write a one page write up on any topic from 9th standard Biology- Chapter 14 - Natural Resources
Answers
Answer:
MARK IT AS BRAINLIEST
Explanation:
Water cycle
The whole process in which water evaporates and falls on the land as rain and water flows back into the sea via rivers is known as the water-cycle.
Main steps involved in water cyles are:
a. Evaporation: Water on earth changes to vapour due to sun’s heat and rises above.
b. Transpiration: Plants absorb water through the roots and then give off excess water in the form of vapor through pores in their leaves.
c. Respiration: It is a process in living organisms involving the production of energy, with the intake of oxygen and the release of carbon dioxide along with water vapour.
d. Precipitation: It is the process of condensation of water vapour in atmosphere into liduid which fall down in the form of rain, snow, sleet or hail.
e. Percolation and Absorption: Some of the precipitation soaks into the ground to reach the underground water, some on land gets absorbed by the plants, crops and trees to grow and the rest flows downhill as runoff to reach the seas to complete the whole water cycle.
2. Nitrogen cycle
The sequence in which nitrogen passes from the atmosphere to the soil and organisms, and then is eventually released back into the atmosphere, is called nitrogen cycle.
Nitrogen cycle involves the following processes:
a. Nitrogen Fixation
It is a process by which atmospheric nitrogen is converted into the form which can be easily absorbed the organisms on earth.
Nitrogen Fixation is carried out by the following ways:
By lightning: When lightning occurs, the high temperature and pressure convert nitrogen and water into nitrates and nitrites which get dissolved in water and are readily used by aquatic plants and animals.
By bacteria- Molecular nitrogen is converted into nitrates and nitrites by free living bacteria or the bacteria like Rhizobium present in the root nodules of legumes. Some bacteria convert the nitrogen gas (N2) to ammonia (NH3) which plants can use.
b. Nitrification: It is the process by which ammonia is converted into nitrites and nitrates.
c. Ammonification: It is the process by which soil bacteria decompose dead organic matter and release ammonia into soil.
d. Denitrification: It is the process by which nitrates are converted into atmospheric nitrogen back to complete the cycle.
3. Carbon cycle
The carbon cycle is the process by which carbon moves from the atmosphere into the Earth and its organisms and then back again.
Carbon cycle involves the following processes:
a. Photosynthesis: In this process plants form their food by absorbing the atmospheric carbon in the form of carbon dioxide gas and release oxygen gas.
Respiration: In this process plants and animals respire resulting in breakdown of glucose stored in the plants and animals to release CO2, water and energy.
Decomposition: In this process dead plants and animals get decomposed to release carbon into the environment.
Combustion: Burning of fossil fuels releases carbon dioxide gas into the environment as by product.
Movement of carbon from the atmosphere to the oceans: The oceans, and other water bodies, soak up about a quarter of the carbon dioxide to form carbonates.
Thus, the amount of carbon dioxide, so formed, is almost equal to the amount of carbon dioxide consumed & hence, its concentration in air remains same.
4. Oxygen cycle
The cyclic process by which oxygen element is circulated continuously through the living and non-living components of the biosphere constitutes oxygen cycle.
Oxygen cycle involves the following processes:
a. Respiration: All living organisms take in simple sugars (glucose) and oxygen and release carbon dioxide, water and energy.
b. Combustion: During the processes of combustion (or burning), oxygen reacts with carbon to form carbon dioxide gas.
c. Photosybthesis: Carbon dioxide gas from atmosphere is absorbed by green plants in the presence of sunlight to form carbohydrates and oxygen. Thus, oxygen is liberated in atmosphere.