NIOS Biology Intext Solutions Chapter 25
INTEXT QUESTIONS 25.1
1. Name the various levels of organizations.
Ans: Genes → Cell → Organ → Organism → Population → Community
2. Define the term ecology.
Ans: The Study of animals and plants in relation to their habit and habitats.
3. What are the three physical systems that support life on Earth?
Ans: Atmosphere, lithosphere, and hydrosphere
4. Name the major components of the environment.
Ans: (i) Abiotic (ii) Biotic
5. Enumerate the various physical factors of the environment
Ans: Light, temperature, humidity, precipitation, pressure, and soil profile
6. Why is habitat called the address of organisms, and its niche, the profession? Justify.
Ans: Habitat is thus the physical environment in which an organism lives. Thus, a single ocean as a habitat may support a whale, a sea-horse, a seal, phytoplankton, seaweeds ,and many other kinds of organisms. Niche is the functional characteristics of a species in its habitat. It is the sum of all the activities and relationships of a species on how it uses the resources in the habitat for its survival and reproduction.
7. What do we mean by ‘fins are an adaptation of fish to aquatic life’? Explain.
Ans: An adaptation is the appearance, behaviour, structure, or mode of life of an organism that allows it to survive in a particular environment. It helps the organism adapt to the changing environment. Thus, fins are a type of adaptation for fish to live in their aquatic habitat.
INTEXT QUESTIONS 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 the population reaches the 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:
(a) S-shaped growth curve
(b) J-shaped growth curve
(c) Z-shaped growth curve
Ans: (a) S-shaped growth curve
INTEXT QUESTIONS 25.3
1. Define an ecosystem.
Ans: An Ecosystem is a unit to study ecology/a functionally independent unit to study. The interrelation between biotic and abiotic components.
2. What are the main components of an ecosystem?
Ans: Main components
- Biotic components: Producers, consumers and decomposers.
- Abiotic components: Light, temperature, inorganic substances and organic compounds.
3. Give reason, why decomposers are necessary in an ecosystem.
Ans: to break down products of dead animals and plant tissue.
4. What is the role of decomposers in nature?
Ans: Decomposers are the organisms that feed on dead organic matter, called detritus, of all the trophic levels and help in recycling the nutrients.
5. Why are plants called autotrophs and animals called heterotrophs?
Ans: Plants are capable of capturing solar energy and transforming it into food energy. Thus, they produce their own food. Animals depend upon plants or other animals for food, as they cannot produce their own food.
6. Give one example of food chain.
Ans: Grass → Grasshopper → Frog → Snake → Hawk/eagle
7. Name the trophic level frog belongs to.
Ans: Secondary level consumer
8. Snake can be both a secondary as well as a tertiary consumer. Justify.
Ans: A Snake can feed on a rat, and then it is a secondary consumer. It can also feed on a fro,g and then it is a tertiary consumer.
INTEXT QUESTIONS 25.4
1. What can be the maximum number of steps in a food chain?
Ans: Up to five (5)
2. Why is energy flow linear in an ecosystem?
Ans: Energy from solar radiation is fixed in the form of food by the producer. This energy is passed on to the consumers of different trophic levels. At each trophic level, energy is used by the member for metabolism, and only leftover energy is passed on each trophic level (10%).
3. Define : (a) biomass (b) pyramid of number.
Ans: (a) Biomass is the total volume of organic content of an organism. The pyramid of numbers
(b) Pyramid of numbers is a representation of the total number of individual organisms in each trophic level.
4. What is meant by community stratification?
Ans: Stratification is the vertical and horizontal distribution of various species occupying
different levels.
INTEXT QUESTIONS 25.5
1. Fill in the blanks
(a) The relationship between two organisms where one receives benefits at the cost of other is known as ______.
Ans: Commensalism
(b) A group of several species living together with mutual tolerance or adjustment and beneficial interactions in a natural area is known as ______ .
Ans: Community
(c) A force that acts against maximum population growth is ______ .
Ans: Environmental resistance
(d) Association between insect polinated flowers and pollinating insect is an association termed as _____.
Ans: Pollination
INTEXT QUESTIONS 25.6
1. Define alpine tundra ecosystems.
Ans: It’s an ecosystem that occurs on high mountain peaks above the tree line. Environmental conditions are very severe and show day and night temperature variation.
2. Give two examples of plants of tundra.
Ans: Cotton grass, sedges, dwarf leath, willows, birches, and lichens (any two).
3. Give two common characteristics of tundra and desert biome.
Ans:
- Both of them have very harsh climatic conditions.
- Scarce vegetation.
4. Names of three main types of forests.
Ans:
- Tropical rainforest temperature.
- Deciduous boreal or northern.
- Coniferous rain forest.
5. Where are savannas found?
Ans: Eastern Africa, South America, Australia, and India (any two).
6. What are deciduous trees?
Ans: Trees that shed their leaves in autumn and grow new foliage during spring.
INTEXT QUESTIONS 25.7
1. What are plankton?
Ans: Free-floating microscopic organisms
2. Name two phytoplanktons and two bottom dwellers in freshwater ecosystem.
Ans: diatoms, algae, prawn, crabs, snail (any two)
3. What is the maximum pressure in ocean?
Ans: 1000 atmosphere
4. Give an example of (a) wetland (b) a lotic type of ecosystem.
Ans:
- (a) swamps, marshes, and mangroves (any one)
- (b) streams, rivers, springs (any one)
INTEXT QUESTIONS 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 QUESTIONS 25.9
1. Define nutrient cycle.
Ans: Movement of nutrient elements through the various components of an ecosystem is called the nutrient cycle.
2. Where are the bulk of nutrient stored in an ecosystem?
Ans: In the Reservoirs pool
3. Name the nutrient cycle where atmosphere acts as the main reservoir.
Ans: Gaseous cycle
4. List any two human activities that have led to increase in atmospheric CO2.
Ans: Industrialization, urbanization, increased use of automobiles (any two)
5. Name the reservoirs for water cycle.
Ans: Polar ice caps and water are present deep in the oceans.
6. How do humans affect the phosphorus cycle?
Ans: Excessive use of synthetic fertilizers is one way humans affect the phosphorus cycle. Plants cannot fully utilize this phosphorus, and the unused part results in run-offs to various reservoirs, where it causes eutrophication.
7. How do the sea birds contribute to the phosphorus cycle?
Ans: Seabirds play an important role in bringing back phosphorus to the cycle through their guano deposits.
Additional Study Materials
- Chapter 19 Reproduction in Plants
- Chapter 20 Growth and Development in Plants
- Chapter 21 Reproduction and Population Control
- Chapter 22 Principles of Genetics
- Chapter 23 Molecular Inheritance and Gene Expression
- Chapter 24 Genetics and Society
