UNIT 3: Ecosystem

Ecosystem

Q. What do you mean by ecosystem?

Ans : The interaction created by the inter-relationship between the biotic and abiotic factors in the environment is called an ecosystem.

Q. What are the biotic and abiotic factors?

Ans: All the living beings living in an ecosystem are called the biotic elements. Carbon, nitrogen, carbon, dioxide, water, carbohydrates, proteins, lipids, nucleic acid, climate, light, temperature, air etc. are abiotic factors.

Q : What is Food chain? What are its types?

Ans: The process of eating and being eaten among animals in any trophic structure helps the food energy to flow in a disciplined manner. This is called food chain. Food chains are of two types —

(a)  Grassland food chain

(b)  Detritus food chain

Q.4 : What do you mean by Food web for Food cycle?

Ans: The food-related relationship among different beings in a biotic community is called food web or food cycle.

Q.5 : How is the energy flow directed?

Ans : Heat energy is directed by the two laws of thermo-dynamiss. The first law is that- energy can neither fee created nor be destroyed; it can only be transformed from one state₄to another. The second law states that during transformation, some amount of energy is lost.

Q.6 : Who propagated the concept of ecological pyramid?

Ans : An English scientist named Charles Elton.

Q.7 : What are the main ecosystems?

Ans : There are three types of ecosystems in the environment—

(i) Terrestrial ecosystem    (ii) Freshwater ecosystem, and   (iii) Marine ecosystem.

Q.8 : What are the main characteristics of the rainforests?

Ans : Its temperature is high (23°-27°C)

(i) Every year, there is 200-1000 cm rainfall.             

(ii) Warm and moist climate           

(iii) Contains sufficient amount of mineral and humus

(iv) The height of plants differs according to species. Some trees grow upto 30-40 metres in height

(v) Trees which can grow under the shadow of these big trees are bamboo, ferns and shrubs etc.

Q.9 : Where in India can you find desert ecosystem?
Ans : India's Thar desert.                                    

Q.10 : Write the names of some plants and animals found in the pond ecosystem.

Ans : Spyrogyra, Eugonium, Zygnema Azola, Wolpaia, Salvinia, Pigtia Lemona, Echomia, Cerataphylum, Articularia, Hydrilla, Vallisnaria, Nelumb, Typha, Saggitaria, Frogomytes, CioJiates and Flagellate protozoa, Rotifers, Daphnia, Cyclops, haylly, dragonfly, damal fly, water boatman, beetles, water insects, fish, frogs, turtles, snakes etc. and those that live in the depths like hydra; prawns, crabs, different varieties of snails.

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1.  Name two types of habitats on our planet.

Ans : Terrestrial and Aquatic habitat.

2.  What is biosphere?

Ans: The zone consisting of land, water and air where life exists is called alnosphere.

3.    What is the percentage of hydrosphere on the earth surface?

Ans : Hydrosphere covers about 73% area of the earth surface.

4.  What is the meaning of litho?

Ans : The meaning of litho is stony.

5.  What is stratopause?

Ans : The upper layer of the stratosphere is known as stratopause.

6.    What is the importance of the troposphere?

Ans : Troposphere is the most important zone of the atmosphere. Cloud formation, thundering, lightning etc. take place in this zone.

7. Define ecology.

Ans : An aspect of biology that deals with the interrelationship between biotic and abiotic components as well as the relationships among the individuals of the biotic component is called ecology.

8. What is population ecology and genecology?
Ans : Study of population and their interactions is termed

as population ecology while the study of population of a single'j species is called genecology.

9. Into how many types can ecology be divided? Name them.

Ans : Ecology can be divided into two types. They are : (i)   Autecology, (ii) Synecology.

10. Define ecological niche.

Ans: An ecological niche is the unique complex of factors which characterizes the environment of any given population,

11. What is the full form of IBP?

Ans : The International Biological Programme.

12. Define ecosystem?

Ans : Any unit in which there is interaction between ' organisms and their physico-chemical environment and between! organisms and materials is called an ecosystem.

13. What is terrestrial and aquatic ecosystems.
Ans ; The desert, grassland, forest, crop-fields and mountains represent terrestrial ecosystem, whereas ponds, lakes, rivers, seas and aquarium represent aquatic ecosystems.

14. What are terrestrial and aquatic ecosystems'.
Ans : The desert, grassland, forest, crop-fields and mountains represent terrestrial ecosystems, whereas ponds,
lakes, rivers, seas and aquarium represent aquatic ecosystems
15. Give examples of some man-made ecosystems.

Ans : Crop-fields, gardens, aquarium etc.

16.   What is phytoplankton?
Ans: The Autotrophs iadeep water are microscopic floating plants called phyto-plankton.

17.   Define food chain.

Ans : The sequence of eating and being eaten in an ecosystem is known as food chain. !

18.   What are the components of an environment?
Ans : The environment consists of non-living or abiotic components and a living biological community or biotic components.

19.   What is the meaning of 'biosphere'?

Ans : The entire inhabited part of the earth and its atmosphere including the living and the non-living components form the biosphere.

20.     What are the primary constituents of the biosphere?

Ans : The primary constituents of the biosphere are : (i)  The Hydrosphere (ii) The Lithosphere   (iii) The Atmosphere.

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1. What is an ecosystem?

Ans : An ecosystem is a group of biotic communities of species intereaeting with one another and with their non-living environment exchanging energy and mater. Now, ecology is often defined as the studty of ecosysytem.

The following conditions are essential for healthy ecosystem-

·      Space for growthe and movement.       

·      Pure air for breathing.                          

·      Sufficient supply of Water.

·      Availability of inorganic substances.

·      Adequate distribution of energy for biological activities.    

Q. Give an account of the biotic and abiotic components of biosphere.

Ans : Biosphere has two main components :

(i) Abiotic Components : The abiotic components of the biosphere are water, gases and mineral elements. The factors like sunlight, temper n food from simple inorganic substances like carbon dioxide and water, in the presence of light

(ii) Biotic Components :

Consumers: The organisms which consume food prepared by the producers are called consumers.                          

Decomposers : The micro-organisms which break down the complex organic compounds of the dead remains of plants and animals and their products like faeces, urine etc. into simpler substances are called decomposers.                                      

Q:  Explain the relationship amongst the producers, consumers and the decomposers.

Ans : The relationship amongst the producers, consumers and the decomposers is as follows :

The producers are the green plants which trap solar energy and convert it to potential energy. All the consumers like animal and non-green plants directly or indirectly depend upon the plants for energy and the decomposers are non-green microbes which break down the complex organic compounds of the dead remains of plant and animals and their products-like faeces, urine etc. into simpler substances. 4. Distinguish between:

(a)    Phagotrophs and Saprotrophs:  The organisms which consume other organisms are known as phagotrophs and the micro-organisms which feed on dead organic matters are known as saprotrophs.

(b)    Autotrophs and Heterotrophs: The organisms which can prepare their own food from simple inorganic substances like carbon dioxide and water, in the presence of light are known as autotrophs. For e.g. -Green plants.

All the consumers which are dependent on autotrophs for their food are known as heterotrophs. For e.g. - Lion, tiger, etc.

(c)    Herbivore and Carnivore: The organisms which derive their food directly from plants or producers are called herbivores. For e.g. cow, buffalo, goat, deer etc. They are also known as primary consumers or first order consumers.

The organisms which feed on herbivores are called secondary consumers or second order consumers or carnivores. For e.g. lion, tiger, snake, hawks and frog etc.

(d)     Micro-consumers and Macroconsumers: The micro-consumers are also called the saprobes or saprophytes. They constitute a sort of heterotrophic organisms that break down the complex compounds of dead protoplasm, absorb some of the decomposition products, and release simple substance for utilising by the producers. For eg. - Bacteria and fungi.

Macro-consumers are also known, as phagotrophs. They constitute a sort of heterotrophic organisms, chiefly animals that ingest other organisms or particulate organic matter. For e.g. — lion, tiger etc.

Write short notes on:

(a)     Homeostasis: The ecosystem, by itself, tries to resist the change and maintain itself in equilibrium with the environment owing to a property which is known as homeostasis. Homeostasis is the inherent property of all living systems to resist change. It is capable of self-maintenance and self-regulation.

(b)    Biomes: The natural ecological groupings of plants and animals made on the basis of climates are called biomes. The existence of plants and animals in an area is determined by the climatic conditions of the area. Same type of plants and animals appear together in similar climatic zones. Biomes may also be termed
as major ecosystems of the earth. The major biomes of the world are Tundra, Northern Conifer forest or Taiga, Temperate deciduous forest, Tropical rain forest, Chaparral, Tropical Savannah, Grassland, Desert.                                          

(c)     Food chain: A food chain is simply a series of different kinds of organisms through which food energy flows in an ecosystem. All the food chains begin-with a producer i.e. green plants) which is the origin of all food. There is a sequence in which one organism eats up the other organism for survival. For example, in grassland ecosystem the grass is eaten up by animals like deer and the deer in turn is consumed by a lion.

One of the examples of food chain is :

Grass--->     Insects--->       Frog--->        Snakes --->         Hawk

(Producer) (Herbivore)       (Carnivore)      (Large Carnivore)    (Top Carnivore)

(d)    Food web: The linear arrangement of producers and consumers in an ecosystem does not reflect the interrelationship amongst the various organisms of an ecosystem. In fact, many animals may act as consumers of first, second or third order. The interconnected food - chains operating in an ecosystem which establish a network of relationships between various species, is called food web.

(e)    Trophic level: The producer-consumer arrangement in an ecosystem is one kind of structure called trophic structure and each food level is known as trophic level. The amount of living materials in the different trophic levels or in a component population is known as the standing crop, irrespective of plants and animals.

Different trophic levels of an ecosystem are:

a.     The plants are producers and constitute the first trophic level

b.     Herbivores which fed upon the plants constitute the second trophic level.

c.     Carnivores which feed upon the herbivores are called the third trophic level.

d.     Large carnivores or top carnivores that feed upon the small carnivores constitute the fourth trophic level.

Q: Write the causes of ecological succession and its basic types.

Ans: A progressive organization of a biological community as a new plants and animals species come into an area and alter the environmental conditions is called ecological succession. Ecological succession is of two types. These are as follows:

(i) Primary succession: When plants and animals colonize a previously desolate area then primary succession takes places such as sand dune, new volcanic island, bare rock, or recently glaciated ground. Everything including the soil bacteria, insects plants, and animals must come from nearby habitats in these situations.

(ii) Secondary Succession: In areas where communities have become established before an event then secondary succession occurs, such as fire, landslide, flood, hurricane field-clearing disturbs them.

Q: Write about the biotic components in the earth.

Ans: Producers, consumers and decomposer are the three biotic component in the earth.

(i) Producer: Producer means the green plants and certain photosynthetic or chemosynthetic bacteria which produce food for all other organism. These can convert the light energy of sun into potential chemical energy in the form of organic compounds, needed plants for their own growth and; development.

(ii) Consumers: Consumers refer to those organisms which get their organic food from other organism and they are directly or indirectly depend upon the producer organisms. Consumers consume the materials built up by the producers. There are three type of consumer. These are primary, secondary and tertiary consumers.

·         Primary consumers feed on tree leaves. Ant, flies, beetles, bugs, spiders, elephants, deer, squirrel, mongoose etc are primary consumers.

·         Secondary consumers feed on herbivores. Snakes, birds, lizards, fox etc are considered as secondary consumer.

·         Tertiary consumers are the top carnivores that eat upon consumers carnivores. Lion, tiger etc are Tertiary consumers.

(iii) Decomposers are referred to parasitic and saprophytic organism which derive their nutrition by breaking down the complex organic molecules into simpler organic compounds. Various bacteria and fungi are considered as decomposers.

Q. Diagrammatically show the Structure of the atmosphere.

Ans : Atmosphere is formed of the gaseous cover which envelops the hydrosphere and the lithosphere. On the basis of temperature the atmosphere can be roughly divided into four zones. They are-

(i) Troposphere: The basal part of the atmosphere which is about 20 km above the earth's surface is known as troposphere. Cloud formation, thundering, lightning etc. take place in this zone. Air temperature gradually decreases with increasing height. This is the most important zone of the atmosphere for organisms.

(ii) Stratosphere: This zone extends upto 30 km in height. The temperature in this zone increases upto 90oC. The increase in temperature in this zone is due to the formation of ozone under the influence of ultra-violet component of sunlight.

(iii) Mesosphere: Mesosphere is about 40 km in height from the stratosphere. Temperature in this zone again goes down upto 80o.

(iv) Ionosphere: The rest of the atmosphere above the mesosphere upto a height of above 400 km above the earth's 1 surface is ionosphere. Most of the gaseous components which become ionized under the influence of the radiant energy remain as ions in this zone. The lower most region of ionosphere is called thermosphere. It is 85 km above the surface of the earth. The layer above ionosphere is called exosphere.

Q. Write about the various functions of ecosystem.

Ans : The ecosystem has many functions. The different functions of an ecosystem are as follows -

·      Ecosystem circulates between leaving and non-leaving organism.

·      In ecosystem flow of energy is consumed by autotrophs in the time of their respiration .growth and any other metabolic reaction.

·      Ecosystem exchange biotic and abiotic materials, in an ecosystem by dimensional and highly complex interrelation different components linked together.

·      Ecosystem adjusts a functional balance among various components.

·      Ecosystem is achieved by a number of limitations, which, is called cybernetics.

Q. What is meant by energy flow in ecosystem? Explain it with an example.    

Ans: The energy from the sunlight is converted by the plants themselves into growing new plants materials. Leaves of trees, flowers, fruits, trunks brunches, roots etc of plants are the plants materials which formed through sunlight. The energy cycle is based on the flow of energy through the ecosystem. Plants are known as producer in the ecosystem because plants can grow by converting the sun's energy into their tissues directly. Different plants and animals are linked to one another through food chain. Each plants or animals can be linked to several plants or animals. Those interlinked chains can be depicted as food web.

In the ecosystem the energy can be depicted in the form of a energy pyramid. It also known as food pyramid which has a base of producer or plants. These are two types of consumers. One is first order consumers and the second one is second order consumers. The pyramid has a narrower middle section that depicts the number and biomass of herbivorous animals are first order consumers and the apex depicts the small biomass of carnivorous animals are the second order consumers.       

The materials are returned to the soil when plants and animals are die. Plants can absorb the nutrients through their roots.

Q. What are the structural features of an ecosystem?

Ans : (i) Biotic structure : The plants, animals and microorganisms present in an ecosystem form the biotic components. These are as follows-

·   Producers : Green plants which trap solar energy and convert it   to potential-chemical energy are called producers.

·   Consumers: All animals and non-green plants which directly or indirectly depend upon the producers for energy are called consumers. They may be herbivores, carnivores, omnivores, detritivores.

·   Decomposers: They derive their nutrition by breaking down the complex organic molecules to simpler organic compounds and ultimately into inorganic nutrients. Various becteria and fungi are decomposers.

(ii) Abiotic structure: The physical and chemical components of an ecosystem constitute its abiotic structure.

·   Physical factors: The sunlight and shade, intensity of solar flux, duration of sun hours, average temperature,
maximum-minimum temperature, annual rainfall, wind, latitude and altitude etc. are some of the important physical features which have a strong influence on the ecosystem.

·   Chemical factors: Availability of major essential nutrients, like carbon, nitrogen, phosphorus, hydrogen, oxygen, level of toxic substances, salts causing salinity and various organic substances present in the soil or water largely influence the functioning of an ecosystem.

Q. What are the functional attributes of an ecosystem?

Ans : The major functional attributes of an ecosystem are as follows -

(i) Food chain, food webs and trophic structure, (ii) Energy flow (iii) Cycling of nutrients, (iv) Primary and secondary production, (v) Ecosystem development and regulation.

Q. What are the significances of food chains and food webs?

Ans: (i) Food chains and food webs play a very significant role in the ecosystem because the two most important functions of energy flow and nutrients cycling take place through them,

(ii) The food chains also help in maintaining and regulating the population size of different animals and thus, help maintain the ecological balance.

(iii) Food chains show a unique property of biological magnification of some chemicals, there are several pesticides, heavy metals and other chemicals which are non bio­degradable in nature. Such chemicals are not decomposed by microorganisms and they keep on passing from one trophic level to another. At each successive trophic level, they keep one increasing in concentration. This phenomenon is known as biomagnifications or biological magnification.

Q. What do you understand by ecological pyramids?

Ans : An ecological pyramid is a graphical representation of an ecological parameter, like number of biomass or accumulated energy at different trophic levels in a food chain in an ecosystem. Ecological pyramids are of three types-

(i) Pyramid of numbers: It is the graphic representation showing the arrangement of number of individuals (population size) of different trophic levels in a food chain in an ecosystem.

(ii) Pyramid of biomass: The total amount of living or organic matter in an ecosystem at any time is called biomass. Pyramid of biomass is a graphic representation of biomass present per unit area in different trophic levels.

(iii) Pyramid of energy: It is a graphic representation of amount of energy trapped per unit time and area in different trophic levels of a food chain.

Q. Write about the flow of energy in an ecosystem.

Ans: Flow of energy in an ecosystem takes place through the food chain and it is this energy flow which keeps the ecosystem going. The flow of energy follows the two laws of thermodynamics-

1st law of thermodynamics states that energy can neither be created nor be destroyed but it can be transformed front one form to another. The solar energy captured by the green plants gets converted into biochemical energy of plants and later into of consumers.

2nd law of thermodynamics states that energy dissipates as it is used or in other words, it gets converted from a more concentrated form to a dispersed form.

The flow of energy through various trophic levels in an| ecosystem can be explained with the help of various energy flow models -

(i) Universal energy flow model: Energy flow through an ecosystem was explained by Odjum as the universal energy flow model. As the flow of energy takes place, there is a gradual loss of energy at every level, thereby resulting in less energy available for next trophic level.

(ii) Single channel energy flow model: The flow of energy takes place in a unidirectional manner through a single channel of green plants or producers to herbivores and carnivore

Q.     What do you understand by primary production and secondary production?

Ans: Primary production: Primary productivity of and ecosystems defined as the rate at which radiant energy converted into organic substances by photosynthesis or chemosynthesis by the primary producers. When organic matter is produced by the primary producers some of it is oxidized or burnt inside their body to form carbon dioxide which is release during respiration. Now, the producers are left with a little less organic matter than what was actually produced by them. This is known as the net primary production (NPP) and the] respiratory loss (R) added to it gives the gross primary production (GPP).

GPP = NPP+R

Secondary production: The food synthesized by green plants through photosynthesis is the primary production which is eaten by herbivores. The plant energy is used up for producing organic matter of the herbivores which, in turn, is used up by the carnivores. The amount of organic matter stored by the herbivores or carnivores is known as secondary production. The energy stored at consumer level for use by the next trophic level is thus defined as secondary production.

Q.      What is homeostasis? What do you understand by feedback mechanism?

Ans: Any environmental stress tries to disturb the normal functioning. On application of a stress, the negative feedback mechanisms start operating, trying to counter the stress to regulate the system. But beyond the homeostatic plateau, positive feedback starks, which further accelerate the stress causing death or collapse of the organism/ system, of an ecosystem. However, the ecosystem by itself tries to resist the change and maintains itself in equilibrium with the environment due to a property known as homeostasis. Homeostasis is the inherent property of all living systems to resist changes. However, the system can show this tolerance only within a maximum and a minimum range. Within this range, if any stress tries to cause a deviation, then the system has its own mechanisms to counteract these deviations which are known as negative feedback mechanisms. So, negative feedback mechanisms are deviation counteracting mechanisms which try to bring the system back to its ideal conditions. But if the stress is too high and beyond the range of tolerance then another type of mechanism, known as positive feedback mechanism starts operating. So, the positive feedback mechanisms add to the stress conditions and tend to take the system away from the optimal conditions.

Q. Describe the process of ecological succession.

Ans :   The process of succession takes place in a systematic order of sequential steps as follows -

a.             Nudation: It is the development of a bare area without any life form, which is caused due to landslides, volcanic eruption drought, frost, overgrazing, industrial activities etc.

b.             Invasion: It is the successful establishment of one of more species on a bare area through dispersal or migration, followed by ecesis or establishment. Dispersal of the seeds, spores etc. is brought about by wind, water, insects of birds. Then the seeds germinate and grow on the land". As growth and reproduction start, these pioneer species increase in number and form group or aggregations.

c.             Competition and coactions: As the number of individuals grows, there is competition, both inter-specific and intra-specific for space, water and nutrition. They influence each other in a number of ways, known as coaction.

d.             Reaction: The living organisms grow, use water and nutrients from the substratum, and in turn, they have a strong influence on the environment which is modified to a large extent, and this is known as reaction. The modifications sometimes become unsuitable for the existing species and favour Some which replace them. Thus reaction leads to several seral communities.

e.             Stabilization: The succession ultimately culminates in a more qr less stable community called climax which is in equilibrium-with the environment.

Q. Write a short note on tropical rain forest.

Ans : The tropical rain forests are evergreen, broad leaf forests found near the equator. They are characterized by high temperature high humidity and high rainfall, all of which favour the growth of trees. All through the year, the climate remains more or less uniform. They are the richest in biodiversity. Different types and layers of plants and animals are present m the tropical rain forests, e.g. the emergent layer-is the topmost layer of the tallest broad-leaf evergreen trees, below which lies the canopy where top branches of shorter trees form an umbrella like cover. Below this is present the underestory of still smaller trees. On the tree trunks, some woody climbers are found to grow which are known are epiphytes. The understory trees, unusually receive very dim sunlight. The shrub layer receives even less sunlight and the ground layer commonly known as forest floor receives almost no sunlight and is a dark layer. Most of the animals like bats, birds, insects etc. occupy the bright canopy layer while mpnkeys, toads, snakes etc. keep on moving up and down in sunny and darker layers. Termites, fungi, mushroom etc. Grow on the ground layer. Interestingly, the flowers of forest trees are very large, colourful, fragrant and attractive which helps in pollination by insects, birds, bats etc. The silent valley in Kerala is the only tropical rain forest lying in India.

Q. Write a short note on Savannas.

Ans: Tropical grasslands occur near the borders of tropical rainforest in regions of high average temperature and low to moderate rainfall. In Africa, these are typically known as Savannas, which have tall grasses with scattered shrubs and stunted trees. The Savannas have a wide diversity of animals, including zebras, giraffes etc. During dry season, fires are quite common. Termite mounds are very common here.

Tropical Savannas have a highly efficient system of photosynthesis. Deliberate burning of these grasslands can release huge quantities of carbon dioxide, another green house gas, responsible for global warming.

Q. What are different types of deserts?

Ans :  Deserts are of three major types -

·         Tropical deserts, like Sahara and Nanib in Africa and Thar Desert of Rajasthan in India are the driest of all with only a few species. Windblown sand dunes are very common.

·         Temperate deserts, like Mojave in Southern California where day time temperatures are very high in summer and cold in winter.

·         Cold deserts, like the Gobi desert in China have cold winters and warm summers.

Q. What are different types of lakes ?

Ans :                                             

·         Oligotrophic lakes, which have low nutrient concentration,  

·         Eutrophic lakes, Which are over nourished by nutrients like nitrogen and phosphorus, usually as a result of agricultural run-off or municipal sewage discharge. They are covered with algal blooms, e.g. Dal lake.

·         Dystrophic lakes, that have low p^H, high humic acid content and brown waters, e.g. bog lakes.

·         Endemic lake, which is very ancient, deep and has endemic fauna which are restricted only to that lake, e.g. the Lake Baikal in Russia.                              

·         Desert salt lakes, which occur in arid regions and have developed high salt concentrations as a result of high evaporation. e.g. Sambhar lake in Rajasthan.

·         Volcanic lakes, that receive water from magma after volcanic eruptions e.g. many lakes in Japan.

·         Meroraictic lakes, that are rich in salts and art permanently stratified, e.g. lake Nevada.

·         Artificial lakes or impoundments, that are created due to construction of dams, e.g. Govindsagar lake at Bhakra Nangal.

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