Intro to Biodiversity and Ecosystem Services

Learning Objective ERT-2.A: Explain levels of biodiversity and their importance to ecosystems.
- Essential Knowledge ERT-2.A.1: Biodiversity in an ecosystem includes genetic, species, and habitat diversity.
- Essential Knowledge ERT-2.A.2: A more genetically diverse population can better respond to environmental stressors. A population bottleneck can lead to a loss of genetic diversity.
- Essential Knowledge ERT-2.A.3: Ecosystems with a larger number of species are more likely to recover from disruptions.
- Essential Knowledge ERT-2.A.4: Loss of habitat leads to a loss of specialist species, followed by generalist species. It also reduces the numbers of species with large territorial requirements.
- Essential Knowledge ERT-2.A.5: Species richness is the number of different species in an ecosystem.

Definition: Biodiversity refers to the diversity of life forms present in an ecosystem.
Measurement: Biodiversity is measured on 3 different levels:
- Genetic Diversity: This measures how different the genes are among individuals within a population (a group of the same species).
- Species Diversity: This measures the number of different species in an ecosystem, as well as the balance or evenness of the population sizes of all species within that ecosystem.
- Ecosystem Diversity: This refers to the number of different habitats available in a given area.
General Principle: Higher biodiversity is directly correlated with higher ecosystem and population health. A healthier ecosystem or population is more robust and resilient.

Species Richness (r): This is simply the total number of different species found in a particular ecosystem.
- A high species richness is generally considered a good indicator of ecosystem health, suggesting the presence of more quality resources such as H_2O and soil.
Species Evenness: This is a measure of how balanced the individual organisms in an ecosystem are across the different species.
- Evenness helps to indicate if one or two species dominate the ecosystem or if the population sizes of all species are relatively well-balanced.

Definition: Genetic diversity measures how different the genomes (the complete set of genes) are among individuals within a population of a given species.
Origin of Genetic Diversity: Genetic diversity exists in all populations due to two primary mechanisms:
- Random Mutations: Errors in the copying of DNA can lead to new gene combinations and traits.
- Recombination of Chromosomes: During the formation of sex cells in parents, chromosomes can recombine, leading to new genetic combinations and traits in offspring.
Importance: The more genetic diversity a population possesses, the better equipped it is to respond to environmental stressors such as drought, disease, or famine.
- Higher genetic diversity increases the probability that some individuals within the population will have traits that enable them to survive a particular environmental stressor.

Definition: A bottleneck event is an environmental disturbance, such as a natural disaster or human habitat destruction, that drastically reduces a population's size and indiscriminately kills organisms regardless of their genetic makeup.
Consequences: These events severely reduce genetic diversity within the surviving population.
- The surviving population is smaller and, because individuals died randomly, it often does not represent the full genetic diversity of the original population.
- A smaller, less genetically diverse population becomes even more vulnerable to future environmental disturbances.