Definition
Biodiversity
Biodiversity refers to the variety of life in an ecosystem, encompassing different levels of biological organization.
- It plays a crucial role in maintaining ecosystem stability, resilience, and productivity.
- Biodiversity is generally categorized into three levels: habitat, species and genetic diversity.
Levels of Biodiversity
- Biodiversity is studied at three interconnected levels:
- Habitat diversity: the variety of different habitats or ecosystems in a given area.
- Species diversity: the number and relative abundance of species in a particular region.
- Genetic diversity: the range of genetic material within a species.
- Each level interacts with and supports the others, forming the foundation for ecological resilience.
Note
- Biodiversity is not only about the number of species but also their ecological roles, interactions, and functional diversity.
- Together, these levels determine the resilience of ecosystems and their ability to adapt to change.
Habitat Diversity
Definition
Habitat diversity
Habitat diversity is the range of different habitats present in an ecosystem or within a geographical area.
- Habitat diversity refers to the range of different habitats or ecological niches present in an ecosystem or biome.
- Each habitat supports distinct communities of organisms adapted to its specific conditions.
- High habitat diversity usually corresponds to high biodiversity overall, as different habitats host varied species.
Tip
- Ecosystems such as coral reefs and tropical rainforests have exceptionally high habitat diversity, supporting countless microhabitats and species interactions.
- In contrast, deserts or polar regions have relatively uniform conditions, resulting in lower habitat diversity.
Example
- The Amazon Rainforest has high habitat diversity, with tropical forests, rivers, wetlands, and grasslands supporting a vast range of organisms.
- Coral reefs offer diverse microhabitats such as reef crests, lagoons, and deep-sea areas, allowing for a rich variety of species.
- In urban areas, habitat diversity is lower due to human land use reducing natural environments.
Analogy
- Think of habitat diversity as the “architecture” of biodiversity.
- The more rooms (habitats) a building has, the more types of occupants (species) it can support.
Species Diversity
Definition
Species diversity
Species diversity is the variety of species in an ecosystem, including both species richness (the number of species) and species evenness (the relative abundance of each species).
- Species diversity represents the variety of different species within an ecosystem and their relative abundance.
- It includes both species richness (number of species) and species evenness (how evenly individuals are distributed among species).
Tip
- Species-rich ecosystems such as rainforests or coral reefs are highly stable and resilient because their complex food webs can withstand disturbances.
- Ecosystems with low species diversity, like monoculture pine forests, are vulnerable to collapse when faced with diseases or pests.
Example
- The Great Barrier Reef has high species diversity, with over 1,500 fish species and 600 coral species.
- Tropical rainforests have more species than temperate forests, as the stable climate supports year-round biodiversity.
- Monoculture farms (e.g., large wheat fields) have low species diversity, making them more vulnerable to pests and diseases.
Genetic Diversity
Definition
Genetic diversity
Genetic diversity is the variety of genes within a species, allowing for adaptation to environmental changes.
- Species-rich ecosystems such as rainforests or coral reefs are highly stable and resilient because their complex food webs can withstand disturbances.
- Ecosystems with low species diversity, like monoculture pine forests, are vulnerable to collapse when faced with diseases or pests.
Tip
- Populations with high genetic diversity are more adaptable to environmental changes, disease, and climate variation.
- Low genetic diversity increases the risk of extinction due to limited ability to evolve or respond to stressors.
Example
- Cheetahs have low genetic diversity, making them more susceptible to diseases and environmental changes.
- Wild plant populations have higher genetic diversity than cultivated crops, making them more resistant to pests and drought.
- Domesticated dog breeds show high genetic diversity due to selective breeding for various traits.
Interconnection Between Levels of Diversity
- High habitat diversity → supports more niches → increases species diversity.
- High species diversity → broadens the gene pool → enhances genetic diversity.
- High genetic diversity → allows populations to adapt and persist → maintains ecosystem stability.
Example
Protecting coral reefs (habitat diversity) helps preserve thousands of fish and coral species (species diversity) and maintains genetic variation within these populations (genetic diversity).
The Role of Biodiversity in Ecosystem Resilience
- Ecosystem resilience is the capacity of a system to withstand disturbance and recover from stress while maintaining essential functions.
- Each level of biodiversity strengthens resilience in a distinct way:
- Habitat diversity ensures that if one habitat type is degraded, others can still provide refuge or resources.
- Species diversity adds redundancy, so if one species is lost, others can fill its role (unless it’s a keystone species).
- Genetic diversity allows populations to adapt to gradual or sudden environmental changes, enhancing survival prospects.
Example
After a forest fire, genetically diverse plant populations have a higher chance of producing individuals tolerant to new soil or moisture conditions, allowing regrowth and stabilization.
Evolution as a Driver of Biodiversity
Definition
Evolution
Evolution is the cumulative change in the heritable characteristics of a population over generations.
- Biodiversity is the product of millions of years of evolution, the gradual accumulation of genetic changes within populations over time.
- Evolution explains the origin of new species and the diversity of life forms on Earth.
Key Mechanisms of Evolution
- Mutation: Random changes in DNA that introduce new alleles into the gene pool.
- Natural Selection: Individuals with advantageous traits survive and reproduce more successfully.
- Genetic Drift: Random changes in allele frequencies, especially in small populations.
- Gene Flow: Movement of genes between populations through migration or interbreeding.
Examples of Evolutionary Change
- Darwin’s Finches (Galápagos Islands): Beak shapes evolved based on food sources, showing adaptive radiation.
- Peppered Moth (Industrial Revolution): Change in coloration due to environmental selection pressures.
- Human Evolution: Shared ancestry with chimpanzees highlights cumulative genetic changes over millions of years.
Self review
- Define biodiversity and describe its three levels with examples.
- Explain how habitat diversity can lead to increased species and genetic diversity.
- Discuss why ecosystems with high species diversity tend to be more resilient.
- How does genetic diversity help species survive environmental changes?
- Explain why low genetic diversity can make species more prone to extinction.
