Science [1 Mark Questions]

Low rainfall, high temperature, soil erosion and the harsh climate are the factors responsible for scanty vegetation in desert.

Planktons are very minute or microscopic organisms freely floating on the surface of water in a pond, lake, river or ocean.

The group decomposers includes micro-organisms such as bacteria and fungi, that obtain nutrients by breaking down the remains of dead plants and animals. They recycle matter by breaking down the organic remains and waste products of plants and animals. These recycled matter are washed up and enter the soil from where plants absorb the nutrients again. Thus, the decomposers play a very important role in the recycling of nutrients.

It is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable and other are non- biodegradable.

Parasites depends on plants on which they live for food whereas decomposers feed on dead and decaying animals or plants.

Frogs eat up mosquitoes. In the absence of frogs, the number of mosquitoes increase too much and spread malaria.

2. Ecosystem: It is an ecological system consisting of a distinct biotic community and the physical environment (consisting of a number of abiotic factors) both interacting and exchanging materials between them.

Decomposers.

Ozone is formed at the higher level of atmosphere by the action of UV radiation on molecule. High energy UV radiations split apart some oxygen molecules into atomic oxygen which react with molecular oxygen to form ozone molecules.

If 20000J of energy is available to the plants, plants can utilize only 1% of energy. Therefore, plants have 200J of energy with them. Now, according to the 10% law, Plants have 200J of energy of which 20J energy is transferred to the sheep.
Similarly, Sheep have 20J of energy of which 2J energy is transferred to man.

Reuse: We can reuse the empty bottles of jam, pickles etc for the storage purposes.
Recycle: We can recycle old newspapers, aluminum cans etc.

Incineration.

Second trophic level: Insects Fourth trophic level: Snakes.

The various steps involved in food chain are called tropic levels.

CFC – Chlorofluorocarbons. Chlorofluorocarbons released into the air react with ozone gas present in the ozone layer and destroy it gradually.

Natural ecosystems – Grass land and forest. Artificial ecosystems – Parks and Gardens.

Trophic levels.

Animal Bones and Leather Belts.

Kinetic energy.

According to the 10% law, only 10% of the energy entering a particular trophic level of organisms is available for the next higher trophic level. If the energy at the producer level is 100J, the energy at the hawk level in both the food chains can be calculated as under.

1. Plants → Mice → Snakes → Hawks

100J → 10J → 1J → 0.1J

2. Plants → Mice → Hawks

100J → 10J → 1J
So, it is clear that hawks will get 10% more energy in the second food chain compared with the first food chain.

The physical and biological world together is called environment.

Cat.

Biosphere (also environment).

Ozone layer protects the earth and the organisms from the harmful Ultraviolet rays of the Sun. The UV radiations cause health problems like skin cancer, eye problems in animals and also pose many problems to the plants. The depletion of the ozone layer causes more UV radiation to reach the Earth and thus it is a cause of concern.

Ecosystem.

Ponds, Lakes, Rivers, Deserts and Forests are natural ecosystems.

The waste materials which cannot be broken down into non-poisonous or harmless substances in nature are called non-biodegradable waste materials. Example – D.D.T and Plastics.

Producer.

Ultra Violet radiations.

Ozone is formed at the higher level of atmosphere by the action of UV radiation on molecule. High energy UV radiations split apart some oxygen molecules into atomic-oxygen which react with molecular oxygen to form ozone molecules.

Plants are called producers because green plants prepare their own food from simple inorganic substances like carbon dioxide and water by using sunlight energy in the presence of chlorophyll.

Green plants always occupy the first trophic level because they are the producers. They convert the energy of the Sun into a usable form of energy for the next trophic level.

Herbivorous are the second trophic level organisms because they feeds on first trophic level organisms.

Affluent life style is led by most of the people living in cities. Along with growing population, people are migrating to cities getting attracted to the life style. For example: usage of personal vehicles instead of public transport increases consumption of fuel, pollution etc.

When the given substance changes its structure and become unused.

Decomposers are the organisms which convert organic material into inorganic form.

Plankton, fish, crab, shark.

Crop fields, Gardens, Aquarium, Parks are the man-made ecosystems.

Paper bags should be used for shopping because these are biodegradable whereas plastic bags are non- biodegradable.

Trophic level.

Lakes are really a natural ecosystem because it possesses every kind of life in it. The lake holds both abiotic and biotic compounds in it and provides a valid environment to get utilized by each other.

Bacteria and fungi break down the complex organic compounds present in the dead organisms into simpler substances. So they are called decomposers.

When CFC’S reach upper layers of the atmosphere, they cause depletion of ozone layer, and allow harmful UV radiations to reach the surface of the earth to create health hazards.

Second trophic level: Insects.
Fourth trophic level: Snakes.

Biological Magnification.