LEVELS OF BIODIVERSITY

 LEVELS OF BIODIVERSITY

B.Sc. Zoology, zoologys.co.in 

Prepared by Dr Bhabesh Nath, Assistant Professor, Department of Zoology, B N College (A)Dhubri   

 

Introduction

Biodiversity, or biological diversity, refers to the variety and variability of living organisms and the ecological complexes in which they occur. It includes differences within species, between species, and among ecosystems. Biodiversity is therefore not restricted to the number of species present in an area; it also includes genetic variation and the diversity of communities and ecosystems.

Major Levels of Biodiversity

Biodiversity is commonly studied at three major levels:

· Genetic diversity: variation in genes and alleles among individuals and populations of the same species.

· Species diversity: variety of species and their relative abundance in a particular habitat or region.

· Ecosystem diversity: variety of ecosystems, habitats, biological communities, and ecological processes in a geographical area.

Genetic Diversity

Genetic diversity is the variation in genetic composition among individuals, populations, or geographical races of a species. It arises through mutation, recombination, gene flow, and other evolutionary processes.

Importance of Genetic Diversity

· Provides the raw material for adaptation and evolution.

· Increases the ability of populations to withstand environmental changes, diseases, and parasites.

· Helps maintain reproductive and ecological fitness of populations.

· Supports selective breeding and improvement of domesticated animals and crops.

· Reduces the risk of population decline caused by inbreeding and loss of genetic variation.

Examples

· Different breeds of domestic cattle, dogs, and poultry show genetic variation within species.

· Different populations of a species may possess adaptations to temperature, salinity, altitude, food availability, or disease.

· Wild populations of the same species can contain locally adapted genetic variants.

Species Diversity

Species diversity refers to the variety of species occurring in a community, ecosystem, or geographical region. It has two important components: species richness and species evenness.

Species Richness

Species richness is the number of different species present in a defined area. For example, a forest containing 100 species has greater species richness than a forest containing 40 species, if the areas being compared are equivalent.

Species Evenness

Species evenness describes how equally individuals are distributed among the species in a community. Two communities may contain the same number of species but differ greatly in evenness.

Types of Species Diversity

· Alpha diversity: diversity within a particular habitat or local community.

· Beta diversity: change in species composition between habitats or communities.

· Gamma diversity: overall diversity across a larger geographical region or landscape.

Examples

· A tropical rainforest generally contains many more species than a highly disturbed urban habitat.

· A coral reef supports a large variety of fishes, cnidarians, molluscs, crustaceans, echinoderms, and microorganisms.

· A pond community contains interacting species of fish, insects, molluscs, amphibians, algae, aquatic plants, and microorganisms.

Ecosystem Diversity

Ecosystem diversity is the variety of ecosystems and ecological communities found in a region. It includes differences in physical conditions, organisms, habitats, food webs, nutrient cycles, and ecological processes.

Examples of Ecosystem Diversity

· Terrestrial ecosystems: forests, grasslands, deserts, and mountain ecosystems.

· Freshwater ecosystems: ponds, lakes, rivers, streams, and wetlands.

· Marine ecosystems: coral reefs, estuaries, mangroves, seagrass beds, and open-ocean systems.

· Human-influenced ecosystems: agroecosystems, urban ecosystems, and managed landscapes.

Importance

· Provides habitats and ecological niches for diverse organisms.

· Supports nutrient cycling, decomposition, pollination, soil formation, and primary production.

· Maintains ecological stability and resilience.

· Provides ecosystem services such as food, freshwater, climate regulation, coastal protection, and recreation.

· Creates opportunities for scientific study, education, and conservation.

Relationship Among the Three Levels

The three levels are interconnected. Genetic diversity contributes to the long-term survival and adaptability of species. Species diversity contributes to the structure and functioning of communities. Different communities, together with their physical environments and ecological processes, form diverse ecosystems. Loss at one level can influence the other levels.

Level	Unit of variation	Main components	Example
Genetic diversity	Genes within a species	Alleles, genotypes, populations	Breeds and locally adapted populations
Species diversity	Species in a community or region	Richness and evenness	Species-rich rainforest
Ecosystem diversity	Ecosystems and habitats	Communities, habitats, ecological processes	Forest, wetland, coral reef

Factors Affecting Biodiversity

· Habitat loss and fragmentation.

· Overexploitation of biological resources.

· Pollution of air, water, and soil.

· Invasive alien species.

· Climate change and associated changes in temperature and precipitation.

· Natural disasters and other disturbances.

· Small population size, inbreeding, and loss of genetic variation.

Conservation of Biodiversity

Conservation aims to maintain biodiversity at genetic, species, and ecosystem levels. Effective conservation generally combines protection of habitats with sustainable management of biological resources.

· In-situ conservation: protection of organisms in their natural habitats, such as national parks, wildlife sanctuaries, biosphere reserves, and protected wetlands.

· Ex-situ conservation: conservation outside natural habitats through zoos, aquaria, botanical gardens, seed banks, gene banks, and captive-breeding programmes.

· Sustainable use of biological resources.

· Habitat restoration and ecological management.

· Control of invasive species and illegal wildlife trade.

· Public awareness, environmental education, and community participation.

Key Points for Examination

1. Biodiversity has three principal levels: genetic diversity, species diversity, and ecosystem diversity.

2. Genetic diversity is variation within and among populations of the same species.

3. Species diversity includes species richness and species evenness.

4. Ecosystem diversity represents the variety of ecosystems and ecological communities in a region.

5. Alpha, beta, and gamma diversity describe species diversity at local, between-community, and regional scales.

6. The three levels of biodiversity are interconnected and should be conserved together.

Conclusion

Understanding biodiversity at genetic, species, and ecosystem levels provides a framework for studying biological variation and its conservation. Genetic diversity enables populations to adapt, species diversity supports complex communities, and ecosystem diversity maintains a wide range of habitats and ecological processes. Conservation strategies are most effective when all three levels are considered together.

Short Answer Questions

· Define biodiversity.

· What is genetic diversity? Give two examples.

· Distinguish between species richness and species evenness.

· What are alpha, beta, and gamma diversity?

· Define ecosystem diversity and give examples.

· Why is genetic diversity important for adaptation?

· Differentiate in-situ and ex-situ conservation.

Multiple Choice Questions

The variation in genes among individuals of the same species is called:

· A. Ecosystem diversity

· B. Genetic diversity

· C. Species richness

· D. Beta diversity

Answer: B

The number of species present in a defined area is known as:

· A. Species richness

· B. Species evenness

· C. Genetic variation

· D. Ecosystem diversity

Answer: A

Species diversity within a local community is commonly termed:

· A. Alpha diversity

· B. Beta diversity

· C. Gamma diversity

· D. Genetic diversity

Answer: A

Variation in species composition between communities is described by:

· A. Alpha diversity

· B. Beta diversity

· C. Genetic diversity

· D. Species richness

Answer: B

The variety of ecosystems in a geographical region is called:

· A. Genetic diversity

· B. Species evenness

· C. Ecosystem diversity

· D. Alpha diversity

Answer: C

References

· Odum, E. P. and Barrett, G. W. Fundamentals of Ecology.

· Primack, R. B. Essentials of Conservation Biology.

· Gaston, K. J. and Spicer, J. I. Biodiversity: An Introduction.

· Raven, P. H. and others. Biology and related biodiversity texts.