Test: Organisms & Populations - 2 - NEET MCQ

Living organisms present in an ecosystemforms biotic components. It includes all plants, animals and microbes. The biotic components share and compete for resources present in particular ecosystem.

Mycorrhiza is a mutualistic interaction between fungi and plants. About 80-90 percent of plants rely on mycorrhiza for the uptake of minerals (nitrogen, phosphorous, etc.) from the soil. While plants supply essential nutrients such as sugars to fungi for their proper growth.

The factors which is responsible for wide variety of habitats within each biome includes local and regional variations of temperature, soil type, water availability etc.

Hypersaline lagoons have very high concentration of salt (>100). Some organisms can survive in wide range of salinity. These organisms are calledeuryhaline species.

Xerophytes are plants that grows in deserts having very less water. Sunken stomata, leaves reduced into spines and CAM photosysnthesis are the characteristicfeatures of these plants. Cuticle is present on leaves to prevent loss of water.

Biotic potential can be decribed as natural capacity of organisms in an ecosystem to reproduce. Biotic potential depends upon availability of food, water and numberof organisms in reproductive age group.

The phrase “sharing of food” or “sharing of the table” describes commensalism. It is a long-term relationship between two species in which one species derives the benefit while other is neither harmed nor benefited.

Vultures will not be considered as predator. Vultures feed on dead animals on the other hand predators kill or harms the prey for obtaining food.

The stationary phase is absent in exponential growth. Exponential growth is observed when resources in the population are unlimited. The population grows in geometric fashion and results in a J-shaped curve.

The body temperature of any homeotherm falls or rises suddenly it would become ill due to change in homeostasis of individual. At higher temperature enzymatic activity get altered that change the physiological activities of organisms.

Age groups among human population includes reproductive, pre-reprouctive and post reproductive growth. It do not includes embryonic phase growth.

E In competition, superior competitor eliminates the inferior one. This statement is called Gause’s competitive exclusion principle. Two closely related competing for same resources cannot co-exist indefinitely and inferior will be eliminated.

The given figure is of sigmoidal growth. It is a logistic/ S-shaped growth curve. It is obtained due to the finite and limited source of resources in a population.

Biological control method adopted in agricultural pest control are based on the ability of predator to regulate prey population.

Mediterranean orchid Ophrys ensures pollination by co-evolution, sexual deceit and pseudo-copulation. One petal of flower bears an uncanny resemblance to female of bee in size, colour and markings.

Verhulst-Pearl logistic model of growth is more realistic growth model in comparison to exponential model of growth. Population growing in a habitat having limited resources shows sigmoid curve like growth before reaching to carrying capacity.

Species facing completion might evolve mechanism that promotes co-existence rather than exclusion that mechanism is called resource partitioning. In which they avoid completion by choosing different times of feeding or different foraging patterns.

The organisms move away temporally from stressful habitat to more suitable habitat is called migration. Migration adaptation is a behavioral attribute.

Polygamous population is often directly related to number of females in the population. Polygamy means having more than one female partner with single male that can reproduce.

Natality or birth rate is the number of birth in a given period in the population that are added to initial population. Actual birth rate under environmental condition is much less than total birth because all organisms do not survive adulthood due ot predation, completion etc.

The group of individuals living in as defined geographical area share or compete for similar resources and potentially interbreed forms a population. Interbreeding means sexually reproducing organisms but asexually reproducing organisms also form population ecologically.

Age pyramid of expanding population is broader at base and thin upwards. Number of individuals in pre-reproductive age is more than post reproductive age. Population size is technically called as population density.

Negative interactions includes completion, predation, parasitism and amensalism. Pencillin and Streptomycin prohibits the growth of micorbes or kills the microbes that is a kind of negative interactions.

The interaction between two species in which both are benefited is called mutualism. Anabaena and Azolla help each other in obtaining food. Anabaena is a nitrogen fixing algae.

It indicates a stationary phase. The population achieves zero growth in the stationary phase. It is the last phase of logistic growth. It is due to many reasons such as exhaustion of resources, aging, etc.