Extensive geographical belt of forest known as ‘Taiga’, belongs to
(a) Coniferous forest (b) Temperate forest
(c) Tropical forest (d) Sub-tropical forest
Annual rainfall in the area of a tropical deciduous forest is
[BHU 1986]
(a) Over 300 cm (b) 200-250 cm
(c) 100-150 cm (d) 50-75 cm
Acacia, Euphorbia and Cenchrus grass are characteristics of
[CBSE PMT 1998]
(a) Grassland biome (b) Desert biome
(c) Chapparal biome (d) Temperate biome
Biosphere is [Pb. PMT 2000]
(a) Global ecosystem
(b) Global community
(c) Living organism
(d) Count of organism on earth
In sedimentary cycles, the reserve pool is
(a) Air
(b) Water
(c) Lithosphere
(d) Lithosphere and atmosphere
A long term global cycle which is linked by water and in which sea floor rising play an important role is
(a) Water cycle (b) Carbon cycle
(c) Phosphorus cycle (d) Carbon and nitrogen cycle
The largest reservoir of sulphur and phosphorus in biosphere is
(a) Atmosphere (b) Ocean
(c) Organism (d) Rocks
The most crucial role in cycle is played by
(a) Evaporation from water sheets
(b) Transpiration by plants
(c) Absorption of by plants
***
(d) Percolation of rain water into soil upto water table
Putrefaction, lightening and thunder help in
(a) N2 cycle (b) P cycle
(c) S cycle (d) Hydrologic cycle
Which one of the following element is the critical limiting factor in the function of ecosphere because of its irretrievable loss into the ocean [CPMT 1989]
(a) Phosphorus (b) Calcium
(c) Magnesium (d) Iron
Which one of the following pairs is a sedimentary type of biogeochemical cycle [CBSE PMT 1995; BHU 2000]
(a) Phosphorus and carbon dioxide
(b) Oxygen and nitrogen
(c) Phosphorus and nitrogen
(d) Phosphorus and sulphur
1
c
2
a
3
c
4
b
5
a
6
c
7
c
8
d
9
a
10
a
11
a
12
d
(c) Because according to altitude and latitude, geological conditions are changed.
(c) Climatic conditions of tropical deciduous forest are annual temperature 22-32oC, annual rainfall 90-160 cm and dry months are 6-8.
5 (a) Biosphere is the global ecosystem where living organisms can survive.
(c) Lithosphere is the solid components of the earth crust, rocks, soil and mineral.
(a) All parts of the hydrosphere viz. oceans, lakes, rivers, ponds lose water through evaporation. At any time, atmosphere contains 0.13×1020 G of water vapour. In higher altitudes, water vapours cool, condense and form clouds. The clouds move to long distances. They ultimately precipitate.
(a) A large amount of phosphate is lost in the sea by sedimentation. This is irretrievable loss.
(d) In sedimentary cycles of matter, materials involved in circulation between biotic and abiotic components of biosphere are non gaseous and the reservoir pool is lithosphere e.g., phosphorus, calcium, magnesium. Sulphur has both sedimentary and gaseous phases
Chapparal occurs in area
(a) Africa (b) Siberia
(c) Mediterranean(d) Arabia
Rainfall occurs in chapparal during
(a) The whole year (b) Summer
(c) Winter(d) Spring-autumn
Deserts occur in areas of
(a) Adverse human disturbance
(b) Underground saline water
(c) Little underground water
(d) Rain shadow
All types of latitudinal biomes are found telescoped on high hills found in
(a) Tropical areas (b) Subtropical areas
(c) Temperate areas(d) None of the above
Biome represents
(a) All the organisms of earth
(b) Flora of a land
(c) Flora and fauna of a land
(d) A major ecosystem delimited by climate or geography
Sedimentary cycle having a small gaseous component also is found in
(a) ‘P’ cycle (b) ‘S’ cycle
(c)‘N’ cycle (d) ‘C’ Cycle
Which is involved in sedimentary cycle
(a) C (b) N
(c)H(d) S
The reservoir pool for gaseous cycles of matter is
(a) Atmosphere (b) Hydrosphere
(c)Both (a) and (b)(d) Lithosphere
The reservoir pool of carbon is
(a) Air and water (b) Fossil fuels
(c)Rocks(d) All of these
For recycling of materials which one is most necessary
(a) Producers (b) Consumers
(c)Decomposers(d) None of above
Burning of fossil fuels affects
(a) Nitrogen cycle (b) Carbon cycle
(c)Phosphorus cycle (d) Water cycle
In carbon cycle, source of carbon to plants is
(a) Atmospheric CO2 (b) Carbonate rocks
(c)Fossil fuels (d) All of these
The process of evapo-transpiration and precipitation is known as
(a) Carbon cycle (b) Hydrological cycle
(c)Nitrogen cycle(d) All of these
Global water cycle involves
(a) Forest trees
(b) Algae
(c)Microorganisms
(d) Evaporation of water from water bodies
Local water cycle involves
(a) Living beings (b) Physical factors
(c)Atmosphere(d) None of these
The agent/s which make/s free atmospheric nitrogen available to plants is/are
(a) Lightening
(b) Free living nitrogen fixing bacteria
(c)Symbiotic nitrogen fixing bacteria
(d) All of these
Non biological nitrogen fixation is
(a) Electrochemical (b) Photochemical
(c)Both (a) and (b)(d) None of these
Phosphorus is mostly found in rocks in combination with
(a) Calcium (b) Iron
(c)Aluminium(d) All of these
Phosphorus cycle is
(a) Gaseous cycle
(b) Perfect cycle
(c)Imperfect cycle
(d) Partly gaseous and partly sedimentary
Phosphorus of ocean becomes available to land plants due to
(a) Sea birds (b) Deep sea activities
(c)Ocean spray(d) All of these
Volcano eruption disturbs
(a) Phosphorus cycle (b) Nitrogen cycle
(c)Carbon cycle(d) Sulphur cycle
Phosphorus cycles in the form of
(a) (b) (gas)
(c)(d)
Inorganic element that changes food into usable energy is
(a) S (b) P
(c)Ca(d) Mg
Degradation of proteins play a part in
(a) Calvin cycle (b) Water cycle
(c)Sulphur cycle (d) Nitrogen cycle
In which of the following cycle, an atmospheric cycle is absent
(a) Carbon cycle (b)Phosphorus cycle
(c)Nitrogen cycle (d) Sulphur cycle
Which of the following is the major source of phosphorus
(a) Plants (b) Animals
(c)Crystalline rocks(d) Deserts
A biogeochemical cycle without an atmospheric component is
(a) Carbon cycle (b) Phosphorus cycle
(c)Nitrogen cycle (d) Sulphur cycle
Biogeochemical cycling refers to cycling of [DPMT 1983]
(a) Energy in the ecosystem
(b) Nutrients in the ecosystem
(c)Water
(d) Gases between plants and animals
Cycling of elements in an ecosystem is called
[DPMT 1983; MP PMT 1987, 99; BHU 2000]
(a) Chemical cycle (b) Geochemical cycle
(c) Biogeochemical cycle (d) Geological cycle
The circulation or cycling of elements in an ecosystem is known as [MP PMT 1987; CBSE PMT 1999]
(a) Geological cycling (b) Geo-chemical cycling
(c)Bio-geochemical cycling(d) Nutrient cycling
Maximum contribution of O2 is from [CBSE PMT 1989]
(a) Phytoplankton (b) Grasslands
(c)Herbs and shrubs(d) Dense forest
In water receiving regions, what does forest regulate
[MP PMT 1989]
(a) Hydrological cycle (b) Carbon cycle
(c) Nitrogen cycle (d) Calcium cycle
Which of the following cycle would be affected if decomposers of an ecosystem vanish [RPMT 1992]
(a) Producer’s cycle (b) Consumer’s cycle
(c) Decomposer’s cycle (d) Biogeochemical cycle
Nitrogen is a critical element of the ecosystem because it is
[BHU 1996]
(a) Essential element (b) Abundant in atmosphere
(c)Labile(d) Fixed by microbes
The phosphorus rich fertilizer obtained from sea birds along the coast of Chile and Peru, is [Rohtak 1996]
(a) Guano (b) Bone meal
(c)Dung(d) Urea
CO2 content of atmosphere has increased in the last 150 years from [AIIMS 1997]
(a) 25 to 35 ppm (b) 270 to 340 ppm
(c)0.027 to 0.34 ppm(d) 0.2 to 0.3 ppm
Role of bacteria in carbon cycle is [CBSE PMT 1998]
(a) Photosynthesis
(b) Chemosynthesis
(c)Breakdown of organic compounds
(d) Assimilation of nitrogen compounds
One way cycle is [Pb. PMT 1999]
(a) CO2 cycle (b) H2O cycle
(c)Free energy cycle(d) O2 cycle
Study of Biogeochemical cycles is called Biogeochemistry. Its father is Vernadsky (=Winodgsky). It involves
[CBSE PMT 1999]
(a) Cycling of energy (b) Cycling of gases
(c)Cycling of nutrients(d) Cycling of water
Amount of nitrogen fixed electrochemically and photochemically is [Kerala 2000]
(a) 140 mg/m2/yr (b) 78 mg/m2/yr
(c)35 mg/m2/yr(d) 15 mg/m2/yr
(e) 350 mg/m2/yr
Crystalline rocks are natural source of biogenetic element
[Kerala 2000]
(a) Calcium (b) Phosphorus
(c)Magnesium(d) Calcium
(e) Sulphur
Azotobacter and Clostridium are nitrogen fixing bacteria and found in [Haryana 2000]
(a) Nodulated roots (b) Leaves of certain plant
(c)Free in soil(d) None of the above
The limiting factor in nitrification of soil is [AIIMS 2000]
(a) pH (b) Temperature
(c)Light(d) Air
Biochemical cycle with gaseous phase is [DPMT 2001]
(a) Carbon (b) Sodium
(c)Phosphorus(d) Magnesium
Which one is sedimentary cycle [Kerala 2001]
(a) Oxygen cycle (b) Nitrogen cycle
(c)Hydrogen cycle(d) Phosphorus cycle
(e) Carbon cycle
Nitrogen content of biosphere remains constant due to
[AFMC 2001]
(a) Nitrogen fixation (b) Nitrogen cycle
(c)Industrial pollution(d) Absorption of nitrogen
Which of the following is present in maximum amount in atmosphere [DPMT 2002]
(a) Oxygen (b) Nitrogen
(c)Carbon dioxide(d) Hydrogen
Nitrates are transformed into nitrogen by [CPMT 2003]
(a) Ammonifying bacteria (b) Nitrifying bacteria
(c)Denitrifying bacteria(d) Both (a) and (b)
In the phosphorus cycle, phosphate becomes available by weathering of rocks first to [Pb. PMT 2004]
(a) Consumers (b) Producers
(c)Decomposers(d) None of these
Grassland biome for its maintenance requires
(a) Periodic fire (b) Intensive grazing
(c) Mowing (d)All the above
In India, temperate evergreen vegetation occurs mostly in
[CPMT 1983, MP PMT 1990]
(a) Rajasthan and South Punjab
(b) Eastern and Western Himalayas less than 3500 m
(c) Western Himalayas above 3500 m
(d) Western Ghats and Assam
The most striking difference between tropical rain forest and temperate forest is that [RPMT 1988]
(a) The tropical rain forests have preponderance of angiosperms while the temperate one have preponderance of gymnosperms
(b) The trees of temperate forests are taller than those of tropical rain forests
(c) Plants of temperate forests are comparatively more mesophytic
(d) Tropical forests are comparatively more homogeneous
Alpine forests of Himalayas have [MP PMT 1991]
(a) Tall evergreen coniferous trees
(b) Tall broad-leaved evergreen trees
(c) Tall broad-leaved deciduous trees
(d) Dwarf shrubby plants
Alpine forests occur at altitude [MP PMT 1992]
(a) 3900–6000 m (b) 1900–3000 m
(c) 1000–1500 m (d) 500–1000 m
Dense evergreen vegetation of broad sclerophyllous leaves and shrubs with fire resistant resisnous plants is known as
[AIIMS 1997]
(a) Chapparral vegetation (b) Savannah vegetation
(c) Steppe grassland(d) Tundra vegetation
A treeless biome is [AFMC 1999; MP PMT 2000]
(a) Tundra (b) Grassland
(c) Desert(d) All the above
More than half of the earth’s flora and fauna is found in
[HP PMT 2001]
(a) Tropical rain forests
(b) Montane temperate forests
(c) Deciduous forests
(d) Alpine forests
About how much water is recycled in the form of rains per year
(a) < 4.46 times 105> gram per year
(b) < 4.46 times 1010> gram per year
(c) < 4.46 times 1020> gram per year
(d) < 4.46times 1030> gram per year
Fishing and Guano birds assist the cycling of
(a) Nitrogen (b) Phosphorus
(c) Carbon (d) N2 and carbon both
Of more immediate concern regarding carbon cycle is
(a) Output rate of carbon locked in deposits of coal, petroleum and natural gas
(b) Green house gases
(c)Increase in the total mass of carbon in earth’s atmosphere by 12-14%
(d) All above
Hydrological cycle comprises of two overlapping cycles
(a)Surface waters and atmospheric cycles
(b) Oceanic and fresh water cycles
(c)Ground water and atmospheric cycles
(d) Global and smaller cycles
If there was no CO2 in the earth’s atmosphere, the temperature of earth’s surface would be [CBSE PMT 1998]
(a) As such
(b) Less than the present level
(c) Increase from present level
(d) Dependent upon oxygen amount of the environment
Concentration of nitrogen remains constant by [AFMC 2001]
(a) Nitrogen cycle (b) Thundering and light
(c)Enzymes(d) Both (a) and (b)
Read the assertion and reason carefully to mark the correct option out of the options given below :
(a) If both the assertion and the reason are true and the reason is a correct explanation of the assertion
(b) If both the assertion and reason are true but the reason is not a correct explanation of the assertion
(c) If the assertion is true but the reason is false
(d) If both the assertion and reason are false
(e) If the assertion is false but reason is true
Assertion : Biomes are the major ecosystem of the world.
Reason : Tundra is an example of biome.
Assertion : Taiga is also called North coniferous forest.
Reason : The ground flora is absent in Taiga.
Assertion : Temperate deciduous forest is two – storeyed forest.
Reason : Two stories are formed of soft – wood and hard – wood trees.
Assertion : When the rain forest is removed, grasslands appear.
Reason : In rain forest, nutrient cycling is slow.
Assertion : Chaparral is also called “shrub forest”.
Reason : Trees are totally absent in chaparral.
Assertion : Savannahs show rich species diversity.
Reason : The biome is prone to fires.
Assertion : Grasslands are suitable for grazing food chain.
Reason : Grazers are mostly small animals.
Assertion : Coral reef are equivalent to tropic rain forest.
Reason : Maximum diversity of Biota occurs in the reefs.
Assertion : Biosphere has three subdivisions.
Reason : All subdivisions of biosphere are independent.
Assertion : Tropical rain forests are disappearing fast from developing countries such as India.
Reason : No value is attached to these forests because these are poor in biodiversity.
[AIIMS 2003]
Assertion :The whole of biogenetic nutrients show circulation.
Reason :Biogeochemicals cycles operate in the biosphere.
Assertion :Nitrogen is an important structural and functional constituents of living protoplasm.
Reason : Plants and animals mostly depend upon atmospheric nitrogen.
Assertion :Atmospheric nitrogen is always fixed by nitrogen-fixing micro-organisms.
Reason : Decomposers release nitrogen from dead bodies of plants and animals.
Assertion : Azolla is used in paddy fields.
Reason :The fern is capable of fixing nitrogen.
Assertion : Phosphorus cycle is imperfect.
Reason :Human activities has made phosphorous less cyclic.
Assertion :Hydrologic cycle is a perfect one.
Reason :The cycling of water is a fast process.
Assertion :Excess of sulphur reaches to reservoir pool.
Reason :Thiobacillus and Desulpho vibrio convert elemental sulphur into the sulphate.
Assertion :Some toxic element also cycle.
Reason :Human activities upset the cycle and make them accessible to living beings.
Assertion : Gaseous cycle is faster than the cycle of matter.
Reason : Sedimentary cycles are very slow.
Assertion : Water cycle can be divided into two global and biological.
Reason : Both type of water cycles are independent.
Biomes and Biosphere
1
a
2
a
3
b
4
d
5
a
6
b
7
a
8
b
9
d
10
c
11
d
12
b
13
d
14
a
15
d
16
c
17
c
18
d
19
a
20
d
21
d
22
b
23
a
24
c
25
c
26
b
27
c
28
b
29
a
30
b
31
c
32
d
33
c
34
b
35
a
36
c
37
a
38
a
39
b
40
d
41
d
42
a
43
d
44
b
45
d
46
d
47
b
48
d
49
b
50
a
51
c
52
a
53
b
54
c
55
d
56
b
57
b
58
d
59
d
60
a
61
c
62
a
63
c
64
c
65
d
66
a
67
b
68
b
69
a
70
b
71
b
72
a
73
c
Bio-Geochemical cycle
1
a
2
b
3
b
4
a
5
d
6
d
7
a
8
d
9
c
10
c
11
c
12
a
13
a
14
b
15
d
16
c
17
d
18
c
19
b
20
a
21
b
22
d
23
a
24
d
25
c
26
d
27
c
28
a
29
a
30
c
31
b
32
d
33
b
34
c
35
b
36
b
37
c
38
d
39
a
40
a
41
d
42
c
43
a
44
b
45
c
46
c
47
c
48
c
49
b
50
c
51
a
52
a
53
d
54
b
55
b
56
c
57
b
Critical Thinking Questions
1
d
2
b
3
a
4
d
5
a
6
a
7
d
8
a
9
c
10
b
11
d
12
a
13
b
14
d
Assertion and Reason
1
b
2
c
3
d
4
d
5
c
6
e
7
c
8
a
9
c
10
c
11
e
12
c
13
d
14
c
15
b
16
b
17
c
18
b
19
b
20
c
Biomes and Biosphere
(a) Temperature influences the vegetation of an area and precipitation affects both plant and animal life. Hence both ecological factors are most strong determinants of various biomes.
(a) Because at the surface of water, light is available easily.
(d) A large community of plants and animals, characterized by its particular type of dominant vegetation and its associated animals is called Biomes.
(a) The solid component of earth is called lithosphere.
(b) Temperate deciduous forests occur in areas having warm summers, cold winters and moderate amount of precipitation (75-150 cm annually).
(b) Because for the environmental balance, communities of organisms and plants depend upon each other.
(d) Because all animals survive in low water concentration.
(c) As a result of manipulation by man, the biosphere has become transformed into human dominated environment of noosphere (noo=mind).
(d) Alpine tundra is the highest attitudinal biome which occurs near the top of very high mountains having permanent snow, e.g., Himalayas.
(d) The taiga or northern temperate coniferous forest or boreal forests consist of evergreen, cone bearing trees.
(c) Chapparal occurs in mediterranean area (hence mediterranean scrub forest), Pacific coast of North America, Chile, South Africa and South Australia.
(d) Desert biome lacks rain (less than 25 cm) due to either being present in rain shadow (area beyond high mountains which cut off clouds e.g., Tibet). Lack of cloud intercepting mountains or lying away from cloud seeding regions. e.g., death valley of U.S.A.
(d) Biomes are ecosystems of plants and animals that occur over wide areas of land within specific climatic regions and are easily recognized by their overall appearance.
(a) Tropical rain forests are mainly found in central America along Amazon and Orinoco rivers. South east Asia including India. In India, tropical rain forests occur in western Ghats, Assam and Andamans.
(c) Succulent plants are characteristics of deserts. Succulents plants store water. They have mucilage to retain water. Stomata are sunken and usually open during night only e.g., Opuntia, Euphorbia.
(c) Woody plants (trees and shrubs) also occur in grasslands as scattered individuals or in belts. These are called a ‘Savannah’.
(b) Himalayan coniferous forests are attitudinal forests which occur in the Himalayas at the attitude of 1700-3000m.
(a) Man and Biosphere programme was formally launched by UNESCO in 1971. It is an inter disciplinary programme of research and training with emphasis on ecological approach to the study of interrelationship between man and his environment.
(b) Plankton’s are passively drifting or floating organisms. Most of these minute organisms, plankton includes photosynthesizing organisms as well as heterotrophic organisms.
(d) Because these are the sub-divisions of biosphere.
(c) Tundra biome is characterised by desert like levels of precipitation (less than 25 cm annually), extremely long and cold winters and short warmer summers.
(b) Because abiotic (non-living) and biotic (living) components together constitute the biosphere and abiotic component is composed of the air (atmosphere), earth (lithosphere) and water (hydrosphere).
(a) In the tropical rain forests of south America, Africa and the Indo-Malayan region near the equator, there is plenty rainfall (minimum 190 cm/yr) and weather is always warm (20-25oC).
(b) Ozone layer is the ultraviolet rays protector of earth.
(d) Because desert lands are included in this biome.
(d) Tropical rain forest shows maximum biodiversity on land is shown by this biome and it is estimated that one half to two-thirds of all species of terrestrial plants and insects live in tropical forests.
(a) The entire inhabited part of the earth and its atmosphere (including the living and the non living components) forms the biosphere.
(d) Fossorial animals are abundant in desert grassland which are adopted to live underground inside burrows (in low temperature).
(a) Vegetation of tropical rain forests show stratification. Stratification is the grouping of plants in a forest into two or more well defined layers depending upon their height like tall tress, medium sized trees, small trees, bushes, herbs, etc.
(b) Its dominant climax vegetation consists of broad-leaved hardwood (dicot) tree like Oak, Elm, Maple, Birch, etc.
(c) It is a broad leaved evergreen shrub forest of hard and thick-leaved small trees and shrubs which usually contain resin but are resistant to fires. Both plants and animals are adopted to frequent and long periods of drought.
(b) Flora of thorn forests include Prosopis cineraria, Acacia senagal, Capparis decidua, Salvadora oleoides, Asparagus racemosus, Ephedra foliata.
(d) The tropical rainforests are most diverse and highly dense with maximum productivity (approximately 12000 k cal /m2/yr).
(d) Benthonic organisms are found along the floor of the sea bed, bottom of a lake and include creeping, crawling or sessile organisms. The benthonic region has scavengers and decomposers.
(c) Savannah occurs in North Australia, India, Central and Southern Africa including east central S. Africa.
(c) Tundra receives very little precipitation, around 25 cm/ year, mostly in the form of snow. The area is covered by snow for most part of the year. The highest summer temperature is 10oC. It is unable to melt snow except for the upper 10-20 cm. The remaining part of the soil is in permanently frozen (permafrost) condition.
(a) India has identified 14 areas as biosphere reserves. Of these, the Nilgiri biosphere reserve, including parts of Karnataka, Kerala and Tamilnadu was declared in 1986 (First one).
(b) Productivity of the tropical rain forest is very high 12000 Kcal/m2/yr. as compared to 3000 Kcal/m2/yr. for temperate deciduous, 2000 Kcal for taiga and only 200 Kcal/m2/yr for tundra.
(b) The biome occurs in equatorial or sub equatorial regions where both rainfall and warmth are abundant. Rainfall is above 140 cm/yr usually between 200-500 cm/yr. It may be up to 1000 cm. Rain occurs through major parts of the year.
(a) Man and biosphere programme is an international bio-logical programme of UNESCO (United Nations Educational Scientific and Cultural Organization) which was started in 1971 but was introduced in India in 1986.
(c) Prairies contain tall grasses and shrubs.
Bio-Geochemical Cycle
(a) Because CO2 is utilized in photosynthesis of plants.
(b) In water-logged soils and other anaerobic areas, some bacteria utilize the oxygen of nitrates for meeting their requirements. This reduces nitrate into gaseous forms of nitrogen which escape into atmosphere. This phenomenon is called denitrification.
(b) Nitrobacter is a N2 fixing organism, it fixes atmospheric free N2 into soluble salts like nitrites and nitrates. The fixed N2 is absorbed by plants when herbivores feed on these plants, the N2 flows on the carnivores through food chain hence it is important for the N2 cycle.
(d) Carbon enters the biotic system through photosynthesis. In photosynthesis green plants utilize CO2 and incorporate the carbon of CO2 in Glucose. In respiration, burning of biomass and fossil fuels release a lot of CO2. Burning of fossil fuels adds 6×1012kg of carbon into atmosphere.
(d) The term biogeochemical cycling is used for exchanges/circulation of biogenetic nutrients between living and nonliving components of biosphere (thousands of ecosystem constitute the biosphere).
(c) The cyclic movement of chemical elements of biosphere between organism and environment are referred as ‘Biogeochemical cycles’. The word Bio refers to the living organisms and geo refers to the rocks, soil, air and water of the earth.
(c) Because during nitrification process ammonium compounds are oxidized into nitrate in two stages (i) these are acted upon by the nitrite bacteria (Nitrosomonas) and oxidized into NO2 and (ii) the nitrite thus formed is again acted upon by the nitrate bacteria (Nitrobacter) and further oxidized into nitrate NO3 and these are absorbed by plants. Sometimes Nitrogen fixing bacteria (Rhizobium leguminosarum), lives in the root nodule of the plants of leguminosae family can fix direct atmospheric nitrogen. Some other bacteria like cyanobacteria and photosynthetic bacteria can also fix the nitrogen in the soil. The denitrifying bacteria can convert the salts of nitrogen directly into atmospheric nitrogen.
(a) The biogeochemical cycles are classified into 2 types namely gaseous cycles and sedimentary cycles.
(d) In sedimentary cycles the main reservoirs are soil and rocks e.g., Sulphur cycle, phosphorus cycle etc.
(c) In gaseous cycles of matter the materials involved in circulation between biotic and abiotic components of biosphere are gases or vapours and the reservoir pool is atmosphere or hydrosphere. e.g., C, H, O2, N2 and H2O.
(d) Carbon is present in the abiotic environment in following forms (i) CO2 in air or atmosphere (ii) Dissolved CO2 or carbonic acid and bicarbonate in water or hydrosphere (iii) Carbonates and graphite in the rocks.
(c) The decomposers are heterotroph organisms that break up the dead bodies of plants and their waste products into smaller bits or molecules. The reducers release molecules to the environment as chemical to be used again by the producers.
(b) Because burning of fossil fuel release a lot of CO2.
(a) Carbon present in the atmosphere and hydrosphere is available to the living world as free or dissolved CO2. It is picked up by producers in the process of photosynthesis and changed to organic compounds.
(d) Global water cycle consists of evaporation and precipitation of water. All parts of the hydrosphere (viz., oceans, lakes, rivers, ponds, moist soil) lose water through evaporation.
(d) N2 fixation occurs in two ways namely-Electrochemical fixation and Biological fixation. Lightening is the electrochemical fixation and free living nitrogen fixing bacteria and symbiotic nitrogen fixing bacteria are the biological N2 fixing organisms.
(c) With the help of lightning (electro-chemical) and high energy radiations (photochemical reactions), a small quantity of nitrogen combines with O2 to form nitrogen oxides that are washed down with rain water.
(c) Because atmosphere or gaseous cycle is absent.
(c) Phosphorus is obtained from soil as orthophosphate (PO43-). Organic phosphorus circulates in nature from plants to animals. Phosphate is released by decomposers (Phosphatising bacteria) back to soil.
(b) Usable energy is ATP in which phorphorus is present.
(d) Plants and animals contain nitrogen in their body protein. After death, the proteins of dead bodies are decomposed into amino acids and ammonia. This ammonia may be converted into nitrates or free nitrogen.
(c) The main source of phosphorus is rocks. Through erosion and weathering phosphorus is made available in the soil.
(b) Nutrient cycles are exchanges, storage and transfers of biogenetic nutrients through various components of ecosystem so that the nutrients can be used again and again.
(a) Major source of O2 liberation is photosynthesis and about 90% of total photosynthesis is done by phytoplankton.
(d) Recycling of material is carried out by decomposers. If decomposers of an ecosystem vanish recycling of materials are stopped.
(a) The excess of phosphate in the bodies of animals is excreted out through faces. The bird guano (excreta) contains a large amount of phosphate.
(b) CO2 conc. was about 270 ppm in 1750 and 368 ppm in 2000. The rise has been due to large scale deforestation (for grazing land, cropland or urban estates), change in land use and large scale combustion of fossil fuels.
(d) Phosphorus cycle is sedimentary cycle because its main reservoirs are soil and rocks.
(b) 78.03% of the atmosphere consists of nitrogen. Some is being added to it through volcanic eruptions, erosion of sedimentary rocks and denitrification.
(c) Common denitrifying bacteria are Pseudomonas aeruginosa and Thiobacillus denitrificans. Which reduces nitrate into gaseous forms of nitrogen which escape in to atmosphere.
(b) In the phosphorus cycle, weathering makes phosphate available to the soil from where plants or producers get them first.
Critical Thinking Questions
(d) Grazing, fire and mowing help to maintain grassland and prevent woody species to invade the area.
(b) They are altitudinal forests which occur in the Himalayas at the altitude of 1700-3000m. They are evergreen because the needle shaped leaves of the coniferous plants persist for 2-7 yrs.
(a) Alpine is a treeless area on high mountains (above 3500 m) which has snow for long months.
(a) Diversity of life is so high that a hectare of the forest may have as many as 200 species of trees, 70-80% of all insects and 80-85% of all birds are known from tropical forests
(c) The total world precipitation amounts to 4.46×1020 G per year. This means that the atmosphere must be refilled with water vapours 34 times in a year.
(a) Hydrological cycle is actually made of two overlapping cycles larger global water cycle consists of evaporation and precipitation of water and smaller biological water cycle involves entry of water into living beings and its return to the physical environment.
(b) CO2 layer around earth surface acts as insulator and does not allow heat of the earth to escape into space thus keeping the earth warm.
Assertion and Reason
(b) A biome is defined as a large natural ecosystem which is distinct in its climate conditions and has its specific type of plant and animal life. Biomes are two types – terrestrial and aquatic. The major terrestrial biomes are – tundra, taiga, deciduous forest, tropical rain forest, chaparral, tropical savannah, grassland and desert.
(c) Taiga biome occurs just South of tundra across North America, Europe and Asia It is also found in the Southern hemisphere (e.g., – parts of New Zealand). Dominant vegetation consists of evergreen conifers which are able to tolerate wide fluctuation of temperature, light and soil. They are pine, fir, hemlock, spruce, jumper, yew, larch, deodar. The ground flora consists of herbs, ferns, mosses and lichens.
(d) Temperate deciduous forest are four – storeyed. The top stratum is occupied by trees reaching a height of 30–40 m. There is an understorey of small trees, an intermediate stratum of shrubs and a ground stratum made of herbs, grasses, ferns, mosses and lichens. Vines are found here and there. A few soft – wood trees (conifers) may occur at places interspersed with hard – wood trees.
(d) When the rain forest is removed, a secondary forest often develops that includes soft – wood trees such as Musanga (Africa), Cecropia (America) and Macoranga (Malaysia). Efficient direct nutrient cycling by mutualistic micro – organisms is a remarkable property of rain forests that enable them to be as luxuriant on poor soils as on more fertile sites.
(c) Chaparral is a broad – leaved evergreen shrub forest of hard and thick leaved small trees and shrubs which usually contain resin but are resistant to fires. Crop land is man made ecosystem. Man has been doing his best in modifying the cropland to get maximum benefit out of them. A cropland ecosystem may be illustrated by crops like wheat, maize, rice, sugarcane, etc.
(e) Tropical savannahs are grasslands with scattered trees or clumps of trees. The areas of tropical savannah have one or two prolonged dry seasons when fires are an important part of the environment. Since both trees and grass must be resistant to drought and fire, the number of species in the vegetation is not large.
(c) When natural grasslands become pasture, the native grazers are replaced by the domestic kind, cattle, horses, sheep and goats. Grasslands are adapted to heavy energy flow along the grazing food chain. Large herbivores are a characteristic feature of grasslands. The general food chain of grassland’s :
(a) Coral reefs are the specialized ecosystem of ocean which are among the most productive of all ecosystem anywhere, with a diversity equalled only by tropical rainforest. The amount of oxygen is very high. During the day it may reach 250 percent of saturation because of the production of O2 by algae in the reef structure. The productivity of reefs is also caused by quickly and efficient running of nutrients cycle between the components of reef ecosystem. No organic matter is incorporated permanently into the sedimentary portion of system portion of reef. The condition of rapid nutrient cycling allow a mechanism by which the natural paucity of nutrients in the ocean can be effectively circumvented. All these conditions favour the high biodiversity in coral reef.
(c) Living mantle or biosphere has three subdivisions hydrosphere, lithosphere and atmosphere. They do not occur in isolation but interact with one another in more than one way and support the living beings.
(c) Tropical rain forests are located in the equatorial regions whereever the annual rainfall exceeds 140 cm. They are also called jungles and cover one twelveth of earth’s surface but contain more than half of the earths flora and fauna (i.e., rich in biodiversity). Now-a-days these forests are becoming disappearing due to excessive use in domestic purposes like fuel, furnitures, accomodations, cloths, resin, gum, etc.
(e) Circulation of biogenetic materials between the living and the non-living worlds is called cycles of matter of biogeochemical cycling. The important biogeochemical cycles that operates in biosphere are carbon cycle, sulphur cycle, O2 cycle, N2 cycle, etc. The whole of biogenetic nutrients are not always in circulation. For example, rocks from which nutrients are very slowly transferred to the cycling pool.
(c) Nitrogen is a component of amino acids, proteins enzymes, nucleotides and nucleic acids, which form important constituents of living protoplasm. The atmosphere contains approximately 80% nitrogen gas which cannot be directly utilized by most organisms except certain nitrogen fixers. Animals mostly depend upon the organic nitrogen provided by plants. The inorganic nitrogen picked up by plants is mostly in the form of nitrate and to some extent ammonium ions.
(d) Biologically nitrogen is fixed by certain free living bacteria, symbiotic bacteria and cyanobacteria. 70% of nitrogen fixation is done by the above micro-organisms. Nitrogen is also fixed by photochemical and electrochemical reactions of the atmosphere. Ammonia is produced industrially by combination of nitrogen with hydrogen. Dead bodies of plants and animals also possess nitrogenous compounds. Both are acted upon by decomposers, which release ammonia and utilise the remaining organic acids for their body building.
(c) The fronds of small floating aquatic fern Azolla contain small pores filled with symbiotic blue-green alage (Anabaena) that actively fix nitrogen. For this ferns are spread in paddy fields, before the rice seedlings are planted, the flooded paddies are covered with aquatic ferns, which fix enough nitrogen to supply the crop as it matures.
(b) Phosphorus deposits in the form of rocks are gradually eroding, releasing phosphates to ecosystems, but much phosphate escapes into the sea, where part of it is deposited in the shallow sediments and part of it is lost to the deep segments. The means of returning phosporus to the cycle may be inadequate to compensate for the loss. Human activities appear to hasten the rate of loss of phosphorus and thus make the phosphorus cycle less cyclic. Thousands of tons of phosphates are also returned to land by marine fishing. One to two million ions of phosphate rock that is mined and used for fertilizer, much of which is washed away and lost.
(b) Unlike most other nutrient or material cycles, the hydrologic cycle involves the movement of a chemical compound water. The hydrologic cycle is one of the most nearly perfect cyclical processes. i.e., the cycle rotates in hydrosphere, lithosphere and atmosphere efficiently. The cycling of water in the atmosphere is a fairly rapid process, the average residence time being only about 10 days, but possibly less in the humid tropics.
(c) Some bacteria and fungi can change H2S and elemental sulphur to sulphate state (e.g.,Beggiotoa, Thiobacillus, Penicillium, Neurospora). Reverse can also occur (e.g.,Aerobacter, Desulpho vibrio) Leaching Delsulpho vibrio bacteria are ecologically important, because they give SO4 in deep segments and in anoxic waters, such as the Black Sea to H2S gas and precipitation of sulphur take out some sulphur from circulating pool and convert into part of reservoir pool.
(b) The cycling of various naturally occurring elements, including toxic pollutants, is a well-regulated and balanced process but man’s industrial activity often tends to disturb this equilibrium and upset the balance towards greater accumulation and lesser destruction. Human activities also provide newer sources of toxic elements to the environment and such elements, like naturally occurring ones, may pass through the biogeochemical cycle and in turn become accessible to living organisms, e.g., DDT.
(b) Gaseous cycles are quick and take little time to complete beyond the stay of matter in the food chain. Sedimentary cycles are usually very slow. They operate via sea food chain or coastal sprays. A still slow process is the formation of rocks and their exposure.
(c) Water or hydrological cycle is actually made of two overlapping cycles – larger global water cycle and smaller biological water cycle. Global water cycle consists of evaporation and precipitation of water. The smaller biological water cycle involves entry of water into living beings and its return to the physical environment.
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