"Distribution of Bacteria and Fungi" Bacteria and Fungi PPT Courseware 7

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"Distribution of Bacteria and Fungi" Bacteria and Fungi PPT Courseware 7

Review the past and learn the new

1. Before injecting drugs into patients, nurses always wipe the injection site with alcohol cotton balls. Do you know the reason for doing this?

Tip: The purpose of this is to remove bacteria, viruses, etc. from the skin surface.

2. Steamed buns and fruits will grow mold and hair if left for a long time. What are these "mold and hair"?

Hint: mold within fungi.

collaborative inquiry

Observe colonies

Read the textbook P55~P56 with pictures to clarify the meaning of colony and the difference between bacterial and fungal colonies:

1. Bacteria and most fungi are very small. If you want to know the "true face" of bacteria and fungi, what should you do?

Tip: Cultivate colonies of bacteria and fungi.

Explore and discuss:

1. Why must the petri dishes and culture media used for culture be treated at high temperatures before inoculation? Why use sterile cotton swabs?

Because after high temperature treatment, the spores of bacteria and fungi mixed on the petri dish and in the culture medium can be killed, thus eliminating contamination from other environments outside the experiment. Therefore, do not blindly open the petri dish before the experiment to prevent bacterial and fungal spores from falling on the culture medium. The purpose of using sterile cotton swabs in the experiment is also to prevent microorganisms on the cotton swabs from contaminating the culture medium.

2. Which step in the general culture method of bacteria and fungi is equivalent to Tip 4?

The operation in Tip 4 is equivalent to the inoculation step in general culture methods.

3. Through the communication between the groups, what do you think of the distribution of bacteria and fungi?

Bacteria and fungi are almost everywhere, but the distribution in different environments is different. For example, more bacteria and fungi are attached to hands and coins.

4. Under what environmental conditions are bacteria and fungi unlikely to exist? Isn't it possible that bacteria and fungi are not present in this inquiry? What's going on? Why?

Bacteria and fungi cannot exist in an environment that has undergone strict high-temperature sterilization. There is, for example, a set of petri dishes in the control group, because the petri dishes in the control group have been in a sealed state after high-temperature sterilization.

life link

1. What is the reason why food spoils quickly in hot summer?

Tip: The temperature is high in summer, and food contains moisture and organic matter. Bacteria and fungi can grow and multiply in large numbers, causing food to spoil.

2. When Mingming’s mother makes kimchi, she uses a jar (as shown in the picture), not only covers it with a lid, but also uses a circle of water to seal it. Can you explain the reason?

Tip: The jar is covered with water and sealed with water. The purpose is to prevent air from entering the jar and maintain an oxygen-deficient environment inside the jar. Because lactic acid bacteria can only decompose organic matter in vegetables into lactic acid in an oxygen-deficient or anaerobic environment.

3. Spring is here, and my mother washes and dries the cotton clothes before putting them in the closet for storage, saying that this way the clothes will not get moldy. Why are washed and dried clothes not prone to mold?

Tip: The growth of bacteria and fungi requires moisture, organic matter and suitable temperature. Washed and dried clothes lack the moisture and organic matter needed for the growth of bacteria and fungi.

Basic standards met

1. Multiple choice questions

1. Please decide which of the following statements about bacterial colonies is incorrect ( )

A. A large group of bacteria or fungi that can be seen with the naked eye is called a colony

B. Colonies are formed by the reproduction of a bacterium or fungus

C. As long as there are suitable conditions, colonies can be formed under natural conditions without artificial culture.

D. Bacterial colonies are generally smaller than fungal colonies

[Analysis] Choose A. This question tests your understanding of the concept of colony. Under suitable conditions, bacteria and fungi will multiply in large numbers. The visible aggregate formed after the reproduction of bacteria or fungi is a colony. Compared with bacterial colonies, bacterial colonies are smaller and fungal colonies are larger.

2. Regarding the description of the phenomenon shown in the figure, the incorrect one is ( )

A. Spots are colonies of mold

B. A spot is formed by a mold that reproduces in large quantities

C. Different colored spots on steamed buns are caused by different molds

D. A spot is a mold

[Analysis] Choose D. This question tests the judgment of bacterial and fungal colonies. Individual bacteria and molds are relatively small, and individual bacteria and molds cannot be seen with the naked eye. They can only be discovered after a colony has formed. The colonies on the steamed buns are relatively large, fluffy, and come in red, green, black and other colors, so the colonies can be judged to be mold colonies. Since each colony has a different color, it is formed by different molds.

5. (Extended exploration) The beautiful river has been polluted in recent years, a large amount of sewage has been discharged, garbage has floated on the river, and the originally clear river water has turned into smelly water. Students in a school's biology interest group want to measure the number of bacteria per milliliter of river water and have designed the following plan. Can you fill in the experimental report completely?

Tip: This experiment starts by culturing the bacteria and then counting them. The experimental steps for cultivating bacteria are divided into four steps:

first step:__________. In this step, we mainly use agar and _____ (fill in "soap water" or "beef juice").

Step 2: __________. The purpose of this step is ______________.

third step:__________. In this step, we took 5 ml of river water, diluted it 10,000 times and used 2 ml for the experiment.

the fourth step:_____. This step should last about a week and should be observed every day.

[Analysis] This question mainly examines the general process of cultivating bacteria and fungi. The culture of bacteria and fungi is generally divided into medium preparation, high temperature sterilization, inoculation and (constant temperature) culture. Step 1: Since bacteria need water, suitable temperature, organic matter, etc. to survive, sufficient organic matter must be added when preparing the culture medium to meet the needs of bacterial survival and reproduction. Beef juice is rich in organic nutrients, while soapy water No, so add beef juice to the agar. Step 2: Prepared culture

It can only be used after high-temperature sterilization. The purpose is to kill bacteria, fungi and spores in the petri dish and culture medium and eliminate the interference of other bacteria and fungi in the environment outside the experiment. Step 3: The polluted river water contains a large number of bacteria. We dilute it and use it, which greatly reduces the number of bacteria and facilitates counting after cultivation. The process of placing the diluted river water on the culture medium is called inoculation. Step 4: To culture, you can culture it in an incubator or in a warm place indoors.

Answer: Prepare culture medium, beef juice, high temperature sterilization, prevent bacteria and fungi in the environment from interfering with the experiment, inoculate and culture

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Update Time: 2024-07-29

This template belongs to biology courseware People's Education Edition Biology for Grade 8, Volume 1 industry PPT template

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