Biodiversity and Ecosystems Review

Diversity of life forms in an ecosystem: This is measured on three different levels:
- Genetic diversity: Refers to the variation in genes among individuals within a population (a group of the same species).
- Species diversity: Encompasses both the total number of different species in an ecosystem (richness) and the relative abundance or evenness of the population sizes of all species within that ecosystem.
- Ecosystem diversity: Represents the number of different habitats available within a given geographical area.
Significance: Higher biodiversity generally leads to higher ecosystem and population resilience when faced with disturbances.

Richness (S): Simply the total count of different species found in a particular ecosystem.
- High richness is usually an indicator of good ecosystem health, suggesting an abundance of quality resources such as water and soil.
Evenness: A metric that assesses how balanced the population sizes are among the different species in an ecosystem.
- It indicates whether there are one or two dominant species or if population sizes are well-distributed across all species.

Definition: Genetic diversity is a measure of how different the genomes (the complete set of genes) are among individuals within a population of a specific species.
Origin: Genetic diversity naturally exists in all populations due to two main processes:
- Random mutations: Errors during DNA replication introduce new genetic variations.
- Recombination of chromosomes: During the formation of sex cells (meiosis) in parents, chromosomes exchange genetic material, leading to new gene combinations and novel traits in offspring.
Benefits:
- A population with greater genetic diversity is better equipped to respond to environmental stressors like drought, disease, or famine.
- Higher genetic diversity increases the probability that some individuals within the population will possess traits that allow them to survive and reproduce despite the environmental stressor.

Definition: An environmental disturbance (e.g., natural disaster, human habitat destruction) that drastically reduces a population's size, indiscriminately killing organisms regardless of their genetic makeup.
Impact on Genetic Diversity: Bottleneck events significantly reduce genetic diversity.
- The surviving population is smaller and, because individuals died randomly, it may not accurately represent the genetic diversity of the original larger population.
Increased Vulnerability: A smaller, less genetically diverse population becomes even more susceptible to future environmental disturbances.