Name the three events in the sexual reproduction of an angiosperm and mention what major events occur in each of them.

Explain the development of the zygote into an embryo and of the primary endosperm nucleus into an endosperm in a fertilised embryo sac of a dicot plant. 

Puneet used to like beautiful flowers but not the insects flying in the garden.He discussed his plan but his father advised him not to do so as it will affect seed formation in ornamental plants of the garden.
Read the above passage and answer the following questions:
(i) Was the decision of Puneet to kill insects of garden with insecticide right?
(ii) Why did his father advise him not to do so?
(iii) Are chemical insecticides safe for living organisms including human beings?

Give the structure of simple type placenta.

Let us assume in a given plant, the genotype symbol 'Y' stands for dominant yellow seed colour and 'Y' for recessive green seed colour; symbol 'R' for round seed shape and 'r' for wrinkled seeds.  Two homozygous parents (plant) with genotypes 'RRYY' and 'rryy' are crossed and their F₁ generation progeny is then 
(a) Phenotype of F₁ progeny
(b) Genotype of F₁ Progeny
(c) Gamete genotypes of F₁ progeny
(d) Phenotypic ratio of F₂ population
(e) Phenotypic ratio of yellow seeds to green seeds and round seeds to wrinkled seeds in F₂ population.

(a)Name two types of satellite DNA.Mention the basis for such a classification.
(ii)Show only diagrammatically the process of transcription in bacteria

Write the causative organism, mode of infection, symptoms and preventive measures of
(1) Leprosy
(2) Whooping cough

Water is the most important factor influencing the life of organisms.  Life on earth originated in water and cannot be sustained without water.  Organisms living in water bodies (ocean, lake, river, etc.) also face water-related problems.
(a) How are aquatic animals affected by the quality of water? Explain.
(b) Mention any four adaptations the desert plants have, to live there successfully.
(c) Represent the value learnt.

Describe in detail the species-area relationship of biodiversity

Why is ozone layer in stratosphere called a protective layer?