Question 20 What two sources does earth get all its energy from? (Think back to earth science...)

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1 Question 20 What two sources does earth get all its energy from? (Think back to earth science...)

2 Earth's Energy Sources The Sun Earth's Internal Energy / Heat

3 3 Types of Organisms Autotrophs ( self feeding ): Green Plants Organisms that can harness the energy from the sun to make their own food (photosynthesis). Heterotrophs ( other feeding ): Everything Else Organisms that cannot make their own food. They must eat other organisms to obtain nutrients (sugar for energy and the other macromolecules for structure) Chemotrophs A few types of ocean bacteria can make their own food from chemicals in the ocean

4 Think about it... All organisms ultimately get their energy for living from the sun. Autotrophs (plants) are a crucial link between the sun and all other organisms. Even meat eaters ultimately get their energy from the sun...they eat other animals...which ate something else...which ate plants...which got their energy from the sun.

5 What do plants need to grow? Make a list of the things that plants need to grow.

6 Plants Need... Soil (for minerals and some organic material) Water Carbon Dioxide Sun

7 Question Where do plants get their food from? From the soil? What do you think?

8 An experiment... Up till the 1600's everyone thought plants got their food from soil. A Belgian physician named Jean Baptiste van Helmont decided to test this assumption. Weighed a young willow tree and the soil it was in. Five years later he weighed them again. The tree was much heavier, but the soil was pretty much the same (only lost 57 grams) The plant had gotten its food (energy) and raw materials for growing from somewhere else...

9 Photosynthesis: The Big Picture Plants take in Carbon Dioxide (CO 2 ) and water (H 2 O). Using the suns energy (absorbed by chlorophyll) they combine these substances to make glucose sugar (C 6 H 12 O 6 ) and oxygen (O 2 ) Glucose is then used to make enegy (after photosynthesis the plants metabolize the sugar in mitochondria to make ATP) Oxygen is necessary for this metabolism (last step of metabolism) Also, some extra O 2 is released. (Which is important for us!) Glucose is also used to build the structures of the plant. (Cellulose, etc...)

10 The Photosynthesis Equation Chlorophyll is a green pigment found in plant leaves. It absorbs sunlight and used the energy in the light to make the above reaction happen. Chloroplasts are the organelles inside leaf cells that contain chlorophyll.

11 Another way to look at Photosynthesis...

12 A little about how we see colors... Light is made of different colors. When you see a rainbow, drops of water in the air are acting like a prism separating light into its component colors.

13 What is light made of? Light is made of little packets of energy called Photons. The amount of energy a photon has determines what color it is. All the colors combine to make white light (what we see) Objects absorb some of these colored photons and reflect others. The color it reflects is the color we see the object as.

14 An example An apple absorbs all the colors in the light except red. It reflects the red photons. The red photons enter our eyes and we see the apple as red.

15 What does this have to do with plants? Chlorophyll absorbs all the colors except green. It reflects green so we see leaves as green. The chlorophyll is able to absorb (capture) all these other color photons and use the energy to carry out the reactions of photosynthesis. Note: There are several different types of chlorophyll. Chlorophyll a is able to use the energy from the photons. Chorophyll b,c, and d help chlorophyll a use more colors and

16 How it works: The Heavy Duty Details Light Dependent Reactions (Need Light) Chlorophyll captures photons (energy) and turns them them from light energy into chemical energy molecules. Makes ATP and NADPH (energy molecules) Water is split by light and oxygen is produced. Light Independent Reactions (Dark Reactions - Don't need light) Enzymes (run by the ATP and NADPH) catalyze a series of reactions that take CO 2 and water and turn them into glucose. (Calvin Cycle) CO from the air is turned into a chain to make

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18 Where does photosynthesis happen in the cell? Photosynthesis happens in Chloroplasts. Chloroplasts are organelles that contain chlorophyll.

19 How does Carbon Dioxide get into the leaf and extra O 2 leave? Leaves have openings called Stomata. They are like pores that allow gases in and out of the leaf. Guard Cells determine how much the pores open to control the amount of gases going in and out (including water vapor...important when it is hot out and in desert plants!) Spongy layer stores air.

20 See diagram on page 49 of your Textbook

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22 Why are leaves flat? Leaves are flat so that they have more surface area...to absorb as much sunlight as possible. Like a biological solar panel...

23 What happens in the Fall? Plants have other pigments that the presence of chlorophyl hides. In the fall plants stop making chlorophyll to get ready for winter. These other pigments reflect the other colors we never see...red, orange, yellow... Ultimately all nutrients, pigments, etc...get sucked back into the plant from the leaves (storage for winter). The leaves turn brown, die, and fall off for winter.

24 Rates of Photosynthesis Temperature Higher temp increases photosythesis (molecules move faster) Too much temperature kills enzymes though. Light Intensity Increasing light also increases photosynthesis...to a certain point. Increasing CO 2 Concentration The more raw materials around the more plants can photosynthesize.

25 Rates of Photosynthesis Decreasing Water Although plants only use a little water...decreasing water severely decreases photosynthesis rate. Minerals Minerals from the soil are necessary for photosynthesis. Minerals act as cofactors / coenzymes. Without them enzymes carrying out the reactions don't function! Magnesium and Nitrogen are especially important...they help to make chlorophyll.