Organisms and Populations Questions and Answers AP Inter 2nd Year Zoology Chapter 8

Reviewing AP Inter 2nd Year Zoology Study Material Chapter 8 Organisms and Populations Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Zoology 8th Lesson Organisms and Populations Questions and Answers

IV. Very Short Answer Questions

Question 1.
Define carrying capacity.
Answer:
Carrying capacity (K) is the maximum number of individuals of a particular species that a habitat can sustainably support with the resources available.

Question 2.
What is commensalism? Give one example.
Answer:

1. Commensalism is an interaction between two different species in which one species benefits while the other remains neither benefited nor harmed.
2. Example: An orchid growing on a mango tree. The orchid receives physical support, whereas the mango tree is unaffected.

Question 3.
Define mortality.
Answer:

1. Mortality is the number of deaths occurring in a population during a specified period.
2. It is one of the major factors, along with emigration, that contributes to a decrease in population density.

Question 4.
Give one example of mutualism.
Answer:
Lichen (Alga + Fungus) is a classic example of mutualism,

• The alga prepares food through photosynthesis.
• The fungus provides water, minerals, shelter, and protection.

Question 5.
Write the Verhulst-Pearl Logistic Growth equation.
Answer:
Verhulst-Pearl Logistic Growth Equation : dN/dt = rN(l – N/K)
Where:

• N = Population size
• r = Intrinsic rate of natural increase
• K = Carrying capacity
• dN/dt = Rate of population growth

V. Short Answer Questions

Question 1.
Differentiate between Exponential and Logistic Growth.
Answer:

Question 4.
Explain the term “Age Pyramid” and its significance.
Answer:
Age Pyramid:
1. An age pyramid is a graphical representation showing the age composition of a population.
2. It displays the percentage of individuals belonging to different age groups:

• Pre-reproductive,
• Reproductive,
• Post-reproductive.

3. It generally represents the distribution of both males and females within a population.
Types of Age Pyramids :

Expanding (Triangular) Pyramid:

1. Contains a larger proportion of young individuals.
2. Indicates a growing population.

Stable (Bell-shaped) Pyramid :

1. Shows nearly equal proportions of different age groups.
2. Represents a stable population.

iii) Declining (Urn-shaped) Pyramid:

1. Has a greater proportion of older individuals.
2. Indicates a declining population.

Significance:

• Helps predict future trends in population growth.
• Indicates whether a population is expanding, stable, or declining.
• Assists in planning resources, healthcare, and developmental programmes.
• Provides information about the age structure and reproductive potential of a population.

Question 5.
Why is competition considered a negative interaction?
Answer:
Competition is regarded as a negative interaction because both participating species are adversely affected while competing for the same limited resources.

• Competition for Resources: Organisms compete for essential resources such as food, water, nutrients, space, and light, reducing the availability of these resources for both species.
• Reduced Fitness: Competition lowers the growth, survival, and reproductive success (fitness) of one or both competing species.
• Interference Competition: Even when resources are present, the presence of one species may interfere with the feeding, growth, or reproduction of another, causing negative effects.
• Competitive Exclusion: According to Gause’s Competitive Exclusion Principle, two species competing for the same limiting resource cannot coexist indefinitely. Eventually, the superior competitor excludes or eliminates the weaker one.

Question 6.
What is Competitive Release? Give an example where a species showed wider distribution in the absence of a competing species.
Answer:

1. Competitive release is the phenomenon in which a species expands its population size or geographical distribution after the removal of a stronger competing species.
2. Under normal conditions, a dominant competitor restricts the growth and spread of another species by competing for common resources such as food, shelter, or space.
3. Once the superior competitor is absent, the weaker species gains access to more resources and habitat, allowing it to increase in number and occupy a wider area.

Example: (Connell’s Barnacle Experiment)

• The barnacle Balanus is a stronger competitor and occupies most of the intertidal region.
• It limits the distribution of the smaller barnacle Chthamalus to a narrow zone.
• When Balanus is removed, Chthamalus spreads into the vacant area and occupies a much larger portion of the shore, demonstrating competitive release.

Question 7.
Explain Gause’s Competitive Exclusion Principle with a suitable natural example from nature.
Answer:

1. Gause’s Competitive Exclusion Principle states that two closely related species competing for the same limited resources cannot coexist indefinitely in the same habitat.
2. When two species depend on identiçal resources such as food, water, or space, the better competitor utilizes the resources more efficiently, while the weaker species becomes disadvantaged.
3. Over time, the weaker species is either eliminated from the habitat or forced to migrate, as both species cannot permanently occupy the same ecological niche.

• In the Galapagos Islands, the Pinta Island tortoise was originally the major grazing herbivore.
• Later, goats were introduced, and they competed with the tortoises for the same vegetation.
• Since goats grazed more efficiently, they outcompeted the tortoises for food resources.
• As a result, the tortoise population declined drastically and eventually became extinct on the island, illustrating the principle of competitive exclusion.

VI. Long Answer Questions

Question 1.
Give an account of various types of interactions among the animal species with suitable examples.
Answer:
In nature, plants, animals, and microorganisms interact with one another to form biological communities. These interspecific interactions may be beneficial (+), harmful (-), or neutral (0) depending on their effect on the participating species.

1.Mutualism (+/ +):

• Mutualism is an interaction in which both species benefit.
• These associations are often essential for the survival, growth, and reproduction of the organisms involved.

Examples:

1. Lichen: The alga prepares food through photosynthesis, while the fungus provides shelter, water, and minerals.
2. Mycorrhiza: Fungi help plant roots absorb water and minerals, while plants supply carbohydrates to the fungi.
3. Fig tree and fig wasp: Both organisms depend on each other for successful reproduction.

Mutualism improves the survival and reproductive success of both species.

2. Competition (-/-):

• Competition occurs when two species utilize the same limited resources, causing both to be negatively affected.
• Resources involved may include food, water, light, nutrients, or living space.

Examples:.

1. Flamingos and fishes competing for zooplankton.
2. Balanus (strong competitor) restricting the distribution of Chthamalus.
3. Goats competing with Galapagos tortoises for vegetation.

• Some organisms reduce competition through resource partitioning, where they use different resources or exploit them at different times.
• Competition influences the growth, survival, and geographical distribution of species.

3. Predation (+ / -):
In predation, one organism (predator) captures, kills, and feeds on another organism (prey).

Examples:

1. Tiger hunting deer.
2. Sparrow feeding on seeds.
3. Sea star Pisaster preying on mussels.

• Predators regulate prey populations and help prevent overpopulation.
  
• Prey species develop defensive adaptations such as camouflage, mimicry, toxins, or protective structures.
• Predation contributes to ecological balance and maintains species diversity.

4. Parasitism (+ / -):

• In parasitism, the parasite benefits, whereas the host is harmed.
• Parasites obtain food and shelter by living on or inside the host.

Examples:

1. Ectoparasites: Lice, ticks.
2. Endoparasites: Liver fluke, Plasmodium.
3. Brood parasitism: Asian koel laying eggs in the nest of a house crow.

The host is weakened but usually not killed immediately, allowing the parasite to survive.

5. Commensalism (+/ O):
In commensalism, one organism benefits while the other is neither helped nor harmed.

Examples:

1. Orchid growing on a mango tree for physical support.
2. Cattle egrets feeding on insects disturbed by grazing cattle.
3. Clownfish obtaining protection among the tentacles of sea anemones.

This interaction benefits only one species without affecting the other.

6. Amensalism (- / 0):

• Amensalism is an interaction where onç species is harmed, while the other remains unaffected.
• It usually occurs when one organišm inhibits the growth or survival of another without gaining any benefit.
• Although less common than other interactions. amensalism plays an important role in maintaining ecological balance.

Question 2.
Write an essay on population growth models.
Answer:
Population size and population density are not fixed; they vary over time due to several factors such as food availability, climatic conditions, competition, and predation. To explain these variations, ecologists have developed population growth models, mainly the exponential growth model and the logistic growth model.

These models help in understanding population dynamics, wildlife conservation, and resource management.
1. Exponential Growth Model (J-shaped Curve): The exponential growth model explains how a population grows under ideal environmental conditions, where resources are available without limitation. Under such favourable conditions, organisms reproduce at their highest biological capacity, resulting in a rapid rise in population size.

Exponential Growth Equation:dN/dt = rN
Where:

• N = Population size .
• t=Tinie E
• dN/dt = Rate of change of population with respect to time
• r = Intrinsic rate of natural increase

When the population size is plotted against time, it produces a J-shaped growth curve, indicating rapid and uninterrupted population growth. The population at any given time can also be represented by: N_t = N₀e^rt
Where: N_t = Population size at time t; N₀ = Initial population size e = Base of the natural logarithm (≈ 2.718); r = Growth rate; t = Time

However, exponential growth is seldom observed in nature because unlimited resources are rarely available. It generally occurs only for a short duration, such as when a species colonizes a new habitat

2. Logistic Growth Model (S-shaped Curve): In natural environments, resources are limited, so a population cannot continue growing forever. As the population increases, competition for available resources becomes more intense, causing the growth rate to decline.

Eventually, the population reaches a maximum sustainable limit known as the carrying capacity (K), which represents the largest number of individuals that the environment can support

Logistic Growth Equation: dN/dt = rN(1 -N/K)

Where: N = Population size; t = Time; r = Intrinsic rate of natural increase
K = Carrying capacity (maximum population that the environment can sustain);
(1-N/K) = Environmental resistance factor

When the population size (N) is small, the population grows rapidly. As N gradually approaches the carrying capacity (K), the growth rate slows down and finally becomes zero when N = K.
This model produces an S-shaped (sigmoid) growth curve consisting of three distinct phases:

• Lag Phase: Initial stage with slow population growth. ,
• Log Phase: Period of rapid population growth.
• Stationary Phase: Growth levels off as the population reaches the carrying capacity.

The logistic growth model is regarded as a more realistic representation of population growth under natural environmental conditions.

I. Multiple Choice Questions

Question 1.
Which of the following is correct example of a commensalism interaction?
1. Tiger and Deer
2. Orchid growing on mango tree
3. Orchid flower and Bee
4. Algae and fungi in a lichen
Answer:
2. Orchid growing on mango tree

Question 2.
The carrying capacity of population is represented by
1. Birth rate
2. Death rate
3. K
4. R
Answer:
3. K

Question 3.
Natality refers to
1. Number of deaths per unit time
2. The number of births per unit time
3. Number of immigrants
4. Number of emigrants
Answer:
2. The number of births per unit time

Question 4.
Which interaction harms both species?
1. Mutualism
2. Amensalism
3. Competition
4. Predation
Answer:
3. Competition

Question 5.
The logistic growth equation is
1. dN/dt = Rn
2. dN/dt = rN(K – N)/K
3. dN/dt = K – N
4. dN/dt = rN
Answer:
2. dN/dt = rN(K – N)/K

Question 6.
The process of migration from one habitat to another for breeding is called :
1. Immigration
2. Emigration
3. Natality
4. Seasonal migration
Answer:
4. Seasonal migration

Question 7.
In which type inter species interaction, result is+/0?
1. Parasitism
2. Commensalism
3. Mutualism
4. Amensalism
Answer:
2. Commensalism

II. Fill in the Blanks

1. The intrinsic rate of natural increase is denoted by …………………….. .
Answer:
r

2. In predation, one organism is benefited and the other is …………………….. .
Answer:
harmed

3. The interaction between algae and fungi in lichen is ………………………… .
Answer:
Mutualism

4. Removal of predators from an ecosystem can lead to in ……………………….. of prey population.
Answer:
over population

5. ………………………….. is the study of relationships of organisms with their environment.
Answer:
Ecology

6. The population growth curve with an S-shape is called ………………………. growth curve.
Answer:
Logistic

III. One Word Answer Questions

Question 1.
What is the term used for number of individuals per unit area?
Answer:
Density

Question 2.
In which biological interspecies relationship where both species are in benefit?
Answer:
Mutualism

Question 3.
In what type of biological relationship one organism that lives inside another?
Answer:
Endoparasite

Question 4.
Name the term used for “The gradual change in population size over time”.
Answer:
Population growth

Question 5.
What is the process known as when an organism is transferred from its natural habitat to a different one?
Answer:
Emigration

Question 6.
What does the term ‘r’ in population growth represent?
Answer:
Intrinsic rate of natural increase

Objective Questions

Question 1.
Ecology mainly deals with the relationship between organisms and their ………………….. .
1. Tissues
2. Environment
3. Cells
4. Genes
Answer:
2. Environment

Question 2.
The natural place where an organism lives is known as its:
1. Niche
2. Community
3. Habitat
4. Population
Answer:
3. Habitat

Question 3.
Individuals of the same species occupying a defined area together form a:
1. Habitat
2. Population
3. Ecosystem
4. Community
Answer:
2. Population

Question 4.
Which of the following is considered an abiotic factor?
1. Animals
2. Microbes
3. Temperature
4. Plants
Answer:
3. Temperature

Question 5.
Which among the following is a biotic factor?
1. Soil
2. Light
3. Water
4. Animals
Answer:
4. Animals

Question 6.
Temperature mainly influences organisms by affecting:
1. Distribution
2. Growth
3. Metabolism
4. All of these
Answer:
4. All of these

Question 7.
Organisms capable of maintaining a constant body temperature are called:
1. Cold-blooded
2. Endotherms
3. Ectotherms
4. Poikilotherms
Answer:
2. Endotherms

Question 8.
Animals that cannot regulate a constant body temperature are:
1. Warm-blooded
2. Homeotherms
3. Ectotherms
4. Endotherms
Answer:
3. Ectotherms

Question 9.
Water availability influences organisms with respect to:
1. Reproduction
2. Distribution
3. Survival
4. All of these
Answer:
4. All of these

Question 10.
Light is an essential factor for:
1. Digestion
2. Respiration
3. Photosynthesis
4. Excretion
Answer:
3. Photosynthesis

Question 11.
Soil characteristics mainly affect:
1. Mutation
2. Plant growth
3. Enzyme action
4. Animal behaviour
Answer:
2. Plant growth

Question 12.
Adaptation refers to:
1. Growth only
2. Structural and functional adjustments
3. Isolation
4. Mutation only
Answer:
2. Structural and functional adjustments

Question 13.
Migration enables organisms to:
1. Escape unfavorable conditions
2. Find food
3. Avoid predators
4. All of these
Answer:
4. All of these

Question 14.
Hibernation is an adaptation for surviving during:
1. Rainy season
2. Winter
3. Summer
4. Spring
Answer:
2. Winter

Question 15.
Aestivation generally occurs in:
1. Autumn
2. Summer
3. Winter
4. Spring
Answer:
2. Summer

Question 16.
Desert plants commonly show:
1. Soft stems
2. Thick cuticle
3. High transpiration
4. Large leaves
Answer:
2. Thick cuticle

Question 17.
Camels survive in deserts mainly because of:
1. Large ears
2. Water conservation
3. Thin skin
4. High sweating
Answer:
2. Water conservation

Question 18.
Population density refers to the number of individuals per:
1. Organ
2. Cell
3. Unit area
4. Tissue
Answer:
3. Unit area

Question 19.
Natality is another term for:
1. Birth rate
2. Migration
3. Growth
4. Death rate
Answer:
1. Birth rate

Question 20.
Mortality represents the:
1. Growth
2. Migration
3. Death rate
4. Birth rate
Answer:
3. Death rate

Question 21.
Immigration means movement of individuals:
1. Into population
2. Out of population
3. Across species
4. Within population
Answer:
1. Into population

Question 22.
Emigration refers to movement of individuals:
1. Out of population
2. Into population
3. Across species
4. Within population
Answer:
1. Out of population

Question 23.
Population growth is influenced by:
1. Migration
2. Birth
3. Death
4. All of these
Answer:
4. All of these

Question 24.
Exponential growth produces which type of curve?
1. Circular
2. J- shaped
3. Linear
4. S-shaped
Answer:
2. J- shaped

Question 25.
Logistic growth is represented by:
1. Straight line
2. Circular
3. S – shaped
4. J – shaped
Answer:
3. S – shaped

Question 26.
Competition occurs when organisms:
1. Share resources
2. Compete for the same resource
3. Mutate
4. Grow independently
Answer:
2. Compete for the same resource

Question 27.
Predation is an interaction where one organism:
1. Helps another
2. Kills another
3. Mutates
4. Competes
Answer:
2. Kills another

Question 28.
Parasitism benefits:
1. Host only
2. Parasite only
3. Both
4. None
Answer:
2. Parasite only

Question 29.
Mutualism is an interaction that benefits:
1. None
2. Both species
3. Predator
4. One species
Answer:
2. Both species

Question 30.
In commensalism, the beneficiary is:
1. Both
2. One species, the other unaffected
3. Both harmed
4. None
Answer:
2. One species, the other unaffected

Question 31.
Amensalism is an interaction where:
1. One harmed, other unaffected
2. One benefited
3. Both benefited
4. Both harmed
Answer:
1. One harmed, the other unaffected

Question 32.
Population interactions are studied under:
1. Anatomy
2. Ecology
3. Physiology
4. Genetics
Answer:
2. Ecology

Question 33.
Predators help maintain:
1. Growth
2. Mutation
3. Stability
4. Imbalance
Answer:
3. Stability

Question 34.
Adaptations evolve over:
1. Hours
2. Days
3. Generations
4. Minutes
Answer:
3. Generations

Question 35.
Organisms react to environmental changes through:
1. Migration
2. Adapting
3. Hibernating
4. All of these
Answer:
4. All of these

Question 36.
Environmental resistance mainly restricts:
1. Adaptation
2. Population growth
3. Migration
4. Mutation
Answer:
2. Population growth

Question 37.
The suitable temperature range for an organism is known as:
1. Maximum range
2. Fixed range
3. Optimum range
4. Minimum range
Answer:
3. Optimum range

Question 38.
Adaptations enable organisms to:
1. Reproduce
2. Survive
3. Maintain balance
4. All of these
Answer:
4. All of these

Question 39.
Soil primarily influences:
1. Mutation
2. Plant growth
3. Animal growth
4. Digestion
Answer:
2. Plant growth

Question 40.
Ecological niche includes:
1. Resource use
2. Habitat
3. Role of organism
4. All of these
Answer:
4. All of these

Question 41.
Population size changes due to:
1. Migration
2. Birth
3. Death
4. All of these
Answer:
4. All of these

Question 42.
Ecological interactions influence:
1. Ecosystem
2. Population
3. Community
4. All of these
Answer:
4. All of these

Question 43.
Population growth decreases when:
1. Resources are limited
2. Mutation increases
3. Migration increases
4. Resources abundant
Answer:
1. Resources limited

Question 44.
Ecology mainly deals with the study of:
1. Cells
2. Genes
3. Interactions
4. Tissues
Answer:
3. Interactions

Question 45.
The intrinsic rate of natural increase is represented by:
1. N
2. r
3. t
4. K
Answer:
2. r

Question 46.
Carrying capacity is denoted by:
1. r
2. K
3. N
4. t
Answer:
2. K

Question 47.
Logistic growth equation mainly considers:
1. Carrying capacity
2. Mutation
3. Migration
4. Isolation
Answer:
1. Carrying capacity

Question 48.
Which factor directly increases population size?
1. Competition
2. Natality
3. Mortality
4. Emigration
Answer:
2. Natality

Question 49.
Immigration results in:
1. Increase in population
2. No change
3. Mutation
4. Decrease in population
Answer:
1. Increase in population

Question 50.
Emigration causes:
1. Increase in population
2. Mutation
3. No change
4. Decrease in population
Answer:
4. Decrease in population

Question 51.
The age structure of a population is illustrated by:
1. Graph
2. Table
3. Pyramid
4. Curve
Answer:
3. Pyramid

Question 52.
A population with more young individuals shows as:
1. Stable pyramid
2. Expanding pyramid
3. Declining pyramid
4. Bell-shaped pyramid
Answer:
2. Expanding pyramid

Question 53.
A stable population is represented by:
1. Declining
2. Bell-shaped
3. Expanding
4. Irregular
Answer:
2. Bell-shaped

Question 54.
An interaction in which both organisms gain benefit is called:
1. Competition
2. Mutualism
3. Predation
4. Parasitism
Answer:
2. Mutualism

Question 55.
In parasitism, the host is:
1. Harmed
2. Benefited
3. Unaffected
4. Mutated
Answer:
1. Harmed

Question 56.
An organism that feeds on another organism is known as:
1. Host
2. Predator
3. Competitor
4. Parasite
Answer:
2. Predator

Question 57.
Predation helps regulate:
1. Population size
2. Mutation
3. Migration
4. Growth
Answer:
1. Population size

Question 58.
Competition develops when organisms use:
1. Same limited resources
2. Habitat only
3. Same genes
4. Same species only
Answer:
1. Same limited resources

Question 59.
Which interaction harms one species while the other remains unaffected?
1. Mutualism
2. Amensalism
3. Parasitism
4. Commensalism
Answer:
4. Commensalism

Question 60.
In commensalism, one organism benefits while the other is :
1. Benefited
2. Harmed
3. Unaffected
4. Mutated
Answer:
3. Unaffected

Question 61.
Lichens are a classic example of:
1. Competition
2. Mutualism
3. Amensalism
4. Parasitism
Answer:
2. Mutualism

Question 62.
Population growth rate depends on :
1. Mortality
2. Natality
3. Migration
4. All of these
Answer:
4. All of these

Question 63.
Environmental resistance includes factors that:
1. Increase reproduction
2. Limit population growth
3. Increase population
4. Increase mutation
Answer:
2. Limit population growth

Question 64.
The symbol “r” indicates :
1. Population size
2. Growth rate
3. Carrying capacity
4. Time
Answer:
2. Growth rate

Question 65.
Population growth becomes zero when:
1. Resources increase
2. Carrying capacity is reached
3. Migration occurs
4. Birth rate increases
Answer:
2. Carrying capacity is reached

Question 66.
Population regulation mainly occurs because of:
1. Environmental resistance
2. Mutation
3. Reproduction
4. Isolation
Answer:
1. Environmental resistance

Question 67.
When population size equals carrying capacity, growth rate becomes:
1. Negative
2. Zero
3. Maximum
4. Minimum
Answer:
2. Zero

Question 68.
Which interaction negatively affects both participating species?
1. Competition
2. Mutualism
3. Commensalism
4. Parasitism
Answer:
1. Competition

Question 69.
In parasitism, the organism that gains benefit is the:
1. Host
2. Parasite
3. Both
4. None
Answer:
2. Parasite

Question 70.
Predators help preserve ecological balance by:
1. Increasing prey
2. Controlling prey population
3. Causing mutation
4. Increasing growth
Answer:
2. Controlling prey population