WBBSE Class 9 Life Science Solutions Chapter 5.1 Ecology and Ecological Organisations

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 5.1 Ecology and Ecological Organisations offer valuable context and analysis.

WBBSE Class 9 Science Chapter 5.1 Question Answer – Ecology and Ecological Organisations

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Who first coined the term ‘ecology’?
Answer:
Famous ecologist, Ernst Haeckel (1869), coined the term ‘ecology’.

Question 2.
Which level of ecology deals with the interaction of a species with the environment?
Answer:
Population level of ecology deals with the interaction of a species with the environment.

Question 3.
Which level of ecology deals with the interaction of two or more species?
Answer:
Community level of ecology deals with the interaction of two or more species.

Question 4.
Give an example of effect of light on plants.
Answer:
Long day plants (such as mustard, radish etc.) require light for more than 12 hours for flowering.

Question 5.
Which type of plants are adapted to survive in bright sunlight?
Answer:
Heliophytes, such as pine trees, are adapted to survive in bright sunlight.

Question 6.
Which type of plants are adapted to survive in low sunlight?
Answer:
Sciophytes, such as ferns, are adpated to survive in low sunlight.

Question 7.
In which physiological event, does the flowering of plants depend upon the span of daylight?
Answer:
In photoperiodism, flowering of plants depends upon the span of daylight.

Question 8.
Name some long day plants.
Answer:
Mustard, radish, tobacco etc. are long day plants.

Question 9.
Name some short day plants.
Answer:
Dahlia, cosmos, sugarcane, strawberry etc. are common short day plants.

Question 10.
Name some day neutral plants.
Answer:
Cucumber, tomato, cotton etc. are some day neutral plants.

Question 11.
Give an example of effect of humidity on plants.
Answer:
Increase in humidity reduces the rate of transpiration in plants.

Question 12.
Give an example of effect of temperature on plants.
Answer:
Reduction of temperature reduces the rate of flowering in certain plants such as tulip.

Question 13.
Give an example of effect of light on animals.
Answer:
Zooplanktons move towards the upper surface of the water bodies in presence of sunlight.

Question 14.
Give an example of effect of humidity on animals.
Answer:
In certain desert animals, like Moloch horridus, the skin possesses numerous hygroscopic spines to keep the body moist as much as possible.

Question 15.
Give an example of effect of temperature on animals.
Answer:
Due to extremely low temperature in polar regions, the size of polar bears are bigger compared to the bears of warmer region.

Question 16.
In which type of animals, very few sweat glands are found?
Answer:
In desert animals, number of sweat glands are very low.

Question 17.
In which geographical region, plants have less leaves and more spines?
Answer:
In desert, plants have less leaves and more spines.

Question 18.
In which region tall trees with needle-like leaves are found?
Answer:
Tall trees with needle-like leaves are seen in regions, where occasional snowfall occurs.

Question 19.
Name one component of population.
Answer:
Species is a component of population.

Question 20.
Name two factors that regulate population size.
Answer:
Natality and mortality are two factors that regulate population size.

Question 21.
Name two factors that increase population size.
Answer:
High natality and immigration increase population size.

Question 22.
Name two factors that decrease population size.
Answer:
High mortality and emigration decrease population size.

Question 23.
Members of which age group are predominant in a growing population?
Answer:
Members of lower age group are predominant in a growing population.

Question 24.
In a community, size of which trophic level increases with decrease in number of predators?
Answer:
In a community, size of primary consumer population increases with the decrease in number of predators.

Question 25.
Name one positive and one negative interspecific interaction.
Answer:
Commensalism is a positive and predation is a negative inter-specific interaction.

Question 26.
Give an example of symbiosis in the plant world.
Answer:
Lichen is an example of symbiosis in the plant world.

Question 27.
Name the inter-specific relation between orchid and mango tree.
Answer:
The inter-specific relation between orchid and mango tree is a type of commensalism.

Question 28.
Which type of symbiosis is noticed between Trychonympha and termites?
Answer:
Obligatory symbiosis is noticed between Trychonympha and termites.

Question 29.
Which type of relation is prevalent amongst various predators in a community?
Answer:
Various predators in a community carry on competition against each other.

Question 30.
What is hyperparasite?
Answer:
A parasite, that draws nutrition from another parasite, is called a hyperparasite.

Question 31.
What kind of interaction is competition?
Answer:
Competition is a negative-negative (- -) interaction.

Question 32.
What kind of interaction is predation?
Answer:
Predation is a positive-negative interaction.

Question 33.
Give two examples of positive-positive interaction.
Answer:
Examples of positive-positive interaction are mutualism and protocooperation.

Question 34.
What happens in commensalism?
Answer:
In commensalism, one individual is benefited and the other individual is neither benefited nor harmed.

Question 35.
Which is the ultimate source of energy in every ecosystem?
Answer:
Sun is the ultimate source of energy in every ecosystem.

Question 36.
Who acts as producer in any ecosystem?
Answer:
Green plants act as producer in any ecosystem.

Question 37.
Who acts as consumer in any ecosystem?
Answer:
All animals act as consumer in any ecosystem.

Question 38.
Who acts as decomposer in any ecosystem?
Answer:
Micro-organisms, such as bacteria, fungi etc. act as decomposer in any ecosystem.

Question 39.
Give two examples of phytoplanktons.
Answer:
Two examples of phytoplanktons are Chlamydomonas and Volvox.

Question 40.
Give two examples of zooplanktons.
Answer:
Two examples of zooplanktons are Cyclops and Daphnia.

Question 41.
Name two pelagic animals.
Answer:
Mosquito larvae and jellyfish are pelagic animals.

Question 42.
Give two examples of Necton.
Answer:
Fishes and whales are examples of Necton.

Question 43.
Give two examples of benthos.
Answer:
Corals and sea-anemones are examples of benthos.

Question 44.
What will happen if all the producers of any ecosystem are completely destroyed?
Answer:
If all the producers of an ecosystem are completely destroyed, the entire animal population of that ecosystem will be destroyed.

Question 45.
Name two plants that act as consumers.
Answer:
Dionaea sp. (venus flytrap) and Nepenthes sp. (pitcher plant) are two insectivorous plants that act as consumers. They feed on insects.

Question 46.
How much energy is transferred from one trophic level to the next in an ecosystem?
Answer:
10 % energy is transferred from one trophic level to the next in an ecosystem.

Question 47.
Who proposed the 10 % law of energy flow in an ecosystem?
Answer:
Famous scientist Lindeman, proposed the 10 % law of energy flow in an ecosystem.

Question 48.
Give an example of detritus food chain.
Answer:
Example of detritus food chain isEarthworm arrow Sparrow arrow Hawk.

Question 49.
Give an example of grazing food chain.
Answer:
Example of grazing food chain is-Grass arrow Grasshopper arrow Frog arrow Snake arrow Hawk.

Question 50.
Who are macro-consumers in any ecosystem?
Answer:
In an ecosystem, macro-consumers include all herbivores (cow, goat etc.) and all carnivores (cat, dog, tiger, lion etc).

Question 51.
Who are micro-consumers in any ecosystem?
Answer:
In an ecosystem, micro-consumers include all fungi and bacteria.

Question 52.
Give an example of terrestrial and aquatic ecosystem.
Answer:
Example of terrestrial ecosystem is forest ecosystem and example of aquatic ecosystem is pond ecosystem.

Question 53.
Name two nutrient cycle.
Answer:
Carbon cycle and oxygen cycle are two nutrient cycle.

Short Questions and Answers : (2 marks for each question)

Question 1.
What is meant by environment?
Answer:
All physical, living and non-living components surrounding the living organisms, which show direct or indirect impact on their behaviour, reproduction and life style, are collectively known as environment.

Question 2.
What is ecology?
Answer:
Ecology is the branch of science, dealing with study of interrelation amongst all physical, nonliving and living components of an environment.

Question 3.
What is ecosystem?
Answer:
Ecosystem is a functional unit of nature, where various living components interact with each other and with the non-living components, in a specific environment.

Question 4.
What is autecology?
Answer:
The branch of ecology dealing with the study of interrelation amongst different members of a single species (population) with each other and with the environment, is called autecology. Ecology of termites is an example of autecology.

Question 5.
What is synecology?
Answer:
The branch of ecology dealing with the study of interrelation amongst members of different species (community), residing in diverse environment, with each other and with the environment is called synecology. Ecology of a forest is an example of synecology.

Question 6.
Mention three environmental factors, which have direct impact on organisms at individual level.
Answer:
Light, relative humidity and temperature are three main environmental factors, which have direct impact on organisms at individual level.

Question 7.
What is photoperiodism?
Answer:
The physiological activity of various organisms depending upon the length of day or night is known as photoperiodism. For example, blooming and leaf abscission in plants and breeding and migration in animals, depend upon the relative length of light and dark periods.

Question 8.
What is meant by long day plant?
Answer:
The plants, that require longer span of day light for blooming, are called long day plants. Example-Mustard, Radish etc.

Question 9.
What is meant by short day plant?
Answer:
The plants, that require shorter span of day light for blooming, are called short day plants. Example-Rice, Cotton, Sugarcane, Dahlia etc.

Question 10.
Which physiological activities of plants are affected mainly by relative humidity?
Answer:
The rate of transpiration, water absorption and germination of seeds are some physiological activities of plants, which are directly affected by relative humidity.

Question 11.
How does environmental temperature affect biological activities of plants?
Answer:
Distribution of vegetation, rate of metabolism, blooming of flowers, transpiration etc. are various biological activities of plants, which are directly affected by environmental temperature.

Question 12.
Mention few examples of the impact of environmental temperature on animals.
Answer:

1. Sex ratio of rat flea and Daphnia are affected by temperature.
2. Hyla, the tree frog becomes darker in colour in higher temperature.
3. Body size of birds and mammals of cooler region becomes larger.
4. At higher temperature, metabolic rate becomes higher.

Question 13.
What is natality? Express natality by an equation.
Answer:
Natality: Natality or birth rate can be defined as, the ratio of total live births to total population in a specified community or area, over a specific period of time.

Expression: Natality is expressed as the number of live births per 1000 of the population per year. It is represented by the following equation -B = \(\frac{n d}{\mathrm{~N}}\) × 1000
where, B = birth rate or natality, N = total number of individuals in a population, nb = number of live births.

Question 14
What is mortality? Express mortality by an equation.
Answer:
Mortality: Mortality or death rate can be defined as, the ratio of total deaths to total population in a specified community or area, over a specific period of time.
Expression: Mortality is expressed as the number of deaths per 1000 of the population per year. It is represented as the following equation-
D = \(\frac{n d}{\mathrm{~N}}\) × 1000
where, D = Death rate or mortality, N = Total number of individuals in a population, nd = Number of deaths.

Question 15.
What is meant by absolute natality?
Answer:
The theoretical rate of increase of a population size in presence of all favourable factors and complete absence of any negative factor related to birth, is known as absolute natality.

Question 16.
What is meant by realized or ecological natality?
Answer:
The true rate of increase of a population size, in presence of all controlling factors (environmental pressure) acting on the birth of new members, is called realised or ecological natality.

Question 17.
Why is absolute natality higher than realized natality?
Answer:
In nature, different controlling factors restrict the reproductive process and increase foetal death. Therefore, the natality value never reaches that level as expected in ideal setup. That is why, absolute natality becomes higher than realized natality.

Question 18.
What is migration?
Answer:
Migration is the movement of animals or human beings, individually or in large group, from one place to another, temporarily or permanently, due to environmental or biological factors.

Question 19.
Why do animals migrate from one place to another?
Answer:
Animals migrate from one place to another due to seasonal food and water scarcity, temperature change, natural calamities like excessive rainfall or snowfall, population pressure and in search of good breeding place etc.

Question 20.
What is immigration? What is its impact on a population?
Answer:
Immigration: Immigration is the permanent inflow of a bulk of animals or human beings, from any other locality into a population.
Impact: Immigration increases the size of a population.

Question 21.
What is emigration? What is the impact of emigration on a population?
Answer:
Emigration: Emigration is the permanent exit of a bulk of animals or human beings of a population from their habitat to some other place.
Impact: Emigration reduces the size of a population.

Question 22.
What is meant by population density?
Answer:
Population density is the number of individuals of a population, residing in a unit area of their natural habitat. It can be expressed by the following equation -D = \(\frac{n d}{\mathrm{~N}}\),
where, D = Population density, N = No. of individuals of a population, A}= Area of the natural habitat.

Question 23.
What is population? What is population size?
Answer:
Population: Population is an aggregate of naturally interbreeding individuals inhabiting in same geographical area at a certain period of time.
Population size: Population size (usually denoted by N) is the number of individual organisms in a population.

Question 24.
What is carrying capacity?
Answer:
Carrying capacity of an ecosystem is the maximum population size of a given species that the environment can sustain indefinitely, by providing the necessary resources (food, water, habitat) available in the environment.

Question 25.
What is overpopulation?
Answer:
If the population size of a species exceeds the carrying capacity of the environment for that particular kind of species, then this unsustainable condition is known as overpopulation. Various factors like, increased natality, reduced mortality, increased rate of immigration or depletion of resources are responsible for overpopulation.

Question 26.
What is biotic community?
Answer:
Biotic community is a natural assemblage of a number of interacting populations that occupy the same geographical area, in a particular time.

Question 27.
Which types of interactions are commonly seen in a biotic community?
Answer:
Members of a biotic community are involved in various interactions. These are competition, predation, parasitism, cooperation etc.

Question 28.
What is meant by competition? Give example.
Answer:
Competition: Competition is a negative interaction amongst the members of same or different species in a population to obtain more of the limited natural resources (food, water, shelter) for survival.
Example: Lions compete for food with cheetah and hyena.

Question 29.
What is meant by predation? Give example.
Answer:
Predation: Predation is an inter-specific positive-negative interaction between prey and predators, where predator survives by feeding on the prey.
Example: Birds feed on insects. Snakes feed on rats and frogs.

Question 30.
What is meant by parasitism? Give example.
Answer:
Parasitism: Parasitism is a non-mutual, symbiotic, positive-negative interaction, where one organism is benefited at the expense of the other.
Example: Tapeworms (Taenia) draw nutrition from human (host) intestine. Dodder plants (Cuscuta) suck nutrients from phloem of the host plants.

Question 31.
What is meant by cooperation? Mention the types of cooperation.
Answer:
Cooperation: Cooperation is a positive interaction between two different species, where either both are benefited or one is benefited and the other remains unaffected.
Types: Cooperation is of three types

1. commensalism
2. mutualism
3. protocooperation.

Question 32.
What is meant by commensalism? Give example.
Answer:
Commensalism: Commensalism is a positiveneutral inter-specific interaction, where one member is benefited but the other remains unaffected.

Example: Orchids (epiphytes) grow on branches of mango tree, thereby getting safe shelter but the mango tree remains unaffected. Sucker fishes fix on the body of sharks and get food from discards of shark’s meal, but the shark remains unharmed.

Question 33.
What is symbiosis? Give example.
Answer:
Symbiosis: Symbiosis is an inter-specific cooperation in which two species live in a close physical association and both are benefited in some way or the other. This is also known as obligatory mutualism.
Example: Trichonympha receive shelter and nutrients in the intestine of termites and in return help in the digestion of cellulose of the wood fragments taken by the termites as food.

Rhizobium bacteria trap atmospheric nitrogen and supply it to leguminous plants, and in return they get shelter in the root nodules of those plants.

Question 34.
What is meant by mutualism? Give example.
Answer:
Mutualism: Mutualism is a positive-positive inter-specific interaction, where both members are benefited by one another, but close physical association is not evident.
Example: Insects collect nectar and pollens from flowers. In exchange, they help in spreading pollen grains from one flower to another, thereby helping in reproduction.

Question 35.
What is meant by protocooperation? Give example.
Answer:
Protocooperation: Protocooperation is a positive-positive inter-specific interaction, where both members are benefited but obligatory interdependence is not evident.
Example: Sea-anemone often rides on the shell of hermit crab. Here, sea-anemone intakes discarded food of hermit crab and in return protects it from predators by its stinging cells. This relation is not obligatory because both can survive independently.

Question 36.
How do different organisms remain organised in nature?
Answer:
In nature, all living organisms maintain a close interrelation among themselves and with the non-living components of the environment. This interrelationship helps to organize all the biotic components of nature.

Question 37.
How many types of ecosystem are there?
Ecosystem is normally of two types-
Natural ecosystem: The ecosystem that develops naturally in an environment. Example-Pond ecosystem.
Artificial ecosystem: The ecosystem which is artificially created by human beings. ExampleEcosystem in a crop field.

Question 38.
What is biome? What is biomass?
Answer:
Biome: Biome refers to a living community
characterized by distinctive plant and animal species and maintained under the climatic conditions of the largest geographical region.
Biomass: Biomass refers to the mass of various living organisms in a particular area or ecosystem, at a given time.

Question 39.
What is an ecological niche? What do you mean by planktons?
Answer:
Ecological niche: Ecological niche is defined as the role and the position of a particular species in its environment.
Planktons: Planktons are a diverse group of microscopic organisms which can float freely with the oceanic currents and in other water bodies. There are two types of planktonsphytoplanktons and zooplanktons.

Question 40.
What are phytoplanktons and zooplanktons?
Answer:
Phytoplanktons: The photosynthesising microscopic organisms drifting on the upper surface of water bodies, are known as phytoplanktons. Example- Diatoms, Cyanobacteria, Dinoflagellates etc.

Zooplanktons: The heterotrophic, microscopic organisms belonging to the animal community, that drift on the surface of water body, are called zooplanktons. Example-Jellyfish, Cyclops, Daphnia etc.

Question 41.
Who are called producers of an ecosystem? What are their functions?
Answer:
Producers: In an ecosystem, those organisms, which are capable of synthesizing their own food, are called producers. Green plants (autotrophs) play the role of producer in an ecosystem.

Function: Producers utilize the solar energy to synthesize their own food. They trap the energy from the sunlight and convert it into chemical energy within their body. The food, so produced, are utilized by other members of the ecosystem.

Question 42.
Who are called consumers of an ecosystem? Discuss their types.
Answer:
Consumers: In an ecosystem, the living organisms, who cannot prepare their own food and depend upon plants or other animals for their nutrition, are called consumers. Animals and human beings (heterotrophs) play the role of consumer in an ecosystem.

Types: Depending upon their food habits, consumers may be of various types-

1. Primary consumers: Directly depend on plants (producers) for food.
2. Secondary consumers: Feed on primary consumers.
3. Tertiary consumers: Feed on secondary consumers.

Question 43.
Who are the decomposers in an ecosystem? What is their role in ecosystem?
Answer:
Decomposers: In an ecosystem, the organisms which degrade the complex organic substances of dead bodies of producers and consumers and their organic wastes into simpler substances and obtain food from them are known as decomposers. Microorganisms, such as bacteria, fungus etc. play the role of decomposers in an ecosystem.

Role:

1. They help in decomposition of dead plant and animal remains and organic wastes, thereby preventing environmental pollution.
2. They convert large and complex organic matters into small and simple organic matters. As a result, continuous supply of organic elements on earth is maintained.

Question 44.
Who are the transformers of an ecosystem?
Answer:
The microorganisms, which break simple organic compounds and release inorganic elements from them, are known as transformers. Different denitrifying bacteria, sulphur bacteria, phosphobacteria belong to this group.

Question 45.
What is meant by flora and fauna?
Answer:
Flora: In an ecosystem, the entire plant community of a particular region is referred to as flora.
Fauna: In an ecosystem, the entire animal community of a particular region is referred to as fauna.

Question 46.
What is meant by nutrient cycle? What is its significance?
Answer:
Nutrient cycle: The cyclic process by which organic and inorganic matters of the environment are utilized by the living organisms and are again returned to the environment, thereby maintaining their balance, is known as nutrient cycle.

Significance:

• The constancy of nutrient elements within the environment is maintained.
• In this cycle, producers collect nutrients from the environment and these are returned by decomposers and transformers.

Question 47.
Nutrient cycle is a type of bio-geo-chemical cycle. Explain.
Answer:

• Different living organisms (plants, animals, microbes) participate in nutrient cycle. Therefore, it is a bio-cycle.
• Soil, rock, water etc. are various geographic elements that are included within nutrient cycle. Hence, it is a geo-cycle.
• The nutrient elements participate in various chemical reactions occurring within the body of the living organisms. Hence, it is a chemical cycle.
• Combining the above three conditions, it can be rightly said that the nutrient cycle is a type of bio-geo-chemical cycle.

Question 48.
What is energy flow in an ecosystem? Why it is unidirectional?
Answer:
Energy flow: In an ecosystem, the flow of energy along a food chain, starting from producer and gradually reaching the top level consumer through different trophic levels, is known as energy flow in an ecosystem.

Unidirectional flow: In any ecosystem, energy flow occurs through different trophic levels, starting from producer to consumer to decomposer. But this energy never comes back to the producer again. Due to this reason, energy flow in an ecosystem is unidirectional.

Question 49.
What is meant by trophic level? What is 10% law of energy flow?
Answer:
Trophic level: Trophic level refers to the position of a particular species in the ecological food chain. The organisms are classified on the basis of their feeding habits into four types –

• Producer
• Primary consumer
• Secon-dary consumer
• Tertiary consumer.

10 % law of energy flow: According to this law, each and every trophic level of a food chain in an ecosystem receives 10 % energy from its previous trophic level. This law was proposed by Lindeman.

Question 50.
What is food pyramid? What is energy pyramid?
Answer:
Food pyramid: Food pyramid is the graphical representation of different trophic levels in a food chain, starting from producer at the base, to the top level consumer at the peak.

Energy pyramid: Energy pyramid is the graphical representation of different trophic levels in a food chain, based on the total content of energy trapped in different levels from producer at the base to the consumers at the peak.

Question 51.
What is food chain? What is food web?
Answer:
Food chain: Food chain is a feeding hierarchy of different organisms in an ecological community in which organisms are linked to each other through the transfer of energy via food,

starting from producers or detritus and finishing at the top most level of consumers.

Food web: Food web is the network of several food chains, interconnected at different trophic levels, so as to develop a distribution system of energy via food amongst every member of the biotic community.

Question 52.
What is adaptation? Write two features of food chain.
Answer:
Adaptation: Adaptation is an evolutionary process by which an organism undergoes permanent anatomical or physiological or behavioral changes, in order to cope with the changing environment.

Features of food chain:

1. Energy flow occurs according to the sequential arrangement of various trophic levels in a food chain, i.e., producer arrow primary consumer arrow secondary consumer arrow tertiary consumer.

2. Different food chains in an ecosystem connect together to form a food web.

Question 53.
What is a grazing food chain?
Answer:
The food chian that starts from producers and proceeds through different consumers from lower to higher level, is known as grazing food chain.

Question 54.
What is parasitic food chain?
Answer:
The food chain that starts from producers (such as plants) and ends to any parasite, is called parasitic food chain.

Question 55.
What is detritus food chain?
Answer:
The food chain that starts from dead and decaying organic matters and ends to any large consumer, is called detritus food chain.

Question 56.
What is diurnal thermoperiodicity?
Answer:
Diurnal thermoperiodicity is response of organisms to daily changes of temperature. Example-Day time temperature is favourable for photosynthesis, transpiration, etc. and low temperature at night is suitable for storage of food, growth etc. Seed germination is influenced by diurnal changes of temperature.

Question 57.
What is seasonal thermodynamicity?
Answer:
Seasonal thermodynamicity is response of organisms to seasonal changes in temperature along with photoperiodicity. It controls flowering, fruiting, leaf fall, growing of new leaf etc. Example-Apple tree needs exposure to 7° C for more than 800 hours to set fruit. Wheat needs 10-25° C temperature in early winter for seed germination.

Question 58.
What do you mean by vital index?
Answer:
The percentage ratio of natality over mortality within a population in a given time, is known as vital Index. Vital index determines the normal growth of a population.

Vital Index (VI ) = \(\frac{\text { Natality }}{\text { Morality }}\) × 100

In case of growing population, V is >100
In case of negative growth, quad V is <100
In case of zero growth or stable population,
V is = 100.

Question 59.
Distinguish between producers and consumers.
Answer:

Features	Producers	Consumers
1. Source of food	Synthesise own food by photosynthesis	Depend directly or indirectly on producers for food
2. Ecological status	Belong to the first trophic level	Belong to any of the second to the top most trophic levels
3. Source of energy	Get energy directly from the sun	Get energy from the previous trophic level
4. Example	All green and other photosynthetic plants and microorganisms	All animais and nonchlorophyllous plants

Question 60.
Distinguish between producers and decomposers.
Answer:

Features	Producers	Decomposet
1. Source of food	Synthesise own food by photosynthesis	Draw nutrients from dead and decaying matters
2. Type of nutrition	Perform autotrophic nutrition	Perform saprophytic nutrition
3. Role in ecosystem	Synthesise complex organic compound (food matter) from simple inorganic matters	Break complex organic matters as free elements
4. Example	All green and other photosynthetic plants and microorganisms	Microbes, including decomposing bacteria and fungi

Question 61.
Distinguish between consumers and decomposers.
Answer:

Features	Consumers	Decomposers
1. Type of food	Complex organic matters from live organisms	Dead and decaying matters
2. Type of nutrition	Perform heterotrophic nutrition	Perform saprophytic nutrition
3. Role in ecosystem	Collect energy from producers and other consumers	Break complex organic matters as free elements
4. Example	All animals and non-chlorophyllous plants	Microbes, including decomposing bacteria and fungi

Question 62.
Distinguish between macro-consumers and micro-consumers.
Answer:

Features	Macro-consumer	Micro-consumer
1. Size	Larger and multicellular	Smaller and mostly unicellular
2. Type of nutrition	Autotrophic or heterotrophic	Saprophytic
3. Source of energy	Get energy indirectly from producers or other consumers	Get energy by breaking organic matters
4. Exampie	All animals and plants	Microbes, including decomposing bacteria and fungi

Question 63.
Distinguish between mutualism and commensalism.
Answer:

Features	Mutualism	Commensalism
1. Nature	Both the associates are benefited	One of the associates is neither benefited nor harmed
2. Contact	Close contact is maintained between two associates	Close contact between the associates is not mandatory
3. Example	Reiation between pollinating insects and flowers	Relation between epiphytic orchids and mango tree

Question 64.
Distinguish between intra-specific competition and inter-specific competition.
Answer:

Features	Intra-spesific competition	Inter-specific competition
1. Nature	Competition between members of the same species	Competition between members of different species
2. Causes of competition	To acquire food, shelter and sex partner	To acquire food and shelter
3. Predation	Predation rarely occurs	Predation is very common

Question 65.
Distinguish between food chain and food web.
Answer:

Features	food chain	Food web
1. Involvement	One species is involved in each trophic level	Many species are involved in each trophic level
2. Prey-predator relation	Specific	Diverse
3. Energy flow	Energy flows in a straight linear path	Energy flows in a complex reticular path

Question 66.
Distinguish between grazing food chain and detritus food chain.
Answer:

Features	Grazing food chain	Detritus food chain
1. Source of energy	Sun	Organic matters from dead and decaying substances
2. Flow of energy	Starts from producers and reaches the top most level of consumers via lower levels of consumers	Starts from detritus and reaches the top most level of consumers via detritivores and other lower consumers

Question 67.
Distinguish between population and community.
Answer:

Features	Population	Community
1. Definition	Maintain interbreeding relation	Maintain prey-predator or hostparasite or symbiotic relations
2. Relation type	Belong to a smaller level of ecological study	Belong to a larger level of ecological study
3. Span	Members are not interconnected in food chain or food web	Members are interconnected in food chain or food web
4. Interaction	Sum total of the members of a single species inhabiting in a specific region in a specific time	Sum total of the members of different interacting populations inhabiting in a specific region in a specific time

Question 68.
Distinguish between population and community.
Answer:

Features	Natality	Mortality
1. Nature	Indicates the rate of increase of a population due to birth	Indicates the rate of decrease of a population due to death
2. Effect on biomass	Biomass is directly proportional to natality	Biomass is inversely proportional to mortality
3. Effect on population	Population size increases due to natality	Population size decreases due to mortality

Long Questions and Answers : (5 marks for each question)

Question 1.
Briefly explain the impact of light on living organisms.
Answer:
Effect of light on living organisms :

1. In green plants, chloroplasts tend to concentrate on that surface of a leaf which gets more light.

2. In some plants, span of day light effects their flowering and other physiological activities. This phenomenon is known as photoperiodism. The plants, such as dahlia, sugarcane, strawberry etc., flowers bloom during shorter day light period and are called Short Day Plants (SDP). The plants, such as pea, radish, spinach etc., flowers bloom during longer day light period and are called Long Day Plants (LDP). In some plants, such as tomato, cucumber, cotton etc., span of day light does not have any significant impact on blooming. These are known as Day Neutral Plants (DNP).

3. Light enhances the pigmentation of skin. Animals living in hot and humid climate have darker body colour. Animals living in polar region have pale body colour. Similarly, human population living in strongly sunlit regions have darker body colour.

4. Photoperiod is the controlling factor for breeding features of different animals. The animals, such as sheep, goat, deer etc. breed during decreasing day length of autumn, known as Short Day Breeders (SDB). On the other hand, lemurs, horses, hamsters etc. breed during increasing day length of spring and are known as Long Day Breeders (LDB). Also, there are certain animals, whose breeding is not affected by day length. These animals, include guinea pig, cat, rabbit etc.

Question 2
Explain the effect of temperature on living world.
Answer:
Effect of temperature on living organisms

1. Plants growing in desert region have light-coloured body hairs, acting as heat reflectors. Their leaves are modified into spines and they have less stomata to reduce transpiration. The overall surface area of these plants are less, compared to other plants. As a result, area exposed to air is reduced, thereby reducing the rate of transpiration.

2. Plants growing in hot but humid climate of tropical region, have broad flat and thick green leaves to increase the rate of transpiration.

3. In amphibians, reptiles and fishes, body temperature varies with environmental temperature. These animals are therefore, known as poikilothermic animals. On the other hand, birds and mammals maintain constant body temperature in any environment. These are known as homeothermic animals.

4. Some animals, such as toads, house lizards, ants etc., can withstand wide range of temperature variation in the environment. These are called eurythermal animals. Some animals, such as fishes and cnidarians cannot tolerate wide temperature fluctuation. These are called stenothermal animals.

Question 3.
Explain the effect of relative humidity on living organisms.
Answer:
Effect of relative humidity on living organisms

1. Plants growing in arid climate develop features that help them to resist atmospheric dryness. They have elaborate root system, few leaves, less stomata, waxy leaf and stem surfaces, elaborate tap root system etc. to conserve and collect more water.

2. Plants growing in moist environment have wider leaves with many stomata to dispose excess water and these plants perform transpiration at higher rate. Certain plants like tomato, a few grasses dispose excess water as tiny droplets through special water pore, called hydathodes, situated along the edge of the leaves to get rid of excess water.

3. Animals living in desert regions have few sweat glands, discharge scanty urine and dry faeces. A desert reptile, Moloch horridus have uniquely designed spiny skin to reduce water loss and maintain body humidity. Insects living in desert region bear a layer of waxy cuticle over their body to reduce water loss.

4. Excessive relative humidity is favourable for the growth of fungal population. In moist weather, different pathogenic and non-pathogenic fungi grow. In moist weather, population of bryophytes and pteridophytes also increase significantly.

Question 4.
Explain the role of different factors regulating population size.
Answer:
Factors regulating population size
Four factors play significant role in regulating the population size. These are-

• natality
• mortality
• immigration
• emigration.

1. Natality: Natality can be defined as the ratio of total live births to a population in a specified community or area, over a specific period of time. We may express natality or birth rate as the number of live births per 1000 of the population per year. It can be represented as the following equation-

B = \(\frac{n d}{\mathrm{~N}}\) × 1000, text where,
B = natality or birth rate,
N = total number of individuals in a population,
nb = number of live births.

2. Mortality: Mortality can be defined as the ratio of total deaths to a population in a specified community or area, over a specific period of time. Population size decreases with the increase in mortality of the individuals.
Death rate or mortality is often expressed as the number of deaths per 1000 of the population per year. It can be represented as the following equation.

D = \(\frac{n d}{\mathrm{~N}}\) × 1000, where, D =text mortality or death rate,
N = total number of individuals in a population,
nd = number of deaths

3. Immigration: Immigration is the mass entry of individuals in a population in a given area, from some other place. Therefore, immigration increases the population size very quickly.

4. Emigration: Emigration, on the other hand, means the mass departure of individuals from a population in a given area, to some other place. By emigration, population size goes down abruptly.

5. iscuss different levels of positive inter-specific interactions in the living world.
Positive inter-specific interactions in living world Positive interactions in living world are collectively known as cooperation. In nature, several species live together with cooperation. Here, both or at least one of the species, involved in the relation is benefited, but neither of them is harmed. This cooperative relationship between different species help in better growth, reproduction and survival. Cooperation may be of different types-

• symbiosis
• mutualism
• protocooperation
• commensalism.

These are described below.
1. Symbiosis: Symbiosis is an inter-specific cooperation, in which two species live in a close physical association and both are benefited some way or the other. Symbiosis may be obligate (both the species entirely depend upon one another for survival) or facultative (both the species do not depend on their partner for survival).

Example-In lichens, algae and fungi develop symbiotic association. Here, the fungus acts as a settling platform and provides water and mineral to the alga. In return, the alga synthesises food for both.

2. Mutualism: Mutualism is the cooperation between two species, in which both are benefited but close physical association and nutritional interdependence between them is not evident.

Example-Insects collect nectar and pollen from flowers. In exchange, they help in spreading pollen grains from one place to another that help in plant reproduction.

3. Protocooperation: Protocooperation is a positive inter-specific interaction, where both members are benefited but, they do not depend on one another for survival. Growth and survival of both the species is possible even in the absence of this interaction.

Example-Sea-anemone often rides on the shell of hermit crab. Here sea-anemone intakes discarded food of the hermit crab and in return protects it from the predators by its stinging cells. This relation is not obligatory because both can live independently.

4. Commensalism: Commensalism is the cooperation between two species, where one of the members is benefited, but the other member is neither benefited nor harmed. In this relation, close association occurs between the two species, but nutritional interdependence is not developed.

Example-Epiphytic orchids grow on the branches of big trees, but carry out photosynthesis independently. By this process, orchids escape predation, but the host tree is neither harmed nor benefited.

Question 6.
Discuss about competition, predation and parasitism in the living world.
Answer:
Interactions in living world :
In living world, introspecific and inter-specific interactions involve two individuals, of which either both or one of the members is benefited and the other member sustains loss, get injured or die. Among these interactions competition, predation and parasitism are important. These are described below-
1. Competition: Competition can be defined as a negative interaction, where members of the same or other species fight with each other to acquire limited supply of environmental resources food, water, shelter and mates. Competition is mainly of two types-[A] intra-specific competition and [B] inter-specific competition.
Intra-specific competition: in this competition, members of the same species fight among themselves for food and mate.

Example-Fighting among dogs or fighting among cats.

Inter-specific competition: This competition takes place between members of two or more different species, for food and shelter.
Example-Sparrows quarrelling with common maina or dogs fighting with cats.

2. Predation: Predation is another type of inter-specific interaction, in which one species attacks another species to kill and consume it. Here, the attacker is known as predator and the one, which is attacked, is called the prey. The predator obtains nutrition and energy from the prey.
Example-Tigers kill deer, praying mantis kills other insects, pitcher plants trap insects etc. In all the above examples, the former ones are the predators and the latter ones are the prey,

3. Parasitism: Parasitism is the most advanced type of inter-specific interaction, in which one species depends upon other species for food or shelter or both. Here, the dependent member (parasite) is benefited, but the other member (host) is deprived.
Example-Tapeworms (Taenia), roundworms (Ascaris) etc. are the parasitic worms that draw nutrients from human (host). Dodder plants (Cuscuta sp.) suck nutrients from phloem of the host plants.

Question 7.
Write down a brief note on different types of parasites in living world.
Answer:
Different types of parasites
From evolutionary point of view, parasitism is the most advanced type of inter-specific interaction, in which one species depends upon other species for food or shelter or both. Here, the dependent member (parasite) is benefited, but the other member (host) is deprived. Different types of parasites are described below.

Based on their position in host body, parasites are classified into two types-
1. Ectoparasites: These parasites draw nutrients from outside the body of the host.
Example-Louse, ticks, bedbugs live on body surface of mammals, In case of parasitism in plants, Dodder plant needs a special mention. Dodder plant (Cuscuta sp.) produces root like structures, called haustoria, which penetrate the vascular bundle of the host and derive nutrition directly.

2. Endoparasites: These parasites live inside the body of the host and collect nutrients from them.
Example-Tapeworm, roundworm, Plasmodium (maiarial parasite), liver fluke etc. live inside human body.

On the basis of the dependance of parasitism, they may be of two types-

Obligatory parasites: These species completely depends upon a host to complete their life cycle. Example-Tapeworm, roundworm, Plasmodium etc. spend their life permanentiy as parasites.

Facultative parasites: These species can survive without the parasitic mode of life but can also adapt a parasitic life.
Example-The parasitic nematode Strongyloides stercoralis can also be free living.

Question 8.
Briefly describe the general structural aspects of an ecosystem.
Answer:
Structural aspect of ecosystem :
An ecosystem constitutes two types of components or factors – [1] abiotic factors and [2] biotic factors.
1. Abiotic factors: Abiotic factors include the non-living components of ecosystem. They have direct impact on life process of living organisms. Various abiotic component of the ecosystem areorganic component, inorganic component and physical component.

Organic component: Different organic matters, such as carbohydrate, protein, fat etc. are obtained from the dead and decaying organic remains of plants and animals. These organic matter mix with the soil and produce humus, which play a significant role in regulating soil fertility.

Inorganic component: It includes various mineral elements (such as calcium, magnesium, salts of sodium, potassium, sulphur etc.) and gases (such as oxygen, nitrogen, carbon dioxide etc.). Green plants use these elements for synthesizing their own food.

Physical component: The physical component of ecosystem includes various factors, such as light, temperature, humidity, altitude, steepness of slope, firmness of soil. Of these, the most important physical factor is light, more specifically sunlight. Green plants trap the solar energy and convert it to chemical energy to prepare their own food by the process of photosynthesis.

2. Biotic factors: The living organisms constitute the biotic factors of an ecosystem. Various components of biotic factors are- autotrophs and heterotrophs.
Autotrophs: All those organisms, capable of synthesizing their own food by photosynthesis or chemosynthesis, are known as autotrophs. All green plants, photosynthetic and chemosynthetic microorganisms are the examples of autotrophs.

Heterotrophs: The living organisms, which depend directly or indirectly on autotrophs for their nutrition are known as heterotrophs. Heterotrophs may be classified into three typesconsumers, decomposers and transformers.

1. Consumers: These organisms directly or indirectly consume autotrophs, especially green plants and plant products, to gain nutrition and energy. So, they are called consumers. Depending upon the nature of food they eat, consumers are classified into three types-

• Primary consumers: These animals directly consume green plants or plant products for nutrient and energy. Example-Deer, cow, grasshopper etc. (all herbivores).
• Secondary consumers: These animals directly consume herbivores for nutrition. Example-Frogs, small birds, rat, lizards etc.
• Tertiary consumers: These are larger consumers, which feed on both primary and secondary consumers. Example-Owl, tiger, lion, falcon, king cobra etc.

2. Decomposers and transformers: The organisms, which get their nutrients from dead organisms and decaying organic matter and in this process break the larger organic compounds into smaller molecules, are called decomposers. Different microorganisms (such as bacteria) and some fungi (such as Agaricus) belong to this group. Some bacteria act upon those small organic molecules, that are the end products of decomposition. These bacteria completely break those organic molecules and return the elementary components in nature. They are called transformers.

Question 9.
How does energy flow through an ecosystem?
Answer:
Energy flow in ecosystem :

Energy flow can be defined as the unidirectional transfer of solar energy, in the form of organic matters, from producers to the highest level of consumers, through different trophic levels via food chains. Sun is the ultimate source of energy in all ecosystems. Only photosynthetic organisms are capable of trapping and transforming the light energy form the sun into chemical energy in the form of food. This energy is transferred from producers to consumers through food chain, which is called flow of energy. Energy flow in an ecosystem occurs through the following three steps.

1. Acquiring energy: All green plants and other photosynthetic microorganisms can trap radiant energy from the sun. Only 0.02 % of the total energy of sun comes to the earth as light. Of this, only 0.1 % is trapped by means of photosynthesis. This process is called acquiring energy.

2. Utilizing energy: The light energy from the sun, trapped by the green plants, is oxidized during respiration to produce chemical energy. This energy is necessary to carry out different metabolic activities. This process is called utilization of energy.

3. Iransfer of energy: From the green plants, net primary production passes to different level of consumers through food chain. The herbivores or primary consumers directly get their share of energy from producers. By respiration, primary consumers utilize a greater portion of the transferred energy. the remaining portion of energy is then transferred to the higher level of consumers in the same way.

When energy flow occurs from one trophic level to another, subsequently an amount of energy is lost in the process which cannot be regained further. Moreover, the energy that follows from producer to consumer, can never be returned to the producer. Hence, the flow of energy is always unidirectional.

According to famous scientist, Lindeman, out of the total energy produced or received in a particular trophic level, only 10 % of it is transferred to the next trophic level. This is known as Lindeman 10 % law. As a result, very less amount of energy is received by the members of highest trophic level.

Question 10.
With an example, describe how biogeochemical cycle of a nutrient operates in nature.
Answer:
Biogeochemical cycle of a nutrient
Living organisms obtain different nutrients (such as C, H₂, O₂, N₂, S, P, Ca etc.) from the environment through food and as respiratory gases. These elements act as structural components of a living body. These elements
are the returned to the environment by excretion, respiration and decomposition of dead or decaying organic matters. Within biosphere, several structurally and metabolically important elements are exchanged between the biotic and the abiotic components of the ecosystem. This exchange of elements occurs through a cyclic path, known as nutrient cycle or biogeochemical cycle.
Here, the carbon cycle is discussed below as an example.

Carbon cycle refers to the cyclic exchange of carbon in the physical and biological systems.

• Reservoir Pool: Carbon bed of lithosphere act as reservoir pool for carbon.
• Cyclical Pool: The cyclic pool of carbon involves the atmosphere and the sea water.

3. Utilisation of carbon from nature: It involves two pathways-

Biological path: The biological path of carbon utilization involves activities of green plants and shelled molluscs. Green plants trap carbon within cellular compounds by photosynthesis. Shelled molluscs utilize carbon of CO₂ to prepare their shell. The echinoderms use CO₂ from air to form the spinous body surface with ossicles, which is made up of calcium carbonate.

Physiochemical path: The physiochemical path of carbon utilization involves certain marine deposits, such as limestone, dolomite, feldspar etc. absorb carbon (CO₂) to prepare calcium carbonate (CaCO₃).

4. Return of carbon to nature: Carbon is returned to the environment by two pathways-

Biological path: All living forms (except a few anaerobes) release CO₂ by respiration. CO₂ is released into the nature by decomposition of organic matters. After the death of molluscs and sea corals, their calcium carbonate rich shells are decomposed to produce CO₂.

Physiochemical path: Combustion of fossil fuel, wood etc., forest fire and volcanic eruption produce huge quantity of CO₂. This cyclic process of utilization and return of carbon to nature occurs at same rate. This helps to maintain constant carbon content in the environment.