Menstrual Cycle

Yes, understanding the menstrual cycle helps in: Identifying the fertile window for conception or avoiding pregnancy. Monitoring reproductive health and detecting irregularities.

Implantation should occur during the luteal phase (days 15–28) of the menstrual cycle. Reason: The uterine lining (endometrium) is thick and vascularised during the luteal phase, providing optimal conditions for embryo implantation and development.

Hormones: Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH). Source organ: Anterior pituitary gland.

Human activities responsible for accelerated species extinction include: Habitat destruction: Clearing forests for agriculture, urbanisation, and infrastructure development destroys natural habitats, leading to the loss of biodiversity. Overexploitation: Overhunting, overfishing, and overharvesting of natural resources deplete populations of species beyond recovery. Pollution: Release of pollutants into the air, water, and soil disrupts ecosystems, making them uninhabitable for many species.

Step 1: Analyzing the assertion:
- The corpus luteum is a temporary endocrine structure in the ovaries that forms after ovulation.
- It secretes the hormone progesterone, which is essential for the regulation of the menstrual cycle and for the maintenance of the endometrium during pregnancy.
Step 2: Analyzing the reason:
- Progesterone is indeed necessary for the maintenance of the endometrium. It prepares the uterine lining for possible implantation of a fertilized egg and helps in maintaining the lining during early pregnancy.
Step 3: Conclusion:
- Both Assertion (A) and Reason (R) are true, and the reason provides the correct explanation for the assertion. Thus, the correct answer is option (A).