Principles of organisationOxford AQA IGCSE Biology: Flashcards

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What is a specialised cell?

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What is a specialised cell?: A cell that is adapted for a specific function through structural and functional modifications to suit its role within the organism.
Explain how red blood cells are specialised for their function.: Red blood cells lack a nucleus and organelles, allowing more space for haemoglobin to carry oxygen. Their biconcave disc shape increases surface area for oxygen absorption and allows flexibility to pass through narrow capillaries.
Describe the specialisations of a sperm cell.: Sperm cells have a flagellum (tail) for motility, mitochondria in the midpiece to provide energy for movement, and an acrosome at the head containing enzymes to penetrate the egg membrane.
Explain how an egg cell is specialised for its function.: Egg cells are large and contain abundant cytoplasm packed with nutrients (yolk) to support the developing embryo. They have a nucleus containing genetic material and a cell membrane that prevents entry of multiple sperm.
Describe the specialisations of ciliated epithelial cells.: Ciliated epithelial cells have cilia on their free surface that beat in a coordinated wave-like motion to move mucus and particles. They contain numerous mitochondria to provide energy for ciliary movement.
Explain how root hair cells are adapted for absorption.: Root hair cells have a long, thin extension (root hair) that increases surface area for water and mineral ion absorption. They contain numerous mitochondria to provide energy for active transport of mineral ions.
Describe the specialisations of palisade cells.: Palisade cells are elongated and tightly packed to form a dense layer. They contain numerous chloroplasts for photosynthesis and are positioned near the leaf surface to receive maximum light.
Explain how nerve cells (neurones) are specialised for transmitting signals.: Nerve cells have a long axon for transmitting electrical impulses over long distances. They have many branches (dendrites and synaptic terminals) to connect with other cells and receive/transmit signals.
Describe the specialisations of muscle cells.: Muscle cells contain numerous mitochondria to provide energy for contraction. They have contractile protein filaments (actin and myosin) that enable the cell to shorten and generate force.
State the levels of organisation in a multicellular organism, from smallest to largest.: Cells → Tissues → Organs → Organ systems → Organism
Define a tissue.: A group of similar cells that work together to perform a specific function.
Define an organ.: A structure made of different tissues working together to perform a particular function.
Define an organ system.: A group of organs working together to perform a major body function.
Name three animal tissues and state their functions.: Epithelial tissue (covers and protects surfaces), muscular tissue (enables movement), nervous tissue (transmits electrical signals).
Name three plant tissues and state their functions.: Xylem (transports water and mineral ions), phloem (transports sugars and other dissolved substances), epidermal tissue (protects and controls gas exchange).
Give an example of an animal organ and identify the tissues it contains.: The heart is an organ containing muscular tissue (for contraction), connective tissue (for support), and epithelial tissue (for protection). It functions to pump blood around the body.