NEET Biology Notes Organisms and Ecosystem Organisms and their Environment
Organisms and their Environment
Ecology
The term ‘ecology’ was introduced by Reiter in 1868 and E Haeckel (1869) defined it as the study of natural environment including the relations of organisms to one another and to their surroundings. R Mishra is known as Father of Indian Ecology. He defined ecology, it as the interaction of form, functions and factors.
Autecology
It is the branch of ecology, which is concerned with the study of an individual organism (an individual species).
Synecology
It is the branch of ecology, which deals with the study of a group (or groups) of. organisms that are associated together as a unit.
Organisms and their Environment
Ecology at the organismic level is essentially physiological ecology, which tries to understand how different organisms are adapted to their environments in terms of not only survival but also reproduction.
The variations in precipitations leads to the formation of major biomes such as desert, rainforest and tundra.
Habitat and Niche
Habitat It is a place where an organism lives. It represents a particular set of environmental conditions suitable for its successful growth.
Life exists on different habitats like grassland, deserts, tropical and temperature forests, coniferous forests, arctic and alpine tundra, deep ocean trenches, torrential streams, permafrost polar regions, high mountain tops, boiling thermal spring, stinking compost pits and even air intestine is a unique habitat for many microbes.
Ecological niche It is of an organism includes the physical space occupied by it, its functional role in the community and the conditions of existence.
- Each species has its own unique niche.
- Two species cannot occupy exactly same niche and coexist.
- Closely related species of competitors will have similar requirements along the niche dimensions, so that their niche will overlap one another partially or fully.
- If the niche of one species completely overlaps that of another, then one of the species will be eliminated.
- If the niche overlaps partially, coexistence is possible in two ways:
- One species fully occupies its own fundamental niche excluding the second species from parts of its fundamental niche and leaving it to occupy a smaller realised niche.
- Both species have restricted realised niches, each utilising a smaller range of particular niche dimensions than they would in the absence of other species.
Environmental Factors
- The habitat includes both biotic and abiotic factors.
- Biotic factors mostly influence growth and reproduction. It contain
- Plants
- Animals
- Microbes
- nteraction of organisms
- Abiotic factors are temperature, water, light and soil.
- Temperature governs the functions and geographical distribution of organisms. Some organisms are eurythermal, while others are stenothermal.
- Water is an important factor for life. Organism may be euryhaline (tolerate wide range of salinity) or stenohaline (can tolerate only a narrow range of salinity).
- Light influences life on earth as plants prepare food and release oxygen during photosynthesis.
- Soil sustains life on earth. The physical and chemical properties of soil, such as grain size, porosity, pH and mineral composition determine the type of plant that can grow in a particular habitat.
Population
It is a unit of biotic community made up of near , permanent group of interbreeding individuals of a species found in a space at a particular time.
Different population characteristics are as follows:
Population Attributes
A population has certain attributes that an individual organisms does not have.
These are as follows:
- Birth rate (natality)
- Death rate (mortality)
- Sex ratio
- Immigration
- Emigration
In any population, three ecological age groups are
- Pre-reproductive
- Reproductive
- Post-reproductive
The age pyramids reflect the growth status of population. These are as follows:
- An expanding/growing population
- A stable population
- A declining population Post-reproductive
- Population Growth
Population growth depends on factors like
- Food availability
- Weather
- Predation pressure
- Competition
The equation for population growth is
The maximum population of species that a particular environment can sustain is called carrying capacity.
The population growth models are
- Exponential growth model
- Logistic growth model
When the resource availability is unlimited in the habitat, the population grows in an exponential or geometric fashion. No population can continue to grow exponentially as the resource availability becomes limiting at certain point of time.
A population showing logistic growth shows sigmoid curve. This growth model is more realistic in nature.
Population Interactions
Living organisms cannot live in isolation and they do interact in various ways to form biological communities. Interspecific interactions arise from the interaction of populations of two different species. They could be beneficial, detrimental or neutral.
The organisms in a population interact in the following ways:
- Mutualism
It is the interspecific interaction in which both the interacting species are benefitted. - Predation
It is an interspecific interaction, where one animal (predator) kills and consumes the other weaker animal (called prey). - Parasitism
It is the interspecific interaction, where one of the species depends on the other species for food and shelter, in this process, the host is damaged. - Commensalism
It is the interspecific interaction, where one species is benefitted, while the other species is neither benefitted nor harmed. - Competition
It is a type of interaction either among individuals of the same species (intraspecific) or between individuals/ population of different species (interspecific competition). - Amensalism
It is the interaction between two different species, in which one species is harmed and the other is neither benefitted nor harmed.
Adaptations
Adaptation is any attribute of the organisms (morphological, physiological and behavioural) that enables the organism to survive and reproduce in its habitat.
Many adaptations have evolved over a long evolutionary time and are genetically fixed. For example, in the absence of external source of water, the kangaroo rat in North American deserts is capable of meeting all its The tribes living at high altitudes of mountains have a higher count of red blood cells and haemoglobin and high vital capacity than people living in plains.
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