Page No - 227
Give an example of a four step food chain operating in grassland. Name the secondary consumer in this food chain
Food chain in Grass Land
Grass --> Insect --> Frog --> Bird
The secondary consumer is frog
(a) Define trophic level. Draw the food chain with four trophic levels.
(b) What will happen if we kill all the organisms in one trophic level ?
(a) Trophic Levels – The various steps in a food chain at which the transfer of food takes place are called trophic levels. In a food chain, each step representing an organism forms a trophic level.
Grass --> Insect --> Frog --> Bird
(b) If we kill all the organisms in one trophic level, then the transfer of food (and energy) to the next trophic level will stop due to which the organisms of next trophic level will starve and die or migrate to other areas. The killing of all the organisms in one trophic level will also lead to the overpopulation of organisms in the previous trophic level. These effects will cause an imbalance in the ecosystem. For example, if we kill all the herbivorous animals like deer, rabbits, etc., in a forest, then the carnivorous animals like lions, tiger, etc., will not get food. Due to this, the lions and tigers etc., will starve and die or migrate from forest and go towards human settlements and attack people. Moreover, in the absence of herbivores like deer, rabbits, etc., the population of the previous trophic level ‘plants’ (or vegetation) will increase too much (because there are no deer or rabbits to eat them). All these effects will create an imbalance in the ecosystem.
What is the difference between the food habits of organisms belonging to the first and the third trophic levels ? Give one example each of the organisms belonging to these two trophic levels.
The organisms belonging to the first trophic level are producers which make their own food with the help of sun’s energy. For example – Green plants. The organisms of third trophic level are carnivores that feed upon herbivores. For example – Lion and Tiger.
Can the organisms of any trophic level be removed without causing any damage to the ecosystem ? Will the impact of removing all the organisms in a trophic level be different for different trophic levels ?
No. The impact of removing all the organisms of a trophic level will be different for different trophic levels.
Consider the food chain :
Grass → Deer → Lion
What will happen if all the lions are removed from the above food chain ?
If all the lions are removed, then there will be no predator control over the population of deer due to which its populations will greatly increase and deer will eat all grass. Over grazing will eliminate the grass and other green plants completely and turn the lush green forest into a desert area having no vegetation at all.
The number of malaria patients in a village increased tremendously when large number of frogs were exported from the village. What could be the cause for it ?
Frogs eat up mosquitoes. In the absence of frogs, the number of mosquitoes increase too much and spread malaria.
How does a biodegradable waste differ from a non-biodegradable waste ? Give two examples of non- biodegradable wastes which pollute our environment.
Which of the following are biodegradable and which non-biodegradable ?
Glass bottle, Paper, Ball point pen refill, Hay, DDT, Wheat, Cake, Wood,
Polythene bag, Jute bag, Cotton cloth, Grass, Vegetable peels
Glass bottle – Non-biodegradable Paper – Biodegradable Ball point pen refill – Non- biodegradable Hay – biodegradable DDT – Non- biodegradable Wheat – Biodegradable Cake – Biodegradable Wood – Biodegradable Polythene Bag – Non-biodegradable Jute Bag – Biodegradable Cotton Cloth – Biodegradable Grass – Biodegradable Vegetable peels – Biodegradable
(a) Describe an activity to show that while paper is biodegradable but plastic (say, polythene) is non-
(b) Explain why, some materials are biodegradable but some are non-biodegradable.
(a) We take a piece of paper and a plastic bag (Polythene Bag). Now dig the ground to about 15 centimeters depth and place the piece of paper and plastic bag in the dug up ground separately. After a month, we dig up the buried material and observe them. We will find that the piece of paper has been partially eaten up but the plastic bag has been remained unaffected. This means that the paper have been decomposed by the micro-organisms present in the soil. So paper is biodegradable. On the other hand, the plastic bag has not been decomposed by the micro ?organisms present in the soil, therefore It is non-biodegradable.
(b) It is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable and other are non- biodegradable.
Write down a food chain :Write down a food chain :
(a) in the sea
(b) which ends with humans
(c) with five links in it.
Plants -- > Grasshoper --> Frog --> Snake --> Hawk
At which trophic level a person is feeding when he is eating :At which trophic level a person is feeding when he is eating :
(a) roasted chicken
(a) Third trophic level
(b) Second trophic level
(c) Third trophic level
(d) Second trophic level
(e) Fourth trophic level
A student went to study a local pond. In one part of the pond she noticed tadpoles scraping at some pond weed. In another part she saw a water beetle holding a tadpole in its jaws.A student went to study a local pond. In one part of the pond she noticed tadpoles scraping at some pond weed. In another part she saw a water beetle holding a tadpole in its jaws.
(a) Construct a food chain for the pond.
(b) How many links are there in this chain ?
(a) Weed Tadpole Water beetle
Construct (a) a long food chain, and (b) a short foodchain, ending with man.
Algea -- > Protozoa -- > Small Fish --> Big Fish --> Man
(a) State one advantage of using jute bags over plastic bags for shopping.
(b) Write a common food chain of a pond ecosystem having four links.
(a) Jute bags should be used for shopping because these are biodegradable whereas plastic bags are non- biodegradable.
We do not clean ponds or lakes but an aquarium needs to be cleaned periodically. Why ?
Pond is a complete eco system having decomposer organisms which are the cleansing agents themselves. Aquarium is an incomplete ecosystem and does not have decomposer organisms for cleansing purposes.
What will be the consequence of the absence of decomposers in the ecosystem ?
In the absence of decomposers, the dead bodies of plants and animals would keep lying as such and the elements of plant and animal bodies would never be returned to their original pool like soil, air and water. The cycling process of life and death would be disrupted. The nutrient pool will not be replenished and would exhaust soon.
Give two differences between food chain and food web.
|Food Chain||Food Web|
|1. Food chain is a straight sequence of organisms|
2. Food chain do not have any cross linkages
|1. Food web is a complex network|
2. Food web has many cross linkage
Write one or two words for each of the following statements/definitions :Write one or two words for each of the following statements/definitions :
(a) Each level of food chain where transfer of energy takes place
(b) The physical factors like temperature, rainfall, light, soil, air and water of an ecosystem
(c) Organisms which depend on the producers for food either directly or indirectly
(d) The physical and biological world where we live in
(e) Selfcontained unit of living things and their non-living environment needing only sunlight for its functioning
(a) Trophic Level
(b) Abiotic components
(a) What is meant by biodegradable waste materials ? Give two examples of biodegradable wastes.
(b) Which of the following materials are non-biodegradable ?
Aluminium wire, Tea leaves, Synthetic fibre, Wool
(a) The waste materials which can be broken down to non- poisonous substances in nature in due course of time by the action of micro-organisms like certain bacteria are called biodegradable waste materials. Example ? Paper and wool.
(b) Aluminum wire and Synthetic fibre.
(a) What is meant by non-biodegradable waste materials ? Give two examples of non-biodegradable wastes.
(b) Which of the following materials are biodegradable ?Animal bones, Iron nails, Plastic mugs, Leather belts, Silver foil
(a) The waste materials which cannot be broken down into non-poisonous or harmless substances in nature are called non-biodegradable waste materials. Example – D.D.T and Plastics. (b) Animal Bones and Leather Belts.
Page No - 228
(a) Define an ecosystem. Give examples of any two ecosystems.
(b) List the biotic and abiotic components of an ecosystem.
(a) An eco system is a self contained unit of living things(plants, animals and decomposers), and their non living environment (soil, air and water). Example – a grassland and a forest.
(a) What is a food chain ? Give one example of a simple food chain.
(b) What is a ‘food web’ ? Show its formation.
(a) The sequence of living organisms in a community in which one organism consumes other organisms to transfer food energy is called a food chain. The simple food chain operating in grass land is:
Plants ---> Deer ---> Lion
b) The interconnected food chains operating in an ecosystem which establish a network of relationships between various species is called a food web.
In this food web, we can see a network of numerous pathways along which the food flows within grass land community. This food web starts from the plants which is producer and end in top carnivore hawk.
(a) What is meant by ‘environment’ ?
(b) What type of substances are the major pollutants of the environment ? Name two such substances.
(c) Name the organisms whose uncontrolled activities are damaging the environment.
(d) Explain why, it is better to use paper bags than plastic bags.
(a)The physical and biological world together is called environment.
(b) The non- biodegradable wastes pollutes the environment like plastic and polythene bags.
(c) Human beings are the only organisms which change the natural environment to fulfill their needs. The uncontrolled activities of human beings are damaging the balanced and healthy environment.
(d) Paper bags should be used for shopping because these are biodegradable whereas plastic bags are non- biodegradable.