Organisms and Populations Test - 12

• A predator is an organism that hunts, catches, kills, and eats other animals.
• Parasitism is a type of symbiosis where one organism (the parasite) benefits and the other (the host) is harmed. 
• A host is an organism that harbors a parasite, or a mutual or commensal symbiont, providing nourishment and shelter. 
• Amensalism is an association between organisms of two different species in which one is inhibited or destroyed and the other is unaffected.
• So, the correct answer is option D.

• r-selected species are the ones that are found in the sparsely crowded ecological niche to exploit it and aim at the production of a large number of small-sized progeny with lower survival rates due to the short gestation period and early attainment of maturity.
•  k-selected species are characterized by exponential growth in population size till carrying capacity of the niche only. These species produce a small number of large-sized progeny and have longer gestation periods to allow proper embryological development.

The two populations A and B are herbivores which are competing for the same food. Population A decreased as it was not well adapted as population B. Population B was able to strive for the available food.

Commensalism refers to relationship wherein one organism is benefitted while other remains unaffected and is denoted by + 0. 

Natality is the rate of production of new individuals per unit area of population per unit time. Simply it is called birth rate. So, the correct answer is option 4.

One of the best-known examples of commensalism is that between the hermit crab and a sea anemone (e.g., Adamsia). The anemone is often found attached to the shell in which the hermit crab lives. A sea anemone attaches itself to the crabs shelter and it may envelop part of the crab's shell as well. The growth of the crab and anemone keep pace with each other and the crab has no need to change its shell more and more of its is sheltered by the anemone. As the crab moves about in search of food the anemone is brought into contact with a greater supply of food and the crab is protected by the anemone's stinging cells.

Gause grew populations of Paramecium aurelia and the larger P. caudatum, in controlled conditions. When these two populations were grown in separate test tubes, the population of each species quickly increased to the carrying capacity. When grown together, determined by available conditions, one species thrived over other. It led to the principle of competitive exclusion that two competing species can not coexist and in time one or the other would eventually out-compete. 

• In ecology, the competitive exclusion principle, sometimes referred to as Gause's law of competitive exclusion or just Gause's law is a proposition that states that two species competing for the same resource cannot coexist at constant population values if other ecological factors remain constant. 
• When two competing life forms attempt to occupy the same niche, only one outcome is possible: One life form will drive out the other.
• So, the correct answer is option C.

• Mutualism (Symbiosis) is a relationship, in which both the interacting organisms/partners are benefited from each other. 
• Predation is the consumption of one species (the prey) by another (the predator). 
• Parasitism is a host-parasite relationship in which one (parasite) is benefited while the other (host) is adversely affected, although not necessarily killed.
• Competition is the injurious effect of one organism on another because of the removal of some resource of the environment. This phenomenon can result in major fluctuations in the composition of the microbial population in the soil.