Biology-organisation

• Most animals and plants consist of different types of cells organised as tissues, organs and systems
• The human respiratory system is a body system adapted for efficient gas exchange
• In multicellular organisms, the levels of organisation are: cells → tissues → organs → organ systems
• Organelle:

  • A specialised unit within a cell which performs a specific function
• Cell:

  • The basic building block of all living organisms
• Tissue:

  • A group of cells working together to perform a shared function, and often with similar structure
• Organ:

  • A structure made up of groups of different tissues, working together to perform specific functions
• Organ system:

  • A group of organs with related functions, working together to perform certain functions within the body
• Plant cells, tissues and organs are adapted to their functions
• The stem, root, and leaves form an organ system that transports substances into, around, and out of a plant
• Plant stems and roots have two types of transport systems: xylem and phloem
• Xylem vessels are narrow, hollow, dead tubes with lignin, responsible for the transport of water and minerals in plants
• Phloem transports sugars and amino acids dissolved in water
• In the root, xylem forms a central column for solid support, while phloem is towards the centre, outside the xylem
• In the stem, xylem and phloem are grouped into vascular bundles
• Plant leaves are the main organ of photosynthesis
• Leaves are adapted for gas exchange and photosynthesis
• Features of plant leaves:

  • Large surface area for maximum absorption of light and carbon dioxide
  • Thin, flattened blade for limited distance for water and gases to diffuse
  • Vascular tissue in midrib and veins to transport water, minerals, glucose, and other products of photosynthesis
  • Air spaces between cells within the leaf for the diffusion of gases
• pulmonary vein carries oxygenated blood from the lungs to the left atrium.
• aorta: the main artery of the body, supplying oxygenated blood to the circulatory system. In humans it passes over the heart from the left ventricle and runs down in front of the backbone.
• The liquid component of the blood is called plasma. All the blood cells are suspended in the plasma. It does not have a nucleus.
• Cancer is uncontrollable cell division. It can be caused by exposure to ionising radiation such as X-rays.
• Digestion is a process in which large insoluble food molecules are broken down into smaller, soluble molecules under the control of enzymes.
• Phloem is a specialised tissue found in a plant's roots, stems and leaves. It transports amino acids and sugars.
• What is the missing word in blank A?

  
• Protease enzymes break down proteins into amino acids. (The prefix "prot" refers to proteins and the suffix "ase" means it is an enzyme.)
• Water loss in a plant is affected by the temperature of the surrounding air. If the temperature is decreased, the rate of water loss is decreased and the movement of the air bubble along the glass tube will be slower.
• The plasma transports substances around the body but it does not transport oxygen.
• Carbon dioxide enters a plant from the surrounding atmosphere through diffusion.
• Mineral ions are transported dissolved in water.
• The lungs are organs which remove carbon dioxide from the body.
• Alveoli are found deep inside the lungs.
• The enzyme amylase is a carbohydrase. It breaks large starch molecules into smaller sugar molecules.
• A person who provides an organ for a recipient is referred to as an organ donor.
• The function of the red blood cells, erythrocytes, is to transport oxygen from the lungs to the rest of the body. Red blood cells contain haemoglobin which transports the oxygen.
• Most photosynthesis occurs in the palisade mesophyll layer of a leaf. This is located just below the epidermis.
• Enzymes are made of proteins.
• Deoxygenated blood is pumped to the lungs. Deoxygenated blood is blood that contains very little, if any, oxygen.
• Lipids are composed of fatty acids and glycerol, so the enzyme lipase breaks lipids into fatty acids and glycerol
• Arteries have thick muscular walls to withstand the high pressure of blood that flows through them. If their walls were thin, the high pressure of the blood might burst them.