Sarita Aggarwal solutions for Biology [English] Class 12 ISC chapter 18 - Ecosystem [Latest edition]

Which of the following is an abiotic component of the ecosystem?

Of the incoming solar energy which percentage is reflected back into space?

Total energy stored by green plants is called ______.

Which of the following process helps in nutrient conservation?

What fraction of assimilated energy is used in respiration by the herbivore?

Which of the following is not a part of detritus?

Detritus food chain begins with ______.

The decomposition process does not involve ______.

Percentage energy (of total incident radiation) captured by photosynthetic process is ______.

A food chain always starts with ______.

Which of the following can explain the energy stored in a food chain?

What fraction of assimilated energy is used in respiration by the herbivore?

What fraction of herbivore energy is available to the next trophic level of carnivores?

Which pyramid is always upright, can never be inverted?

Which one of the following has the sedimentary nutrient cycle?

Which of the following is a free living nitrogen fixing bacteria present in soil?

Azospirillum is an example of ______.

Ammonifying bacteria convert ______.

Denitrifying bacteria convert ______.

Atmospheric nitrogen can be fixed by ______.

Main reservoir of phosphorus is ______.

Absorption of phosphorus by higher plants is promoted by the presence of ______.

Which of the following are pioneer organisms of primary succession on a xerach?

The terminal stage of succession is represented by ______.

In a succession in hydrarch, the reed-swamp stage comes after ______.

The succession occurring in water bodies is called ______.

The pyramid of ______ is always upright.

Inverted pyramid is generally found in ______.

In oceans, the productivity is generally limited by ______.

Humus serves as a reservoir of ______.

Dead plant parts and animal remains are called ______.

In deep aquatic ecosystems, floating plants called ______ are the major autotrophs.

The nutrients present in the soil at any given time is referred as its ______.

Only about ______ % of PAR is utilised for photosynthesis.

Nitrosomonas converts ______ to ______.

Nitrates are converted to free molecular nitrogen by ______ a denitrying bacteria.

State whether the following is true or false.

Both abiotic and biotic factors form the structural components of an ecosystem.

State whether the following is true or false.

Zooplanktons and free-swimming organisms are the decomposers in a pond.

State whether the following is true or false.

Net primary productivity is equal to gross primary productivity plus the energy spent on respiration.

State whether the following is true or false.

Decomposition involves fragmentation, leaching and catabolism.

State whether the following is true or false.

Humification is a slow process and is followed by mineralisation.

State whether the following is true or false.

In an ecosystem energy flows in a single direction only from consumers to producers.

State whether the following is true or false.

In a food chain only 10% of energy is transferred to the next trophic level.

State whether the following is true or false.

In a tree-dominated ecosystem, the pyramid of numbers could be an inverted pyramid.

State whether the following is true or false.

In a primary succession, lichens are the pioneer organisms that invade a bare rock.

State whether the following is true or false.

Carbon present as carbonates in producers and consumers, acts as a reservoir of carbon in nature.

Match the following.

Answer the following in one or two words.

A term for man-made ecosystems.

Answer the following in one or two words.

Animals that feed on herbivores.

Answer the following in one or two words.

The net stored energy in green plants after meeting the cost of respiration.

Answer the following in one or two words.

Detritus feeding invertebrates like earthworms.

Answer the following in one or two words.

Pyramid that represents the 'standing crop' of organisms at each trophic level at a particular time.

Answer the following in one or two words.

Conversion of nitrates back to free molecular nitrogen.

Answer the following in one or two words.

A process that leads to accumulation of humus.

Answer the following in one or two words.

Another term for above ground detritus.

Answer the following in one or two words.

Nutrient cycle whose reservoir exists in the earth's crust.

Answer the following in one or two words.

Ecological succession that occurs on a previously unoccupied site like a volcano.

Assertion (A): Despite occupying about 70% of the earth's surface, Oceans are a low productivity ecosystem.

Reason (R): In aquatic ecosystems, productivity is limited by light that decreases with increasing water depth.

Assertion (A): A network of food chains, existing together in an ecosystem is a form of food web.

Reason (R): An animal like tiger, a carnivore, cannot be a part of food web.

Assertion (A): Pyramid of energy may be upright or inverted.

Reason (R): Only 20% of energy goes to next trophic level.

Assertion (A): In a marine aquatic ecosystem, at any given time, the biomass of phytoplanktons (producers) is lower than the biomass of zooplanktons (primary consumers).

Reason (R): Phytoplanktons are consumed almost as rapidly as they are formed and thus have shorter life spans.

Assertion (A): A lake can undergo ecological succession and become a forest over a period of time.

Reason (R): A bare rock can become a forest through ecological succession.

Assertion (A): Secondary succession always involves a predictable species sequence and ends up with the same climax community as existed prior to the disturbance.

Reason (R): A pond can never be considered as a self-sustained ecosystem, as it lacks the structural and functional components of an ecosystem.

Assertion (A): The recycling of carbon is essentially a self-regulating feedback system in nature.

Reason (R): In the atmosphere the reservoir pool of carbon consists of free CO₂.

Assertion (A): Gross primary productivity (GP) refers to the total energy stored by the green plants.

Reason (R): GP includes the energy a plant would spend on respiration.

Assertion (A): The total number of species in an ecotone is more than those present in an adjoining area.

Reason (R): Ecotone is a sharp transition zone between two or more diverse communities.

Assertion (A): Mosses and lichens are said to form the pioneer community in xerarch succession.

Reason (R): It is because during the course of succession these species get established later.

Read the sources given and answer any four from the questions given below:

1. In the above pyramid of biomass, which trophic level represents the more biomass than primary carnivores?
   1. producers and carnivores
   2. herbivores and secondary carnivores
   3. producers and herbivores
   4. both (a) and (c)
2. In an aquatic ecosystem the pyramid of biomass is
   1. upright
   2. triangular
   3. inverted
   4. squarish
3. The biomass of zooplanktons in an aquatic ecosystem is
   1. more than phytoplanktons
   2. less than phytoplanktons
   3. more than large fish in water
   4. both (b) and (c)
4. The pyramid of biomass of an aquatic system is inverted, where the producers are algae and phytoplanktons because
   1. short life span and rapid increasing rate of zooplanktons than phytoplanktons
   2. short life span and rapid increasing rate of phytoplanktons than zooplanktons
   3. biomass of algae and phytoplanktons is maximum
   4. biomass of zooplanktons is more than that of phytoplanktons
5. In the trophic levels the second trophic level is always occupied by
   1. carnivores
   2. herbivores
   3. producers
   4. decomposers