BIOLOGY [3 marks Question Answer]

We must always cany our rubbish home after visiting a picnic spot because if we throw the wastes like plastic bottles, cans, wrappers there, it will not only make the place look awful but also lead to land pollution as plastics and polythenes are non-biodegradable waste i.e. cannot be decomposed by bacteria. It can also become a breeding ground for disease causing insects and rodents. Some rubbish like glass bottles/ cans can cause injuries to others also.

Plants depend upon animals for:
a. Pollination and dispersal of seeds.
b. Nutrients/mirierals in soil formed by decomposition of animal excreta and dead organisms.
c. Caroon-aioxiue reieaseu oy aiimiais uuring icspuauuu for photosynthesis.

Plants, animals and microorganisms living in the pond are its biotic components. Green plants such as algae and water lily are producers. Small animals like tadpoles, snails and insects eat plants and form primary consumers. Larger animals such as fish and frogs who eat the primary consumers, are called secondary consumers.
The bacteria and fungi are decomposers as they feed on dead plants and animals and release simple nutrients into the environments.
Non-living or abiotic component of pond ecosystem include light, water, temperature and dissolved oxygen carbon dioxide and other gases. Plants use dissolved carbon dioxide for preparing their food. They release oxygen, which is used for respiration by animals and by bacteria for decomposition of dead matter. Hence, pond is an example of ecosystem where biotic and abiotic components interact in a habitat.

Any increase in the concentration of green house gases lead to enhanced trapping of heat in the atmosphere and rising of temperature across the earth which is called global wanning. We can prevent global warming by checking the concentration of green house gases like carbon dioxide, methane, nitrous, oxide, ozone etc in the air. Steps to prevent this are :

• Plant more trees to increase forest cover. Plants absorb carbon dioxide.
• Increase use of renewable energy sources such as wind, water and Sun instead of coal, petrol, etc.
• Reduce, reuse and recycle household items.
• Avoid using plastics, polythene and other non-biodegradable articles.

Animals are dependent on plants as :
a. Herbivores depend on plants for their food.
b. Some animals depend on trees for their shelter e.g. Ants, birds, monkeys.
c. Animals also depend on plants for oxygen necessary for respiration.

As only green plants can trap energy from the Sun, all food chains start with plants or producers and energy is transfered through these chains. Solar energy is converted into the chemical energy of food by green plants. Some energy gets stored in plants and rest is used up by them. When plants are eaten by herbivores, the energy stored in them gets transferred to herbivores.Again, herbivores use up some energy and store a part of it. This stored energy is further transferred to camivororous animals when they eat herbivores. Thus, energy passes on from producers to herbivores and then to carnivores as one organism eats the other. The flow of energy is always in one direction and only 10% of energy is transferred to the next level.
Example :
Sun
↓
Grass (Producer)
↓
Rabbit (Primary consumer)
↓
Snake (Secondary consumer)
↓
Eagle (Tertiary consumer)

Factors making earth a habitable planet are :

• Optimum distance from the sun-which makes the earth neither too hot nor too cold.
• Presence of atmosphere – Which has essential gases like oxygen, carbon dioxide, nitrogen, etc.
• Presence of water.
• Gravitational force – Which holds atmosphere and water in place.
• Presence of minerals – Which are required for the growth and sustenance of plant and animal life.

Consumers :
a. They are organisms that cannot make their own food and depend on either plants or other animals for their food.
b. They are also called heterotrophs.
c. e.g. deer, tiger, vulture.
d. They come between producers and decomposers in a food chain.
Decomposers :
a. They are micro-organisms and worms that feed upon the remains of dead plants and animals for energy and return the nutrients to the soil.
b. They are also called nature’s scavengers.
c. e.g. bacteria, fungi, earthworm.
d. They end a food chain.

Producers :
a. They can make their own food using solar energy.
b. All green plants perfor – ming photosynthesis are producers.
c. They are also called autotrophs.
d. A food chain always starts with a producer.
Consumers :
a. They cannot make their own food and depend on plants and other animals for it.
b. All animals, birds, microbes are consumers.
c. They are also called heterotrophs.
d. They come after producer in a food chain.

Hydrosphere :
a. It forms the part of the earth which is made up of water.
b. It includes water in all forms in the form of pond, ocean, glacier, lakes etc.
Atmosphere :
a. The mixture of gases surrounding the earth surface form atmosphere.
b. It includes all gases like oxygen, nitrogen, carbon- dioxide and also water vapours.