It is generally believed that competition occurs only when closely related species compete for the same resources that are limiting.
Give two examples to show that the above statement is not always true.

There is no natural habitat on earth, which is occupied by a single species. In nature, plants, animals and microbes do not and cannot live in isolation. Interspecific interactions arise from the interaction of populations of two different species.
(a) Even a plant species, which makes its own food cannot live alone. Give two examples, where plants depend on other species for survival.
(b) Name the type of interspecific interaction seen in each of the following examples.
(i) Disappearance of smaller barnacles when Balanus dominated intertidal area of the sea coasts of Scotland.
(ii) Clown fish living among the stinging tentacles of sea anemone.
(iii) The Wasp species pollinating a fig inflorescence.
(iv) Cuscuta growing on hedge plants.

If in a population of size 'N', the birth rate is represented as 'b' and the death rate as 'd', the increase or decrease in 'N' during a unit time period 't' will be
dN/dt = (b - d) x N
The equation given above can also be represented as
dN/dt = r x N, where r = (b - d).
(a) What does 'r' represent in the above?
(b) Write anyone significance of calculating 'r' for any population.
(c) In a pond there are 100 frogs. 20 more were born in a year. Calculate the birth rate of this population.

'The population of a metro city experiences fluctuations in its population density over a period of time'.
(a) When does the population in a metro city tend to increase?
(b) When does the population in a metro city tend to decline?
(c) If 'N' is the population density at the time 't', write the population density at the time 't + l'.(Delhi 2020).

The graph given below depicts the organismic response to changing external environmental conditions. According to their response, the organisms are grouped into two types.

Answer the following questions.
(a) Name the group of organisms, which will show pattern A. Give an example.
(b) ame the group of organisms, which will show pattern B. Give an example.
(c) Define homeostasis.