Each species has a characteristic chromosome number and most of their cells have a complete set of these chromosomes. However, in the life cycle of humans, only sperm and eggs have the number of chromosomes.

Strep throat is a bacterial infection caused by group A Streptococcus bacteria, specifically Streptococcus pyogenes. It is a common infection that affects the throat and tonsils, causing symptoms such as sore throat, fever, swollen lymph nodes, and difficulty swallowing. Strep throat is highly contagious and spreads through respiratory droplets when an infected person coughs or sneezes. It is typically treated with antibiotics to prevent complications and reduce the risk of spreading the infection to others. Other diseases caused by bacteria include tuberculosis, pneumonia, urinary tract infections, and bacterial meningitis.

The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid cycle, takes place in the mitochondrial matrix. Mitochondria are the powerhouses of the cell, responsible for generating ATP through aerobic respiration. The Krebs cycle is a key metabolic pathway occurring in the matrix of mitochondria, where acetyl-CoA molecules derived from the breakdown of carbohydrates, fats, and proteins are further oxidized to produce ATP, NADH, FADH2, and carbon dioxide. These energy-rich molecules serve as substrates for the electron transport chain, leading to the production of additional ATP molecules.

The aerodynamic nature of a bird's wing is an example of the central theme in biology known as "Structure and function." This theme emphasizes the relationship between the form and function of biological structures. In the case of a bird's wing, its structure, including its shape, size, and arrangement of feathers, is intricately related to its function, which is to provide lift and thrust for flight. The specific structure of the wing, such as the curvature of the airfoil shape, enables it to generate lift by creating a pressure differential between the upper and lower surfaces of the wing when air flows over it. Thus, the structure of the wing is adapted to its function of facilitating flight in birds.

The cell wall is the part of a plant cell that acts as a barrier and provides support to the cell. It is a rigid, protective structure located outside the cell membrane and is composed primarily of cellulose, a complex carbohydrate. The cell wall gives plant cells their characteristic shape and provides mechanical support, preventing the cell from bursting due to osmotic pressure. It also helps regulate the movement of water and solutes into and out of the cell and protects the cell from pathogens and mechanical damage. In addition to cellulose, the cell wall may contain other polysaccharides, proteins, and lignin, depending on the type of plant cell and its function.