2. How Plants Make Food

3.  Photosynthesis = the process by which plants make food  Photo = light  Synthesis = putting together  Takes place mainly in the leaves  Cells in the leaf have most of the chloroplasts that contain chlorophyll  Chlorophyll takes in light energy from the sun and changes it into chemical energy  Xylem and phloem tubes (veins) carry water from the roots to the chloroplasts AND carry food from the chloroplasts back to the stem and roots.  Veins help a plant keep its shape and keep it from wilting  The adaptation of a leaf being thin and flat helps the leaf take in as much sunlight as possible  Epidermis = the upper layer of a leaf that protects the inner cells like skin on a person.  Sunlight can pass easily through the epidermis

4.  The upper epidermis helps the leaf not lose water through the surface  Sometimes there is a waxy covering called a cuticle on the leaf that also helps the leaf not lose water  Palisade Layer = layer of cells below the epidermis made of long, thin, packed tight cells.  Lots of chloroplasts in these cells  Most photosynthesis takes place here  Spongy layer is next  Loosely packed cells with lots of air spaces  Air spaces allow carbon dioxide to pass through to get to the chloroplasts  Have chloroplasts in the spongy layer but not as much as the palisade layer  Lower epidermis is the underside of the leaf  Stomata are in this layer surrounded by guard cells  Guard cells can change shape to allow the stomata to open and close  Stomata open = carbon dioxide can enter the leaf and oxygen can leave  Stomata closed = not much water and no photosynthesis takes place

5.  Photosynthesis begins when the sun hits a leaf  Light is taken in by chlorophyll in the chloroplasts and is changed from light energy to chemical energy  2 reactions take place in the chemical energy 1. Water is split into hydrogen and oxygen 2. Hydrogen combines with carbon dioxide to make glucose and oxygen  Glucose is used by the plant for food and some is stored as starch  Oxygen is released into the air

6.  Most of the food that a plant produces is used by that plant for it to growth, repair, and reproduce  Cellular Respiration = plants releasing the energy in food to carry on the life process  Oxygen combines with glucose to form carbon dioxide and water and produce energy  Plants store food to use when they can’t make food (cloudy days or dry periods)  Stored food is starch. When the plant needs food, it can turn this starch back into glucose  Plants use 90% of their food. They give 10% to animals who eat it  Animals use most of food they eat to survive (90%)  Energy stored in the food is released by cellular respiration  Energy from the sun passes to the plant and then to the animal  10% of the food an animal eats is stored in their body  When an animal eats another animal, it gets stored energy from that animal.  All energy can be traced by to the SUN!!