Ecosystems1. Hand in your Action Plan.

2. To get back into the swing of things, I am going to give you a very short, open notes quiz. Get your notes out, review material

from before break.

Homework• I am missing at least one assignment from nearly everybody. Not okay. :(– Assignments turned in thus far this quarter: human population activity, population worksheet, yeast lab (individual, don’t turn just one in for the group because you need to answer the questions yourself), and elk game.

Open Notes• 1. All the members of a population belong to the same what?

• 2. If there’s no immigration or emigration, and the growth rate (r) is 0, what could be values for birth and death rates? (note: no immortality allowed)

• 3. Draw an exponential curve.• 4. Draw a logistic curve, and label K.• 5. Does a higher growth rate mean that a population will have a higher carrying capacity? Explain.

Open Notes• 1. Same species.• 2. Birth and death must be equal, positive numbers. They can be anything, so long as they’re both the same.

• 3. J-shaped curve.• 4. S-shaped curve. Carrying capacity is a horizontal line at the “plateau.”

• 5. No, r has no effect on carrying capacity at all. It only affects how quickly the population reaches carrying capacity.

Obectives• Learn the next level of organization up from “population”

• Learn about how energy enters a system of living things

Biological Communities• We’re going to spend a good long time now talking about more complicated things than populations, starting with communities.

• Community: All the populations that all live in the same habitat. – This adds to the levels of organization from before. Recall, what are the levels from smallest to largest?

Levels of Organization• Organelle• Cell• Tissue• Organ• Organ System• Individual• Population• Community• __________

Communities• A major topic in studying communities is the transfer of energy. Organisms can have interesting interactions with each other, and we’re going to start with the one you are probably most familiar with: predation.

• First, what is energy?– With your partner, define energy as best you can, and name as many different kinds of it as you can.

Energy• Energy is the quality of being able to do work.– It’s not a physical thing like an atom. But like atoms, energy can’t be made or destroyed. It can only be transferred from one place to another = Law of Conservation of Energy.

Energy• In ecology and the rest of biology, it’s all about what’s called chemical energy.–Chemical energy: the quality of being able to arrange or rearrange atoms.

– Every chemical compound has chemical energy. A molecule that can rearrange extensively is said to have lots of chemical energy.

Chemical Energy• When we’re talking about chemical energy, we’re really talking about… food!– Food is just a chemical that you can get energy from by rearranging it. It’s sort of complicated and a topic we’ll talk about more next year, but for now, just know that all organisms survive by using the chemical energy from glucose (sugar).

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Chemical Energy• So, you’re an organism. In order for your cells to do all the reactions that are necessary to survive, they need the energy from glucose.

• If you need glucose, a neat trick is just to make some!– Does anybody know what the root “auto-” means when you see it in a word?

Food!• Autotrophs are organisms that make glucose. Easy enough, right?– But, according to the Law of Conservation of Mass, energy can’t be created. It can only be transferred from somewhere else.

– So, if you’re going to make a glucose molecule that has energy, where’d the energy come from…?

Food!• Some organisms can perform what’s called chemosynthesis. (Chemo means chemical) In chemosynthesis, the organism gets the energy to make glucose from some in-organic, non-food chemical.– Methane is a common source. Hydrogen sulfide is another.

– Some bacteria and archaea can do this, but that’s it. The ones that can do it often live around deep sea vents. Generally, we’re not going to focus on it.

Food!• The major source of energy is, of course, the sun!

• The sun is constantly throwing a HUGE amount of energy at the Earth, we get 1000 joules of energy every m2 every second.

• This energy isn’t chemical energy, it’s light energy. Remember light photons?

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Food!• The sun is the original source of energy for nearly all living things.– Even you and I. We’ll talk more about critters like us later.

– The organisms that use the sun’s energy do so through a process called photosynthesis = making glucose using the energy from sunlight.

Photosynthesis• Take it away, Goofy Voice Guy: http://videos.howstuffworks.com/hsw/17173-photosynthesis-the-process-video.htm

Food!• So, you’re a plant, and now you have glucose, hooray! But, photosynthesis alone isn’t enough. What’s the point of making tons of glucose if it’s all just going to chill uselessly in your cells?

• All creatures - chemoautotrophs, photoautotrophs, and everyone else - can conduct cellular respiration = breaking the atoms of glucose apart to get energy for the cell to use.

Food!• So now the question is, why go to the trouble of making glucose if you’re just going to tear it apart anyways? Why not just use the sun to power your cell?– The answer is that there’s only one kind of chemical, called a photopigment, that can be affected by the sun, and that’s really all it can do. You can’t make a whole cell out of photopigment.• So it works like a relay race: some photopigments absorb sunlight energy, and hand it off to glucose.

• Then, glucose can go hand it off to any other part of the cell.

Energy• We’re going to have a lot of focus on tracking the movement of energy from place to place in a community, and it always starts with an autotroph or fifty. Organisms (autotrophs) who can produce glucose are called a community’s producers.– Easy enough, right?

Energy• An important distinction that many students tend to get wrong is that producers don’t produce energy. – That would violate the Law of Conservation of Energy.

– Producers are where energy enters a system of living things.

Energy• Producers have the distinction of not only being the point where energy enters the system, but they’re also bigger and buffer than everyone else in two important ways.– Producers have the highest biomass in a system. That means that if you were to count up all the atomic particles from all the community’s living things, producers would have the most.

– Think about it: have you ever seen a system with more rabbits than grass?

– Why do you think it is that producers have the highest biomass?

Energy• And, producers have the most total energy. All the energy in all the glucose in all the producers’ cells far outranks the energy that the other organisms have.– Why do you think this is?

Energy• This week, we’ll learn how to track energy as it moves through a system. We’ll also learn how to make diagrams to represent where biomass and energy are concentrated in a community.

• Right now, I’d like you to browse chapters 3-1 and 3-2 in the Bio books.– This should be something of a refresher from middle school, but if it’s totally alien to you, let me know so that we can cover the basics at some point.