(i) Describe growth pattern of a population growing in a habitat with limited resources.

(ii) Name the type of curve that is formed for this kind of growth.

OR

(a) Describe the Hydrarch succession.

(b) Differentiate between primary and secondary succession in water.

(i): Logistic growth pattern describes the habitat with limited resources.

_• This model defines the concept “survival of the fittest”.

_• It describes the situation in which the population density of an organism increases slowly establishing itself then increasing rapidly, approaching an exponential growth.

_• It is also known as Sigmoid shaped growth curve(s-shaped growth curve).

_• example: when a fresh culture medium is inoculated with bacteria, s-shaped growth curve is observed.The s-shaped curve is generated when a population approaches the environmental carrying capacity.

_• Carrying capacity is the maximum no. of individuals of a population that can be supported in a given time.

(ii): The type of curve seen is S-shaped growth curve.

OR

(a): Hydrarch Succession:

starting on relatively shallow water, such as ponds, lakes and culminating in mature forest is known as hydrarch succession.

_• It is also known as Hydrosere succession

_• Such a succession does not necessarily lead to the development of a land community.

_• If the water body is large and with wave action, the succession leads to formation of a large aquatic climax community.

_• if the succession starts from a small water body like pond, there is always high probability for the formation of terrestrial complex community.

_• The important characteristic of hydrosere are:

(i) usually starts from a pond

(ii) Phytoplanktons will be the pioneer community

(iii) A forest or grassland will be the climax community

(iv) Includes several stages of plant and animal communities

There are four stages of hydrarch succession:

1. Submerged aquatic plants in the deeper water

2. Emergent cattails and bulrushes rooted in the mud of shallow water

3. Willow thickets along the banks of distant shoreline

4. Conifer forest in drier, well-drained soil above the willow thickets.

(b): Differences between primary and secondary succession are as follows: