Ecology Answers

Prepare a detailed account on any one of the following environmental components:
atmosphere, water, soil.

Klinotaxis occurs in organisms with receptor cells but no paired receptor organs. The cells for reception are located all over the body, particularly towards the anterior side. The organisms detect the stimuli by turning their head sideways and compare the intensity. When the intensity of stimuli is balanced equally from all sides then the organisms move in a straight line. The movement of blowfly and butterfly larvae clearly demonstrates klinotaxis.

Tropotaxis is displayed by organisms with paired receptor cells. When the stimuli coming from a source are balanced equally the organisms show movement. Because of this, animals are able to move sideways, unlike klinotaxis where the organisms can move only in a straight line. The movement of Grayling butterflies and fish lice clearly demonstrates tropotaxis.

I don't understand the part , because of this the animals are able to move sideways. Could you explain?

I was reading Information theory by Eleith, Odum and Golley from different sources, one of which was Funfamentals of ecology by Odum:
... autogenic succession usually begins with an unbalanced community metabolism, where gross production, P, is either greater than or less than community respiration, R, and proceeds towards a more balanced condition, where P=R. The rate of biomass production (B/P ) increases during sucession until a stabilised system is achieved, in which a maximum of biomass (or high information content) and symbiosis between organisms are maintained per unit of available energy flow.
The succession begins with P>R in autotrophic sucession and P<R in heterotrophic sucession.
I have tried to find explanatory texts both in this and other books without any success so my question is how's this balanced state achieved in both types of successions?