(i) Freshwater (Lakes, ponds, and rivers)
(ii) Brackish water (Estuaries and Wetlands)
(iii) Marine (Coral reefs, pelagic zones, and abyssal zones)

This is the level of exposure of plants to environmental factors that leads to neither injury nor reduction in growth and yield of crops.

1. Animals are known to modify their response to environmental changes (stress) in reasonably short time of spans. This known as Acclimatisation.
2. This is observed when people who have moved from the plains to higher altitudes show enhanced RBC count within a few days of settling in their new habitat. This helps them cope with lower atmospheric oxygen and higher oxygen demand.

The natural home (or) environment of an animal, plant or other organism or it can be considered as the address of an organism

(i) Ecological density: It is the size of a population in relation to the numbers per unit of habitat space. (Available area or volume that can be colonized by a population). Eg. 1000 fish in the volume of water in the pond.
(ii) Crude density: It is the size of a population in relation to the numbers per unit of total space. Eg. 1000 fish in a pond.
(iii) Population density: It is usually expressed as the number of individuals per unit area or volume. Eg. 100 trees per acre.

S. No.	J shaped curve	S shaped curve
1.	When a population increases rapidly in an exponential fashion and then stops abruptly due to environmental resistance or due to sudden appearance of a limiting factor, they are said to exhibit J-shaped growth form,	Some populations, as in a population of small mammals, increase lowly at first then more rapidly & gradually slow down as environmental resistance increases where by equilibrium is reached and maintained
2.	Many insects show explosive increase in  number during the rainy season followed by their disappearance at the end of season.	Their growth is represented by s shaped growth curve.

Biotic potential:
It is the maximum reproductive capacity of an organism under optimum environmental conditions.
Carrying capacity:
The maximum number of organisms live in a region can support without environmental degradation is called carrying capacity.
Environmental resistance:
Is the sum total of the environmental limiting factors, both biotic and abiotic which together act to prevent the biotic potential of an organism from being realized.

Properties of soil
(i) Texture of soil - The texture of soil is determined by the size of the soil particles. The types of soil include sand, silt and clay on the basis of their size differences.
(ii) Porosity - The space present between soil particles in a given volume of soil are called pore spaces. The percentage of soil volume occupied by pore space or by the interstitial spaces is called porosity of the soil.
(iii) Permeability of soil - The characteristic of soil that determines the movement of water through pore spaces is known as soil permeability. Soil permeability is directly dependent on the pore size. Water holding capacity of the soil is inversely dependent on soil porosity.
(iv) Soil Temperature - Soil gets its heat energy from solar radiation, decomposing organic matter, and heat from the interior of the earth. Soil temperature affects the germination of seeds, growth of roots and biological activity of soil-inhabiting micro-and macro-organisms.
(v) Soil water - In soil, water is not only important as a solvent and transporting agent, but also maintains soil texture, arrangement, and compactness of soil particles, making soil habitable for plants and animals.