Biodiversity and Conservation Class 12 Notes
The presence or occurrence of several ecosystems, bio species, flora and fauna, and various environments in a particular region on the earth is said to be its Biodiversity.
With the increase in human population, Exploitation of these biodiversities began and today it has already gone beyond control. Therefore, it is a must to take precautionary steps to preserve our biodiversity.
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Edward Wilson invented this phrase. From macromolecules to biomes, diversity is abundant. Our Mother Earth can be categorized into three major types of diversities such as genetic, species, and ecological.
These three diversities are discussed in detail below:
Genetic diversity has been defined as the variety and quantity of genetic substances such as genes & chromosomes present in different species and changes that alter the sequences in genes and alleles within the same species. A single species’ genetic diversity may be substantial over its distributional span.
- A bacteriophage can have an average of 100 genes, while a fruit fly, Drosophila melanogaster, has an abundant 13000 genes.
- we Homo sapiens have a pool of 30,000–40,000 genes.
- This huge gap in the number of genes shows the genetic diversity existing simultaneously on the earth.
- Flora also possesses genetic diversity.
- India has over 50,000 genetically different rice varieties and 1000 mango species.
As the geographical and other environmental conditions vary, the difference in the gene pool of species starts becoming obvious. This is so because species need these changes in order to survive.
It is the quantity and diversity of species in an area region diversity and variety. Species richness is defined as the total number of species available per unit of area. The number of individuals of different species in a particular region represents the species’ evenness or equitability. When species are represented by roughly the same number of individuals, those communities show evenness.
Communities with more members of one or more species than others exhibit dominance or unevenness. Species diversity is the result of species richness, evenness, or equitability. Odum et al. defined species diversity as several species per thousand persons in 1960, but Menhinick calculated it as the number of species of the same size in 1964.
Ecosystem diversity refers to the range of forms found in an ecosystem as a result of niche diversity, trophic levels, and ecological processes such as energy flow nutrient recycling, dominant species roles, and numerous biotic interactions.
Diversity aids in the development of more stable ecosystems, and productive environment that can withstand a variety of environmental challenges, such as extended drought.
Alpha, Beta, and Gamma diversities.
Apart from these important diversities, Biodiversity and conservation class 12 notes talk about community diversity with alpha, beta, and gamma diversities.
Within the Community exists Alpha diversity. It is dependent upon the species’ evenness and richness. In Alpha Diversity, variations are only slightly observed as they face a lot of competition, inter-relationship among species, and adjustments.
Beta diversity can be observed between communities. Such diversity is visible along a habitat gradient in a specific geographical area.
The one that explicitly occurs in the ranges of communities over the entire landscape of a geographical territory is defined as Gamma diversity.
Levels & Patterns of Biodiversity
According to Biodiversity and conservation class 12 notes, following are the patterns of biodiversities:
Near the poles, species diversity declines. In comparison to temperate and polar regions, the tropics have a greater diversity of species. The following are the reasons behind this:
For numerous years, the tropical regions have remained unaffected. As a result, species diversity in the tropics has increased.
The climate in the tropics is more stable and predictable. Another reason for greater species variety is because of this. Solar energy contributes to increased production and biodiversity in the tropics.
2. Species Area Relation
Within a region, species richness increases as the investigated area increases, but only to a certain point. For a variety of taxa, such as freshwater fishes, angiosperms plants, and birds, the relationship between the area and species richness is found to be a rectangular hyperbola.
If plotted a graph, the relationship is depicted by a straight line as demonstrated by the equation
log S = log C + Z log A
S= Species richness, A= Area, C = Y-intercept and
Z = slope of the line (regression coefficient)
- The value of Z lies in the range of 0.1 to 0.2 irrespective of the taxonomic group of that region.
- Z value range will be between 0.6 & 1.2 in case of a very large area like continents.
Biodiversity loss & its Reasons
An area’s loss of biodiversity can result in
- Plant output is deteriorating.
- Decreased Drought resistance, environmental challenges, and global warming resistance.
- Variable ecological processes such as water usage, plant yield, and pest and disease cycles.
The responsible factors for causing the loss of biodiversity as per biodiversity and conservation class 12 notes are due to reasons explained by the Evil Quartet.
Habitat Loss & Fragmentation
The most common cause of animal and plant extinction is habitat loss and fragmentation. The Amazon rain forest (the planet’s lungs), which contains millions of species, is being chopped and cleared for soya bean cultivation or conversion to grasslands. When big ecosystems are fragmented as a result of numerous human activities, animals, and birds that require broad territories move and are negatively impacted.
Excessive exploitation of a species, whether it be a plant or an animal, diminishes the size of its population, putting it at risk of extinction. Due to human overexploitation, three subspecies of the dodo, Tiger, star sea cow, and passenger pigeon have been extinct in the previous 500 years.
Alien Space Invasion
Upon alien species entering an environment intentionally or unintentionally, some of them may turn invasive and trigger the extinction of indigenous species. The best example can be understood by Nile perch being introduced into Lake Victoria, East Africa and it led to the extinction of a unique species of cichlid fish in this lake, an assemblage of more than 200 species of this species.
Several marine fish populations are now falling all around the world. Inadvertently, non-native or alien species are frequently employed for commercial and other purposes. They frequently become invasive, limiting the development and survival of native species.
It is the fact that the extinction of one species will automatically cause the other one to become extinct. It can be explained with the example of a mutualistic relationship that exists between the Yucca moth and the Yucca flower. With the extinction of the Yucca Flower, the Yucca moth will also disappear.
Methods to Conserve Biodiversity
Biodiversity conservation refers to the enhancement, preservation, and management of biodiversity in order to reap long-term benefits for current and future generations.
Strategies to preserve biodiversity:
The following two strategies mentioned in Biodiversity and conservation class 12 notes can be used to preserve biodiversity:
In situ conservation refers to the preservation of a range of animal and plant species in their native habitat. Biosphere reserves, hot spots, national parks and sanctuaries, wild forests, and other natural areas are included.
Ex-situ conservation is the protection and preservation of endangered animal and plant species outside of their natural environments. Zoos, aquariums, botanical gardens, and geological museums are among them.
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