Short Answer Type(a) Tobacco plants are damaged severely when infested with Meloidegyne incognitia. Name and explain the strategy that is adopted to stop this infestation.
(b) Name the vector used for introducing the nematode specific gene in tobacco plant.(a) Explain the phenomena of multiple allelism and co-dominanace taking ABO blood group as an example.
(b) What is the phenotype of the following:(i) IAi
(ii) i i
(a) List any three ways of measuring population density of a habitat.
(b) Mention the essential information that can be obtained by studying the population of an organism.(a) What is the programme called that is involved in improving success rate of production of desired hybrid and herd size of cattle?
(b) Explain the method used for carrying this programme for cows.
Long Answer Type(a) Explain the significance of ecological pyramids with the help of an example.
(b) Why are the pyramids referred to as upright or inverted?(a) Ecological pyramid is defined as a graphic presentation of the ecological functions like the number of individuals in the various trophic levels, the amount of biomass or the transfer of energy at different trophic levels. This give an apparently simple and fundamental basis for comparing: different ecosystems, seasonal variation within a particular ecosystem, change in an ecosystem. The size of the portion of the diagram associated with each trophic level illustrates the amount of energy, biomass, or number of individuals found in each trophic level.
There are three types of pyramids:
1. Pyramid of numbers- which represents the numbers of organisms at each trophic level.
2. Pyramid of biomass- which represents the weight (usually dry weight) or biomass of organisms at each trophic level.
3. Pyramid of energy - which monitor the energy content of the organisms at each trophic level.
For example - the pyramid of biomass in grassland ecosystem- The producers occupy the base which denotes that the biomass of producer is the highest. The herbivores like rabbits, rats etc. occupy the second trophic level followed by primary carnivores like snakes and lizards. The secondary carnivores occupy the last trophic level and have the lowest biomass.
(b) Upright pyramids - The base of most pyramid (pyramids of number, energy and biomass), representing the producers or the first trophic level is broad and it narrows down at the apex. These pyramids are called upright pyramids. It means producers are more in number and in biomass than the herbivores, and herbivores are more in number and biomass than the carnivores. Also energy at a lower trophic level is always more than that at a higher level.
Inverted pyramids - are those in which the base is narrow and the apex is broad. It denotes that the number or biomass at the first trophic level or producer level is lower as compared to the higher trophics like herbivores or carnivores. These are inverted pyramids. For example- large number of insects feeding on a big tree gives an inverted pyramid of number. The pyramid of biomass in sea is also generally inverted because the biomass of fishes far exceeds that of phytoplankton.
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