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TN 12th Computer Applications மின்னணு செலுத்தல் முறைகள் Sample Question Papers Study Material - QB365 Set A

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TN 12th Computer Applications மின் - வணிகம் Sample Question Papers Study Material - QB365 Set A

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TN 12th Computer Applications திறந்த மூல கருத்துருக்கள் Sample Question Papers Study Material - QB365 Set A

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12th Standard English Medium Biology (Botany) Subject Asexual and Sexual Reproduction in Plants Book Back 5 Mark Questions with Solution Part - I

Published on: 02/06/2021

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Std: 12th Standard - Biology

chapter: - Book back Questions

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Questions:

Generic 3

2 x 3 = 6

Distinguish tenuinucellate and crassinucellate ovules.

Write short note on Pollen kitt.

Generic 2

1 x 2 = 2

‘Pollination in Gymnosperms is different from Angiosperms’ – Give reasons.

Generic 5

2 x 5 = 10

Enumerate the characteristic features of Entomophilous flowers

Write short note on Heterostyly.

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Answers Key:

Generic 3

2 x 3 = 6

ovule is divided into two types based on the position of the sporogenous cell

Tenuinucellate type	Crassinucellate type
Sporogenous cell is hypodermal with a single layer of nucellar tissue around it.	Sporogenous cell is sub hypodermal
Have very small nucellus	Have fairly large nucellus.

Source	Contributed by the tapetum
Colour	Yellow or orange
Content	Carotenoids or flavonoids
Nature	Oily layer forming a thick viscous coating over pollen surface
Use	Attracts insects protects damage from UV radiation.

Generic 2

1 x 2 = 2

Gymnosperms - Pollination is said to be direct as the pollen are deposited directly on the exposed ovules Angiosperms - Pollination is said to be indirect as the pollen are deposited on the stigma of the pistil.

Generic 5

2 x 5 = 10

(i) Flower size Generally large
(ii) It small - aggregated to dense in florescence (eg) Asteraceae flower
(iii) Flower colour - brightly coloured
(iv) The adjacent parts of flower may also be brightly coloured (eg) Coloured bracts of Poinsettia, Bougainvillea
(v) Secretions - Scent, nectar
(vi) Flowers - if no secretion of nectar
(vii) Pollen - Consumed as food or used up to build hives
(viii) Production of foul odour - attracts flies and Beetles
(ix) Presence of juicy cells - juice sucked by insects.
(x) The above characteristic features of entomophilous flowers bring about successful pollination by insects.

(i) Some plants produce two or three different forms of flowers the length of stamen and style differ in them pollination will take place only between organs of same length.
(ii) So cross pollination is only possible. Distyly (eg) Primula-produces two forms of flowers.

Pin or long style	Thrum eyed or short style
Long stamen	Short stamen
Long stigmatic papillae	Small stigmatic papillae
Small pollen grains	Large pollen grains

(iii) Stigma of thrum eyed anther of the pin lie in same level, Anther of the thrum eyed stigma of the pin lie in same level.
(iv) So effective cross pollination occurs, Tristyly - (eg) Lythrum
(v) The plant produces three kinds of flowers having difference in length of stamen and style.
(vi) Pollen from flowers of one type pollinate only the other two types can but not their, own type.