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Energy flows - class-XII

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A freshwater organism cannot survive in a water body that has grater ......... that its original habit. 

  1. Oxygen content

  2. Depth

  3. Salt concentration

  4. Water clarity


Correct Option: C
Explanation:

For aquatic organisms the quality (chemical composition, PH) of water is very important. The salt concentration (measured as salinity in parts per thousand), is less than 5 parts per thousand in inland waters, 30-35 parts per thousand in the sea and more than 100 parts per thousand in some hyper saline lagoons. Many fresh water animals cannot live for long in sea water and vice versa because of the osmotic problems they would face. 

So, the correct answer is 'Salt concentration'.

The trophic efficiency of producers, herbivores and carnivores are respectively

  1. $10%, 20%, 30%$

  2. $20%, 30%, 60%$

  3. $20%,40%,80%$

  4. Always $10%$


Correct Option: A
Explanation:
According to Lindeman's law of trophic efficiency, 10% of the energy is transferred from one trophic level to another. The trophic efficiency is related to the growth efficiency and standard metabolism of the individual.
So, the correct answer is '10'.

Ten percent of energy gets transferred in food chain, this is enuciated by

  1. Lindeman

  2. Haeckel

  3. Schimper

  4. Zernicke


Correct Option: A
Explanation:

Raymond Lindeman gave the famous 10 % law. According to this law, at each trophic level, only 10% of the energy of the subsequent trophic levels is transmitted. So, the amount of energy goes on decreasing at each tropic level.

So, option A "Lindeman" is the correct answer.

Ecosystem dynamics is governed by

  1. Solar radiation and the carbon cycle

  2. Photosynthesis and respiration

  3. The carbon cycle and photosynthesis

  4. Energy flow and chemical/nutrient cycling

  5. The nitrogen cycle and the phosphorous cycle


Correct Option: D

The energy flow in an ecosystem is

  1. Multidirectional

  2. Unidirectional

  3. Bidirectional

  4. Circular


Correct Option: B
Explanation:

The flow of energy in the ecosystem is unidirectional. The energy enters the plants (from the sun) through photosynthesis during the making of food. This energy is then passed on to the successive trophic levels in a food chain is only 10% and rest energy get lost as heat during transfer and life process. 

Thus, the correct answer is option A.

According to a pyramid of production, approximately what percent of the energy at a trophic level is transferred to the next trophic level? 

  1. 2%

  2. 10%

  3. 50%

  4. 75%

  5. 90%


Correct Option: B
Explanation:
The number of trophic levels in the food chain is restricted as the transfer of energy follows 10 percent law. This law states that only 10% of the energy is transferred to each trophic level from the lower trophic level. 
According to Lindeman's Law of trophic efficiency, the efficiency of energy transfer from one trophic level to the next is about 10%. Lindeman considered individual organisms belongs to trophic levels with each level acting as a transformer of energy.
So, the correct answer is 10%.

The best source of energy in the environment is

  1. Water

  2. Soil

  3. Trees

  4. Ponds


Correct Option: C
Explanation:

Trees are autotrophs or producers in an ecosystem and trap solar energy. The solar energy is converted into chemical energy, which is stored in seeds, fruits and other storage organs. Thus, producers like trees are the source of chemical energy for all the heterotrophic organisms. All the heterotrophs either directly or indirectly depend on the food, synthesized by producers like trees. These organisms directly cannot use solar energy.

10% law of flow of energy in ecosystem was proposed by

  1. Lindeman

  2. Carl Mobius

  3. Tansley

  4. Darwin


Correct Option: A
Explanation:

Only 10 percent of the gross productivity of producer is entrapped by herbivores for their body-building. Herbivores are eaten by primary carnivores. Only 10 percent of the herbivore productivity is utilised by carnivores. Higher carnivores are similarly able to retain only 10 percent of energy present in primary carnivores. This is called as 10 percent law by Lindeman.

Inorganic element that changes food into usable energy is

  1. S

  2. P

  3. Ca

  4. Mg


Correct Option: B

Energy enters an ecosystem through 

  1. Herbivores

  2. Producers

  3. Carnivores

  4. Decomposers


Correct Option: B
Explanation:

A food chain is series of plants/animals which are interrelated in the form of organism being eaten as food by the other. It consists of producers, consumers and decomposers. The energy enters in an ecosystem through producers. Plants are producers which convert solar energy into chemical energy through photosynthesis. From producers, the energy is then transferred to the herbivores and carnivores. The animals eating plants are called as primary consumers or herbivores and animals eating primary consumers are called as secondary consumers or carnivores. Decomposers are those which decay the waster organic matter and release energy back in the environment.

Thus, the correct answer is 'Producers.'

Transfer of energy in different trophic levels of an ecosystem is

  1. Bioenergetics

  2. Biosystem

  3. Geobiocoenosis

  4. Holocoenosis


Correct Option: A
Explanation:

Flow of energy in different trophic levels of an ecosystem is called as bioenergetics. It is also called as energy flow. In this, there is flow of energy through the food chain. Solar energy is converted to chemical energy by photosynthetic plants. From plants, the energy is transferred to primary consumers and secondary consumers in a food chain. Decomposers release energy back to the environment by decomposing organic waste matter.

Thus, the correct answer is 'Bioenergetics.'

Amount of energy transferred from one trophic level to next is

  1. 1.5%

  2. 10%

  3. 15%

  4. 20%


Correct Option: B
Explanation:
Flow of energy declines as it passes from lower to higher trophic level. The energy decreases from one trophic level to the next trophic level because energy is lost as metabolic heat during transfer of energy. When food energy passes from producers to herbivores to carnivores, only 10% of energy is transferred from one trophic level to another trophic level. Hence, producers receives the maximum energy.
Thus, the correct answer is '10%.'

Efficiency of energy transfer from one trophic level to the higher trophic level is called

  1. Assimilation efficiency

  2. Exploitation efficiency

  3. Lindeman's trophic efficiency rule

  4. Gross primary productivity


Correct Option: C
Explanation:

Lindeman's trophic efficiency rule was introduced by Reymond Lindeman. According to this rule, the 10% of transfer of energy is transferred from one trophic level to the next successive trophic level. The rest of the energy is lost during transfer of energy and during respiration. The first trophic level has the maximum energy. 

Thus, the correct answer is 'Lindeman's trophic efficiency rule.'

The amount of usable energy remains constant as it is passed from one trophic level to another.

  1. True

  2. False

  3. Either

  4. Neither


Correct Option: B
Explanation:
Organisms depend on the organisms of lower trophic levels for their energy requirements. There is a certain mass of living matter present in a trophic level at a particular time which is called standing crop and measured as mass of living organisms i.e. biomass. The biomass of species is measured in terms of dry weight. Transfer of energy from one trophic level to next trophic level follows 10 percent law known as Lindeman's law of trophic efficiency which states that the efficiency of energy transferred from one trophic level to the next higher trophic level is about 10%. So the energy decreases as it is transferred to subsequent trophic levels.
Hence, the statement given in the question is incorrect.
So, the correct answer is 'False'.

The maximum energy is stored at following trophical level in any ecosystem

  1. Producers

  2. Herbivores

  3. Carnivores

  4. Top carnivores


Correct Option: A
Explanation:
A. Producers are the green plants which synthesise their own food using sunlight.
B. Herbivores are primary consumers which feed on producers.
C. Carnivores are secondary consumers who feed primary consumers.
D. Top carnivores are tertiary consumers who feed on other carnivores.
Maximum energy is stored in the trophic levels of producers as they synthesise their own food. They occupy the lowest trophic level and energy is transferred from them to higher subsequent trophic levels. As the energy decreases each time it is transferred to the next higher trophic level, the lowest trophic level i.e. producers, have maximum energy.
So, the correct answer is 'Producers'.  

The energy within an ecosystem is fixed and never changes.

  1. True

  2. False

  3. Either

  4. Neither


Correct Option: B
Explanation:
In an ecosystem, sun is the ultimate source of energy. The solar energy is converted into chemical energy by plants and is stored in them. This energy is then passed to other organisms as they feed on producers. The transfer of energy from one trophic level to other follows 10 percent law according to which only 10% of the energy is passed from one trophic level to next and rest of the energy is lost in respiration and in the form of heat. Thus, energy within an ecosystem is not fixed.
Hence, the statement given in the question is not correct.
So, the correct answer is 'False'.

If $5$ joules of energy is available at producer level then find the energy transferred to the lion in the following food chain.
Plants $\rightarrow$ Deer $\rightarrow$ Lion

  1. $5$ joules

  2. $0.5$ joules

  3. $0.05$ joules

  4. $0.005$ joules

  5. None of these


Correct Option: C
Explanation:
  • According to the 10% rule when energy is passed in an ecosystem from one tropic level to the next, only 10% of the energy is passed on and the rest is wasted.
  • 10% of (10% of 5 joules)=Energy transferred to the lion.
  • So, the correct choice is '0.05 joules'.

Grass $\rightarrow$ Deer $\rightarrow$ Tiger
In this food chain, the biomass of grass is $1$ tonne. The tiger biomass will be:

  1. $100 \,kg$

  2. $10 \,kg$

  3. $1 \,kg$

  4. $1000 \,kg$


Correct Option: B
Explanation:

According to 10% law of Lindemann, if 1 tonne (1000 kg) biomass is present in grass, only 10% of it means 100 kg will go into deer and in tiger the biomass will be only 10 kg, i.e. 10% of deer's biomass.

So, the correct option is '10kg'.

An ecosystem is maintained by the flow of energy derived from the Sun. Energy trapped by plants varies from ecosystem to ecosystem. The table given shows energy absorption by different vegetations of different ecosystem.

Vegetation $\%$ of energy absorption
a) Aquatic ecosystem $15-16\%$
b) Grassland $14-15\%$
c) Mixed forest $13-14\%$
d) Modern $C _3$ crops $12-13\%$
e) Modern $C _4$ crops $10-12\%$

Find the correct match.

  1. C

  2. B

  3. A

  4. E


Correct Option: C
Explanation:

An ecosystem is normally an open system because there are a continuous and variable entry and loss of energy and material. The ecosystem is the basic fundamental unit of ecology which includes both the organism and the non-living environment is influencing the property of each other and is necessary for the maintenance of life. The whole Earth can be known as biosphere or ecosphere.

Various plant and various vegetation have a different level of energy absorption. There is a grassland ecosystem and a forest ecosystem and many other.
So, the correct option is 'C' 

The pyramid of energy is the best representation of an ecosystem because it indicates

  1. Relation of all plants and animals

  2. Total energy present in an ecosystem

  3. The rate of flow of energy through the food chain

  4. None of the above


Correct Option: C
Explanation:
  • The pyramid of energy shows the relationship between the flow of energy and different trophic level.
  • The pyramid of energy depicts the flow of energy in the ecosystem.
  • The source of energy in an ecosystem is the sun, the producers trap the solar energy and use it for photosynthesis which is in turn eaten by organisms of the higher trophic level such as primary consumers, secondary consumers.
  • So, the correct answer is 'The rate of flow of energy through the food chain'.

The cost of other ecosystem services like recreation and nutrient cycling are?

  1. $> 10\%$ each

  2. $< 6\%$ each

  3. $< 10\%$ each

  4. $6\%$ each


Correct Option: A
Explanation:

The cost of ether ecosystem services like recreation and nutrient cycling are > 10% each.

The importance of ecosystem maintenance lies in

  1. Cycling of materials

  2. Flow of energy

  3. Both of the above

  4. None of the above


Correct Option: C
Explanation:

An ecosystem comprises of biotic and abiotic components which interact with each other to maintain an equilibrium. A major focus of ecosystem ecology is on functional processes, ecological mechanisms, that maintain the structure and services produced by ecosystems. These include primary productivity (production of biomass), decomposition, and trophic interactions. The various trophic levels of an ecosystem interact with each other by  a flow of energy and cycling of materials from one trophic level to the other.

Which of the cycle is concerned with energy flow in the ecosystem?

  1. Food cycle

  2. O$ _2$ cycle

  3. Cl$ _2$ cycle

  4. All of the above


Correct Option: A
Explanation:

A food cycle is associated with energy flow in the ecosystem. It contains several trophic levels which are interdependent to each other for energy. Only 10% of energy can be transferred to the successive trophic level and rest 90% get utilise in their life processes.

Thus, the correct answer is option A.

One way cycle is

  1. CO$ _2$ cycle

  2. H$ _2$O cycle

  3. Free energy cycle

  4. O$ _2$ cycle


Correct Option: C
Explanation:

Free energy cycle is the unidirectional cycle in our ecosystem. In other cycles like oxygen cycle, carbon dioxide cycle and water cycle, the basic elements are circulated and cycled whereas, in free energy cycle, energy flows from solar energy to producers and then consumers to decomposers. 


The transfer of energy from a level to another is governed by Law of thermodynamics. The average efficiency of energy transfer from herbivores to carnivores level is

  1. 10%

  2. 25%

  3. 5%

  4. 50%


Correct Option: A
Explanation:

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.

10% energy transfer law in food chain was first given by

  1. Lindeman

  2. Tansley

  3. Elton

  4. Raunkiaer


Correct Option: A
Explanation:

The ten percent law for the transfer of energy from one trophic level to the next was introduced by Raymond Lindeman (1942). 

According to this law, during the transfer of energy from organic food from one trophic level to the next, only about ten percent of the energy from organic matter is stored as flesh. The remaining is lost during transfer, broken down in respiration, or lost to incomplete digestion by higher trophic levels.

The study of energy transfer in an ecosystem at different trophic levels is known as

  1. Bioenergetics

  2. Geobiocoenosis

  3. Holocoenosis

  4. Biosystem


Correct Option: A
Explanation:

Bioenergetics is a field in biochemistry, that concerns energy flow through living systems. This includes the study of different cellular processes, such as cellular respiration and the many other metabolic processes, that can lead to production and utilization of energy in forms such as ATP molecules.

Percentage energy transferred to higher trophic level in food chain is 

  1. 1%

  2. 10%

  3. 90%

  4. 100%


Correct Option: B
Explanation:

The ten percent law for the transfer of energy from one trophic level to the next was introduced by Raymond Lindeman (1942). According to this law, during the transfer of energy from organic food from one trophic level to the next, only about ten percent of the energy from organic matter is stored as flesh. The remaining is lost during transfer, broken down in respiration, or lost to incomplete digestion by higher trophic levels.

The pyramid of number of individuals per unit area in grassland ecosystem will be

  1. Erect

  2. Inverted

  3. Both A and B

  4. None of the above


Correct Option: A
Explanation:

Pyramids of numbers describes the relationship between organisms at successive trophic levels in terms of their number. In grassland, the producers, which are mainly grasses are always maximum in number as compared to the  primary consumers, the secondary consumers like snakes and lizards are lesser in number than the rabbits and mice. Finally, the top (tertiary) consumers like hawks or other birds are least in number. Thus, the pyramid becomes upright.

Therefore, the correct answer is option A.

A component of physical environment of an ecosystem is

  1. Sunlight

  2. Decomposers

  3. Water

  4. Temperature


Correct Option: A
Explanation:

The physical components of the environment are also known as abiotic components. They include soil, water, air, climate, temperature and sunlight. It determines the type of habitat or living conditions of the living population. Thus the correct answer is option A.

About how much of the net primary productivity of a terrestrial ecosystem is eaten and digested by herbivores?

  1. 10%

  2. 1%

  3. 30%

  4. 50%


Correct Option: A
Explanation:

According to the 10%  law, in a terrestrial ecosystem during the transfer of energy from one trophic level to the next, about ten percent of the energy in the form of organic matter is eaten and digested and stored as flesh. The remaining is lost during transfer in the form respiration or incomplete digestion. Thus the correct answer is option A.

10% law of energy transfer was given by

  1. Lindemann

  2. Tansley

  3. Stanley

  4. Darwin


Correct Option: A
Explanation:

Lindemann (1942) put forth ten percent law for the transfer of energy from one trophic level to the next. According to the law, during the transfer of organic food from one trophic level to the next, only about ten percent of the organic matter is stored as flesh. The remaining is lost during transfer or broken down in respiration.

Plants utilise sun energy for primary production and can store only 10% of the utilised energy as net production available for the herbivores. When the plants are consumed by animal, about 10% of the energy in the food is fixed into animal flesh which is available for next trophic level (carnivores). When a carnivore consumes that animal, only about 10% of energy is fixed in its flesh for the higher level.

So at each transfer 80 - 90% of potential energy is dissipated as heat (second law of thermodynamics) where only 10 - 20% of energy is available to the next trophic level.

Therefore, the correct answer is option A.

Which of the following is the correct order of flow of energy?

  1. Plants--> tigers--> microbes--> goats

  2. Plants--> goats--> tigers--> microbes

  3. Tiger--> plants--> microbes--> goats

  4. Microbes--> tigers--> goats--> plants


Correct Option: B
Explanation:

The flow of energy is always unidirectional. The energy passes from primary producers to primary consumers. From the primary consumers, the energy is passed to secondary consumers and then to tertiary consumers. Thus the energy pyramid is always upright.

If first trophic level represent 100,000 kcal of energy. According to Lindman's law, how much energy is available to the fourth trophic level?

  1. 10 kcal

  2. 100 kcal

  3. 1,000 kcal

  4. 10,000 kcal

  5. 100,000 kcal


Correct Option: B
Explanation:
If first trophic level represents 100,000 kcal of energy, in second level it will have 10% of 100000 = 10000 kcal.
In third level, 10 % of 10000 = 1000 kcal
In fourth level, 10% of 1000 = 100 kcal
The Ten percent law is the transfer of energy from one trophic level to the next was introduced by Raymond Lindeman (1942). According to this law, during the transfer of energy from organic food from one trophic level to the next, only about ten percent of the energy from organic matter is stored as flesh.

Autotrophic species produce 400,000 kJ of energy in a tropical food web. The amount of energy at the level of secondary consumers is

  1. 40 KJ

  2. 400 KJ

  3. 4000 KJ

  4. 40, 000 KJ

  5. 4000, 000 KJ


Correct Option: C
Explanation:

Energy transfer along each trophic level of a food chain exhibit loss of 90% energy as heat and transfer of only 10% energy to the next trophic level. The energy is lost in metabolic activities. According to this, out of 400,000kJ energy of primary producers, 40000kJ will be transferred to primary consumers and 4000kJ will be transferred to the secondary consumer. Tertiary consumers will obtain only 400kJ energy from secondary consumers while top consumers will obtain as little as 40kJ energy. Correct answer is option C.

Find the incorrect statement about the energy flow through an ecosystem?

  1. Energy is conserved and stays in an ecosystem, to be used by organisms again and again.

  2. Solar radiation is the original energy source for the vast majority of organisms on earth.

  3. Energy flow is one-way, from autotrophs to progressively higher trophic levels.

  4. Energy flow is inefficient; a lot is lost in each transfer from one organism to another.

  5. All solar radiation used in photosynthesis will eventually be lost as heat.


Correct Option: A
Read the passage and answer the following question.

Assume you had a 10m$^2$ pond to study. You measured the amount of light energy bathing the water surface at 1,000kcal.


Based on the energy captured, about what percentage of that would be transferred to higher trophic levels?

  1. 1.65 percent

  2. 16.5 percent

  3. 33 percent

  4. 3.3 percent

  5. 66 percent


Correct Option: B

If the energy produced by plants is 800,000 kJ, then how much energy will exist at the level of secondary consumers?

  1. 80 kJ

  2. 800 kJ

  3. 8,000 kJ

  4. 80,000 kJ

  5. 800,000 kJ


Correct Option: C
Explanation:

According to the 10 percent law, when energy is passed in an ecosystem from one trophic level to the next, only ten percent of the energy will be passed on.  The remaining is lost during transfer, broken down in respiration, or lost to incomplete digestion by higher trophic levels.

As per this rule, if the plant produces 800,000kJ of energy then only 10% of this is passed to the next trophic level which is the primary consumers. So, the energy obtained by the primary consumer will be 80,000kJ.
Now, only 10% of this 80,000kJ is passed on to the next trophic level (secondary consumers) which is 8,000KJ.
So, the correct answer is option C.

According to Lindeman's 10% law, only 10% energy is transferred to the next trophic level. If the plants produce 100 units of energy, the amount of energy at the level of secondary consumers would be

  1. 1 unit

  2. 25 units

  3. 50 units

  4. 70 units

  5. 80 units


Correct Option: A
Explanation:

10 percent Law introduced by Lindeman states that only 10% of energy is transferred from one trophic level to another and 90% of the energy is lost during transfer, respiration and digestion processes. Therefore if plants (present at producers level) produces 100 units of energy, 10% of it will be transferred to primary consumers (10 units of energy) and 10% of the subsequent energy is transferred to secondary consumers (1 unit of energy). Hence, the correct answer is option A.

Only a small portion of chemical energy in an apple is transferred to an organism that eats it.
What happens to the majority of the chemical energy stored in the apple when another organism eats it?

  1. The majority of the energy is spontaneously lost to the surroundings.

  2. The majority of the energy is used to do some kind of cellular work in the apple.

  3. The majority of the energy is lost as heat energy to the surrounding environment.

  4. The majority of the energy is destroyed or recycled.


Correct Option: B
Explanation:

The transfer of energy from one trophic level to another follows the 10% law of energy transfer. So, of the total energy created only 10% is passed on from the producers to the consumers while rest is used by the producer to carry out its activities

So, the correct answer is 'The majority of the energy is used to do some kind of cellular work in the apple'

Maintenance of internal favourable conditions, despite changes in external environment is

  1. Entropy

  2. Steady state

  3. Enthalpy

  4. Homeostasis


Correct Option: D
Explanation:

Higher animals like mammals tend to maintain a constant internal environment despite changes in external environment. This is called as homeostasis, e.g., in humans a body temperature around 97 fahrenheit is considered normal. In summers when outside temperature is high or in winters when outside temperature is very low the body temperature remains constant. This is one example of homeostasis. The nervous and endocrine system closely interplay to maintain homeostasis. Therefore, the correct answer is option D.

The movement of energy and nutrients through living systems differs in what way? 

  1. Energy recycles while nutrients flow in two directions.

  2. Nutrients recycle while energy flows in one direction.

  3. Nutrients are lost as heat while energy forms chemical compounds.

  4. Nutrients are constantly available while energy is limited.

  5. Nutrients are lost as heat while energy is limited.


Correct Option: B
Explanation:
Energy is passed from one trophic level to the next trophic level. Hence energy flows in one direction through successive trophic levels in a food chain. Nutrients are produced from the matter. The matter may be organic or inorganic. The organic and inorganic matter is produced, exchanged and moved within the ecosystem and this is called cycling. Hence nutrients are recycled.
So, the correct answer is 'Nutrients recycle while energy flows in one direction'.

Which best describes the movement of energy and matter through living systems? 

  1. Energy flows while matter is cycled.

  2. Matter flows in two directions while energy flows in one direction.

  3. Energy is cycled while some matter is lost as heat.

  4. Energy forms chemical compounds while matter flows.

  5. Matter is always available while energy is cycled.


Correct Option: A
Explanation:
Energy is passed from one trophic level to the next trophic level. Hence energy flows through successive trophic levels in a food chain. 
Matter may be organic or inorganic. The organic and inorganic matter is produced, exchanged and moved within the ecosystem and this is called cycling. Hence matter is cycled.
So, the correct answer is 'Energy flows while matter is cycled'.

Which one of the following is one way cycle?

  1. Carbon cycle

  2. H$ _{2}$O cycle

  3. Free energy cycle

  4. O$ _{2}$ cycle


Correct Option: C
Explanation:

The transfer of energy in an ecosystem is always one way, from the sun to producers, from producers to herbivores, from herbivores to carnivores. The one way transfer of energy is in accordance with the laws of thermodynamics. 

Water, carbon and oxygen cycle in the ecosystem and are regularly exchanged between biotic and abiotic components.

Flow of energy declines from low to higher trophic level in ecosystem, is mainly explained by

  1. First law of thermodynamics

  2. Second law of thermodynamics

  3. Both of the above

  4. None of the above


Correct Option: B
Explanation:

Ecosystem require a constant input of energy as every component of an ecosystem is regularly dissipating energy. Two laws of thermodynamics govern this flow of energy. 

According to first law of thermodynamics, energy can be transformed as well as transferred but is neither created nor destroyed. 
According to second law of thermodynamics, every activity and energy transformation is accompanied by dissipation of energy. 

The maximum energy in an ecosystem is available at lowest or producer level and as energy is transferred from producers to successively higher levels energy level gets diminished. Thus, the correct answer is option B.

The importance of ecosystem lies in

  1. Cycling of materials

  2. Flow of energy

  3. Both A and B

  4. None of the above


Correct Option: C
Explanation:

The ecosystem is an interaction between living beings (biotic component) and their physical environment (abiotic component).

The most important characteristics of any ecosystem are energy flow and cycling of materials. Green plants trap solar energy and convert it into a usable form, which is passed on to successive levels through food chains and food webs. The other important characteristic of the ecosystem is cycling of materials. This is called as the biogeochemical cycle, in which decomposers release nutrients back to the environment to maintain the ecosystem. Thus, the correct answer is option C.

Select correct answers :
(1) Flow of energy
(2) Flow of materials
(3) Flow information
(4) Flow of smoke

  1. 1, 2, 3 correct

  2. 1 and 2 correct

  3. 2 and 4 correct

  4. 1 and 3 correct


Correct Option: A

In terrestrial ecosystem, maximum energy is present in

  1. $T _3$

  2. $T _2$

  3. $T _1$

  4. $T _4$


Correct Option: C
Explanation:

The first trophic level is represented as T$ _1$. It includes producers. The second trophic level is represented as T$ _2$. It includes primary consumers. Similarly, third trophic level is represented as T$ _3$. It includes secondary consumers. In terrestrial ecosystem, maximum energy is present in T$ _1$, that is producers.

Thus, the correct answer is 'T$ _1$.' 

What percent of assimilated energy is used in respiration by the herbivores?

  1. 20%

  2. 30%

  3. 40%

  4. 60%


Correct Option: B
Explanation:

Large amount of assimilated energy is used in respiration. In herbivores, 30% of assimilated energy is used in respiration. Herbivores are more efficient in using energy for their growth and development than animals. Hence, plants grow faster than animals. 

Thus, the correct answer is '30%.'

In an ecosystem, which of the following shows one-way passage?

  1. Free energy

  2. Carbon

  3. Nitrogen

  4. Potassium


Correct Option: A
Explanation:

Energy flow is the amount of energy that flows from one trophic level to another trophic level in an ecosystem. It is unidirectional or one-way passage. In an ecosystem, flow of free energy occurs through different trophic levels. Producers or plants obtain their energy from the sun by photosynthesis. The primary consumers (herbivores) obtain their energy from the producers. The secondary consumers (carnivores) obtained their energy by using herbivores as a source of food and so on. The energy present at each successive trophic level is 10% of the previous trophic level.

Thus, the correct answer is 'Free energy.'

Path of energy flow in an ecosystem is 

  1. Herbivores > Producers > Carnivores -> Decomposers

  2. Herbivores > Carnivores >Producers > Decomposers

  3. Producers > Carnivores > Herbivores > Decomposers

  4. Producers >Herbivores > Carnivores > Decomposers


Correct Option: D
Explanation:

Ecosystem is made up of living and nonliving things. Living things or biotic things include plants and animals. Nonliving things or abiotic things include air, water, land.  It is composed of organisms interacting within communities. The driving force for an ecosystem is solar energy. Producers use solar energy to synthesize their food by the process of photosynthesis. From producers, the energy is transferred to herbivores. Herbivores eat producers. The energy is transferred from herbivores to carnivores. Carnivores eat herbivores. From carnivores, the energy is transferred to decomposers. They decompose organic matter of plants and animals.

Thus, the correct answer is 'Producers >Herbivores > Carnivores > Decomposers.'

Which of the following receives the maximum energy?

  1. Producers

  2. Decomposers

  3. Primary consumers

  4. Secondary consumers


Correct Option: A
Explanation:
Flow of energy declines as it passes from lower to higher trophic level. The energy decreases from one trophic level to the next trophic level because energy is lost as metabolic heat during transfer of energy. When food energy passes from producers to herbivores to carnivores, only 10% of energy is transferred from one trophic level to another trophic level. Hence, producers receives the maximum energy.
Thus, the correct answer is 'Producers.'

Each successive trophic level has

  1. Less total energy

  2. More total energy

  3. Increased total energy

  4. Non estimated energy contents


Correct Option: A
Explanation:

Pyramid of energy represents the amount of energy at each trophic level. In any ecosystem, flow of energy declines as it passes from lower to higher trophic level. Hence, the pyramid of energy is always upright. Each successive trophic level has less total energy. In this, the energy decreases from one trophic level to the next trophic level because energy is lost as metabolic heat during transfer of energy. When food energy passes from producers to herbivores to carnivores, only 10% of energy is transferred from one trophic level to another trophic level.

Thus, the correct answer is 'Less total energy.'

Loss of energy from one trophic level to next higher trophic level is

  1. 30%

  2. 40%

  3. 60%

  4. 90%


Correct Option: D
Explanation:

According to the Lindeman's trophic efficiency rule, the 10% of energy is transferred from one trophic level to the next successive trophic level. The rest of the energy, that is 90% of energy is lost during transfer of energy from one trophic level to next higher trophic level. The first trophic level has the maximum energy. 

Thus, the correct answer is '90%.'

Ten percent law of energy transfer in food chains was given by

  1. Elton

  2. Haeckel

  3. Lindeman

  4. Schimper


Correct Option: C
Explanation:

Ten percent law of energy transfer in food chains was given by Reymond LIndeman. It is also called as Lindeman's trophic efficiency rule. According to this rule, the 10% of transfer of energy is transferred from one trophic level to the next successive trophic level. The rest of the energy is lost during transfer of energy and during respiration. The first trophic level has the maximum energy. 

Thus, the correct answer is 'Lindeman.'

10% law of energy transfer in food chain was given by

  1. Elton

  2. Schimper

  3. Haeckel

  4. Lindeman


Correct Option: D
Explanation:

Ten percent law of energy transfer in food chains was given by Reymond LIndeman. It is also called as Lindeman's trophic efficiency rule. According to this rule, the 10% of transfer of energy is transferred from one trophic level to the next successive trophic level. The rest of the energy is lost during transfer of energy and during respiration. The first trophic level has the maximum energy. 

Thus, the correct answer is 'Lindeman.'

In a food chain, energy flows

  1. From low to high level

  2. From high to low level

  3. From low to middle level

  4. From middle to low level


Correct Option: A
Explanation:

In a food chain, energy enters through producers. Producers such as plants synthesize their own food in presence of sunlight. They convert solar energy into chemical energy. From producers, the energy flows to the primary consumers to the secondary consumers to the tertiary consumer. Hence, the energy flow in a food chain is always from low to high level. During energy transfer, only 10% of energy is transferred from one trophic level to another trophic level.

Thus, the correct answer is 'From low to high level.'

Lindemans energy transfer law states that only

  1. 20% energy is transferred to higher trophic level

  2. 10% energy is transferred to higher trophic level

  3. 30% energy is transferred to higher trophic level

  4. 50% energy is transferred to higher trophic level


Correct Option: B
Explanation:

Ten percent law of energy transfer in food chains was given by Reymond LIndeman. It is also called as Lindeman's trophic efficiency rule. According to this rule, the 10% of transfer of energy is transferred from one trophic level to the next successive trophic level. The rest of the energy is lost during transfer of energy and during respiration. The first trophic level has the maximum energy. 

Thus, the correct answer is '10% energy is transferred to higher trophic level.'

Which of the following statements regarding energy flow is/are false?
I. Detritus food chain begins with dead organic matter
II. In aquatic ecosystem, detritus food chain is the major conduit for energy flow
III. In terrestrial ecosystem a larger fraction of energy flows through grazing food chain
IV. Producers belong to the first trophic level of the food chain

  1. II and III only

  2. III and IV only

  3. I and IV only

  4. I and II only

  5. I, II and III only


Correct Option: A

The energy required daily by hunter- gatherer humans was:

  1. 2000 - 4000 kcal

  2. 6000 - 10000 kcal

  3. 10000 - 70000 kcal

  4. 10000 - 12000 kcal


Correct Option: A
Explanation:
  • A hunter-gatherer is a human living in a society in which most or all food is obtained by foraging (collecting wild plants and pursuing wild animals).
  • The energy required daily by hunter-gatherer humans was 2000 - 4000 kcal.
  • So, the correct answer is ' 2000 - 4000 kcal'.

As biomass passes from one trophic level to another, the amount of total energy

  1. Declines

  2. Increases

  3. Remains unaffected

  4. None of the above


Correct Option: A
Explanation:

Energy flow is the amount of energy that flows from one trophic level to another trophic level in an ecosystem. It is unidirectional. In any given ecosystem, flow of energy occurs through different trophic levels. Producers or plants obtain their energy from the sun by photosynthesis. The primary consumers (herbivores) obtain their energy from the producers. The secondary consumers (carnivores) obtained their energy by using herbivores as a source of food and so on. The energy present at each successive trophic level is 10% of the previous trophic level. Hence, as biomass passes from one trophic level to another, the amount of total energy declines.

Thus, the correct answer is 'Declines.'

In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of

  1. Heat energy

  2. Light energy

  3. Chemical energy

  4. Mechanical energy


Correct Option: C
Explanation:

In an ecosystem, the ultimate source of energy is sun and solar energy is trapped by photoautotrophs or green plants which then convert it into chemical energy which is stored in carbohydrates. This chemical energy in the form of food is passed on from one organism to another in a food chain in the ecosystem. 

Therefore, the correct answer is option C.

Bioenergetics can be defined as the process of energy transfer between trophic levels

  1. True

  2. False


Correct Option: B
Explanation:

  • Bioenergetics is a field in biochemistry and cell biology that concerns energy flow through living systems. 
  • This is an active area of biological research that includes the study of the transformation of energy in living organisms and the study of thousands of different cellular processes such as cellular respiration and the many other metabolic and enzymatic processes that lead to production and utilization of energy in forms such as adenosine triphosphate (ATP) molecules. 
  • That is, the goal of bioenergetics is to describe how living organisms acquire and transform energy in order to perform biological work. 
  • The study of metabolic pathways is thus essential to bioenergetics.
So the given statement is false.

Energy recycling is an important part of every ecosystem

  1. True

  2. False


Correct Option: B
Explanation:

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. Ecosystems maintain themselves by cycling energy and nutrients obtained from external sources. The low rate of energy transfer between trophic levels makes decomposers generally more important than producers in terms of energy flow. Decomposers process large amounts of organic material and return nutrients to the ecosystem in inorganic form, which are then taken up again by primary producers.

So the given statement is false.

Choose the correct answers from the alternatives given .
Which of the following forms of energy is not correctly matched?

  1. Kinetic energy fat molecules

  2. Kinetic energy: movement of muscles

  3. Chemical energy: glucose

  4. Potential energy ATP


Correct Option: A
Explanation:

Fats typically provide more than half of the body's energy needs. Fat from food is broken down into fatty acids, which can travel in the blood and be captured by hungry cells. Fatty acids that aren't needed right away are packaged in bundles called triglycerides and stored in fat cells, which have unlimited capacity. Fat is the body's most concentrated source of energy, providing more than twice as much potential energy as carbohydrate or protein (9 calories per gram versus 4 calories each per gram).

Kinetic energy comes into play when there is motion (for e.g. muscles) while fats are rather part of energy requirement during the static state of the body. Hence, fat molecules rather provide potential energy.
So, the correct option is 'Kinetic energy fat molecules'.

Choose the correct answers from the alternatives given .
Diffuse, disorganised forms of energy

  1. Are heat

  2. Increase entropy

  3. Are not usable to do work

  4. All of these


Correct Option: D
Explanation:

Entropy is the measurement of this disorder in energy, in which heat energy, is not usable, is considered disorganized. Thus, a system with a large amount of usable energy has low entropy, a system with little usable energy has high entropy. Based on the second law of thermodynamics, entropy will continually increase in the universe as energy becomes more and more disorganized.

So, the correct option is 'All of the above'. 

The energy flows from autotroph to the heterotrophs.

  1. True

  2. False


Correct Option: A
Explanation:
Energy flow always occurs from lower trophic level to a higher trophic level. According to Lindeman's law of trophic efficiency, about 10% of energy is transferred from one trophic level to the higher trophic level. Autotrophs are the producers. They occupy the first trophic level. Heterotrophs are consumers which occupy subsequent trophic levels as primary, secondary and tertiary consumers. Thus, energy transfer takes place from autotrophs to heterotrophs.
Hence, the statement given in the question is correct.
So, the correct answer is 'True'.

Ecosystem is not accepted by which law of thermodynamics ? 

  1. 1 st law

  2. Zeroth law

  3. 2 nd law

  4. 3rd law


Correct Option: A
Explanation:

First law of thermodynamics defines that the energy neither created nor destroyed but can only be transformed. Ecosystem is not accepted by the 1st law of thermodynamics because the energy is created.

So, the correct option is '1 st law'.

Energy of motion is also known as:

  1. Dynamic energy

  2. Kinetic energy

  3. Sensible heat energy

  4. Static energy


Correct Option: B

Two objects, A and B, have the same mass but the specific heat of A is larger than B. If both objects absorb equal amounts of energy,

  1. A will become warmer than B

  2. B will become warmer than A

  3. Both A and B will warm at the same rate

  4. A will get warmer, but B will get colder


Correct Option: B

Energy transformation through the food chain is

  1. Regular

  2. Comfortable

  3. Proposed

  4. Inefficient


Correct Option: D

What is an average incident energy?

  1. 3000kcal/m2/day

  2. 2000kcal/m2/day

  3. 5000kcal/m2/day

  4. 6000kcal/m2/day


Correct Option: A

The correct sequence of components through which energy may pass from initial source, through an ecosystem is

  1. Sun $\rightarrow$ Autotrophs $\rightarrow$ Heterotrophs $\rightarrow$ Environment $\rightarrow$ Space

  2. Space $\rightarrow$ Environment $\rightarrow$ Heterotrophs $\rightarrow$ Autotrophs $\rightarrow$ Sun

  3. Sun $\rightarrow$ Space $\rightarrow$ Environment $\rightarrow$ Heterotrophs $\rightarrow$ Autotrophs

  4. Sun $\rightarrow$ Space $\rightarrow$ Environment $\rightarrow$ Autotrophs $\rightarrow$ Heterotrophs


Correct Option: D
Explanation:

The energy flow starts from the sun. The light energy enters the space and then into the atmosphere. The energy in the atmosphere is captured by the plants which are autotrophs. Plants convert this light energy to chemical energy by photosynthesis. The food prepared by the plants is consumed by the heterotrophs. The heterotrophs are utilized by the decomposers.

So, the correct answer is option D. 

Energy transfer from one trophic level to another is

  1. 10%

  2. 5%

  3. 15%

  4. 20%


Correct Option: A
Explanation:

The amount of energy at each trophic level decreases as it moves through an ecosystem. As little as 10 percent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat. The efficiency with which energy or biomass is transferred from one trophic level to the next is called as the ecological efficiency. Consumers at each level convert on average only about 10% of the chemical energy in their food to their own organic tissue (the ten-percent law). 

Therefore, the correct answer is option A.

Flow of energy declines as it passes from lower to higher trophic level. This is explained by

  1. First law of thermodynamics

  2. Second law of thermodynamics

  3. Newtons second law

  4. Newtons third law


Correct Option: B
Explanation:

Flow of energy declines as it passes from lower to higher trophic level. This is explained by second law of thermodynamics. According to this law, the energy decreases from one trophic level to the next trophic level because energy is lost as metabolic heat during transfer of energy. When food energy passes from producers to herbivores to carnivores, only 10% of energy is transferred from one trophic level to another trophic level.

Thus, the correct answer is 'Second law of thermodynamics.'

Consider the components of a food chain producers $ \rightarrow\ $ herbivores $ \rightarrow\ $ carnivores $ \rightarrow\ $ top carnivores. Eventually what happens to all the energy passed from one element to the next?

  1. It recycles back to the producers

  2. It results in a much larger decomposer population

  3. It is dissipated into the environment.

  4. It is recaptured by another food chain


Correct Option: C
Explanation:

food chain can be described as a series of energy dilutors, the energy that fails to reach the next level being dissipated as heat or movement. Most of the energy contained in the food of animal consumers is used by them during the processes of food collection, digestion, and other essential metabolic activity.

So, the correct option is 'It is dissipated into the environment.'

The only requirement of an ecosystem is a constant input of energy that comes by the process of respiration

  1. True

  2. False


Correct Option: B
Explanation:

  • An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. 
  • Energy flow is the amount of energy that moves through a food chain. 
  • Energy that is not used in an ecosystem is eventually lost as heat. 
  • Energy is passed on from one trophic level to the next trophic level and each time some energy is lost as heat into the environment. 
  • This is due to the fact that each organism must use some energy that they received from other organisms in order to survive. 
  • The top consumer of a food chain will be the organism that receives the least amount of energy.
So the given statement is false.

Read the following statements carefully:
(I) Energy transfer in the biotic world always proceeds from the autotrophs.
(II) Energy flow in undirectional
(III) Energy availability is maximum at the tertiary level.
(IV) There is loss of energy from one trophic level to that other.
Select the relevant statements for the forest ecosystem.

  1. I, II and IV

  2. I, II and III

  3. I, III and IV

  4. II, III and IV


Correct Option: A
Explanation:
A forest ecosystem is formed by the community of organisms which live in a forest. The relevant statement for the forest ecosystem are:
I→ Energy transfer in the biotic world always proceeds from the autotrophs as the plants and the trees are the major producers. 
II→ Energy flow is unidirectional.
IV→ There is a loss of energy from one trophic level to the other as the law of energy transfer is applicable to this ecosystem.
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