(a) Difference between repetitive DNA and satellite DNA.

(b) Difference between mRNA and tRNA 

(c) Difference between Template strand and Coding strand

(i) Earthworms are known as detritivores as they breakdown  detritus(dead remains of plants and animals) into smaller particles. Earthworms are often called farmer's friend.
(ii) Fragmentation is the first step in the process of decomposition. It is the process by which detritivores (e.g. earthworm) breakdown detritus in smaller particles.
(iii) The steps involved in decomposition are fragmentation, leaching, catabolism, humification and mineralisation.
(iv) Arun is very alert, curious and had scientific attitude.

The menstrual cycle is controlled by rhythmic synthesis and release of ovarian hormones under feedback control from the hormones of anterior pituitary. These are discussed below:
(i) Pituitary hormones The gonadotroph cells, of anterior pituitary secrete FSH and LH in females. Their role in menstrual cycle are:
(a) Follicle Stimulating Hormone (FSH) It is secreted during the follicular phase of the cycle and is responsible for follicular development on induction of LH receptors on granulosa cells of the ovary.
(b) Luteinising Hormone (LH) Its primary function is to stimulate the formation of corpus luteum and secretion of estradiol and progesterone from ovary.
(ii) Ovarian hormones Ovary secretes the following hormones under the effect of FSH and LH.
(a) Oestrogen It influences proliferation of the uterine endometrium to prepare for implantation of the fertilised oocyte.
(b) Progesterone secreted from corpus luteum under LH influence, maintains endometrium for implantation It rising level inhibits LH.

Plants require sunlight for photosynthesis. Therefore, light is an important factor that affects the distribution of plants, e.g.,
(i) Many species of small plants (herbs and shrubs) growing in forests are adapted to photosynthesis optimally under very low light conditions so they are seen distributed in shady areas under tall, canopied trees.
(ii) Many plants in the shade will grow vertically to gain access to light. These plants will appear to have maller4 leafs than others of the same species of the same age found in conditions with better sunlight.
(iii) Large sized trees will be present in areas that get abundant sunlight.
(iv) Plants dependent on sunlight to meet their photoperiodic requirements of flowering, will try to be distributed in area where this requirement is being met for their reproductive success.

Genetic engineering is a manipulation of genetic material in vitro. It involves the techniques to alter the chemistry of genetic material (DNA and RNA), to introduce the host organisms and thereby change the phenotype of the host organism.
Steps of rDNA technology are:
(i) Isolation of DNA.
(ii) Fragmentation of DNA by restriction endonucleases.
(iii) Isolation of the desired DNA fragments.
(iv) Amplification of the gene of interest.
(v) Ligation of the DNA fragment into the victor using DNA ligase.
(vi) Transfer of the recombinant DNA into the host.
(vii) Culturing the host cell on a suitable medium on a large scale.
(viii) Extraction of the desired product.
(ix) Downstream processing of the products as finished products.

(a)
(b) The virus is called retro virus because its genetic material is RNA that is transcribed to DNA using enzyme reverse transciptase.
(c) Yes, the infected cell can survive, while viruses are being replicated and released.

(i) To understand the problem faced by the family and the nation due to increasing population and the benefits of having a small family.
(ii) Role of Government in controlling population explosion are:
(a) Creating public awareness through mass media.
(b) Education at all Levels.
(c) Family planning.
(d) Increasing marriageable age (18 for girls and 21 for boys)
(iii) In India, these programmes called 'family planning' were initiated in 1951.
(iv) Rohit and his friends showed understanding about the problem of population explosion, teamwork, and motivational capacity.

Plant breeding technology used in the green revolution has made us self-sufficient in food production. This has helped in the development of high yielding and disease resistant varieties in wheat, rice, maize, etc.

(i) Animal breeding is a branch of animals husbandry that aims to increase the animal yield and improvement of desirable qualities of animal product.
(iii) New breed of cattle and poultry are Jersey and Leghorn respectively.

Difference between spermatogenesis and oogenesis are as follows

Fig 1. represents  interaction between individuals of a single population.
Fig 2. represents  interaction between individuals of 3species (A,B,C) in a community.
Fig 3. represents a biome having 3 communities at different stages of development

(i) Golden rice is variety of rice in which rice grain has a coating of beta carotene, a precursor of vitamin A.
(ii) It is very useful for poor rice eating human population which generally suffers from vitamin A deficiency.
(iii) Being a farmer, Anil's grandfather was concerned about the latest development in agriculture and wanted to grow such varieties which provide better nutrition contents to human beings.

(i)  These are the organisms which contain functional foreign genes.
(ii) These are produced by experimentally introduced gene into their genome by genetic engineering from another species.
(iii) Hari's friend helped him by advising him transgenic crop having delayed ripening property.

(a) Removal of all producer reduce primary production in the ecosystem. Hence, no biomass will be available to the successive/higher trophic level or heterotrophic organisms.
(b) Elimination of all organisms of herbivore level results into an increase in primary productivity and biomass of producer and the carnivorous animal will not survive due to inavailability of food due to the elimination of herbivores.
(c) Removal of top carnivores also disturbs the ecosystem as it will result in huge increase in a number of herbivores which will finish plants creating desertification.

According to second law of thermodynamics every activity involving energy transformation is accomplished by dissipation of energy as heat and only a part of it is used in building up tissues in an organisms. If left to itself it will undergo randomness.
This trapped energy as biomass is transferred to next trophic level. According to Lindman law only 10% of the stored energy is passed from one trophic level to successive trophic level.

(a) Removal of all producer reduce primary production in the ecosystem. Hence, no biomass will be available to the successive/higher trophic level or heterotrophic organisms.
(b) Elimination of all organisms of herbivore level results into an increase in primary productivity and biomass of producer and carnivorous animal will not survive due to availability of food due to elimination of herbivores.
(c) Removal of top carnivores also disturb the ecosystem as it will result in huge increase in number of herbivores which will finish plants (producers) creating desertification.

(a) Removal of all producer reduce primary production in the ecosystem. Hence, no biomass will be available to the successive/higher trophic level or heterotrophic organisms.
(b) Elimination of all organisms of herbivore level results into an increase in primary productivity and biomass of producer and carnivorous animal will not survive due to availability of food due to elimination of herbivores.
(c) Removal of top carnivores also disturb the ecosystem as it will result in huge increase in number of herbivores which will finish plants (producers) creating desertification.

Primary productivity can be defined as the rate at which primary producers (e.g. green plants) traps and store solar radiation in the form of biomass. This is measured in terms of weight (gm) and in terms of energy (kcal m²) per year in a given time.
So, primary productivity varies from ecosystem to ecosystem. The ecosystem which possesses more producers will be more productive in terms of primary productivity. The young forest is still developing it may contain fewer trees compared to the old forests. The young forests therefore will not quench the solar radiation as much as old forests. Hence, old forest is more productive as compared to foung one. The shallow polluted lake will be less productive because of less number of producers and high amount of dead organic matter.

In terms of ecosystem dynamics, flow of energy takes place from one trophic level to the next trophic level in unidirectional way. About 50% of solar energy incident over earth is present in Photosynthetic Active Radiation (PAR) and 2-10% of this PAR is utilised by green plants to form chemical energy(Gross Primary Productivity) (GPP). Out of 90% of gross primary productivity is lost maximum during respiration and other vital activities. Gross Primary Productivity of an ecosystem is the rate of production of organic matter during photosynthesis. So nature tend to increase gross primary productivity through supporting the large number of plant (producers) in an ecosystem. Net Primary Productivity is the available biomass for the consumption to heterotrophs (human and animals) man tries to increase net primary productivity by cultivating food and other crops which the depend on to fulfil their needs.

Species diversity decrease as we move towards the poles, because 
(i) Temperature decrease and conditions become harsh.
(ii) Both the amount and intensity of solar radiation decrease.
(iii) Less resources available to support species.
Speciation is generally a function of time and environmental stability, so if condition are too harsh, it is difficult for the species to survive and adapt. this results in decrease in biodiversity towards the poles.

Scientific explanation for the direct relationship between diversity and stability of an ecosystem could be as follows 
If a specific plant species dies, the related insect population will be affected that would lead to unavailability of food for the birds.
In addition, if the plant species was a nitrogen fixer, the death of these plants would mean no replenishment of soil with nitrogen. This will obviously affect the other plants as well. So, if the cycle continues, the whole habitat/ecosystem will be negatively affected.

(A) Role of modern methods of breeding animals:
(i) By continued inbreeding, superior genes can be accumulated and less desirable genes can be eliminated by selection. It is also used to produce pure line.
(ii) By cross-breeding, good characters of different breeds can be combined to produce high yielding hybrid animals Examples 1.Karan Swiss breed of Switzerland and Sahiwal of India and gives about 3,500 litres of milk during its lactation period of 300 days.
2. High yielding layers of fowls e.g. IBL-80; B-77 and HH-260 are also cross-breeds out of which IBL-80 and B-77 breeds produce 200 eggs while HH-260 produces 260 eggs in a year.
3. Hissardale is a high wool and meat-yielding cross breed of sheep, while mules are more sturdier and stronger interspecific hybrids produced by a cross between male donkey and female horse (mare).
(iii) Multiple Ovulation-Embryo Transfer (MOET):
(iv) Artificial Insemination 
(B)Role of modern methods of plant breeding:
1. Green revolution.
2. Genetically modified crops.

(a) For forming 1 kg of meat about 3-10 kg of cereal is consumed. Thus if one shifts from grain to meat, consumption of cereals will be increased.
(b) Use of SCP microbes, no doubt is emerging area of research. SCP microbes are rich in proteins.

Amniocentesis is a foetal sex determination test based upon the chromosomal pattern in the amniotic fluid surrounding the developing embryo. It should be legally banned throughout the country as such a ban shall check increasing female foeticide cases and maintain a normal sex rJtio in the country.

Hormonal Control of Menstrual Cycle.
Gonadotropin-releasing hormone (GnRH) also called Gonadotropin-releasing Factor (GnRF), is secreted by the hypothalamus of the brain, which stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).FSH stimulates the ovarian follicles to produce oestrogens during proliferative phase.LH stimulates the corpus luteum of the ovary to secrete progesterone.
1.Menstrual phase is caused by the reduction of progesterone and oestrogens.
2.Proliferative phase is caused by the increased production of oestrogens.
3.LH causes ovulation.
LH also causes transformation of empty Graafian follicle into corpus luteum by luteinisation inside the ovary. LH also stimulates corpus luteum to secrete progesterone hormone to help in implantation, placentation and maintenance of pregnancy.
4.Secretary phase is caused by increased production of progesterone.