NEET Biology Organisms and Populations
Organisms and Populations PDF Notes, Important Questions and Synopsis
- Ecology is a branch of biology which deals with the inter-relationships among organisms and interactions between organisms and their environment.
- Homeostasis is a self-regulatory mechanism to maintain the internal environment constant despite changes in the external environment.
- Regulators are organisms which maintain their homeostasis by physiological means to ensure constant body temperature and osmotic concentration irrespective of the fluctuations in the external environment; for example, birds and mammals.
- Conformers are organisms which cannot maintain a constant internal environment; for example, fish and reptiles.
- Adaptation is the development of certain features in an organism in response to a particular environment which may improve its chances of survival and reproduction in the habitat.
- Differences between Hibernation and Aestivation
Population is defined as a group of organisms of the same kind at a particular time which occupy a particular space.
Population density is defined as the number of individuals present in a unit area at a given time.
Factors Affecting Population Density
Natality is the increase in the number of individuals in a population under the given environmental conditions.
Mortality is the loss of individuals due to death in a population under the given environmental conditions.
Age Pyramids for Human Population
Population growth can be measured as an increase in the size of a population over a period of time.
Population exhibits a characteristic pattern of increase known as the population growth curve.
Exponential (J-shaped) growth curve: When the resources are not limiting the growth, the plot is exponential (curve a).
Logistic (S-shaped) growth curve: When responses are limiting the growth, the plot is logistic (curve b).
The interaction of populations of two or more different species is known as population interaction.
Gauss gave the competitive exclusion principle which states that two closely related species competing for the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated eventually.
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