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Science (English Medium) Class 12 - CBSE Important Questions

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Answer the following question.
Express the process of pollination in Vallisneria.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Pollination

Differentiate between geitonogamy and xenogamy (allogamy).

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Pollination

Answer the following question.
Write the difference in the characteristics of the progeny produced as a result of the two processes.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Pollination

Can a plant flowering in Mumbai be pollinated by pollen grains of the same species growing in New Delhi? Provide explanations to your answer.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Pollination

Answer the following question.
When a seed of orange is squeezed, many embryos, instead of one are observed. Explain how it is possible.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Polyembryony

Coelacanth was caught in South Africa. State the significance of the discovery of Coelacanth in the evolutionary history of vertebrates.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Pollination

Emasculation and bagging are the two important steps carried during artificial hybridization to obtain superior varieties of desired plants. Explain giving reasons, in which types of flowers and at what stages are the two processes carried out.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Artificial Hybridization or Artificial Fertilization

State what is apomixis. Write its significance. How can it be commercially used?

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Polyembryony
Draw an L.S. of pistil showing pollen tube entering into the embryo sac. Label the following:
  1. Nucellus
  2. Antipodals
  3. Synergids
  4. Micropyle
Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Pollination

Flowers which have single ovule in the ovary and are packed into inflorescence are usually pollinated by ______.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Pollination

Assertion: Apomictic embryos are genetically identical to the parent plant.

Reason: Apomixis is the production of seeds without fertilization.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Apomixis

Trace the development of a megaspore mother cell to the formation of a mature embryo sac in a flowering plant.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Development of Female Gametophyte or Embryo Sac

The wall layer of microsporangium, which nourishes the pollen grain, is ______.

Appears in 1 question paper
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Microsporogenesis

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

Appears in 1 question paper
Chapter: [2] Human Reproduction
Concept: Menstrual Cycle (Ovarian Cycle)

Describe the roles of pituitary and ovarian hormones during the menstrual cycle in a human female.

Appears in 1 question paper
Chapter: [2] Human Reproduction
Concept: Menstrual Cycle (Ovarian Cycle)

How is 'oogenesis' markedly different from 'spermatogenesis' with respect to the growth till puberty in the humans?

Appears in 1 question paper
Chapter: [2] Human Reproduction
Concept: Gametogenesis

Draw a sectional view of human ovary and label the different follicular stages, ovum and Corpus luteum.

Appears in 1 question paper
Chapter: [2] Human Reproduction
Concept: Gametogenesis

When and where do chorionic villi appear in humans?

Appears in 1 question paper
Chapter: [2] Human Reproduction
Concept: Pregnancy and Embryonic Development

Draw a diagrammatic sectional view of the female reproductive system of human and label the parts

(i) where the secondary oocytes develop

(ii) which helps in collection of ovum after ovulation

(iii) where fertilization occurs

(iv) where implantation of embryo occurs.

Appears in 1 question paper
Chapter: [2] Human Reproduction
Concept: The Female Reproductive System

Explain the role of pituitary and the ovarian hormones in menstrual cycle in human females

Appears in 1 question paper
Chapter: [2] Human Reproduction
Concept: Menstrual Cycle (Ovarian Cycle)
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