2SG1 - Unit 2 Mid-Unit Study Guide

Zombie Fire - Ground fires do not flame but burn more slowly and have the tendency to spread deep into

the ground and spread laterally.

Fuel - Something with a lot of energy in it that can burn Ex, Wood, gasoline, and alcohols are all fuels.

Peat - Formed over time (hundreds to thousands of years) by layers of dead plants building up

underwater and not decomposing.

Energy - Cannot be created or destroyed. A measure of something’s ability to do work. Ex: gravitational

potential, chemical, solar.

Matter - Everything is made up of matter. It has mass and can most commonly be found as a solid, liquid,

or gas.

Carbon Sink - A carbon sink is a large store of carbon (energy/matter) that is keeping it out of the

atmosphere.

Burn Scar - Blackened areas left on the forest floor after a fire.

Socio-ecological components - How social (human) and ecological systems influence one another.

Permafrost - A subsurface layer of ground that stays frozen year round.

Photosynthesis - A process in plants that converts energy (sunlight) into food (sugars). Carbon dioxide

and water combine to form carbon-based molecules (sugars) and release oxygen.

Cellular respiration - Occurs in plants and animals and involves chemical reactions with oxygen that

release stored energy. In these processes, complex molecules containing carbon (glucose) react with

oxygen to produce carbon dioxide, water and chemical energy.

Tilt - The orientation of the earth’s axis of rotation relative to the sun. Ex: the earth’s tilt was different

11,000 years ago.

Chemical Energy - The energy which is stored in the bonds of chemical compounds

(molecules and atoms).

Independent Variable - The change under investigation. Ex: The fuel we burned

Dependent Variable - What is affected by change. Ex: The mass of the solid after burning

Energy and Matter Flow

1. How does a drop in temperature affect the flow of energy and matter in an ecosystem? Why

might this be significant for plant and animal survival?

A drop in temperature slows down the flow of energy and matter because chemical reactions, like

those involved in decomposition and respiration, happen at a slower rate. This can affect energy

transfer in food webs and impact ecosystem dynamics.

2. Describe how temperature changes could influence energy flow between living organisms

and their environment.

Temperature changes reduce metabolic rates in organisms and can lead to slower decomposition and

nutrient cycling, affecting both producers and consumers.

Peat and Zombie Fires

3. What makes peat prone to zombie fires, and why do these fires pose a unique

environmental challenge?

Peat is prone to zombie fires because it can smolder underground for long periods. These fires can

reignite above ground later under dry conditions, contributing to greenhouse gas emissions.

4. Discuss how stored energy in peat interacts with oxygen to influence fire behavior.

When oxygen levels increase in peat, stored energy becomes more accessible for combustion,

making it highly flammable and contributing to fire spread.

5. How do dead plants contribute to the formation of peat in low-oxygen environments?

Dead plants under low-oxygen conditions slowly decompose, and their organic matter becomes

compacted, forming peat over time.

6. Why does the carbon in dead plants become "locked" in peat, and under what conditions

might it be released?

Carbon in peat becomes trapped due to the slow decomposition process. Thawing frozen peat (from

permafrost) or burning releases this carbon back into the atmosphere, impacting the climate.

7. Why is peat considered a significant source of stored energy, and which molecules are most

prevalent in peat?

Peat is a rich source of carbon-based molecules like sugars and organic matter. This makes it an

important long-term carbon sink in ecosystems.

8. How do stored carbon-based molecules in peat contribute to climate change?

Peat’s carbon-based molecules are released into the atmosphere through decomposition or burning,

contributing more carbon dioxide (a greenhouse gas) to the atmosphere.

9. How does the thawing of permafrost impact the carbon sink and contribute to climate

change?

Thawing permafrost reduces the carbon sink: peat’s carbon-based molecules are released into the

atmosphere through either decomposition or burning. Both decomposition and burning increase

when permafrost thaws. The decomposition or burning of peat releases previously trapped carbon

dioxide (a greenhouse gas) into the atmosphere.

10. Explain the process of photosynthesis and why it is essential for energy storage in plants.

Photosynthesis uses solar energy to convert carbon dioxide and water into chemical energy stored in

sugars, which plants use for growth and reproduction. Without it, ecosystems would lack an energy

source.

11. Compare and contrast photosynthesis and cellular respiration in terms of energy and matter

transformation.

Photosynthesis stores energy in glucose molecules, while cellular respiration breaks glucose down to

release energy. The matter involved in both processes are the same, but in opposite directions.

Photosynthesis uses sunlight to rearrange the matter in carbon dioxide and water into sugar

molecules, with extra oxygen released as “waste”. Cellular respiration breaks down the matter in sugar

molecules using oxygen to release energy and gives off water and carbon dioxide as “waste”. Both

processes are vital but occur in opposite directions.

Decomposition

12. Why does decomposition slow down in low-oxygen environments, and what happens to

organic matter in such conditions over time?

In low-oxygen environments, decomposition slows down, allowing organic matter to accumulate

over time. Dead plants can form peat under these conditions.

13. How does the presence of oxygen affect the decomposition process in peat after permafrost

thaws?

Oxygen increases decomposition because it allows decomposers to break down matter more

efficiently (higher rates of cellular respiration because of oxygen), releasing carbon dioxide.

Arctic Conditions and Historical Energy Storage

14. What environmental conditions in the past allowed for increased energy and matter storage

in Arctic plants?

Increased plant growth in the Arctic during past periods was due to a different tilt of the Earth’s axis,

resulting in more solar radiation in the Arctic region. More solar radiation allowed for more

photosynthesis (converting sun energy into stored energy in sugars in plant matter).

15. How did low temperatures in Earth's history contribute to the formation of large amounts of

peat?

Low global temperatures slowed down decomposition, enabling peat to form as plant material

accumulated faster than it decomposed. Then, formation of permafrost (frozen ground year round)

further preserved the peat underground in the Arctic Circle.

Investigations and Experiments

16. What was the purpose of the yeast lab? What were the independent and dependent

variables? What did we control (keep the same)?

We used yeast and sugar to investigate how temperature affects decomposition. The independent

variables were temperature and time and the dependent variable was the amount of carbon dioxide

produced, measured by the height of the foam. We controlled the amount of yeast, water, and sugar

for each experiment.

17. What was the purpose of the elodea lab? What were the independent and dependent

variables? What did we control (keep the same)?

We used elodea plants and BTB to investigate how light conditions affect photosynthesis rates. The

independent variable was light exposure and the dependent variable was the amount of carbon

dioxide produced, measured by the height of the foam. We controlled the amount of yeast, water,

and sugar for each experiment.

18. How does the starch test help study stored energy in plants, and what might its results

reveal?

The starch test detects stored carbohydrates in plants, indicating the energy reserves available for

growth and survival. A darker color (purple/brownish) indicates more starch is present, which is more

energy stored.

19. In the peat lab, why might peat be harder to ignite compared to other fuels, and what does

its behavior during burning tell us about its energy properties?

Peat is harder to ignite because of its moisture content and density. Once lit, it burns slowly,

producing smoke and releasing stored carbon as carbon dioxide. Its slow burning behavior is evidence

for a lot of stored energy in the matter.