CBSE Class 12 Biology HOTs Ecosystem

Question. A bear that eats a fish that further ate bugs that ate lgae is a
(a) primary producer
(b) primary consumer
(c) secondary consumer
(d) tertiary consumer
Answer : D

Question. Fill up the blanks.
I. Animals which feed directly on plants, are called …A….
II. Consumers that feed on primary consumers are called …B….
III. In an ecosystem two laws of thermodynamics govern the…C….
Choose the correct option for A, B and C.
(a) A–herbivores, B–carnivores, C–flow of energy
(b) A–autotrophs, B–heterotrophs, C–trophic level
(c) A–photosynthesisers, B–higher levels predators, C–flow of energy
(d) A–predators, B–grazers, C–trophic level
Answer : A

Question. Which of the following two organisms are producers?
(a) Plants and phytoplanktons
(b) Plants and consumers
(c) Zooplanktons and phytoplanktons
(d) Phytoplanktons and chlorophylls
Answer : A

Question. To show how many organisms are present at each level of a food chain, ecologists use a model called
(a) an energy flow pyramid
(b) pyramid of numbers
(c) pyramid of energy
(d) food chain/food web pyramid
Answer : B

Question. How many trophic levels human beings function at in a food chain?
(a) 1
(b) 2
(c) 3
(d) 4
Answer : C

Question. The upright pyramid of number is absent in
(a) pon
(b) forest
(c) lake
(d) grassland
Answer : B

Question. A sequence of species or organism through which the food energy pass in a community is called
(a) pyramid of energy
(b) food chain
(c) food web
(d) nutrient cycle
Answer : B

Question. Energy enters in any ecosystem through
(a) herbivores
(b) carnivores
(c) producers
(d) decomposers
Answer : C

Question. Energy flow in an ecosystem is
(a) unidirectional
(b) bidirectional
(c) multidirectional
(d) All of these
Answer : A

Question. The green plants in an ecosystem which can trap solar energy to convert it into chemical bond energy are called
(a) producer
(b) decomposer
(c) consumer
(d) predators
Answer : A

Question. Food chain refers to
(a) number of humans forming a chain for food
(b) animals gathered near a source of food
(c) transfer of energy from producers to consumers
(d) None of the above
Answer : C

Question. Food chain starts with
(a) N2-fixation
(b) osmosis
(c) respiration
(d) photosynthesis
Answer : D

Question. Food chain consists of
(a) plants
(b) herbivores
(c) carnivores
(d) All of these
Answer : D

Question. In grazing food chain, energy comes from
(a) organic remain
(b) sun
(c) water
(d) All of these
Answer : B

Question. …… starts with green plants called producers as the first trophic level. The most appropriate choice for filling blank space is
(a) detritus food chain
(b) grazing food chain
(c) complex food chain
(d) normal food chain
Answer : B

Question. A much larger fraction of energy flows in a terrestrial ecosystem through
(a) grazing food chain
(b) detritus food chain
(c) complex food chain
(d) food web aquatic ecosystem
Answer : B

Question. Which food chain correctly describes the flow of energy in an ecosystem?
(a) Grass→ cow→ human
(b) Caterpillar→ leaf→ human
(c) Cow→ grass→ human
(d) Leaf→ bird→ caterpillar
Answer : A

Question. A much large fraction of energy flows in an aquatic ecosystem through
(a) grazing food chain
(b) detritus food chain
(c) complex food chain
(d) food web
Answer : A

Question. In what order do a hawk, grass and rabbit form a food chain in a meadow?
(a) Hawk→ grass→ rabbit
(b) Grass→ hawk→ rabbit
(c) Rabbit→ grass→ hawk
(d) Grass→ rabbit→ hawk
Answer : D

Question. Which of the following organisms in the given food web act as a secondary consumers?(image 72)
(a) I and IV
(b) V and VI
(c) III and VI
(d) IV and VII
Answer : C

Question. A person who eats a chicken that ate grain is a
(a) primary producer
(b) primary consumer
(c) secondary consumer
(d) quaternary consumer
Answer : C

Question. Vegetable eating person acts as
(a) primary producer
(b) primary consumer
(c) secondary consumer
(d) tertiary consumer
Answer : B

Question. What is common characteristic of earthworm, soil mites and dung beetle of an ecosystem?
(a) Primary producer
(b) Primary consumer
(c) Secondary consumer
(d) Tertiary consumer
Answer : B

Question. Which of the following organisms in the given food web (fig of Q. 72) acts as a primary consumers?
(a) II, IV and V
(b) I, II and III
(c) II, III and IV
(d) IV, VII and VIII
Answer : A

Question. Energy for the detritus food chain comes from
(a) organic remain
(b) air
(c) radiation
(d) water
Answer : A

Question. …… begins with dead organic matter and saprophytes make the first trophic level. Most appropriate word for filling blank space is
(a) Detritus food chain
(b) Grazing food chain
(c) Complex food chain
(d) Normal food chain
Answer : A

Question. The organisms, which attack dead animals are
(a) first link of the food chain and are known as primary producers
(b) second link the food chain and are herbivorous
(c) third link of the food chain and are tertiary consumers
(d) present at the starting of food chain and are detritivores
Answer : D

Question. Select the incorrect food chain.
(a) Grass→ Frog→ Vulture
(b) Grass→ Grasshopper→ Frog→ Snake→ Eagle
(c) Grass→ Deer→ Lion
(d) Phytoplankton→ Zooplankton→ Fish (perch)→ Fish (bass)→ Man
Answer : A

Question. Identify the possible link ‘A’ in the following food chain.
Plant→ Insect→ Frog→ ‘A’→ Eagle CBSE-AIPMT 2012
(a) Rabbit
(b) Wolf
(c) Cobra
(d) Parrot
Answer : C

Question. The mass of living material at a trophic level at a particular time is called CBSE-AIPMT 2015
(a) gross primary productivity
(b) standing state
(c) net primary productivity
(d) standing crop
Answer : D

Question. The 10% law is related to
(a) Mendelian genetics
(b) non-Mendelian genetics
(c) energy transfer from lower trophic level to higher trophic level
(d) energy consumption during photosynthesis in C4-plants
Answer : C

Question. The 10% law for energy transfer in food chains was given by
(a) Stanley
(b) Tansley
(c) Lindemann
(d) Weismann
Answer : C

Question. What percentage of herbivore’s chemical energy is transferred to the chemical energy within the carnivore tissue?
(a) 100%
(b) 50%
(c) 1%
(d) 10%
Answer : D

Question. Suppose 2000 J of solar energy is incident on green vegetation. On the basis of 10% law of Lindemann. Identify A, B and C.
(a) A – 20 J, B – 2 J, C – 0.2 J
(b) A – 200 J, B – 20 J, C – 2 J
(c) A – 400 J, B – 40 J, C – 4 J
(d) A – 40 J, B – 4 J, C – 0.4 J
Answer : A

Question. The tiger is left with 10J of energy in a grass–deer–tiger food chain. The energy available at grass level is
(a) 100 J
(b) 2000 J
(c) 1000 J
(d) 10,000 J
Answer : C

Question. If 20 J of energy is trapped at producer level, then how much energy will be available to peacock as food in the following food chain? Plant→ Mice→ Snake→ Peacock
(a) 0.02 J
(b) 0.002 J
(c) 0.2 J
(d) 0.0002 J
Answer : A

Question. The relation between producers and consumers in an ecosystem can be graphically represented in the form of a pyramid called
(a) ecological pyramid
(b) trophic level
(c) Pi chart
(d) pyramid of biomass
Answer : A

Question. A food web
(a) is more real than food chain
(b) consists of a number of food chains interlinked at various trophic levels
(c) provides a number of alternate food to consumers
(d) All of the above
Answer : D

Question.  How many food chains are there in the food web shown below?(image69)
(a) 2
(b) 3
(c) 5
(d) 7
Answer : C

Question. Identify A, B and C from the given flowchart.(image70)
(a) A–Bulbul, B–Snake, C–Monkey
(b) A–Beetle, B–Lizard, C–Praying mantis
(c) A–Ladybird, B–Snake, C–Hawk
(d) A–Lizard, B–Bird, C–Snake
Answer : C

Question. In ecological pyramid, the base always represents the …A… and the apex represents …B… . Here, A and B represent.
(a) A–producers, B–top level consumers
(b) A–top level consumers, B–producers
(c) A–producers, B–secondary consumers
(d) A–producers, B–primary consumers
Answer : A

Question. Which of the following ecological pyramid are always inverted?
(a) Pyramid of number in parasitic food chain and pyramid of biomass in pond ecosystem
(b) Pyramid of number in pond ecosystem and pyramid of biomass in pond ecosystem
(c) Pyramid of number in pacific food chain and pyramid of number in pond ecosystem
(d) All of the above
Answer : A

Question. Given below is one of the types of ecological pyramids. This type represents (image96)
(a) pyramid of number in a grassland ecosystem
(b) pyramid of energy in forest ecosystem
(c) pyramid of biomass in sea ecosystem
(d) pyramid of biomass in terrestrial ecosystem
Answer : A

ECOSYSTEM

Q.1) How does the man made ecosystem differ from the natural ecosystem? 

Ans1) Man made ecosystem Natural ecosystem Under regular control not under the control of man And monitored by man

Q.2) Detritus contribute to the biogeochemical cycles, how? 1

Ans2) By the decomposition of detritus, the simple minerals are released into the atmosphere & from there it come back to the earth.

Q.3) Can temperature regulate the rate of decomposition how? 1

Ans3) High temperature favours decomposition and low temperature inhibits decomposition.

Q.4) The detritus food chain and grazing food chain differ. How? 1

.Ans4) Detritus food chain begins from the dead and decaying matter while grazing food chain starts from the green plants(Producers).

Q.5) "The Green Revolution has been achieved due to the use of improved crop varieties and agrochemicals, but it is still not enough to feed the growing population". Suggest a suitable method of agriculture to meet the demand. 1

Ans5) Vegetation changes in turn change the food and shelter for various types of animals. As a result the foresaid changes happen.

Q.6) A species of Solanum is intolerant to salty soil. How will you make the species tolerant to the given abiotic stress?. 1

Ans6) In burnt out forests and flooded lands some soil or sediment is present. There is no need for soil to be formed.

Q.7) Why do we use GM to create tailor made plants?. 1

Ans7) The reservoir of gaseous cycle exists in the atmosphere and for the sedimentary cycle it is located in earth's crust.

2 marks

 

Q.5) Given below is a simplified model of phosphorus cycle. Write down the natural reservoir of phosphorus and also the processes that put in phosphorus tothe soil.

Ans5) A. Rock minerals B. Weathering C. Decomposition

3 MARKS

Q.1). The following is the diagrammatic representation of decomposition cycle in a terrestrial ecosystem, answer and complete the cycle.

Answer: A- Green leaves

             B- Eaten by insects

             C- Bacteria and Fungi

             D- Soil earthworms and Bacteria

 

Q.2) Mark the producer, primary consumer, secondary consumer and tertiary consumer of a grassland ecosystem of the following.

 

GRASS SNAKE HAWK GRASSHOPPER

 

Q.3). Find out the consumer of top order/ top carnivore from the following food chains. Why?

 

a) Phytoplankton → small fishes → large fishes  → Hawk

 

b) Phytoplankton →  Zooplankton  →  Fishes  →  Man

 

Answer: (a). Hawk

(b). Man

 

Q.4)Write the probable primary consumer and top consumer of the following ecological pyramid.

 

5) Based on the following information, answer the A, B, C and D with reference to Grass land ecosystem.

 

Q.6).In terrestrial ecosystem DFC and GFC are interlinked at certain level. Jusify the statement.

 

Hint: GFC-PREY to DFC

 

Q.7). Which stage is common between hydrarch and xerarch succession?

 

Ans: Climax forest

 

Q.8). Why food chain in the environment operative in the form of food web?

 

Ans: (i )Omnivorous nature

       (ii ) One animal depends on many types of animal for food.

 

Q.9). Complete the steps of decomposition process by using a suitable terminology in a &b.

 

Answer : a-Fragmentation

b- humification

 

Q.10) Complete the following simplified schematic diagram of Phosphorous cycle by writing the correct answer for ‘A’, ‘B’, ‘X’ and ‘Y’.

 

Q.11) Why are all the pyramids upright in most of the ecosystems?

 

Ans: Energy at the lower trophic level is more than at higher trophic level.

 

Q.12. Why pyramid of energy is always upright and can never be inverted?

 

Ans: Some amount of energy is lost during its transfer from one trophic level to the next.

 

Q.13. Tree Birds Parasites Draw a ecological pyramid by using the above food chain.

 

Q.14. How human activities can significantly influence the carbon cycle?

 

Q.15. Why ecosystem services are more essential nowadays?

 

Q.16. In a simple ecosystem, there exists a field of clover. Mice eat the clover and skunks eat the mice. The skunks are in turn eaten by wolves. If 10,000 calories are available from clover plants, how much energy would each of the organism in the food chain receive.

 

Q.!7. In the pyramid of biomass drawn name the two crops.

(i) One which is supported.

(ii) One which supports.

(iii) In which ecosystem is such a pyramid found.