NEET Practice Questions (MCQs) with Answers & Solutions

(d) Competition is a type of negative interaction which develops between two or more organisms using the same resource, if the resources are insufficient to fulfill their demands. The competition within the members of same species is termed as intraspecific competition while the competition between two species is termed as interspecific competition. Competition increases with population density. 

(b): Thermal stratification in the water column is an important physical feature in many temperate and tropical lakes. This vertical stratification, which results from density changes with temperature, has a strong influence on the rates of biological and chemical processes in lakes. Thermally induced density stratification begins in the spring after the ice cover breaks up and the lake has mixed (spring overturn) and persists through summer in moderately deep lakes in the temperature zone (e.g., southern Ontario). During the period when strong vertical stratification occurs, the upper layer of the water column (epilimnion) is warmed by the sun while the lower layer (hypolimnion) remains cool and heavy. The middle layer (metalimnion) is characterized by a temperature gradient (um thermocline). During the autumn, winds and temperature gradually erode this thermal stratification until mixing of the water column (fall overturn) occurs.

(a) Isoconformers/osmoconformers are those animals that do not actively control the osmotic condition of their body fluids. They show changes in the concentration of the body fluids according to the concentration of surrounding medium.

Examples : All marine invertebrates, some fresh water invertebrates and a single vertebrates, hagfish (a marine cyclostome).

(d) Biosphere is biologically inhabited part of Earth along with its abiotic or physicochemical components. Biosphere consists of three interacting subdivisions - atmosphere, lithosphere and hydrosphere. Atmosphere is the transparent gaseous mantle surrounding the Earth. Lithosphere is the outer solid crust of Earth. Hydrosphere is liquid mantle of Earth.

(c) Mutualism is an obligatory positive interspecific interaction stongly beneficial to both species. The unicellular photosynthetic algae, called Zoochlorellae live symbiotically in the outer tissues of coelenterates. Algae are photosynthetic and produce oxygen and food beneficial to hosts and in exchange they obtain materials like carbon dioxide and nitrogenous wastes released by metabolism of host animals.  

(a) World population day - 11th July

No tobacco day - 31st May

World environment day - 5th June

World health day - 7th April

(c) The Great Barrier Reef - the largest system of coral reefs in the world is more than 2000 km in length and comprises 2900 separate reefs and 940 islands. Its high species diversity includes more than 400 species of coral, 400 species of molluscs, 1500 species of fish, 6 species of turtles, 35 species of seabirds and 23 species of sea mammals. The Great Barrier Reef is one of the richest and most complex natural systems in the world. The Reefs's diverse range of habitats all connect and support each other, which means they are all vital to the life of the Great Barrier Reef.

(a) The predator develops a preference to other diets and can give unforeseen negative results that could outweigh all benefits. For example, when the mongoose was introduced in Hawaii in order to control the rat population, it preyed on the endemic birds of Hawaii, especially their eggs, more often than it ate the rats. As most of the birds feed on insect and keep insect population low. The mongoose who destroy birds acts as secondary pest.

(d) Symbiosis means "living together". It is a beneficial coaction between two (or more) different species in which one or both the species are benefited and neither species is harmed. Symbiotic relationships are manifested through commensalism, protocooperation and mutualism and are widespread in nature. Commensalism is an association or relationship between two different organisms in which one is always benefitted while the other is neither benefitted nor harmed. This relationship may be permanent or temporary and the benefit derived from the other organism may consist of protection, transportation, living space and food. Protocooperation is a relationship between two or more individuals of different species in which all are benefitted by one another.

(b) The term ecology was coined by combined two Greek words, oikos (meaning 'house' or 'dwelling place') and logos (meaning 'the study of') to denote such relationships between the organisms and their environment. Thus, literally ecology is the study of organisms at 'home'.