In the context of human reproduction, the 'Placenta' is fully formed and functional by the end of which trimester of pregnancy? MCQ with Answer and Explanation
In the context of human reproduction, the 'Placenta' is fully formed and functional by the end of which trimester of pregnancy?
A. Second trimester (end of 24 weeks)
B. At the time of birth
C. First trimester (end of 12 weeks)
D. Third trimester (end of 36 weeks)
Answer: Option C
Solution (By JKSSB Mock Tests)
The placenta begins to form immediately after implantation of the blastocyst. By the end of the first trimester (around 12 weeks of gestation), the placenta is fully formed and takes over the primary role of hormone production (progesterone and estrogen) from the corpus luteum. It is fully functional in providing oxygen, nutrients, and waste removal for the developing fetus for the remainder of the pregnancy. It is not fully formed at conception, nor does it wait until the second or third trimester.
Explanation:
The common garden pea is scientifically named Pisum sativum. It belongs to the family Fabaceae. Mendel chose this plant for his genetic experiments because it has easily distinguishable contrasting traits, a short generation time, and is primarily self-pollinating. Cicer arietinum is chickpea, and Phaseolus vulgaris is the common bean.
Explanation:
The anther is the terminal part of the stamen (male reproductive organ) where pollen grains are produced through microsporogenesis. Stigma is the receptive surface for pollen, style connects stigma to ovary. Ovary contains ovules, which develop into seeds after fertilization. The anther has four microsporangia (pollen sacs).
Consider statements about environment: 1. The greenhouse effect is entirely unnatural. 2. Deforestation contributes to global warming. 3. Ozone depletion causes skin cancer. Which are correct?
Explanation:
The greenhouse effect is a natural process that keeps Earth warm; the problem is the enhanced greenhouse effect due to human activities. Deforestation reduces the number of trees absorbing CO2, increasing atmospheric greenhouse gases and contributing to global warming. Ozone layer depletion allows more harmful UV-B radiation to reach Earth, significantly increasing the risk of skin cancers. Thus, statements 2 and 3 are correct.
No comments yet. Be the first to start the discussion!