(i) Because of various types of biological(e.g. breeding behaviour, inability to form fertile hybrids) and physical barriers (e.g. habitat and geographical distribution).
(ii) Because the requirements of individuals of the same species are very similar, hence they compete more intensely.
(iii) Because parasite obtain nourishment and other things from host, e.g. they have reduced ingesting and egesting organs.

(i) Difference between upright and inverted pyramid are:

(ii) Difference between food chain and food web are:

Out of the two conservation measures, in situ will help in the survival of larger number of species. In situ is onsite conservation. which implies that species are conserved in their natural habitat.
To conserve species in their natural habitat, the entire ecosystem has to be conserved, which include other organisms, biotic and abiotic component of the ecosystem associated with the target species.
Hence, in situ conservation helps in the survival of larger number of species.

New about Neo-Darwinism: Dodson (1960) mentions, "Slow accumulation of small mutations, the screening out of combination and these by ecological factors comprise natural selection to form subspecies and finally the formation of food species by the same processes aided by isolating mechanisms, which prevent the sub-species from merging with the general population from which it came."
The Neo-Darwinism is considered to be explanatory theory as modified by new research as a highly probable and the best explanation, which we have had so far. Recently, some evidences in favour of natural selection have come up. Extensive use of D.D.T. against mosquitoes have been responsible for mutant forms which are resistant to the insecticides. These mutant species reproduced quickly and survived due to extinction of original forms. This experiment together with several other proved effectiveness of the Darwin's theory.

Offspring formed by asexual reproduction referred to as clones because they are morphologically, physiologically and genetically similar to the parent.

(i) Acetic acid - Acetobacter aceti
(ii) Butyric acid - Clostridium butylicum
(iii) Lacteric acid - Lactobacillus delbruekii

Scrubber
1. It is used to remove gases like sulphur dioxide from industrial exhaust.
2. The exhaust is passed through a spray of water or lime.
3. Water dissolves the gases and lime reacts with sulphur dioxide to form a precipitate of calcium sulphate or sulphite.

The processes included under biotechnology are:
(i) Recombinant DNA (rDNA) vaccines.
(ii) Synthesis of a gene and introduction of it into a target cell.
(iii) Gene therapy.
(iv) In vitro fertilisation for production of test-tube babies.
(v) Production of many other biological compounds like hormones, insulin, growth hormone, etc.

Stable community
(i) It shall not show too much variations in the year-to-year productivity.
(ii) It must be either resistant or resilient to sesonal disturbances.
(iii) It must be resistant to invasion of alien species.

(i) Tropical rainforest    
(ii) Deciduous forest    
(iii) Desert    
(iv) Coniferous forest    
(v) Agricultural fields    
(vi) Grassland.

(i) Grasslands,Forests.
(ii) Oceans, Ponds, Lakes.
(iii) Agricultural fields, Aquariums.

The three parts of a pistil and their functions are:
(i) Stigma - it acts as the platform where the pollen grains are lodged during pollination.
(ii) Style - it exposes the stigma for easy pollination.
(iii) Ovary - it encloses the ovule(s) inside which is the female gametophyte.

The male accessory ducts are rete testis, vasa efferentia, epididymis and vas deferens.These ducts store and transport the sperms from the testes to the outside through the urethra. The male accessory glands are paired seminal vesicles, prostate gland and paired Bulbourethral glands. The secretion of these glands forms seminal plasma, which is rich in fructose, calcium and certain enzymes. The secretion of Bulbourethral glands lubricates the glans penis.