Organisms and Population
EXERCISE
Q.1 Multiple choice question
i) Which factor of an ecosystem includes
plants, animals, and microorganisms?
2. Abiotic factor
3. Direct factor
4. Indirect factor
Solution: Biotic factor
ii) An assemblage of individuals of
different species living in the same habitat and having functional interactions
is _______________.
1. Biotic community
2. Ecological niche
3. Population
4. Ecosystem
Solution: An assemblage of individuals of different species living in the
same habitat and having functional interactions is a Biotic community.
iii) Association between sea anemone and
Hermit crab in gastropod shell is that of _______________.
1. Mutualism
2. Commensalism
3. Parasitism
4. Amensalism
Solution: Association
between the sea anemone and Hermit crab in gastropod shell is that of Commensalism.
iv) Select the statement which explains
the best parasitism.
1. One species is benefited.
2. Both the species are benefited.
3. One species is benefited, other is not affected.
4. One species is benefited, other is harmed.
Solution: One species is benefited, other is harmed.
v) Growth of bacteria in a newlly
innoculated agar plate shows ____________.
1. exponential growth
2. logistic growth
3. Verhulst-Pearl logistic growth
4. zero growth
Solution: Growth of bacteria in a newly innoculated agar plate shows exponential growth.
Q.2.Very short answer question
1.Define the following term -Commensalism
Ans:
Commensalism: Commensalism is the interaction in which one species gets
benefited and the other is neither harmed nor benefited.
2.Define the
following term-Parasitism
Ans: Parasitism: Parasitism is the interaction in which only one species (parasite)
is benefited and the interaction is detrimental to other species (host).
3.Define the following term -Camouflage
Ans:
Camouflage: Camouflage is the cryptic coloration or patterns adopted by prey
species to blend with the surroundings or background so as to escape their
predators.
4.Give one example for Interspecific
competition
Ans:
Interspecific competition:
E.g. Competition between leopards and
lion, resident fish competing with migratory birds Flamingos for common food
i.e. zooplankton
5.Give one example for Mutualism
Ans: Mutualism: E.g. Lichens represent an intimate, mutualistic relationship between a fungus and photosynthetic algae or cyanobacteria.
6.Name the type of association:
Clownfish and sea anemone
Ans:Clown
fish and sea anemone: Commensalism
7.Name the type of association: Crow
feeding the hatchling of Koel
Ans:
Crow feeding the hatchling of Koel: Brood parasitism
8.Name the type of association: Humming birds
and host flowering plants
Ans:
Humming birds and host flowering plants: Mutualism
9.What is the ecological process behind
the biological control method of managing with pest insects?
Ans: The ecological process behind the biological control method of managing with pest insects is Predation. Predators regulate the population of prey in a habitat, thus helping in the management of pest insects.
Q.3.Short answer question
1.How is the dormancy of seeds different
from hibernation in animals?
Ans:i.
Seed dormancy is the inability of viable seeds to germinate even under suitable
environmental conditions, whereas hibernation in animals is a state of reduced
activities to escape cold winter conditions.
ii. During seed dormancy, growth and development of an embryo are arrested temporarily, whereas in hibernation animals enter a state of inactivity by slowing their metabolism.
2.If a marine fish is placed in a
freshwater aquarium, will it be able to survive? Give reason.
Ans:i.
If a marine fish is placed in a freshwater aquarium, fish would not be able to
survive because marine fishes are adapted to high salt concentrations of the
marine environment.
ii. Marine fishes
have more osmotic concentration (more salt concentration) than marine water
which prevents marine water to enter into the body.
iii. When marine fish
is placed in a freshwater aquarium, water enters into the body of marine fish
due to osmosis, as freshwater creates a hypotonic environment outside the
fish’s body.
iv. Entry of water into the body causes
its body to swell leading to the death of the marine fish.
3.Name important defense mechanisms in
plants against herbivores.
Ans:efense
mechanisms in plants against herbivores can be morphological like thorns (in
Acacia, Cactus) or chemicals like poisonous cardiac glycosides (produced by
Calotropis), secondary metabolites (for e.g.nicotine, caffeine, quinine,
strychnine, opium, etc.)
4.An orchid plant is growing on the
branch of the mango tree. How do you describe this interaction between the
orchid and the mango tree?
Ans:An orchid growing on the branch of a mango tree is an epiphyte. Epiphytes are plants growing on other plants which however, do not derive nutrition from them. Therefore, the relationship between a mango tree and an orchid is an example of commensalisms,
where
one species gets benefited while the other remains unaffected. In the above
interaction, the orchid is benefited as it gets support while the mango tree
remains unaffected.
i. An orchid plant is
growing on the branch of a mango tree represents Commensalism.
ii. In this
interaction, one species gets benefited and the other is neither harmed nor
benefited.
iii. Orchid is an
epiphytic plant. While growing on mango tree it gets support but does not
derive any nutrition from the mango tree.
iv. Thus, the orchid plant is benefited, while the mango tree is neither benefited nor harmed.
5.Write a short note on Adaptations of
desert animals
Ans:Adaptations
of animals for desert habitats:
1. Desert animal-like
Kangaroo rat inhabiting the Arizona deserts has the potential to concentrate
its urine to conserve water. This animal never drinks water in its life.
2. Snakes and desert
lizards bask in the sun early in the morning and burrow themselves in the sand
in the afternoons to escape the heat of the day, to prevent water loss.
3. Camels can store fat in the hump
which can be metabolised for energy. A camel can survive for many days without
water. Long eyelashes, ears lined with hair, and slit-like nostrils help to
keep out sand.
6. Write a short note on Behavioural
adaptations in animals
Ans:Behavioural
adaptations in animals.
a. To cope up with
extreme variations in their environment, some organisms respond through
behaviourally (like migration, hibernation, and aestivation).
b. For e.g. Desert
lizards manage to keep their body temperature fairly constant by behavioural
adaptations.
c. They bask in the sun and absorb heat
when their body temperature drops below the comfort zone. But when the ambient
temperature starts increasing, they move into the shade.
d.
Some species burrow into the sand to hide and escape from the heat.
7. Define Population and Community.
Ans:i. Population: Organisms
of the same kind inhabiting a geographical area constitute the population.
OR
Individuals live in
groups in a well-defined geographical area, share or compete for similar
resources, potentially interbreed and thus form a population.
OR
The population is
defined as a group of individuals of a species occupying a definite geographic
area at a given time.
ii. Community: Several populations of different species in a particular area constitute a community that interacts with one another in several ways.
Q. 4.Long answer question
Enlist and explain the important
characteristics of a population.
Ans:i. The important characteristics of a population are population size, population density, natality, mortality, sex ratio, immigration, emigration, age pyramids, expanding population, population growth forms, and biotic potential.
ii. Some
important characteristics of the population are: a. Population density: Population
density tells us the number of individuals presents per unit space, in a given
time.
OR The
density of a population is the total number of individuals in that population
present per unit area at a specific time.
b.
Natality: Natality is the birth rate of a population.
c.
Mortality: Mortality is the death rate of a population.
d.
Age distribution and Age pyramids:
1. A population
consists of individuals of different ages. The entire population is divided
into three age groups – pre-reproductive (0-14 years), reproductive (age 15-44
years), post-reproductive (45-85+years)The relative proportion of individuals
of various age groups in the population is referred to as the age structure of
the population.
2. If the age
distribution (percent individuals of a given age or age group) is plotted for
the population, the resulting structure is called as age pyramid.
e.
Sex Ratio:
Sex ratio is the ratio of the number of individuals of one sex to that of the other sex