From Cell to Organism: Focus on Plants Section 9.1 Science 10

Learning Outcomes By the end of this section you should be able to… describe why multicellular organisms need a level of organization to survive describe how leaf cells of plants have specialized structures and functions explain the gas exchange system in plants explain the transport system in plants describe phototropism and gravitropism

Unicellular vs Multicellular Organisms Unicellular Organisms Multicellular Organisms All life processes occur in a single cell Large surface area to volume ratio Short life BENEFITS DOWNFALLS Contain specialized cells that perform specialized functions Small surface area to volume ratio Longer life

Multicellular Organisms Specializations: Animal Cells Perform specific tasks: Muscle cells Nerve cells Skin cells Blood cells Plant Cells Perform specific tasks: Root cells Stalk cells Leaf cells Vascular cells

Organization of a multicellular Organism (plant or animal): Cells - perform a specific job Tissues - group of specialized cells working together Organs - tissues contributing to the same function Organ System - group of organs working together

Plants have two organ systems Above Ground Plant Organ Systems Plants have two organ systems Above Ground The shoot system: stem, leaves, buds, flowers, fruits & tubers Below Ground The root system: tap root, lateral roots & surface roots Students just write down the names of the two systems and whether they are above or below ground. More to come later.

Plants have three kinds of tissues: Dermal Tissue = Skin (or epidermis) Ground Tissue (mesophyll and palisade) Vascular Tissue = Circulatory (xylem & phloem) More to come later on these…

Cell Specialization in leaves Leaves are specialized to do Photosynthesis: carbon dioxide + water oxygen + glucose 6CO2(g) + 6H2O(l) 6O2(g) + C6H12O6(s) Suns energy chlorophyll Glucose is a carbohydrate used for energy in both plant and animal cells Oxygen gas, essential for both plants and animals, is produced as a by-product

How come plants can do Photosynthesis: Plants contain an important organelle that animals do not: CHLOROPLASTS Chloroplasts contain a pigment called CHLOROPHYLL traps light energy to drive the reaction

How do plants release energy from Photosynthesis? Cells Burn Glucose = Carbohydrate Source of energy (for all cells!) Glucose = C6H12O6

Cellular Respiration To obtain energy to fuel the cell’s activities a second general reaction is required. This process is cellular respiration Occurs in the Mitochondria

6O2(g) + C6H12O6(s) 6CO2(g) + 6H2O(l) oxygen + glucose carbon dioxide + water 6O2(g) + C6H12O6(s) 6CO2(g) + 6H2O(l)

Next Steps Cell Specialization in Organisms P. 320-324 of your text Label the specialized cells in a leaf Review Photosynthesis & Cellular Respiration

Plant Structure and Function Label your diagram of the cross section of a leaf (pg. 321 in your textbook) We will fill in the function in a minute

More on Plant Structures & Function Epidermal Cells Sponge Tissue Cells Stomata & Guard Cells Palisade Tissue Cells Vascular Tissue Cells

Epidermal Cells Epidermis Covers the upper and lower surfaces of the leaf The cuticle is a waxy layer that coats the upper epidermis to prevent evaporation of water from the leaf protect the cell They are transparent to allow solar energy to pass into the leaf

Palisade Tissue Cells The next layer down from the epidermis packed with chloroplasts where most of the leaf’s photosynthesis occurs They are long & narrow which allows them to pack closely together, therefore very efficient

Spongy Tissue Cells contain chloroplasts and carry out photosynthesis The layer below the palisade tissue cells These cells are round and loosely packed. Air spaces are between them, like a SPONGE exchange gases and water

Stomata pores in the leave which allows gases in and out They are embedded with in the lower epidermal layer CO2 in and O2 and H2O out

Guard Cells Each stoma is flanked by guard cells Regulate the stoma’s size Open and closes the stomata

Science 10, Plants Science 14-Sep-18 Page 309. Mitchell, 2004

Vascular Tissue Cells tubes that act as leaf veins transports fluids xylem – carries water and minerals from the roots to the leaves phloem – carries sugars made by the leaf to various parts of the plant

Science 10, Plants Science Features of the leaf. Science 10, Plants Science 14-Sep-18 palisade mesophyll vascular bundle --point out upper and lower epidermis --in the vascular bundle, the xylem is the pink stuff on top, in rows of “holes” and the phloem is the tiny blue/purple stuff underneath --under the phloem are dark pink rings. These are a supportive structure called “collenchyma”. FYI only; science 10 doesn’t need to know collenchyma. spongy mesophyll guard cells and stoma Mitchell, 2004

Science 10, Plants Science 14-Sep-18 Leaf Features This leaf is from a plant adapted to survive in dry weather. It looks somewhat different from the previous leaf, but they both have similar features. Can you spot them? Look for dermal, ground and vascular tissues. Mitchell, 2004

Science 10, Plants Science 14-Sep-18 cuticle upper epidermis palisade mesophyll vascular bundle spongy mesophyll air spaces Teacher Info: Thickened, waxy cuticle present on upper surface. It is transparent. In this picture, the upper epidermis is 3 layers thick, and stained red in colour. Two layers of palisade mesophyll. Difficult to make out the xylem and phloem in the bundle because it’s so tiny. Xylem is likely located facing the top of the leaf. Stomata are located in depressions that shelter pores from dry wind. May be surrounded by hairs. Reduced number of stomata. Stomata located on lower epidermis only. Lower epidermis is a few cell layers thick and stained red. guard cells (stoma is closed) lower epidermis Mitchell, 2004

To Do: Read pages 320-324 Photosynthesis & respiration in plants (BLM9-1) on back side of leaf diagram.