Chapter 1 – Environment
Environment is the natural component in which biotic (living) and abiotic (non-living) factors interact among themselves and with each other.
• These interactions shape the habitat and ecosystem of an organism.
• In biological sense, environment constitutes the physical (nutrients, water, air) and biological factors (biomolecules, organisms) along with their chemical interactions (chemical cycles – carbon cycle, nitrogen cycle etc.) that affect an organism or a group of organisms.
• All organisms are dependent on the environment to carry out their natural life processes and to meet their physical requirements (food, energy, water, oxygen, shelter etc.).
• The biosphere is the biological component (supporting life) of earth which includes the lithosphere, hydrosphere and atmosphere.
• The biosphere includes all living organisms on earth, together with the dead organic matter produced by them.
• Biosphere is absent at extremes of the North and South poles, the highest mountains and the deepest oceans, since existing hostile conditions there do not support life (life is the characteristic feature of biosphere).
• Occasionally spores of fungi and bacteria do occur at great height beyond 8,000 metres, but they are metabolically inactive, and hence represent only dormant life.
• Habitat is the physical environment in which an organism lives (address of an organism).
• Many habitats make up the environment.
• A single habitat may be common for more than one organism which have similar requirements.
• For example, a single aquatic habitat may support a fish, frog, crab, phytoplankton and many others.
• The various species sharing a habitat thus have the same ‘address’. E.g. Forest, river etc.
Difference between Habitat and Environment
• A habitat always has life in it, whereas the environment does not necessarily have life in it.
• All habitats are environments, but all environments are not habitats. • A habitat is always a preference of one species.
• An environment could be a preference of many species that could eventually become many habitats.
• Usually, the environment governs the properties of a habitat, but not vice versa
An ecosystem can be visualised as a functional unit of nature, where living organisms (producers, consumers, and decomposers) interact among themselves and also with the surrounding physical environment.
• An ecosystem can be of any size but usually encompasses specific and limited species. E.g. Aquatic Ecosystem. (This is how ecosystem is different from Environment)
• In the ecosystem, biotic and abiotic components are linked together through nutrient cycles and energy flows.
• Everything that lives in an ecosystem is dependent on the other species and elements that are also part of that ecological community.
• If one part of an ecosystem is damaged or disappears, it has an impact on everything else.
Classification of Ecosystems
• Forest, grassland and desert are some examples of terrestrial ecosystems; pond, lake, wetland, river and estuary are some examples of aquatic ecosystems.
• Crop fields and an aquarium are human-made ecosystems.
Difference between Ecology, Environment & Ecosystem
• Ecology is the study of interactions between organisms, organisms and the surroundings occurring within an ecosystem or environment.
• An ecosystem is a functional unit of the environment (mostly biosphere). • An environment is a group of ecosystems.
Environment ➔ Can be almost everything or a small region.
Habitat ➔ Area where an organism lives.
Biosphere ➔ The region on earth that supports life.
Ecosystem ➔ Producers, Consumers, Decomposers and their relationships (tiny environment).
It is the functional unit of the environment.
Q. Which one of the following is the best description of the term “ecosystem”?
a) A community of organisms interacting with one another
b) That part of the Earth which is inhabited by living organisms
c) A community of organisms together with the environment in which they live.
d) The flora and fauna of a geographical area.
• A community of organisms interacting with one another – no specific term.
• That part of the Earth which is inhabited by living organisms ➔ biosphere.
• A community of organisms together with the environment in which they live ➔ ecosystem • The flora and fauna of a geographical area ➔ biodiversity.
- Majority of biochemical reactions take place in an aqueous medium.
- A few organisms can tolerate and thrive in a wide range of temperatures (they are called
- A vast majority of them are restricted to a narrow range of temperatures (stenothermal).
21% oxygen helps in the survival of many organ- isms; 78% nitrogen prevents spontaneous
- spontaneous combustion and 0.038% carbon dioxide helps primary producers in the synthesis of carbohy- drates.
- Proteins, carbohydrates, lipids etc. are essential for energy transfer in the living world.
- Carbon, carbon dioxide, water, sulphur, nitrates, phosphates, and ions of various metals are es- sential for organisms to survive.
- Vertical zonation of vegetation is caused due to altitude.
- Change in temperature with altitude is a limiting factor.
Buffering capacity of the earth
- A a neutral pH (pH of 7) is maintained in the soil and water bodies due to the buffering capac- ity of earth.
- The neutral pH is conducive for the survival and sustenance of living organisms.
- Some organisms are tolerant of a wide range of salinities (euryhaline).
- Others are restricted to a narrow range of salini- ties (stenohaline).
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