Life Processes

Step 1: Humans need more energy to maintain activities and body temperature. Step 2: Separate blood flow gives cells more oxygenated blood. Step 3: This supports efficient aerobic respiration.

Step 1: Blood first goes to lungs to receive oxygen. Step 2: Then oxygenated blood goes to the body through a separate route. Step 3: Separate circulation gives efficient oxygen supply to the body.

Step 1: Arteries carry blood pumped forcefully from the heart. Step 2: Their walls are thick and elastic. Step 3: Veins return blood at low pressure so valves prevent backflow.

Step 1: Substances must pass between cells and blood. Step 2: Thin walls make this exchange easier. Step 3: Therefore capillaries are suitable exchange sites.

Step 1: Some fluid from blood moves between tissues. Step 2: This extra fluid must be returned. Step 3: Lymph helps return it to blood circulation.

Step 1: In humans the heart pumps blood. Step 2: In plants root pressure and transpiration pull help raise water. Step 3: Therefore the driving forces of both transport systems are different.

Step 1: Leaves can be the source of food. Step 2: Roots fruits and growing parts can be use or storage sites. Step 3: This translocation needs energy.

Step 1: Undigested food leaves as faeces after digestion. Step 2: Metabolic wastes are produced by cell activities. Step 3: Removing these wastes is excretion.

Step 1: During filtration some useful substances and water may filter with wastes. Step 2: The body cannot afford to lose all of them. Step 3: Reabsorption helps return them to blood.

Step 1: Kidneys normally filter blood. Step 2: If kidneys fail wastes can collect in blood. Step 3: Dialysis helps clean blood artificially.

Step 1: Plants do not have kidneys like animals. Step 2: They can store some wastes in leaves bark resins or gums. Step 3: When old parts fall some wastes are removed too.

Step 1: Nutrition provides food to the body. Step 2: Energy remains stored in food. Step 3: Respiration releases that energy for cellular use.

Step 1: In photosynthesis food is made from carbon dioxide and water. Step 2: In respiration food breaks down to release energy and carbon dioxide may form. Step 3: Thus both are linked in flow of materials and energy.

Step 1: In large organisms many cells are deep inside the body. Step 2: Diffusion is slow over long distances. Step 3: Therefore a transport system is needed.

Step 1: Unicellular organisms are made of one cell. Step 2: The whole cell can exchange materials with the environment. Step 3: Therefore simple diffusion can be more useful for them.

Step 1: Oxygen enters blood in alveoli. Step 2: Blood carries oxygen to cells with help of haemoglobin. Step 3: Cells use that oxygen for aerobic respiration.

Step 1: Carbon dioxide forms during cellular respiration. Step 2: Blood carries it to lungs for removal. Step 3: If it accumulates it can affect body balance.

Step 1: Digestion changes food into simple substances. Step 2: Absorption brings them into blood. Step 3: Blood carries them to distant cells.

Step 1: Food is digested after eating. Step 2: Digested substances should enter blood from the small intestine. Step 3: Without absorption cells will not receive energy source.

Step 1: Organisms obtain or make food. Step 2: Food comes into a usable form. Step 3: Respiration releases energy from food.