Maharashtra Board Class 12 Biology Chapter 15 Biodiversity Conservation and Environmental Issues PDF Download

Biodiversity, Conservation and Environmental Issues

Diversity is variety. This variety of life is called biodiversity. Biodiversity includes a vast array of species of microorganisms - viruses, algae, fungi, plants and animals occurring on Earth, either in terrestrial or aquatic habitat and the ecological complexes of which they are part.

The diversity is with respect to size (microscopic to macroscopic), shape, colour, form, mode of nutrition, type of habitat, reproduction, motility, duration of life cycle span, etc. This is actually due to the attempt of living beings to accommodate with different environmental conditions (like climatic, edaphic, topographic, geographic, etc.) or situations, solely for their survival and perpetuation. In doing so, living organisms adapt themselves to overcome different situations and thus develop distinct but different features and that has actually lead to the diversity in them. The diversity in features become infused in the life cycle. In short, these adaptations in different environments serve as basis for diversity.

Definition of Biodiversity: It is the part of nature which includes the differences in the genes among the individuals of a species; the variety and richness of all plants and animal species at different scales in a space - local regions, country and the world; and the types of ecosystem, both terrestrial and aquatic, within a defined area.

The term biodiversity was actually coined by Walter Rosen (1982) but the term was popularised by sociologist Edward Wilson to describe combined diversity at all the levels of biological organisation.

Biodiversity that we see today, is the outcome of over 3.5 billion of years of evolutionary history mainly influenced by natural processes and of late by influence of humans.

In this chapter, we shall study the basic concepts of biodiversity such as levels and patterns of biodiversity, expanse, importance, loss and conservation methods and efforts undertaken.

15.1 Levels of Biodiversity

Diversity of living world can be observed at various levels, ranging from molecular to ecosystem level. Major hierarchial and interrelated levels are genetic diversity, species diversity (community), and ecosystem diversity (ecological).

Teacher's Note

Biodiversity means all different types of plants and animals in one place. For example, a mango tree, a coconut tree, and a neem tree together have more biodiversity than just mango trees alone.

Exam Trick

Remember three levels: Genetic = genes in one animal, Species = different types of animals, Ecosystem = different habitats like forest and desert. Just like your family (genetic), your school (species), and your city (ecosystem).

Points to Remember

Biodiversity is the variety of all living things on Earth.
There are three levels of biodiversity: genetic, species, and ecosystem.
Genetic diversity means different genes in the same animal type.
Species diversity means many different types of animals and plants.
Ecosystem diversity means different types of habitats like forests and deserts.

a. Genetic Diversity

It is the intraspecific diversity. It is the diversity in the number and types of genes as well as chromosomes present in different species and also the variation in the genes and their alleles in the same species. It includes variation within a population and diversity between populations that are associated with adaptation to local conditions. Genetic variations (e.g. allelic genes) lead to individual differences within species. Such variations pave way to evolution. They also improve chances of continuation of species in the changing environmental conditions or allow the best adapted to survive. Existence of subspecies, races are examples of genetic diversity. Greater the diversity, better would be sustenance of a species. You know about 1000 varieties of mangoes and 50,000 varieties of rice or wheat in India.

Another case of genetic diversity is: a medicinal plant Rauwolfia vomitoria which secretes active component reserpine, is found in different Himalayan ranges. This plant shows variations in terms of potency and concentration of active chemical, from location to location.

Genetic diversity or variability is essential for a healthy breeding population of a species.

Teacher's Note

Genetic diversity is small differences between animals of the same type. For example, some mangoes are sweet and some are sour because they have different genes inside them.

Exam Trick

Genetic diversity = different genes in same species. Remember: Why do brothers and sisters look different even though they are from the same parents? Because of genetic diversity!

Points to Remember

Genetic diversity means differences in genes within the same type of animal or plant.
More genetic diversity helps animals survive changes in nature.
Different varieties of rice and mango show genetic diversity.
Without genetic diversity, animals cannot adapt to new environments.
Subspecies and races are examples of genetic diversity.

b. Species Diversity

It is the interspecific diversity. The number of species of plants and animals that are present in a region, constitutes its species diversity. Some areas or regions are richer in species than in the other regions. Species diversity deals with variety of species (species richness) as well as number of individuals of different species (species evenness) observed in area under study. E.g. amphibian species diversity is more in western ghats than in eastern ghats. Natural undisturbed tropical forests have much greater species richness than monoculture plantation of timber plant, developed by forest plantation. India is one among 15 nations that are rich in species diversity.

Teacher's Note

Species diversity means how many different types of animals and plants live in one place. For example, if a forest has tigers, deer, birds, and snakes, it has high species diversity.

Exam Trick

Species diversity = how many different animal types in one area. Think of a garden with only roses (low diversity) versus a garden with roses, marigolds, and dahlias (high diversity).

Points to Remember

Species diversity is the number of different types of animals and plants in an area.
Tropical forests have more species diversity than cold forests.
Western ghats have more amphibian species than eastern ghats.
A natural forest has more species diversity than a single crop farm.
India is one of the 15 countries with the most species diversity.

c. Ecological (Ecosystem) Diversity

It is related to the different types of ecosystems/habitats within a given geographical area. There are a large variety of ecosystems on Earth having their own complement of distinctive interlinked species, based on the differences in the habitat. It can be described for a specific geographical region. Generally, there may be one or many different types of ecosystems in a region. Thus, ecosystem diversity is very high in India while it is quite low in Norway. In India, we can find a great variety of ecosystems - deserts, rain forests, deciduous forests, estuaries, wetlands, grasslands, etc. The Western ghats show great ecosystem diversity while regions like Ladakh and Rann of Kutch do not show variance like we observe in Western ghats.

The diversity of life at all the three levels is now rapidly being modified by modern man.

Teacher's Note

Ecosystem diversity means different types of habitats in one place. India has deserts, forests, and wetlands all in one country, so it has high ecosystem diversity.

Exam Trick

Ecosystem diversity = different types of homes for animals. Remember: A rainforest is different from a desert. Each needs different plants and animals.

Points to Remember

Ecosystem diversity means different types of habitats in one area.
India has high ecosystem diversity with deserts, forests, and wetlands.
Norway has low ecosystem diversity as it is mostly cold and snowy.
Western ghats show great ecosystem diversity in India.
Each ecosystem has its own special plants and animals.

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