Application These bioreactors are used to produce large quantities of products enzymes, etc., using microbial, plant, animal of human cells.

Since, DNA is a hydrophilic molecule, it cannot pass through the cell membranes. In order to force bacteria to take up the plasmid, the bacterial cells must first be made competent to take up DNA. This is done by treating them with a specific concentration of a divalent cation such as calcium, which increases the efficiency with which DNA enters the bacterium through the pores in its cell wall.
Recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice, followed by placing them briefly at 42 C (heat shock) , and then putting them back on ice. This enable the bacteria to take up the recombinant DNA.

Three uses of PCR are:
(i) It is used to during rDNA for production of newer and desired DNA
(ii) It is used for DNA sequencing.
(iii) It is used in DNA figerprinting.

A - GnRH
B - FSH
C - Spermatogenesis
D - Spermiogenesis

The creation and the presence of variation is directionless in regards that they occur randomly and spontaneously. The variations which are helpful in the adaption of an organism towards its surrondings would be passed on to next generations.
Natural selection is the most critical evolutionary process,which can be considered directional as it leads to only one path that is selection and prepetuation of better adapted individuals.Natural selection leads to survival of the fittest and disappearance of all those organism which do not fit in the prevailing environmental conditions.

1.Several microbes are used in preparing medicines.
2.The most important medicines for which microbes are used are antibiotics.  These are chemical compounds produced by some microbes and are used to kill or to subside the growth of other disease-causing microbes. Streptomycin, tetracycline and penicillin are some of the commonly used antibiotics. These antibiotics have significantly contributed towards the welfare of the human society.

(i) Differences between innate immunity and acquired immunity are:

(ii) Differences between active immunity and passive immunity are:

Prevention is always better than cure because some diseases cause extensive damage to the body tissues or organs and have a
(i) negative effect on their capacity to function
(ii) permanent or long term debilitating effect.
(iii) negative mental and psychological effect.
(iv) financial burden.
Hence, it is said that prevention is easier and effective than cure of a disease.

1. Certain bacteria which grow anaerobically on cellulosic material, produce large amounts of methane along with CO₂ and H₂. These bacteria are called methanogens (one of the common bacterium is Methanobacterium). 
2. Methanogens are commonly found in the anaerobic sludge during sewage treatment and are also present in the rumen (a part of stomach) of cattle. In rumen, methanogens help in the breakdown of cellulose and their excreta called gobar, is rich in these bacteria.  Therefore, dung can be used to produce biogas commonly called as gobar gas.

(a) Fertilization takes place in the mosquito intestine.
(b) Female Anopheles in the stomach.
(c) Female Anopheles mosquito release sporozoites in human body.
(d) Human body, in liver and blood cells

If succession occurs in an area devoid of life, it is termed as primary succession. On the other hand, if succession occurs in an area where natural or man made causes have resulted in destruction but area still has organic matter, then it is termed as secondary succession.
Primary succession on a bare rock is very slow as establishment of new communities is slow process and formation of soil takes several hundred years.On the other hand, in areas where natural biotic communities have been destroyed,e.g.., because forests after fire or abondoned land after floods, succession is faster.It because such areas still have soil and sediment rich in organic matter.

The phenomenon is point mutation that involves substitution of a single nitrogenous base in DNA.

There are insemination centres throughout the country which collect the semen of superior bulls of exotic or indigenous breeds and store in the frozen form to be used at a later date. We should take our cows to these centres for artificial insemination.

Hormone insulin is synthesized as a proinsulin which consists of three polypeptide chains.It undergoes a process of maturation during which the chain C consisting of 33 amino acids is removed.The mature insulin molecule consists of two short polypeptide chains of about 51 amino acids.The chain A has 21 and the chain B has 30 amino acids which are linked together by disulphide bridges.

The earth originally had a strongly reducing atmosphere. There was no oxygen in molecular form in the primitive atmosphere.

A. Parthengenesis
B. fruit, seedless
C. embryo, seed
D. dicots, monocots
E. 4 to 5 
F. nectar fragrance, colours
G. sexual, long, poor
H. nucellus, micropyle
I. uni
J. endosperm.

Living organisms are composed of various biomolecules and there are two main macromolecules, i.e., DNA and proteins which can have structural specificity as diverse as the basic requirement of genetic material
It was believed that proteins could be the ideal candidates for genetic material because:
(1) Proteins are made up of twenty amino acids thus the diversity can be generated on the basis of the number of residues of each amino acid in a given protein and sequence of amino acid would be enormous.
(2) They are macromolecules and universally present.

primary structure of nucleic acid and protein

Species diversity is the occurrence of variety and abundance of species in community while ecological diversity is the occurrence of different ecosystem and communities in a geographical area.

Hot spots bear major number of endemic species through having the area 2 % only. Thus by protecting hot spots, rate of extinction of species can be reduced up to 30%.

'Red' in IUCN red list (2004) indicates the threatened species i.e. the species under varying degree of extinction risk categories.

Glaciation, melting of snow, eruption of large volcanoes, earthquakes, movement of continents, large meteorites falling on earth, drought, etc. could have triggered mass extinction.

1. We are still not clear whether evolution and natural selection are processes or results of some unknown processes.
2. On one hand, when we describe the world as we see today, we describe evolution a process.
3. On the other hand, when we describe life on earth, we treat evolution as a consequences of the process of natural selection.

With the industrial growth in 1920, the white-winged grey-coloured Biston betularia was rapidly replaced by a dark-coloured melanic Biston carbonaria as the later had more chances of survival and favoured by Natural selection. But after 1956, the coal was rapidly replaced by oil and electricity as energy source in the industries which reduced soot deposition. So the light coloured moth is again replacing the dark-coloured moth by reverse evolution.

Meiotic division during oogenesis is different from that of spermatogenesis in the following ways

(i) Unequal cell division makes the ovum much larger than the other three polar bodies. As, ovum has more
cyloplasm and more organelles, it has a better chance of survival.
(ii) The male makes millions of tiny sperms, while the female makes only one egg per month that also arrested for second meiotic division, until just before fertilisation. This is a way of conserving energy.
(iüi) Sperm is smaller and motile as it has to move out of male system to female reproductive system. Larger egg has abundant reserve food, so thal embryo starts developing right after fertilisation.