our environment

environment

environment

the physical and biological world in which we live in is called the environment. it includes our physical surroundings like air, water, soil and organisms such as plants and animals and microorganisms like bacteria and fungi

all of these components are dependant on one another. they interact with one another and maintain a balance in the environment

biodegradable and non-biodegradable wastes

those wastes which can be broken down to non-poisonous substances in nature in due course of time by the action of microorganisms (decomposers) are called biodegradable wastes. they do not pollute the environment (only do when their amount is too large to be degraded)

those wastes which cannot be broken down into non-poisonous substances in nature are called non-biodegradable wastes. they are major pollutants of the environment. examples; DDT, plastics etc.

why some materials are biodegradable while others are not

the microorganisms present in the environment can only break down natural materials but cannot break down man-made materials like plastic. so it is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable while others are non-biodegradable

ecosystem

an ecosystem is a unit of living things (plants, animals, decomposers) and their non-living environment (soil, air, water)

examples: grassland, forest, desert (natural) ; gardens, parks, aquariums (artificial)

components of an ecosystem

every ecosystem has two main components;

abiotic components: include the physical environment like soil & water, the inorganic substances like CO2 & H2O, and the climatic factors like light & temperature

biotic components: include the organisms; i.e,, producer (autotrophs), consumer (heterotrophs), decomposer (saprotrophs)

the functioning of an ecosystem

from the earth, carbon dioxide and water are absorbed from the producer organisms. with the help of sunlight energy, the producers convert these inorganic materials to organic compounds like carbs which act as food. the consumers derive their energy needs from producers. when consumers and producers die, the decomposers act on their dead bodies to return various elements back to the earth, creating a cycle.

producers

producers are the organisms which can prepare their own food from simple inorganic materials like CO2 and H2o by using sunlight energy in the presence of chlorophyll

examples: green plants, blue-green algae

consumers

those organisms which consume food prepared by producers are called consumers

if an animal eats green plants then we say it gets the food from producers directly. if an animal eats the meat of an animal which eats green plants then we say it gets the food from producers indirectly

examples: all animals, protozoa

planktons

planktons are microscopic organisms which freely float on the surface of water in a pond, lake or ocean. they are of two types;

phytoplanktons: microscopic aquatic plants (algae)

zooplanktons: microscopic aquatic animals (protozoa)

decomposers

the microorganisms which break down complex organic compounds present in dead organisms into simpler substances are called decomposers

the bacteria which act as decomposers are called putrefying bacteria. the secretion of their body break down organic material into simpler substances like CO2, NH3. they use some of it for their own maintenance and release the remaining into the environment

importance of decomposers

decomposers help in decomposing dead bodies and hence act as cleaning agents of environment. the various elements which were taken by plants from the soil, air and water and returned back to them after their death due to the action of decomposers

if decomposers didnt exist, then the cyclic process of life and death would be disrupted

food chains

the sequence of living organisms in which one organism consumes another organism to transfer food energy, is called a food chain

it represents a single directional transfer of energy

the study of food chains helps us in knowing various interactions among difference organisms and their interdependence

example: Grass → Deer → Lion

food web

the interconnected food chains in an ecosystem which establish a network of relationships between organisms is called a food web

it is the network of a large number of food chains in an ecosystem

the members of higher tropic levels feed on many different organisms of the lower tropic levels, unlike food chains

removal of one group of organisms does not disturb the whole chain

trophic levels

the various steps in a food chain at which the transfer of energy takes place are called trophic levels

the producers constitute the first trophic level

the herbivores constitute the second trophic level

the smaller carnivores constitute the third trophic level

the large carnivores constitute the fourth trophic level

effect of human activities on the ecosystem

the shortening of food chains due to human activities like hunting leads to an imbalance in the ecosystem

for example: the formation of the sahara desert is due to the large scale killing of tigers

what happens if all lions are removed

if lions are removed, the population of deers increases greatly. this will lead to an excessive grazing of grass due to which grass can be eliminated

what happens if all deers are removed

if all deers are removed, then there would not be sufficient food for the lions resulting in them leaving the forest and eating animals out of their food chain and disturbing the entire ecosystem

what happens if all the producers are removed

if all producers are removed, then there is no food for any other organisms

transfer of energy in food chains

the food chains actually represent a stepwise transfer of energy between trophic levels. the flow of energy is as follows;

first step: sunlight energy trapped by green plants

second step: herbivores consume the green plants and release unused energy as heat (community heat)

third step: carnivores consume the herbivores and release community heat

characteristics of transfer of energy

energy is not created in the ecosystem. it is only converted from one form to another

there is a continuous transfer of energy from one trophic level of organisms to the next trophic level in the food chain

there is a loss of energy at each energy transfer in various trophic levels which goes into the environment and remains unutilized (the energy is lost as heat energy)

ten percent law

according to the 10% law, only 10% of the energy entering a particular trophic level is available for transfer to the next trophic level. in simple words, the energy available at each trophic level is 10% of the previous level

[note: plants only absorb 1% of the sunlight energy coming from the sun]

why the number of trophic levels in a food chain is limited

food chains generally consist of three our four steps because after that the energy available for the next organism is negligible and is not sufficient for it to sustain its life

biological magnification

the increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification. this is due to the fact that they are non-biodegradable

it is the most harmful for organisms at higher trophic levels

ozone layer formation

ozone is a poisonous gas which is formed high up in the atmosphere by the action of UV rays on the oxygen molecules. it is as follows;

O2 →(uv rays) O + O

these oxygen atoms are very reactive and combine with the oxygen molecules to form ozone, O3

O2 + O → O3

depletion of ozone layer

the ozone layer is very important for life on earth as it absorbs the harmful UV rays (they cause skin cancer, damage eyes and immune system) and prevents it from reaching the earth

the depletion of ozone is due to the use of CFCs (chlorofluorocarbons), which are used in refrigerators and ACs as coolants. they react with ozone and destroy it gradually

in 1987, UNEP forged an agreement with its members to freeze CFC production

modes of waste disposal

recycling

preparation of compost

incineration (reducing waste to ashes)

landfill