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.

1. Primary succession in water:

• The pioneer species are phytoplanktons.
• The phytoplanktons are replaced by free-floating angiosperms.
• Then, rooted angiosperms invade sedges, grasses and finally the trees.
• At last, a stable climax forest is formed.
• An aquatic habitat is converted into mesic habitat.

2. 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.

1. Ecological succession is the phenomenon in which the structure and composition of communities change in an orderly and sequential manner leading ultimately to the establishment of a climax community.
2. The ecological succession in a forest destroyed by a forest fire will be faster, because, there is already soil (substratum) and organic matter present; some vegetative propagules may also be present and it is secondary succession.
3. In a newly created pond, it is primary succession as there is not much of organic matter or any propagules; hence it will take a very long time.

1. Terrestrial ecosystem: Forest, grassland, desert, etc.

2. Aquatic ecosystem: Pond, lake, river, wetland, estuary, etc.

3. Man-Made ecosystem: A manmade ecosystem is an artificial biological system that is managed and sustained by people.

1. Chemical composition of detritus:

• Decomposition is faster when detritus is rich in nitrogen and water-soluble substances like sugars.
• Decomposition is slow when detritus is rich in lignin and chitin.

2. Oxygen:

• Decomposition is an oxygen-consuming process.
• Anaerobic conditions inhibit decomposition.

1. Trees.
2. Deer and rabbits.
3. Snakes and hawks.

2. As energy flows from one trophic level to the next, approximately 90% of it is lost.
3. Eventually there is not enough energy to support another level.

1. Lichen stage.
2. Moss stage.
3. Annual grass stage.
4. Perennial grass stage.
5. Shrub stage.
6. Climax community.

1. Small short lived plants (r-selection) to large long lived plants (k-selection).
2. Unstable biotic community to stable biotic community.
3. Little diversity to high degree of diversity.
4. Aquatic or dry conditions to mesic conditions.

1. Both producers and consumers die and decompose.
2. Only producers use inorganic nutrients to make organic molecules.
3. Energy does not cycle.

1. The process by which autotrophs convert inorganic materials into organic material with the help of solar energy is called photosynthesis.
2. The green pigment which traps solar energy and converts light energy into chemical energy is chlorophyll.
3. The three pigments, i.e. chlorophyll, carotenoids and xenthophylls together form a complex of pigments in the thylakoid membrane. These complexes work for the absorption of light and its transfer to a reaction centre,

These complexes are called photosynthetic unit or photosystem or pigment system.

1. Primary consumers: The consumers that feed on plants direcdy, are called primary consumers or herbivores.

2. Secondary consumers: Those animals, which ear other animals, who ear plants are called secondary consumers. These are also referred ro as primary carnivores.

3. Tertiary consumers: These are animals who feeds on secondary consumers for their nutrition. These are also referred to as secondary carnivores.

Therefore, due to this interdependence of food/energy between organisms, the chains or webs are formed in the ecosystem.

It is a graphic presentation of aquatic food chain in terms of numbers of producers and consumers at each level.

1. The process of harvesting chemical energy for metabolic activities by oxidising the food molecules is called respiration.
2. The most common substrate used in the process is glucose.
3. ATP or Adenosine Triphosphate is also known as energy currency of the cell.

1. It never takes into account the same species belonging to two or more trophic levels.
2. It assumes a simple food chain, which never exists in nature.
3. In spite of the vital role played by saprophytes/ decomposers, they are not given any position in ecological pyramids.

1. Reed-swamp stage.
2. Submerged plant stage.
3. Marsh-meadow stage.
4. Scrub stage.

Both the hydrarch and xerarch lead to mesic conditions of forest.

1. Reduction in primary productivity. No biomass available for consumption by higher trophic levels/ heterotrophs and hence heterotrophs also die of starvation.
2. Increase in primary productivity and biomass of producers. Carnivore population will subsequently dwindle due to food shortage.
3. Increase in number of herbivores which leads to over-grazing by herbivores, finally resulting in desertification.

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.