Science: Class 7 — Chapter 7: Transportation in Animals and Plants

7.1 Circulatory System

Blood: A fluid that flows in blood vessels, transporting digested food, oxygen, and waste products.
Plasma: The fluid part of the blood in which various cells are suspended.
Red Blood Cells (RBC): Cells containing haemoglobin, a red pigment that binds with oxygen and transports it throughout the body.
White Blood Cells (WBC): Cells that fight against germs and infections entering the body.
Platelets: Specialized blood cells responsible for blood clotting to stop bleeding.

Arteries: Thick-walled, elastic vessels that carry oxygen-rich blood away from the heart at high pressure.
Veins: Thin-walled vessels with valves that carry carbon dioxide-rich blood back to the heart. Valves prevent backflow.
Pulse: The throbbing movement felt in arteries due to blood flow. A resting adult has a pulse rate of 72 to 80 beats per minute.
Capillaries: Extremely thin tubes that connect arteries to veins, allowing exchange of substances with tissues.
Pulmonary Artery: Carries carbon dioxide-rich blood from the heart to the lungs (exception to typical arteries).
Pulmonary Vein: Carries oxygen-rich blood from the lungs to the heart (exception to typical veins).

Heart: A muscular organ, roughly the size of a fist, located in the chest cavity, acting as a continuous pump.
Chambers: Divided into four chambers to prevent mixing of oxygen-rich and carbon dioxide-rich blood: two upper atria and two lower ventricles.
Heartbeat: The rhythmic contraction and relaxation of heart muscles, measured using a stethoscope.

7.2 Excretion in Animals

Excretion: The process of removing toxic waste products produced in cells from the body.
Kidneys: Two organs that filter blood to remove waste products in the form of urine.
Ureters: Tube-like structures that carry urine from the kidneys to the bladder.
Urinary Bladder: A muscular sac that stores urine until it is passed out.
Urethra: The muscular tube through which urine is eliminated from the body.
Urine Composition: Typically consists of 95% water, 2.5% urea, and 2.5% other waste products.
Dialysis: An artificial blood-filtering process used when a person's kidneys fail.

Aquatic Animals (e.g., Fish): Excrete cell waste as ammonia, which dissolves directly in water.
Land Animals (e.g., Birds, Lizards, Snakes): Excrete a semi-solid, white compound called uric acid.
Humans: Primarily excrete urea.
Sweat: Contains water and salts; helps in removing waste and cooling the body.

7.3 Transport of Substances in Plants

Root Hairs: Increase the surface area of roots for absorbing water and mineral nutrients from the soil.
Xylem: Vascular tissue forming a continuous network of channels to transport water and nutrients from roots to leaves.
Phloem: Vascular tissue responsible for transporting food prepared by leaves to all parts of the plant.

Transpiration: The evaporation of water through stomata on leaf surfaces.
Suction Pull: Generated by transpiration, pulling water to great heights in tall trees. Also helps in cooling the plant.