1. Natural Sciences Grade 7
Term 1: Life and Living
The Biosphere
(PPT 1) Revision of Grade 6

2. Gr 7 Natural Sciences – Term 1, Topic 1
Topic 1 The Biosphere
The Earth
Gr 7 Natural Sciences – Term 1, Topic 1

3. Gr 7 Natural Sciences – Term 1, Topic 1
Earth
Third planet from the Sun.
Called ‘the blue planet’ [ocean water makes the Earth appear blue from space].
It has one moon.
It takes actually [365¼ = year] days to orbit the sun [results in leap year every 4th year with 29 days in February].
Gr 7 Natural Sciences – Term 1, Topic 1 3

4. Gr 7 Natural Sciences – Term 1, Topic 1
Earth
70% is covered with water.
It takes 23 hours, 56 minutes and 4 seconds to rotate on its axis. It is not actually round in shape; in fact it is geoid (Its rounded shape has a slight bulge towards the equator).
Gr 7 Natural Sciences – Term 1, Topic 1 4

5. Gr 7 Natural Sciences – Term 1, Topic 1
3% fresh water on Earth [2% is frozen in ice sheets and glaciers and only 1% water of the earth is fresh - in rivers, lakes and underground].
97% water is salted on Earth.
Tilts at roughly 66 degrees.
150 million km from the Sun.
Earth
Gr 7 Natural Sciences – Term 1, Topic 1 5

6. Gr 7 Natural Sciences – Term 1, Topic 1
Earth
Average temperature is 15 °C.
Atmosphere contains oxygen which animals breathe in and carbon dioxide which plants take in.
Gr 7 Natural Sciences – Term 1, Topic 1 6

7. Gr 7 Natural Sciences – Term 1, Topic 1
Earth’s Rotation
Turning of Earth on its own axis.
The Earth’s axis is tilted.
Causes day and night.
Takes the Earth 24 hours to rotate.
The rotation is like a wheel on a bicycle. It takes 24 hours for Earth to move around once (make a full circle). You could ask a learner to stand in front and in the same position slowly turn around starting and ending in the same position and explain it takes Earth 25 hours to do the same thing.
Gr 7 Natural Sciences – Term 1, Topic 1

8. Gr 7 Natural Sciences – Term 1, Topic 1
Earth’s Revolution
Earth orbits the Sun.
Earth takes 365 ¼ days to go around the Sun.
The revolution of the Earth around the Sun determines the seasons (summer, winter, autumn, spring).
Orbit is oval shaped.
Remind the learners that all the planets move around the Sun. Remind them from the first work they did that the planets all have different times to make one lap around the Sun. It takes one year (365 ¼ days). The year is divided into 12 months and the twelve months are divided into four seasons = summer, autumn, winter, spring. The next slide shows a position on the globe and how with the Earth revolving the seasons change.
Gr 7 Natural Sciences – Term 1, Topic 1

9. Gr 7 Natural Sciences – Term 1, Topic 1
Day and Night
The Sun gives off light and heat.
The Sun sets in the west and rises in the east.
Do the activity where they colour in where it is day or where there is night.
Explain that the side of Earth facing the sun is lit up and the side of Earth away from the Sun is dark (shadow) so it is night time. The next slides shows this. In other words only one side of the Earth gets light at a time.
Gr 7 Natural Sciences – Term 1, Topic 1