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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
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<title>Grade 7 - 9 Workbooks | Natural Sciences Grade 7</title>
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<div class="container lifeandliving">
<div id="toc" class="col-md-3 pull-left"></div>
<h1>Natural Sciences Grade 7</h1>
<div id="contents" class="col-md-9 main-content">
<div class="section">
<h1 class="title" id="toc-id-0">The Biosphere</h1>
<div class="note col-md-12" data-type="keyquestions">
<ul data-class="ListBulleted">
<li>What is the biosphere?</li>
<li>What are the coldest or hottest places where life can exist?</li>
<li>How deep can you go in the sea before you do not find anything living anymore?</li>
<li>Are there living organisms on top of the world's highest mountains?</li>
<li>How can you tell if something is alive or if it was never alive?</li>
<li>What do organisms need to stay alive?</li>
<li>How come some organisms can live in certain places while others cannot?</li>
</ul>
</div>
<p>Let's start exploring the world around us and how it works! Remember that this is your book! You must use it to explore and ask questions about the world around you, and also to learn about yourself and who you are. Do not be afraid to take notes in the margins of this book - make your own scribbles and notes to yourself about points to remember or questions you would like to ask. Be curious! Explore and imagine the possibilities of what you can do with science!</p>
<div class="section">
<h2 class="title" id="toc-id-1">What is the biosphere?</h2>
<div class="note col-md-6" data-type="newwords">
<ul data-class="ListBulleted">
<li>atmosphere</li>
<li>biosphere</li>
<li>depend</li>
<li>environment</li>
<li>habitat</li>
<li>microorganism</li>
<li>organism</li>
</ul>
</div>
<div class="note col-md-6" data-type="takenote">
<p>All the 'New words' listed in the boxes in the margin are defined in the glossary at the end of this strand.</p>
</div>
<p>
Have you heard the word 'sphere' before? Do you know what it means? A sphere is normally used when talking about a round shape (like a ball). Now, what do we mean when we talk about the <strong>biosphere</strong>? The prefix 'bio-' indicates something to do with life. For example, 'biology' is the study of living organisms. So, can you put these two meanings together to work out what 'biosphere' means?
</p>
<p>The biosphere is the place where life exists on planet Earth. When we talk about the biosphere, we are talking about a huge system (the whole world!) and how all the different parts work together to support life. We will look at these different parts in more detail a bit later.</p>
<div class="note col-md-6" data-type="didyouknow">
<p>
The first person to use the term 'biosphere' was the geologist Eduard Suess in 1875 when he wrote a definition for the biosphere as 'the place on Earth's surface where life dwells<em>.</em>'
</p>
</div>
<figure>
<img src="images/gr7ll01-gd-0001.jpg" width="300"/><figcaption class="caption">The biosphere is where life exists on our planet, including the soil and rocks, water and air.</figcaption>
</figure>
<div class="note col-md-6" data-type="takenote">
<p>The 'Visit' boxes in the margins contain links to interesting websites and videos. Simply type the link exactly as it is into the address bar in your browser.</p>
</div>
<p>
We can also use the term biosphere in different ways. When we speak of all life on Earth as it interacts with the non-living rocks and soil, water and air (<strong>atmosphere</strong>), we call this the biosphere.
</p>
<figure>
<img src="images/gr7ll01-gd-0002.jpg" width="300" alt="http://commons.wikimedia.org/wiki/File:Biosphere\_2\_Habitat\_\%26\_Lung\_2009-05-10.jpg"/><figcaption class="caption">Biosphere 2 is a man-made research centre in America, in the Arizona desert, where scientists have built a large enclosed artificial biosphere. </figcaption>
</figure>
<div class="note col-md-6" data-type="visit">
<p>
Learn more about Biosphere 2, a fascinating ongoing project to maintain a man-made biosphere<a data-class="ExternalLink" href="http://bit.ly/18cwCth">bit.ly/18cwCth</a>
</p>
</div>
<p>
We can also call a specific part or region on Earth that supports life, a biosphere, especially when we refer to the living organisms and the <strong>environments</strong> in which they live.
</p>
<div class="activity" data-type="Activity">
<h1 class="title">Where do you think life exists on Earth ?</h1>
<p>
<strong>INSTRUCTIONS:</strong>
</p>
<ol data-class="ListEnumerated">
<li>The following table contains some photos of different places on Earth. Describe what each photo is showing.</li>
<li>Then decide if you think life exists there or not. If you do think so, list some of the organisms which you think live in this place.</li>
</ol>
<table class="too-large">
<tr>
<td>
<p>
<strong>Aplace on Earth</strong>
</p>
</td>
<td>
<p>
<strong>What is this image showing?</strong>
</p>
</td>
<td>
<p>
<strong>Do you think there is life there? If so, what?</strong>
</p>
</td>
</tr>
<tr>
<td>
<figure>
<img src="images/gr7ll01-gd-0003.jpg" width="300"/>
</figure>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<td>
<figure>
<img src="images/gr7ll01-gd-0004.jpg" width="300"/>
</figure>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<td>
<figure>
<img src="images/gr7ll01-gd-0005.jpg" width="300"/>
</figure>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<td>
<figure>
<img src="images/gr7ll01-gd-0006.jpg" width="300"/>
</figure>
</td>
<td>
</td>
<td>
</td>
</tr>
</table>
<div class="exercises">
<div class="problemset">
<div class="entry"><div class="problem">
</div>
<div class="solution">
<table>
<tr>
<td>
<p>
<strong>Aplace on Earth</strong>
</p>
</td>
<td>
<p>
<strong>What is this image showing?</strong>
</p>
</td>
<td>
<p>
<strong>Do you think there is life there? If so, what?</strong>
</p>
</td>
</tr>
<tr>
<td>
<figure>
<img src="images/gr7ll01-gd-0007.jpg" width="300"/>
</figure>
</td>
<td>
<p>Adesert with rocks, some mountains and grass.</p>
</td>
<td>
<p>Yes, life exists here.</p>
<p>Organisms include:</p>
<ul data-class="ListBulleted">
<li>snakes</li>
<li>birds</li>
<li>grasses</li>
<li>cacti</li>
<li>insects</li>
<li>possibly buck, jackal, hares, etc</li>
<li>possibly humans (this is actually a photo from Namibia)</li>
</ul>
</td>
</tr>
<tr>
<td>
<figure>
<img src="images/gr7ll01-gd-0008.jpg" width="300"/>
</figure>
</td>
<td>
<p>Amountain range covered in snow.</p>
</td>
<td>
<p>Yes, life exists here.</p>
<p>Organisms include:</p>
<ul data-class="ListBulleted">
<li>trees (seen at bottom of photo)</li>
<li>possibly bears, snow leopards, rabbits, etc</li>
<li>possibly humans</li>
</ul>
</td>
</tr>
<tr>
<td>
<figure>
<img src="images/gr7ll01-gd-0009.jpg" width="300"/>
</figure>
</td>
<td>
<p>The sky with clouds and some birds.</p>
</td>
<td>
<p>Yes, life exists here.</p>
<p>Organisms include:</p>
<ul data-class="ListBulleted">
<li>birds</li>
<li>insects</li>
</ul>
</td>
</tr>
<tr>
<td>
<figure>
<img src="images/gr7ll01-gd-0010.jpg" width="300"/>
</figure>
</td>
<td>
<p>Soil with grass growing on top.</p>
</td>
<td>
<p>Yes, life exists here.</p>
<p>Organisms include:</p>
<ul data-class="ListBulleted">
<li>plants (grasses and other shrubs)</li>
<li>insects</li>
<li>earthworms</li>
<li>microorganisms</li>
</ul>
</td>
</tr>
</table>
</div>
</div>
</div>
</div>
</div>
<p>After doing this activity, did you see that life exists everywhere on Earth? From the highest mountains to the deepest oceans, from the hottest deserts to the thickest jungles, there is life. Did you also notice that when describing the places on Earth where life exists, you used words such as soil, rocks, water, air? These are all part of the biosphere and have special names.</p>
<div class="section">
<h3 class="title" id="toc-id-2">Components of the biosphere</h3>
<div class=" col-md-6 note" data-type="newwords">
<ul data-class="ListBulleted">
<li>adapt</li>
<li>aquatic</li>
<li>component</li>
<li>hydrosphere</li>
<li>lithosphere</li>
<li>marine</li>
<li>matter</li>
<li>organic</li>
<li>photosynthesis</li>
<li>respire</li>
</ul>
</div>
<p>
In the previous activity we saw that life can be found in water, soil and rocks or the air around us. These <strong>components</strong> form part of the biosphere and have special names:
</p>
<ul data-class="ListBulleted">
<li>
<strong>Lithosphere</strong> which includes the soil and rocks.
</li>
<li>
<strong>Hydrosphere</strong> which includes all the water.
</li>
<li>
<strong>Atmosphere</strong> which includes all the gases.
</li>
</ul>
<p>
The biosphere includes the lithosphere, hydrosphere and atmosphere. The biosphere includes all living organisms, and also dead <strong>organic matter</strong>.
</p>
<div class="activity" data-type="Activity">
<h1 class="title">Describe the components of the biosphere</h1>
<p>
<strong>INSTRUCTIONS:</strong>
</p>
<ol data-class="ListEnumerated">
<li>Study the following photo that shows the components of the biosphere.</li>
<li>Identify and describe the elements of the lithosphere, hydrosphere and atmosphere that you can see in the photo.</li>
</ol>
<figure>
<img src="images/gr7ll01-gd-0011.jpg" width="300"/><figcaption class="caption">The lithosphere, hydrosphere and atmosphere on Earth.</figcaption>
</figure>
<div class="exercises">
<div class="problemset">
<div class="entry"><div class="problem">
<p>Lithosphere: </p><hr/>
<hr/>
</div>
<div class="solution">
<p>There are rocks. They are hard, sharp, porous in places, eroded by water. There is sand. It is grainy, rough, contains many small pieces of shell and rocks.</p>
</div>
</div>
<div class="entry"><div class="problem">
<p>Hydrosphere: </p><hr/>
<hr/>
</div>
<div class="solution">
<p>This is the seawater and sea spray. Some learners might mention the water vapour that evaporates from the sea. The water is clear and fast flowing, the sea water tastes salty, the sea foam forms on top.</p>
</div>
</div>
<div class="entry"><div class="problem">
<p>Atmosphere: </p><hr/>
<hr/>
</div>
<div class="solution">
<p>This is the gases. The air includes gases such as oxygen, carbon dioxide and nitrogen. Atmospheric gases are not visible, but the sky looks blue.</p>
</div>
</div>
<div class="entry"><div class="problem">
<p>Even though you cannot see living organisms in this photo, there are many living and dead plants and animals that could live on a beach such as this one. Make about 10 plausible (believable) guesses of the types of organisms which would live in this environment. (Hint, think about what might be living in the sea, sand or air.) </p><hr/>
<hr/>
<hr/>
</div>
<div class="solution">
<p>Learner-dependent answer. Learners should be able to imagine for example dolphins swimming in the water, or snails or mussels on the rocks, seaweed in the water and perhaps microbes in the sand. Other organisms could be: crabs, sea gulls and other birds, many types of fish, sharks and whales out at sea, corals, anemones, etc.</p>
</div>
</div>
</div>
</div>
</div>
<p>Different organisms can exists in different places in the biosphere. Let's have a look at the different components of the biosphere and which types of organisms exist there.</p>
<div class="section">
<h4 class="title">Atmosphere</h4>
<p>The atmosphere is the layer of gases that surrounds the Earth. The three most important gases in the atmosphere are nitrogen, oxygen and carbon dioxide. The atmosphere is made up of several layers.</p>
<div class="note col-md-6" data-type="visit">
<p>
A fun infographic about the atmosphere<a data-class="ExternalLink" href="http://bit.ly/132W0U0">bit.ly/132W0U0</a>
</p>
</div>
<div class="note col-md-6" data-type="didyouknow">
<p>The Earth's atmosphere has changed over time. Our oxygen rich atmosphere was formed by algae millions of years ago.</p>
</div>
<div class="activity" data-type="Activity">
<h1 class="title">The atmosphere</h1><div class="teachers-guide">
<p>Learners do not need to know the layers of the atmosphere - this will be done in more detail in Gr. 9 Earth and Beyond. The focus of this activity is to show that the atmosphere is actually a very wide layer around the Earth, but life only exists at the bottom near to the Earth's surface where their requirements for life are met.</p>
</div>
<p>
<strong>QUESTIONS:</strong>
</p>
<div class="exercises">
<div class="problemset">
<div class="entry"><div class="problem">
<p>Discuss with your partner whether you think organisms could live on Earth without the atmosphere. Explain why you think so. </p><hr/>
<hr/>
<hr/>
</div>
<div class="solution">
<p>This questions is deliberately included to elicit debate. Without the atmosphere life as we know it would not be possible. The oxygen and carbon dioxide in the lower layers of the troposphere (that touches Earth) allow life to exist as organisms can respire and plants can photosynthesise. The atmosphere also helps to keep the Earth warm by trapping solar energy. The atmosphere protects life from too much UV radiation from the Sun. Earth is the only planet in our solar system that can support life, due in part to our atmosphere.</p>
</div>
</div>
</div>
</div>
</div>
<div class="note col-md-6" data-type="visit">
<p>
Our atmosphere is escaping! (video)<a data-class="ExternalLink" href="http://bit.ly/1beNzVB">bit.ly/1beNzVB</a>
</p>
</div>
</div>
<div class="section">
<h4 class="title">Hydrosphere</h4>
<p>The hydrosphere consists of all water on Earth in all its forms.</p>
<div class="activity" data-type="Activity">
<h1 class="title">The water cycle</h1><div class="teachers-guide">
<p>This acts as a revision of some of the previous work done on the water cycle and states of matter and links this to different aquatic habitats for organisms.</p>
</div>
<p>
<strong>INSTRUCTIONS:</strong>
</p>
<ol data-class="ListEnumerated">
<li>Study the following diagram describing the water cycle on Earth.</li>
<li>Answer the questions that follow.</li>
</ol>
<figure id="gd-idm19294768">
<img src="images/gr7ll01-gd-0012.jpg" width="300"/>
</figure>
<p>
<strong>QUESTIONS:</strong>
</p>
<div class="exercises">
<div class="problemset">
<div class="entry"><div class="problem">
<p>Do you remember learning about the different states of matter? The hydrosphere includes all water in all the states of matter. Look at the diagram of the water cycle and identify water in the different states of matter. </p><hr/>
<hr/>
<hr/>
</div>
<div class="solution">
<p>Water is a liquid in the sea, dams, river, rain and dew.</p>
<p>Water is a solid as snow on the mountains (or in hail).</p>
<p>Water is a gas as water vapour in the air.</p>
</div>
</div>
<div class="entry"><div class="problem">
<p>The water cycle shows different sources of freshwater and saltwater. Many plants, animals and microorganisms have adapted to live in an aquatic habitat. A very small percentage of the world's water sources are freshwater and the rest is saltwater. Write down as many different types of aquatic habitats that you can think of where different organisms exist. </p><hr/>
<hr/>
<hr/>
</div>
<div class="solution">
<p>Aquatic habitats include: rivers, dams, lakes, ponds, marshes, estuaries, groundwater and aquifers. There are many different aquatic habitats in the sea, such as rocky shorelines and rock pools, deep water and polar ice caps.</p>
</div>
</div>
</div>
</div>
</div>
<div class="note col-md-6" data-type="takenote">
<p>
The word 'aquatic' is used to describe something to do with water. Therefore aquaticanimals are animals that live in or near water. The word<strong>marine</strong>describes organisms that live in saltwater or the sea. So someone studying the organisms in the sea is called a marine biologist.
</p>
</div>
</div>
<div class="section">
<h4 class="title">Lithosphere</h4><div class="teachers-guide">
<p>Learners will look at the lithosphere in much more detail in Gr. 9 Earth and Beyond, where they will look at the rock cycle as well as mining in South Africa. This is meant as an introduction and the focus should be on how organisms interact with the lithosphere.</p>
</div>
<p>
As we have said, the lithosphere includes the rocks, soil and sand on Earth. Organisms <strong>depend</strong> on the lithosphere in many different ways. We find out how in the next activity.
</p>
<div class="activity" data-type="Activity">
<h1 class="title">How do organisms depend on the lithosphere?</h1>
<p>
<strong>INSTRUCTIONS:</strong>
</p>
<ol data-class="ListEnumerated">
<li>Below are several photos depicting different ways that organisms depend on and interact with the lithosphere.</li>
<li>Use these images to write a paragraph about how different organisms depend on the lithosphere in different ways.</li>
</ol>
<figure>
<img src="images/gr7ll01-gd-0013.jpg" width="300" alt="http://www.flickr.com/photos/cheezepix/1733216613/"/><figcaption class="caption">Bird nests </figcaption>
</figure>
<figure>
<img src="images/gr7ll01-gd-0014.jpg" width="300" alt="http://www.flickr.com/photos/sidelong/542808053/"/><figcaption class="caption">A rock pool </figcaption>
</figure>
<figure>
<img src="images/gr7ll01-gd-0015.jpg" width="300" alt="http://www.flickr.com/photos/71888644@N00/6310931034/"/><figcaption class="caption">A termite mound </figcaption>
</figure>
<figure>
<img src="images/gr7ll01-gd-0016.jpg" width="300" alt="http://www.flickr.com/photos/dodo-bird/477583981/"/><figcaption class="caption">A tree growing in the ground </figcaption>
</figure>
<div class="teachers-guide">
<p>A frequent misconception is that plants get larger and grow because of nutrients they absorb from the soil. However most of the organic mass from any plant is from carbon dioxide that is captured during photosynthesis and used to make organic molecules. It is important to stress that the main nutrient obtained from the soil is water, and relatively small amounts of minerals. If plants 'took up' the actual soil then one would expect it to be depleted and there would be large craters around every large tree!</p>
</div>
<figure>
<img src="images/gr7ll01-gd-0017.jpg" width="300" alt="http://www.flickr.com/photos/dodo-bird/477499086/"/><figcaption class="caption">An earthworm in soil </figcaption>
</figure>
<figure>
<img src="images/gr7ll01-gd-0018.jpg" width="300" alt="http://www.flickr.com/photos/87328375@N06/8434096665/"/><figcaption class="caption">A mud hut </figcaption>
</figure>
<hr/>
<hr/>
<hr/>
<hr/>
<hr/>
<hr/>
<div class="teachers-guide">
<p>Some of the things which learners could note are:</p>
<ul data-class="ListBulleted">
<li>Animals live in parts of the lithosphere, such as earthworms which live in the soil, ants which make their nests out of sand. Many microorganisms live in soil.</li>
<li>Some birds make their nests on rocks and also use sand to make the nests.</li>
<li>Most plants and trees need soil to grow in. They absorb water and minerals, and use the soil to anchor their roots.</li>
<li>Rocks form rock pools on the shoreline. Rock pools are homes to many different organisms.</li>
<li>Humans use mud and stones to build houses and other buildings.</li>
</ul>
</div>
</div>
<p>
We have now looked at the different parts of the biosphere and seen that there are many different types of organisms that exist. Each of the organisms that we have seen so far needs to be able to stay alive in those specific conditions. We say they need to <strong>adapt</strong> to live in their particular habitat. What does it mean to stay alive though?
</p>
</div>
</div>
</div>
</div>
<!--./section-->
<div class="section">
<h3 class="title" id="toc-id-3">Characteristics of living plants and animals</h3><div class="teachers-guide">
<p>This was first introduced in Gr. 4 Life and Living and then also revised in Gr. 5 and 6.</p>
</div>
<div class="note col-md-6" data-type="newwords">
<ul data-class="ListBulleted">
<li>abiotic</li>
<li>cellular respiration</li>
</ul>
</div>
<div class="note col-md-6" data-type="visit">
<p>
Video about the seven life processes<a data-class="ExternalLink" href="http://bit.ly/1cxrrZT">bit.ly/1cxrrZT</a>
</p>
</div>
<p>There are seven processes that all living organisms perform that determine whether they are alive or not. Let's have a look at the seven life processes:</p>
<div class="exercises">
<div class="problemset">
<div class="entry"><div class="problem">
<ol data-class="ListEnumerated">
<li>
<p>
All living things need to be able to <strong>move</strong>. Moving does not have to consist of big movements. Even plants move, for example as the flowers and leaves turn to face the sun during the course of the day.
</p>
</li>
<li>
<p>
All living things need energy to perform the life processes. Organisms release energy from their food by a process called <strong>cellular respiration</strong>.
</p>
</li>
<li>
<p>
All living things need to be <strong>sensitive</strong> to their environment. Think of an example of why animals need to sense their environment and write it down below.
</p>
<hr/>
</li>
<li>
<p>
All living things need to be able to <strong>grow.</strong>
</p>
</li>
<li>
<p>
All living things need to be able to <strong>reproduce</strong> so that they do not die out.
</p>
</li>
<li>
<p>
All living things need to be able to <strong>excrete</strong> waste.
</p>
</li>
<li>
<p>
All living things need <strong>nutrition,</strong> as they need to break down nutrients during cellular respiration to release energy.
</p>
</li>
</ol>
</div>
</div>
</div>
</div>
<div class="note col-md-6" data-type="visit">
<p>
Learn more about the seven life processes<a data-class="ExternalLink" href="http://bit.ly/16Cj2jz">bit.ly/16Cj2jz</a>
</p>
</div>
<p>Now that we can determine whether something is living or not, we can take a look at what living things need to survive. In other words, what are the requirements for life?</p>
</div>
</div>
<div class="section">
<h2 class="title" id="toc-id-4">Requirements for sustaining life</h2>
<div class="note col-md-6" data-type="newwords">
<ul data-class="ListBulleted">
<li>favourable</li>
<li>requirement</li>
<li>sustain</li>
</ul>
</div>
<p>
After studying the seven life processes, we now know what animals, plants and other living organisms need to <em>do</em> in order to be classified as living. In order to stay alive these living organisms <strong>require</strong> (need) certain things or specific conditions. In this section we are going to study the requirements necessary to <strong>sustain</strong> life.
</p>
<div class="note col-md-6" data-type="takenote">
<p>'Sustain'means to keep things alive or in existence. We also use the word sustainable when we want to say that something can continue or be continued for a long time.</p>
</div>
<div class="activity" data-type="Activity">
<h1 class="title">Identify the requirements for sustaining life</h1><div class="teachers-guide">
<p>The answers to this activity are summarised in the subsequent text. In order to get learners to first think about the answers and discuss them without just reading them up in the text, perhaps get them to first take notes in a separate notebook or on scrap paper and have the class discussion before opening the workbooks and allowing them to then take down some notes.</p>
</div>
<p>Imagine that you are the design team for the first International Moon Space Station, similar to the International Space Station already orbiting Earth, but situated on the Moon!</p>
<figure>
<img src="images/gr7ll01-gd-0019.jpg" width="300"/><figcaption class="caption">The international space station that orbits Earth, seen from above.</figcaption>
</figure>
<div class="note col-md-6" data-type="visit">
<p>
Find out more about life on the International Space Station as astronauts perform their everyday tasks.<a data-class="ExternalLink" href="http://bit.ly/178CXVe">bit.ly/178CXVe</a> or <a data-class="ExternalLink" href="http://bit.ly/1cfDcF7">bit.ly/1cfDcF7</a>
</p>
</div>
<p>
<strong>INSTRUCTIONS:</strong>
</p>
<ol data-class="ListEnumerated">
<li>Work in groups of four.</li>
<li>What do you think the astronauts and plants living on the new Moon Station will need in order to live? Discuss the five most important requirements that you need to provide in order for the astronauts and plants to remain alive on your Moon Space Station.</li>
<li>Explain why your group chose these five requirements as the most important to sustain life. Write down your notes from your group discussion on the lines provided. Decide which member of your group is going to report back your findings to the rest of the class.</li>
</ol>
<div class="exercises">
<div class="problemset">
<div class="entry"><div class="problem">
<p>Have a class discussion after you have finished discussing this in your group. </p><hr/>
<hr/>
<hr/>
<hr/>
<hr/>
<hr/>
<hr/>
<hr/>
</div>
<div class="solution">
<p>Learner-dependent answer</p>
</div>
</div>
</div>
</div>
<div class="teachers-guide">
<p>When groups are finished discussing their most important requirements, let groups share their lists with the other groups and have a class discussion. List their answers on the board and make a tick for each one that is repeated - for example Food/ Oxygen/ Water might be repeated so each time it repeats make a tick next to it. This way they will quickly be able to see which requirements are most commonly repeated in the class. Learners might identify 'Food' rather than energy. Remind them that they also have to think about the plants which do not need to eat food. So ask the learners what term they could use as a more general term for food? This links back to nutrition in the seven life processes. The answer is that living things need a source of energy. If learners do not come up with the fact that living things need 'favourable/good/optimal temperatures', ask them some leading questions such as: 'Do you think the space station needs to be heated or cooled? Why? Will
the humans and plants be able to survive at the temperature it is on the Moon? ' etc.
</p>
</div>
</div>
<p>Living organisms require certain conditions or things to be able to stay alive. We say that these things or conditions sustain life.</p>
<p>You would have discussed some of these requirements in the last activity. Did you come up with the same or similar requirements? Living organisms require the following to survive:</p>
<ul data-class="ListBulleted">
<li>energy</li>
<li>gases</li>
<li>water</li>
<li>soil</li>
<li>favourable temperatures</li>
</ul>
<p>Next, we look at these in a bit more detail.</p>
<p>
<strong>Energy</strong>: All living organisms need energy to stay alive and perform the life processes. Plants need energy from sunlight in order to photosynthesise. Other organisms get their energy from the food that they eat.
</p>
<figure>
<img src="images/gr7ll01-gd-0020.jpg" width="300"/><figcaption class="caption">All living things need a source of energy. The grass and trees get their energy from the Sun to photosynthesise. The cow gets its energy by eating the grass.</figcaption>
</figure>
<p>
<strong>Gases</strong>: All living things require oxygen for cellular respiration. Oxygen is used to release energy from nutrients and carbon dioxide and water is produced as a waste product of respiration. Green plants also need carbon dioxide to photosynthesise.
</p>
<div class="teachers-guide">
<p>Ask your learners what they think makes Earth's atmosphere unique. Answers: Our atmosphere contains the right gases to sustain life (ie. oxygen and carbon dioxide), our atmosphere also protects us from the harmful rays of the Sun (such as UV rays) by absorbing some of them.</p>
</div>
<figure>
<img src="images/gr7ll01-gd-0021.jpg" width="300"/><figcaption class="caption">All living things need oxygen to respire, such as this dog which is breathing air in through its nose.</figcaption>
</figure>
<p>
<strong>Water</strong> is vital to life. Every organism on our planet needs water to live.
</p>
<figure>
<img src="images/gr7ll01-gd-0022.jpg" width="300"/><figcaption class="caption">Water is vital for life on Earth.</figcaption>
</figure>
<div class="note col-md-6" data-type="didyouknow">
<p>When astronomers search for life outside of our solar system, they search for planets that might contain liquid water, believing that where there is water there may be life.</p>
</div>
<p>
<strong>Soil</strong> sustains life on Earth. Most plants depend on soil for support, minerals and water. Without the soil, plants would not be able to produce the food that animals and other organisms depend on.
</p>
<figure>
<img src="images/gr7ll01-gd-0023.jpg" width="300" alt="http://www.flickr.com/photos/87743206@N04/8053614949/"/><figcaption class="caption">Most plants need soil to grow in. </figcaption>
</figure>
<div class="note col-md-6" data-type="didyouknow">
<p>Not all plants need to grow in soil. Epiphytes, such as mosses and orchids, are a group of plants which grow on other plants or rocks. They get their moisture and minerals from the air and rain.</p>
</div>
<p>
<strong>Favourable temperatures</strong>: All organisms are adapted to live in a particular temperature. In general, our planet has favourable temperatures to support life. Earth is at an optimal distance from the sun so that it is not too hot, like on Mercury, and not too cold, like on Neptune.
</p>
<div class="note col-md-6" data-type="takenote">
<p>In Natural Sciences, when we use the word 'favourable' we mean something that is advantageous, helpful, or optimal. For example, we can talk about favourable conditions for life.</p>
</div>
<div class="note col-md-6" data-type="didyouknow">
<p>Every solar system has a 'Goldilocks' zone which is a region that is not too hot (close to the sun), and not too cold (far from the sun) to be able to sustain life. Earth is in the middle of our solar system's Goldilocks zone!</p>
</div>
<div class="note col-md-6" data-type="visit">
<p>
Read more about the 'Goldilocks Zone'<a data-class="ExternalLink" href="http://bit.ly/13ITCQU">bit.ly/13ITCQU</a> and <a data-class="ExternalLink" href="http://bit.ly/11OIY9R">bit.ly/11OIY9R</a>
</p>
</div>
<p>Let's find out what the requirements are to grow seedlings. We will learn how to conduct a scientific investigation to do this.</p>
<div class="teachers-guide">
<p>In previous grades learners were required to complete a similar investigation to determine the optimal requirements for seeds to grow. CAPS suggests that they do this activity again in order to reinforce the concept of the requirements to sustain life. Teachers should gauge how many learners did this particular activity in previous grades and should explain that this repetition is not so much to find out what requirements are necessary to sustain life, but to give them an opportunity to learn how to conduct a science investigation. This has therefore been included again as a very good opportunity (with learners already aware of the outcome) to review the scientific method and allow learners to practise this.</p>
</div>
<div class="note col-md-6" data-type="newwords">
<ul data-class="ListBulleted">
<li>dependent variable</li>
<li>hypothesis</li>
<li>independent variable</li>
<li>scientific method</li>
<li>variables</li>
</ul>
</div>
<div class="activity" data-type="Investigation">
<h1 class="title">What are the requirements to sustain life in plants?</h1><div class="teachers-guide">
<p>Start growing seedlings at the beginning of the term in the first lesson. A suggestion is to break the class up into groups and assign each group a different requirement to investigate. For example, one group should test whether water is needed, one group should test whether light is needed, one group should test the favourable temperature. Each group should also conduct a control so that they can all attempt to get seed to germinate.</p>
</div>
<p>In this investigation, we are going to germinate bean seeds (or any other seeds that your teacher provides you with). Each group in the class is going to be testing a different requirement for germination and growth of the seedling.</p>
<div class="note col-md-6" data-type="takenote">
<p>A hypothesis is an educated guess about what the outcome of the investigation will be. The hypothesis is stated before starting the investigation and must be written as a statementand must be in the future tense.</p>
</div>
<p>
<strong>AIM:</strong>
</p>
<p>A scientific investigation always has an aim or question that needs to be answered. What is the aim of this investigation? Write down what you aim to find out. </p><hr/>
<hr/>
<div class="teachers-guide">
<p>'To find out what plants need to grow'. (An aim MUST start with 'To find out / To determine / To see if .. etc. This is different from a scientific question like 'What do plants need to grow?')</p>
</div>
<p>
<strong>HYPOTHESIS:</strong>
</p>
<p>A hypothesis is where you propose (suggest) what the outcome of the investigation will be. It is a prediction of what the results will be. Write a hypothesis for this investigation. </p><hr/>
<hr/>
<div class="teachers-guide">
<p>Learner-dependent answer. The hypothesis should include a prediction about the need for soil, light, water and the favourable temperature. For example: 'The plant will grow best in full sunlight, less in the shade, and not at all in full darkness.'</p>
</div>
<p>
<strong>VARIABLES:</strong>
</p>
<p>
Scientists often use investigations to search for cause and effect relationships. This means that they design experiments to investigate how changes to one part will cause an effect on another. These changing quantities are called <strong>variables</strong>. There are usually three kinds of variables:
</p>
<ol data-class="ListEnumerated">
<li>
<strong>Independent variables:</strong> This is the thing that you are changing in the investigation. You are in control of the independent variable. For example, if you wanted to investigate if eating a lot of sugar makes you gain weight, then the amount of sugar you eat is the independent variable. You control how much sugar you eat. We want to achieve something called a FAIR TEST which means that only ONE independent variable is changed at one time. Once the independent variable has been changed the scientist then observes what the effect will be. In the example of investigating if sugar makes you gain weight, you cannot at the same time investigate whether exercise makes you lose weight. This would not be a fair test.
</li>
<li>
<strong>Dependent variables:</strong> The dependent variable is the thing that you observe in an investigation. You do not change it. The dependent variable will change depending on the independent variable. For example, in the investigation to see if eating a lot of sugar makes you gain weight, then the dependent variable will be how many kilograms you gain (or lose) as a result of eating sugar. How much weight you gain depends on how much sugar you ate. Dependent variables should be measured in an objective way using numbersas far as possible.
</li>
<li>
<strong>Controlled variables:</strong> These are the quantities that a scientist wants to remain the same or unchanged throughout the experiment. The controlled variable needs to be carefully monitored to make sure that it stays the same. In the example to see if sugar makes you gain weight, you could have one person eat a lot of sugar and the other person eat no sugar and then see the changes in weight. There are some things that need to stay the same for both of these people so that it is a fair test. For example, both people must do the same amount of exercise so that this does not influence their weight. This is a controlled variable.
</li>
</ol>
<div class="teachers-guide">
<p>Stress to the learners that dependent variables should be measured using NUMBERS as far as possible, as this leads to tables and graphs. They should avoid subjective evaluations like it 'looks good' or 'feels nice'. This is not science.</p>
</div>
<div class="teachers-guide">
<p>Ask learners if they can think of any other variables that need to be kept the same in this example. They might think of things like the starting weight of the people should be the same, they should be the same sex, same age, they should both be healthy and not sick etc.</p>
</div>
<p>You can also do a control test. For example, in this investigation about the growth of plants, you will be taking away one of the requirements for growth. You need to do a control test where another plant is given all the requirements, including the one you took away in the other plant. You can then compare your plant where you took one requirement away to the control plant which has that requirement to see if there is a difference.</p>