Transcript PPT
Plants A study of multicellular organisms Cell Specialization • Why do cells specialize? – Increase efficiency • Division of labor – What does efficiency look like? • Special cell shapes, sizes, type and number of organelles, and locations in the organism Cell Specialization • The cell is the basic unit of life • In multicellular organisms cells take on specialized roles to perform a specialized function. – Tissues: Groups of cells that perform the same function are called tissues – Organ: Different types of tissues can combine together to form an organ – System: Different organs can also work together to form a system What are some functions done by different parts of a plant? Shoot System Root System Specialized cells in a leaf Tissue Types in the Leaf • Dermal Tissue – Thin protective outer layer • Ground Tissue – Middle layers • Vascular Tissue – Cells specialized in transport Dermal Tissue Epidermal Cells • Like skin cells, they form a protective layer on the upper and lower surface of the leaf – one cell layer thick – Arranged in a flat tightly knit sheet – Transparent to allow sunlight to pass through to cells that specialize in photosynthesis layer Cuticle • Covers the epidermis to prevent water loss – Waxy substance secreted by the leaf cells – Also protects from disease causing micro-organisms Stomata and Guard Cells • Small openings in the epidermal layer – Allow gasses and water to enter and leave the leaf – Mostly found on the underside of the leaf – Each stoma has 2 guard cells that regulate the stoma’s size Micrographs of Stomata Ground Tissue Ground Tissue • The majority of the plant • Located under the epidermis – In the stem • Provides strength, support – In the roots • Food and water storage – In the leaves • Where photosynthesis occurs What functions occurs inside a leaf? • Photosynthesis!!! – Leaves are flat and have a lot of surface area so that they can absorb the suns rays and use the energy to create glucose. • What is the chemical formula for photosynthesis? – CO2 + H2O C6H12O6 + O2 Where does photosynthesis occur? • Chloroplasts – Contain special pigments that capture light energy • Therefore, leaf cells contain a lot of chloroplasts Palisade Tissue Cells • Cells that are structured and arranged to maximize efficiency for photosynthesis – – – – Form a distinct layer in the leaf Long, and narrow (look like columns) Tightly packed Contain many chloroplasts Spongy Tissue Cells • Located below palisade tissue cells • Round and loosely packed, lots of air spaces – Helps exchange gasses and water with the environment • Contain some chloroplasts (thus, perform photosynthesis)