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9.  Ecology Questions

1.  A student wanted to estimate the number of grasshoppers in 5km2 grass field near the school compound.

Using a sweep net he captured 36 grasshoppers. He used a red felt pen to mark the thorax of each insect before releasing back into the field. Three days later he made another catch of grasshoppers. He collected 45 grasshoppers of which only 4 had been marked with red mark.

 a) Name the above method used in the population estimation    b) Calculate the population of grasshoppers using the above data  

2.  What is the significance of the following in the ecosystem?

 a) Decomposers

 b) Predators

3.  Birds feed on grasshoppers that feed on grass.

 a) Draw a possible food chain from the above information

 b) Explain why the biomass of organisms decreases at each preceding trophic level.  

4.  Define the following terms:-

 (i) Autecology  ;  

 (ii) Biomass;

5.  State two most important factors that favour exponential growth of a population of gazelle

 in a park

6.  (a) Distinguish between habitat and niche.

 (b) Explain why Biomass of producers is greater than that of primary consumers in a balanced


(c) State two advantages of a biological control method over the chemical control method of

pests and parasites  

7.  Explain how oil as a pollutant may affect aquatic plants and animals?

8.  The diagram below shows part of a food relationship in an ecosystem:-









 (a) Name the food relationship above

 (b) How many trophic levels are shown in the diagram above?

 (c) State main source of energy in the ecosystem  

9.  Use the food web below to answer the questions that follow:-









 (a) Construct a food chain ending with crocodile as a quartenary consumer

 (b) Name the organisms in the food web hat has only one predator  

10.  50 black mice and 50 white mice were released in an area inhabited by a pair of owls. After

four months, the mice in the area were recaptured and only 38 black mice and only a white mice


(a) How would you explain these results?  

 (b) Name the theory of evolution that support the results in (a) above

11.  In a certain school Form three class did an experiment to estimate the number of Tilapia

 in their fish pond. 725 tilapia were netted marked and released.  

a) State the method used in this exercise  

b) Calculate the tilapia population.

c) State two assumptions made by the students during the investigation

12.  An investigation was carried out on a terrestrial ecosystem. The population sizes and species

 biomass were determined and recorded as shown in the table  
















  1. If these organisms had a feeding relationship, construct a simple food chain involving all the organisms
  2. Construct pyramid of numbers using the data provided above  
  3. State one disadvantage of using pyramid of number in expressing feeding relationships in ecological ecosystem  

13.  The figure represents a feeding relationship in an ecosystem  







 (a) Write down the food chain in which the Guinea Fowls are secondary consumers

 (b) What would be the short term effects on the ecosystem if lions invaded the area

 (c) Name the organism through which energy from the sun enters the food web

14.  Outline three roles of active transport in human body  

15.  Distinguish between community and population

16.  Describe how the belt transect can be used in estimating the population of a shrub in a

grass land

17.  A fish farmer wanted to know the number of fish in a pond. He collected 10 fish from the pond

and labeled each, by a tag label on its fin and returned the ten fish to the pond to mix with

other fish . When he later collected 50 fish from the pond, he found only four of them had labels

 a) Estimate the total number of fish in the pond (show your workings)

 b) What two assumptions are being made in this methods of estimating population  

18.  What is the importance of saprophlic fungi and bacteria in an ecosystem

19.  i) Name one main cause of global warming

What are the effects of global warming  

20.  Explain how saliva is important in digestion  

21.  Give a reason why two species in an ecosystem cannot occupy the same niche

Image From EcoleBooks.com22.  Below is a pyramid of numbers indicating trophic levels:-








 (a) What do you understand by the term trophic level?

 (b) Name the trophic level numbered 5 on the pyramid

 (c) Name Q  

 (d)What is the significance of the arrow R

23.  Two populations of the same species of birds were separated over a long period of time by an

 ocean. Both populations initially fed on insects only. Later, it was observed that one population

 fed entirely on fruits and seeds, although insects were available. Name this type of evolutionary


24.  To estimate the population size of crabs in a certain lagoon, traps were laid at random. 400 crabs

were caught, marked and released back into the lagoon. Four days later, traps were laid again and

360 crabs were caught. Out of the 360crabs, 90 were found to have been marked

 (i) Calculate the population size of the crabs in the lagoon

 (ii) What is the name given to this method of estimating the population size

25.  State the function of each of the following apparatus:

 (a) Pooter …

 (b) Sweep net …………

26.  State the role of the following apparatus in the study of living things.

 (a) Sweep nets.

 (b) Pooter.

 (c) Pit fall trap.

27.  Name three density dependent factors in an ecosystem.

28.  (a) What are the two main components of an ecosystem?

(b) Apart from mere observation of actual feeding suggest two methods that can be used

to determine the type of food eaten by animals

29.  The chart below represents a simplified nitrogen cycle.

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 What is represented by X, Y and Z?

30.  In an ecological study, a locust population and that of crows was estimated in a grassland area

 over a period of one year. The results were tabulated as shown below.













No. of Adult locusts x 102












Number of crows












Amount of rainfall












a) Draw a graph of population of locusts and crows against time  

 b) i) State the relationship between rainfall and locust population  

ii) Account for the relationship you have stated in b (i) above  

 c) What happens on the populations of locusts and crows in the months of January to March?

  Give a reason.  

 d) If the area of study was one square kilometer, state one method used to estimate the

  population of :-   i) Locusts

ii) Crows

 (e) (i) State the trophic levels of the (i) Locusts and (ii) crows  

(ii) Construct a simple complete food chain involving these organisms

 (f) If the locust were removed from the food chain, what would be its effect?

(g) Define biomass  

31.  Two species of antelopes were introduced into an ecosystem at the same time in equal numbers.

The graphs below show their relative numbers during the first eight years of their co-existence.

Study the graphs carefully and answer the questions that follow.

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a) i) Which species of antelope has better survival adaptations.  

ii) Give a reason for your answer above.  

b) i) Name the type of curves shown.

ii) Name the phases labeled PQ, QR, RS, ST

c) Explain the shape of the curve for the species of Antelope A between

i) Q and R.

ii) S and T.

 d) i) State the type of competition shown by the two species of antelopes.

ii) State any two symptoms of intraspecific competition in plants.

e) Suggest how the species B avoid competitive exclusion..

f) State any three adaptations that enable the antelopes to overcome predation.

g) State any two possible methods by which populations of the two antelopes’ species were


32.  Explain five abiotic factors that affect the ecosystem

33.  The data shown below was taken from Savannah grassland habitat. Examine it carefully and then

 answer the questions that follow:-  

 (a) Draw three food chains  

 (b) Draw a pyramid of numbers for a food chain with four trophic levels and indicate the trophic

  levels at which each member feeds

 (c) State the effect of removing the hunting dogs  

 (d) Why is it advisable to feed 100kg of grain to man instead of using it to fatten steers then

supply beef to human population?




















Hunting dogs

















34.  Study the following food web and answer questions that follow:  









 (a) (i) Name the organisms that occupy the second trophic level  

  (ii) What is the other name for the second trophic level

 (b) Write down two food chains from the food web that:

  (i) End with hawks as tertiary consumer

  (ii) End with hawks as quaternary consumer

 (c) Giving reasons state; (i) the organism with largest biomass       (ii) the organism with least biomass

35.  (a) Explain how food as a factor regulates the population of animals in an ecosystem

(b) Describe the flow of energy from the sun through the different trophic levels in an ecosystem

36.  (a) Describe how a population of grasshoppers in a given area can be estimated

(b) Describe how the belt transect can be used in estimating the population of a shrub in

a grassland

37.  The flow chart below represents a feeding relationship in an ecosystem









 (a) Name; (i) The producers in the ecosystem  

    (ii) Two organisms which are both secondary and tertiary consumers

  (b) State two short term effects of immigration of insects in the ecosystem.

 (c) Which organism has the least Biomass in the food web. Explain.

 (d) State three disadvantages of using synthetic pesticides over Biological control.

 (e) State the role of each of the following in an ecosystem;

  (i) Saprophytes  

  (ii) Leguminous plants

(iii) Explain the role of producers in an ecosystem

(f) Name one method that would be used to estimate the population of small fish in the


38.  How are leaves of mesophytes adapted to their functions?

 9.  Ecology Answers

1.  a) Capture –recapture method;

 b) Calculate the population of grasshoppers using the above data

FM x SC  = 36 x 45;  = 405;

MR = 4


2.  a) Help to breakdown dead organic matter hence reducing bulk; in the recycling of Nutrients;

 b) Regulate the predator – prey population;


3.  a) Grass___________ grasshoppers ____________ birds;

 b) Not all the energy is transferred from one trophic level to another; some is lost as heat, some

is used up during metabolism and some is lost when organisms die and decay;


4.  Autecology is the study of population / study of members of a species;

 Biomass is the quantity of matter of a given type of organisms at a given trophic level  

 Or the dry weight of an organism;


5.  – Availability / adequate food supply ;  

 – Absence of predations ;

– Absence of disease; (mark the first two pts


6.  (a) Habitat – physical location with asset of condition where an organism lives; while  

niche is the exact place where an organism occupy and its role in the habitat;

 (b) Producers have a greater biomass than primary consumers since they start the food chain.

  Inter-trophic energy losses occur in form of heat;

 (c) It is non-toxic; It’s organism specific;


7.  Reduce oxygen supply and hence suffocation and death of plants and animals, clog respiratory surfaces (gills and stomata) leading to death;


8.  (a) Food web;  

(b) Three;

(c) Sun


9.  a) Microscopic plants- mosquito larvae- small fish- large fish- crocodiles

 b) Large fish;


10.  a) Owl is nocturnal , white mice are easily seen and predated on, black mice camouflaged/ not

easily predated on;

 b) (Theory of) Natural selection;



11.  a) Capture recapture method

b)  i)  P = FM x SC


= 725 + 974;


= 5080;

Where FM – First marked

SC – Second recapture

MR – Marked recapture

P – Population  


 ii) – No fish moves in or out of the area between counts

 – The marked fish mix freely with other fish populations;

 – Marking does not expose the fish to predation

 – No variation in population size


12.  D A C B


(b) – Correct label;

– A,B same size;

– C-largest;

– D- smallest;  


13.  – Protects delicate internal parts from mage;

 – prevents excess loss of water (desiccating);

 – provides surfaces for attachment of body muscles / organs;


14.  a) Grass Grasshopper Guinea Fowl;

Grass Termites Guinea Fowl;

 b) – Leopards will decrease;

  – Gazelles will also decrease;

 c) Grass;


15.  Population — all members of one species occupying a particular habitat at a given time;

  Community — all organisms belonging to different species that interact in the same habitat;


16.  – lay down two ropes parallel to each other a meter apart; count the number of shrubs between

the two ropes at marked points; and record the number repeat the process several times;

Obtain average number calculate area of the belt transect.  


17.  a)  Population = FM X SC  


P = 10 X 50 = 500;

4   4

 = 125;

 b) No entry or exit of fish;

Tags did not influence the general behavior of fish


18.  – they decompose organisms; aid in nutrient circulation


19.  i) Accumulation of CO2 in the atom

 ii) Increase in environmental temperature

  • Eratic weather changes


20.  – Enzymes amylase digests starch to maltose

 – Mucus lubricates food


21.  Due to (stiff) competition for available resources which leads to elimination/exclusion;


22.  a)feeding level

 b)quaternary consumer;

  c)sun/source of energy;


23.  Adaptive radiation/divergent evolution;


24.  i)crab pop= number marked in 1st catch x total no. in 2nd catch  

Number marked(recaptured)in second catch.

= 400×360



 ii) Capture mark release recapture/

 Capture-recapture /capture release /recapture;


25. (a) Suck small crawling insects (from tree trunks):

(b) Catching (flying) insects in grass:


26.  (a) Used for the collection of flying specimens such as butterflies;

 (b) Used for sucking small insects from barks of trees and under stones;

 (c) Used for trapping crawling insects such as termites;


27.  1. Competition;  

 2. Emigration;  

 3. Predation;   4. Parasitism;  


28.  (a) Biotic and abiotic factors (2x ½ =1mk)

  (b) – Feacal analysis

  – Type of dentition type of beak  (2 x1=2mks)


29.  X – denitrifying bacteria/

 Y – Animals/ herbivores; accept primary consumers

 Z – Nitrogen fixing bacteria (in soil) accept Azotobacter


30.  a) Check graph  

  • Labelling axes;;
  • Scale
  • Plotting;
  • Joining (smooth contineas);
  • Identifying the graph;












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b)  i) The population of locusts increase with increase in that the amount of rainfall;

 ii) – Increased amount of food;

  • Improve breeding conditions;

c)  – The population of both decreases

 – Less food availability for locusts and hence crows;

d)  i) Quadrat method;

 ii) total counts

e)  i) locusts ____ primary consumers;

  Crows ______ secondary consumers;

 ii) Grass ____ Locusts ________ crows;

f)  – Grass would increase;

 – Crows would reduce;

g) Wild animals are browzers hence obtain food while cows are grazers hence lack grass

h) Biomass is the total dry weight of organisms at a particular trophic level


31.  (a) (i) Antelope A;

  (ii) Reason- Rate of multiplication /reproduction is higher in species A than B;

(b) (i) Sigmoid curve /ogive/s-shaped curve;

  Accept any one correct

 (ii) PQ- Lag phase /slow growth phase; QR- Exponential/log / rapid growth phase;

RS – Deceleration phase ST- Stationary/constant growth phase;

(c) (i) Q and R

Marked with rapid population growth rate; many mature reproducing organisms/individuals/antelopes;

  Absence of environmental resistance;

(ii) S and T – Growth rate stagnant/birth rate equals to death rate; the ecosystem has attained

its carrying capacity/environmental resistance (density dependent) have set-in;

(d) (i) Interspecific;

  (ii) Thin and tall; yellow/pale green; low yield

(e) By occupying different (ecological) niches;

(f) Move swiftly to escape predators; camouflage to avoid noticed by predators; Eyes on the

side of the head to give them a wide field of view enabling them to keep track of their enemies;

(g) Capture –recapture method,; direct count,

  Aerial photography


32.  Water- The availability of adequate amounts of water lead to plant growth which  

provides food for animals. In aquatic environment, wateris a medium in which gametes are released thus lead to continuity in procreation.

Temperature- Influences the rate of enzyme catalyzed reactions. Therefore, it exerts an influence on almost all activities of plants and animals such as respiration, photosynthesis, growth, transport e.t.c.

Light-Is necessary in plants for photosynthesis as it influences flowering of a wide variety

of plants, affecting opening and closing of stomata, affect the rate of transpiration.

Salinity- Is the salt content of eater. It varies in aquatic habitat. Fresh water organisms suffer the

risk of loosing water.

Humidity – Determines the amount of water loss from a bodies animals and organs of plants;

high humidity means less evaporation; and low humidity means high rate of

evaporation and transpirations;

pH – It determines if water habitat is acidic or alkaline; PH has a great influence on

physiological function of organisms affects enzyme concern reactions since

enzymes operate within a narrow pH ranges

Wind– Wind came physical damage to plants; increase rate of transpiration as air blows

away; causes migration of insects; wind having gases may acid rain in a region;

wind is an agent of pollination and dispersal;

33.  (a)

Grasses   Caterpillar  Frogs   Snakes Hawk

Grasses   Squirrel  Hunting dogs Hawk Vulture

Grasses   Elephant   Vultures

Grasses   Caterpillar  Snake Hawk


 (b)  Pyramid of numbers.
















 (c)  Effects of removing the hunting dogs.

– Increase in number of gazelles and squirrels due to reduced predation leading to

increased pressure upon the grass;  

(d)   During transfer of energy at each feeding level, some amount of energy in form of heat is

lost only about 10% would be transferred from the grains to steers and out of the 10 %

about 1 kg would be transferred to man. The rest would be lost as heat or ingestible



34.  a) i) Slugs; mice;/ Amphids/ caterpillar  

 ii) Primary consumers;


 b) i) plants _________ mice _______ snakes __________ Hawks;


Plants ________ Caterpillar ________ insectivorous birds _______ hawks


 c) Plants _________ directly obtain energy from the sun


 Hawks – Loss of energy in form of heat; through process of respiratal/ defaecation/ excretion


35.  a) A lot of food causes population increase due to high rate of reproduction and immigration resulting in completion for food/ death/ emigration; reducing population; little food leads to competition; leading to emigration/ death; reducing population

b) Energy from the sun is trapped by green plants; during photosynthesis; producing chemical energy/ carbohydrates/ food

Green plants are producers/ 1st trophic level Green plants are eaten by herbivores which are primary consumers/ occupy the second trophic level, when plants dies and animals die organisms die; saprophytic fungi/ bacteria/ micro organisms feed on them; thus decomposing them into smaller/ simpler substances/ they are decomposers/ detritivores; At all levels some energy is lost; through respiration


36.  a)  A- Ovary  

B- Oviduct/ fallopian tube

C- Uterus/ uterine wall

D- Cervix

 b)  Produce ova

Produce femme hormones/ Estrogen and progesterone

 c)  – Highly vascularized to supply nutrients to foetus/ drain away excretory wastes

– Inner wall lined with Endometrium for implantation of fertilized egg/ zygote

– Muscular for peristalisis to expel menses during menstruation/ parturition

– Great capacity to expand during gestation to accommodate developing foetus

 d)  -copulation/ Achieve orgasm in Human male followed by ejaculation

– birth canal


37.  a) use the capture -recapture method; capture the grass hoppers; count; and mark using

permanent ink; record; releases; and allow time(1-24hrs);recapture and count the marked and unmarked;

Total population is equal to the number marked and unmarked grasshoppers in the second sample X number of marked grasshoppers in the first sample divided by number of grasshoppers marked in the second sample that were recaptured;

Acc P= FMxSC


where FM-1st captured

SC-2nd capture(marked and unmarked

MR-marked recaptured

(rej. ½ mark i.e. 10/2=5) acc specified distance apart e.g. 3m apart

b. run two ropes parallel to each other a meter apart; counts of shrub are made between the two ropes at marked points/whole belt (and recorded);report the process severally(at least 3 times);calculate shrub area of the belt transect; calculate shrub population for whole area;

Rej all shrubs counted

NB shrub pop=average shrubs per transect x total area of grassland

Average area of belt transect (max 3)


38.  (a) (i) Phytoplanktons:

(ii) Hawk; and water snake:

(b) – Decrease in phytoplanktons:

– Increase in population of small fish:  

(c) Hawk;- Top predator amount of energy decreases in successive trophic level/energy is lost

through respiration; undigested/unconverted food:

(d) Residue is poisonous to man;

-Kill non- targeted organism / Beneficial organisms:

-Remains for along time in the ecosystem / pollutes environment:

(e) (i) Causes decomposition/Recycling of nutrients:

(ii) Root nodules: have bacterial / Rhizobium sp: to convert free nitrogen: into nitrates in the


(f) Capture – recapture: capture release recaptures:

(g) Manufacture food: (OWTTE) to be used by themselves: and all other organisms in the

ecosystem ( awls)


39.  Broad/ wide lamina: to Provide a large surface area to trap maximum sunlight or


– Thin lamina; to reduce the distance covered b\ light and carbon (iv) oxide: to reach the

photosynthetic cells/ palisade cells;

– Cuticle; is transparent to allow light reach photosynthetic cells:

– Waterproof climatic cuticle: to reduce water loss/Transpiration:

– Numerous stomata: efficient gaseous exchange: palisade (mesophyll) cells: have numerous

chloroplasts: for maximum photosynthesis: spongy mesophyll cells: are irregular in shape

creating large air spaces between: for efficient /free circulating air; Lear veins; have x 1cm 1r

transport of water and mineral salts: and phloem for transport of manufactured food;

– Leaf mosaic: to maximum trapping of sunlight for photosynthesis:

– Guard cells: to control opening and closing stomata: Guard cells have chloroplasts for




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EcoleBooks | 9. 	Ecology Questions And Answers


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