BIOLOGY 3 Marks Question

1. Pyramid of number.
2. Pyramid of biomass.
3. Pyramid of energy.

• The pyramid of biomass in sea is inverted.
• The pyramid of energy in sea is upright.

1. Thermal power plants/smelters/other particulate matter releasing industries.

To remove particulate matter.

2. Very very small particulate matter/less than 2.5 micrometres are not removed/velocity of air between plates must be low enough to allow the dust to fall/cannot work without electricity.

1. Production of biomass/energy per unit area in a given time (per year) by plants during photosynthesis.

Depends upon - plant species inhabiting a particular area, environmental factors availability of nutrients, photosynthetic capacity of plants.

2. GPP – R = NPP.

1. Nile perch an exotic predatory fish introduced into Lake Victoria (South Africa) threatens the entire ecosystem of the lake by eliminating several native species of the small cichlid fish species.
2. Introduction of water hyacinth has threatened the survival of many aquatic species in lakes and rivers, as this plant multiplies very fast and clogs the water bodies.
3. Lantana camera has invaded forestlands in many parts of India, and it competes strongly with the native species.

The nutrients, which are present in the ecosystem never get lost, they are recycled again and again indefinitely. The movement of nutrient elements through the various components of an ecosystem is called as nutrient cycling, or also called biogeochemical cycles; (ro-living' geo-rocks, air, water).

Nutrient cycles are of two types based on their reservoir (i.e. storehouse): Gaseous cycle and sedimentary cycle' In both the gaseous and sedimentary cycle, environmental factors like temperature, pH' soil nature and moisture can regulate the rate of release of nutrients into the atmosphere. The function of the reservoir is to meet the deficit, which occurs due to imbalance in the rate of influx and efflux.

1. The first statement shows only the quantity of biomass produced but it does not show the duration and area in which it was produced.
2. The second statement shows quantity and area but it does not show the duration in which it was produced.
3. The third statement is a complete as it shows the quantity, area and duration. Information from the third statement can be used to calculate primary productivity in the farm: in term of biomass produced.

1. The species that invade a bare area are called pioneer species.
2. In a xeric succession the pioneer species are usually lichens then bryophytes, which are succeeded by ferns and some other bigger plants. Lichen produces organic acids which corrodes rock surface and release minerals required for growth. The corroded rock accumulates soil particles by wind and provides substrate for bryophytes and ferns.

1. The sequential, gradual and predictable changes in the species composition in an area are called succession or ecological succession.

Ecological succession is of two types:

1. Primary succession: It begins in areas where no living organisms ever existed. Therefore, the establishment of a biotic community is very slow, e.g., newly cooled lava, bare rock, newly created pond or reservoir.

2. Secondary succession: It begins in areas where natural biotic communities have been destroyed, e.g., abandoned farm lands, buried or cut forests. Since soil is available, it is a faster process.

Difference:

1. Into chemical energy, (in molecular bonds), through a process known as photosynthesis. Most of this energy is stored in compounds called carbohydrates. The plants convert a tiny amount of the light they receive into food energy. When animals eat green plants
2. They consume and absorb some of this energy, which stored as chemical energy in compounds known as fats and protein. Milk from cows is a good source of solar energy
3. (Also an excellent source of essential vitamins and minerals). When we drink milk our bodies convert the energy stored in the milk into energy for running, playing and important metabolic activities
4. We have become “solar powered”!

The rate of decomposition is controlled mainly by the following two factors:

1. Chemical composition of detritus The rare of decomposition is slower, if detritus is rich in lignin and chitin while, it is quicker if it is composed of nitrogen and water-soluble substances like sugars.
2. Climatic factors Temperature and soil moisture are the most important climatic factors that controls decomposition.

Properties:

1. It is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.
2. Being colloidal in nature, it serves as a reservoir of nutrients.
3. It improves the water-holding capacity of soil.

• It does not take into account the same species belonging to two or more trophic levels.
• It is based on the assumption of simple food chain. However, simple food chain never exists in nature. It is the complex food web which exists in nature.
• A food pyramid does not take into account the decomposers. But the fact is, decomposers play important role in nutrient cycle.

Primary succession on rocks:

• Lichens are the pioneer species on a bare area.
• The lichen secretes some acids to dissolve rock and help in weathering and soil formation.
• Later, some small bryophytes invade and hold the small amount of soil.
• The bryophytes are succeeded by herbs, shrubs and ultimately big trees.
• At last, a stable climax forest is formed.
• The xerophytic habitat gets converted into a mesophytic one.