Read the following statements.
I. In a population, the birth rate and death rate refer to per capita births and deaths, respectively.
II. It is uncommon to encounter solitary individuals of a particular species in natural environments.
III. The size of population for any species is a stable phenomenon
IV. The impact of ecological factors on population growth is typically manifested in the size or density of the population.
Choose the correct statements.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → I, II and IV
A population is a group of individuals of one species living in a defined area. It has attributes that a single individual does not have, such as birth rate, death rate and size, and its size keeps changing.
I. In a population, the birth rate and death rate refer to per capita births and deaths, respectively. — True. An individual may be born or die, but a population has birth and death rates, worked out per member of the population.
II. It is uncommon to encounter solitary individuals of a particular species in natural environments. — True. In nature we rarely find isolated, single individuals; most live in groups in a defined area and share or compete for resources.
III. The size of population for any species is a stable phenomenon. — False. Population size is not a static parameter. It keeps changing with food availability, predation pressure and adverse weather.
IV. The impact of ecological factors on population growth is typically manifested in the size or density of the population. — True. The effect of any ecological process, such as competition, a predator or a pesticide, is judged by the change in population size (population density).
NCERT Extract:
Population Attributes – “In nature, we rarely find isolated, single individuals of any species; majority of them live in groups in a well defined geographical area, share or compete for similar resources, potentially interbreed and thus constitute a population.”
Population Attributes – “… An individual may have births and deaths, but a population has birth rates and death rates. In a population these rates refer to per capita births and deaths.”
Population Attributes – “… The size of the population tells us a lot about its status in the habitat. Whatever ecological processes we wish to investigate in a population, be it the outcome of competition with another species, the impact of a predator or the effect of a pesticide application, we always evaluate them in terms of any change in the population size.”
Population Growth – “The size of a population for any species is not a static parameter. It keeps changing with time, depending on various factors including food availability, predation pressure and adverse weather.”