CBSE 2023 · Region 1 · Set 2 · Q31 · 5 marks
(i)When and how does foetal ejection reflex begin ?(ii)Pituitary gland and uterine muscles play an important role during parturition. Explain.(iii)A functional mammary gland is a characteristic of all female mammals. Given below is a diagrammatic sectional view of a mammary gland. Identify the parts $\displaystyle 1$, $\displaystyle 2$ and $\displaystyle 3$, and mention one function of each of them.
(i)How are the characteristic features of pollen, anther and stigma of a maize plant suited for pollination by wind?(ii)How do you justify that:(1)Pollen grains are recovered from fossils?(2)Micropyle remains as a small pore in the seed coat of a fully developed seed?
(i)
When and how does foetal ejection reflex begin ?
(ii)
Pituitary gland and uterine muscles play an important role during parturition. Explain.
(iii)
A functional mammary gland is a characteristic of all female mammals. Given below is a diagrammatic sectional view of a mammary gland. Identify the parts $\displaystyle 1$, $\displaystyle 2$ and $\displaystyle 3$, and mention one function of each of them.
(i)
How are the characteristic features of pollen, anther and stigma of a maize plant suited for pollination by wind?
(ii)
How do you justify that:
(1)
Pollen grains are recovered from fossils?
(2)
Micropyle remains as a small pore in the seed coat of a fully developed seed?
Marking-scheme solution
(a) (i) • When foetus is fully mature/ after completion of gestation periods / after
completion of pregnancy
mild uterine contractions originate in response to the signal from a fully developed foetus and placenta
(ii) Foetal ejection reflex triggers a release of oxytocin from the maternal pituitary,
oxytocin acts on uterine muscles and causes contractions and expulsion of baby out of the uterus.(iii) $\displaystyle 1$- Mammary lobes, has clusters of cells called alveoli.
2 - Mammary alveolus, secrete milk.
$\displaystyle 3$-Lactiferous duct, through this milk is sucked out.
OR
(b) (i) • Pollen- light / non-sticky, to travel easily through air
// produce in enormous amount, to compensate the wastage during pollination
• Anther – well exposed, pollen easily dispersed into wind current
• Stigma – Large / often feathery, to easily trap air-borne pollen grains
(ii) ($\displaystyle 1$) Pollen grains have hard outer layer exine made up of sporopollenin, which is one of the most resistant organic material known / no enzyme can degrade sporopollenin.
($\displaystyle 2$) It allows the entry of water, oxygen into the seed at the time of germination.
Human ReproductionParturition and LactationUnderstandlong_answerhard
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CBSE Class 12 Biology past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.