ORGANISMS AND POPULATION MCQs for NEET UG BIOLOGY — Medium, Page 2

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If in a pond there are 20 lotus plants of last year and through reproduction 8 new plants are added. Then the birth rate is

View answer and explanation

Correct option: C

0.4 offspring per lotus per year

Option C (0.4 offspring per lotus per year) is correct because the birth rate is calculated by dividing the number of new plants by the initial number of plants (8/20 = 0.4).

Solution approach

Correct Answer + Core Reason: 0.4 offspring per lotus per year. Birth rate is the number of new individuals divided by the initial population size.

Step-by-Step Solution:
Step 1: Identify the number of new plants: 8.
Step 2: Identify the initial number of plants: 20.
Step 3: Calculate the birth rate: $Birth\ Rate = \frac{{Number\ of\ New\ Plants}}{{Initial\ Number\ of\ Plants}}$
Step 4: Substitute the values: $Birth\ Rate = \frac{{8}}{{20}}$
Step 5: Calculate the birth rate: $Birth\ Rate = 0.4$

Why other options are wrong:
- Option A: 0.8 is incorrect. It's not a logical calculation based on the given data.
- Option B: 0.2 is incorrect. It's not a logical calculation based on the given data.
- Option D: 0.6 is incorrect. It's not a logical calculation based on the given data.

Key Concepts:
- Birth rate
- Population dynamics

Memory Aids:
- Birth Rate = Births / Population

Quick Tips:
- Remember to divide the number of new individuals by the initial population size.

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(A): Two closely related species competing for the same resource cannot co-exist indefinitely.

(R): If two species compete for the same resource, they could avoid competition by choosing, for instance, different times for feeding or different foraging patterns.

View answer and explanation

Correct option: B

Both (A) and (R) are true and (R) is not the correct explanation for Assertion

Option B (Both (A) and (R) are true and (R) is not the correct explanation for Assertion) is correct because while both statements are true, the reason doesn't explain the competitive exclusion principle.

Solution approach

Correct Answer + Core Reason: Both (A) and (R) are true and (R) is not the correct explanation for Assertion. While both statements are true, the reason doesn't explain the competitive exclusion principle.

Step-by-Step Solution:

Step 1: Analyze Assertion (A): Two closely related species competing for the same resource cannot co-exist indefinitely. This is the competitive exclusion principle, which is true.

Step 2: Analyze Reason (R): If two species compete for the same resource, they could avoid competition by choosing, for instance, different times for feeding or different foraging patterns. This is resource partitioning, which is also true.

Step 3: Determine if Reason (R) explains Assertion (A): While both are true, resource partitioning is a mechanism to *avoid* competitive exclusion, not an explanation for why it occurs.

Step 4: Final Answer: Both (A) and (R) are true and (R) is not the correct explanation for Assertion

Why other options are wrong:
- Option A: The reason does not explain the assertion.
- Option C: Both assertion and reason are true.
- Option D: Both assertion and reason are true.

Key Concepts:
- Competitive exclusion principle
- Resource partitioning
- Ecological competition

Memory Aids:
- Competitive exclusion: One species outcompetes another for the same resource.
- Resource partitioning: Species evolve to use resources differently to avoid competition.

Quick Tips:
- Distinguish between the competitive exclusion principle and mechanisms to avoid competition.

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Example involved in the Connell’s elegent field experiments

View answer and explanation

Correct option: B

Balanus and Cathamalus

Option B (Balanus and Cathamalus) is correct because Connell's elegant field experiments involved studying the competition between these two barnacle species.

Solution approach

Correct Answer + Core Reason: Balanus and Cathamalus. Connell's experiments focused on interspecific competition between these barnacle species.

Step-by-Step Solution:

Step 1: Recall Connell's experiment: Connell's experiment is a classic example of interspecific competition in ecology.

Step 2: Identify the species involved: The experiment involved two species of barnacles, *Balanus* and *Chathamalus*, competing for space in the intertidal zone.

Step 3: Conclusion: The correct answer is *Balanus* and *Chathamalus*

Why other options are wrong:
- Option A: Pisaster and Invertebrates are involved in keystone predator experiments, not Connell's barnacle experiment.
- Option C: Goats and Abingdon relate to island ecology and grazing impacts.
- Option D: Warblers are related to resource partitioning studies.

Key Concepts:
- Interspecific competition
- Connell's experiment
- Barnacles

Memory Aids:
- Barnacles Compete: Balanus and Chthamalus

Quick Tips:
- Remember the key species and the focus of classic ecological experiments.

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Basic unit of ecological hierarchy is

View answer and explanation

Correct option: D

Individual organism

Option D (Individual organism) is correct because an individual organism is the most basic and fundamental unit in the ecological hierarchy.

Solution approach

Correct Answer + Core Reason: Individual organism. An individual organism is the most basic unit of ecological hierarchy.

Step-by-Step Solution:

Step 1: Define Ecological Hierarchy: The ecological hierarchy represents the levels of organization in ecology, from the simplest to the most complex.

Step 2: Analyze the Options: Consider each option in terms of its position in the hierarchy.

Step 3: Conclusion: The individual organism is the most basic unit because it's the starting point for ecological studies. Populations are groups of individuals, communities are groups of populations, and so on.

Why other options are wrong:
- Option A: Species is incorrect because a species is a group of similar individuals, making it a higher level of organization than an individual organism.
- Option B: Genus is incorrect because a genus is a taxonomic rank above species, representing a group of related species. It's even higher in the hierarchy.
- Option C: Population is incorrect because a population is a group of individuals of the same species, making it a higher level of organization than an individual organism.

Key Concepts:
- Ecological Hierarchy
- Individual Organism
- Population
- Species
- Genus

Memory Aids:
- Remember the order: Individual → Population → Community → Ecosystem → Biome → Biosphere. The individual is the base.

Quick Tips:
- Start with the smallest unit when considering ecological hierarchies.

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Ephemerals are xerophytes that are

View answer and explanation

Correct option: C

Drought escaping

Option C (Drought escaping) is correct because ephemerals are xerophytes that complete their life cycle quickly during the short periods when water is available, thus escaping drought conditions.

Solution approach

Correct Answer + Core Reason: Drought escaping. Ephemerals avoid drought by completing their life cycle quickly.

Step-by-Step Solution:

Step 1: Define Ephemerals. Ephemerals are plants that have a short life cycle, typically completing it during periods when conditions are favorable (e.g., after rainfall in a desert).

Step 2: Define Xerophytes. Xerophytes are plants adapted to arid environments.

Step 3: Analyze the options:
- A. Drought resisting: These plants have adaptations to withstand drought conditions for extended periods.
- B. Drought enduring: Similar to drought resisting, these plants can survive prolonged drought.
- C. Drought escaping: These plants avoid drought by completing their life cycle quickly when water is available.
- D. None of these: This is incorrect because ephemerals are a type of xerophyte that escapes drought.

Why other options are wrong:
- Option A: Drought resisting plants survive through drought, while ephemerals avoid it.
- Option B: Drought enduring plants survive through drought, while ephemerals avoid it.
- Option D: Ephemerals are a type of xerophyte that escapes drought.

Key Concepts:
- Xerophytes: Plants adapted to arid environments.
- Ephemerals: Plants with short life cycles that avoid drought.

Memory Aids:
- Think of "ephemeral" as something that is short-lived and fleeting, like the plant's life cycle.

Quick Tips:
- Differentiate between plants that resist, endure, and escape drought conditions.

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In a g raph of population, on x-axis time and on y-axis population is plotted. A parallal line to x-axis shows

View answer and explanation

Correct option: B

Natality equal to mortality

Option B (Natality equal to mortality) is correct because a parallel line to the x-axis in a population graph indicates that the population size is stable, meaning the birth rate (natality) equals the death rate (mortality).

Solution approach

Correct Answer + Core Reason: Natality equal to mortality. A parallel line indicates a stable population.

Step-by-Step Solution:

Step 1: Interpret the Graph. A graph with time on the x-axis and population on the y-axis shows population changes over time. A line parallel to the x-axis indicates no change in population size.

Step 2: Relate to Natality and Mortality. Population size remains constant when the number of births (natality) equals the number of deaths (mortality).

Step 3: Analyze the options:
- A. Natality increases mortality decreases: This would lead to population growth.
- B. Natality equal to mortality: This results in a stable population, represented by a horizontal line.
- C. Natality decreases mortality increases: This would lead to population decline.
- D. Natality constant mortality increases: This would lead to population decline.

Why other options are wrong:
- Option A: Natality increasing and mortality decreasing would cause the population to increase, not remain constant.
- Option C: Natality decreasing and mortality increasing would cause the population to decrease, not remain constant.
- Option D: Natality constant and mortality increasing would cause the population to decrease, not remain constant.

Key Concepts:
- Natality: Birth rate.
- Mortality: Death rate.
- Population Growth: Change in population size over time.

Memory Aids:
- Remember that a stable population means births and deaths are balanced.

Quick Tips:
- Understand how birth and death rates affect population growth and decline.

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The relationship between the alga Microcystis and the surroundings fauna correspond to

View answer and explanation

Correct option: A

Amensalism

Option A (Amensalism) is correct because amensalism describes a relationship where one organism is harmed or inhibited, and the other is unaffected. Microcystis can release toxins that harm surrounding fauna without benefiting from the interaction.

Solution approach

Correct Answer + Core Reason: Amensalism. Microcystis harms surrounding fauna without benefiting itself.

Step-by-Step Solution:
Step 1: Define the terms: Amensalism (one organism is harmed, the other is unaffected), Parasitism (one organism benefits, the other is harmed), Predation (one organism kills and eats another), Exploitation (one organism benefits by using another, but not necessarily killing it).
Step 2: Consider the relationship between Microcystis and surrounding fauna. Microcystis can release toxins.
Step 3: These toxins can harm or inhibit the growth of other organisms (fauna).
Step 4: Microcystis does not gain any benefit from harming the fauna. This fits the definition of amensalism.

Why other options are wrong:
- Option B: Parasitism requires one organism to benefit while harming the other. Microcystis doesn't benefit.
- Option C: Predation involves killing and eating. Microcystis doesn't kill and eat the fauna.
- Option D: Exploitation involves one organism benefiting from another. Microcystis doesn't benefit.

Key Concepts:
- Amensalism
- Ecological interactions

Memory Aids:
- Amensalism = A Menace, but no benefit to the menace-maker.

Quick Tips:
- Focus on whether both organisms are affected and how they are affected (benefit, harm, or no effect).

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A biologist studied the population of rats in a barn. He found that the average natality was 250, average mortality 240, immigration 20 and emigration 30. The net increase in population is

View answer and explanation

Correct option: B

Zero

The correct answer is Zero (B) because the net increase is calculated by (natality + immigration) - (mortality + emigration), which equals zero in this case.

Solution approach

Correct Answer + Core Reason: Zero. The net increase is calculated by (natality + immigration) - (mortality + emigration).

Step-by-Step Solution:

Step 1: Define population increase: Change in population size over time.

Step 2: Identify given values: Natality = 250, Mortality = 240, Immigration = 20, Emigration = 30.

Step 3: Apply the formula: Net increase = (Natality + Immigration) - (Mortality + Emigration).

Step 4: Substitute values: Net increase = (250 + 20) - (240 + 30).

Step 5: Calculate: Net increase = 270 - 270 = 0.

Why other options are wrong:
- Option A: 5 is incorrect; the correct calculation is 270 - 270 = 0.
- Option C: 10 is incorrect; the correct calculation is 270 - 270 = 0.
- Option D: 15 is incorrect; the correct calculation is 270 - 270 = 0.

Key Concepts:
- Population dynamics
- Natality
- Mortality
- Immigration
- Emigration

Memory Aids:
- Remember the formula: (Births + Immigration) - (Deaths + Emigration).

Quick Tips:
- Be careful with signs (positive for additions, negative for subtractions).

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Differentiation of various tissue and organs in response to light is called

View answer and explanation

Correct option: B

Photomorphogenesis

Option B (Photomorphogenesis) is correct because photomorphogenesis refers to the light-mediated development of plant form and structure.

Solution approach

Correct Answer + Core Reason: Photomorphogenesis. This term describes development in response to light.

Step-by-Step Solution:

Step 1: Define Morphogenesis: Morphogenesis is the biological process that causes an organism to develop its shape.

Step 2: Define Photomorphogenesis: Photomorphogenesis is morphogenesis influenced by light.

Step 3: Conclusion: Differentiation of tissues and organs in response to light is photomorphogenesis.

Why other options are wrong:
- Option A (Morphogenesis): Morphogenesis is a general term for development of form, but doesn't specifically refer to light.
- Option C (Organogenesis): Organogenesis is the process of organ formation, but doesn't specify light as the trigger.
- Option D (Embryogenesis): Embryogenesis is the formation and development of an embryo, but doesn't specify light as the trigger.

Key Concepts:
- Morphogenesis
- Photomorphogenesis
- Plant Development

Memory Aids:
- Photo- = Light (think of photosynthesis)

Quick Tips:
- Remember that photomorphogenesis is light-dependent development.

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Halophytes are

View answer and explanation

Correct option: C

Salt-resistant

Option C (Salt-resistant) is correct because halophytes are plants that thrive in environments with high salt concentrations.

Solution approach

Correct Answer + Core Reason: Salt-resistant. Halophytes are adapted to saline environments.

Step-by-Step Solution:

Step 1: Define Halophytes: Halophytes are plants that can grow in soils with high salt concentrations.

Step 2: Understand Adaptation: These plants have adaptations to tolerate or exclude salt from their tissues.

Step 3: Conclusion: Halophytes are, by definition, salt-resistant.

Why other options are wrong:
- Option A (Fire-resistant): Fire-resistant plants are adapted to survive in fire-prone environments, not necessarily saline ones.
- Option B (Cold-resistant): Cold-resistant plants are adapted to survive in cold environments, not necessarily saline ones.
- Option D (Sand-loving): Sand-loving plants (psammophytes) are adapted to sandy soils, which may or may not be saline.

Key Concepts:
- Halophytes
- Salt Tolerance
- Plant Adaptations

Memory Aids:
- Halo- = Salt (think of halogen elements and salts)

Quick Tips:
- Remember that halophytes are specifically adapted to high-salt environments.

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Many parasites have evolved to be …A… in such a way that both host and the parasite tend to …B… that is, if the host evolves special mechanisms for rejecting or resisting the parasite, the parasite has to evolve mechanisms to …C… and neutralize them, in order to be successful with the same host species
Choose the correct option for A, B and C

View answer and explanation

Correct option: B

A-host-specific, B-coevolve, C-counteract

Option B (A-host-specific, B-coevolve, C-counteract) is correct because parasites evolve to be specific to their hosts, leading to coevolution where both host and parasite adapt, and parasites counteract host defenses.

Solution approach

Correct Answer + Core Reason: A-host-specific, B-coevolve, C-counteract. This option accurately describes the evolutionary arms race between parasites and hosts.

Step-by-Step Solution:

Step 1: Understand the scenario: Parasites and hosts engage in an evolutionary arms race.

Step 2: Define the terms:
- Host-specific: Adapted to a particular host species.
- Coevolve: Evolve together in response to each other.
- Counteract: Act against or neutralize.

Step 3: Fill in the blanks:
- Parasites evolve to be *host-specific*.
- Host and parasite *coevolve*.
- Parasites *counteract* host defenses.

Why other options are wrong:
- Option A (A-host-specific, B-evolve, C-counteract): While A and C are correct, B is better described as coevolution, not just evolution.
- Option C (A-source specific, B-coevolve, C-counteract): "Source-specific" is less accurate than "host-specific" in this context.
- Option D (A-source specific, B-evolve, C-counteract): Both A and B are less accurate than the corresponding terms in the correct answer.

Key Concepts:
- Parasitism
- Coevolution
- Host-parasite interactions

Memory Aids:
- Think of the host and parasite as being in a constant battle, each trying to outsmart the other.

Quick Tips:
- Look for the option that best describes the reciprocal evolutionary changes between host and parasite.

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The desert plants in order to tolerate water stress, show

View answer and explanation

Correct option: D

All of the above

Option D (All of the above) is correct because desert plants exhibit all these adaptations to minimize water loss and tolerate drought conditions.

Solution approach

Correct Answer + Core Reason: All of the above. Desert plants use all these adaptations to conserve water.

Step-by-Step Solution:

Step 1: Understand Water Stress: Desert plants face significant water stress due to arid conditions.

Step 2: Analyze the Adaptations:
- Sunken stomata reduce water loss through transpiration.
- Reduced leaves minimize surface area for transpiration.
- Well-developed root systems maximize water absorption.

Step 3: Conclusion: Desert plants show all of these adaptations to tolerate water stress.

Why other options are wrong:
- Option A (Sunken stomata): While sunken stomata are an adaptation, this option is incomplete as other adaptations also contribute.
- Option B (Reduced leaves): While reduced leaves are an adaptation, this option is incomplete as other adaptations also contribute.
- Option C (Well developed root system): While a well-developed root system is an adaptation, this option is incomplete as other adaptations also contribute.

Key Concepts:
- Xerophytes
- Plant Adaptations
- Water Conservation

Memory Aids:
- Think of all these adaptations working together to help plants survive in the desert.

Quick Tips:
- Remember that desert plants have multiple adaptations to deal with water scarcity.

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Which is the characteristics of desert plant adaptation?

View answer and explanation

Correct option: D

All of the above

Option D (All of the above) is correct because desert plants typically have thick cuticles, stomata in deep pits, and stomata that close during the day to conserve water.

Solution approach

Correct Answer + Core Reason: All of the above. These are all adaptations to reduce water loss in desert plants.

Step-by-Step Solution:

Step 1: Consider the challenges faced by desert plants: Water scarcity and high temperatures.

Step 2: Evaluate each characteristic:
- Thick cuticle on their leaf surface: Reduces water loss through transpiration.
- Stomata arranged in deep pits: Creates a humid microenvironment, reducing water loss.
- Stomata remain closed during day: Reduces water loss during the hottest part of the day.

Step 3: All three characteristics are adaptations to conserve water.

Why other options are wrong:
- Option A (Thick cuticle on their leaf surface): This is a correct adaptation, but not the only one.
- Option B (Stomata arranged in deep pits): This is a correct adaptation, but not the only one.
- Option C (Stomata remain closed during day): This is a correct adaptation, but not the only one.

Key Concepts:
- Desert adaptations
- Transpiration
- Stomata
- Cuticle

Memory Aids:
- Think of desert plants as trying to minimize water loss in every way possible.

Quick Tips:
- Remember that desert plant adaptations are all about conserving water.

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Resource partitioning includes

View answer and explanation

Correct option: D

All of the above

Option D (All of the above) is correct because resource partitioning can occur through temporal, spatial, and morphological differences in resource use.

Solution approach

Correct Answer + Core Reason: All of the above. Resource partitioning can occur through temporal, spatial, and morphological differences.

Step-by-Step Solution:

Step 1: Define Resource Partitioning: Resource partitioning is the process by which species divide a limited resource to avoid competition.

Step 2: Define Temporal Partitioning: Temporal partitioning involves using resources at different times.

Step 3: Define Spatial Partitioning: Spatial partitioning involves using resources in different locations.

Step 4: Define Morphological Partitioning: Morphological partitioning involves differences in body shape or size that allow species to use resources differently.

Step 5: Conclusion: All three options are valid forms of resource partitioning.

Why other options are wrong:
- Option A: Temporal partitioning is only one aspect of resource partitioning.
- Option B: Spatial partitioning is only one aspect of resource partitioning.
- Option C: Morphological partitioning is only one aspect of resource partitioning.

Key Concepts:
- Resource partitioning
- Competition
- Niche differentiation

Memory Aids:
- Resource Partitioning: Time, Space, Shape

Quick Tips:
- Remember the different ways species can divide resources to minimize competition.

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Concept of mimicry was given by …A…
Father of Indian Plant Ecology …B…
Term ‘ecology’ coined by …C…
Here A, B and C refers to

View answer and explanation

Correct option: B

A-HW Bates, B-Ramdev Mishra, C-Ernst Haeckel

Option B (A-HW Bates, B-Ramdev Mishra, C-Ernst Haeckel) is correct because HW Bates proposed the concept of mimicry, Ramdev Mishra is the Father of Indian Plant Ecology, and Ernst Haeckel coined the term 'ecology'.

Solution approach

Correct Answer + Core Reason: A-HW Bates, B-Ramdev Mishra, C-Ernst Haeckel. This matches the correct attributions for mimicry, Indian Plant Ecology, and the term 'ecology'.

Step-by-Step Solution:

Step 1: Recall the Contributions of Scientists: Consider the scientists and their contributions to ecology and related fields.

Step 2: Match the Scientists to the Concepts:
- Mimicry: HW Bates
- Father of Indian Plant Ecology: Ramdev Mishra
- Term 'Ecology': Ernst Haeckel

Step 3: Conclusion: The correct order is A-HW Bates, B-Ramdev Mishra, C-Ernst Haeckel.

Why other options are wrong:
- Option A: A-Haeckel, B-Ramdev Mishra, C-Reiter is incorrect because Haeckel coined the term ecology, not mimicry, and Reiter is not associated with the term ecology.
- Option C: A-HW Bates, B-Birbal Sahani, C-Ernst Haeckel is incorrect because Ramdev Mishra, not Birbal Sahani, is known as the Father of Indian Plant Ecology.
- Option D: A-HW Bates, B-Birbal Sahani, C-Reiter is incorrect because Ramdev Mishra, not Birbal Sahani, is known as the Father of Indian Plant Ecology, and Reiter is not associated with the term ecology.

Key Concepts:
- Mimicry
- Ecology
- History of Ecology

Memory Aids:
- Bates = Mimicry (think "Bates" and "baits" - mimicry can be a form of baiting or deception).
- Mishra = Indian Plant Ecology (think "Mishra" and "India").
- Haeckel = Ecology (think "Haeckel" and "Ecology" both start with "E").

Quick Tips:
- Memorize the key scientists and their contributions to ecology.

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Assertion (A): Small sized birds and mammals are rarely found in Polar Regions.

Reason (R): Small animals have large surface area relative to their volume, so that they can minimize loss of heat.

View answer and explanation

Correct option: C

A is true, R is false

The correct answer is C (A is true, R is false) because small-sized birds and mammals are rarely found in Polar Regions due to heat loss, and small animals have a large surface area to volume ratio, which *increases* heat loss.

Solution approach

Correct Answer + Core Reason: A is true, R is false. Small animals lose heat more easily, making polar regions difficult.

Step-by-Step Solution:

Step 1: Analyze the assertion: Small birds and mammals are rare in polar regions.

Step 2: Analyze the reason: Small animals have a large surface area relative to their volume, so that they can minimize loss of heat.

Step 3: Determine if the assertion is true: This is generally true due to heat loss challenges.

Step 4: Determine if the reason is true: This is false; a large surface area to volume ratio *increases* heat loss.

Why other options are wrong:
- Option A: The reason is false.
- Option B: The reason is false.
- Option D: The assertion is true.

Key Concepts:
- Bergmann's rule
- Surface area to volume ratio
- Heat loss
- Polar adaptations

Memory Aids:
- Remember that small animals lose heat faster due to their surface area to volume ratio.

Quick Tips:
- Relate body size to heat regulation in different climates.

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Which of the following is inappropriately defined? I. Host is an organism which provides only food, shelter to another organism II. Amensalism is a relationship in which one species is benefitted, whereas the other is unaffected III. Predator is an organism that catches and kills other organism for food of same species IV. Endo parasite is an organism which always lives inside the body of other organism and may kill it Select the correct option

View answer and explanation

Correct option: B

III and IV

Option D (I, III and IV) is incorrect because statement III is wrong; houseflies are r-selected species.

Solution approach

Correct Answer + Core Reason: III and IV. Statements III and IV are inappropriately defined.

Step-by-Step Solution:

Step 1: Analyze each statement:
- I. Host is an organism which provides only food, shelter to another organism - Correct.
- II. Amensalism is a relationship in which one species is benefitted, whereas the other is unaffected - Incorrect. Amensalism is when one species is harmed, and the other is unaffected.
- III. Predator is an organism that catches and kills other organism for food of same species - Incorrect. Predators kill organisms of *different* species.
- IV. Endo parasite is an organism which always lives inside the body of other organism and may kill it - Incorrect. It doesn't always kill the host.

Step 2: Identify the incorrectly defined statements: II, III, and IV.

Step 3: Select the correct option: The option containing II, III, and IV is the correct answer.

Step 4: Final Answer: III and IV

Why other options are wrong:
- Option A: Statement I is correctly defined.
- Option B: Statement I is correctly defined.
- Option C: Statement I is correctly defined.

Key Concepts:
- Ecological interactions
- Host
- Amensalism
- Predator
- Endoparasite

Memory Aids:
- Amensalism: 0/-
- Commensalism: +/0

Quick Tips:
- Carefully consider the definitions of each ecological interaction.

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A population interaction in which both species are benefitted is called

View answer and explanation

Correct option: D

Mutalism

Option D (Mutalism) is correct because mutualism is a relationship where both species involved benefit from the interaction (+,+).

Solution approach

Correct Answer + Core Reason: Mutalism. This interaction is defined as both species benefitting.

Step-by-Step Solution:

Step 1: Define Commensalism: Commensalism is a (+, 0) interaction where one species benefits, and the other is unaffected.

Step 2: Define Ammensalism: Ammensalism is a (0, -) interaction where one species is unaffected, and the other is harmed.

Step 3: Define Predation: Predation is a (+, -) interaction where one species benefits (the predator) and the other is harmed (the prey).

Step 4: Define Mutalism: Mutalism is a (+, +) interaction where both species benefit.

Step 5: Match the definition: The question describes a (+, +) interaction, which matches the definition of mutualism.

Why other options are wrong:
- Option A: Commensalism requires only one species to benefit.
- Option B: Ammensalism requires one species to be harmed.
- Option C: Predation requires one species to be harmed.

Key Concepts:
- Population interactions
- Mutualism, Commensalism, Parasitism, Predation, Ammensalism

Memory Aids:
- Mutual = Both benefit

Quick Tips:
- Remember the symbols (+, -, 0) to represent the effects of interactions on each species.

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Organisms which breed only once in their lifetime

View answer and explanation

Correct option: C

Both (1) and (2)

Option C (Both (1) and (2)) is correct because both Pacific salmon fish and bamboo are examples of organisms that reproduce only once in their lifetime (semelparity).

Solution approach

Correct Answer + Core Reason: Both (1) and (2). Both Pacific salmon and bamboo reproduce only once in their lifetime.

Step-by-Step Solution:

Step 1: Define Semelparity: Semelparity is a reproductive strategy where an organism reproduces only once in its lifetime.

Step 2: Identify Examples: Pacific salmon fish and bamboo are well-known examples of semelparous organisms.

Step 3: Conclusion: Both Pacific salmon and bamboo breed only once in their lifetime.

Why other options are wrong:
- Option A (Pacific salmon fish): While Pacific salmon fish are semelparous, this option is incomplete as bamboo is also semelparous.
- Option B (Bamboo): While bamboo is semelparous, this option is incomplete as Pacific salmon fish are also semelparous.
- Option D (None of these): Both Pacific salmon and bamboo are examples of organisms that breed only once in their lifetime.

Key Concepts:
- Semelparity
- Reproductive Strategies
- Life History Traits

Memory Aids:
- Semel- = Once (think of "single")

Quick Tips:
- Remember that semelparity is a reproductive strategy involving a single reproductive event.

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Remembering +4 | -1

Radiation below the visible range are called

View answer and explanation

Correct option: A

UV

Option A (UV) is correct because ultraviolet (UV) radiation lies below the visible range in the electromagnetic spectrum.

Solution approach

Correct Answer + Core Reason: UV. Radiation below the visible range is UV.

Step-by-Step Solution:

Step 1: Describe the electromagnetic spectrum.\nThe electromagnetic spectrum includes various types of radiation, including radio waves, infrared (IR), visible light, ultraviolet (UV), X-rays, and gamma rays.

Step 2: Position of UV radiation.\nUV radiation has shorter wavelengths and higher frequencies than visible light, placing it below the visible range.

Why other options are wrong:
- Option B: IR (Infrared) radiation lies above the visible range, having longer wavelengths and lower frequencies.
- Option C: Both (a) and (b) is incorrect because only UV radiation lies below the visible range.
- Option D: Radiowaves have much longer wavelengths than visible light and are not below the visible range in the spectrum.

Key Concepts:
- Electromagnetic spectrum
- UV radiation
- IR radiation
- Visible light

Memory Aids:
- Remember the order of the electromagnetic spectrum: Radio waves, Microwaves, Infrared, Visible, Ultraviolet, X-rays, Gamma rays.

Quick Tips:
- Understand the relative positions of different types of radiation in the electromagnetic spectrum.

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Mycorrhiza is a mutualistics association of plants root with fungi. The association occurs in

View answer and explanation

Correct option: D

All of these

Option D (All of these) is correct because mycorrhizal associations are common in dicots, monocots, and nearly all gymnosperms.

Solution approach

Correct Answer + Core Reason: Mycorrhizal associations occur in all the listed plant groups.

Step-by-Step Solution:

Step 1: Define Mycorrhiza: Mycorrhiza is a symbiotic association between a fungus and the roots of a plant.

Step 2: Describe the association in dicots: Mycorrhizal associations are common in many dicot species.

Step 3: Describe the association in monocots: Mycorrhizal associations are also found in a significant percentage of monocot species.

Step 4: Describe the association in gymnosperms: Nearly all gymnosperms form mycorrhizal associations, which are crucial for nutrient uptake.

Step 5: Combine the information: Since the association occurs in dicots, monocots, and gymnosperms, the correct answer is all of these.

Why other options are wrong:
- Option A: While mycorrhizae are common in dicots, it's not exclusive to them.
- Option B: While mycorrhizae are present in monocots, it's not exclusive to them.
- Option C: While mycorrhizae are common in gymnosperms, the question asks for all groups where it occurs.

Key Concepts:
- Mycorrhiza
- Symbiosis
- Plant-fungus interactions

Memory Aids:
- Myco = fungus, rhiza = root

Quick Tips:
- Remember that mycorrhizae enhance nutrient uptake for plants.

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Understanding +4 | -1

Factors which determine to the large extent the vegetation of any area are I. pH of soil II. mineral composition of the soil III. water holding capacity of soil IV. weather condition Choose the correct option

View answer and explanation

Correct option: D

I, II, III and IV

Option D (I, II, III and IV) is correct because pH, mineral composition, water holding capacity, and weather conditions all significantly influence vegetation.

Solution approach

Correct Answer + Core Reason: I, II, III and IV. All the listed factors determine the vegetation of an area.

Step-by-Step Solution:

Step 1: Consider each factor individually:
- I. pH of soil: Affects nutrient availability to plants.
- II. Mineral composition of the soil: Provides essential nutrients for plant growth.
- III. Water holding capacity of soil: Determines water availability for plants.
- IV. Weather condition: Affects temperature, sunlight, and precipitation, all crucial for plant growth.

Step 2: Recognize that all these factors are important for plant growth and distribution.

Step 3: Conclude that all options are correct.

Why other options are wrong:
- Option A (I and II): This is incomplete as it omits water holding capacity and weather conditions.
- Option B (II and III): This is incomplete as it omits pH and weather conditions.
- Option C (I, II and III): This is incomplete as it omits weather conditions.

Key Concepts:
- Soil properties
- Weather conditions
- Plant growth requirements

Memory Aids:
- Remember that plants need the right pH, minerals, water, and weather to thrive.

Quick Tips:
- When in doubt, consider the holistic needs of plants.

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Analyzing +4 | -1

A female fig wasp enters the syconium of a fig, pollinates the flowers and lays eggs in the ovaries of some of the flowers. The young larvae grow up, eat (and kill) some, but not all of the seeds and complete their life cycle.
The fig is completely dependent on fig wasps to pollinate its flowers and the fig wasp requires figs to complete its life cycle
The interaction between figs and fig wasps has aspects of
I. mutualism
II. host-parasite interaction
III. competition
IV. ammensalism
V. protocooperation
Select the correct option

View answer and explanation

Correct option: A

I and II

Option A (I and II) is correct because the fig and fig wasp interaction involves both mutualism (pollination) and host-parasite interaction (larvae eating seeds).

Solution approach

Correct Answer + Core Reason: I and II. The fig and fig wasp interaction involves both mutualism and host-parasite interaction.

Step-by-Step Solution:

Step 1: Analyze the interaction: The fig wasp pollinates the fig flowers (mutualism). The fig wasp larvae eat some of the fig seeds (host-parasite interaction).

Step 2: Identify the relevant interactions:
- I. Mutualism: Both species benefit (fig gets pollinated, wasp gets a place to lay eggs).
- II. Host-parasite interaction: The wasp larvae consume fig seeds, harming the fig.
- III. Competition: Not a primary aspect of the interaction as described.
- IV. Ammensalism: One species is harmed, the other unaffected. Not the case here.
- V. Protocooperation: Both benefit, but the relationship is not obligatory. Mutualism is a better fit.

Step 3: Select the correct option: I and II are the most accurate descriptions of the interaction.

Step 4: Final Answer: I and II

Why other options are wrong:
- Option B: Competition is not a primary aspect of this interaction.
- Option C: Protocooperation is less precise than mutualism in this case.
- Option D: Neither competition nor ammensalism are the best descriptions of this interaction.

Key Concepts:
- Mutualism
- Host-parasite interaction
- Ecological interactions

Memory Aids:
- Mutualism: +/+
- Parasitism: +/-

Quick Tips:
- Carefully analyze the benefits and harms to each species involved in the interaction.

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Remembering +4 | -1

Ratio between mortality and natality is called

View answer and explanation

Correct option: B

Vital index

Option B (Vital index) is correct because the vital index is calculated as the ratio of natality (birth rate) to mortality (death rate).

Solution approach

Correct Answer + Core Reason: Vital index. Vital index is the ratio between natality and mortality.

Step-by-Step Solution:

Step 1: Define Natality and Mortality: Natality is the birth rate, and mortality is the death rate in a population.

Step 2: Define Vital Index: Vital index is a measure of population growth calculated as (Natality / Mortality) * 100.

Step 3: Conclusion: The ratio between mortality and natality is called the vital index.

Why other options are wrong:
- Option A: Population ratio is a general term and doesn't specifically refer to the ratio of natality to mortality.
- Option C: Density coefficient is a measure of population density, not the ratio of birth and death rates.
- Option D: Census ratio is not a standard ecological term related to natality and mortality.

Key Concepts:
- Natality
- Mortality
- Vital Index
- Population Ecology

Memory Aids:
- Vital index = (Births / Deaths) * 100. Think of "vital" as relating to life (births) and death.

Quick Tips:
- Remember the formula for vital index: (Natality / Mortality) * 100.

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The term ‘Niche’ was first used by

View answer and explanation

Correct option: B

Grinnel

Option B (Grinnel) is correct because Joseph Grinnell was the first to use the term 'niche' in an ecological context.

Solution approach

Correct Answer + Core Reason: Grinnel. The term ‘Niche’ was first used by Grinnel.

Step-by-Step Solution:

Step 1: Recall the History of Ecology: Consider the scientists who have contributed to the development of ecological concepts.

Step 2: Identify the Correct Scientist: Remember that Grinnel introduced the concept of the niche.

Step 3: Conclusion: Grinnel was the first to use the term 'niche' in ecology.

Why other options are wrong:
- Option A: Elements is incorrect because it is not associated with the initial use of the term 'niche'.
- Option C: Warming is incorrect because it is not associated with the initial use of the term 'niche'.
- Option D: Odum is incorrect because while Eugene Odum made significant contributions to ecology, he did not originate the term 'niche'.

Key Concepts:
- Ecological Niche
- History of Ecology

Memory Aids:
- Associate "Grinnel" with the "genesis" (beginning) of the niche concept.

Quick Tips:
- Remember key figures associated with fundamental ecological concepts.

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B-horizon is also called

View answer and explanation

Correct option: C

Sub-soil region

Option C (Sub-soil region) is correct because the B-horizon is also known as the sub-soil region.

Solution approach

Correct Answer + Core Reason: Sub-soil region. B-horizon is also called Sub-soil region.

Step-by-Step Solution:

Step 1: Define soil horizons.\nSoil horizons are layers of soil with distinct characteristics.

Step 2: Describe the B-horizon.\nThe B-horizon, or subsoil, is located below the A-horizon and is characterized by the accumulation of minerals leached from above.

Why other options are wrong:
- Option A: Top soil region refers to the A-horizon.
- Option B: Below soil region is a vague term and not specifically associated with the B-horizon.
- Option D: Upper soil region refers to the A-horizon or O-horizon.

Key Concepts:
- Soil horizons
- B-horizon (subsoil)

Memory Aids:
- O-A-B-C (Order of soil horizons from top to bottom)

Quick Tips:
- Remember the order of soil horizons and their general characteristics.

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Analyzing +4 | -1

If a person moves from plains to hill station,
where atmospheric pressure is about 200 mm Hg
less than that at sea level, after 14 months
A. There will be difficulty in breathing
B. The value of

p{O_2}

in blood will increase
C. The number of RBCs increases in that person
Select the option that is correct for that acclimatized person.

View answer and explanation

Correct option: D

Only C is correct

Option D is correct because only the increase in the number of RBCs (C) is the correct adaptation to lower atmospheric pressure at a hill station after acclimatization.

Solution approach

Correct Answer + Core Reason: Only C is correct. Acclimatization to high altitude involves increased RBC production to compensate for lower oxygen availability.

Step-by-Step Solution:

Step 1: Understand the scenario: A person moving from plains to a hill station experiences lower atmospheric pressure, leading to reduced oxygen availability.

Step 2: Analyze option A: Initially, there will be difficulty in breathing (hypoxia) due to lower oxygen partial pressure. However, after acclimatization (14 months), the body adapts, and breathing becomes easier, not more difficult. So, A is incorrect.

Step 3: Analyze option B: The value of $p{O_2}$ (partial pressure of oxygen) in the blood will initially decrease due to lower atmospheric pressure. After acclimatization, the body tries to maintain oxygen delivery, but the $p{O_2}$ doesn't increase above normal levels. So, B is incorrect.

Step 4: Analyze option C: The body responds to lower oxygen availability by producing more red blood cells (RBCs). This increases the oxygen-carrying capacity of the blood, compensating for the lower oxygen partial pressure. This is a key adaptation to high altitude. So, C is correct.

Why other options are wrong:
- Option A: Difficulty in breathing is a short-term effect, not a long-term adaptation.
- Option B: $p{O_2}$ in blood does not increase after acclimatization; the body compensates by increasing RBC count.
- Option A and B: Both A and B are incorrect as they describe initial symptoms, not long-term adaptations.
- Option B and C: B is incorrect, so this option is incorrect.

Key Concepts:
- Acclimatization to high altitude.
- Hypoxia: Low oxygen levels.
- Erythropoiesis: Production of red blood cells.
- Partial pressure of oxygen ( $p{O_2}$ )

Memory Aids:
- Remember that increased RBC production is a key adaptation to high altitude.

Quick Tips:
- Understand the physiological responses to changes in altitude and oxygen availability.

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Large size of pinnae in animals of warm region in comparison to animal of cold region is due to

View answer and explanation

Correct option: D

Allen’s rule

Option D (Allen’s rule) is correct because Allen's rule states that animals in warmer climates tend to have larger appendages to dissipate heat.

Solution approach

Correct Answer + Core Reason: Allen’s rule. Allen's rule explains the relationship between body shape and climate.

Step-by-Step Solution:

Step 1: Understand Allen's Rule: Allen's rule states that endothermic animals from colder climates usually have shorter limbs or appendages than equivalent animals from warmer climates.

Step 2: Apply the Rule: Larger pinnae (ears) in warm regions increase surface area for heat dissipation, which is consistent with Allen's rule.

Step 3: Conclusion: The large size of pinnae in animals of warm regions is an adaptation to facilitate heat loss, as described by Allen's rule.

Why other options are wrong:
- Option A (Dollo’s law): Dollo's law states that evolution is not reversible; once a structure is lost, it cannot be regained in the same form. This is not related to pinnae size.
- Option B (Gloger’s law): Gloger's law relates to pigmentation; animals in warmer, more humid climates tend to be more heavily pigmented than those in colder, drier climates. This is not related to pinnae size.
- Option C (Cope’s law): Cope's law states that animal lineages tend to increase in body size over evolutionary time. This is not related to pinnae size.

Key Concepts:
- Allen's Rule
- Adaptation to Climate
- Heat Dissipation

Memory Aids:
- Allen = Appendages (think of Allen's rule relating to appendages)

Quick Tips:
- Remember that Allen's rule deals with the size and shape of appendages in relation to climate.

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Statement I: In nature, animals. plants, and microbes do not and cannot live in isolation.

Statement II: For any species. the minimal requirement is one more species on which it can feed.

View answer and explanation

Correct option: A

Both statements I and II are correct and II explains I

Option A (Both statements I and II are correct and II explains I) is correct because organisms in nature are interconnected, and at least one other species is needed for food.

Solution approach

Correct Answer + Core Reason: Both statements I and II are correct and II explains I. Organisms in nature are interconnected, and at least one other species is needed for food.

Step-by-Step Solution:

Step 1: Analyze Statement I: In nature, animals, plants, and microbes do not and cannot live in isolation. This is true because organisms are interconnected through food webs and other interactions.

Step 2: Analyze Statement II: For any species, the minimal requirement is one more species on which it can feed. This is also true, as all organisms need a source of energy, often another species.

Step 3: Determine if Statement II explains Statement I: Statement II explains why organisms cannot live in isolation, as they need other species for food.

Step 4: Final Answer: Both statements I and II are correct and II explains I

Why other options are wrong:
- Option B: Statement II *does* explain Statement I.
- Option C: Both statements are true.
- Option D: Both statements are true.

Key Concepts:
- Ecological interactions
- Food webs
- Interdependence of species

Memory Aids:
- Organisms are interconnected through food webs.

Quick Tips:
- Consider the flow of energy and nutrients through ecosystems to understand species interdependence.

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Application +4 | -1

A protozoan reproduces by binary fission. What will be the number of protozoans in its population after six generations?

View answer and explanation

Correct option: C

64

Option C (64) is correct because with binary fission, each protozoan divides into two. After six generations, the population will be 2 to the power of 6, which equals 64.

Solution approach

Correct Answer + Core Reason: 64. Binary fission results in exponential growth: $2^6 = 64$ .

Step-by-Step Solution:

Step 1: Understand Binary Fission. Binary fission is a type of asexual reproduction where one cell divides into two identical cells.

Step 2: Apply Exponential Growth. After each generation, the number of protozoans doubles. The formula for population size after $n$ generations is $N = N_0 \times 2^n$ , where $N_0$ is the initial population size (in this case, 1) and $n$ is the number of generations.

Step 3: Calculate Population Size. After 6 generations, the population size will be $1 \times 2^6$ .

Step 4: Calculate $2^6$ . $2^6 = 2 \times 2 \times 2 \times 2 \times 2 \times 2 = 64$ .

Why other options are wrong:
- Option A: 128 is $2^7$ , which would be after 7 generations, not 6.
- Option B: 24 is incorrect; it seems to be a miscalculation or misunderstanding of exponential growth.
- Option D: 32 is $2^5$ , which would be after 5 generations, not 6.

Key Concepts:
- Binary Fission: Asexual reproduction where one cell divides into two.
- Exponential Growth: Growth that occurs when the growth rate is proportional to the current size.

Memory Aids:
- Remember that binary fission doubles the population each generation.

Quick Tips:
- Use the formula $N = N_0 \times 2^n$ for calculating population size after binary fission.

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