Ecological Principles MCQ Quiz - Objective Question with Answer for Ecological Principles - Download Free PDF

The correct answer is It is unaffected by the evenness of species abundances.

Concept:

• The Shannon-Wiener diversity index is a widely used measure for quantifying species diversity in an ecosystem. It accounts for both species richness (the number of species present) and species evenness (how evenly the individuals are distributed among the species).

•  The formula for the Shannon index (H) is often expressed as:

• In the Shannon index, p is the proportion (n/N) of individuals of one particular species found (n) divided by the total number of individuals found (N), ln is the natural log, Σ is the sum of the calculations, and s is the number of species. 
• The higher the Shannon index, the greater the diversity in a community.
• This index gives higher values when there is greater species richness and evenness, indicating a more diverse ecosystem.

Explanation of the Correct Answer:

• It is unaffected by the evenness of species abundances is incorrect because the Shannon-Wiener diversity index incorporates species evenness into its calculations. Evenness refers to how similar the abundance of different species is within the ecosystem. 
• If abundances are very uneven (e.g., one species is super abundant and others are rare), the p_i(lnp_i)​ term for the dominant species will heavily influence the sum, leading to a lower diversity value.
• The index is sensitive to both richness and evenness. Ecosystems where species are more evenly distributed yield higher index values compared to those where one or a few species dominate.

Brief Overview of Other Options:

• Option 1: "It increases as species richness increases." This is correct because the Shannon-Wiener index rises when more species are present. Greater species richness contributes positively to the index value.
• Option 2: "It is maximized when all species have equal abundances." This is correct because the index reaches its maximum value when all species in the ecosystem have equal proportions (maximum evenness). This state represents the highest level of diversity.
• Option 4: "A low index value indicates dominance of one or a few species." This is correct because ecosystems with low diversity (where one or a few species dominate) yield low Shannon-Wiener index values. Such dominance reduces both richness and evenness.

The correct answer is Only when S1 > [(E1h2) / E2] - h1

Concept:

• Optimal Foraging Theory (OFT) is a model of how animals make decisions about where and what to eat. The model predicts that an animal acts in such a way as to maximize the net energy gained from foraging while minimizing the risks and energy expenditure involved. In other words, an animal will try to get the most food while using the least amount of effort and minimizing risk such as predation.

Main components of the OFT:-

• Energy Currency: The currency is typically the amount of usable energy an animal obtains from its food, minus the energy it uses up in the act of foraging. Energy obtained from food is dependent on the quality and quantity of the food, while energy spent while foraging can include physically searching for, pursuing, and handling the food.
• Decision Variables: These are the factors that an animal can affect to optimize its energy balance. They might include things like which type of food to pursue, where to look for that food, and whether to eat a found piece of food immediately or to continue foraging.
• Constraints: These are factors that limit the animal's ability to optimize its energy balance. They might include factors like predation risk or physiological limitations such as digestion speed.

• The profitability of the prey items is dependent on:
  • E- the amount of energy prey provides to the predator.
  • Handling time (h): time taken by the predator to handle the food. 
  • Search time (S): time taken by the predator to find prey.
  • The profitability of the prey item is given by - E/h.

The correct answer is B only

Concept:

• A bipartite network represents interactions between two distinct sets of entities or groups, such as species in two different trophic levels (e.g., predators-prey, pollinators-plants, frugivores-plants).
• In the given network, links represent interactions between species in the higher trophic level (A to H) and species in the lower trophic level (I to P).
• Each link represents a dependency or interaction. The presence or absence of links, as well as their patterns, helps infer ecological roles, stability, and potential vulnerabilities in the system.

Explanation:

Statement A: "If the network represents predator species (A-H) and prey species (I-P), then D is an apex predator."

• An apex predator is a predator at the top of the food chain that has no natural predators of its own. In the given network, species D interacts with multiple species in the lower trophic level, but there is no evidence from the network alone to conclude that D is an apex predator. This statement is therefore incorrect.

Statement B: "If the network represents plant species (I-P) and pollinator species (A-H), then species I is more likely to experience local extinction than K."

• The likelihood of local extinction for a species can depend on its number of interactions or connections in the network.
• In the given network, species I has fewer interactions (fewer links) than species K, making it more vulnerable to disturbances or pollinator loss. This statement is correct.

Statement C: "The network is more stable if D is removed and the population size of O increases."

• Network stability depends on various factors, including the removal of key species and changes in population dynamics.
• Removing a highly connected species (a "hub" or "generalist") from a network typically decreases network stability because many other species depend on it. Species D is the most connected species in the higher trophic level.

Statement D: "If the network represents frugivore species (A-H) and plant species (I-P), then M is a keystone species."

• A keystone species has a disproportionately large effect on its ecosystem relative to its abundance or biomass.
• Species M (a plant) interacts with only 1 frugivores (D). M is not particularly highly connected or central in the network. 
   

The correct answer is (A) - (II), (B) - (III), (C) - (IV)

Explanation:

• Soil formation is a natural process influenced by climatic conditions, vegetation, and topography, which leads to the development of distinct soil types.
• The processes of soil formation, such as Gleization, Laterization, and Podzolization, are closely associated with specific climatic conditions and environmental factors.

Gleization:

• Gleization occurs in areas with poor drainage, leading to waterlogging and anaerobic conditions.
• This process is common in low-lying areas with high rainfall, where the accumulation of water restricts oxygen supply to the soil.

Laterization:

• Laterization is a soil formation process that occurs in humid tropical and subtropical regions with high temperatures and abundant rainfall.
• It results in the leaching of silica and accumulation of iron and aluminum oxides, forming laterite soils.

Podzolization:

• Podzolization takes place in cool, moist climates of mid-latitude regions, often under coniferous forests.
• It involves the leaching of organic acids and minerals, creating distinct soil horizons.

The correct answer is A and B

Explanation:

• A metapopulation, as described in the classical model by Richard Levins (1969, 1970), refers to a collection of subpopulations occupying discrete patches of habitat that are connected through the processes of extinction and recolonization.
• The classical metapopulation model assumes that subpopulations experience local extinctions and recolonizations and that their dynamics are largely independent from one another.
  • Condition A: Individual subpopulations should have realistic chances of both extinction and recolonization. This is a key characteristic of metapopulations.
    • Local extinctions occur due to factors such as environmental variability, predation, or resource limitations, but recolonization through dispersal ensures the persistence of the metapopulation as a whole.
  • Condition B: The dynamics of the various subpopulations should be largely independent. This independence ensures that local extinctions in one patch do not directly affect other patches, allowing the metapopulation to persist through recolonization processes.
• Both conditions A and B are essential to the classical metapopulation model

Incorrect Options:

• Condition C, which states that recolonization occurs mainly through dispersal from a mainland patch, is not a feature of the classical metapopulation model. This condition is characteristic of the "mainland-island" metapopulation model, not the classical model.
• Condition D, which states that population dynamics in the patches should be highly synchronous, is also incorrect. The classical metapopulation model assumes independence in the dynamics of subpopulations, which is the opposite of synchrony.

The correct answer is Dolphins.

Key Points 

• The Gangetic river dolphin is India's national aquatic animal and is popularly known as ‘Susu’.
• Dolphins are one of the oldest creatures in the world along with some species of turtles, crocodiles, and sharks.
  • The Ganges river dolphin was officially discovered in 1801.
  • Ganges river dolphins once lived in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Nepal, India, and Bangladesh. But the species is extinct from most of its early distribution ranges.
  • The Ganges river dolphin can only live in freshwater and is essentially blind.
  • They hunt by emitting ultrasonic sounds, which bounce off of fish and other prey, enabling them to “see” an image in their mind.
  • They are frequently found alone or in small groups, and generally a mother and calf travel together.
  • Calves are chocolate brown at birth and then have grey-brown smooth, hairless skin as adults.
  • Females are larger than males and give birth once every two to three years to only one calf.
• It is among the four freshwater dolphins in the world- the other three are:
  • The ‘Baiji’ is now likely extinct from the Yangtze River in China.
  • The ‘Bhutan’ of the Indus in Pakistan
  • The ‘Boto’ of the Amazon River in Latin America. 

Important Points 

• Vikramshila Gangetic Dolphin Sanctuary:
  • It is situated in the Bhagalpur district of Bihar, India.
  • The sanctuary is a 50 km stretch of the Ganges River from Sultanganj to Kahalgaon.
  • It was designated as a protected area for the endangered Gangetic dolphins in 1991.

Concept:

• Productivity is defined as the rate of biomass production per unit area.
• Primary productivity is the rate of biomass production per unit area by the primary producer. 
• The producer is any organism that produces food through photosynthesis. 
• The producer is the first level of the ecosystem that provides energy to all of the consumers in the ecosystem.
• The total amount of energy fixed by the producer through photosynthesis is referred to as gross primary productively (GPP).
• While the amount of energy that remains after respiration loss in the producer is referred to as Net primary productivity (NPP).
•  Hence, NPP = GPP - Respiration
• So, NPP is the actual biomass that is available for consumption by the primary consumers (heterotrophic organisms).
• The rate of production of new biomass by the primary consumers (heterotrophic organisms) is called secondary productivity.

Important Points

• Tropical rainforests, swamps and marshes, and algae beds and reefs are ecosystems with the highest Net primary productivity. 
• While open ocean and desert ecosystems have the lowest NPP. 
• It can be seen in the second graph where NPP is given in g/m²/yr. This graph demonstrates the average net primary productivity of different ecosystems.
• The third graph demonstrates the productivity in relation to the amount of area that type of ecosystem occupies on the Earth. It shows the annual world net primary production of the different ecosystems on the earth. 
• Open ocean has the largest percentage of world's annual NPP. i.e., the open ocean contributes 24.4% of the world's net primary productivity. This is because around 70% of the Earth’s surface is occupied by the ocean.
• The second highest world annual NPP is of  tropical rain forest (22%), followed by swamps and marshes (2.3%) and lastly algae beds and reefs (0.9%)
• So, the correct order of the ecosystem in increasing order of NPP is - algae beds and reefs (0.9%), swamps and marshes (2.3%), tropical rain forests (22%) and open oceans (24.4%). 

Hence, the correct answer is option 4.

The correct answer is Option 2 i.e. 14 130 56 200

Key Points

• The efficiency with which energy is transferred from one trophic level to the next is called ecological efficiency. 
• Energy transfer in the ecosystem is not efficient, as only almost 10% of energy is transferred to the next trophic level, while 90% of the energy is lost to the environment. 
• Due to non-predation death, egestion, and cellular respiration, a  notable amount (almost 80 -90 %)  of energy is lost to the environment.
• Ecological efficiency included various related efficiency, which is as follow: 

1. Exploitation efficiency/ consumption efficiency(CE)
   • It is defined as the percentage of food available at one trophic level that is consumed (ingested) by the consumers. at one trophic level. 
2. Assimilation efficiency (AE)
   • It is defined as the percentage of food assimilated across the gut wall and becomes incorporated into growth.
3. Net production efficiency (PE)
   • It is defined as the percentage of assimilated energy  that is converted into new biomass. 

Explanation:

• Given : Pn - 1 = 1000 kcal, I/Pn - 1 = 20%, A/I = 35% and Pn/A = 20%
• First we will find the amount ingested i.e., I.
• Now, we will find the amount assimilated
•  
• Ingestion =  Assimilated + Non-assimilated 
• Now, we will find the amount of biomass produced at the trophic level. 
• Lastly, we will find the amount of biomass lost in the respiration 
• The amount of biomass assimilated is used for carrying out respiration and also passed on to the next trophic level. 
• So, Pn = 14, NA = 130, R = 56 and I = 200

Hence, the correct answer is Option 2.

The correct answer is 622.

Concept:

The mark-recapture method to estimate the population size of grasshoppers. This method is based on the assumption that the ratio of marked to total individuals in the sample is the same as the ratio of marked to total individuals in the entire population.

The population size (N) can be estimated using the Lincoln-Petersen formula for each day:

𝑁 = (𝑀×𝐶)/𝑅
N=RM×C​

Where:M M" id="MathJax-Element-43-Frame" role="presentation" style="position: relative;" tabindex="0">​

• M is the total number of marked individuals in the population (before the recapture on that day),
• C is the total number of individuals captured on the day,
• R is the number of marked individuals in the recaptured sample.

Solution:

Day 2:

• M=40 (from day 1, all marked)
• C=60 (recaptured grasshoppers)
• R=4 (marked in the recapture sample)

Using the formula:

• N₂ = (40×60)/4 = 600

Day 3:

• M=40+(60−4)=96 (40 already marked, plus 56 newly marked grasshoppers)
• C=50 (recaptured grasshoppers)
• R=7 (marked in the recapture sample)

Using the formula:

• N₃ = (96×50)/7 =685.71≈686

Day 4:

• M=96+(50−7)=139 (96 already marked, plus 43 newly marked grasshoppers)
• C=25 (recaptured grasshoppers)
• R=6 (marked in the recapture sample)

Using the formula:

• N₄ = (139×25)/6 =579.17≈579

Average Population Size:
Now, the average population size can be calculated from the three estimates (N₂ ,N₃ ,N₄):

Mean = (600+686+579)/3 =1865/3 ≈ 621.67

Thus, the estimated population size based on the mean of the three observations is approximately 622 grasshoppers.

The correct answer is 30

Explanation:

Environmental filtering refers to the process by which certain species from a regional species pool are selected to be part of a local community based on their ability to thrive in specific environmental conditions. This filtering often results in a reduced number of species in the local community compared to the broader regional pool.

Factors to Consider:

1. Regional Species Pool: This is the total number of species available in a larger geographic area, which in this case comprises 60 species.
2. Local Species Pool: This is the subset of the regional pool that can persist and reproduce in the local environment. Due to environmental filtering, not all species in the regional pool will be suitable for the local conditions.
3. Environmental Filtering: The process typically reduces species richness in the local pool. Depending on the environmental constraints (e.g., soil type, climate, competition), many species may be excluded from the local community.

Local Species Pool:

Given that environmental filtering tends to significantly reduce the number of species that can coexist in a specific habitat, it’s reasonable to expect that the local species pool would be much smaller than the regional species pool. In many ecological contexts, the local species pool could be around half or less of the regional pool, especially in more specialized environments.

In this case, a local species pool of 30 species represents a significant filtering from the 60 species available in the regional pool, aligning well with the principles of environmental filtering.

Therefore, the likely local species pool of this community is 30.

The correct answer is Parapatric speciation

Concept:

• Speciation is the process by which independently evolving lineages, i.e., species, are formed.
• It involves the divergence of populations into distinct species through genetic differentiation and reproductive isolation.

Explanation:

• Parapatric Speciation:
  • This type of speciation occurs between adjacent populations within a broadly continuous habitat.
  • Unlike allopatric speciation, there is no physical barrier separating the populations.
  • Gene flow is reduced due to environmental gradients or differences in selection pressures across the habitat.
  • Over time, these differences can lead to reproductive isolation and the formation of new species.

Other Options (Incorrect):

• Allopatric Speciation:
  • Occurs when populations are geographically separated by physical barriers such as mountains, rivers, or oceans.
  • Isolation prevents gene flow between populations, leading to divergence and speciation.
• Peripatric Speciation:
  • Similar to allopatric speciation but involves a small population isolated at the edge of a larger population.
  • Genetic drift and selection pressures in the isolated population lead to rapid speciation.
• Sympatric Speciation:
  • Occurs without geographical separation.
  • New species arise within the same habitat through mechanisms such as polyploidy, sexual selection, or ecological niche differentiation.

The correct answer is Option 3 i.e.High edge-to-area ratio of the reserve

Concept:

• Conservation of biodiversity refers to the protection, upliftment, restoration and management of natural resources (flora and fauna). 
• The following are the objectives of biodiversity conservation:
• Conservation of species diversity.
• Sustainable use of ecosystem and species.

Biodiversity conservation can be divided into two - 

1. In-situ conservation - The preservation of species in their natural habitat is referred to as in-situ conservation of biodiversity. The natural ecology is preserved and safeguarded using this technique.
   • National park - It is a reserve of land protected by the government where human activities like hunting, grazing, and farming are strictly prohibited. For e.g., Kaziranga National Park, Assam, Periyar National Park, Kerala, etc.
   • Biological reserves -Biosphere reserves are protected regions where native wildlife and domesticated flora and animals are all safeguarded. Human activities like tourism and research are allowed here.
   • Wildlife sanctuaries - In the region, only wildlife is protected. Human activities like logging, farming, the gathering of woods and other forest products are permitted here as long as they do not interfere with conservation initiatives. Tourism is allowed here as well. 
2. Ex-situ conservation - ​The conservation of biodiversity out of its natural habitat is called ex-situ conservation. Zoos, botanical gardens, gene banks, nurseries, etc. are a few examples of ex-situ conservation. ​

Explanation:

Option 1: 

• Generally, reserves that are connected by wildlife corridors are better than non-connected reserves. 
• Hence, this is an incorrect option. 

Option 2: 

• A reserve should have one or more buffer zone rings around the core areas.
• The buffer zone protects the core area from human activities thereby preserving the habitat and thus the species inhabiting the core areas as well
• Hence, this is an incorrect option. 

Option 3: 

• An ideal reserve should have a low edge-to-area ratio. 
• Because if the edge-to-area ratio is low then the amount of area that is subjected to edge conditions is also less.
• The edges of the forest are more subjected to harsh conditions like higher temperatures, lower humidity, etc, and some species cannot tolerate these conditions and cannot survive on the edge of the reserve. 
• So it is ideal that the reserve is compacted with a round shape instead of an elongated shape so as to minimise land area experiencing edge conditions. 
• Hence, this is the correct option. 

Option 4: 

• Ideally, a nature reserve should have a perfect circle shape because it reduces dispersal distances and avoids detrimental edge effects. 
• Hence, this is an incorrect option.

Hence, the correct answer is Option 3.

The correct answer is A, B and D

Key Points

• The survival of plants depends on their ability to make the most of the sunlight received from the sun. 
• Through the process of photosynthesis, plants capture light energy and convert it into food, to survive. 
• To adequately capture this valuable resource, plant leaves have adapted to survive in shade as well as the sun. 
• The leaves found at the top of the canopy and received direct sunlight are called sun leaves while the leaves that are present below the canopy (shaded region) and do not receive direct sunlight are called shade leaves.

Sun leaves and shade leaves can interchange as per the situation of the sunlight. 

1. Higher amount of chlorophyll per dry weight: Shade leaves generally have higher levels of chlorophyll per unit dry weight. This is because they need to maximize light absorption in low-light conditions. More chlorophyll allows them to capture the limited light available more efficiently for photosynthesis.
2. Lower density of stomata: Shade leaves typically have a lower density of stomata compared to sun leaves. Stomata are the pores on leaf surfaces through which gas exchange occurs. In shaded environments, water loss through transpiration is less of a concern, so having fewer stomata helps conserve water without significantly affecting CO₂ uptake for photosynthesis.​
3. Thicker leaves: Sun leaves are usually thicker than shade leaves. Thicker leaves have more cell layers, including a well-developed palisade layer, which can help protect against intense sunlight and reduce water loss. Shade leaves, on the other hand, tend to be thinner because they do not need as much structural reinforcement and want to maximize the light captured by each cell layer.

4. Lower rates of dark respiration per unit area: Shade leaves generally exhibit lower rates of dark respiration per unit area. Dark respiration is the process by which plants consume oxygen and produce CO₂ in the absence of light, using up energy reserves. Lower dark respiration rates in shade leaves help conserve energy, which is important in low-light environments where energy production through photosynthesis is limited.

Explanation:

• High amount of chlorophyll per dry weight is found in the shade leaves.
• Lower density of stomata is found in the shade leaves as compared to sun leaves.
• Sun leaves are thicker.
• Lower rates of dark respiration per unit area is found in shade leaves.
• So, statements A, B, and D are correct regarding the shade leaves.

Hence, the correct answer is option 3.

The correct answer is Tropical Forest > Temperate Forest > Tundra > Desert

Explanation:

1. Net Primary Productivity (NPP): The rate at which plants in an ecosystem produce net useful chemical energy; it is equal to the difference between the total energy captured through photosynthesis (Gross Primary Productivity, or GPP) and the energy respired by the plants. Typically measured in grams of carbon per square meter per year 
2. Leaf Area Index (LAI): A dimensionless quantity that characterizes plant canopies. It is defined as the total one-sided leaf area per unit ground surface area.
3. Season Length: The duration of the growing season, usually defined as the period of time each year during which the climatic conditions are suitable for plant growth. This might be the number of days in a year when temperature and moisture conditions allow the plants to grow.
4. NPP per Day per Unit Area: The average amount of net primary productivity produced per day by each square meter of land area in an ecosystem.

Calculation: Calculated by dividing the annual NPP by the season length. This gives a measure of the productivity rate without adjusting for the leaf area index (LAI).

Ecosystem Order According to NPP per Day per Unit Area. Based on the calculated values of NPP per day per unit area, here's the order for the given ecosystems from highest to lowest:

• Tropical Forest: 6.80 g m^-2 day^-1
• Temperate Forest: 6.20 g m^-2 day^-1
• Desert: 2.50 g m^-2 day^-1
• Tundra: 1.80 g m^-2 day^-1

Key Points 

• Desert ecosystems have a high NPP per day per unit LAI despite having relatively low overall productivity because their leaf area is highly efficient at converting available resources into biomass during their short growing season.
• Tundra follows, with relatively high efficiency in terms of daily productivity per unit leaf area, although the short growing season and low total leaf area limit overall productivity.
• Tropical Forest shows high annual productivity overall, but when broken down on a per day per unit leaf area basis, it's lower than desert or tundra because the high total leaf area dilutes the daily productivity rate.
• Temperate Forest has similar LAI to tropical forests but shorter growing seasons, resulting in slightly lower NPP per day per unit LAI compared to tropical forests.

Thus, the correct order of decreasing NPP per day per unit leaf area among the given ecosystems is Tropical Forest > Temperate Forest > Tundra > Desert

The correct answer is Mortality and reproduction are strongly dependent on population density.

Explanation:

r-selected species are characterized by traits that favor rapid reproduction and quick population growth, particularly in unstable or unpredictable environments. Here’s a breakdown of the traits:

1. Mortality and reproduction are strongly dependent on population density: This statement is NOT characteristic of r-selected species. Instead, r-selected species typically experience less regulation of their mortality and reproduction by population density. They often thrive in conditions where resources are abundant, allowing them to reproduce rapidly without the constraints of high competition or density-dependent factors.

2. Tend to occupy habitats that are unpredictable and/or ephemeral: This statement is characteristic of r-selected species. They often inhabit environments that are unstable, which require quick colonization and rapid life cycles.

3. Thrive in habitats where resource competition is low: This is also characteristic of r-selected species. They often exploit resources quickly and can thrive in environments with little competition.

4. Have superior capabilities to colonize new habitats: This is characteristic of r-selected species. They are typically adapted for rapid dispersal and colonization, allowing them to establish populations in new or disturbed areas quickly.

Conclusion: Therefore, the trait that is NOT characteristic of r-selected tree species is Mortality and reproduction are strongly dependent on population density.