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Transcript
Cells – division of labour Recap: Unicellular organisms • • Amoeba – Single cell organism The same cell has to.. Take in food Excrete waste Move Grow Reproduce This is not the case for multi-cellular organisms! Multicellular organisms • Different functions required to maintain life processes are performed by different types of cells • 200+ types of cells in a human body • Cells have different shapes and structures suited for their job Specialisation – division of labour – More efficient and effective – Multitasking! – Disadvantages? “Blank” cells? • Some cells are “blank” because they do not have particular functions yet, but can later change into nearly any type of body cells Stem cells – Found in embryos, umbilical cord blood, bone marrow – Umbilical cord blood “bank” • Potential ACE project Guard cell Nerve cell Sperm cell Root epidermal cell Fat cell Red blood cell Guard cell • Occurs in pairs on the underside of a leaf • Each pair is shaped so that a tiny opening called stoma (plural: stomata) exists between them • Stomata allows for gaseous exchange between the leaf and the surroundings, and water to escape • The opening and closing of the stomata is caused by the guard cells changing in shape Sperm cell • Has to swim towards an egg to fertilise it • Has a “tail” called a flagellum to help it swim • Has much more mitochondria (part of the cell that releases energy) as compared to other cells • Store fat for future use • Recent studies have shown that the number of fat cells do not decrease when you lose weight – only the fat cell volume changes. • “If you are overweight and you lose weight, you still have the capacity to store lipids because you still have the same number of fat cells. That may be why it’s so hard to keep the weight off.” Fat cell • Multiple nerve endings • Specialised extensions to receive messages (dendrites) and send messages (axons) to other nerve cells quickly Nerve cell • Have long and narrow protrusions called root hairs • Large surface area for the absorption of water and minerals Root epidermal cell • Flat and biconcave in shape • Large surface area : Volume ratio – allows for rapid diffusion of gases • Contains haemoglobin which carries oxygen • Absence of nucleus • Elastic – can squeeze through narrow capillaries Red blood cell Cells – from cells to tissues Cells Tissues • In multicellular organisms, cells of the same type are organised into groups or layers called tissues • They work together to do the same job Animal tissues Nerve cells → nerve tissue • found in the brain and spinal cord • carries messages from one part of the body to another Cells Tissues • In multicellular organisms, cells of the same type are organised into groups or layers called tissues • They work together to do the same job Animal tissues Muscle cells → muscle tissue • found in the limbs and in the walls of some organs • contracts and relaxes to cause body movements Cells Tissues • In multicellular organisms, cells of the same type are organised into groups or layers called tissues • They work together to do the same job Animal tissues Fat, bone, blood, cartilage cells → Connective tissue • support and connect different tissues • join different parts of an organism Cells Tissues • Cells of the same type are organised into groups or layers called tissues • They work together to do the same job Epithelial cells → Epithelial tissue • protects structures beneath them Animal tissues Cells Tissues Vascular tissue • found in all parts of a plant • carries food (phloem) and water (xylem) to various parts of the plant Plant tissues Dermal tissue • found on surfaces of different parts of a plant • protects plants against injury and drying up Ground tissue • found mainly in the stems of plants • supports and strengthens the plant Cells – from tissues to organs Tissues Organs • Different tissues are usually grouped together to form an organ • Tissues in the organ work together to carry out one or more functions • Organs are covered by epithelial tissues for protection Animal organs Brain • consists of nerve tissue + connective tissue • controls the activities of the body Tissues Organs • Different tissues are usually grouped together to form an organ • Tissues in the organ work together to carry out one or more functions • Organs are covered by epithelial tissues for protection Animal organs Stomach • consists of muscular tissue + connective tissue • digests food Tissues Organs • Different tissues are usually grouped together to form an organ • Tissues in the organ work together to carry out one or more functions • Organs are covered by epithelial tissues for protection Animal organs Heart • consists of muscular tissue + connective tissue • Pumps blood around the body Tissues Organs • Different tissues are usually grouped together to form an organ • Tissues in the organ work together to carry out one or more functions • Organs are covered by epithelial tissues for protection Animal organs Lungs • consists of muscular tissue + connective tissue • enables gaseous exchange between the body and the surroundings Roots Flowers Leaves Plant organs Stems Cells – from organs to system Human organ systems • • • • • • • respiratory system circulatory system nervous system digestive system excretory system skeletal system reproductive system Plant organ systems Shoot system (above ground) Root system (below ground) Cells – from system to organism Different systems make up the whole organism. • Each system carries out its own function • Interacts and works together with other systems to enable the organism to function smoothly and efficiently :D Different systems make up the whole organism. Summary Cell Tissue Organ System Organism Digestive System – Digests food Division of labour exists amongst cells, tissues, organs and systems to ensure the organism functions properly and efficiently.