Biodiversity, Conservation, and Evolution

Module 4 (9/22–9/28) · Biodiversity, Ecosystem Services and Conservation; Adaptations, Natural Selection, Evolution · Blueprint Pillar 3 · PGCC Outcome 2 · Download .docx

Objectives

Define the three levels of biodiversity.
Explain natural selection and the conditions required for it.
Distinguish background extinction from mass extinction.
Describe keystone species and trophic cascades.

Key terms

Genetic diversity: Variation in DNA sequences among individuals within a species.
Species diversity: The variety and relative abundance of species in a given area.
Ecosystem diversity: The range of different habitat types, communities, and ecological processes on Earth.
Ecosystem services: Benefits that functioning ecosystems provide to humans: provisioning, regulating, cultural, supporting.
Natural selection: Differential survival and reproduction of individuals due to heritable trait differences.
Adaptation: A heritable trait that increases an organism's fitness in a particular environment.
Speciation: The evolution of new species when populations become reproductively isolated.
Background extinction: The low, ongoing rate of species loss that occurs between mass extinction events.
Mass extinction: A rapid, global event in which more than 75% of species go extinct.
IUCN Red List: International Union for Conservation of Nature's global database of species extinction risk.
Keystone species: Species with a disproportionately large impact on ecosystem structure relative to its biomass.
Trophic cascade: Chain reaction through a food web triggered by adding or removing a predator.

The concept

Biodiversity has three levels: genetic diversity (variation within a species), species diversity (variety of species in an area), and ecosystem diversity (variety of habitat types). High biodiversity increases ecosystem resilience and the range of services ecosystems can provide.

Natural selection requires three conditions: heritable variation among individuals, differential reproduction (some traits improve survival and reproduction), and a selective environment. Adaptations are heritable traits that increase fitness in a specific environment — they evolve over generations; no individual evolves. Speciation occurs when populations become reproductively isolated and diverge genetically.

Background extinction is the low, ongoing rate of species loss throughout life's history. Mass extinctions are rapid, catastrophic events eliminating more than 75% of species. Keystone species have a disproportionately large effect on ecosystem structure relative to their abundance — removing them triggers trophic cascades. The IUCN Red List classifies species by extinction risk from Least Concern to Extinct.

Self-check

Try each one before you look. A miss here costs nothing and tells you exactly what to reread.

1. The three levels of biodiversity are:

2. Which of the following is a required condition for natural selection to occur?

3. A keystone species is defined by:

4. What distinguishes a mass extinction from background extinction?

5. A trophic cascade is triggered when:

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