Which class of animals constitute the largest biomass?

Which class of animals constitute the largest biomass?

We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

I found here that species-wise it is cow. But, collectively, insects may exceed even mammals. So, which class of animals constitutes the largest biomass?

Following from MarchHo's comment, I have not been able to find class-specific (in the formal sense) estimates, but if you meant 'class' in an informal sense, the following may be useful.

A nice infographic covering the relative biomass of all land mammals is here, and a full table for species groups (at the level of domesticated vertebrates, invertebrates, etc) is here (reproduced below).

Short answer: amongst animals, invertebrates are where the mass is.

NCERT Solutions for Class 12th: Ch 14 Ecosystem Biology

(d) Decomposers
Decomposers include micro-organisms such as bacteria and fungi. They form the largest population in a food chain and obtain nutrients by breaking down the remains of dead plants and animals

3. The second trophic level in a lake is
(a) Phytoplankton
(b) Zooplankton
(c) Benthos
(d) Fishes

(b) Zooplankton
Zooplankton are primary consumers in aquatic food chains that feed upon phytoplankton. Therefore, they are present at the second trophic level in a lake.

4. Secondary producers are
(a) Herbivores
(b) Producers
(c) Carnivores
(d) None of the above

(d) None of the above
Plants are the only producers. Thus, they are called primary producers. There are no other producers in a food chain.

5. What is the percentage of photosynthetically active radiation (PAR) in the incident solar radiation?
(a) 100%
(b) 50 %
(c) 1-5%
(d) 2-10%

(b) 50%
Out of total incident solar radiation, about fifty percent of it forms photosynthetically active radiation (PAR).

6. Distinguish between
(a) Grazing food chain and detritus food chain
(b) Production and decomposition
(c) Upright and inverted pyramid
(d) Food chain and Food web
(e) Litter and detritus
(f) Primary and secondary productivity

(a) Grazing food chain and detritus food chain

Grazing food chain Detritus food chain
In this food chain, energy is derived from the Sun. In this food chain, energy comes from organic matter (or detritus) generated in trophic levels of the grazing food chain.
It begins with producers, present at the first trophic level. It begins with detritus such as dead bodies of animals or fallen leaves, which are then eaten by decomposers or detritivores.
This food chain is usually large. It is usually smaller as compared to the grazing food chain.

(b) Production and decomposition

Production Decomposition
It is the rate of producing organic matter (food) by producers. It is the process of breaking down of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into organic raw materials.
It depends on the photosynthetic capacity of the producers. It occurs with the help of decomposers.
Sunlight is required by plants for primary production. Sunlight is not required for decomposition by decomposers.

(c) Upright and inverted pyramid

Upright pyramid Inverted pyramid
The pyramid of energy is always upright. The pyramid of biomass and the pyramid of numbers can be inverted.
The number and biomass of organisms in the producer level of an ecosystem is the highest, which keeps on decreasing at each trophic level in a food chain. The number and biomass of organisms in the producer level of an ecosystem is the lowest, which keeps on increasing at each tropic level. Light is not required for decomposition by decomposers

(d) Food chain and Food web

Food chain Food web
Food chain is single pathway of energy transfer from upper to lower. Food web is made of several interconnecting pathways.
One individual occupies one trophic level at a time. One individual occupies many trophic level at a time.
It decreases stability of the ecological system and less adaptive. It increases stability of the ecological system and more adaptive.

(e) Litter and detritus

Litter Detritus
Litter contains all kinds of waste materials above the surface of the earth. Detritus contains dead animals and plants below and above the surface of the earth.
It contains both biodegradable as well as non-biodegradable wastes. It contains only biodegradable wastes.

(f) Primary and secondary productivity

Primary productivity Secondary productivity
Rate of amount of production of organic matter by producers over a period of time. Rate of amount of production of organic matter by consumers over a period of time.
It is due to photosynthesis. It is due to herbivory and predation.

7. Describe the components of an ecosystem.

An ecosystem is defined as an interacting unit that includes both the biological community as well as the non-living components of an area. The living and the non-living components of an ecosystem interact amongst themselves and function as a unit, which gets evident during the processes of nutrient cycling, energy flow, decomposition, and productivity. There are many ecosystems such as ponds, forests, grasslands, etc.
The two components of an ecosystem are:
(a) Biotic component: It is the living component of an ecosystem that includes biotic factors such as producers, consumers, decomposers, etc. Producers include plants and algae which contain chlorophyll pigment, which helps them carry out the process of photosynthesis in the presence of light. Thus, they are also called converters or transducers. Consumers or heterotrophs are organisms that are directly (primary consumers) or indirectly (secondary and tertiary consumers) dependent on producers for their food. Decomposers include micro-organisms such as bacteria and fungi. They form the largest population in a food chain and obtain nutrients by breaking down the remains of dead plants and animals.
(b) Abiotic component: They are the non-living component of an ecosystem such as light, temperature, water, soil, air, inorganic nutrients, etc.

8. Define ecological pyramids and describe with examples, pyramids of number and biomass.

An ecological pyramid is a graphical representation of various ecological parameters such as the number of individuals present at each trophic level, the amount of energy, or the biomass present at each trophic level. Ecological pyramids represent producers at the base, while the apex represents the top level consumers present in the ecosystem. There are three types of pyramids:
(a) Pyramid of numbers
(b) Pyramid of energy
(c) Pyramid of biomass
Pyramid of numbers: It is a graphical representation of the number of individuals present at each trophic level in a food chain of an ecosystem. The pyramid of numbers can be upright or inverted depending on the number of producers. For example, in a grassland ecosystem, the pyramid of numbers is upright. In this type of a food chain, the number of producers (plants) is followed by the number of herbivores (mice), which in turn is followed by the number of secondary consumers (snakes) and tertiary carnivores (eagles). Hence, the number of individuals at the producer level will be the maximum, while the number of individuals present at top carnivores will be on the other hand, in a parasitic food chain, the pyramid of numbers is inverted. In this type of a food chain, a single tree (producer) provides food to several fruit eating birds, which in turn support several insect species.
Pyramid of energy: An energy pyramid is a graphical model of energy flow in a community. The different levels represent different groups of organisms that might compose a food chain. From the bottom-up, they are as follows: Producers bring energy from nonliving sources into the community.
Pyramid of biomass: A pyramid of biomass is a graphical representation of the total amount of living matter present at each trophic level of an ecosystem. It can be upright or inverted. It is upright in grasslands and forest ecosystems as the amount of biomass present at the producer level is higher than at the top carnivore level. The pyramid of biomass is inverted in a pond ecosystem as the biomass of fishes far exceeds the biomass of zooplankton (upon which they feed).east.

9. What is primary productivity? Give brief description of factors that affect primary productivity.

It is defined as the amount of organic matter or biomass produced by producers per unit area over a period of time.
Primary productivity of an ecosystem depends on the variety of environmental factors such as light, temperature, water, precipitation, etc. It also depends on the availability of nutrients and the availability of plants to carry out photosynthesis.

10. Define decomposition and describe the processes and products of decomposition.

Decomposition is the process that involves the breakdown of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into inorganic raw materials such as carbon dioxide, water, and other nutrients. The various processes involved in decomposition are as follows:
(i) Fragmentation: It is the first step in the process of decomposition. It involves the breakdown of detritus into smaller pieces by the action of detritivores such as earthworms.
(ii) Leaching: It is a process where the water soluble nutrients go down into the soil layers and get locked as unavailable salts.
(iii) Catabolism: It is a process in which bacteria and fungi degrade detritus through various enzymes into smaller pieces.
(iv) Humification: The next step is humification which leads to the formation of a dark-coloured colloidal substance called humus, which acts as reservoir of nutrients for plants.
(v) Mineralization: The humus is further degraded by the action of microbes, which finally leads to the release of inorganic nutrients into the soil. This process of releasing inorganic nutrients from the humus is known as mineralization.
Decomposition produces a dark coloured, nutrient-rich substance called humus. Humus finally degrades and releases inorganic raw materials such as CO2, water, and other nutrient in the soil.

11. Give an account of energy flow in an ecosystem.

12. Write important features of a sedimentary cycle in an ecosystem.

Sedimentary cycles have their reservoirs in the Earth's crust or rocks. Nutrient elements are found in the sediments of the Earth. Elements such as sulphur, phosphorus, potassium, and calcium have sedimentary cycles.
Sedimentary cycles are very slow. They take a long time to complete their circulation and are considered as less perfect cycles. This is because during recycling, nutrient elements may get locked in the reservoir pool, thereby taking a very long time to come out and continue circulation. Thus, it usually goes out of circulation for a long time.

13. Outline salient features of carbon cycling i n an ecosystem.

The carbon cycle is an important gaseous cycle which has its reservoir pool in the atmosphere. All living organisms contain carbon as a major body constituent. Carbon is a fundamental element found in all living forms. All biomolecules such as carbohydrates, lipids, and proteins required for life processes are made of carbon. Carbon is incorporated into living forms through a fundamental process called 'photosynthesis'. Photosynthesis uses sunlight and atmospheric carbon dioxide to produce a carbon compound called 'glucose'. This glucose molecule is utilized by other living organisms. Thus, atmospheric carbon is incorporated in living forms. Now, it is necessary to recycle this absorbed carbon dioxide back into the atmosphere to complete the cycle. There are various processes by which carbon is recycled back into the atmosphere in the form of carbon dioxide gas. The process of respiration breaks down glucose molecules to produce carbon dioxide gas. The process of decomposition also releases carbon dioxide from dead bodies of plants and animals into the atmosphere. Combustion of fuels, industrialization, deforestation, volcanic eruptions, and forest fires act as other major sources of carbon dioxide.

How Are Animals Classified?

Biological scientists estimate that collectively the earth’s 5 to 40 million species of organisms (depending on the estimate you choose to believe) make up a total of some two trillion tons of living matter, or biomass. The plants comprise well over 90 percent of the biomass. The animals, the focus of this article, comprise only a small percentage of the biomass, but they account for the majority of species.

In accordance with the Linnaeus method, scientists classify the animals, as they do the plants, on the basis of shared physical characteristics. They place them in a hierarchy of groupings, beginning with the kingdom animalia and proceeding through phyla, classes, orders, families, genera and species. The animal kingdom, similar to the plant kingdom, comprises groups of phyla a phylum (singular for phyla) includes groups of classes a class, groups of orders an order, groups of families a family, groups of genera and a genus (singular of genera), groups of species. As established by Linnaeus, the scientists call an animal species, as they do a plant species, by the name of the genus, capitalized, and the species, uncapitalized. So far, the scientists have classified and named something over a million animal species. Without doubt, they have millions more to go.

Taxonomists, biological scientists who specialize in classifying and naming the living organisms, group the multicellular, independently mobile organisms that eat other organisms into the kingdom of animalia. The taxonomists recognize that the animals, unlike the plants, possess specialized tissues that may be organized into even more specialized organs, and they recognize that most animals, especially the more evolutionarily advanced species, have &ldquobilateral symmetry,&rdquo which means that the right and left sides are essentially mirror images of each other. Critically, especially in the desert, animals, unlike plants, often utilize their mobility to seek refuge from environmental stresses such as intense heat and prolonged drought.

Animal Populations

Worldwide, the animal population consists of species numbering somewhere in the millions. The largest, the blue whale, may exceed 100 feet in length and 150 tons in weight. The smallest known animals, for instance, a parasitic wasp that taxonomists have named Dicopomorpha echmepterygis, measure no more than a few thousands of an inch in length.

The most abundant and diverse animal communities occupy earth&rsquos most biologically productive regions, for example, the tropical rainforests, where the species of living organisms probably number in the millions. Conversely, the least abundant and diverse animal communities live in the least biologically productive regions, in particular, deserts like those of our Southwest, where the species of living organisms likely number in the tens to hundreds of thousands.

The biological richness of a tropical rainforest contrasts sharply with the biological impoverishment of our deserts. The net biological productivity of a typical area in a tropical rainforest may exceed that of a comparable area in our desert lands by a factor of 40 to 50 times, according to the Physical Internet site. Moreover, according to the Tropical Rainforest Biome Internet site, &ldquoScientists believe that the tropical rainforests of the world might hold up to ninety percent of the plant and animal species on earth.&rdquo In a paper called &ldquoTropical Biomes,&rdquo Professor Ralph E. Taggart, Michigan State University, said &ldquoThe total biological diversity of only a few square kilometers of rich tropical rainforest can exceed that of entire regions in the temperate zone. Most of the plants and animals of the world are found in the complex mosaic of natural communities that make up this biome.&rdquo Nevertheless, our deserts host a diverse and highly adapted community of animals.

The Animal Community

Taxonomists typically divide the animal kingdom into two &ldquosubkingdoms,&rdquo which include the invertebrates (animals without backbones) and vertebrates (animals with backbones). As with the plants, taxonomists turn the subsequent animal groupings and classifications, from phyla through genera, into a churning landscape that is simply a part of the scientific process. Depending on their academic roots and research, they divide and re-divide the animal community in many different ways, frequently regrouping, reclassifying and even re-naming species as they go. Some, called &ldquolumpers,&rdquo identify species as belonging to the same group even though there may be small differences. Other scientists, called &ldquosplitters,&rdquo identify the same species as belonging in distinct groups because of the same small differences. The lumpers produce a relatively simple taxonomy, the splitters, a far more complex taxonomy.

Classifying an Invertebrate

In our deserts, the invertebrate subkingdom includes phyla such as arthropods (insects, centipedes, spiders, scorpions, desert shrimp and many others), mollusks (snails) and annelids (earthworms). In the desert, as well as across the world, arthropods, measured in terms of abundance and diversity, rank at the top of all the animal phyla. An elegant insect, the monarch butterfly, serves as example of how the classification system works for the invertebrates.

At the phylum level, the monarch belongs to the arthropods, which share several physical characteristics. According to Barbara Terkanian, &ldquoA Vertebrate Looks At Arthropods,&rdquo A Natural History of the Sonoran Desert, the arthropods have jointed legs, and they have external skeletons, or exoskeletal material, that includes &ldquoeyes, mouthparts, antennae, body, legs, the fore and hind sections of the digestive tract, and some respiratory surfaces. Regions of flexible, unhardened exoskeleton serve as joints between neighboring segments.&rdquo The body cavity contains the digestive, circulatory, nervous and reproductive systems.

At the class level, the monarch has membership in the insect group, which comprises the overwhelming majority of the arthropods. The insects have several distinguishing physical characteristics, including three-part bodies, six legs (three pairs), compound eyes and two antennae. The class, called Insecta, includes three subclasses, according to Kendall Bioresearch Services Internet site. The first consists of insects that have never had wings throughout their evolutionary history. The young resemble the adults. The second subclass consists of insects that have wings at present or had them at some point during their evolutionary history. The nymphs resemble the adults. The third subclass consists of insects that have wings at present or had them at some point during their evolutionary history. The young take the form of larvae that change into adults during a non-feeding metamorphosis. The first subclass consists of four orders, including, for example, bristletails and springs tails. The second subclass has 16 orders, including, for instance, dragonflies crickets, grasshoppers and locusts termites and sucking lice. The third subclass has nine orders, comprising insects such as beetles fleas bees, wasps and ants and the butterflies and moths.

At the order level, the monarch belongs to butterflies and moths, called Lepidoptera, which rank high among the most intriguing and conspicuous insect orders in the Southwest. They have two pairs of membranous, scaled and often brightly colored wings. Typically they have large eyes, long antennae and a long sucking tube (which the insect coils beneath its head when not feeding). The larvae, or caterpillars, all have silk glands that they use for spinning their cocoons. Their order contains well over 100 families.

At the family level, the monarch is the star of the milkweed butterflies, called Danaidae, which are among the best known in our deserts (as well as across the country). The milkweed butterflies usually have goldish wings trimmed in black, according to Donald J. Borror and Richard E. White, A Field Guide to the Insects of America North of Mexico. Their caterpillars feed on milkweed leaves, which invest both larvae and adults with a bitter and toxic taste that discourages predators.

At the genera level, the monarch is one of a mere handful of closely related species collectively called Dannaus. These species show apparently common evolutionary origins in their caterpillars, which share similar spots and smooth skin texture on their abdomens, according to David Munro, &ldquoThe Biogeography of the monarch Butterfly,&rdquo San Francisco State University, Department of Geology, fall 1999.

At the species level, the monarch is called plexippus. It is, says Munro, &ldquoa medium sized butterfly, measuring about 3 inches from wingtip to wingtip. Its body is about one inch long. Its four wings are generally a field of yellow, orange or gold, with veins of black running through them. A band of black, thickest at the front, rings the wings, and the body is black as well. This black band is usually speckled with white spots, larger at the front and smaller at the back.&rdquo

The monarch, the aristocrat of the butterfly and moth world, bears the scientific name of Dannaus plexippus. In summary, it fits into the Linnaeus classification scheme as follows:

Question 1.
Which of the following is considered as pioneer community in xerarch ?
(a) Annual herbs
(b) Perennial herbs
(c) Shrubs
(d) Lichens
(d) Lichens

Question 2.
Correct sequence of stages of succession on a bare rock is
(a) Lichens → Mosses → Grasses → Shrubs → Trees
(b) Trees → Shrubs → Lichens → Mosses → Grasses
(c) Mosses → Shrubs → Trees → Lichens → Grasses
(d) Mosses → Lichens → Grasses → Shrubs → Trees.
(a) Lichens → Mosses → Grasses → Shrubs → Trees

Question 3.
In lithosere, foliose lichens make the conditions favourable for the growth of
(a) crustose lichens
(b) mosses
(c) annual grasses
(d) perennial grasses.
(b) mosses

Question 4.
The correct sequence of plants in a hydrosere is
(a) Volvox → Hydrilla → Pistia → Scirpus→ Carex → Quercus
(b) Pistia → Volvox → Scirpus → Hydrilla → Quercus → Carex
(c) Quercus → Carex → Volvox → Hydrilla → Pistia → Scirpus
(d) Quercus → Carex → Scirpus → Pistia → Hydrilla → Volvox.
(a) Volvox → Hydrilla → Pistia → Scirpus→ Carex → Quercus

Question 5.
The second stage of hydrosere is occupied by plants like
(a) Azolla
(b) Typha
(c) Carex
(d) Vallisneria.
(d) Vallisneria.

Question 6.
An ecosystem which can be easily damaged but can recover after some time if damaging effect stops, will be having
(a) low stability and high resilience
(b) high stability and low resilience
(c) low stability and low resilience
(d) high stability and high resilience.
(a) low stability and high resilience

Question 7.
Which one of the following is not a gaseous biogeochemical cycle in ecosystem ?
(a) Water cycle
(b) phosphorus cycle
(c) Nitrogen cycle
(d) Carbon cycle
(b) phosphorus cycle

Question 8.
The function of reservoir pool is to meet with the deficit of nutrient that occurs due to
(a) imbalance in rate of efflux and influx of nutrients
(b) only efflux of nutrients
(c) ceased nutrient cycle
(d) none of these.
(a) imbalance in rate of efflux and influx of nutrients

Question 9.
About 71 % of total global carbon is found in
(a) Oceans
(b) Forests
(c) grasslands
(d) agroecosystems.
(a) Oceans

Question 10.
What percentage of total global carbon is atmospheric carbon ?
(a) 0.03%
(b) 1%
(c) 10%
(d) 30%
(b) 1%

Question 11.
Climax community is in a state of
(a) non-equilibrium
(b) equilibrium
(c) disorder
(d) constant change.
(b) equilibrium

Question 12.
Among the following biogeochemical cycles, which one does not have losses due to respiration ?
(a) Phosphorus
(b) Nitrogen
(c) Sulphur
(d) All of the above
(d) All of the above

Question 13.
The reservoir for the gaseous type of biogeochemical cycle exists in
(a) stratosphere
(b) atmosphere
(c) ionosphere
(d) lithosphere.
(b) atmosphere

Question 14.
The zone at the edge of a lake or ocean which is alternatively exposed to air and immersed in water is called
(a) pelagic zone
(b) benthic zone
(c) lentic zone
(d) littoral zone.
(d) littoral zone.

Question 15.
Edaphic factor refers to
(a) water
(b) soil
(c) relative humidity
(d) altitude.
(b) soil

Question 16.
Term ‘ecosystem’ was coined by
(a) Odum
(b) Tansley
(c) Lindeman
(d) Elton.
(b) Tansley

Question 17.
Which of the following pairs is not correct ?
(a) E. Haeckel – Coined the term ‘Ecology’
(b) Tansley – Coined the term ‘Ecosystem’
(c) R. Mishra – Father of Indian Ecology
(d) None of these
(d) None of these

Question 18.
Vertical distribution of different species occupying different levels in dense vegetation is called
(a) stratification
(b) species composition
(c) standing crop
(d) trophic structure
(a) stratification

Question 19.
Which one of the following aspects is not a component of functional unit of ecosystem ?
(a) Productivity
(b) Decomposition
(c) Energy flow
(d) Ecological pyramids
(d) Ecological pyramids

Question 20.
The movement of energy from lower to higher trophic level is
(a) always unidirectional
(b) sometimes unidirectional
(c) always bidirectional
(d) undeterminable.
(a) always unidirectional

Question 21.
The rate of conversion of light energy into chemical energy of organic molecules in an ecosystem is
(a) net primary productivity
(b) gross primary productivity
(c) secondary productivity
(d) gross secondary productivity.
(b) gross primary productivity

Question 22.
The biomass available for consumption by the herbivores and the decomposers is called
(a) net primary productivity
(b) secondary productivity
(c) standing crop
(d) gross primary productivity
(a) net primary productivity

Question 23.
________ is the rate of production of organic matter by
(a) Primary productivity
(b) Secondary productivity
(c) Net primary productivity
(d) Gross primary productivity
(b) Secondary productivity

Question 24.
The rate of formation of new organic matter by rabbit in a g rassland, is called
(a) net productivity
(b) secondary productivity
(c) net primary productivity
(d) gross primary productivity
(b) secondary productivity

Question 25.
Primary productivity depends upon
(a) light and temperature
(b) water and nutrients
(c) photosynthetic capacity of producers
(d) all of these.
(d) all of these.

Question 26.
Which of the following processes does not contribute to the C02 pool in the atmosphere ?
(a) Respiration by producers
(b) photosynthesis by producers
(c) Respiration by consumers
(d) Decomposition by decomposers
(b) photosynthesis by producers

Question 27.
Major source of sulphur is
(a) oceans
(b) land
(c) rocks
(d) lakes.
(c) rocks

Question 28.
The ecosystem services include
(a) maintenance of biodiversity
(b) pollination of crop
(c) spiritual, cultural and aesthetic values
(d) all of these.
(d) all of these.

Question 29.
Out of the total proposed cost of various ecosystem services, cost of climate regulations and habitat for wildlife are
(a) 50%
(b) 10%
(c) 6%
(d) 25%
(c) 6%

Question 30.
The process of mineralisation by microorganisms helps in the release of
(a) inorganic nutrients from humus
(b) both organic and inorganic nutrients from detritus
(c) organic nutrients from humus
(d) inorganic nutrients from detritus and formation of humus.
(a) inorganic nutrients from humus

Question 31.
An inverted pyramid of biomass can be found in which ecosystem ?
(a) Forest
(b) Marine
(c) Grassland
(d) Tundra
(b) Marine

Question 32.
Which of the following is not a producer ?
(a) Spirogyra
(b) Agaricus
(c) Volvox
(d) Nostoc
(b) Agaricus

Question 33.
Which of the following ecosystems is most productive in terms of net primary production ?
(a) Deserts
(b) Tropical rainforests
(c) Oceans
(d) Estuaries
(b) Tropical rainforests

Question 34.
Among the following, where do you think the process of decomposition would be the fastest ?
(a) Tropical rainforest
(b) Antarctic
(c) Dry arid region
(d) Alpine region
(a) Tropical rainforest

Question 35.
During the process of ecological succession, the changes that take place in communities are
(a) orderly and sequential
(b) random
(c) very quick
(d) not influenced by the physical environment.
(a) orderly and sequential

Question 36.
The annual net primary productivity of the whole biosphere is approximately.
(a) 150 billion tons
(b) 160 billion tons
(c) 170 billion tons
(d) 180 billion tons.
(c) 170 billion tons

Question 37.
Which one of the following exhibits least productivity ?
(a) Salty marshes
(b) Grasslands
(c) Open oceans
(d) Coral reefs
(c) Open oceans

Question 38.
Which one of the following is the most productive ecosystem ?
(a) Temperate forest
(b) Grassland
(c) Desert
(d) Tropical rainforest
(d) Tropical rainforest

Question 39.
During the process of decomposition
(a) CO2 is consumed and O2 is released
(b) O2 is consumed and CO2 is released
(c) CO2 is consumed and H2O is released
(d) none of these.
(b) O2 is consumed and CO2 is released

Question 40.
Rate of decomposition depends upon
(a) chemical composition of detritus
(b) temperature
(c) soil moisture and soil pH
(d) all of these.
(d) all of these.

Question 41.
Decomposers are also called as
(a) transducers
(b) reducers
(c) micro-consumers
(d) both (b) and (c).
(d) both (b) and (c).

Question 42.
The ultimate energy source of all ecosystems is
(a) producers
(b) organic molecules
(c) carbohydrate
(d) solar radiation.
(d) solar radiation.

Question 43.
Percentage of photosynthetically active radiation (PAR) in the incident solar radiation is
(a) 1 – 5%
(b) 2 – 10%
(c) less than 50%
(d) approx. 100%
(c) less than 50%

Question 44.
Percentage of photosynthetically active radiation (PAR) that is captured by plants in synthesis of organic matter is
(a) 50 – 70%
(b) 30 – 40%
(c) 80 – 100%
(d) 2 – 10%
(d) 2 – 10%

Question 45.
Select the incorrect food chain.
(a) Grass → Grasshopper → Frog → Snake → Eagle
(b) Phytoplanktons → Zooplanktons → Small fish → Large fish
(c) Diatoms → Zooplanktons → Small fish
(d) Grass → Frog → Vulture
(d) Grass → Frog → Vulture

Question 46.
If 10 joules of energy is available at the producer level, then amount of energy present at the level of secondary consumers is
(a) 10 J
(b) 1J
(c) 0.1 J
(d) 0.01 J.
(c) 0.1 J

Question 47.
The energy and biomass relationship between the organisms at different trophic levels can better expressed by
(a) food chain
(b) food web
(c) ecological pyramids
(d) energy cycle
(c) ecological pyramids

Question 48.
Which one of the following animals may occupy more than one trophic levels in the same ecosystem at the same time ?
(a) Sparrow
(b) Lion
(c) Goat
(d) Frog
(a) Sparrow

Question 49.
Organisms which are associated with first as well as third trophic level are
(a) macrophytes
(b) phytoplanktons
(c) chemoautotrophs
(d) insectivorous plants.
(d) insectivorous plants.

Question 50.
Mr. X is eating curd/yoghurt. For this food intake in a food chain he should be considered as occupying
(a) First trophic level
(b) second trophic level
(c) third trophic level
(d) fourth trophic level
(c) third trophic level

Question 51.
Primary succession occurs on
(a) area destroyed due to forest fire
(b) newly formed river delta
(c) harvested crop field
(d) all of these.
(b) newly formed river delta

Question 52.
Successions that occur on soils or areas which have recently lost their community are referred to as
(a) primary successions
(b) secondary successions
(c) lithoseres
(d) priseres.
(b) secondary successions

Question 53.
Which one of the following statements is correct for secondary succession ?
(a) It begins on a bare rock.
(b) It occurs on a deforested site.
(c) It follows primary succession.
(d) It is similar to primary succession except that primary succession has a relatively fast pace.
(b) It occurs on a deforested site.

Question 54.
The rate of secondary succession is faster than primary succession because
(a) soil or sediment is already present
(b) water is available in large quantity
(c) climax community is already present
(d) pH of soil is favourable.
(d) pH of soil is favourable.

Question 55.
As the succession proceeds number and types of __________ change.
(a) vegetation
(b) animals
(c) vegetation and animals
(d) vegetation, animals and decomposers
(d) vegetation, animals and decomposers

We hope the given Biology MCQs for Class 12 with Answers Chapter 14 Ecosystem will help you. If you have any query regarding CBSE Class 12 Biology Ecosystem MCQs Pdf, drop a comment below and we will get back to you at the earliest.

Subphylum Crustacea

Crustaceans are the most dominant aquatic arthropods, since the total number of marine crustacean species stands at 67,000, but there are also freshwater and terrestrial crustacean species. Krill, shrimp, lobsters, crabs, and crayfish are examples of crustaceans (Figure 3). Terrestrial species like the wood lice (Armadillidium spp.) (also called pill bugs, rolly pollies, potato bugs, or isopods) are also crustaceans, although the number of non-aquatic species in this subphylum is relatively low.

Figure 3. The (a) crab and (b) shrimp krill are both crustaceans. (credit a: modification of work by William Warby credit b: modification of work by Jon Sullivan)

Crustaceans possess two pairs of antennae, mandibles as mouthparts, and biramous (“two branched”) appendages, which means that their legs are formed in two parts, as distinct from the uniramous (“one branched”) myriapods and hexapods (Figure 4).

Figure 4. Arthropods may have (a) biramous (two-branched) appendages or (b) uniramous (one-branched) appendages. (credit b: modification of work by Nicholas W. Beeson)

Unlike that of the Hexapoda, the head and thorax of most crustaceans is fused to form a cephalothorax (Figure 5), which is covered by a plate called the carapace, thus producing a body structure of two tagma. Crustaceans have a chitinous exoskeleton that is shed by molting whenever the animal increases in size. The exoskeletons of many species are also infused with calcium carbonate, which makes them even stronger than in other arthropods. Crustaceans have an open circulatory system where blood is pumped into the hemocoel by the dorsally located heart. Hemocyanin and hemoglobin are the respiratory pigments present in these animals.

Figure 5. The crayfish is an example of a crustacean. It has a carapace around the cephalothorax and the heart in the dorsal thorax area. (credit: Jane Whitney)

Most crustaceans are dioecious, which means that the sexes are separate. Some species like barnacles may be hermaphrodites. Serial hermaphroditism, where the gonad can switch from producing sperm to ova, may also be seen in some species. Fertilized eggs may be held within the female of the species or may be released in the water. Terrestrial crustaceans seek out damp spaces in their habitats to lay eggs.

Larval stages—nauplius and zoea—are seen in the early development of crustaceans. A cypris larva is also seen in the early development of barnacles (Figure 6). Crustaceans possess a tripartite brain and two compound eyes. Most crustaceans are carnivorous, but herbivorous and detritivorous species are also known. Crustaceans may also be cannibalistic when extremely high populations of these organisms are present.

Figure 6. All crustaceans go through different larval stages. Shown are (a) the nauplius larval stage of a tadpole shrimp, (b) the cypris larval stage of a barnacle, and (c) the zoea larval stage of a green crab. (credit a: modification of work by USGS credit b: modification of work by Mª. C. Mingorance Rodríguez credit c: modification of work by B. Kimmel based on original work by Ernst Haeckel)

Birds are animals that have feathers and that are born out of hard-shelled eggs.

Some people think that what makes an animal a bird is its wings. Bats have wings. Flies have wings. Bats and flies are not birds. So what makes an animal a bird?

All birds have feathers and birds are the only animals that do. The feathers on a bird’s wings and tail overlap. Because they overlap, the feathers catch and hold the air. This helps the bird to fly, steer itself and land.


Fish are vertebrates that live in water and have gills, scales and fins on their body. There are a lot of different fish and many of them look very odd indeed. There are blind fish, fish with noses like elphants, fish that shoot down passing bugs with a stream of water and even fish that crawl onto land and hop about!



Our editors will review what you’ve submitted and determine whether to revise the article.

Biomass, the weight or total quantity of living organisms of one animal or plant species ( species biomass) or of all the species in a community (community biomass), commonly referred to a unit area or volume of habitat. The weight or quantity of organisms in an area at a given moment is the standing crop. The total amount of organic material produced by living organisms in a particular area within a set period of time, called the primary or secondary productivity (the former for plants, the latter for animals), is usually measured in units of energy, such as gram calories or kilojoules per square metre per year. Measures of weight—e.g., tons of carbon per square kilometre per year or gigatons of carbon per year—are also commonly recorded.

In a different though related sense, the term biomass refers to plant materials and animal waste used especially as a source of fuel.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by John P. Rafferty, Editor.

Three major types of ecological pyramids exist: pyramid of number, biomass, and energy. They are described as follows.

1. Pyramid of Number

  • This type of pyramid can have two different forms depending on the number of organisms: upright and inverted.
  • In an upright pyramid of number, the number of organisms generally decreases from the bottom to top. This generally occurs in grassland and pond ecosystems where the plants (usually the grasses) occupy the base of the pyramid. The succeeding levels of the pyramid include the consumers.
  • An inverted pyramid of number, on the other hand, is just the opposite of the former. It is usually observed in tree ecosystems with the trees as the producers and the insects as consumers.

Among the three types of ecological pyramids, the pyramid of number is the least accurate for it does not take account the exact number of population and therefore cannot completely define the trophic structure in that ecosystem.

2. Pyramid of Biomass

  • For instance, a pyramid of biomass is a depiction of the amount of food available and how much energy is being passed on at each trophic level. Most the biomass that animals consume is used to provide the energy, converted to new tissues, or just remain undigested.
  • Most of the time, pyramids of biomass are in a true pyramidal shape with biomass in the lower trophic levels are greater than the trophic levels above them.
  • Like the pyramid of numbers, the pyramid of biomass can either have two forms: upright and inverted. Usually, terrestrial ecosystems are characterized by an upright pyramid of biomass having a larger base (primary producers) with the smaller trophic levels (consumers) located at the top.
  • On the other hand, aquatic ecosystems are the complete opposite as they will assume the inverted structure of the pyramid. This is because the phytoplankton producers (with generally smaller biomass) are located at the base while the consumers having larger biomass are located at the top of the pyramid.

Biomass is also used as a source of renewable energy in replacement of fossil fuels. This alternative has dramatically helped in the improvement of the planet’s climatic conditions. A wide variety of benefits can be obtained from the utilization of biomass as a fuel, and they include the reduction of wastes and low costs.

3. Pyramid of Energy

  • The pattern of the energy flow in this type of pyramid is based on the principles of thermodynamics. This law specifically says that energy is neither be created nor destroyed only transformed into another form.
  • This pyramid shows that energy is transferred from lower trophic levels with more amount of energy (producers) to higher ones (consumers) and converted in the biomass.
  • Therefore, it can be concluded that organisms found at the highest trophic levels of shorter food chains bear a greater amount of energy than the ones found in longer ones.
  • Unlike the first two ecological pyramids, the pyramid of energy is always illustrated in an upright position, with the largest energy carriers at the base.

The idea of the pyramid of energy is very crucial in the idea of biological magnification, which is defined as the tendency of toxic substances to increase in amount as you go up the trophic levels.

CBSE Class 12 Biology Board Exam 2018: Important 5 Marks questions

Get important (5 Marks) questions for CBSE Class 12 Biology board exam 2018. As per latest Class 12 Biology exam pattern, students have to attempt three 5 marks questions. These are long answer type questions.

Important 5 marks questions for Class 12 Biology board exam 2018 are available here. As per latest CBSE Class 12 Biology exam pattern 2018, students will get three 5 marks questions in the paper means a total of 15 marks.

Students preparing for CBSE Class 12 Biology board exam 2018 are advised to go through the latest Sample Paper issued by CBSE.

If you are looking for important 1 marks, 2 marks and 3 marks questions of CBSE Class 12 Biology board exam 2018 then please go through the links given below:

Important (5 marks) questions for Class 12 Biology board exam 2018 are given below

Question: (a) Mention the role of vectors in recombinant DNA technology. Give any two examples.

(b) With the help of diagrammatic representation only, show the steps of recombinant DNA technology.

Question: (a) What is plasmid?

(b) What is meant by ADA deficiency? How is gene therapy a solution to this problem? Why is not a permanent cure?

Question: Explain Hershey-Chase experiment. What was proved through this experiment?

Question: (a) A true breeding pea plant, homozygous for inflated green pods is crossed with another pea plant with constricted yellow pods (ffgg). What would be the phenotype and genotype of F1 and F2 generations? Give the phenotype ratio of F2 generation.

(b) State the generalisation proposed by Mendel on the basis of the above mentioned cross

Question: Explain the steps involved in the production of genetically engineered insulin.

Question: (a) Name the nematode that infects and damages tobacco roots.

(b) How are transgenic tobacco plants produced to solve this problem?

Question: Explain the steps involved in the production of genetically engineered insulin.

Question: (a) Name the nematode that infests and damages tobacco roots.

(b) How are transgenic tobacco plants produced to solve this problem?

Question: Explain the steps involved in the production of genetically engineered insulin. Why is insulin thus produced preferred to the one produced from non-human sources?

Question: (a) Why is Bacillus thuringiensis considered suitable for developing GM plants?

(b) Explain how it has been used to develop GM crops.

Question: What is semiconservative replication of DNA? Explain how it was experimentally proved.

Question: (a) A true breeding pea plant homozygous for axial violet flowers is crossed with another pea plant with terminal white flowers (aavv). Work out the cross to show the phenotypes and genotypes of F1 and F2 generations along with the ratios.

(b) State the law that Mendel proposed on the basis of such a cross.

Question: What are transgenic animals? Explain any four ways in which such animals can be beneficial to humans.

Question: (a) What is a plasmid?

(b) What is meant by ADA deficiency? How is gene therapy a solution to this problem? Why is it not a permanent cure?

Question: Explain with the help of a diagram the development of a mature embryo sac from a megaspore mother cell in angiosperm.

Question: (a) Explain the experiment performed by Griffith on Streptococcus pneumoniae. What did he conclude from this experiment?

(b) Name the three scientists who followed up Griffith’s experiments.

(c) What did they conclude and how?

Two blood samples A and B picked up from the crime scene were handed over to the forensic department for genetic fingerprinting. Describe how the technique of genetic fingerprinting is carried out. How will it be confirmed whether the samples belonged to the same individual or to two different individuals?

Question: One of the main objectives of biotechnology is to minimise the use of insecticides on cultivated crops. Explain with the help of a suitable example how insect resistant crops have been developed using techniques of biotechnology.

Question: (a) How is mature insulin different from proinsulin secreted by pancreas in humans?

(b) Explain how was human functional insulin produced using rDNA technology.

(c) Why is the functional insulin thus produced considered better than the ones used earlier by diabetic patients?

Question: (a) How did Griffith explain the transformation of R strain (non-virulent) bacteria into S strain (virulent)?

(b) Explain how MacLeod, McCarty and Avery determined the biochemical nature of the molecule responsible for transforming R strain bacteria into S strain bacteria.

Question: (a) You are given tall pea plants with yellow seeds whose genotypes are unknown. How would you find the genotype of these plants? Explain with the help of cross.

(b) Identify a, b and c in the table given below:

Monohybrid F1 phenotypic expression

The progeny resembled only one of the parents

(a) When and how does placenta develop in human female?

(b) How is the placenta connected to the embryo?

(c) Placenta acts as an endocrine gland. Explain.

(i) How does a Chromosomal disorder differ from a Mendelian disorder?

(ii) Name any two chromosomal aberration associated disorders.

(iii) List the characteristics of the disorders mentioned above that help in their diagnosis.

Fitness is the end result of the ability to adapt and get selected by nature. Explain with suitable example.

When and where are primary oocytes formed in a human female? Trace the development of these oocytes till ovulation (in menstrual cycle). How do gonadotropins influence this developmental process?

(i) Explain the events taking place at the time of fertilization of an ovum in a human female.

(ii) Trace the development of the zygote upto its implantation in the uterus.

(iii) Name and draw a labelled sectional view of the embryonic stage that gets implanted.

Describe the process of decomposition of detritus under the following heads: Fragmentation leaching catabolism humification and mineralisation.

Question: Describe in sequence the events that lead to the development of a 3-celled pollen grain from microspore mother cell in angiosperms.

Question: (a) Give a schematic representation showing the events of spermatogenesis in human male.

(b) Describe the structure of a human sperm.

Question: (a) State the law of independent assortment.

(b) Using Punnett Square demonstrate the law of independent assortment in a dihybrid cross involving two heterozygous parents.

Question: How did Alfred Hershey and Martha Chase arrive at the conclusion that DNA is the genetic material?

Question: (a) Why are herbivores considered similar to predators in the ecological context? Explain.

(b) Differentiate between the following interspecific interactions in a population:

(i) Mutualism and Competition

(ii) Commensalism and Amensalism

Question: (a) Trace the succession of plants on a dry bare rock.

(b) How does phosphorus cycle differ from carbon cycle?

Question: Explain double fertilisation and trace the post-fertilisation events in sequential order leading to seed formation in a typical dicotyledonous plant.

Question: Explain the process of fertilisation in human female, and trace the post-fertilisation events in a sequential order up to implantation of the embryo.

Question: (a) Explain with the help of a graph the population growth curve when resources are

(i) limiting and (ii) not limiting.

(b) “Nature has a carrying capacity for a species.” Explain.

Question: ABO blood grouping in human population exhibits four possible phenotypes from six different genotypes. Explain different mechanisms of inheritance involved in exhibiting the possibility of four phenotypes and six genotypes.

Question: Where do transcription and translation occur in bacteria and eukaryotes respectively? Explain the complexities in transcription and translation in eukaryotes that are not seen in bacteria.

Question: (a) State the arrangement of different genes that in bacteria is referred to as ‘operon’.

(b) Draw a schematic labelled illustration of lac operon in a ‘switched on’ state.

(c) Describe the role of lactose in lac operon.

Question: (a) A true breeding homozygous pea plant with green pods and axial flowers as dominant characters, is crossed with a recessive homozygous pea plant with yellow pods and terminal flowers. Work out the cross up to F2 generation giving the phenotypic ratios of F1 and F2 generation respectively.

(b) State the Mendelian principle which can be derived from such a cross and not from monohybrid cross.

Question: Explain the process of protein synthesis from processed m-RNA. 5

Question: Which methodology is used while sequencing the total DNA from a cell? Explain it in detail.

Question: Citing lake as an example of a simple aquatic ecosystem, interpret how various functions of this ecosystem are carried out. Make a food chain that is functional in this ecosystem.

(a) Colonization of a rocky terrain is a natural process. Mention the group of organisms which invade this area first. Give an example.

(b) Over the years, it has been observed that some of the lakes are disappearing due to urbanization. In absence of human interference, depict by making a flow chart, how do the successional seres progress from hydric to mesic condition.

(c) Identify the climax community of hydrarch and xerarch succession.

Question: Draw a labelled diagram of the sectional view of a mature pollen grain in angiosperms.

Explain the functions of its different parts.

Question: Give a schematic representation of oogenesis in humans. Mention the number of chromosomes at each stage. Correlate the life phases of the individual with the stages of the process.

Question: (a) Draw a schematic labelled diagram of a fertilised embryo sac of an Angiosperm.

(b) Describe the stages in embryo development in a dicot plant.

Question: (a) Draw a labelled diagram of a sectional view of human seminiferous tubule.

(b) Differentiate between gametogenesis in human males and females on the basis of:

(i) time of initiation of the process.

(ii) products formed at the end of the process.

Question: (a) Draw a labelled schematic representation of a mature embryo sac of an angiosperm.

(b) Explain the role of ovarian hormones in inducing changes in the uterus during menstrual cycle.

(c) What triggers release of oxytocin at the time of parturition?

Question: (a) Give a schematic representation of oogenesis in human female indicating the chromosomal number at each step. Mention at what stage of female life does each phase occur.

(b) Where would you look for coleoptile and coleorhiza? What function do they perform?

(a) Trace the development of embryo after syngamy in a dicot plant.

(b) Endosperm development precedes embryo development. Explain.

(c) Draw a diagram of a mature dicot embryo and label cotyledons, plumule, radicle and hypocotyl in it.

(a) Draw a labelled diagram of L.S. of a flower to show the growth of pollen tube reaching egg apparatus.

(b) Pistil of a flower does not accept pollen from any plant other than from its own kind. How does it happen? Explain

Draw and explain a logistic curve for a population of density (N) at time (t) whose intrinsic rate of natural increase is (r) and carrying capacity is (k).

Question: (a) Draw the pyramids of biomass in a sea and in a forest. Explain giving reasons why the two pyramids are different.

  1. The red-crowned crane is named for the red "cap" on top of its head, which is exposed red skin. These cranes are considered sacred in Japan, where they are considered a sign of fidelity in marriage.
  2. On average, red-crowned cranes are the heaviest crane species, weighing up to 25 pounds.
  • Least Concern
  • Near Threatened
  • Vulnerable
  • Endangered
  • Critically Endangered
  • Extinct in the Wild
  • Extinct
  • Data Deficient
  • Not Evaluated

The red-crowned crane has snow-white primary feathers with a black face and neck. White feathers extend from behind the eyes to the nape, and a red patch tops the crane's head, giving it its name. The majority of the body is pure white with the exception of black secondary and tertiary feathers. The red-crowned crane has a deep green bill and a long, sharply angular beak for spearing its prey. Both males and females are the same color, and males tend to be slightly larger.

Juveniles have a combination of white, partly tawny, cinnamon brown and/or gray plumage. The neck collar is gray to coffee brown, the secondary feathers are dull black and brown, and the crown and forehead are covered with gray and tawny feathers. The legs and bill are similar to those of adults but lighter in color. The primary feathers are white, tipped with black, as are the upper primary coverts. At two years of age, the bird's primary feathers are replaced with all white feathers.

Red-crowned cranes are highly aquatic cranes with large home ranges in southeastern Russia, northeast China, Mongolia and eastern Japan. They feed in deeper water than other cranes. They also forage regularly on pasturelands in Japan, and in winter they use coastal salt marshes, rivers, freshwater marshes, rice paddies and cultivated fields. These cranes prefer to nest in marshes with relatively deep water and standing, dead vegetation.

Red-crowned cranes are well adapted to cold temperatures. The Russian and Chinese populations mainly winter in the Yellow River delta. the coast of Jiangsu province, China, and the Korean Demilitarized Zone. In winter and on passage, the birds occur in wetlands, including tidal flats, saltmarshes, rivers, wet grassland, saltpans and aquaculture ponds. These cranes are migratory. The Japanese population, however, is non-migratory.

The omnivorous birds seek out sustenance in marshes and feeds on a variety of invertebrates and small aquatic invertebrates, fish, amphibians, rodents, reeds, grasses, heath berries, corn and other plants. In the winter, they move to paddy fields where they feed on rice. During the winter, the Japanese population feeds on corn at artificial feeding stations. Cranes in managed populations are fed crane pellets, mealworms, earthworms, crickets and small fish.

Red-crowned crane pairs are generally monogamous. Nests are built on wet ground or in shallow water. Females usually lay two eggs, and incubation (by both sexes) lasts 29 to 34 days. The male takes the primary role in defending the nest against possible danger. Chicks fledge, or take their first flight, at about 95 days . When the young cranes are three months old, they accompany their parents while looking for food in the wetlands. They are able to fly by autumn. Families stay intact until the next breeding season when the young adults leave the parents.

Lifespan in the wild is not well documented, but in human care the median age for both sexes of red-crowned cranes is 15.1 years.

Red-crowned cranes are the second-rarest species of crane, the whooping crane of North America being the rarest. The key threat to red-crowned cranes is the loss and degradation of wetlands in their breeding and wintering grounds, as human development, principally for conversion to agriculture but also industrial and economic development, encroaches rapidly on the wetlands that these large birds require.

This loss of habitat is leading to the over-concentration of cranes at a few sites. There are 1,700 to 2,700 red-crowned cranes in all of Eastern Asia, according to the International Union for Conservation of Nature’s Red List of Threatened Species.

Red-crowned Cranes at the Smithsonian Conservation Biology Institute

The Smithsonian Conservation Biology Institute was part of a program that donated red-crowned crane eggs, which were flown to Russia and raised in the Khinganski Nature Reserve. The offspring were later released into the wild. This program sent about 150 eggs between 1995 and 2005.

The program has been put on hold in order to concentrate on different crane conservation programs in Russia, such as education. Without a doubt, the international efforts of Russia, China, Japan and Korea are needed to protect the species from extinction. The most pressing threat is habitat destruction, with a general lack of remaining pristine wetland habitat for the species to nest in.

SCBI is one of the few centers with the expertise and space to manage cranes. The development of artificial insemination and egg sexing has allowed SCBI to successfully breed cranes that other facilities could not, due to behavioral or physical limitations. In addition, the large facility in Front Royal, Virginia, allows for the housing of singletons. There are no reintroduction programs for red-crowned cranes at this time.

Currently the red-crowned cranes at SCBI are not recommended for breeding by the Species Survival Plan, due to a nationwide lack of space combined with the overall lower genetic value of some of the individuals. SCBI received a juvenile male for pairing with a single female. Once the male reaches sexual maturity, at approximately 3 years of age, this pair will be bred. SCBI has produced five red-crowned crane chicks over the last 30 years.

Watch the video: Wie nachhaltig sind Biomasse-Kraftwerke? (May 2022).