31 Years NEET Previous Year Questions: Organisms & Populations - 2 - NEET MCQ

Cuscuta, or Dodder plant, is a parasitic plant that wraps around other plants for nourishment. Cuscuta is found on outer side of the host and is total stem parasite. Cuscuta a parasite of Acacia.

Secondary succession refers to the regrowth of a habitat in the area where disruptive event has occurred and eliminated the existing, above ground plant life of the natural habitat. So, it occurs on a deforested site.

Large woody vines are more commonly found in tropical rain forests. This is a common concern in the high humidity climatic condition.

‘A’ is more recent and shows slight reduction in growth rate.

There is a decline in population as boys marry girls only from their own tribe in the isolated small tribal populations. 

It is competition between individuals of same species. The intraspecific competition may be very severe because all the members of a species have similar requirements of food, habitat mate, etc and they also have similar adaptations to get their needs.

When the members of a species are inter - fertile and produce fertile offsprings.

If a population (e.g reindeer population) is allowed to grow in a predator free environment, the population grows beyond carrying capacity and there occurs population crash due to sudden shortage of food. Such growth curves also occur in insect populations during rainy season, and in algal blooms.

Geometric representation of age structure a characteristic of population.

Praying mantis is a good example of camouflage. Camouflage is the natural colouring of an animal which enables it to blend in with its surroundings.
A praying mantis, or praying mantid, is the common name for an insect of the order Mantodea. Often mistakenly spelled preying mantis (a tempting mistake, as they are notoriously predatory) they are in fact named for the typical “prayer-like” stance. The word mantis derives from the Greek word mantis for prophet or fortune teller. A praying mantis from India

The formula of exponential growth is  is the rate of change in population size, r is the biotic potential and N is the population size.

Niche indicate the habitat of a particular species and the interaction of that species with the resources present in the habitat. Niche overlap means that two or more species sharing the resources present in a particular niche.

Demography is the study of population in all aspects. Fertility refers to the number of children per couple. Mortality rate is the average number of natural deaths per unit  population per unit time. Age distribution refers to the proportionate occurrence of individuals of the three age groups. Developing countries usually  have high rate of population growth, because of increasing fertility and declining mortality.

In the sigmoid growth cur ve growth is slow in the lag phase. Growth rate remains stable during the stationary phase and it declines during the senescent phase. Growth increases logarithmically during the exponential phase.

Desert show maximum difference between day and night temperature.

A keystone species is the one which makes up only a small proportion of the total biomass of a community, yet has a huge impact on the community’s organization and survival.

Diffused porous wood have vessels irregularly arranged within the wood. In tropics, there is no sharp distinction between the seasons; hence, there is not much difference in the activity of cambium.

Semilog of per minute growing bacterium when plotted against time, would yield ascending straight line.

The growth curve for bacteria is sigmoid. First phase is the phase of slow growth- Lag phase. Second phase is the period of accelerated growth - Log phase. Third phase is the phase when growth rate  becomes stable - Stationary phase. Finally growth rate declines.

The biotic potential is defined as the physiological capacity of organisms to produce their offspring under natural conditions. It is also called reproductive potential. In nature, the biotic potential of organisms is enormous but all the organisms do not survive due to the lack of food and space. There are also a number of diseases and predatory organisms, that feed upon other organisms. The carrying capacity is the maximum number of individuals which the environment can support or sustain.

Tropical rain forests occur in equatorial and subequatorial regions. The forests receive all the external inputs for optimum plant growth.  Due to abundant plant growth, a large number of animals live in tropical rain forests. In grasslands fire occur periodically which prevent tree growth. In savannahs periods of drought are common. In deciduous forests are found predominantly broad leaved hard wood deciduous trees.

Tropical forests are found in tropical zone of the world and are characterised by very high temperature with rainfall in abundance. The flora of tropical rain forest is very rich and highly diversified. The tropical forests have a very rich fauna both in density as well as in varieties. The reason for this high diversity and variety of flora and fauna is the occurence of suitable conditions in these forests. So these are more vulnerable to invasion by outside plants and animals.

Mortality is the average number of natural deaths per unit population per unit time. Fecundity refers to the biotic potential of the organism. Environmental resistance is the sum total of all limiting factors that prevents a population to realize its full potential.

For its pollination the orchid Ophrys speculum has picked on the most selective attraction in the entire animal kingdom. It is pollinated by a hairy wasp, Colpa aurea. The wasp has a fixed habit whereby its males leave the burrows for above-ground existence about four weeks before the females emerge for the open-air mating. The orchid opens its flowers about the same time the males appear and they possess an appearance and odour similar to those possessed by the female wasps. The inexperienced males mistake the Ophrys flowers for their female counterparts and land to perform the act of pseudo-copulation. The insect repeats the act with a number of orchid flowers and carries pollinia from one flower to another. This insect-plant relationship is beneficial only to the plant.

Biotic potential is the inherent ability of an organism to reproduce.  Resistance refers to the sum total of all the limiting factors that inhibit further growth of population.