O1- There is a hierarchical structure within multicellular organisms.

Organisation OVERVIEW…… When cells of the same type are assembled together they form a tissue. When different tissues are assembled to perform a particular task they form organs which, in turn make up systems. A group of systems makes it possible for an organism to perform the functions necessary for life. An organism may be defined as a collection of cells, tissues, organs and systems that are capable of independent existence and reproduction.

Organisation

Organisation O1.1 – Give examples of cells with identical genetic information that differentiate to produce cells with specialised structures and functions. All cells of an organism are genetically identical as they are all derived from the zygote (fertilised egg). As the organism grows the cells divide by mitosis and differentiate to become different cells with their own structure and function. In each differentiated (specialised) cell only a small number of genes that code for the specialised function/structure ‘active’ or ‘switched on’ (transcribed and translated).

Organisation Other genes, not required are inactive. As an embryo develops, the position of the cell determines which genes will be active and which will be inactive, therefore the specialisation of the cell. Once a cell has specialised it cannot transform into another type.

Organisation Examples of specialised cells in humans: Muscle Cells – elongated with an abundance of filaments that permit the cells to elongate and contract. Red blood cells – small bi-concave shaped cells packed with haemoglobin to transport oxygen.

Organisation Examples of specialised cells in plants: Palisade Cells – in the leaf of a plant with a rectangular shape packed with chloroplasts for photosynthesis. Guard cells – in the lower parts of leaves with a specialised shape controlling the opening and closing of the stomatal pore.

Organisation Activities: Essentials Textbook: Read pg. 112 – 113 https://www.youtube.com/watch?v=m0pf5k3q8zk Activities: Essentials Textbook: Read pg. 112 – 113 Complete Focus Questions 1 – 4 (pg. 113)

Organisation O1.2 – Give examples of cells of like form and function that aggregate as tissue. A tissue is a collection of similar cells grouped together to perform a specific function. These cells may be held together by a sticky substance or by a fabric of extracellular fibres. There are four basic types of tissues in humans:

Organisation Epithelial Tissue: Tightly packed cells that cover and protect the inside and outside surfaces of the body. The different types of epithelial cells are named according to their shape:

Organisation Connective Tissue: Supports or binds other cells and tissues together. The tissue consists of a sparse population of cells scattered through the extracellular matrix.

Organisation Muscle Tissue: Contains cells that contract and relax allowing for movement. This movement is due to the extensive cytoskeleton in these cells consisting of contractile protein filaments (actin and myosin).

Organisation Nervous Tissue: Is able to detect stimuli and transmit messages from one part of the body to another in the form of tiny electrical currents.

Organisation Activities: Essentials Textbook: Read pg. 113 – 114 Complete Focus Questions 1 – 2 (pg. 114)

Organisation O1.3 – Give examples of organs that contain several types of tissue. Organs are discrete structures composed of several types of tissue, that perform specific tasks. Example – The stomach

Organisation Other important organs in the human body: Organ Main tissues Function Heart Muscle, nerve and blood Muscular pump to move blood to all parts of the body. Brain Blood, nerve Detection, processing and transmission of information as nerve impulses. Liver Connective, blood Metabolism of waste materials, production of bile and urea and storage of glycogen.

Organisation Some important organs in plants:

Organisation Some important organs in plants: Organ Main tissues Function Root Epidermal, vascular Absorption of water and nutrients, anchorage. Stem Epidermal, vascular, parenchyma Transport of materials to and from the roots, support. Leaf Epidermal, mesophyll, vascular Production of carbohydrates by photosynthesis.

Organisation O1.4 – List the organ systems that constitute the human body. An organ system is a group of organs that coordinate to carry out a specific function.

Organisation

Organisation Activities: Essentials Textbook: Read pg. 115 – 116 Complete Focus Questions 1 – 2 (pg. 116) Essentials Workbook: Worksheet 22 ~ Organisation of multi-cellular organisms