SEE Science (Ecosystem) Notes

                                               

               Ecosystem

1.  Define 'ecosystem'.

Ans: Ecosystem is defined as a delicate and dynamic balance which exists between the biotic and abiotic components.

2.  Which type of living being is the mushroom?

Ans: Mushroom is a decomposer in a community.

3.  Draw a labeled diagram of pyramid of biomass of an aquatic ecosystem.

Ans:

Fig: Pyramid of biomass of an aquatic ecosystem.

4.    Why the number of producer is larger than consumer in nature?

Ans: The producer is only the source of food energy for consumers. Producers are the only organisms which have ability to manufacture their own food by photosynthesis. Various types of consumers depend on producers directly or indirectly to obtain their food. Only 10% of the total energy is transferred from one trophic level to another. So, an ecosystem cannot run smoothly if the number of producers is less. Therefore, the number of producers is always more in an ecosystem.

5.    What is nitrogen fixation?

Ans: Nitrogen fixation is the process of conversion of free atmospheric nitrogen into the compound of nitrogen (i.e. nitrates) in soil.

6.    Farmers are suggested to cultivate leguminous plants at a certain intervals of years, why?

Ans: The roots of nodules of leguminous plants (like soya bean, pea, bean, etc.) contain nitrogen fixing bacteria like Rhizobium. Those bacteria convert atmospheric nitrogen into nitrates in the soil. From the soil nitrates are absorbed by the plant to make the pant protein.  So, leguminous plants play a great role to increase the fertility of soil by the process of biological nitrogen fixation. Therefore, farmers are suggested to cultivate leguminous plants at a certain intervals of years.

7.     What is Denitrification? Name the bacteria that help in this process.

Ans: Denitrification is the process of conversion of nitrate salts present in the soil into      free atmospheric nitrogen. It is carried out in the soil by free living bacteria called      Pseudomonas.

8.     It is beneficial for farmers when there occurs lightning in the months of Falgun and Chaitra, why?

Ans: During lightening in the sky, a huge temperature is produced in the atmosphere. This allows nitrogen to react with oxygen in the atmosphere to form oxides of nitrogen like nitric oxide, nitrogen dioxide, etc. These nitrogen oxides get dissolved in rain water forming very dilute solution of nitric acid and nitrous acid on coming to the earth with rain water. These acids react with alkalis and other salt to produce nitrate in the soil. The nitrate, so formed is absorbed by the plants for their growth and development. So, it is beneficial for farmers when there occurs lightning in the months of Falgun and Chaitra.

9.     Mention any two human activities that affect water cycle.

Ans: Any two human activities that affect water cycle are:

i) Deforestation

ii) Production and use of chlorofluorocarbons.

10.  Differences between

Nitrification	Denitrification
It is the process of conversion of ammonium salt into nitrites and nitrate.	It is the process of conversion of nitrates salt present in soil into free nitrogen gas.
It converts nitrogen into a usable form	It releases nitrogen in the atmosphere.

11.  Define bio-geochemical cycle and ecological pyramid.

Ans: Bio-geochemical cycle: The exchange of bio-chemicals between living and non-living       components of the bio-sphere is called bio- geochemical cycle.

        Ecological pyramid: The graphical presentation of number, biomass and accumulated     energy at different trophic level in a food cycle.

12.  In which cycle does carbon cycle belong?

Ans: Carbon cycle belongs to bio-geochemical cycle.

13.  Why green plants are called producers?

Ans:  Green plants are called producers because they are capable of synthesizing their own from inorganic compounds like carbondioxide and water in the presence of sunlight by the process of photosynthesis.

14.  Differences between nitrate and nitrite bacteria on the basis of their function.

Nitrate bacteria	Nitrite bacteria
They convert nitrites into nitrates in soil.	They convert ammonia into nitrites in soil.

15.  Write the name of an abiotic factor that plays a role in the ecosystem?

Ans: the name of an abiotic factor that plays a role in the ecosystem are:

a) Air              d) Heat            

b) Water        e) Temperature

c) Light           f) Soil

16.  Arrange the eagle, grass, snake, frog and insect in correct order to make a food chain of a grass land.

Ans: 

Grass

Insect

Frog

Snake

Eagle

17.  What is the role of mushroom in ecosystem?

Ans: The role of mushroom in ecosystem is:

a)     They help to decompose complex molecules into simpler inorganic molecules.

b)     They maintain the fertility of soil.

c)     They help in recycling of matter in nature.

18.  In the given diagram, a pyramid of biomass of an ecosystem is shown, name the ecosystem. What relation between producer and consumer, is shown in the given diagram?

Ans: It is the pyramid of biomass of an aquatic ecosystem.

19.  Name producer, primary consumer, secondary consumer and decomposer from the given lists.

Ans: Producer – Green plant

        Primary consumer – Pigeon

        Secondary consumer – Eagle

        Decomposer – Fungi

20.  Differences between

Aquatic ecosystem	Terrestrial ecosystem
It operates in water.	It operates on land.
In pond ecosystem, the biomass of producers is the smallest and that of tertiary consumers is the largest	In terrestrial ecosystem the biomass of tertiary consumer is the smallest and that of producer is the largest.