(a)(i) Ecological succession; is the orderly series of changes occurring in plant and animal or microbial communities over a period of time, resulting in the establishment of a final,stable and climax community.
(ii) Characteristics of ecological succession of plants:.
(a) Ecological succession- of plants takes place in a newly formed open habitat barren area or land.
(b) Successional changes are orderly and they develop in a certain sequence.
(c) Pioneer or earliest colonisers are hardy with short life cycle and are replaced by small herbaceous plants
(d) The rate of successional change is rapid initially but, gradually, it slows down until the final climax or stable community is reached.
(e) The number of serial communities depends on minor differences in edaphic, topographic or other local conditions.
(f) Succession occurs over a period of time.
(g) The earliest colonizers are usually very few species.
(h) During their life, the pioneers make extensive use of the material in their environment to a point of depletion.
(i) Death of the pioneer communities adds some organic matter to the soil environment, and favours the establishment of new species.
(b) Factors which affect population size are:
(i) availability of resources (e.g. water, space, food, resting sites, nesting sites)
(ii) existence of other organisms which compete for resources in the environment (interspecific competition) and thus decrease the size of the population
(iii) predators/organisms feeding on the members of the population
(iv) existence of parasites and pathogens which cause diseases and thereby reduce the population size.
(v) abiotic factors such as climatic factors, e.g. rainfall temperature, humidity, topography, soil and edaphic factors
(vi) natality and mortality effects on the population size (the greater the mortality, the less the population but the greater the natality, the greater the population size).
(vii) over crowding
(viii) migration, emigration, dispersal and immigration.
(c) Adaptation of tapeworm Taenia solium to its habitat in gut of human:
(i) Tapeworm possesses hooks on the scolex for attachment to gut wall.
(ii) It possesses suckers for attachment to gut wall.
(iii) It has a ribbon-like, flatten or tape-like body to fit into the gut of host.
(iv) It has a fast rate of proliferation of proglottides to ensure survival of the organisms or ensure perpetuation of the species.
(v) Large surface area of its body allows absorption of food from the gut.
(vi) It is a hermaphrodite and this allows successful sexual reproduction
(vii) The surface of its body is thin and permeable and allows rapid absorption of food.
(viii) The wall of its body is resistant to digestion by host digestive enzymes
(ix) Mature proglottides loaded with eggs are detached and expelled with faeces of the host for dispersal.