On Monday, the classroom aquarium had clear water and only a small amount of algae. By Friday, thick green algae covered much of the glass.
No one saw what caused the change, but students recorded information about the aquarium each day.
Examine the Evidence
| Day | Light Each Day | Water Temperature | Nitrate Level | Amount of Algae |
|---|---|---|---|---|
| Monday | 8 hours | 22°C | 5 ppm | Very little |
| Tuesday | 8 hours | 22°C | 5 ppm | Very little |
| Wednesday | 8 hours | 22°C | 24 ppm | Small patches |
| Thursday | 8 hours | 22°C | 23 ppm | Several patches |
| Friday | 8 hours | 22°C | 21 ppm | Thick growth |
The Science Question
Which change most likely caused the rapid algae growth?
Write a response containing at least five complete sentences.
Your response must:
- Make a clear claim identifying the most likely cause.
- Include at least two specific pieces of evidence from the table.
- Explain why the algae did not appear immediately after the change.
- Identify one variable that probably did not cause the algae growth.
- Explain why the evidence supports your conclusion.
You may begin with:
The rapid algae growth was most likely caused by…
Think Before You Write
Ask yourself:
- Which measurement changed before the algae began increasing?
- Which conditions remained constant?
- Why might a living organism need time to respond to a change?
- Does the evidence prove the cause, or does it identify the best-supported explanation?
- What additional information would make your conclusion stronger?
Post Your Response
Post your five-sentence explanation in the comments.
Use only your first name and class period. Do not include your last name, email address, or other personal information.
After posting, read one classmate’s explanation and respond with one of these sentence starters:
- The strongest evidence in your response is…
- I reached the same conclusion because…
- One variable your explanation rules out is…
- Another piece of evidence you could include is…
- We could test this explanation by…
Your goal is not simply to guess the cause. Your goal is to build the explanation that is best supported by the available evidence.
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29 Responses
The rapid algae growth was most likely caused by the time of day and the fact that the algae grew over the course of several days.
so it got big fast because it was 8 hours of sun light everyday and the Nitrate was getting higher day by day and the Water Temperature was the same everyday so that’s how it got bigger everyday
You did good joe! Keep up the good work.
Algae covers aquarium glass because. Algae can spread making it bigger over time. Like the example saying that. “It was Monday and on Friday it grew.” that is because the people gave it time to spread. and that is why algae grows in aquarium tanks.
This is alpha, I agree with you.
The strongest evidence in your response is when you said that people gave it time to grow and spread.
I think the most likely cause is the algae that has better growth on Friday because, the chart says on Friday the algae had thick growth.The chart also says that on Thursday the algae had several patches of algae.The algae didn’t appear immediately after the change because it had started off with a different water temperature.one variable that probably did not cause the algae to grow is the nitrate level.The rapid algae was most likely caused by the water temperature and nitrate level.
Aquarium algae grows becauses it has imbalance nutrients inside of the aquarium or you have the lights turn on for a long period of time.
I agree with you.
The algae might of grown a lot because the temperature remained calm and warm which I think is a perfect environment for them. Also because the Nitrate Level kept increasing over the days and with the nitrate level increasing it boosted its growth. I think this is how the algae grew a lot specially in one week. Also algae does not grow that fast.
The rapid algae growth was most likely caused by the nitrate level, and I think you have to have a specific amount of it. Or maybe it was the temp of the water. And maybe there is something in the water that helps the algae grow rapidly. If there was fish in there maybe the fish could’ve been the thing that made the algae grow. But I think it’s the nitrate level. I think this because when the nitrate level was on 21 ppm it grew very thick.
The algae growth was probably caused by a long period of time with the lights on or the tempature.
I think that the algae started to grow because of the temperature and light each day stayed the same and the algae built up. another reason the algae didnt start growing until the nitrate level increased. the algae didnt grow immediately after the change because algae takes time to grow. one thing that probably didnt help the algae growth was the amount of light each day. The rapid algae growth was most likely caused by the change in nitrate level and the amount of days the aquarium was left there.
JALIYAH A + response I’m so proud of you baby boo the most important evidence in your text “the algae started to grow because of the temperature and light each day stayed the same and the algae built up.” I LOVE YOU POOKIE BEAR!!!!!!!!
I think aquarium algae was caused, because the sun made it grow throughout the days that passed.
On Wednesday the Nitrate level was increased by 19 which caused the algae to grow more and more. If you look at the chart the algae starts increasing a bit more on Wednesday then Thursday the amount of algae became several patches, but the nitrate level started to go down.Then on Friday it turn into a thick algae but the nitrate was at 21 . I can confirm this since the water temperature did not change, the light each day did not change.Then on Wednesday the nitrate level was changed then it caused the algae to grow.
The fast algae growth was probably caused by a sudden spike in the aquarium’s nitrate level from the data table, the nitrate level jumped alot from 5 ppm on tuesday to 24 ppm on wednesday right before the algae started spreading alot and fast the thick green algae did not appear immediately on wednesday because living organisms require time to consume nutrients, grow, and reproduce conversely the water temperature and normal light exposure probably didn’t cause this, as both variables stayed completely the same at 22°C and 8 hours all week this evidence strongly helps support the conclusion because nitrates imitate as powerful fertilizer that disrectly fuels the fast overgrowth of aquatic plants and algae.
The most likely change is that the nitrate levels went up later in the week. you can see that Thursday and Friday had the most growth.
Also, since Wednesday was the first day the nitrate levels changed, the algae probably didn’t adapt immediately.
It barely grew on the first two days but then started growing faster. The reason I think it grew fast is because of the nitrate level suddenly going really high, and so thats why I think it was growing fast when that happened. Everyday it had the same water temperature and light each day and the only thing that really changed was the nitrate level so that’s why I think that lowk.
The most likely change is that the nitrate levels went up later in the week. you can see that Thursday and Friday had the most growth!!!!!!!!!!!!!!!!.
The algae grew by the temperature and lighting throughtout the day like a plant
I think it grew by sunlight and water.
Algae growth is driven more by the soil or the length of time the water sits inside; it can also be caused by dirt and other factors.
The most likely change is that the nitrate levels went up later in the week. you can see that Thursday and Friday had the most growth.
The algae growth was caused by a long time with the lights on and it takes time to grow. Since the algae was small on Monday it kept growing during the week. Then on Wednesday the algae kept increasing a bit more than it was on Monday. On Thursday there were several patches. I think the algae kept growing because the water temperature and the lights didn’t changed at all so the algae kept building up, so I think the reason why the algae kept growing was the water temperature and the lights at all.
I think what caused the rapid algae growth is the increase of the nitrate level. I think this because throughout the week everything had stayed the same and nothing had changed except for when the nitrate level would go up. Through the week the algae kept growing as the nitrate levels would go up and get higher reaching its highest on Friday even though the nitrate was lower than the day before. I think that happened because it started to spread too much and by the time the nitrate level started to go down it had spread and grown bigger.
I think the reason that the algae grew so fast is because the nitrate levels increased. Monday and Tuesday the nitrate levels were 5ppm but on Wednesday it increased to 24ppm when the algae grew to small patches instead of it being very little. Then it keeps on growing larger every day until it covers the entire aquarium.
Direct sunlight is a primary cause of rapid algae growth in aquariums.