Organism and population

1 mark Questions
Q1) Define the following
1) Population: “population may be defined as a group of organisms of the same species occupying a
particular space in a given time”.

2) Habitat: :- “ Habitat is a place or the set of the environmental conditions around the organism to
which it must adapt to survive and prosper.”

OR
“ place or area where a particular species life is its habitat.

3) Natality :- “ Natality is the birth rate of a population.”

4) Mortality:- Mortality is the death rate of a population”.

5) Immigration: (I) is the number of individuals of the same species that have come into the habitat
from elsewhere during the time period under consideration.
6) Emigration: (E) is the number of individuals of the population who left the habitat during the time
period.
7) Mutualism: The interaction is between two species which are interdependent. It benefits both the
species.
8) Competition: Competition is the type of interaction where both the species are at loss.
9) Parasitism: It is the interaction between two species where one species benefits while other is
harmed is called Parasitism.
10) Predation: It is an interaction where one species hunts another species for food . the species tha t
hunts is called predator and the species that is hunted is called prey.
11) Commensalism: Commensalism is the interaction in which one species benefits and the other is
neither harmed nor benefited.
12) Camouflage : Camouflage is called cryptic coloration, is a defence mechanism to avoid being
detected easily, easily by the predators.

Q2) Give an example of each

 Mutualism: Plant – Animal relationship :- Lichen ( fungus and cyanobacteria interaction)
 Interspecific competition - In shallow creeks on the west coast of Mumbai, visiting
flamingos and resident fish compete for their common food the zooplankton.
Competiotion between lepord and lions for the same prey.
 Ectoparasitism : Lice on human , ticks on dogs.
 Brood Parasitism: Asian koel and common Indian crow.
 Commensalism: An orchid growing as an epiphyte on branch of mango tree., sea anemone
and clown fish..

Q3) Name the type of association

1. Clownfish and sea anemone: - Commensalism
2. Plasmodium vivax and female anopheles mosquito: - Parasitism
3. Crow feeding the hatching of koel: - Brood parasitism
4. Humbing birds and host of flowering plants:- Mutualism
5. Visiting flamingo and resident fish in Mumbai coast :- Competition
6. Fungus and photosynthetic algae (Lichen): -Mutualism
7. Cattle egrets and grazing cattle:- Commensalism
flowering

2 marks Questions

Q1) Distinguish between

a. Habitat and Niche
Habitat Niche
A habitat is an area, where a species lives and A niche is an concept, of how an organism lives
interact with the other factors and proposer. or survive in the environmental conditions.
Habitat consist of numerous niches. Niche do not contain such components.
Effect of temperature, rainfall and other abiotic Niche shows impact of organisms upon the
factors. On its population. habitat
Habitat supports numerous species at a time. Niche supports a single species at a time.
Habitat is a physical place. Niche is an activity performed by organisms.
Habitat is not species specific. Niche is species specific.
 b) Natality and Mortality.
Natality Mortality
Natality is the birth rate of a population Mortality is the death rate of population
It is number of births per unit population per It is number of deaths per unit population per
unit time unit time
It increases population size It decreases population size
It increases population density It decreases population density.

c) Parasitism and Mutualism

Parasitism Mutualism
Parasites harm the host and parasites is It benefits both the species
benefitted
It occurs between host and parasites It occurs between two non- parasitic species
Parasite need host to complete it’s life cycle but This interaction is obligatory and inter-
host doesn’t need parasite. dependent.
Eg. Plasmodium vivax need the host to comlete Fungus and photosynthetic algae (Lichen)
the life cycle.

d) Competition and Mutualism

Mutualism Competitions
Mutualism is an interaction between two species in Competition is a negative interaction
which each member favours the growth and survival between two organisms in which the fitness
of each other of an organism overpowers the presence of
another
Both are benefited One is benefited and other is harmed.
This interaction is obligatory and Interaction where both species are at a loss.
interdependent. Totally unrelated species may compete for
the same resource.
Eg. Lichen E.g. Competition for food between
carnivores

2 Marks Questions
a. Define the term Natality. How is natality calculated?
Ans.:
i. “Natality is the birth rate of a population.”
ii. Natality is calculated as number of births per unit population per unit time.

b. With the help of Pyramid describe the growing population.

Ans.: The graphical representation of the age composition of a specific population is called the
Rapid growth age pyramid. E.g Kenya, Nigeria
1. Triangular shaped age pyramids are formed when the individuals in the pre-reproductive and
reproductive age group
2. The prer-eproductive age group is high and very less number of individuals are present in the
post-reproductive age group.
3. The population 'Rapid growth' represents an expanding population.
4. Kenya is showing rapid growth as its pre-reproductive group is large. Post-reproductive group is
much reduced. Therefore, 15 years from now, the population will be large.

Q) Write a shot note on ( 2 Marks Questions)

1. Exponential growth

1. When the resources are abundant: Food Space etc. With

2. Unlimited Habitat.
3. Each species has the ability to fully realize its innate potential to grow in numbers.
4. The growth of a population is called an exponential or geometric growth.
5. Every species growing exponentially under unlimited resource conditions.
6. Reach enourmous population densities in a short time.
7. E.g. Elephant could reach enourmous numbers.
8. Exponential growth shows J-shaped curve.
 1. Logistic Growth Curve
Ans.
1. A population growing in a habitat with limited resources show following phases in a sequential
manner, (a) A lag phase (b) Phase of acceleration (c) Phase of deceleration (d) An asymptote.
2. When the population density reaches the carrying capacity.A plot of N in relation to time (t)
results in a sigmoid curve. This type of population growth is called Verhulst-Pearl Logistic
Growth.

2. Adaptation of desert animals

Ans. :
1. Desert animals like camel produce concentrated urine and dry dung.
2. Many other hot desert animals are nocturnal, seeking out shade during the day or dwelling
underground in burrows.
3. Many desert species burrow into sand, to hide and escape from the heat .

3. Adaptation of desert plant.

Ans:
1. Thick cuticle on their leaf surfaces
2. Stomata of desert plants is sunken that is it is in deep pits to minimize loss of water through
transpiration.
3. Desert plants also have a special photosynthetic pathway (CAM -Crassulacean acid metabolism)
that enables their stomata to remain closed during daytime.
4. Desert plant Opuntia, have their leaves reduced or they are modified to spines to prevent
transpiration.
5. The flattened stems called as phylloclade does photosynthesis.

4. Adaptation of animals in colder region

Ans:
1. Shorter snout, ear, tail and limbs to minimise loss of body heat. E.g. polar bear
2. Aquatic mammals have thick layer of fat below their skin acting as an insulator to reduce loss of
body heat.e.g Polar seals.

5. Explain Gause’s : Competitive Exclusion Principle”.

Ans:
1. Gause’s : Competitive Exclusion Principle” state that two closely related species competing for
the same resources cannot coexist indefinitely and the competitively inferior one will be
eliminated eventually.
2. It is possible if resources are limited.
3. Species could avoid competition by choosing different times for feeding.

6. Name important defence mechanism in plants against Herbivorous.

Ans:
1. Morphological defence against grazing animals : e.g. Acacia ( Thorn)
2. E.g Calotropis produced highly poisonous cardiac glycosides.

7. An orchid plant is growing on branch of mango tree. How do you describe this interaction between the
orchid and mango tree.
Ans:

1. Orchid grows as epiphyte on mango trees. The tree do not get any benefit but is neither harmed.
But orchid gets support.
2. It is an e.g of commensalism

8. Write any Two behavioural adaptation in animals.

Ans:

1. Desert lizard.
2. Some species burrow into the sand to hide and escape from the heat.
3. They bask in the sun and absorb heat, when their body temperature drops below the comfort zone,
move into shade, when the ambient temperature starts increasing.
4. Migration: Some organisms respond through physiological adjustment

3 marks Questions
1. What are the major abiotic factors that influence habitat?
Ans. :
1. Water:
a. Availability of water is an important factor affecting the organism.
b. The productivity and distribution of plants are also heavily dependent on water.
 2. Light:
a. Plants use light for photosynthesis, which only source of energy. for the entire ecosystem.
b. For animals, diurnal and seasonal variation in light intensity and duration are clues for timing,
their foraging, reproductive and migratory activities.
3. Soil:
a. Characteristics of soil like composition, grain size, water holding capacity, determine the
perlocation,
b.pH, mineral composition and topography, determine the vegetation area.

2. What are the three types of niche?

Ans: The three types niche are found-

a. Spatial or habitat niche.

It deals with the physical space occupied by the organisms
b. Trophic niche :
It is on the basis of trophic level of an organism in a food chain.
c. Multidimensional or hyper volume niche.
 It considers a number of environmental factors, the resulting space will be hypervolume, not
something that can be perceived by the human mind.
 This space is called hypervolume niche.
 Fundamental niche: Absence of all competitors, this is highly improbable in nature.
 Realized niche: more realistic approach, in the presence of competition for the resources
available in the habitat.

3. What are the different ways in which organism adapt changes in environment.
Ans. :
1. Morphological: Desert plants have a thick cuticle on their leaf surface and have their stomata
in deep pits to minimize loss of water through transpiration. E.g. Opuntia
2. Physiological: Mammals from colder region have shorter snout, ears, tail, limb and a thick
layer of fat to minimise the loss of body heat.
3. Behavioural: Some species in a desert burrow into the sand to hide and escape from the heat.