Organisms and Populations Test - 80

• Predation is the form of interaction in which the predator is benefitted (+) while the prey is harmed (-).
  
• In parasitism, the parasite is benefitted (+) as it gets food from the host, and the host is definitely harmed (-). 
• The host is devoid of nutrition and may contract some disease.
• That means both predation and parasitism are interactions where one partner is benefitted while the other is harmed, i.e. (+,-).

Correct Option: B

Explanation:

• When there is no environmental opposition, or when resources are limitless, exponential expansion is seen.
• Because resources are limited in the natural world, population growth is constrained by environmental constraints and follows a logistic growth pattern.
• Biotic potential refers to a population's capacity to grow given perfect environmental conditions, such as enough food, no predators, and no illness, or when there is no environmental resistance.
• The major defining elements of an organism's biotic potential are its rate of reproduction and the size of each litter.

Cuscuta is a genus which includes nearly 100–170 species of yellow, orange, or red parasitic plants found in the temperate and tropical regions. Eichhornia or water hyacinth belongs to the genus of aquatic flowering plants develops root pocket to float freely in water.
Monotropa is a genus with 5 species of herbaceous perennial plants which are saprophytes.Rhizophora belongs to the genus of tropical mangrove trees with adaptations, such as pneumatophores.Utricularia or bladderworts is a genus of insectivorous plants with nearly 233 species. Thus, the correct answer is option D.

Mutualism is a relationship in which both the organisms are benefited by one another. Hence, there is plus and plus for both the species.

Predation, parasitism, competition and various other factors impart a cumulative effect on population size. It is never deterimined by any of above mentioned single factor. Rather any drastic change or natural calamity such as drought, femine, and flood can alone reduce the population size making option E correct answer.

Closure of stomata throughout the night does not impart any adaptation to dry climate because plant loose water through stomata in the day when the rate of transpiration is much higher due to the higher temperature. Photorespiration reduces the efficiency of RUBISCO and poses a demand of keeping stomata open for longer time to carry out photosynthesis. The opening of stomata for longer duration cause loss of water through transpiration. Spatial separation of carbon dioxide fixation and RUBISCO activity in mesophyll and bundle sheath cells of $$C_4$$ plants respectively avoids photorespiration by concentrating $$CO_2$$ in bundle sheath cells to scale down the oxygenase activity of RUBISCO and increase the RUBISCO efficiency. The increased RUBISCO efficiency allows higher rates of photosynthesis even when stomata are closed for longer time as well as reduces photorespiration and water loss. CAM plants reduce water loss by opening the stomata at night only. Thus, the correct answer is option A. 

Many species are brood parasites as they lay their eggs in the nests of other species, but the majority of species raise their own young. An example of brood parasite is female European Cuckoos lay their eggs only in the nests of other species of birds. A cuckoo egg usually closely mimics the eggs of the host (one of whose eggs is often removed by the cuckoo). The host may recognize the intruding egg and abandon the nest, or it may incubate and hatch the cuckoo egg. Shortly after hatching, the young European Cuckoo, using a scoop-like depression on its back, instinctively shoved over the edge of the nest any solid object that it contacts. With the disappearance of their eggs and rightful young, the foster parents are free to devote all of their care to the young cuckoo. Frequently this is an awesome task, since the cuckoo chick often grows much larger than the host adults long before it can care for itself.

Mutualism refers to the association which is benefited to both the partners. Parasitism is the relationship where one organism is benefited at the expense of other. Commensalism refers to the relationship wherein one organism is benefited while other remain unaffected. Symbiosis is the close association between two organisms of different species wherein one or both partners are benefited. Predation refers to the act of feeding on other animals. Thus, the correct answer is option B.