a) Biodiversity:
(i) Biodiversity or biological diversity refers to a wide variety of living organisms (plants, animals and other micro organisms) which live in a habitat.
(ii) It is highly influenced by topography climate as well as human activities.
(iii) It represents the strength of the biological resources of a place on earth.
(iv) In biodiversity, each species, no matter how big or small, has an important role to play in the ecosystem.
(v) It maintains the ecological balance and facilitates social benefits such as tourism, education, research etc. over an area.
b) Loss of biodiversity
(i) The extinction of species (flora and fauna) due to human and natural influences is called loss of biodiversity.
(ii) The biodiversity loss has a great impact on mankind and also affects land, water, air etc.
(iii) Habitat destruction due to deforestation, population explosion, pollution and global warming are the major cause for loss of biodiversity.
(iv) Sometimes, habitat loss is so severe or happens so quickly that it results in a species being eliminated from the planet.
(v) Scientists are still trying to decide what caused the mass extinction of dinosaurs.

An ecological region that has lost more than 70% of its original habitat is considered a hot spot.

(i) Terrestrial biomes is a group ofliving organisms that live and interact with one another on land.
(ii) They are mainly determined by temperature and rainfall.
(iii) Some of the major terrestrial biomes of the world are
a. Tropical Forest Biomes
b. Tropical Savanna Biomes
c. Desert Biomes
d. Temperate Grassland Biomes and
e. Tundra Biomes

(i) Bio diversity refers to a wide variety of Iiving organisms, which live in a habitat.
(ii) It is highly influenced by topography, climate as well as human activities.

(i) Biosphere, the fourth sphere of the Earth, is a life supporting layer that exists on the earth's surface.
(ii) This layer on earth encompasses the Lithosphere, Hydrosphere and Atmosphere.
(iii) It includes flora and fauna that thrive on or near the earth's surface.
(iv) Biosphere harbours all ecosystems on the earth and sustains life forms including mankind

This layer on earth encomposses the Lithosphere, Hydrosphere and Atmosphere. Biosphere is made up of different eco-systems.

(i) Producers are self nourishing components of the ecosystem.
(ii) Hence they are called autotrophs.

c) A is true; R is false

b) Both assertion(A) and reason (R) are true; R does not explain A

Aquatic biome is a group of living organisms that live and interact with one another and its aquatic environment for nutrients and shelter. It is broadly classified as fresh water biomes and marine biomes.
A. Fresh water Biomes:
(i) Fresh water biomes comprises lakes, ponds, rivers, streams, wetlands etc.
(ii) It is influenced by various abiotic components such as the volume of water, water flow, composition of oxygen, temperature, etc.
(iii) Humans rely on freshwater biomes for drinking water, crop irrigation, sanitation and industry.
(iv) Water lily, lotus, duck weeds etc. are the common plants found here.
(v) Trout, salmon, turtles, crocodiles etc. are the animals found here.
B. Marine Biomes:
(i) They are the largest aquatic biomes on earth.
(ii) They are continuous bodies of salt water and provide a wide range of habitats for marine plants and animals.
(ii) Coral reefs are a second kind of marine biomes within the ocean.
(iv) Estuaries, coastal areas where salt water and fresh water mix, form a third unique marine biome.
(v) As water provides maximum mobility to marine organisms, nutrients are circulated more quickly and efficiently here than the terrestrial biomes.
(vi) Apart from animals, plants such as kelp, algae, phytoplankton etc. also grow in water.
(vii) Some of the threats and issues to aquatic biomes are overfishing, pollution and rise in sea level.

(i) An ecosystem consists of three basic components, namely
a) Abiotic components,
b) Biotic components and,
c) Energy components
a) Abiotic Components
Abiotic components include the non-living, inorganic, physical and chemical factors in the environment. Eg. Land, Air ,Water, Calcium, Iron etc.
b) Biotic Components
(i) Biotic components include plants, animals and micro organisms.
(ii) Biotic components can be classified into three categories: (1) Producers, (2) Consumers and (3) Decomposers.
(iii) Producers are self nourishing components of the ecosystem. Hence they are called Autotrophs.
(iv) They are found both on land and water. Eg. Plants, Algae, Bacteria etc.
(v) Consumers are those that depend on producers, directly or indirectly. Hence they are called Heterotrophs.
(vi) Decomposers are some organisms that are incapable of preparing its own food. They live on dead and decaying plants and animals. Hence they are called Saprotrophs.
c) Energy Components
(i) All organisms in the biosphere use energy to work and convert one form of energy into another.
(ii) The Sun is the ultimate source of energy for the biosphere as a whole.
(iii) The producers, consumers and the decomposers contribute a lot to the energy flow in an ecosystem.