In an ecological succession, there is a tendency towards an increase in biodiversity (i.e. species diversity) from pioneer to climax stage due to following reasons:
(i) Environmental conditions become more and less hostile.
(ii) More and more ecological niches become available.
(iii) There is a change in types of plant and animal species towards a state of stability.
(iv) There is an increase in organic matter and biomass supported by available energy.

(a) Two examples of man-made ecosystems are: Gardens and parks, crop fields and fishery tanks.
(b) Salient features of man-made ecosystems:
(i) These are simple and highly efficient.
(ii) These are generally monoculture (e.g. field crops) with low biodiversity.
(iii) These are generally unstable
(iv) These are more vulnerable to sudden changes because of low biodiversity, stability and self-regulation.

(a) Removal of all producer reduce primary production in the ecosystem. Hence, no biomass will be available to the successive/higher trophic level or heterotrophic organisms.
(b) Elimination of all organisms of herbivore level results into an increase in primary productivity and biomass of producer and the carnivorous animal will not survive due to inavailability of food due to the elimination of herbivores.
(c) Removal of top carnivores also disturbs the ecosystem as it will result in huge increase in a number of herbivores which will finish plants creating desertification.

According to second law of thermodynamics every activity involving energy transformation is accomplished by dissipation of energy as heat and only a part of it is used in building up tissues in an organisms. If left to itself it will undergo randomness.
This trapped energy as biomass is transferred to next trophic level. According to Lindman law only 10% of the stored energy is passed from one trophic level to successive trophic level.

(a) Removal of all producer reduce primary production in the ecosystem. Hence, no biomass will be available to the successive/higher trophic level or heterotrophic organisms.
(b) Elimination of all organisms of herbivore level results into an increase in primary productivity and biomass of producer and carnivorous animal will not survive due to availability of food due to elimination of herbivores.
(c) Removal of top carnivores also disturb the ecosystem as it will result in huge increase in number of herbivores which will finish plants (producers) creating desertification.