Science
(a) Differentiate between self-pollination and cross-pollination.
(b) Identify A, B and C in the diagram given below and write one function of each.
Answer
(a)
| Self-pollination | Cross-pollination |
|---|---|
| Transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant. | Transfer of pollen grains from the anther of one flower to the stigma of a flower on another plant of the same species. |
| No genetic variation; offspring are identical to parent. | Produces genetic variation; offspring show new traits. |
| No external agents are needed. | Requires agents like wind, water, or insects. |
(b) Identification and functions of parts (A, B, and C) :
A – Stigma
Function : It receives pollen grains during pollination.B – Pollen tube
Function : It carries male gametes (sperm nuclei) from pollen grain to the ovule for fertilisation.C – Female gamete (egg or ovum)
Function : It fuses with the male gamete during fertilisation to form the zygote, which develops into a seed.
Related Questions
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- is heated at 443 K in excess conc. H2SO4.
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(a) Write the functions of the following parts of human female reproductive system :
- Ovary
- Fallopian tube
- Uterus
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(a) The power of a lens 'X' is -2·5 D. Name the lens and determine its focal length in cm. For which eye defect of vision will an optician prescribe this type of lens as a corrective lens ?
(b) "The value of magnification 'm' for a lens is -2." Using new Cartesian Sign Convention and considering that an object is placed at a distance of 20 cm from the optical centre of this lens, state :
- the nature of the image formed;
- size of the image compared to the size of the object;
- position of the image, and
- sign of the height of the image.
(c) The numerical values of the focal lengths of two lenses A and B are 10 cm and 20 cm respectively. Which one of the two will show higher degree of convergence/divergence? Give reason to justify your answer.
(a) Draw a ray diagram to show the refraction of a ray of light through a rectangular glass slab when it falls obliquely from air into glass.
(b) State Snell’s law of refraction of light.
(c) Differentiate between the virtual images formed by a convex lens and a concave lens on the basis of :
- object distance, and
- magnification