"Photosynthesis" PPT

Description

"Photosynthesis" PPT

Part One: Situation Import

Before the mid-18th century, people had always believed that all the nutrients needed for plant growth came from the soil. Including the ancient Greek philosopher Aristotle also thought so. Aristotle's conclusion is actually just an empirical speculation without corresponding scientific experiments. Today, the teacher introduced four scientific experiments in the classroom to experience the arduous process of discovering photosynthesis with the students!

learning target

1. Understand that the discovery of photosynthesis is the result of the wisdom and unremitting efforts of many scientists.

2. Understand the scientific way of thinking used by scientists to discover and solve problems.

3. Analyze its raw materials, conditions and products through the discovery process of photosynthesis.

Photosynthesis PPT, Part 2: Exploration Topic 1

Four science experiments

First half of the 17th century Helmont (Belgium) experiment

1771 Priestley (UK) experiment

1779 Ingelhaus (Dutch) experiment

1864 Saxophone (Germany) experiment

1. Helmont (Belgium) Experiment

He planted a willow seedling weighing 2.3kg into a wooden barrel containing soil. The weight of the soil in the barrel was 90kg. After that, he only used pure rainwater to water the willow seedlings. To prevent dust from falling in, he specially made a bucket lid.

Five years have passed, and Liu Miao has gradually grown up. He weighed the mass of the willow seedlings and soil again, and the result surprised Helmont: the mass of the willow seedlings increased by 74.5 kg, and the mass of the soil only decreased by 0.057 kg.

in conclusion:

The substances needed for the growth of willow seedlings are not directly transformed from the soil. Water is the substance that makes the plants gain weight.

Question:

Are Helmont's experimental conclusions completely correct? From the perspective of plant living environment, what other factors should be considered when analyzing the sources of materials needed for plant growth?

2. Priestley (UK) experiment

Put a lighted candle and a mouse in a sealed glass cover. Soon the candle went out and the mouse died.

Under light, a lit candle and a pot of green plant are placed in a sealed glass cover. The plant can live for a long time and the candle does not go out.

Under light, put a pot of green plants and a mouse into an airtight container at the same time, and both the plant and the mouse can live normally.

in conclusion

Green plants can purify the air that has become polluted by burning candles or breathing animals.

think

When people repeated Priestley's experiment, some succeeded, some always failed, and some even found that plants polluted the air more seriously. Why do scholars get different experimental results?

Photosynthesis PPT, Part 3: Exploring Topic 2

Explore photosynthesis

1. Verify that green leaves synthesize starch under light

Experimental principle

Whether green leaves synthesize starch under light can be tested with iodine solution. Because starch turns blue when exposed to iodine during a chemical reaction. However, it is difficult for iodine molecules to enter the living cells of leaves, and the color of the pigments in the chloroplasts interferes with the blue color displayed by iodine and starch. Therefore, boiling alcohol is used to kill the leaf cells and dissolve the chlorophyll in the alcohol. Iodine molecules soak into the cells of the decolored leaves, testing for the presence of starch.

2. Examine the release of oxygen during photosynthesis

3. Verify that plants require chlorophyll for photosynthesis

4. Test that photosynthesis requires carbon dioxide

Photosynthesis PPT, Part 4: Training to meet standards

1. The raw material of photosynthesis is ( )

A. Chlorophyll, water and carbon dioxide B. carbon dioxide and water

C. Starch and oxygen D. Light, chlorophyll and water

2. The conditions for plants to carry out photosynthesis are ( )

A. water b. carbon dioxide c. light d. chloroplast

3. In the experiment of green leaves synthesizing starch under light, potted geraniums were placed in a dark place for a day and night. The purpose was ()

A. Easy to check the amount of starch

B． Helps remove chlorophyll

C. Let the original starch in the leaves be exhausted

D. Easy to test with iodine solution

4. The correct order of the experiment "Green leaves synthesize starch under light" is ( )

①Put the leaves into a beaker filled with alcohol and heat it over water

②Put the geranium under the light

③Cover part of the geranium leaves with black paper

④Put the geranium in a dark place for a day and night

⑤Pick off the partially shading leaves and remove the black paper

⑥Rinse the leaves with clean water and add iodine solution dropwise

A. ②⑤①⑥ B. ④③②⑤①⑥

C. ②③④⑤①⑥ D. ②④③⑤⑥①

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Update Time: 2024-11-23

This template belongs to biology courseware Beijing Normal University Edition Seventh Grade Biology Volume 1 industry PPT template

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