspots

  • Areas with high biodiversity under threat from humans.

  • Endemic species are species not found anywhere else.

Conservation Strategies

  • Protected Areas

  • Habitat Restoration

  • Sustainable Use of Natural Resources

  • Captive Breeding and Reintroduction

  • Education and Awareness

Kinabalu Birdwing Butterfly

  • Mount Kinabalu in SE Asia shows altitudinal zonation and has many endemic species.

  • The birdwing butterfly's native habitat is undisturbed cloud forest, with larvae feeding on Aristolochia foveolata.

Conservation Efforts

  • Tourism and ecotourism can help sustain ecosystems.

  • Training homestay owners to breed birdwings.

  • Public awareness campaigns.

  • Borneo Birdwing Project: Swallowtail and Birdwing Butterfly Trust.

Biodiversity Crisis

  • 150,300 species on the IUCN Red List.

  • High percentages of amphibians, sharks and rays, corals, conifers, mammals, and birds are endangered.

  • Organizations like Enel Green Power are involved in biodiversity protection projects.

Nature Positive by 2030

  • Goals include protecting and restoring natural habitats, safeguarding diversity of life, and halving the footprint of production and consumption.

Solutions

  • Protecting at least 30% of natural habitats, halting human-induced extinctions, and transitioning to sustainable practices.

Review Questions

  1. Define habitat diversity, species diversity, and genetic diversity.

  2. Distinguish between species diversity and species richness.

  3. Outline what high and low values of the Simpson reciprocal index indicate about an ecosystem.

    • Explain how diversity indices can be used to measure the impact of human activities.

    • Discuss the usefulness of providing numerical values of species diversity to understanding the nature of biological communities and the conservation of biodiversity.

  4. Describe the process of natural selection and how it leads to the generation of new species.

  5. Explain how the isolation of populations leads to speciation.