Excretion and Circulatory System

Active absorption involves the uptake of water by plant cells using metabolic energy to move water against an osmotic gradient.

Gas exchange in tissues occurs via diffusion, which is driven by the difference in partial pressure or concentration of gases between the blood and the tissues.

The nephron is the microscopic structural and functional unit of the kidney responsible for filtering blood and forming urine.

Transpiration is the biological process where water is lost as vapor from the aerial parts of plants, primarily through the stomata.

Urea is the primary nitrogenous waste product excreted by humans, produced in the liver from ammonia.

The glomerulus is a network of small blood vessels (capillaries) located within the Bowman's capsule of the nephron. It is responsible for the filtration of blood during urine formation.

Unicellular organisms rely on simple physical processes to exchange materials with their environment. Diffusion allows gases and small molecules to move across the cell membrane along a concentration gradient.

Platelets, also known as thrombocytes, are cell fragments in the blood that aggregate at the site of a wound to form a clot. RBCs carry oxygen, and WBCs are primarily involved in immune defense.

When a blood vessel is damaged, platelets disintegrate and release thromboplastin. This substance initiates the clotting cascade by converting prothrombin to thrombin.

Fish have a single-circuit circulatory system where blood passes through the heart once per cycle. Their heart consists of one atrium and one ventricle, making it a two-chambered organ.

In the absence of oxygen, yeast performs fermentation. This process converts glucose into ethyl alcohol (ethanol), carbon dioxide, and a small amount of energy.

Arteries carry blood away from the heart under high pressure, necessitating thick, elastic walls to withstand the force. Veins have thinner walls and valves to prevent backflow.

Although nitrogen is abundant in the atmosphere, plants cannot absorb it directly as gas. They absorb nitrogen primarily in the form of nitrates or ammonium ions from the soil.

In vertebrates, hemoglobin is contained within red blood cells. However, in some invertebrates like the earthworm, hemoglobin is dissolved directly in the plasma.

The heart is enclosed in a double-walled sac known as the pericardium. Pleura covers the lungs, and meninges cover the brain.

The spleen is the largest organ of the lymphatic system. It acts as a filter for blood, recycling old red blood cells and storing platelets and white blood cells.

The pulmonary artery is the only artery that carries deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation.

In the human heart, the right atrium and right ventricle receive blood returning from the body, which is low in oxygen and high in carbon dioxide.

Lymph is essentially blood plasma that has leaked out of capillaries. It lacks red blood cells (which are too large to pass through vessel walls) but contains a higher concentration of certain white blood cells (lymphocytes).

The kidneys are the primary organs responsible for osmoregulation, which involves maintaining the balance of water and mineral ions in the blood.

In freshwater protozoa like Amoeba, the contractile vacuole collects excess water from the cytoplasm and expels it to prevent the cell from bursting.

Urochrome is a pigment derived from the breakdown of hemoglobin. It is responsible for the characteristic yellow color of urine.

The hypothalamus regulates water balance by signaling the pituitary gland to release antidiuretic hormone (ADH), which increases water reabsorption in the kidneys.

Dialysis is a medical procedure used to filter waste products and excess fluid from the blood when the kidneys are unable to perform this function.

Individuals with blood type AB are considered universal recipients because their red blood cells have both A and B antigens, meaning they do not produce antibodies against A or B blood types.