There are shortest lawn grasses, at the same time redwood trees of California of approximate size 100 m.
We have microscopic bacteria of a few micrometre in size. At the same time, we have a blue whale of approximate sizes of 30.
Variety in Shape:
There are plants like Banyan, guava with branches, while there are plants like coconut and palm which has no branches
There are tiny animals like bacteria, amoeba which can only be seen through a microscope. At the same time, we have gigantic animals like an elephant.
Variety in Body Parts:
Some plants are flowering plants while some plants are non-flowering plants. In some animals limbs are present for locomotion while in some plants flagella or cilia are present. Amoeba moves by forming pseudopodia.
Variety in Life Span:
Some pine trees live for thousands of years while insects like mosquitoes die within a few days.
Variety in Complexity:
Some animals like an amoeba, paramoecium are unicellular while animals like monkey, elephant, human are multicellular.
Variety due to Habitat:
There are some plants like hydria which are freshwater dwelling. Some algae are marine. While trees like Banyan are terrestrial.
Fishes are aquatic (freshwater or marine). Tigers, humans are terrestrial (land dwelling). Birds and monkeys are arboreal (tree dwelling). Frog and tortoise are amphibians i.e. they can live on the land and in the water.
Animals and plants of a desert, snow region, and coastal areas and of same class show differences in their body structure.
Variety due to Mode of Nutrition:
Plants are autotrophic because they are the producer. They produce their own food material.
Animals are heterotrophs. They depend on plants and other animals for their food. They are consumers.
Bacteria are saprophytic. They depend on dead decaying matter for their nutrition. They are decomposers.
Planta like Cuscuta is parasitic. It depends on another plant for nutrition without giving any return to the host plant.
Some animals are vegetarian (e,g. elephant), some are nonvegetarian i.e. carnivorous (e.g. tiger). Human are both vegetarian and non vegetarian(omnivorous).
Variety due to Colours:
We can find colourless or even transparent worms, At the same time, we can find brightly coloured birds and flowers.
Variety in the Same Class:
There is more variety in the body structure, life patterns. and habitats of species that belong to same class.
Let us consider class Pisces of the animal kingdom which includes fishes of all kind.
Some fishes are of fresh water while some leaves in seawater (marine). Some have a tiny shape while some are gigantic. Some use tail fin for changing direction while some use it as a weapon of self-defence. Some have a shorter life while some have a very long life.
Thus variety in habitat, size, body structure and lifespan can be observed in the same class.
The basis of Classification:
This variety of life around us has evolved on the earth over millions of years. We look for similarities among the organisms, which will allow us to put them into different classes and then study different classes or groups as a whole. For this, we need to decide which characters decide fundamental differences among organisms. This would form the basis of classification.
Importance of Biodiversity:
Each organism in an ecosystem has a special role to play, hence biodiversity Increases ecosystem productivity.
It promotes soil formation and prohibits soil erosion.
It provides more fruit resources.
It provides employment to local people by offering an environment for recreation and tourism.
It Provides medicinal resources and pharmaceutical drugs.
It provides security against natural disaster and provides speedy recovery from them.
They contribute to environmental and climatic stability.
It reduces pollution.
It protects freshwater resources.
It is required for breeding programmes in agriculture, horticulture, sericulture, and apiculture.
Biodiversity maintains the balance of the ecosystem.
As the human being is part of the ecosystem any damage to biodiversity will cause damage to the support system and it may lead to a threat to human existence. Hence biodiversity should be conserved.
Threat to Biodiversity:
Increase in Human Population:
Due to increase in the population more and more land is required for agriculture, housing, for making roads, constructing a dam, bridges, electrical power stations, and industries.
In last 70 years, there is a rapid decline in biodiversity due to above reasons.
Deforestation and Overgrazing:
Indiscriminate cutting of trees for wood causes deforestation. Overgrazing by cattle and sheep causes a decline in grassland. This creates a loss of habitat for wild animals.
Insecticides used in agricultural practices, toxic elements released by industries, petroleum products pollute water and air.
The species which are unable to tolerate this pollutant level in air or water get eliminated.
Introduction of Exotic Species:
An introduction of a new species from some other area in a new area is called introduction of exotic species. These species compete with native species in that area. It may lead to the extinction of local species.
Global warming, Increase in temperature, changing rain pattern and melting glaciers are causing a great danger to biodiversity.
International trade in wildlife and wildlife products for decorative, medical purpose has threatened many species.
Role of Biodiversity:
Biodiversity maintains equilibrium in nature because of which all kinds of organisms are able to survive. The bacteria and fungi recycle organic matter from dead decaying organisms or living organisms to feed other diverse organisms. Green plants and algae trap solar energy during photosynthesis and produce food which is utilized by all living organisms. Insects and bats pollinate flowers. Animals are medium for dispersion of seeds. Ecosystems such as the forests, deserts, aquatic bodies, wetlands are self-sufficient and sustain their own typicality. Some ecosystems are part of their unique food chains and food webs.
Measures to Conserve Biodiversity:
It is the duty of every human being to protect biodiversity. Conservation keeps ecosystems stable. Many plants have become extinct. Some are close to extinction. Endangered species need to be protected.
Fish and mollusc stocks have to be conserved and prevented from overexploitation by humans for food.
Government and non-government organizations are working for the conservation of biodiversity through legislation. Banning animal killing, banning illegal tree cutting, making zoos, national parks, botanical gardens, biosphere reserves etc. “Operation Tiger” and “Operation elephants” are projects that have helped in preventing the decline in their numbers due to habitat destruction.