CELL ORGANISATIONBy the end of this lesson, you should be able to: 1. State the necessity for cell specialisation in multicellular organisms 2. Describe cell specialisation in multicellular organisms 3. Describe cell organisation in the formation of tissues, organs and systems in multicellular organisms.
Organisms are divided to two types:1. Unicellular organism- single cell organism (Amoeba sp. and Paramecium sp.) 2. Multicellular organism- larger organism with more than one cell.
Each cell is one organism for unicellular org. and its able to carry out all the function of life independently. The larger org. (multicellular org) need many different of cell to carry out all the different function of life. Each cell has to change in shape and structure during cell specialisation to become specific cells in order to perform different function.
Living Process in Unicellular Organisms Unicellular org. are small and simple org. consisting one cell each. Each cell or org is a complete unit of life; able to carry out all the living processes to survive. Amoeba sp. and Paramecium sp. are the example of unicellular org.
1. Amoeba sp. live in water, including water in the soil. It has no fixed shape since its shape change as its move.a) Movement: by extending temporary pseudopodia (false feet) and anchoring the tips on the ground. The rest of the cytoplasm slowly flows into this extension, hence moving the org. along. Reproduction: Amoeba reproduce by binary fission, its nucleus divides to form two daughter nuclei and cytoplasm then divides to form two daughter of amoeba. under adverse condition (drought) amoeba form spores.
c) Feeding: Feeds by process called phagocytosis. Use pseudopodia to engulf the food. Pseudopodia enclosed the food particle and packaged in a food vacuole. food particle fuses with lysosome and will digest by enzyme (lysozyme). The exchange of gases, nutrients and waste substances occur through plasma membrane by diffusion. Water diffuses into cell by osmosis and fill contractile vacuole.
Cell specialisation in multicellular organisms. Multicellular org are more complex than unicellular org. Example: hydra, spirogyra, ferns, other plants, human beings. The larger org need many different types of cell to carry out their life processes. This achieved through cell specialisation and cell organisation.
Cell specialisation Each type of cell is different in size, shape, and structure. Each cell is not capable of performing all the life processes such as respiration, digestion and secretion. So, multicellular org. need a cell specialisation to enable them to perform different functions.
This is achieved through differentiation process (cell begin to change in shape and structure as they grow) The cells acquire special structures and become specialised cells. Each type of cell performs only one specific function. Known as division of labour. Through cell specialisation and division of labour, different functions in the body can be performed at the same time. All the life process can be carry out smoothly and efficiently.
Cell Organisation Organisation of cell allow every part of a multicellular org to perform various functions efficiently. Each part of a multicellular org is organised on the basis of:cell tissues organ system organism
Cells are the basic units of life in all org. Cells of the same type which carry out a common function are organised into tissues. Tissues is a group of similar cells performing a particular function. Different type of tissues group together to form an organ. Organ is a group of tissues that performs a specialised function. Several organs are found within a system.
Cell Organisation in Animala) Tissues: Different types of tissue have different structure that are suited to their functions. Four main types of animal tissue; epithelial tissue, nervous tissue, muscle tissue and connective tissue.
1. Epithelial tissue Consist of epithelial cells arranged in a continuous layer. Cover body surface (exterior) or line the cavities within the body. Protect the underlying cells from mechanical injury. Act to absorb food and water by diffusion. Form secretory glands which produce secretions. Example: surface of skin, lining of stomach, small intestine, trachea and lungs.
2. Muscle tissue: Consist of muscle cells which can contract to perform work. Most abundant tissue in body. Cause body movement by means contraction. Three types of muscle tissue: smooth muscle, skeletal muscle and cardiac muscle. Example: smooth muscle (intestine, blood vessels, urinary and reproductive tracts), skeletal muscle (in arms and legs- attached to the bones), cardiac muscle (wall of heart)
Contraction and relaxation of smooth muscle are responsible for involuntary body activities (peristaltic movement ) Skeletal muscle involve for voluntary movement. Its contract and relax to move the bones. Cardiac muscles contract to pump the blood to the body. The contraction is involuntary.
3. Nerve tissue: Consist of nerve cells called neurones. Each neuron consist of cell body and nerve fibres called dendrites and axons. Send and receive impulses to coordinate the activities of the body. Found in the brain and spinal cord Example: afferent neurone, efferent neurone, interneurone.
4. Connective tissue: Consist of elastic and non-elastic fibres. Join together body structures, as well as protect, hold and support the cell in the body. Can store and transport materials. Loose connective tissue- bind epithelia to underlying tissues and holds organ in place. Dense fibrous connective tissue- contain collagenous fibres packed closely together. Found in tendons (connect muscles to bones) and ligaments (join bones together at joints)
Cartilage- strong and flexible connective tissue. Provide support to nose, ears and covers the end of bones at joints. Also form the disc between vertebrae (act as cushions to absorb pressure) Bone- consist of cells embedded in a matrix of collagen which are hardened by mineral deposits such as calcium. Provides protection to organ and support the body.
Blood cells- produced in bone marrow. Adipose tissue- tightly packed cells that stores fat. Found in the dermis of the skin and around the major organ. Act as energy reserve and provide insulation and protection.
b) Organs: Is formed by two or more types of tissues working together to perform particular function. Example: heart, stomach, skin, kidneys and lungs. Skin covers the body. Act as barrier against infection and water loss. Skin composed of two main layers: epidermis and dermis. Epidermis- outer layer of skin (made up of epithelial tissue)
Dermis- composed of connective tissue, nerve tissue, epithelial tissue and muscle tissue. Blood is supplied to the skin through a network of blood capillaries. Various sensory nerve endings are scattered throughout the dermis and epidermis. These nerve endings act as receptorstransmit nerve impulses for pressure, temperature, touch and pain.
Specialised epithelial cells in the skin form structures such as hair follicles- produce hair, sweat glands (secrete sweat), oil glands (secrete sebum onto the skin surface)
c) System: Several organs which work together to carry out a specific function called organ system. The human body has 11 major system which carry out major body functions. Integumentary system, muscular system, circulatory system, endocrine system, lymphatic system, nervous system, digestive system, skeletal system, excretory system, respiratory system and reproductive system.
Endocrine system Circulatory system
Digestive system Lymphatic system
Female reproductive system
Male reproductive system