HOLIDAYS HOMEWORK

STD: XII

SUB : BIOLOGY

  1. ANSWER THE FOLLOWING QUESTIONS

SEC A

  1. Name the part of the flower which the tassels of the corn cob represent.
  2. Name an IUD that you would recommend to promote the cervix hostility to the sperms.
  3. State one reason why breast feeding the baby acts as a natural contraceptive for the mother.
  4. Why are the testes located outside the abdominal cavity? Name the pouch in which they are present.
  5. Where does fertilizationandimplantation occurin human?
  6. Name the vegetative propagules in the following: a) Agave b) Bryophyllum
  7. Give an example of a plant which came in to India as a contaminant and is a cause of pollen allergy.
  8. Coconut palm is monoecious ,while date palm is dioecious. Why are they called so?
  9. Name all the haploid cells present in an unfertilized mature embryo sac of a flowering plant .write the total number of cells in it.
  10. Why are some seeds of citrus referred to as polyembryonic ?how are they formed?
  11. Why apple is refered to as a false fruit? Name the part in it which develops in to fruit .

SEC B

  1. A single pea plant in your kitchen garden produces pods with viable seeds, but the individual papaya plant does not. Explain(2016)
  2. Banana crop is cultivated by farmers without sowing of seeds .Explain how the plant is propagated.
  3. Describe the structure of the cells that guide the pollen tube to enter the embryo sac.
  4. Explain the events that occur during fertilization of an ovum in humans. How is it that only one sperm enters the ovum?
  5. Make a list of any three outbreeding devices that flowering plants have developed and explain how they help to encourage cross pollination.
  6. A couple where both husband and wife are producing functional gametes ,but the wife is still unable to conceive , is seeking medical aid. Describe the method s you can suggest to this couple to become happy parents.
  7. Write the location and functions in human testes: Sertoli cells , leydig cells
  8. What is ‘Terror of Bengal’ ? Why is it called so?
  9. Why do algae and fungi shift to sexual mode of reproduction just before the onset of adverse conditions?
  10. An anther with malfunctioning tapetum often fail to produce viable male gametophytes . Give one reason.
  11. List the adaptive features of water pollinated flowers like Vallisneria.
  12. Where is acrosome present in humans ?write its functions.
  13. Placenta act as an endocrine gland . explain
  14. Where do the signals for parturition originate from in humans?

SEC C

  1. a) Name the organic material exine of the pollen grain is made up of. How is this material advantageous to pollen grain? (2016)

b)Still it is observed that it does not form a continuous layer around pollen grain .give reason

c)How are the ‘pollen banks ‘useful?.

  1. a) mention the problems that are taken care by Reproduction and child Health Care programme

b) What is amniocentesis and why there is a statuatory ban on it.(2016)

  1. a) how is apomixis different from parthenocarpy?

b) describe any two modes by which apomictic seeds can be produced.

  1. Differentiate between XenogamyGeitonogamy , Oviparous and viviparous organisms , Parthenogenesis and parthenocarpy
  2. Name the two end products of double fertilization in angiosperms .how are they formed ? write their fate during the development of seed.
  3. A) maturesess of legumes are non albuminous .then , can it be assumed that double fertilization does not occur in legumes. Explain your answer.

b) list the differences between the embryos of dicot(pea) and monocot(grass family).

  1. Why are angiosperm anthers called dithecous? Describe the structure of its microsporangium.
  2. What is corpus luteum ?write its functions ? when does it degenerate? Explain the consequences of its degeneration in human females.
  3. When and where does chorionic villi appear in humans ? State its function.
  4. A woman has certain queries as listed below ,before starting with contraceptives pills. Answer them.

a)What do contraceptive pills contain and how do they act as contraceptives?

b)What schedule should be followed for taking these pills?

SEC D

  1. a) Explain the menstrual phase in a human female .state the levels of ovarian and pituitary hormones during this phase.

b) Why is follicular phase in the menstrual also reffered as proliferative phase ? Explain.

c) Draw a graffian follicle and label antrum and secondary oocyte. (2016)

  1. a) As a senior biology student you have been asked to demonstrate to the students of secondary level in your school, the procedure(s) that shall ensure cross pollination in a hermaphrodite flower. List the different steps that you would suggest and provide reasons for each one of them.

b) Draw a diagram of a section of a megasporangium of an angiosperm and label funiculus ,micropyle , embryo sac and nucellus.(2016).

  1. Angiosperm flowers may be monoecious, cliestogamous or show self-incompatibility .describe the characteristic features of each one of them and state which one of these flowers promote inbreeding and outbreeding respectively.
  2. A) How does cleistogamy ensure autogamy ?

b)State one advantage and one disadvantage of cleistogamy to the plants.

  1. Practice the following diagrams in drawing copy:

Human Male and female reproductive organs, T.S of ovary , Testes, ovum, human sperm, ovarian follicle, blastocyst,humanfoetus within the uterus, transport of ovum and passage of growing embryo , flow chart of spermatogenesis , oogenesis ,hormonal control of male and female rep. system

  1. Revise unit I for unit test