a forest hardly has any carnivores. census of herbivores mammals was taken and plotted as a graph shown above. identify the curve that will explain the population growth of herbivores. give reason
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Important Questions for CBSE Class 12 Biology Population
December 6, 2019 by Sastry CBSE
Organisms and Populations Important Questions for CBSE Class 12 Biology Population
1.Population can be defined as the total number of individuals of a species in a specific geographical area, which can interbreed under natural conditions to produce fertile offsprings and function as a unit of biotic community.
2.Population ecology is an important area of ecology as it links ecology to the population genetics and evolution.
3.Population attributes are certain characteristics of a population.
Some of them are as follow:
(i) Population size or density is the number of individuals of a species per unit area or volume.
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(ii)Birth or natality rate is expressed as the number of births per 1000 individuals of a population per year, e.g. if in a pond, there are 20 lotus plants last year and through reproduction, 8 new plants are added
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(iii)Death or mortality rate is expressed as the number of deaths per 1000individuals of a population per year, e.g. if 4 individuals in a population of 40 fruit flies died during a specified time interval (say a week).
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(iv)Sex ratio is expressed as the number of females and males per 1000 individuals of a
population in a given time, e.g. 60% females and 40% males in population.
(v)Age pyramid
When the age distribution (per cent individuals of a given age or age group) is plotted for the population, this is called age pyramid.
Population at any given time is composed of individuals of different ages.
For human population, the age pyramids generally show age distribution of males and females in a combined diagram.
The shape of the pyramids reflects the growth status of the population that whether it is expanding (triangular shaped), stable (bell-shaped) or declining.
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4.Population growth
(i)The size of a population for any species is not a static parameter.
(ii)It keeps changing in time, depending on various factors including food availability, predation, pressure and adverse weather.
(iii)The population density depends on:
Natality is the number of births during a given period in the population that are added to the initial density.
Mortality is the number of deaths in the population during a given period.
Immigration is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration.
Emigration is the number of individuals of the population who left the habitat and moved elsewhere during a given time period.important-questions-for-class-12-biology-cbse-population-t-13-10