Five nutrient-agar Petri dishes are labelled 1 Control (not opened), 2 Inside of mouth, 3 Unwashed fingertip, 4 Clean fingertip and 5 A chosen surface. Observe through the closed lids; do not reopen growing cultures. Your teacher handles safe disposal.
Observe the Petri dishes every second day without a microscope. On your own, record your observations in the table below, using written notes or drawings. After a week, observe each dish with a hand lens. What do you see?
Record each of the five dishes on Day 3, Day 5 and Day 7.
| Petri dish | Day 3 | Day 5 | Day 7 |
|---|---|---|---|
| 1 Control | | | |
| 2 Inside of mouth | | | |
| 3 Unwashed fingertip | | | |
| 4 Clean fingertip | | | |
| 5 Chosen surface: ___ | | | |
Five nutrient-agar Petri dishes are labelled 1 Control (not opened), 2 Inside of mouth, 3 Unwashed fingertip, 4 Clean fingertip and 5 A chosen surface. Observe through the closed lids; do not reopen growing cultures. Your teacher handles safe disposal.
Rank the Petri dishes according to the number of microorganisms growing in each Petri dish. Exclude the control Petri dish. Use ranks 1 (least growth), 2, 3 and 4 (most growth).
Five nutrient-agar Petri dishes are labelled 1 Control (not opened), 2 Inside of mouth, 3 Unwashed fingertip, 4 Clean fingertip and 5 A chosen surface. Observe through the closed lids; do not reopen growing cultures. Your teacher handles safe disposal.
What types of microorganisms do you think grew in the Petri dishes?
Five nutrient-agar Petri dishes are labelled 1 Control (not opened), 2 Inside of mouth, 3 Unwashed fingertip, 4 Clean fingertip and 5 A chosen surface. Observe through the closed lids; do not reopen growing cultures. Your teacher handles safe disposal.
Why do you think microorganisms can grow on the agar?
Five nutrient-agar Petri dishes are labelled 1 Control (not opened), 2 Inside of mouth, 3 Unwashed fingertip, 4 Clean fingertip and 5 A chosen surface. Observe through the closed lids; do not reopen growing cultures. Your teacher handles safe disposal.
In investigations where a fair test is difficult to do, we often include a control. What is the purpose of the Petri dish labelled “control”?
Five nutrient-agar Petri dishes are labelled 1 Control (not opened), 2 Inside of mouth, 3 Unwashed fingertip, 4 Clean fingertip and 5 A chosen surface. Observe through the closed lids; do not reopen growing cultures. Your teacher handles safe disposal.
What does this investigation show us about microorganisms around us?
Five nutrient-agar Petri dishes are labelled 1 Control (not opened), 2 Inside of mouth, 3 Unwashed fingertip, 4 Clean fingertip and 5 A chosen surface. Observe through the closed lids; do not reopen growing cultures. Your teacher handles safe disposal.
Results are reliable if you can be sure that they are correct. Look at the order in which you ranked the Petri dishes in question 5. Outline and explain one way in which you could improve the investigation to make this ranking more reliable.
Five nutrient-agar Petri dishes are labelled 1 Control (not opened), 2 Inside of mouth, 3 Unwashed fingertip, 4 Clean fingertip and 5 A chosen surface. Observe through the closed lids; do not reopen growing cultures. Your teacher handles safe disposal.
Suggest and explain one other way in which you would change this investigation to find out how effective different cleaning methods are.
In a forest, there is a large amount of dead, fallen leaves. What is the role of decomposers in this situation? Tick the two correct answers.
1. Decomposers break down the leaves to release nutrients into the soil.
2. Decomposers use nutrients to make new substances they absorb from the soil.
3. Decomposers get their own nutrients from breaking down the leaves.
4. Decomposers use the leaves for photosynthesis.
Oil is an organic material. It was formed millions of years ago from the remains of dead organisms. Today, oil spills in oceans are a big problem as they harm marine life in ocean ecosystems. The spills need to be cleaned up quickly. One way to do this is to use bacteria that “eat” the oil.
Suggest two ways in which oil spills damage marine ecosystems. You may do some research to help you.
Oil is an organic material. It was formed millions of years ago from the remains of dead organisms. Today, oil spills in oceans are a big problem as they harm marine life in ocean ecosystems. The spills need to be cleaned up quickly. One way to do this is to use bacteria that “eat” the oil.
Oil is an organic material. It was formed millions of years ago from the remains of dead organisms. Today, oil spills in oceans are a big problem as they harm marine life in ocean ecosystems. The spills need to be cleaned up quickly. One way to do this is to use bacteria that “eat” the oil.
How are “oil-eating” bacteria that decompose the oil able to clear up oil spills? Think about the processes involved.
Work in pairs. You will carry out an investigation using two pieces of bread. One piece of bread is dry. The other piece of bread has had water added to it so that it is damp. Talk about what could happen if you leave both pieces of bread in the same, warm environment for a few days.
Two pieces of the same bread are kept in separate sealed, transparent bags in the same warm place. One is dry and the other has five drops of water added. A hypothesis is a suggested explanation. Write a hypothesis that you can test using the two pieces of bread.
Two pieces of the same bread are kept in separate sealed, transparent bags in the same warm place. One is dry and the other has five drops of water added. Use your hypothesis to make predictions about what will happen in an investigation if your hypothesis is correct. Complete a table with Conditions (Moist; Dry), Prediction and Reason.
Two pieces of the same bread are kept in separate sealed, transparent bags in the same warm place. One is dry and the other has five drops of water added. Predict what will happen to both pieces of bread after a few days.
Two pieces of the same bread are kept in separate sealed, transparent bags in the same warm place. One is dry and the other has five drops of water added. Observe the pieces of bread daily for five days. Look for the presence of mould and any changes in the mould. If needed, use a magnifying glass to help with your observations. Write or draw your observations in a table: Day 1, 2, 3, 4, 5; Dry bread; Moist bread. Do not open bags containing mouldy bread.
