(i)No,it was not a wise decision.
(ii) Insecticides kill the insects.These insects are very important for plants as many of these are helpful in carrying out pollination which is very essential for fertilization and seed formation in sexually reproducing species.
(iii)No,many insecticides pollute and, being non-biodegradable, have harmful effects on living organisms

Common human diseases

Ozone layer as protective layer:
The ozone layer in the stratosphere is very useful to human beings because it absorbs the major part of harmful ultraviolet radiation coming from the sun. Therefore, it is called protective layer. However, it has been observed that the ozone layer is getting depleted. One of the reasons for depletion of ozone layer is action of aerosols spray propellants. These are the chemicals such as fluorocarbons and chloro-fluorocarbons. These compounds react with ozone gas in the atmosphere thereby depleting it. Scientists all over the world are worried at the destruction of ozone layer. If the ozone layer in the atmosphere is significantly decreased, these harmful radiations would reach the earth and would cause many damages such as skin cancer, genetic disorders in man and other living forms. Efforts are being made to find substitutes of these chemicals which do not react with ozone.

Structure of Epithelio-chorial placenta. Epithelio-chorial placenta is the simple and basic type of placenta as formed in cow, goat etc. In this case some of the components are derived from the uterine wall of mother while the other parts are derived from the foetus itself.

The maternal components of placenta are:
1. Mucous membrane of the uterine wall.
2. Uterine connective tissue.
3. Maternal endothelium (wall of maternal blood capillaries).
Foetal components of placenta are:
1.Wall of foetal blood capillaries.
2. Foetal connective tissue.
3. Foetal chorionic epithelium

The chemical composition and pH of water are important to affect the animals.
Some animals can tolerate only a narrow range of salinity and are called stenohaline.
Some animals can tolerate a wide range of salinity and are called euryhaline.
Many freshwater fishes can not live for long in sea water and vice versa, because of the osmotic problems, they would face in such waters.
(b) (i) The leaves are reduced to spines.
(ii) The stem is green, flattened, spongy and takes over the function of photosynthesis .
(iii) A thick cuticle prevents loss of water.
(iv) They have a special photosynthetic mechanism (CAM), that enables their stomata to remain closed during day and open during night.
(c) Water is the most precious resource, use it judiciously and think of programs for its conservation.

Species-Area Relationship
1. Alexander Von Humboldt has observed that within a region, species richness increases with increased explored area, but only upto a limit.
2. The relationship between species richness and area for a number of taxa like angiospermic plants, freshwater fishes and birds is found to be a rectangular hyperbola.
3. On a log scale, the relationship becomes linear (straight line) and is described by the equation:
log S = log C + Z log A, where
S = Species Richness
Z = Slope of the line (regression coefficient)
A = Area and C = Y - intercept
4. Ecologists have found that the value of Z-line ranges between 0.1 and 0.2 irrespective of the taxonomic group of the region.
5. But in very large areas, like a continent, the Z value ranges between 0.6 and 1.2 and indicate species richness.

(a) Minisatellites and microsatellites
They are classified on the basis of:
(i) base composition, i.e. A- T rich or G-C rich.
(ii) length of the segment.
(iii) number of repetitive units.

(a) Round and yellow seeds
(b) Rr Yy

(d) 9 round, yellow seeded: 3 Round, green-seeded: 3 wrinkled, yellow seeded: 1 green, wrinkled - seeded
(e) Yellow-seeds: green seeds = 3 : 1 Round seeds: Wrinkled seeds = 3 : 1

(a) A develops into the embryo.
    B develops into the endosperm.
(b) - The endosperm development starts from the primary endosperm cell containing the primary endosperm nucleus.
- In the most common type of endosperm development, the primary endosperm nucleus undergoes successive free nuclear divisions to give rise to a number of free nuclei; at this stage, it is called free nuclear endosperm.
- Subsequently wall formation takes place from the periphery and proceeds towards the centre and the endosperm becomes cellular.
- This type of endosperm development is seen in coconut; the water of the tender coconut represents the free nuclear endosperm with thousands of nuclei in it and the white kernel around it represents the cellular endosperm.
- In albuminous seeds,some amount of endosperm persists in the mature seed, as the developing' embryo does not consume it fully, e.g. wheat/maize.
-In exalbuminous seeds, the endosperm is completely consumed by the developing embryo before seed maturation, e.g. groundnut and pea.
Development of primary endosperm nucleus:
- The PEN undergoes successive nuclear divisions to give rise to free nuclei, this stage of endosperm development is known as free-nuclear endosperm.
- Subsequently cell wall formation occurs and the endosperm becomes cellular .

The three events in sexual reproduction are:
(i) Pre-fertilisation events     (ii) Fertilisation and      (iii) Post-fertilisation events.
(i) Pre-fertilisation events:
The two major events in this phase are;
(a) Gametogenesis, the process of formation of gametes.     (b) Gamete transfer, i.e. pollination the process by which the pollen grains are deposited on the stigma.
(ii) Fertilisation:
1. It is called double fertilisation in angiosperms.
2. Each pollen grain produces two male gametes; one of them fuses with the female gamete to form zygote while the other fuses with the secondary nucleus to form primary endosperm nucleus.