Organisms and Populations MCQ Quiz - Objective Question with Answer for Organisms and Populations - Download Free PDF

The correct answer is \(\dfrac{dN}{dt} = rN\left(\dfrac{K-N}{K}\right)\)dN/dt=rN(K−N)K" id="MathJax-Element-10-Frame" role="presentation" style=" position: relative;" tabindex="0">dN/dt=rN(K−N)K" id="MathJax-Element-23-Frame" role="presentation" style=" position: relative;" tabindex="0">dN/dt=rN(K−N)KdN/dt=rN(K−N)K" id="MathJax-Element-21-Frame" role="presentation" style="position: relative;" tabindex="0">[Math Processing Error]dN/dt=rN(K−N)K" id="MathJax-Element-55-Frame" role="presentation" style=" position: relative;" tabindex="0">dN/dt=rN(K−N)KdN/dt=rN(K−N)K" id="MathJax-Element-77-Frame" role="presentation" style=" position: relative;" tabindex="0">dN/dt=rN(K−N)KdN/dt=rN(K−N)K" id="MathJax-Element-2-Frame" role="presentation" style="position: relative;" tabindex="0">dN/dt=rN(K−N)KdN/dt=rN(K−N)K dN/dt=rN(K−N)K

Explanation:

Verhulst-Pearl logistic growth, also simply known as logistic growth, is a model of population growth that describes how a population grows more slowly as it approaches its carrying capacity. 

A population growing in a habitat with limited resources show initially a lag phase, followed by phases of acceleration and deceleration and finally an asymptote, when the population density reaches the carrying capacity.

A plot of N in relation to time (t) results in a sigmoid curve. This type of population growth is called Verhulst-Pearl Logistic Growth.

• Ideally if the resources in a habitat are unlimited, the population shows exponential growth pattern.
• But resources are not available to any species population in unlimited amount. Thus, the species compete for the available resources to survive.
• This competition for the limited resources restricts the exponential or unlimited growth of any population.
• Any given habitat can only provide resources to support a maximum possible number, beyond which it further growth of population is not possible. This is known as the carrying capacity (K) for a particular species in a habitat.

Logistic growth is represented as: \({dN \over dt} = rN({K-N\over K})\)

where,

• N = Population Density at time t
• K = Carrying Capacity,
• \(r \) = Intrinsic rate of natural increase
• \(dN \over dt\) = Rate of change of population density.
• 'r' value denotes the difference between the per capita birth and death (b-d).
• The environmental resistance is represented in the equation as \(({K-N\over K})\).

The correct answer is Both Statement I and Statement II are incorrect 

Concept:

• Fig trees (genus Ficus) and fig wasps exhibit a fascinating mutualistic relationship that has evolved over millions of years. This relationship is a classic example of co-evolution.
• The fig fruit is technically a syconium, which is an enclosed structure containing numerous tiny flowers inside. Fig wasps play a crucial role in pollinating these flowers.
• Fig wasps enter the syconium to lay their eggs, and in the process, they help pollinate the fig flowers. The fig tree provides a habitat for the wasps to complete their life cycle, while the wasps ensure the tree's reproduction through pollination.
• The presence of wasp remnants inside the fig fruit does not make it non-vegetarian, as the remnants are naturally decomposed and absorbed into the fruit during its development.

Explanation:

Statement I: "Fig fruit is a non-vegetarian fruit as it has enclosed fig wasps in it" is incorrect because:

• Fig fruits are considered vegetarian as they are plant-based, and any wasp remnants are naturally decomposed during fruit development.
• The presence of wasps is part of a natural ecological process and does not change the classification of the fruit as vegetarian.

Statement II: "Fig wasp and fig tree exhibit a mutual relationship as fig wasp completes its life cycle in fig fruit and fig fruit gets pollinated by fig wasp" is incorrect because:

• A part of the life cycle of the wasp is completed in fig fruit. (not complete)
• Fig wasps lay their eggs inside the fig fruit, and their larvae develop there.
• Fig species can be pollinated only by its ‘partner’ wasp species and no other species.
• The female wasp uses the fruit not only as an oviposition (egg-laying) site but uses the developing seeds within the fruit for nourishing its larvae.
• The wasp pollinates the fig inflorescence while searching for suitable egg-laying sites.
• In return for the favour of pollination, the fig offers the wasp some of its developing seeds, as food for the developing wasp larvae.

The correct answer is Commensalism

Concept:

• Commensalism is a type of ecological interaction where one species benefits, and the other species neither benefits nor is harmed.
• In this interaction, the species that benefits is referred to as the "commensal," while the unaffected species is the "host."
• Epiphytes are plants that grow on other plants (such as trees) for physical support but do not extract nutrients or cause harm to the host plant.
• In the given example, epiphytes growing on a mango branch represent commensalism because the epiphytes benefit from the support provided by the mango tree, while the mango tree remains unaffected.
• Barnacles growing on a whale; the barnacles get a place to live and access to food, while the whale is unaffected is another example of Commensalism.

Table: Popular Interactions

Note:

• '+' : Beneficial
• '-' : Detrimental (Harmful)
• '0' : Neutral (Neither benefitted nor harmed)

Explanation of Other Options:

• Mutualism:
  • In mutualism, both species involved in the interaction benefit from each other.
  • For example, pollination is a mutualistic relationship where bees collect nectar (food) from flowers and, in return, help the plant with pollination.
• Predation:
  • Predation involves one species (the predator) hunting, killing, and consuming another species (the prey).
  • For instance, a lion hunting a deer is an example of predation.
• Amensalism:
  • Amensalism is an interaction where one species is harmed, and the other species remains unaffected.
  • For example, the secretion of chemicals by certain fungi that inhibit the growth of nearby plants is an example of amensalism.

The correct answer is a, c

Concept:

• Ectoparasites: Ectoparasites live on the outside of the host's body. They depend on the host for sustenance but do not enter the internal tissues of their host. Common examples include lice and ticks.
• Endoparasites: Endoparasites live inside the host's body, either within cells, tissues, or organs. Examples include the malarial parasite (Plasmodium) and the human liver fluke (Fasciola hepatica).

Explanation:

• a) Lice on humans: This is correct because lice are ectoparasites that live on the surface of the human body, particularly in the hair.
• b) Malarial parasite in humans: This is incorrect because the malarial parasite (Plasmodium spp.) is an endoparasite that lives inside human red blood cells.
• c) Ticks on dogs: This is correct because ticks are ectoparasites that attach to the skin of dogs and other animals to feed on their blood.
• d) Human liver fluke: This is incorrect because the human liver fluke (Fasciola hepatica) is an endoparasite that lives in the bile ducts of the liver.

The correct answer is Competition

Explanation:

Competitive release occurs when a species, whose distribution is restricted to a small geographical area due to the presence of a competitively superior species, expands its range of distribution dramatically upon removal of the competing superior species. Example are The barnacle Balanus dominates the rocky intertidal regions of Scotland, and excludes the barnacle Chathamalus from that zone.

Concept:

• A population at any given point of time comprises of individuals of different age groups.
• The percentage of individuals of a given age or age group is known as age distribution, which is an important population attribute.
• Age pyramid is a structure that results from the plotting of the age distribution of a population.
• For a human population, 3 age groups are considered:
  • Pre-reproductive
  • Reproductive
  • Post-reproductive
• The pre-reproductive age group occupies the lowermost layer of the pyramid.
• Thus, a narrow base would indicate low number of young individuals.

Important Points

• The age pyramids usually include both male and female individuals.
• The shape of the pyramid shows the growth status of a population.
• They can be of 3 basic types:
  • Expanding - Pre-reproductive group is maximum and post-reproductive group is minimum.
  • Stable - The pre-reproductive and reproductive groups are almost equal, while the post-reproductive is less.
  • Declining - Pre-reproductive group is lesser than the other age groups.

Hence, the given diagram denotes stable population.

The correct answer is Commensalism.

• Commensalism is a type of biological interaction in which one species gets benefitted while the other species neither benefit nor are harmed.
  • The species that gains the benefit is termed as commensal and the other species is termed as the host species.
  • It this interaction, the commensal feeds on the substances captured or ingested by the host species.
  • The two partners in this biological interaction can survive independently.
  • The interaction between the sea anemone that has stinging tentacles and the clownfish that lives among them is an example of Commensalism. 

Additional Information

• Mutualism
  • Mutualism is defined as an interaction between individuals of different species that results in positive (beneficial) effects on per capita reproduction and/or survival of the interacting populations.
• Amensalism
  • In amensalism, one species is harmed whereas the other is unaffected.
  • Predation, parasitism and commensalism share a common characteristic– the interacting species live closely together.
• Parasitism
  • Parasitism is a symbiosis in which one organism, the parasite, causes harm to another, the host, which the parasite utilizes as habitat and depends on for resource acquisition.

The correct answer is 1951 - 1981.Key Points

• The period of population explosion in India is referred to as 1951-1981.
• During this period, India's population grew at an unprecedented rate, increasing from around 361 million in 1951 to over 846 million in 1981.
• This period was marked by several factors, including improvements in healthcare and sanitation, increased agricultural productivity, and a decline in infant mortality rates.
• The population explosion had several social and economic consequences, including increased pressure on resources, urbanization, and poverty.

Additional Information

• 1901-1921 was a period of relatively slow population growth in India, with the population increasing from around 238 million to 251 million.
• 1921-1951 was a period of moderate population growth, with the population increasing from around 251 million to 361 million.

The correct answer is increase.Key Points

• If the birth rate of a country is more than the death rate, then the population will increase as more people are being born than dying.
• This is known as population growth and can have both positive and negative effects on a country.

Additional Information

• If the population grows too quickly, it can put a strain on resources such as food, water, and housing. 
• However, if the population growth is managed properly, it can lead to economic growth and development.
• The population will not remain constant if the birth rate is higher than the death rate.

Key Points

• Skin is the outermost covering of the body.
• The human skin is made up of multiple layers of ectodermal tissue that protects the underlying organs, muscles, and ligaments from injuries.
• Skin is composed of stratified squamous epithelium tissue.
• It provides insulation, temperature regulation, and sensation to the body.
• It acts as a physical barrier that prevents the entry of microorganisms.
• The skin has a variety of nerve endings that react to heat and cold, touch, pressure, vibration, etc.
• The skin contains hair on its surface.
• These hairs on the skin help to maintain body temperature.

Explanation:

• The hairs on the skin are erect when the temperature falls because the thickened fur coat act as an insulator.
• When the temperature lowers, the erector muscles of the hair contract, thus raising hairs.
• The hairs can trap a thicker layer of air above the skin.
• The trapped air insulates the skin against heat loss.

Hence, the correct answer is option (1).

Concept:

• An ecosystem refers to a geographical area where both the biotic and abiotic factors work together to maintain the equilibrium of life.
• The biotic factors include plants, animals, and microorganisms whereas abiotic factors include weather, landscapes, etc.
• The organisms living in an ecosystem interact with each other too.
• Vital processes like growth, survival, nutrition and reproduction are depended on these interactions.
• The major interactions seen among the organisms in an ecosystem are - Predation, Parasitism, Commensalism, Mutualism, and Competition.

Explanation:

Ectoparasitism - 

• ​Parasitism is an ecological interaction involving two organisms where one is benefitted while the other is harmed.
• It is a (+/-) kind of interaction.
• It is a relationship between one organism called a parasite that obtains its food from another organism called the host. 
• The parasite may live on or in the body of the host.
• Ectoparasitism is a type of parasitism where the parasite lives on the surface of its host.
• E.g.: Blood sucking lice or fleas on animals like dogs.

Brood parasitism - 

• Brood parasitism is a type of parasitism seen in birds.
• In this type of parasitism, the parasite bird lays its egg in the nest of the host bird.
• The host bird incubates the eggs for the parasite bird.
• The parasite bird can do this because, over the course of evolution, its eggs have evolved to resemble in size and color that of the host bird's eggs.
• This in turn reduces the chances of the parasite bird's eggs being detected and ejected from the nest by the host bird.
• A classic example of brood parasitism is a cuckoo (parasite bird) laying eggs in a crow's nest (host bird).

Commensalism - 

• In commensalism, one of the two organisms involved in the interaction benefits. The other organism involved neither benefits nor is harmed by this interaction.
• It is a (+/0) kind of interaction.
• It takes place between organisms belonging to two different species.
• E.g.: Suckerfish that attaches itself to the under-surface of shark.

Mutualism - 

• ​Mutualism is a type of ecological interaction wherein both the organisms involved are benefitted from the interaction.
• It is a (+/+) kind of interaction.
• Neither of the two organisms involved in this interaction can survive separately.
• E.g: Lichen is an example of mutualism. The lichen body is made up of a matrix formed by a fungus. Within the cells, algae are embedded.

Hence, the correct answer is option 2 (Brood parasitism).

Concept:

• Soil plays a critical role in plant growth.
• Soil provides necessary nutrients to plants.
• Apart from nutrients, oxygen and water is also provided to a plant root through the soil it grows in.
• Soil provides anchorage to plant roots, helping the plant to grow vertically with stability.
• Following are some of the types of soils in which different plants grow:
  • Sandy soil
  • Peaty soil
  • Silty soil
  • Clay soil
  • Saline soil

Important Points

• Lithophytes - 
  • ​These are the plants that grow on or in the crevices of rocks.
  • They can be of two types:
  1. Epilithic i.e. grow on the surface of the rock.
  2. Endolithic i.e. grow in the crevices of the rock.
  • E.g.: Species of ferns like Rock Felt Fern, orchids like Paphiopedilum, etc.
• Psammophytes - 
  • Psammophytes are plants that require sandy soil to thrive.
  • These are generally found in deserts.
  • Most of the psammophytes are xerophytes with reduced or no leaves at all.
  • Some species of Psammophytes are also found in sands along seas, large lakes, or rivers.
  • E.g.: Haloxylon, Aristida, etc.
• Oxylophytes - 
  • ​Oxylophytes are plants that grow in acidic soils.
  • Owing to the soil's dryness due to high acidity, these plants have developed xeromorphism.
  • E.g.: Bog mosses, Cotton grass, etc.
• Halophytes - 
  • ​Halophytes are plants that have a natural ability to withstand salinity.
  • These plants are found in areas with high salinity such as marshes, seashores, saline semi-deserts, etc.
  • These plants are often used as model plants to study stress tolerance in plants.
  • E.g.: Salicornia, Spergularia marina, etc.

Hence, the correct answer is option 2.

Important Points

• Interaction refers to the associations between species that favor or inhibit mutual growth and evolution of populations.
• The interactions may take the form of competition, predation, parasitism, commensalism or mutualism.
• Based of their effects, the interspecific interactions can be of 3 types:
  • Beneficial - These are positive interactions where either one or both of the species are benefitted.
  • Detrimental - These are the negative interactions where one or both of the species are harmed.
  • Neutral - These are interactions where the species is not affected.

Explanation:

Scavenging - 

• It is a type of interaction where organism eats dead or rotting biomass, such as animal flesh or plant material.
• Here the scavenging organism is always benefitted and no other organism is harmed.
• Therefore, it is a positive type of interaction.

Additional Information

• Amensalism - 
  • ​It is the type of interaction in which one of the organism is harmed and the other organism is neither harmed nor benefitted.
  • It is a negative type of interaction air, food, shelter, water, and space.
• Competition - ​
  • The interaction of individuals for a common resource that is in limited supply, 
  • Organisms compete for the resources like air, food, shelter, water, and space that they need to survive, grow, and reproduce.
  • The stronger organisms survive and the others die.
  • Therefore, it is a negative type of interaction.
• Predation - 
  • Predation is a biological interaction where one organism, the predator hunt and kill other organisms i.e. it's prey for food. 
  • Therefore, it is a negative type of interaction.

• Population size keeps changing with time due to a number of factors.
• The basic factors that contribute towards the fluctuations in population density are:
  • Natality (B) 
  • - is the number of births in the given population for a given period of time.
  • Mortality (D) - is the number of deaths in the given population during a given period of time.
  • Immigration (I) - is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration.
  • Emigration (E) - is the number of individuals of a population leaving the habitat for another during the time period under consideration.

We can express the relation between these factors in the following equation:

N_t+1 = N_t + [ (B + I) - (D + E) ]

where, N = Population density

Corrected Table:

Hence, the correct answer is option 1. 

Key Points

• The population consists of all the organisms of a particular species that can interbreed and live in the same place at the same time.
• The two important measures of a population are population size and population density, i.e. the number of individuals per unit area or volume.
• Populations can change in their numbers and structure, due to the natality and mortality of species.
• In population ecology, natality is defined as for a given population, the ratio of the number of births to the size of that population.
• It shows an increasing effect on the population density because it results in the addition of the number of individuals to a population.
• Mortality is the death rate of a population which can be calculated on the basis of the deaths in a particular region.
• It decreases the population density as it subtracts the number of individuals from a population.
• The difference between the natality and mortality rate gives the value for the intrinsic rate of natural increase in a population.

Explanation:

• The percentage ratio of natality over mortality that determines the growth of a population is known as the vital index.
• The vital index can be expressed as (Natality / Mortality) x 100.
• These are used in measuring population density.

Additional Information

• The ratio of males to females in a population is termed as sex ratio.
• Population density is the number of individuals per unit area or volume of a particular population.
• Age structure refers to the proportions of individuals at different life stages of a particular population.

Hence, the correct answer is option (3).