Exam Preparation: MCQ Questions for CBSE Class 12 Biology Half Yearly Exam 2028

In the realm of biology, a myriad of fascinating processes occur, ranging from genetic variation to the intricate workings of food webs. Let's delve into these topics and more.

Genetic variation plays a crucial role in the evolution of species. It can occur through mutation in cells or during gene flow from one population to another. This variation, while often random, can lead to differences that may provide an advantage in certain environments, thereby increasing the chances of survival.

Speaking of environments, it's important to note the concept of a carbon sink. Any environment that can store carbon and remove it from the atmosphere is considered a carbon sink. For instance, trees in rainforests, with their thin barks, broad leaves, and pointed tips, are excellent examples of carbon sinks due to their ability to absorb and store carbon dioxide.

However, deforestation, a practice that removes trees from the landscape, can lead to a decline in carbon sinks, contributing to increased carbon dioxide levels in the atmosphere.

Moving on to reproduction, it's essential to understand that it always involves the fusion of gametes, which can be carried out by both parents. In humans, the gamete mother cells, known as oocytes, are diploid and undergo meiotic divisions to produce four haploid cells, each containing half the number of chromosomes.

In a cross between a brown fur male and a white fur female mouse, both parents are heterozygous, meaning they carry both the genes for brown and white fur. This cross would result in offspring that are either brown or white, depending on which allele for fur colour is expressed.

In pea plants, the alleles coding for kernel color exhibit polygenic inheritance, meaning that more than one gene pair is involved in determining the trait. As a result, the F2 generation of a cross between pea plants having round green seeds (RRGG) and wrinkled yellow seeds (rrgg) would see 25% of eggs carrying both the round and green alleles.

Reproduction also plays a significant role in population health. An increase in infant mortality rate is an indicator of a reproductively unhealthy society, suggesting that efforts should be made to improve maternal and child health.

In the medical field, immuno-suppressants are administered to patients post-organ transplantation and to those suffering from auto-immune disorders to control the cell-mediated response. These drugs help prevent the body from rejecting the transplanted organ or attacking itself.

Lastly, let's touch on the topic of biodiversity. Biodiversity encompasses a wide range of life, from animals and microorganisms present in the intestine of an organism to cells from the same tissue in different organisms. It's important to preserve and protect this diversity to ensure the continued health and sustainability of our planet.

In conclusion, understanding these various biological processes—from genetics to reproduction and environment—provides us with a deeper appreciation for the intricate workings of life on Earth.

Exam Preparation: MCQ Questions for CBSE Class 12 Biology Half Yearly Exam 2028