Lesson B3: Photosynthesis, Respiration, Gas Exchange

Key Ideas   Unit Checklist

  Video Lesson

What substances do plants need to make their own food? Watch this video to learn more about how plants both make and use food.

  Lesson B3: Photosynthesis, Respiration, Gas Exchange

Figure B.1.3.1 – Spider plants grow runners with new plant “spiders” attached.
Figure B.1.3.2 – English ivy grows easily in pots.
Air-Cleaning Houseplants

In our modern world, we use lots of chemicals to make useful things. Sometimes in the process of making useful things or from those useful things, toxic chemicals are released into the air.

Scientists researching ways to clean air in spaceships determined that some plants are very effective at absorbing toxic gases from the air. Common houseplants that are good at cleaning air are English ivy, spider plants, peace lilies, and snake plants.
Reading and Materials for This Lesson

Science in Action 7
Reading: Pages 104–108

Materials:
No other materials are required for this lesson.
Figure B.1.3.3 – The leaves of snake plants look like snakeskin.
Figure B.1.3.4 – Peace lilies produce thin white flowers.

 Watch More

Fresh Air

When fresh air is lacking in buildings, people can develop lung problems and headaches. Some plants are especially good at cleaning toxic substances from the air and putting lots of oxygen back into the air. Watch this video to find out more about these plants.

 Think • Interpret • Decide

Dissolved Oxygen

The video below shows a simple experiment measuring how much oxygen is dissolved in water when a leaf is exposed to both light and dark.

After you have watched the video:

Think: What’s the point? Do you understand the results of this experiment? If not, watch it again.

Interpret:  Why were the dissolved oxygen amounts different when the leaf was in the light than when the leaf was in the dark?

Decide:  How does the amount of light exposure for the leaf affect the amount of oxygen in the water?
When plants make food by photosynthesis, they produce oxygen. Plants need light for photosynthesis.
When the leaf was in the light, it could photosynthesize. As a result, the plant produced more oxygen by photosynthesis. This caused the amount of dissolved oxygen to increase.
When the leaf was in the dark, it did not have any light for photosynthesis. As a result, the plant used oxygen in the process of cellular respiration. This caused the amount of dissolved oxygen to decrease.

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Photosynthesis

Photosynthesis in plants is very important for humans. Watch this animation to find out the reason.

  Connections

Figure B.1.3.5 – Deforestation in the Amazon rainforest is an increasing concern.
Figure B.1.3.6 – Large areas in the Amazon rainforest have been cleared of trees.

Connections: The Environment
>> Deforestation

Deforestation is the cutting of forests. Large areas of forest are cut to use the land for something else. After the trees are cut, people use the land for farming, ranching, mining, or building cities and towns. In fact, you might live in an area that was once forested, but the land was deforested for farming and some became the sites of towns and cities.

Deforestation in tropical rain forests such as the Amazon is a problem for several reasons.

  • Deforestation means that fewer trees are available for photosynthesis. Because trees are not available to use as much carbon dioxide as before cutting, the carbon dioxide stays in the atmosphere. Extra carbon dioxide in the atmosphere contributes to climate change.

  • Trees put water into the atmosphere through transpiration. Less water in the atmosphere changes rain patterns, which also affects climate change.

  • Cutting forests affects species of animals and insects that normally live in the forest. Without their natural habitats, species reduce in numbers, perhaps eventually to become extinct.

  • When trees in rainforests are cut, they cannot be replanted easily. When land is cleared of trees, bare soil is exposed. Rains wash away nutrients in the bare soil. This soil erosion often means large trees are unable to regrow because soil nutrients are not available.
Figure B.1.3.7 – Deforested land in the Amazon is used for cattle ranching.

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Amazon Deforestation

Watch this video to learn more about the cause of deforestation.

Brazil has had recent fresh water shortages. In this news report, a scientist talks about the link between deforestation and drought.

Brazilians trying to stop deforestation use satellites to see where the rainforest is being cleared each day. Watch this video to learn how people use technology to prevent deforestation.



Carnivorous Plants

Carnivorous plants trap and eat insects. Carnivorous plants have leaves and make their own glucose food by photosynthesis. So, why do carnivorous plants eat insects?

Carnivorous plants live in places where the soil contains few nutrients. Plants need nutrients other than glucose. Carnivorous plants catch and eat insects to obtain the additional nutrients that they cannot get from the soil.
Figure B.1.3.8 – When an insect touches the tiny hairs of a Venus Flytrap, the trap snaps shut.

Figure B.1.3.9 – The plant releases digestive juices to dissolve the insect into small particles.
Figure B.1.3.10 – Sundew plants have sticky tentacles to trap and eat insects.

 Watch More

Carnivorous Plants

Watch this video to see how carnivorous plants trap and eat insects.

  Connections


Connections: Literacy
>> Scientific Words


Many science vocabulary words are made of smaller words from the Greek and Latin languages.

Here are a few Greek and Latin words and their meanings.

Greek word
 Meaning    Latin word
 Meaning
 chloro  green    carn  flesh
 plast  formed or molded
   vorous  devour or eat
 photo  light    trans  through or across
 synthesis  putting together
   spirate  breathe
 graph  writing    capillus  hair

Questions

Think about the following questions very carefully. Then, type or write your answers. When you have your answers, click the questions for feedback.

Chloroplast means “green-formed”. The chloroplast is the green part of the leaf where food is formed.
Photosynthesis means “light putting together”. Photosynthesis is the process of light “putting together” food for a plant.
Photosynthesis and photograph both start with “photo”, which means “light”. Both photosynthesis and photographs involve light. Photosynthesis is the process of plants using light to make food, and photographs are made when cameras use light to “write” a picture.
Carnivorous, transpiration, and capillary action are science vocabulary words that come from the Latin language.



  Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.

Unit B Lesson 3 Self-Check

Instructions


Complete the following 6 steps. Don't skip steps – if you do them in order, you will confirm your understanding of this lesson and create a study bank for the future.

  1. DOWNLOAD the self-check quiz by clicking here.

  2. ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.

  3. COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.

  4. REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.

  5. SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.

  6. CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!


Self-Check Time!
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Self-Check Quiz Answers

Click each of the suggested answers below, and carefully compare your answers to the suggested answers.

If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.

The plant in the bedroom was exposed to more light than the bathroom plant was. Exposure to more light meant that the bedroom plant could make more food by photosynthesis. More food meant that the bedroom plant could grow larger than the bathroom plant that received light only when the bathroom light was on.
The girl had headaches because not enough fresh air was available in her room. She breathed in oxygen and breathed out carbon dioxide, but the oxygen was not being replaced. A houseplant in her room took in carbon dioxide through the process of photosynthesis and added more oxygen to the room. More fresh air with oxygen prevented the girl’s headaches.
Plants in fish aquariums photosynthesize. Photosynthesis adds oxygen to the water. Oxygen in the water is helpful for the fish in the aquarium. Fish need oxygen for cellular respiration so they can obtain energy.
When cars burn fuel, carbon dioxide enters the air. During the process of photosynthesis, trees absorb carbon dioxide produced by cars.
At night, trees and plants do not photosynthesize because no light is available. This means that trees and plants cannot remove carbon dioxide from the atmosphere. However, all living things are still putting more carbon dioxide into the air by cellular respiration. As a result, the amount of carbon dioxide in the air increases at night.