ECOLOGY

1. Name the symbiotic relationship that exists between fungi and roots of certain plants.

ANSWER:Mycorrhizae

2. Name the symbiotic association that exists between certain fungi and algae.

ANSWER: Lichen

3. Name the type of association between two organisms in which one benefits and the other
neither benefits nor gets harmed.

ANSWER: Commensalism

1. Explain the term, “Biomass”.

ANSWER: It refers to a mass of naturally grown plant and animal materials
that can provide useful energy.
2. There are two known forms of biomass fuels, what are they?
ANSWER: Biogas and ethanol / alcohol.
3. How is biogas produced?
ANSWER: From anaerobic decomposition of organic waste (e.g. human and
animal manure)
1. What name is given to the rapid growth of populations of algae in either freshwater or
saltwater environments?
ANSWER:Algal bloom / Red tide
2. What name is given to an increase in the growth of algae due to the buildup of nutrients in a
lake or pond?
ANSWER: Eutrophication
1. What name is given to the process by which soil is formed?
ANSWER: Weathering

2. What name is given to soil water that adheres so closely to the soil that it can hardly be
absorbed by roots of plants?
ANSWER: Hygroscopic water

3. Name the type of soil that is formed by the action of decomposers.

ANSWER: Humus

1. The thin shell of air, land and water around the earth that supports life is known as
 ANSWER: Biosphere

2. An organism’s modification in structure, function or behaviour, to suit the environment is

known as
ANSWER: Adaptation

3. A biological community together with the associated abiotic environment is known as

ANSWER: Ecosystem
1. Name the type of relationship that exists between a herbivore and the bacteria that lives in
its caecum.
ANSWER: Mutualism
2. What name is given to terrestrial organisms that are capable of maintaining a constant
body temperature within fairly close limits.
ANSWER: Homoiotherms
3. What name is given to the use of predators to control pests in a farm?
ANSWER: Biological control

Name the type of association that exists between the following organisms.

1. Mistletoe and orange

ANSWER: Parasitism
2. Toad and butterfly
ANSWER: Predation
3. Remora fish and shark
ANSWER: Commensalism
1. What name is given to populations of different species that live together and interact with
each other?
ANSWER: Community
2. What name is given to a number of interconnected food chains that present a complete
picture of feeding relationships in an ecosystem?
ANSWER: Food web
3. What name is given to a particular locality within an ecosystem where an organism can
live successfully and reproduce?
ANSWER: Habitat
 1. What name is given to water that is physically bound to soil particles and is
unavailable to plants?

ANSWER: Hygroscopic water

2. What name is given to water that drains out of pore spaces in the soil after rainfall?

ANSWER: Gravitational water.

3. What name is given soil water that is held against the force of gravity in pores of the
soil?

ANSWER: Capillary water

1. The nutrition of some plants depend on root-bacterium association known as

ANSWER: Root nodules

2. The nutrition of some plants depend on root fungus association known as

ANSWER: Mycorrhiza
3. What name is given to the association between some fungal species and algae.

ANSWER: Lichens
1. A quadrat can only be used successfully to sample vegetation and not animals. Why?
0ANSWER: This is because animals are mobile and can therefore easily escape
beyond the boundaries of the quadrat.
A. About 80% of energy fixed by producers is lost to consumers. Where does this energy
ultimately go? [1attempt]
ANSWER: It goes to decomposers
B. What percentage of light energy is converted to potential chemical energy through
photosynthesis? [1attempt]
Answer: 1%
. Distinguish between detritus food chain and grazing food chain with respect the following

1. The source of energy for the food chain

In detritus food chain, the source of energy is dead organic matter (detritivore)
whereas the sun is the source of energy for the grazing food chain

2. Length of the food chain

The detritus food chain is generally shorter than a gazing food chain

3. Primary consumers
In detritus food chain, the primary consumers are 'detritivores' (protozoans,
bacteria, fungi/saprophytes) whereas herbivores/plant eating organisms are the
 primary consumers in a grazing food chain

1. In a certain food web, sheep and grasshoppers both feed on grass. Which trophic level
do the grasshoppers belong?
Primary consumer / Second trophic level

2. A certain insect eat plants. If the plants are producers what is the insect classified as?
Primary consumer

3. In which trophic level can one place an algae?

Primary producer / 1st trophic level

1. The ability of a population of living species to increase under ideal environmental

conditions, that is, sufficient food supply, no predators, and a lack of disease.
Biotic potential

2. Activities which contribute to an individual's reproductive success and is thus subject

to the forces of natural selection
Adaptive behaviour

3. The maximum number of a given species that can be sustained by resources in a given
environment
Carrying capacity

Mention the specific type of heterotrophic nutrition exhibited by the following organisms.
1. Mistletoe
Parasitism

2. Ferns
Epiphytism

3. Lichens
Mutualism / Symbiotism

Mention one parameter each used to measure growth in plants

1. Height/length
2. Dry weight
3. Number of individuals
4. Volume / Girth
5. Leaf area of plant

Explain the following types of competition in terms of what they compete for
1. Consumptive or exploitative competition
Organisms compete for a resource such as food or building materials
(A competitor harvests a limiting resource; which limits the supply that other
 organisms need to survive that is incapable of harvesting resources at a much rapid
pace)

2. Interference competition
One organism prevents other organisms from using the resource
(A competitor Physically deprive other organism's access to resources. )

3. Preemptive competition.
When they compete for new territory by arriving there first.
(A competitor recruits to and dominates a habitat, monopolizing all available space,
preventing the establishment of potential competitors

1. Name the first step in carrying out ecological studies in a terrestrial habitat
ANSWER: Mapping the area
2. What name is given to a situation where only specified trees in a forest reserve are cut
down?
ANSWER: Selective exploitation
3. A farmer cultivating leafy vegetables will require fertilizers with a relatively high
content of which mineral?
ANSWER: Nitrogen
1. Which abiotic factor determines the depth to which light penetrates a pond?
ANSWER: Turbidity

1. What name is given to the first organisms to inhabit a previously uninhabited area?
ANSWER: Pioneer community

2. What name is given to the final stable community which is most productive and can
be sustained by the environment?
Answer: Climax community]

1. In the following questions, you are given a set of derived units. Give the
corresponding S.I It is generally better to feed many people with primary producers
rather than with consumers. Why do you think this is so?
ANSWER: This is because energy is lost at each trophic level of a food chain.

2. Even though it is generally better to feed many people with primary producers rather
than with consumers, there is a limitation in the feeding of people with only primary
producers. What is this limitation?
ANSWER: Primary producers i.e. plants do not have all the essential amino
acids that humans need (also plants have cellulose which is not digested).
1. Which group of organisms are most helpful in preventing the surface of the earth from
being covered with the bodies of dead organisms?
ANSWER: Fungi and bacteria (decomposers)

2. Which group of organisms would most likely be found at the top of a pyramid of energy?
ANSWER: Carnivores

3. Which group of organisms are most likely to be found at the bottom of a pyramid of
numbers?
ANSWER: Producers
4. What is normally the first line of defense of most prey against predators?
To avoid being detected by the predator.

1. Lichens are made up of a fungus in a mutualistic relationship with an alga. What

benefit does the alga obtain from the relationship?
Minerals and protection

1. Holes created in big trees by woodpeckers serve as shelter by squirrels. What type of
ecological association exist between the squirrel and the tree?
Commensalism

1. PREAMBLE: State one difference each between a grazing food chain and a detritus
food chain
ANSWERS:
1. Grazing food chain starts from the living green plants i.e. producers
occupying the first trophic level, but Detritus starts from the dead organic
matter and decomposers called detritivores as the first trophic level.
2. A much less fraction of energy flows through grazing food chain whereas
a much larger fraction of energy flows through this detritus food chain.
3. Grazing food chain binds inorganic nutrients but detritivore food chain
releases the inorganic nutrients bound in organic matter.
4. Grazing food chain is directly dependent on the inflow of solar radiation.
Whereas in detritivore Energy for the food chain comes from the organic
wastes, exudates and dead matter termed as detritus.
1. Species that share the same habitat and have similar needs frequently use resources in
somewhat different ways so that they do not come into direct competition for at least part
of the limiting resource. What name is given to this?
ANSWER: Resource partitioning
 2. What name is given to the set of resources and habitats that an organism could
theoretically use under ideal conditions?
ANSWER: Fundamental niche
3. What name is given to the set of resources and habitats that an organism actually uses?
ANSWER:Realized Niche
PREAMBLE: Give the type of association that exists between the following organisms
1. Anemone fish that lives in the tentacles of sea anemone.
ANSWER:Commensalism
2. Ant colonies that harbour rove beetles.
ANSWER:Commensalism
3. Branches of timber trees falling underneath shrubs.
ANSWER:Amensalism
1. Territoriality occurs in animals as result of which ecological relationship?
Competition

1. What is the difference between ecological succession and zonation?

Succession refers to the change in a community of organisms in a habitat over
time, whereas zonation refers to the appearance of distinct zones or regions in a
habitat at one time, where different communities of organisms live - due to the
different conditions in those zones.

1. Why is the intensity of natural selection on prey species higher than that of predators
throughout evolution?
The selection pressure on the prey is probably higher than that on the predator
because if a predator fails in its attempt to catch a prey it just misses one meal,
however, if a prey fails in its attempt to escape from a predator, it loses its life.

1. If a lion was hunting, it would want to find food that would give it more energy from
eating the food than it would spend hunting for the food. What name is given to this
process?
Efficient foraging/economical foraging

Fill in the blank with the appropriate word or phrase

1. The total amount of energy that plants assimilate by photosynthesis is called…..

ANSWER: Gross Primary Production

2. Two organisms that use resources when the resources are in short supply are said to be
………
ANSWER: Competitors

3. The number of individual species per unit area is known as ……….

 ANSWER: Population density

Give one of the main feeding tactics used by animals.

ANSWERS:
a) Filter feeding / suspension feeding
b) Deposit feeding / scavenging
c) Herbivory / Grazing
d) Predation

PREAMBLE: Explain the following:

1. Habitat – A place where an organism can live and interbreed

successfully

2. Population - The total number of organisms of a particular species living

in a habitat

3. Community - Refers to all the populations of all the different species in a

Habitat

1. What is the best description of a food web?

ANSWER: complex feeding relationship consisting of interrelated food
chains
2. What do you understand by the tolerance of an organism?
ANSWER: The survival range of an organism under unfavourable
ecological conditions
1. Which of the following best describes the complex relationship between the members of a
community and between the community as a whole and its physical environment?
ANSWER: Habitat. B Environment C. Niche D Ecosystem
Ecosystem

: A meal consists of three items. Explain how each item is ultimately the product of
photosynthesis.
1. The tilapia
ANSWER: The tilapia eat floating aquatic plants and filamentous algae which make
their food by photosynthesis
2. Potatoes
ANSWER: Potatoes are stem tubers containing food which the potato plant made in
its leaves by photosynthesis
3. Mushrooms
ANSWER: Mushrooms feed on decaying organic matter which comes from dead
plants which had made their food by photosynthesis OR
Feed on remains or faces of animals which fed on plants, or on animals which ate
plants which photosynthesised.
State whether the following are density dependent or density independent factors.

1. Flood
ANSWER: Density independent

2. Water
ANSWER: Density dependent

3. Food
ANSWER: Density Dependent

1. Name one climatic factor each that influences the development, distribution and
behaviour of organisms in an aquatic habitat.
ANSWER:

a. Temperature
b. Rainfall.
c. Hydrogen ion concentration (pH)
d. Salinity
e. Turbidity
1. Give one example each of how thermal pollution affects water and aquatic life.
ANSWERS:
a. The heated water released into the water bodies has less oxygen, thus, thermal
pollution leads to de-oxygenation of the water bodies.
b. Fluctuations in the amount of dissolved oxygen (DO).
c. The absence of oxygen leads to death of aquatic organisms.
 d. High temperature of water results in a decrease in the enzymatic activity.
Hence, the primary productivity of the water body decreases.
e. Thermal pollution affects fish population by disturbing reproduction.
f. Metabolic activity of aquatic organisms is affected

1. What are the two primary sources of excessive nitrate and phosphate in rivers and lakes?
ANSWER: From sewage effluents and intensive agriculture.
1. Which of the following relationships involves only one organism?
ANSWER: Epiphytism B. Mutualism C. Parasitism D. Saprophytism

1. Give one effect each of eutrophication on water and aquatic life.

ANSWERS:
a) Organic matter and nutrients that cause eutrophication promote the growth of bacteria
in water bodies.
b) The Nitrates and organic Phosphates also promote the growth of Algae in the water
bodies.
c) Bacteria use more oxygen quickly from the water which increases biological oxygen
demand. (B.O.D.)
d) The death of Algae and nutrients promote more growth of decomposing bacteria.
e) Such water becomes foul and unfit for fishes and other aquatic animals.
f) Aquatic animals die, more decomposition takes place leading to more growth of
decomposing bacteria.

1. How does taxism differ from tropism.

ANSWER:In taxism, the whole organism is affected whereas in tropism only part of
the
organism is affected.
2. What name is used to describe the physical space occupied by an organism together with
its functional role in a community?
ANSWER: Niche
3. Name the natural process that can convert atmospheric nitrogen to soil nitrogen
ANSWER:Lightning
1. Mention two (2 ) factors which might affect an animal living at the bottom of the sea.
ANSWER: Light, Water pressure, Salinity.
2. Mention two (2) abiotic factors which might affect a plant growing on mountains.
ANSWER: Temperature, wind speed, drainage of water, light intensity
3. Give two examples of artificial ecosystems.
ANSWER: Agricultural land, fish farms, Parkland, orchards.
PREAMBLE: State whether the following are structural, physiological or reproductive
specialization of parasites.

1. Reduction of sensory organs associated with the constancy of the parasite’s environment.
ANSWER: Structural

2. Production of digestive enzymes to aid penetration into the host.

ANSWER: Physiological

3. Absence or degeneration of feeding and locomotory organs

ANSWER: Structural

: Name the instruments that are used to measure the following.

1. The speed of wind.
ANSWER: Anemometer

2. The muddiness or cloudiness of water.

ANSWER: Secchi disc
3. The direction of wind.
ANSWER: Wind vane
1. Name the type of association between Rhizobium and roots of leguminous plants.
ANSWER: Mutualism

2. Name the type of association that exists between mistletoe and flowering plants.
ANSWER: Parasitism

3. Name the type of association that exists between a tree and a nesting bird on the tree.
ANSWER: Commensalism