(a) Explain the post-pollination events leading to seed production in angiosperms.
(b) List the different types of pollination depending upon the source of pollen grains.
(a) Pollination is the process of transfer of pollen grains from the anther to stigma.
i. When the pollen grains fall on the stigma, the pollen tube enters one of the synergids and releases two male gametes.
ii. One of the male gametes moves towards the egg cell and fuses with it to form zygote.
iii. The other male gamete fuses with the two polar nuclei and forms the primary endosperm nucleus. This is termed as triple fusion.
iv. After the triple fusion, the central cell becomes the primary endosperm cell (PEC). The primary endosperm nucleus gives rise to endosperm, while the zygote develops into an embryo.
v. Seeds are the fertilised ovules that are developed inside a fruit.
vi. The integuments of ovules harden to form the seed coat, and the micropyle facilitates the entry of oxygen and water into the seed.
b) Depending on the source of pollen grains, pollination can be divided as follows:
i. Autogamy - When the pollen grains are transferred from anther to stigma of the same flower. Autogamy requires the anther and the stigma to in lie close proximity and also requires synchrony between the pollen release and the stigma receptivity. For example - plants like Viola and Oxalis produce two kinds of flowers: Chasmogamous flowers (with exposed anther and stigma) and cleistogamous flowers (plants that do not open at all and in which only autogamy occurs).
Geitonogamy - It is the transfer of pollen grains from the anther of one flower to the stigma of another flower on the same plant. Genetically, it is similar to autogamy, but it requires pollinating agents like winds, water or insects.
Xenogamy - It is the transfer of pollen grains from the anther to the stigma of a different plant.
(a) Name any two places where it is essential to install electrostatic percipitators. Why is it required to do so?
(b) Mention one limitation of the electrostatic precipitator.
(a) How are the following formed and involved in DNA packaging in a nucleus of a cell?
(b) Differentiate between Euchromatin and Heterochromatin
(a) Why should we conserve biodiversity? How can we do it?
(b) Explain the importance of biodiversity hot-spots and sacred groves.
Prior to a sports event blood and urine samples of sports-persons are collected for drug tests.
(a) Why is there a need to conduct such tests/
(b) Name the drugs the authorities usually look for.
(c) Write the generic names of two plants from which these drugs are obtained.
Describe the experiment that helped demonstrate the semi-conservative mode of DNA replication
Reproductive and Child Healthcare (RCH) programmes are currently in operation. One of the major tasks of these programmes is to create awareness amongst people about the wide range of reproduction related aspects. As this is important and essential for building a reproductively healthy society.
(a) Providing sex education in schools in one of the ways to meet this goal. Give four points in support of your opinion regarding this statement.
(b) List any two 'indicators' that indicate a reproductively healthy society.
(a) Briefly explain the events of fertilisation and implantation in an adult human female.
(b) Comment on the role of placenta as an endocrine gland.
Given below is a list of six micro-organism. State their usefulness to humans.
(a) Nucleopolyhedrovirus
(b) Saccharomyces cervisiae
(c) Monascus purpureus
(d) Trichoderma polysporum
(e) Peniciliu notatum.
(f) Propionibacterium sharmanni
(a) Represent diagrammatically three kinds of age-pyramids for the human population.
(b) How does an age pyramid for human population at given point of time helps the policy makers in planning for the future.
