Table of Contents
- 1 Environment
- 2 Habitat
- 3 Biosphere
- 4 Ecosystem
- 5 Components of an Ecosystem
- Environment is the natural component in which biotic (living) and abiotic (nonliving) factors interact with each other. These interactions shape the habitat and ecosystem of an organism.
- In biological sense, environment constitute the physical (nutrients, water, air etc.) 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 (birth to death) and to meet their physical requirements (food, energy, water, oxygen, shelter etc.).
- The environment is not static. Both biotic and abiotic factors are in a constant flux and keep changing continuously.
- Habitat is the physical environment in which an organism lives (it corresponds to address of an organism).
- It is an ecological or environmental area inhabited by particular species of plants, animals, fungi, etc. 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 other kinds of organisms.
- The various species sharing a habitat thus have the same ‘address’. Forest, river etc. are other examples of habitat.
- All habitats are environments but all environments are not habitats.
Difference between Habitat and Environment?
- A habitat always has life in it, whereas the environment does not necessarily have life in it.
- The habitat is a defined place or area of the environment according to the requirements of a particular life form. Therefore, a habitat is always an environment, but an environment is not always a habitat.
- A habitat is always a preference of one species, whereas 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.
- 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.
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- 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.
- 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.
- Ecosystem varies greatly in size from a small pond to a large forest or a sea.
- 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 may also be considered as man-made ecosystems.
- In the ecosystem, biotic and abiotic components are linked together through nutrient cycles and energy flows.
- An ecosystem can be of any size but usually encompasses specific and limited species. Eg: Aquatic Ecosystem. [This is how ecosystem is different from Environment]
- 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.
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Difference Between Ecology, Environment & Ecosystem
- Ecology is the study of the ecosystems and the environment.
- Environment is a group of ecosystems.
- Ecosystem is a functional unit of environment (mostly biosphere).
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.
Q0. Which one of the following is the best description of the term “ecosystem”?
- A community of organisms interacting with one another
- That part of the Earth which is inhabited by living organisms
- A community of organisms together with the environment in which they live.
- 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.
Components of an Ecosystem
- The components of the ecosystem are categorized into abiotic or non-living and biotic or living components. Both the components of ecosystem and environment are same.
- Abiotic components are the inorganic and non-living parts which act as major limiting factors.
- Lot of factors determine the survival of an organism. One single factor can limit the range of an organism. This single factor is called as a limiting factor.
- For example, seeds don’t germinate quickly in evergreen rain forests in spite of good rains and vegetation as the surface soil is heavily leached (nutrients washed away by running water). Here, poor soil is the limiting factor.
- Likewise, germinated saplings may not survive due to lack of light because of the dense canopy. Here, light [shade of the forest] is the limiting factor.
Q1. If a tropical rain forest is removed, it does not regenerate quickly as compared to a tropical deciduous forest. This is because [Prelims Question]
- the soil of rain forest is deficient in nutrients
- propagules of the trees in a rain forest have poor viability
- the rain forest species are slow-growing
- exotic species invade the fertile soil of rain forest.
- the soil of rain forest is deficient in nutrients: Rainforest = Rainfall through the year. It rains almost every day = The top soil is continuously washed away = nutrients are also washed away = leaching of nutrients = very little fertility remains in top soil = most of the seeds don’t germinate for years = regeneration is very slow (it takes decades). But the layer below top soil (sub-soil) is very fertile. So plants grow very quickly once their roots reach the sub-soil and if they receive enough sunlight.
- propagules of the trees in a rain forest have poor viability: Propagule = detachable structure that can give rise to a new plant, e.g. a bud, sucker, or spore [Asexual Reproduction in plants]. Seed bearing plants are more significant than Propagules in rainforest. So propagules don’t really matter.
- the rain forest species are slow-growing: The plant species in rainforests compete for sunlight. So they grow as rapidly as they can.
- exotic species invade the fertile soil of rain forest: this statement is wrong as the rainforest soil is heavily leached. Hence they are not fertile. But exotic invasive species are a threat to rain forests (E.g. Most plantation crops like rubber, palm etc.).
- Light: The spectral quality of solar radiation is important for life. The UV component of the spectrum is harmful to many organisms.
- Rainfall: Majority of biochemical reactions take place in an aqueous medium. These biochemical reactions are important for survival of an organism. So rainfall is an important limiting factor.
- Temperature: Latitudinal insolation decides the temperature range of a region. A few organisms can tolerate and thrive in a wide range of temperatures (they are called eurythermal), but, a vast majority of them are restricted to a narrow range of temperatures (such organisms are called stenothermal).
- Atmosphere: 21% oxygen helps in survival of many organisms, 78% nitrogen prevents spontaneous combustion and 0.038% carbon dioxide helps primary producers in the synthesis of carbohydrates.
- Organic compounds: Proteins, carbohydrates, lipids etc. are essential for energy transfer in the living world.
- Inorganic compound: Carbon, carbon dioxide, water, sulphur, nitrates, phosphates, and ions of various metals are essential for organisms to survive.
- Altitude: Vertical zonation of vegetation is caused due to altitude. Change in temperature with altitude is the limiting factor.
- Buffering capacity of earth: The most unique feature of the earth is its buffering action due to which a neutral pH (pH- 7) is maintained in the soil and water bodies. The neutral pH is conducive for the survival and sustenance of living organisms.
- Salinity: Some organisms are tolerant of a wide range of salinities (euryhaline) but others are restricted to a narrow range (stenohaline). So salinity is a limiting factor.
Effect Of Abiotic Components On Terrestrial Primary Producers – Plants
- Plants are the reason that the other animals are able to survive on land. So the effect of abiotic factors on plants is crucial.
- Extremely high intensity favors root growth than shoot growth which results in increased transpiration, short stem, smaller thicker leaves.
- On the other hand low intensity of light retards growth, flowering and fruiting.
- When the Intensity of light is less than the minimum, the plants ceases to grow due to accumulation of CO2 and finally dies.
- Out of 7 colours in the visible part of spectrum, only red and blue are effective in photosynthesis.
- Plant grown in blue light are small, red light results in elongation of cells results in etiolated plants. Plants grown in ultraviolet and violet light are dwarf.
- Frost results in freezing the soil moisture. The plants growing in such soil, get exposed to direct sun light in the morning, they are killed due to increased transpiration when their roots are unable to supply moisture. This is the main reason for innumerable death of sal seedlings.
- As a result of frost, water in the intercellular spaces of the plant gets frozen into ice which withdraws water from the interior of the cells. This results in increasing concentration of salts and dehydration of cells. Thus coagulation and precipitation of the cell colloid results in death of plant. Also, frost leads to formation of canker.
- Snow acts as blanket, prevents further drop in temperature and protects seedlings from excessive cold and frost.
- Accumulation of snow on tree parts can break the branches or even uproot the tree.
- Snow shortens the period of vegetative growth.
- High temperature results in death of plant due to coagulation of protoplasmic proteins [Some bacteria can survive high temperatures because of their protoplasmic proteins that don’t coagulate at normally high temperatures].
- High temperature disturbs the balance between respiration and photo synthesis thereby causes depletion of food resulting in greater susceptibility to fungal and bacterial attack.
- It also results in desiccation of plant tissues and depletion of moisture.
Primary producers – Autotrophs (self-nourishing)
- Primary producers are basically green plants, certain bacteria and algae that carry out photosynthesis.
- In terrestrial ecosystem, grasses, plants and trees are the primary producers while in aquatic ecosystem, microscopic algae [plankton] are the primary producers.
Consumers — Heterotrophs or Phagotrophs (other nourishing)
- Consumers are incapable of producing their own food. They depend on organic food derived from plants, animals or both.
- Consumers can be divided into two broad groups namely micro and macro consumers.
- Herbivores are primary consumers which feed mainly on plants e.g. cow.
- Secondary consumers feed on primary consumers e.g. wolves, dogs, etc.
- Carnivores which feed on both primary and secondary consumers are called tertiary consumers e.g. lion which can eat wolves, snakes etc.
- Omnivores are organisms which consume both plants and animals e.g. man, bear, etc.
Micro consumers – Saprotrophs (decomposers or osmotrophs)
- They are bacteria and fungi which obtain energy and nutrients from dead organic substances (detritus) of plant and animals.
- The products of decomposition such as inorganic nutrients which are released in the ecosystem are reused by producers and thus recycled.
- Earthworm and certain soil organisms (such as nematodes, and arthropods) are detritus feeders and help in the decomposition of organic matter and are called detrivores.
Classification of Ecosystems