(a) Explain the following modes of… | Biology

Question 1 Report

(a) Explain the following modes of nutrition which occur in plants:
(i)Autotrophic
(ii) Chemosynthetic
(iii) Carnivorous

(b) Give one example each of a plant which undergoes the modes of nutrition listed in (a) above.

(c) (i) Describe three ways by which nitrogen is added to the soil for plant use.
(ii) State two ways by which nitrogen is lost from the soil.

Answer

(a) Modes of nutrition in plants

(i) Autotrophic nutrition - This is a mode of nutrition in which an organism manufactures its own organic food (such as glucose) from simple inorganic raw materials. In green plants this is done by photosynthesis, using carbon dioxide and water in the presence of sunlight and chlorophyll.
(ii) Chemosynthetic nutrition - This is a form of autotrophic nutrition in which an organism synthesises its own food from inorganic materials using energy obtained from chemical reactions (the oxidation of inorganic substances) rather than from sunlight.
(iii) Carnivorous (insectivorous) nutrition - This is a mode of nutrition in certain green plants that trap and digest small animals, especially insects, to obtain nitrogenous nutrients. Such plants photosynthesise but grow in nitrogen-poor soils, so they supplement their nitrogen supply by digesting the trapped animals.

(b) One example of a plant for each mode

(c)(i) Three ways nitrogen is added to the soil for plant use

Nitrogen fixation - free-living and symbiotic nitrogen-fixing bacteria (for example Rhizobium in the root nodules of legumes) convert atmospheric nitrogen into nitrogenous compounds.
Decomposition - decomposers (bacteria and fungi) break down dead plants, animals and their waste, releasing ammonium compounds which are nitrified to nitrates.
Lightning and rainfall - electrical discharge during thunderstorms combines atmospheric nitrogen and oxygen into oxides that dissolve in rain and reach the soil as nitrates (application of nitrogenous fertilisers and manure is another way).

(c)(ii) Two ways nitrogen is lost from the soil

Denitrification - denitrifying bacteria convert soil nitrates back into free nitrogen gas which escapes into the atmosphere.
Leaching - soluble nitrates are washed down beyond the reach of roots by percolating rain water (uptake by plants and removal at harvest, and loss by soil erosion, are others).

Answer Details

(a) Modes of nutrition in plants

(i) Autotrophic nutrition - This is a mode of nutrition in which an organism manufactures its own organic food (such as glucose) from simple inorganic raw materials. In green plants this is done by photosynthesis, using carbon dioxide and water in the presence of sunlight and chlorophyll.
(ii) Chemosynthetic nutrition - This is a form of autotrophic nutrition in which an organism synthesises its own food from inorganic materials using energy obtained from chemical reactions (the oxidation of inorganic substances) rather than from sunlight.
(iii) Carnivorous (insectivorous) nutrition - This is a mode of nutrition in certain green plants that trap and digest small animals, especially insects, to obtain nitrogenous nutrients. Such plants photosynthesise but grow in nitrogen-poor soils, so they supplement their nitrogen supply by digesting the trapped animals.

(b) One example of a plant for each mode

(c)(i) Three ways nitrogen is added to the soil for plant use

Nitrogen fixation - free-living and symbiotic nitrogen-fixing bacteria (for example Rhizobium in the root nodules of legumes) convert atmospheric nitrogen into nitrogenous compounds.
Decomposition - decomposers (bacteria and fungi) break down dead plants, animals and their waste, releasing ammonium compounds which are nitrified to nitrates.
Lightning and rainfall - electrical discharge during thunderstorms combines atmospheric nitrogen and oxygen into oxides that dissolve in rain and reach the soil as nitrates (application of nitrogenous fertilisers and manure is another way).

(c)(ii) Two ways nitrogen is lost from the soil

Denitrification - denitrifying bacteria convert soil nitrates back into free nitrogen gas which escapes into the atmosphere.
Leaching - soluble nitrates are washed down beyond the reach of roots by percolating rain water (uptake by plants and removal at harvest, and loss by soil erosion, are others).

(a) Explain the following modes of nutrition which occur in plants: (i)Autotrophic (ii) Chemosynthetic (iii) Carnivorous (b) Give one example each of a plan...