Community Ecology MCQ Quiz - Objective Question with Answer for Community Ecology - Download Free PDF

The correct answer is populations < communities < ecosystems < biomes

Explanation:

The correct order of increasing biological organization reflects how living organisms and their environments are grouped, from the smallest unit (populations) to the largest (biomes). 

• Populations: A population consists of individuals of the same species living in a specific area and capable of interbreeding. It represents the lowest level of organization in this context.
• Communities: A community consists of all the different populations of various species living and interacting in a particular area. Communities represent interactions among multiple species.
• Ecosystems: An ecosystem includes the biological community (living organisms) and the physical environment (non-living components like air, water, and soil) in which they interact. Ecosystems are broader than communities as they encompass both biotic (living) and abiotic (non-living) components.
• Biomes: A biome is a large-scale ecological area that contains multiple ecosystems with similar climatic conditions and characteristic communities of plants, animals, and other organisms. Examples include tropical rainforests, deserts, and tundras. Biomes represent the largest scale of biological organization in this list.:.

Conclusion: The correct order of increasing biological organization is: populations < communities < ecosystems < biomes.

The correct answer is A and D

Explanation:

Competition between two species can lead to various outcomes depending on how the species interact and utilize resources. Two possible results of species competition are niche differentiation and character displacement. Both of these phenomena help species to coexist by reducing direct competition over resources.

Analysis of the statements:

1. Niche differentiation between species: This is a common outcome of competition where species evolve to occupy different niches, minimizing competition. This is a possible outcome of species competition.
2. Expansion of fundamental niche of both species: This is less likely as fundamental niches are defined by the physical environment rather than competition. Competition typically limits or differentiates niches, rather than expanding them.
3. Expansion of realized niche of both species: This is also not a typical outcome of competition. Realized niches are usually smaller due to competition, and competition rarely leads to the expansion of the realized niche for both species.
4. Character displacement between species: This is an evolutionary outcome where differences in physical traits become more pronounced due to competition. It helps species to reduce competition by allowing them to exploit different resources. This is another valid outcome of species competition. 

• Character displacement is the term used to describe an evolutionary change that occurs when two similar species inhabit the same environment.
• Under such conditions, natural selection favors a divergence in the characteristics--morphology, ecology, behavior, or physiology--of the organisms.
• The best example of Character displacement is  in the Galapagos Islands, a group of coexisting finches have distinctly different body and beak sizes as well as beak shapes.
• Moreover, character displacement in traits associated with resource use (ecological character displacement) has been studied largely independently of that in traits associated with reproduction (reproductive character displacement).

Character displacement is indicated when the difference between species in mean trait value is greater after selection ( d _A ) than before selection ( d _B ). 

Key Points

• Niche differentiation and character displacement are likely outcomes of competition between species, allowing coexistence by reducing direct competition.
• Expansion of fundamental or realized niches is not commonly associated with competition between species.

The correct answer is Pontederia crassipes, Salvinia molesta, Alternanthera philoxeroides.

Explanation:

The plants listed below are major non-native invasive species of aquatic ecosystems in India:

The correct answer is Option 1

Explanation:

a. The competitive exclusion principle, also known as Gause's law, states that two species that compete for the exact same resources cannot stably coexist. One of the two competitors will always have a slight advantage over the other that leads to better survival and reproduction, eventually leading to the decline in the population of the less competitive species. This principle is central in ecology, emphasizing the importance of niche differentiation for species coexistence.

b. This statement is incorrect. A niche describes the role an organism plays in its community, including its interactions with other organisms and its environment, not just the physical space it occupies. A niche encompasses various aspects such as the range of temperatures that an organism can tolerate, the type of food it consumes, where it prefers to live, and its role in energy and nutrient cycles within its habitat. Hence, a niche is often referred to as an organism's "ecological role."

c. This statement is incorrect. The term "ecospecies" is not standard in the terminology of ecology or taxonomy. Species can have various forms (including ecotypes or morphs) adapted to specific environmental conditions, but "ecospecies" is not a recognized unit of classification in biological taxonomy. 

Conclusion:

Therefore, the correct statement is According to competitive exclusion principle, two species cannot coexist in the same community if they have the same niche.

The correct answer is secondary succession.

Explanation:

• Secondary succession refers to the ecological succession that occurs in an area where a biological community has previously existed but was removed due to a disturbance.
• However, the statement that alien species experience secondary succession when introduced to a new ecosystem is incorrect.
• Alien species, when introduced to a new ecosystem, can exhibit various behaviors depending on multiple factors including their adaptability, the existing ecosystem's resilience, and interactions with native species.
• The most common outcomes include exponential growth due to lack of predators or competition, or they may struggle to adapt, potentially leading to extinction.
• Secondary succession is more about the recovery of an ecosystem after disturbance rather than the behavior of alien species in a new environment.
• Therefore, the solution statement provided is incorrect. The more accurate behavior of alien species when introduced to a new ecosystem would often be exponential growth if they successfully adapt and outcompete native species.

Overview of Incorrect Options:
Option 1: Extinction
While some introduced species do fail to establish and go extinct in a new ecosystem, this is not the universal or most characteristic outcome of alien species introduction. Many successfully adapt and thrive.
Option 2: Exponential Growth
This is often the correct outcome for invasive species that find a niche in a new ecosystem without natural predators or controls. They can grow exponentially, often to the detriment of native species and ecosystems.
Option 3: Secondary Succession
Incorrect as the primary concept of secondary succession does not directly apply to the behavior of alien species in new ecosystems. It is more about the ecosystem's recovery process rather than the introduction and adaptation of alien species.
Option 4: Character Displacement
Character displacement involves evolutionary changes in species traits due to resource competition. While this can occur when alien species are introduced, it is a longer-term process and not an immediate outcome of introduction.

In summary, the most common immediate outcome for alien species introduced to a new ecosystem, if they are successful, is exponential growth due to a lack of natural predators or checks and balances that would normally exist in their native habitat. This can lead to significant ecological impacts, including the decline or extinction of native species.

The correct answer is Option 2 i.e. A,C and B

Concept:

• For a variety of studies, including those on the global carbon and nutrient cycles and climate change, accurate estimations of aboveground biomass are crucial.
• Allometric equations or biomass estimate models (BEM), which relate biomass to more easily quantifiable properties like diameter at breast height, overall height, or crown dimensions, are frequently used to infer aboveground biomass.
• There is some reason for adapting BEMs created for one species to comparable ones because many species have fairly similar behaviors.
• It is common practice to further separate the biomass of trees into above- and below-ground components.
• For instance, the biomass that grows above ground consists of leaves, branches, stems, and bark. Researchers may have slightly varied definitions of components.

Explanation:

• Stemwood has the maximum biomass hence it matches curve A.
• Branches have a little more biomass than whole leaves of trees. because branches can be crooked, rotten, or broken. hence, it matches curve C
• The foliage has the least biomass among all hence it matches curve B.

Therefore, the correct answer is Option 2.

The correct answer is populations < communities < ecosystems < biomes

Explanation:

The correct order of increasing biological organization reflects how living organisms and their environments are grouped, from the smallest unit (populations) to the largest (biomes). 

• Populations: A population consists of individuals of the same species living in a specific area and capable of interbreeding. It represents the lowest level of organization in this context.
• Communities: A community consists of all the different populations of various species living and interacting in a particular area. Communities represent interactions among multiple species.
• Ecosystems: An ecosystem includes the biological community (living organisms) and the physical environment (non-living components like air, water, and soil) in which they interact. Ecosystems are broader than communities as they encompass both biotic (living) and abiotic (non-living) components.
• Biomes: A biome is a large-scale ecological area that contains multiple ecosystems with similar climatic conditions and characteristic communities of plants, animals, and other organisms. Examples include tropical rainforests, deserts, and tundras. Biomes represent the largest scale of biological organization in this list.:.

Conclusion: The correct order of increasing biological organization is: populations < communities < ecosystems < biomes.

The correct answer is A and D

Explanation:

Competition between two species can lead to various outcomes depending on how the species interact and utilize resources. Two possible results of species competition are niche differentiation and character displacement. Both of these phenomena help species to coexist by reducing direct competition over resources.

Analysis of the statements:

1. Niche differentiation between species: This is a common outcome of competition where species evolve to occupy different niches, minimizing competition. This is a possible outcome of species competition.
2. Expansion of fundamental niche of both species: This is less likely as fundamental niches are defined by the physical environment rather than competition. Competition typically limits or differentiates niches, rather than expanding them.
3. Expansion of realized niche of both species: This is also not a typical outcome of competition. Realized niches are usually smaller due to competition, and competition rarely leads to the expansion of the realized niche for both species.
4. Character displacement between species: This is an evolutionary outcome where differences in physical traits become more pronounced due to competition. It helps species to reduce competition by allowing them to exploit different resources. This is another valid outcome of species competition. 

• Character displacement is the term used to describe an evolutionary change that occurs when two similar species inhabit the same environment.
• Under such conditions, natural selection favors a divergence in the characteristics--morphology, ecology, behavior, or physiology--of the organisms.
• The best example of Character displacement is  in the Galapagos Islands, a group of coexisting finches have distinctly different body and beak sizes as well as beak shapes.
• Moreover, character displacement in traits associated with resource use (ecological character displacement) has been studied largely independently of that in traits associated with reproduction (reproductive character displacement).

Character displacement is indicated when the difference between species in mean trait value is greater after selection ( d _A ) than before selection ( d _B ). 

Key Points

• Niche differentiation and character displacement are likely outcomes of competition between species, allowing coexistence by reducing direct competition.
• Expansion of fundamental or realized niches is not commonly associated with competition between species.

The correct answer is Pontederia crassipes, Salvinia molesta, Alternanthera philoxeroides.

Explanation:

The plants listed below are major non-native invasive species of aquatic ecosystems in India:

The correct answer is Community Q has higher species diversity than P.

Concept:

• Species diversity refers to the variety and abundance of different species present in a particular ecological community, ecosystem, or geographical area.
• It is a measure of the richness and evenness of species within that region.

Species Richness-

• Species richness refers to the total number of different species present in a specific area or community.
• It is a simple count of the different species and does not consider the abundance of each species.

Species Evenness-

• Species evenness measures the relative abundance of different species within a community.
• It indicates how evenly individuals are distributed among the various species
• High species evenness contributes to a more stable and species diverse ecosystem.

Explanation:

• In the given table, community Q has high species diversity because species evenness is maintained continuously.
• But in community P some species are present in very high number whereas some species are present in very low number, so species evenness is not continuously maintained.
• That's why the species diversity of community Q is higher than P.

Hence, the correct answer is option 2.

The correct answer is Q, R, P

Concept: 

• Species diversity is defined as the number of different species and their relative abundance in a region/area. 
• Species diversity consists of two factors: 

1. Species richness -  It is the total number of different species present in a given region. 
   • The region that has a greater number of species will have high species diversity. 
   • For example, tropical rainforests have more species as compared to the tundra region. So, tropical rainforest will have greater species diversity.
2. Species evenness - it is the relative abundance of all the species present in the region. 
   • A region where all the species have the similar abundance will have the greatest species diversity.

• So species diversity is dependent on both factors, hence, a region having the greatest species richness as well as have highest species evenness will have greater species diversity.

Explanation:

• Habitat P has only 4 species as compared to 8 species in habitats Q and R. Also, species are not evenly distributed.  So, habitat P has the lowest species diversity. 
• Habitat Q and R have the same number of species i.e., 8. So, both habitats have the same species richness.
• Now, there is a greater difference in the abundance ( total number of individuals of each species) in habitat R. so, habitat R has low species evenness.
• On the other hand, habitat Q does not display variability in the number of individuals in different species. ie., there are either 15 or 20 individuals in all species, so, it has greater species eveness.
• Since species diversity depends on species richness and species evenness, So, Habitat Q has the greatest species diversity. 
• Since we have to arrange the habitat in the decreasing order of diversity, the correct order is Habitat Q (highest species diversity)  > Habitat R > Habitat P (lowest species diversity). 

Hence, the correct answer is option 4.

The correct answer is "Offspring do not require elaborate parental care"

Explanation-

Monogamy in birds often evolves when there is a need for parental care, and both parents contribute to raising offspring. If offspring do not require elaborate parental care, there may be less pressure for both parents to stay together.

Option 1- "Poor quality of habitat wherein resources are hard to find":

• Monogamy is advantageous in this scenario because maintaining a territory with necessary resources for breeding and offspring-raising can be challenging. Two parents can better secure and defend resources against intruders.

Option 2 -"Males guard females after mating with them":

• In this case, monogamy is beneficial because it ensures that a male's effort is devoted to his own offspring. By guarding the female, the male prevents other males from mating with her, thereby ensuring paternal certainty.

Option 3-"Mates are scattered and hard to find":

• In species where finding mates takes considerable time and energy, monogamy can be beneficial because it reduces the energy spent on seeking out numerous partners.

Additional Information Monogamy and polygamy are two types of mating systems commonly found among animals. These systems tend to evolve based on what is most conducive for reproductive success in a given environment.

1. Monogamy:

• Monogamy, when an individual mates with only one partner over a defined period, is relatively rare in the animal kingdom but is more common in birds. This can either be serial (having a new partner every breeding season) or lifelong (staying with the same partner for life).
• Example of monogamy in animals is penguins. Emperor penguins, for instance, form monogamous pairs for each breeding season. Both partners share the incubation duties and care for their single offspring.
• Gibbons (primates), swans, albatrosses, and bald eagles also often form lifelong monogamous relationships.

2. Polygamy:- Polygamy, when an individual mates with multiple partners, is the most common mating system among animals. This can take on a few different forms:-

• Polygyny is when one male mates with multiple females. This is the most common form of polygamy. Many deer species like red deer are polygynous, with males (stags) establishing small harems of females (hinds) during the breeding season.
• Polyandry is when one female mates with multiple males. This is much rarer. An example is the jacana, a tropical bird species. In this case, females are larger and more brightly colored than males. The female mates with multiple males, and the males incubate the eggs and raise the chicks.
• Polygynandry is when multiple males mate with multiple females. One example is the bonobo, a species of primate, in which both males and females have multiple sexual partners, and sexual interactions play a key role in the social dynamics of the group.

Monogamy can increase survival for offspring that need care from both parents, but it may limit the number of offspring one could potentially have. Polygamy can increase the number of offspring but can also increase competition and aggression, especially among males.

Concept:

• Quantifying ecological resemblances between samples, including similarities and dissimilarities (or distances), is the basic approach of handling multivariate ecological data.
• Two samples, which contain the same species with the same abundances, have the highest similarity (and lowest dissimilarity or distance); the similarity decreases (and dissimilarity/distance increases) with the differences in their species composition.
• All cluster and ordination methods operate with similarities or distances between samples.

Explanation:

• Jaccard similarity index divides the number of species shared by both samples (fraction a) by the sum of all species occurring in both samples (a+b+c, where b and c are numbers of species occurring only in the first and only in the second sample, respectively).

Jaccard similarity: C_J={a}/{a+b+c}

here, a= 2, b=c=1 so, 2/2+1+1 =2/4= 0.5

• The simple matching coefficient (SMC) or Rand similarity coefficient is a statistic used for comparing the similarity and diversity of sample sets.
• Given two objects, A and B, each with n binary attributes, SMC is defined as: where: is the total number of attributes where A and B both have a value of 0.

SMC= number of matching attributes/sum of all attributes

here we have SMC= 3/3+1+1= 3/5= 0.6

Hence option 4 is correct

The correct answer is (B) and (C)

Concept:

• The transfer of  energy from producers through a series of organisms (herbivores to carnivores to decomposers) with repeated eating and being eaten is known as food chain.
• Various food chains are interconnected and maintain an equilibrium, thus no species become dominant. 
• Nature has been created in way to maintain balance between feeders and producers.

Explanation:

Statement A: Herbivore insects are inefficient feeders

• Animals classified as herbivores get their nutrition from plants and plant derivatives.
• The green plants managed to persist despite 25–30% of bug species, the largest animal group on earth, being herbivorous.
• Thus, this statement is not true

Statement B:   Herbivore insect densities are kept low by predators

• Insect herbivores frequently interact indirectly through interactions mediated by both plant and predators.
• An insect herbivore may also negatively impact another herbivore by altering the abundance or behavior of a shared predator.
• In both cases, an herbivore may provide a net benefit to the plant they consume if that herbivore indirectly suppresses the abundance of a more damaging herbivore.
• Thus, this statement is true

​​Statement C:  Plants secrete herbivore-deterrent chemicals

• Structural traits such as spines and thorns (spinescence), trichomes (pubescence), toughened or hardened leaves (sclerophylly), incorporation of granular minerals into plant tissues, and divaricated branching (shoots with wiry stems produced at wide axillary angles) play a leading role in plant protection against herbivory.
•  Sclerophylly refers to the hardened leaves, and plays an active role in plant defense against herbivores by reducing the palatability and digestibility of the tissues, thereby, reducing the herbivore damage.
• Thus, this statement is not true.

The correct answer is Option 4 i.e. A - iii, B - ii, C - iv, D - i

Explanation-

A.Charles Elton: iii - the pyramid structure of feeding relationships in ecosystems.

• Charles Elton was one of the pioneers of ecology who developed the concept of food webs and emphasized the pyramid structure of feeding relationships in ecosystems. He described how the pyramid's shape and structure reflect the underlying trophic interactions and nutrient flows.

B. A G Tansley: This scientist can be connected to concept ii - the term ecosystem.

• Arthur Tansley was a British ecologist, who is widely credited with introducing the term "ecosystem" in the 1930s. His work led to the recognition of the complex interrelationships among organisms and their environment, essentially viewing the whole system as an integrated unit.

C. A J Lotka: iv - a thermodynamic view of the ecosystem.

• Alfred J. Lotka was a biophysicist and mathematician who developed what is known as the Lotka-Volterra equations for the study of populations. He approached the ecosystem as a thermodynamic system emphasizing the flow of energy, which often referred to as energetic or thermodynamic view of the ecosystem.

D. Raymond Lindeman: i - trophic dynamics.

• Raymond Lindeman was an American ecologist, best known for his seminal work on understanding trophic dynamics i.e., the transfer of energy from one part of an ecosystem to another. He established the concept that energy flows through an ecosystem in one direction, in a "food chain" or "food web".