DAY – 18 (InstaTest-18): Insta 75 Days Revision Plan-2022: Topic – Environment & Ecology, Subject-wise Test 14, Textbook based Test 18 and March 2022 CA

Solution: d

What are the key elements that lead to so much variation in the physical and chemical conditions of different habitats?

The most important ones are temperature, water, light and soil. We must remember that the physico-chemical (abiotic) components alone do not characterize the habitat of an organism completely; the habitat includes biotic components also – pathogens, parasites, predators and competitors – of the organism with which they interact constantly. We assume that over a period of time, the organism had through natural selection, evolved adaptations to optimise its survival and reproduction in its habitat. Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its niche.

Solution: b

In higher plants, seeds and some other vegetative reproductive structures serve as means to tide over periods of stress besides helping in dispersal – they germinate to form new plants under favourable moisture and temperature conditions. They do so by reducing their metabolic activity and going into a state of ‘dormancy’.

In animals, the organism, if unable to migrate, might avoid the stress by escaping in time. The familiar case of bears going into hibernation during winter is an example of escape in time. Some snails and fish go into aestivation to avoid summer–related problems-heat and dessication.

Under unfavourable conditions many zooplankton species in lakes and ponds are known to enter diapause, a stage of suspended development.

Solution: c

Population Interactions

Interspecific interactions arise from the interaction of populations of two different species. They could be beneficial, detrimental or neutral (neither harm nor benefit) to one of the species or both. Assigning a ‘+’ sign for beneficial interaction, ‘-’ sign for detrimental and 0 for neutral interaction, let us look at all the possible outcomes of interspecific interactions

Both the species benefit in mutualism and both lose in competition in their interactions with each other. In both parasitism and predation only one species benefits (parasite and predator, respectively) and the interaction is detrimental to the other species (host and prey, respectively). The interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism. In amensalism on the other hand one species is harmed whereas the other is unaffected. Predation, parasitism and commensalism share a common characteristic– the interacting species live closely together.

Solution: c

Predation: What would happen to all the energy fixed by autotrophic organisms if the community has no animals to eat the plants? You can think of predation as nature’s way of transferring to higher trophic levels the energy fixed by plants. When we think of predator and prey, most probably it is the tiger and the deer that readily come to our mind, but a sparrow eating any seed is no less a predator.

Besides acting as ‘conduits’ for energy transfer across trophic levels, predators play other important roles. They keep prey populations under control. But for predators, prey species could achieve very high population densities and cause ecosystem instability. When certain exotic species are introduced into a geographical area, they become invasive and start spreading fast because the invaded land does not have its natural predators. If a predator is too efficient and overexploits its prey, then the prey might become extinct and following it, the predator will also become extinct for lack of food.

Solution: a

A constant input of solar energy is the basic requirement for any ecosystem to function and sustain. Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of weight (gm–2) or energy (kcal m–2). The rate of biomass production is called productivity. It is expressed in terms of gm–2 yr–1 or (kcal m–2) yr–1 to compare the productivity of different ecosystems. It can be divided into gross primary productivity (GPP) and net primary productivity (NPP). Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilised by plants in respiration. Gross primary productivity minus respiration losses (R), is the net primary productivity (NPP).

Net primary productivity is the available biomass for the consumption to heterotrophs (herbiviores and decomposers).

Secondary productivity is defined as the rate of formation of new organic matter by consumers. Primary productivity depends on the plant species inhabiting a particular area. It also depends on a variety of environmental factors, availability of nutrients and photosynthetic capacity of plants. Therefore, it varies in different types of ecosystems.

Solution: a

You may have heard of the earthworm being referred to as the farmer’s ‘friend’. This is so because they help in the breakdown of complex organic matter as well as in loosening of the soil. Similarly, decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients and the process is called decomposition. Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute detritus, which is the raw material for decomposition. The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification and mineralisation.

Detritivores (e.g., earthworm) break down detritus into smaller particles. This process is called fragmentation.

By the process of leaching, water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.

Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as catabolism. 

It is important to note that all the above steps in decomposition operate simultaneously on the detritus (Figure 14.1). Humification and mineralisation occur during decomposition in the soil. Humification leads to accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. Being colloidal in nature it serves as a reservoir of nutrients. The humus is further degraded by some microbes and release of inorganic nutrients occur by the process known as mineralisation.

Solution: b

Except for the deep-sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth. Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR). We know that plants and photosynthetic bacteria (autotrophs), fix Sun’s radiant energy to make food from simple inorganic materials. Plants capture only 2-10 per cent of the PAR and this small amount of energy sustains the entire living world.

So, it is very important to know how the solar energy captured by plants flows through different organisms of an ecosystem. All organisms are dependent for their food on producers, either directly or indirectly.

Further, ecosystems are not exempt from the Second Law of thermodynamics. They need a constant supply of energy to synthesize the molecules they require, to counteract the universal tendency toward increasing disorderliness.

The green plants in the ecosystem are called producers. In a terrestrial ecosystem, major producers are herbaceous and woody plants. Likewise, producers in an aquatic ecosystem are various species like phytoplankton, algae and higher plants.

Each trophic level has a certain mass of living material at a particular time called as the standing crop. The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area. The biomass of a species is expressed in terms of fresh or dry weight. Measurement of biomass in terms of dry weight is more accurate.

Solution: c

In most ecosystems, all the pyramids, of number, of energy and biomass are upright, i.e., producers are more in number and biomass than the herbivores, and herbivores are more in number and biomass than the carnivores. Also, energy at a lower trophic level is always more than at a higher level.

There are exceptions to this generalization: If you were to count the number of insects feeding on a big tree what kind of pyramid would you get? Now add an estimate of the number of small birds depending on the insects, as also the number of larger birds eating the smaller. Draw the shape you would get. 

The pyramid of biomass in sea is generally inverted because the biomass of fishes far exceeds that of phytoplankton. 

Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step. Each bar in the energy pyramid indicates the amount of energy present at each trophic level in a given time or annually per unit area.

The number of trophic levels in the grazing food chain is restricted as the transfer of energy follows 10 per cent law – only 10 per cent of the energy is transferred to each trophic level from the lower trophic level.

Solution: b

Succession of Plants

Based on the nature of the habitat – whether it is water (or very wet areas) or it is on very dry areas – succession of plants is called hydrarch or xerarch, respectively. Hydrarch succession takes place in wet areas and the successional series progress from hydric to the mesic conditions.

As against this, xerarch succession takes place in dry areas and the series progress from xeric to mesic conditions. Hence, both hydrarch and xerarch successions lead to medium water conditions (mesic) – neither too dry (xeric) nor too wet (hydric).

The species that invade a bare area are called pioneer species. In primary succession on rocks these are usually lichens which are able to secrete acids to dissolve rock, helping in weathering and soil formation. These later pave way to some very small plants like bryophytes, which are able to take hold in the small amount of soil. They are, with time, succeeded by higher plants, and after several more stages, ultimately a stable climax forest community is formed. The climax community remains stable as long as the environment remains unchanged. With time the xerophytic habitat gets converted into a mesophytic one.

Another important fact is to understand that all succession whether taking place in water or on land, proceeds to a similar climax community – the mesic.

Solution: d

What is so special about tropics that might account for their greater biological diversity? Ecologists and evolutionary biologists have proposed various hypotheses; some important ones are

(a) Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification, 

(b) Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialisation and lead to a greater species diversity and 

(c) There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.

Solution: c)

Justification: The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls on their leaves and convert it into food energy.

When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment, some amount goes into digestion and in doing work and the rest goes towards growth and reproduction.

An average of 10% of the food eaten is turned into its own body and made available for the next level of consumers.

Since each higher trophic level receives only a fraction of energy of the lower trophic levels, the energy pyramid is narrow at the top. So, A is correct.

But, generally (barring some aquatic ecosystems) lower trophic levels have higher biomass as compared to the higher trophic levels. So, R is incorrect. Moreover, even if this were to be so, it doesn’t explain A.

Q Source: Basics: Energy transfer in ecossytems

Solution: a)

Justification & Learning: There are many plants in which parts like the root, stem and leaves develop into new plants under appropriate conditions.

• Unlike in most animals, plants can indeed use such a mode for reproduction. This property of vegetative propagation is used in methods such as layering or grafting to grow many plants like sugarcane, roses, or grapes for agricultural purposes.
• Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds. Such methods also make possible the propagation of plants such as banana, orange, rose and jasmine that have lost the capacity to produce seeds. So, 1 is correct.
• Another advantage of vegetative propagation is that all plants produced are genetically similar enough to the parent plant to have all its characteristics. So, 2 is wrong.

Q Source: 12th Biology NCERT

Solution: c

Justification: Phytoplankton are the foundation of the aquatic food web, the primary producers

Zoo plankton feed on phytoplankton and play a vital role in food web of the food chain, nutrient recycling, and in transfer of organic matter from primary producers to secondary consumers like fishes.

Their role in the carbon cycle is quite different from that of trees and other land plants, which absorb CO2 and serve as a storehouse, or “sink”, of carbon.

Instead, ocean life absorbs CO2 during photosynthesis and, while most of the gas escapes within about a year, some of it is transported down into the deep ocean via dead plants, body parts, faeces, and other sinking materials.

The CO2 is then released into the water as the materials decay, and most of it becomes absorbed in the seawater by combining chemically with water molecules (H2O).

Q Source: AR: ICSE 10th Environmental Studies

Solution: b

Justification: Statement 1:  Nitrous oxide emissions occur naturally through many sources associated with the nitrogen cycle, which is the natural circulation of nitrogen among the atmosphere, plants, animals, and microorganisms that live in soil and water.

Statement 2:  Nitrous oxide is actually removed from the atmosphere when it is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions. So, 2 is wrong.

Statement 3:  A natural source of nitrogen oxides occurs from a lightning stroke. The very high temperature in the vicinity of a lightning bolt causes the gases oxygen and nitrogen in the air to react to form nitric oxide. The nitric oxide very quickly reacts with more oxygen to form nitrogen dioxide.

Q Source: ICSE 10th Environmental Studies

Solution: d

Learning: Ecosystem is the groups of organisms from all biological domains in conjunction with the physical (abiotic) environment.

Biome is the continental scale (climatically and geographically contiguous areas with similar climatic conditions) grouping of ecosystems.

Biosphere or Ecosphere is all life plus the physical (abiotic) environment.

Q Source: Basics: Ecology

Solution: d

Solution: c

WHO launched a comprehensive plan to eliminate industrially-produced artificial trans fats from the global food supply by 2023 called REPLACE.

FSSAI, Ministry of Health and Family Welfare, is working for the elimination of industrially produced trans-fat in the ‘food supply’ in India by the year 2022.

Solution: c

The Berne Convention for the Protection of Literary and Artistic Works, usually known as the Berne Convention, is an international agreement governing copyright, which was first accepted in Berne, Switzerland, in 1886. The Berne Convention has 179 contracting parties, most of which are parties to the Paris Act of 1971.

The Berne Convention formally mandated several aspects of modern copyright law; it introduced the concept that a copyright exists the moment a work is “fixed”, rather than requiring registration. It also enforces a requirement that countries recognize copyrights held by the citizens of all other parties to the convention.

Solution: b

The AMOC is a large system of ocean currents. It is the Atlantic branch of the ocean conveyor belt or Thermohaline circulation (THC) and distributes heat and nutrients throughout the world’s ocean basins.

Two main features of the AMOC:

• • Flow of warm, salty water in the upper layers of the ocean northwards from the Gulf of Mexico (Orange line). This is made up of the “Gulf Stream” to the south and the “North Atlantic Current” further north.
  • Cooling of water in the high latitudes of the Atlantic makes the water denser. This denser water then sinks and returns southwards towards tropics and then to the South Atlantic as a bottom current (blue line). From there it is distributed to all ocean basins via the Antarctic circumpolar current

Solution: d

Solution : b

The MSP is the rate at which the government purchases crops from farmers, and is based on a calculation of at least one-and-a-half times the cost of production incurred by the farmers.

The MSP is fixed twice a year on the recommendations of the Commission for Agricultural Costs and Prices (CACP)

The Commission for Agricultural Costs & Prices (CACP) is an attached office of the Ministry of Agriculture and Farmers Welfare, Government of India

Solution : b

Mutual Funds are not part of collective investment schemes

Category I AIF:

• Venture capital funds (Including Angel Funds)
• SME Funds
• Social Venture Funds
• Infrastructure funds
• Category II AIF
• Category III AIF

Solution : a

under new guidelines, the exemption limit has been increased to companies with a turnover of less than Rs 100 crores and that are less than ten years old.

“Angel investor” means any person who proposes to invest in an angel fund and satisfies one of the following conditions, namely,

(a) an individual investor who has net tangible assets of at least two crore

rupees excluding value of his principal residence, and who:

(i) has early stage investment experience, or

(ii) has experience as a serial entrepreneur, or

(iii) is a senior management professional with at least ten years of Experience;

Solution : b

It  is a nationwide placement-linked skill training program funded by the Ministry of Rural Development (MoRD).

It is a part National Rural Livelihood Mission uniquely aimed at rural poor youth between 15 and 35 years of age,with the purpose to create income diversity in poor families

Solution : d

WPI, not CPI, is used to index inflation-linked bonds at the moment

Both the principal and the coupon payment will be protected from inflation.

IIBInflation-indexed bonds were announced in the 2013 budget.s are classified as government securities

Solution : b

Explanation: The first paragraph clearly indicates that Black Money Act is for retrieving the unaccounted illegal income.

Solution : d

Solution : a

N = H.C.F. of (4665 – 1305), (6905 – 4665) and (6905 – 1305)
= H.C.F. of 3360, 2240 and 5600 = 1120.
Sum of digits in N = ( 1 + 1 + 2 + 0 ) = 4

Solution : c

Greatest number of 4-digits is 9999.
L.C.M. of 15, 25, 40 and 75 is 600.
On dividing 9999 by 600, the remainder is 399.
Required number (9999 – 399) = 9600.

Solution : d

L.C.M. of 252, 308 and 198 = 2772.

So, A, B and C will again meet at the starting point in 2772 sec. i.e., 46 min. 12 sec.