Natural Sciences Grade 7 Term 1 Life and

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

Topic 1 The Biosphere The Earth 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 365. 2564 [365¼ = year] days to orbit the sun [results in leap year every 4 th year with 29 days in February]. 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

h t r Ea • 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. 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

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. 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. 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. Gr 7 Natural Sciences – Term 1, Topic 1