"Distribution of Bacteria and Fungi" Bacteria and Fungi PPT Courseware 4

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"Distribution of Bacteria and Fungi" Bacteria and Fungi PPT Courseware 4

think about it

1. Why do steamed buns grow "hair" after being stored for a long time?

Steamed buns that have been stored for a long time will grow "hair", which is the result of the reproduction of mold in the fungus.

2. How come fungus grows on rotten branches?

Fungi growing on rotten trees are actually fungi.

3. Why do nutritious milk and rice grains go bad?

When milk and rice go bad, bacteria invisible to our naked eyes are at work.

1. Observe the colonies

Comparison of bacterial and fungal colonies

Bacterial colonies are small, mostly white, with a smooth, sticky or rough and dry surface.

Fungal colonies are several to dozens of times larger than bacteria, come in many different colors, and are fluffy, flocculent or spider web-shaped.

2. General methods for cultivating bacteria and fungi:

Step 1: Prepare culture medium

Step Two: High Temperature Sterilization

Step Three: Vaccination

Step 4: Constant temperature culture

3. Research: Which one has more bacteria, dirty hands or clean hands?

1Ask the question: Are there more bacteria on dirty hands than on clean hands?

2 Make a hypothesis: Dirty hands have more bacteria.

Experimental steps:

Step 1: Prepare culture medium. Take three sets of petri dishes, label them, write the date on them, serialize them, and indicate the date.

Step two: vaccination. Open the petri dish, first wipe it on the dirty palms with a sterile cotton swab, then lightly apply it on the No. 1 culture medium a few times, and cover it; use another sterile cotton swab to wipe it on the clean palms. Then smear a few times on the No. 2 culture medium and cover it; leave the No. 3 culture medium untreated.

Step 3: Constant temperature cultivation. Place the three sets of petri dishes together in an incubator or a warm place indoors for 3 to 4 days.

Research experiment: detecting bacteria and fungi on palms and mobile phones

Ask the question: Are there bacteria and fungi on your palms and cell phones? Which environment is more common?

Make a hypothesis: There are more bacteria and fungi on mobile phones.

making plans

(1) Materials and utensils: three sets of petri dishes with beef juice culture medium (high temperature sterilized), sterile cotton swabs, label paper, and magnifying glass.

(2) Experimental steps: ① Number the three sets of petri dishes 1, 2, and 3;

② Apply the cotton swab used to wipe the mobile phone on the No. 1 culture medium; apply the cotton swab used to wipe the palm of the hand to the No. 2 culture medium; leave the No. 3 culture medium untreated.

③ Place the three sets of petri dishes in a warm place for cultivation at the same time.

④Observe and record after 2 days;

⑤Repeat the experiment more than 3 times and calculate the average value

test you!

1. In hot summer, food is prone to spoilage and more people suffer from gastroenteritis. Why?

Bacteria and fungi need the right temperature to live

2. In summer, damp food, clothing and leather shoes often become moldy and hairy. Why are damp glass, stone and cement walls not prone to mold?

Bacteria and fungi require organic matter to live

3. Which one is more likely to become moldy, sun-dried seeds or moist seeds? Why?

Moist seeds, bacteria and fungi need moisture to live

4. Living conditions

Basic conditions:

Moisture

suitable temperature

Most also require organic matter

Special living conditions:

Some bacteria and fungi also require specific living conditions. For example, lactic acid bacteria live in anaerobic conditions, and life activities are inhibited under aerobic conditions.

Homework

1. Scientists discovered archaea in extremely special environments such as deep-sea volcanic craters. What does the presence of archaea indicate?

This shows that archaea have strong ability to adapt to the environment and are widely distributed.

2. In the hot summer, food is prone to spoilage and more people suffer from gastroenteritis. Why is this?

Because in hot summer, the air humidity is high and the temperature is high, which is suitable for the reproduction and growth of bacteria and fungi.

If food is stored improperly or for too long, it will deteriorate due to contamination by bacteria and fungi. People are prone to gastroenteritis after eating spoiled food.

3. A classmate inoculated two bacteria, A and B, on an agar medium for culture. At the same time, he also placed pieces of paper soaked in salt water on the medium. After one day of constant temperature cultivation, only A bacteria grew around the salt paper. How do you interpret the results of this experiment?

A can adapt to salty environment, B cannot

Different bacteria require different living conditions

Come and see how much you have mastered in this lesson!

1. Which of the following descriptions about bacterial colonies is correct ( ).

A. Each colony is composed of a large number of different species of bacteria

B. From the shape, size and color of the colonies, bacteria and fungi can be roughly distinguished, as well as their types.

C. Bacterial colonies are often fluffy, flocculent or spider web-shaped

D. A colony is formed from one bacterial cell

2. Which of the following does not belong to the characteristics of bacterial colonies ( )

A. The colonies are relatively small B. The surface is smooth and moist

C. The colonies are velvety D. Easy to pick

3. When cultivating bacteria and fungi, the petri dishes and culture media must be treated at high temperature before inoculation. This is because: ( )

A. High temperature is one of the suitable conditions for the survival of bacteria and fungi;

B. Bacteria and fungi thrive in high temperature environments;

C. Bacteria and fungi in the culture medium and petri dishes need to be killed to avoid affecting the experimental results;

D. High temperature treatment can enrich the culture medium with nutrients.

4. In a small experiment to explore whether there are bacteria on the coin, the coin is gently placed on the surface of the bacterial culture medium. This practice is called ( ) in the general culture method of bacteria.

A. Vaccination b. Planting c. Cultivate D. join

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Update Time: 2024-10-05

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

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