31 Years NEET Previous Year Questions: Organisms & Populations - 1

While they do not rule out the occurrence of interspecific competition in nature, they point out that species facing competition might evolve mechanisms that promote co-existence rather than exclusion. One such mechanism is ‘resource partitioning'.

Species interaction refers to direct and indirect interrelationship between different organisms, while on the other hand population attributes include population size, population density, population spacing, and age structure. Mortality is the ratio of deaths in an area to the population of that area; expressed per 1000 per year. Sex ratio is  the ratio of males to females in a population.

Natality refers to the number of births during a given period in the population that are added to the initial density. Death rate or mortality is the number of deaths in the population during a given time period. Immigration is the number of individuals entering a habitat. Emigration is the number of individuals of the population that left the habitat and had gone elsewhere during a time period.

Asymptote in a logistic growth curve is obtained when population density (N) reaches the carrying capacity (K), i.e., N = K.

Logistic growth of a population size occurs when resources are limited. The formula we use to calculate logistic growth adds the carrying capacity as a moderating force in the growth rate. 

► The logistic model is given as dN/dt = rN(1-N/K) 

When the value of N/K is one, then,

► dN/dt = rN(1-N/K) 
► dN/dt = rN(1-1)
► dN/dt = rN(0)
► dN/dt = 0 (zero)

So, the growth rate of the population will be equal to zero.

Gause's principle of competitive exclusion can be restated to say that no two species can occupy the same niche indefinitely when resources are limiting.

Gause's theory predicts that when two species coexist on a long-term basis, either resources must not be limited or their niches will always differ in one or more features; otherwise, one species will outcompete the other and the extinction of the second species will inevitably result, a process referred to as competitive exclusion.

Competition occurs for light, food and space among organisms in which all partners are adversely affected in an ecosystom.

Most animals that live in deep oceanic waters and called benthos are scavengers or detritivores i.e. organisms that feed on dead plants and animal residues.

• The Hardy-Weinberg equilibrium states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
• These influences include mate choice, mutation, selection, genetic drift, gene flow, and meiotic drive.
• Because one or more of these influences are typically present in real populations, the Hardy-Weinberg principle describes an ideal condition against which the effects of these influences can be analyzed.

In tropical rain forest zone, most of the animals prefer to live on trees. The reason is that the floor of forest is full of humidity, decomposing leaves and other organic matters and is the habitat of insects etc.

• According to the 10 percent law, during the transfer of energy from organic food from one trophic level to the next, only about ten percent of energy from organic matter is stored as flesh. The remaining is lost during transfer, broken down in respiration, or lost to incomplete digestion by higher trophic levels.
• If 20 J of energy is trapped at the producer level, then 0.02 J of energy will be available to peacock as food in the given food chain.

The ozone (O₃ ) found in upper part of the atmosphere, i.e., Stratosphere, is Good ozone, since, it acts as a shield for absorbing UV-radiations from sun.

• The Keoladeo National Park is a famous avifauna sanctuary in India that plays host to thousands of birds especially during the summer season. It is formerly known as the Bharatpur Bird Sanctuary in Bharatpur, Rajasthan.
• October to February is the best time, for the migratory birds are there as well as the residents. In August local birds start their nest building and rear their young for the next few months. October/November is when the migrants arrive. Most stay till March including the Siberian Crane.

Phosphorus is a major constituent of the biological membrane, nucleic acids, and cellular energy transfer system. 

• Detritus is leaf litter and other organic matter intermixed with soil, which is referred to as humus. This detritus or dead organic material and its constituent nutrients are added to the top layer of soil, commonly known as the litter layer.
• Rocks are composed of one or more minerals. 
• Primary producers are organisms in an ecosystem that produce biomass from inorganic compounds (autotrophs). 
• Litterfall is dead plant material, such as leaves, bark, needles, and twigs, that has fallen to the ground.