Biology MCQs

Notes:

• Octopus: Octopuses belong to the class Cephalopoda within Phylum Molluska. Cephalopoda is a group of highly evolved, predatory marine animals. While they share some common ancestors with mollusks, they have distinct characteristics such as a complex nervous system, a beak-like mouth, and tentacles equipped with suckers.
• Snail: Snails are indeed mollusks. They are part of the class Gastropoda within the phylum Mollusca. Snails have a coiled shell and a soft body.
• Oyster: Oysters are also mollusks. They belong to the class Bivalvia within the phylum Mollusca. Oysters are characterized by their two hinged shells and are known for their filter-feeding lifestyle.
• Starfish: Starfish, also known as sea stars, are not mollusks. They belong to the phylum Echinodermata, and they have a completely different body plan and structure compared to mollusks. Starfish have radial symmetry and a unique water vascular system that helps them move and feed.

Notes:
As cells develop some genes are turned off permanently. All of the cells within a complex multicellular organism such as a human being contain the same DNA; however, the body of such an organism is clearly composed of many different types of cells. What, then, makes a liver cell different from a skin or muscle cell? The answer lies in the way each cell deploys its genome. In other words, the particular combination of genes that are turned on (expressed) or turned off (repressed) dictates cellular morphology (shape) and function. This process of gene expression is regulated by cues from both within and outside cells, and the interplay between these cues and the genome affects essentially all processes that occur during embryonic development and adult life. This means that cells become specialized because the genes that are not required are switched off. Only the genes needed to make a particular type of cell work are switched on. So muscle cells only have the genes needed to make muscle cell proteins switched on. All the other genes, such as those needed to make blood cell proteins and nerve cell proteins, are switched off. But the stem cells are unspecialized and can develop into various tissues.

Notes:
Centrosome is an organelle that serves as the main microtubule organizing centre (MTOC). Basal granules are cellular organelles that are similar to the centriole in structure and are found at the base of a cilium or flagellum.

Notes:
Dermatogen is the outer primary meristem of a plant or plant part that according to the histogen theory gives rise to epidermis, which is the outermost layer of the skin. Epidermis provides barrier to infection from environmental pathogens.

Notes:
R.H. Whittaker proposed an elaborated five kingdom classification. He was the first to propose the five-kingdom of organisms taxonomic classification of the world’s biota into the Animalia, Plantae, Fungi, Protista, and Monera in 1969. He also proposed the Whittaker Biome Classification, which categorized biome-types upon two abiotic factors: temperature and precipitation.

Notes:
Human skin can make large amounts of vitamin D when lots of skin is exposed and the sun is high in the sky. Your body is designed to get the vitamin D it needs by producing it when your bare skin is exposed to sunlight.

Notes:
Ethnobotany is the study of the plants of an area and their practical uses through the traditional knowledge of a local culture and people.

Notes:
The plasma membrane is mainly composed of fatty-acid-based lipids and proteins. Robert Hooke discovered the plasma membrane.

Notes:
The Process by which ammonia is converted into nitrate is called Nitrification. It can be done in two steps that involve Nitrite formation and Nitrate formation.

Notes:
Hepadnavirus B (hepatitis B virus, HBV) belongs to the genus Orthohepadnavirus of the Hepadnaviridae family. It is an important cause of viral hepatitis in humans worldwide.