Diseases outbreaks associated with high population on the Island discourages immigration of organisms to the Island Natural calamities such as earthquake, fire, floods may also discourage immigration of organism to the Island. The rate of extinction of organism on Islands increase exponentially with increase with the number of species on the island. Environment resistance in form of diseases reduces the number of organisms on the island. The producing population on the island may be so small that the chances of finding a mate is very low. This makes the organism to dies before producing young ones leading to extinction. The number of predators increase on the island eat the prey to extinction. Natural calamities such as flood may cause massive death of organism leading to their extinction. Competition for resources such as food, shelter and mates increase as the population increases. The better adapted species survive while the less adapted die or escape from the island and eventually become extinct. From figure 1, 2, 3 what conclusions can you draw what determines the number of species on an island? (05marks) Size of the island Distance of the island from the shore Number of species on the island Rate of immigration to the island Rate of extinction of organism from the island Describe how factors other than those depicted in information provided, may affect the immigration of new species on an island. (4marks) Resource availability; if an island has a large resource base, more species are attracted to it. However, the number of immigrants eventually reduce the resource on the island leading to extinction of species. Predation: presence of predators on the island discourage immigration of the prey organism, presence of the prey encourages immigration of the predator. Species mobility; species that can fly or swim are able to migrate to a fur island or run away from predators and can easily search for food. Environmental conditions on the island: favorable conditions on the island encourage immigration of large number of species. Accidental introduction of new species to island, Suggest the factors that would cause immigration of new species to a virgin land. (5marks) Availability of food Availability of shelter Absence of predator
Provide information for conservation forest reserve and management of national parks. To be able to value wild life resources and design/alter boundaries of various conservational areas. Differentiate between sample count and total count Give five factors to be considered before carrying out a counting exercise. Natural vegetation Size of organisms to be counted\ Behavior/social structure/activity of the organism to be counted Nature of the habitat: aquatic or terrestrial Available resources e.g. apparatus, transport, camera, money. Describe a suitable method you would use to estimate the population of Fish e.g. tilapia in a lake Capture-mark-release recapture/ Lincoln index method Gill netting Reason Because fish is large in size and can easily be identified and capture and counted. Lincoln index method No fish are gill-netted and after their operculum tagged with an inconspicuous aluminium discs and then released back into the water without harming them. After some tome N1 fish is netted again, and N2 fish found marked. The population of fish N in a lake is then estimated from Flying insects in an open woodland. Removal method Reason They are small and mobile Using a net, in form of a sweep net, the number of insect captured is recorded. This procedure is repeated a further three times and gradually reducing numbers are recorded. A graph of number of insects per sample against the previous cumulative number of insect is plotted By extra plotting the line of the graph to the point at which no further animals would be captured, the total population of insects is determined. 21 1998/2/1 A study was carried out on a plant of two species of Lemna duckweed. In one experiment they were cultured separately, in another together. Two growth curves were sketched for both experiments. Study the graphs and answer the questions