NIOS Class 12 Biology Chapter 25 Solution – Principles of Ecology
NIOS Class 12 Biology Solution Chapter 25 Principles of Ecology . NIOS Class 12 Biology Chapter 25 Question Answers Download PDF. NIOS Class 12 Biology Notes.
Board |
NIOS |
Class |
12th (Higher Secondary) |
Subject |
Biology |
Topic |
Question Answer, Solution, Notes |
INTEXT 25.1
1.) Name the various levels of organizations.
Ans: The levels of organization are as follows Genes → Cell → organ → organism → Species Population → Community → Ecosystem → Biome → Biosphere.
2.) Define the term ecology.
Ans: Ecology is the scientific study of the relationship and interactions between organisms and their environment. The term ecology is derived from a Greek word Oekologie where “oikos” meaning “household”and “logos” means “the study of”
3.) What are the three physical systems that support life on earth?
Ans: Soil, water and air are the three physical systems which provide material essential for life
4.) Name the major components of the environment.
Ans: The major components of the environment are Abiotic which are Non-living components and Biotic which are Living components
5.) Enumerate the various physical factors of the environment
Ans: light, temperature, humidity, precipitation, pressure and soil profile are physical factors of the environment.
6.) Why is habitat called the address of organisms and its niche ‘the profession’?Justify.
Ans: A population is an assemblage of similar organisms belonging to the same species, living together at one place at a given time. A population always lives a specific place known as its habitat. Many different species with similar requirements may share a habitat. For example, a single ocean as a habitat may support a whale, a sea-horse, seal, phytoplankton, sea weeds, therefore habitat is called the address of organisms
7.) What do we mean by ‘fins are an adaptation of fish to aquatic life’? Explain
Ans: ‘Fins are an adaptation of fish to aquatic life’ because it is mode of life of an organism that allows it to survive in a aquatic environment.
INTEXT 25.2
1.) A population with equal number of births and deaths will show:
(a) Acceleration phase of growth (b) Plateau phase
(c) Exponential growth phase (d) Initial phase of growth
Ans: (b) Plateau phase
2.) When population reaches carrying capacity:
(a) Mortality rate = Birth rate (b) Mortality rate > Birth rate
(c) Mortality rate < Birth rate
Ans: (a) Mortality rate = Birth rate
3.) Human population shows
Ans: (a) S-shaped growth curve
INTEXT 25.3
1.) Define an ecosystem.
Ans: An ecosystem is made up of a biological community and its nonliving surroundings in terms of energy and matter. An ecosystem can be as small as a puddle of water, a stream, a patch of woods, a complete forest, or a desolate area.
2.) What are the main components of an ecosystem?
Ans: Main components are Biotic Abiotic (Producers) light ,Consumers, Temperature Decomposers Inorganic substances organic compounds
3.) Give reason, why are decomposers necessary in an ecosystem?
Ans: Decomposers are necessary in an ecosystem to breakdown products of dead animals and plants tissue. In a food chain, they make up the top trophic level.
4.) What is the role of decomposers in nature?
.Ans: They comprise the top trophic level of the food chain. Decomposers are creatures that consume dead organic matter, also known as detritus, from all trophic levels and aid in the recycling of nutrients. Bacteria, fungi, and mites are a few examples of decomposers.
5.) Why are plants called autotroph and animals called heterotrophs?
.Ans: Plants have the ability to absorb solar energy and convert it into food energy. As a result, they grow their own food. animals can’t produce their own food, thus they must eat either vegetation or other creatures.
6.) Give one example of food chain.
.Ans: Grasses Grasshopper Frogs Snakes Hawk/Eagle
7.) Name the trophic level frog belongs to.
.Ans: The frog belongs to Secondary consumer Carnivores. Carnivores are creatures that eat other creatures or their tissues.
8) Snake can be both a secondary as well as tertiary consumer Justify
Ans: Snake are both secondary and tertiary Since the snake eats the frog, another carnivore, it is a tertiary consumer.
INTEXT 25.4
1.) What can be the maximum number of steps in a food chain?
Ans: There are upto five steps in a food chain. Each step in the food chain is called trophic level
2.) Why is energy flow linear in ecosystem?
Ans: The producer fixes the energy from sun radiation in the form of food.
The consumers at various trophic levels receive this energy. Energy is utilised by each trophic level member for metabolism, and only leftover energy is transferred on to the next trophic level.
3.) Define :
(a) biomass : The producers transform the energy, which enters the environment as solar radiation, into biomass . The biomass of plants, which they store as food, is what gives them their chemical energy.
(b) pyramid of number : graphical representation of the standing crop expressed as number, biomassor energy is called pyramid of number
4.) What is meant by community stratification?
Ans: Community stratification is the term for the vertical and horizontal distribution of plants in an ecosystem.
INTEXT 25.5
Fill in the blanks
(a) The relationship between two organisms where one receives benefits at the cost of other is known as .Commensalism
(b) A group of several species living together with mutual tolerance or adjustment and beneficial interactions in a natural area is known as Community.
(c) A force that acts against maximum population growth is .Environmental resistance
(d) Association between insect polinated flowers and pollinating insect is an association termed as .Pollination
INTEXT 25.6
1.) Define alpine tundra ecosystems.
Ans: Alpine tundra are high mountain peaks above the forest line are home to Alpine tundra. Mountain ranges can be found anywhere, therefore alpine tundra experiences day and nighttime temperature changes.
2). Give two examples of plants of tundra.
..Ans: Cotton grass, sedges, dwarf leath, willows, birches and lichens are the plants of tundra.
3.) Give two common characteristics of tundra and desert biome.
Ans (i) form an extreme condition in sequence of ecosystems with respect to the climatic condition
(ii) Productivity is low
4.) Names of three main types of forests.
Ans: 1. Tropical rain forest temperature.
2.) Deciduous boreal or north.
3.) Coniferous rain forest.
5). Where are savannas found?
Ans: Tropical grasslands are called Savannas. They are found in Eastern Africa, South America, Australia and India
6.) What are deciduous trees?
Ans: In deciduous forests, trees lose their leaves in the autumn, and new foliage emerges in the spring. They are most common in Australia, far eastern Russia, far western China, northwest, central, and eastern Europe, eastern North America, north China, Korea, and Japan.
INTEXT 25.7
1.) What are plankton?
.Ans: Free floating microscopic organisms are called plankton
2.) Name two phytoplanktons and two bottom dwellers in fresh water ecosystem.
Ans: Spirogyra, Ulothrix and hydra, worms.
3.) What is the maximum pressure in ocean.
Ans: In oceans, pressure rises with depth. At the greatest depth, it is 1000 atmospheres below the surface, which is 1 atmosphere.
4.) Give an example of
(a) wet land : swamps, marshes and mangroves
(b) lotic type of ecosystem.: streams, rivers, springs
INTEXT 25.8
1.) What does the following sequence represent:
Blue green algae ⎯→ Crustose lichens
↓
shrubs ←⎯ mosses ←⎯ Foliose lichens
↓
Dicotyledonous trees
- a) Ecological succession
(b) Genetic drift
(c) Phylogenetic trend
(d) A food pyramid
Ans: a) Ecological succession
2.) A community which starts succession in a habitat is:
(a) Pioneer community
(b) Social community
(c) Biotic community
(d) Ecosere
Ans: (a) Pioneer community
3.) In ecological succession, beginning from pioneer and ending in climax community, the biomass shall
(a) decrease
(b) increase and then decrease
(c) decrease and then increase
(d) Increase continuously
Ans: (d) Increase continuously
INTEXT 12.9
1.) Define nutrient cycle.
Ans: Biogeochemical or nutrient cycle refers to the process by which nutrients cycle through the biosphere. It involves the transfer of nutritional elements between the various ecological parts.
2.) Where are the bulk of nutrient stored in an ecosystem?
Ans: The bulk of nutrient stored In the Reservoirs pool in an ecosystem
3.) Name the nutrient cycle where atmosphere acts as the main reservoir.
Ans: In Gaseous cycle the atmosphere acts as the main reservoir
4.) List any two human activities that have led to increase in atmospheric CO2.
Ans: Human activities including industrialization, urbanisation, and rising automobile use are causing carbon dioxide to continuously rise in the atmosphere.
5.) Name the reservoirs for water cycle.
Ans: Polar ice caps and water present deep in the oceans
6.) How do humans affect the phosphorus cycle?
Ans: Human affects the phosphorus by using the fertilizer for plants.
7.) How do the sea birds contribute to the phosphorus cycle?
Ans: Sea birds’ guano deposits play a significant part in returning phosphorus to the cycle.
TERMINAL EXERCISE
1.) What are the three physical life support systems on the planet earth?
Ans: The three physical systems that make up the planet—soil, water, and air—which supply the raw materials for life.
2). Name the various biotic and abiotic components of the environment
Ans: Abiotic components are temperature, light, pressure, humidity, precipitation, wind, mineral elements of soil and composition of air
Biotic components are all living organisms found in the environment including plants, animals and microorganisms.
3.) Give differences between natural and human modified ecosystem
Ans: There are several types of natural ecosystems, including ponds, lakes, meadows, marshlands, grasslands, deserts, and woods. Our natural resources supply us with food, fuel, fodder, and medicines while, Humans create and maintain ecosystems that have been altered for their benefit.
4.) Why is the number of trophic levels restricted to four or five in a food chain?
Ans: The species combination, stratification, and food relationships of an ecosystem can serve as representations of its key structural features therefore trophic levels restricted to four or five in a food chain
5.) Give only two differences between fresh water and marine biome.
Ans: (i) Fresh water is land-based water that is constantly cycling and contains little salt , while marine biome is ocean based water
(ii) Fresh water consist of less amount of salt , while marine biome contains large amount of salt.
6). What will happen if all the floating animals are removed from a lake ecosytem?
Ans: If all the floating animal are removed from a lake , it will disturb the ecosystem by disturbing the food chain of the particular area.
7.) What are the benefits of natural ecosystems?
Ans: There are several types of natural ecosystems, including ponds, lakes, meadows, marshes, grasslands, deserts, and woods. They are our natural resources, and they give us access to things like food, fuel, fodder, and medicines. It maintainthe biodiversity of the earth, provide food and water .
8.) Give two differences between energy flow and biogeochemical cycle in an ecosystem.
Ans: (i) The cycling of the nutrients in the biosphere is called biogeochemical or nutrient cycle, while the flow of energy through living being is the energy flow.
(ii) In biogeochemical the chemical are recycles within the ecosystem, while while energy have unidirectional flow.