Content. Natural Science and Technology Grade 5. Term 4 Planet Earth and beyond and Systems and Control. Topic 14 Plant Earth Unit 1: The Earth moves

Transcription

1 Natural Science and Technology Grade 5 1 Term 4 Planet Earth and beyond and Systems and Control Content Topic 14 Plant Earth Unit 1: The Earth moves Topic 15 The surface of the Earth Unit 1: Rocks Unit 2: Soil comes from rocks Unit 3: Soil types Topic 16 Sedimentary rocks Unit 1: Formation of sedimentary rocks Unit 2: Uses of sedimentary rock Topic 17 Fossils Unit 1: Fossils in rock Unit 2: Body and trace fossils Unit 3: Importance of SA fossils

2 Topic 14 Planet Earth 2 Unit 1 The Earth moves Key Words revolution the movement of an object in space around another object, such as the movement of the Earth around the Sun axis an imaginary line passing through the centre of an object rotation when something turns in a circular movement around a central point such as the Earth around its own axis How the Earth moves The Earth moves, through space, around the Sun. It travels quickly through space and follows a distinct pathway. This pathway around the Sun is called an orbit. When an object moves around another object in space, the movement is called a revolution. The blue arrows show the Earth s orbit

3 3 Did you know? It takes the Earth about 365 days to travel once around the Sun at a speed of about km per hour. That is about 30km in 1 second. Even at this speed it takes the Earth about 365 days to revolve around the Sun once. The Earth spins The Earth spins on its own axis on an imaginary line. This is similar to an apple spinning on a stick. The spinning takes place between the North and the South Pole. The spinning of the Earth on its axis is called a rotation. It takes the Earth 24 hours (one day) to complete a full rotation.

4 4 Topic 15 The surface of the Earth Unit 1 Rocks Key Words Crust - the thin layer of soil and rocks on the surface of the Earth. Soil, air, water and sunlight support life on Earth All living things need the following to survive: a. Soil for plants to grow. b. Air to breathe. c. Water to drink and make plants grow. d. Sunlight, for energy, so that plants can make food for themselves.

5 5 Plants need soil, air water and sunlight Plants are able to make their own food, using nutrients and water in the soil, carbon dioxide from the air and sunlight. Without the food they make, plants would not be able to survive and grow. Most plants also need soil to anchor their roots in the ground. Animals need soil, air, water and sunlight Animals breathe in oxygen from the air and drink water to live. Energy that is needed for their life processes comes from the food they eat. This energy passes up the food chain from plants. All animals depend on plants for food (directly or indirectly). This means that animals also depend on soil, air, water and sunlight that plants use to make food. Unit 2 Soil comes from rocks Key Words topsoil the top layer of soil decompose break down into smaller parts fertile soil soil in which plants flourish and grow well nutrients substances that organisms need to grow and be healthy subsoil - the soil layer below the topsoil bedrock the solid rock below ground, found under the soil humus - soil made of decayed plants, leaves etc. that fertilise growing plants Over millions of years, rocks are worn away by natural elements such as wind and water. These rocks break down into smaller and smaller pieces and eventually grains of sand are formed. Picture A Picture A, illustrates the different soil layers. The top layer of soil has a darkish colour and is called topsoil.

6 6 Topsoil forms very slowly because it is made of the smallest pieces of rock. Topsoil contains lots of nutrients and this makes the soil very fertile. The rotting plants and animal matter in this layer is called humus. The layer under the topsoil in called subsoil. Sub means under. When it rains, the nutrients from the topsoil are washed into the subsoil. Plant roots can also get nutrients from this layer, although it is not as nutrient rich (fertile) as topsoil. A layer of broken pieces of rock (rock fragments) mixed with soil is found below the subsoil. These weathered rock fragments form the next layer of soil. The next layer of soil is the solid rock of the Earth s crust. This is called bedrock. SOIL SUPPORTS LIFE ON EARTH Soil provides plants with nutrients and water. Plants then provide food for plants. Soil is the habitat of many different animals.

7 7 Unit 3 Soil Types Key words microscope - an instrument that makes small things appear much bigger coarse grains - large soil grains fine grains - very small soil grains eroded soil - is soil that has been washed away by water or blown away wind sandy soil - a rough, gritty soil that is mainly made up of sand clayey soil - a smooth or hard soil that is mainly made up of clay loamy soil - is a mixture of sand, clay and humus proportions - parts that make up a whole, the relationship between two things in size or amount compost - rotting plant animal material organisms - animals, plants, humans, all living things When a rock breaks up, it becomes grains of sand. These grains are different sizes and have different names. Large grains are called sand grains and small grains are called clay grains. Clay grains are only visible under a microscope. Large grains are called coarse grains. Small grains are called fine grains.

8 8 We can divide soil into three main types, depending on the proportions of the different sized soil grains. There are three main types of soil: A. Sandy soil B. Clayey soil C. Loamy soil Sandy soil Sandy soil has a high proportion of large coarse grains of sand in them. Sandy soil has a rough, gritty texture when you rub it with your fingers. Clayey soil Clayey soil contains a high proportion of fine grains of clay. Clayey soil has a smooth, sticky texture when it is wet. Clayey soil forms very hard lumps when it is dry.

9 9 Loamy soil When soils are a mixture of sand, clay and other soil grains we call them loamy soils. Loamy soils have a crumbly texture when you rub them between your fingers. When terrestrial (living on land) plants and animals die, their remains mix with the soil. This material rots or decomposes to form compost. Dead plants and animals form compost This compost mixes with the soil and eventually becomes a fine dark mixture. This material is called humus. Humus is very beneficial to soil.

10 10 Loamy soil has plenty of humus in it. Humus makes loamy soil light and nutrient rich. Plants grow best in rich, fertile loamy soil. Soil has air, water, and organisms in it Dry soil has air in the spaces between the grains. When the soil gets wet, water fills these spaces. Water sometimes sticks to the soil grains. Organisms that live in the soil use the air and water in the soil to live, grow and survive. Most plants take in water and nutrients from the soil through their roots.

11 Topic 16 Sedimentary rocks 11 Unit 1 Formation of sedimentary rock Key words sedimentary rock - is made from layers of sand, gravel and other materials that have been deposited, compacted and hardened to form rock deposit - drop or put down in a certain place sediments - soil and pieces of broken rock deposited by a river or by wind contract - to become smaller or narrower shale - a kind of sedimentary rock made of clay sandstone - a kind of sedimentary rock made of sand limestone - a kind of sedimentary rock made from shells and bones of tiny sea animals Sedimentary rocks are layers of material that have been deposited and have been pressed together very hard. They are formed over a very long time. Sedimentary rock forms in the following ways: 1. Rock breaks down into small grains Over a long time, rock breaks down into smaller pieces called grains. The rock breaks down for various reasons. The roots of plants grow into the cracks of rocks, splitting the rock as they grow bigger. Chemicals found in the air, as well as water, can cause the rock to weaken and become brittle. The process of the rock breaking down takes thousands of years until the rock is broken down into small grains.

12 12 2. Mud and sand are moved by wind and water Grains of rock do not stay in one place but are moved around by wind and water. Fine grains of clay form dust when it is dry and mud when it is wet. Dust and sand can be carried away by wind. Sand and mud can be washed away by water flowing over the surface of the Earth after it has rained. 3. Mud, dust and sand are deposited in low-lying areas Loose grains of sand are blown away by the wind and washed away by rain water. Rivers pick up mud and sand and carry them to low-lying areas. When the rivers get to low-lying areas, near the sea, they begin to flow more slowly. The river drops or deposits the mud and sand. These deposits collect year after year in layers. These layers are called sediments. 4. New layers of mud and sand are deposited on top of existing layers that have become compacted When the rivers reach the sea or a lake they cannot carry sand and mud any further, so they deposit this material. The deposits settle into layers and compact as the grains move closer together. More material is deposited on top of the compacted material. This forms new layers. The new layers push down on the old layers to make them compact further. Over a very long time these layers harden into sedimentary rock.

13 13 Examples of sedimentary rock SHALE Some sedimentary rock is made of mud or clay. The mud and clay compact into very thin layers. It feels smooth and flakes easily. SANDSTONE Some sedimentary rock is made almost entirely of sand. You can see the grains of sand in the rock.it feels very rough and is very hard. LIMESTONE Limestone does not form from pieces of broken rock. It is made from the remains of dead sea creatures. Their shells and bones collect on the sea floor and, over time, harden into a layer of rock. Most of these animals are very small and their remains are so broken that you cannot see them in the rock. Limestone is white because the shell in it is made of the same substance as chalk.

14 14 Unit 2 Uses of sedimentary rock Key words cement - something that hardens to act as a adhesive material quarries - places where stones and sand are dug out of the ground kiln- a furnace or oven for burning, baking or drying something Limestone Cement is made from limestone. People dig limestone out of quarries. The limestone is crushed and mixed with small amounts of clay. The mixture is heated to almost 1500 o C in a special oven called a kiln. The powder is then packed into bags. Glass is made from molten (melted) sand. Limestone is mixed with the melted sand to make the glass stronger. Farmers use limestone to improve the fertility of soil, if the soil is too acidic. Limestone is even used in some medicines and cosmetics and as a white pigment in toothpaste, paints and plastics.

15 15 Sandstone Sandstone is a popular building material. It is used to make slabs and tiles for walls of buildings and for floors. Because sandstone is easy to carve, but does not weather quickly (wear out or look old), it is often used for paving stones to make walkways. Shale Shale is used as one of the raw materials needed to make bricks. Shale also splits very easily into thin sheets and is therefore often used as a tile for floors and roofs.

16 16 Topic 17 Fossils Unit 1 Fossils in rocks Key words fossil - the remains or signs of ancient plants and animals preserved in rock ancient - from a very long time ago preserved - something that does not rot extinct - when things die out and no more are left palaeontologist - scientists who study fossils fossil record - the information collected from fossils about life long ago Fossils found in rock The remains of ancient plants and animals that lived millions of years ago are called fossils. These fossils are preserved in layers of sedimentary rock.

17 17 Fossils in sedimentary rock Fossils are found in sedimentary rock. When plants and animals died, billions of years ago, they were buried in the mud. Their bodies were covered by more layers of mud, and over many years, the mud turned to rock. The remains of animals and plants in these layers of rock became fossils. The fossil record Fossils are evidence that life existed on Earth billions of year ago. A fossil record is the information that has been collected from fossils. Scientists, called palaeontologists, study fossils to find out what plants and animals were like millions of years ago. Most of the plants and animals are extinct (no longer in existence) and we only know about them because of the very small number of fossils that people have found. Most of these organisms lived on Earth long before the first humans.

18 18 Unit 2 Body and trace fossils Key words body fossils - the hard parts of plant and animal bodies such as bones, that have been replaced by minerals to form fossils trace fossils - fossilised signs of anything that is left behind by an animal such as footprints There are two main types of fossils: Body fossils Trace fossils Body fossils Body fossils are the actual/real preserved body part of a plant or animal. This could include bones, teeth, shell, leaves, stems and seeds. The soft body parts, such as muscles and skin rot away or are eaten by other animals. Body fossils tell us about the plant or animal s body structure. Trace fossils

19 19 Trace fossils are preserved signs of animals. They are not remains of a plant or an animal s body. Fossil footprints, nests, eggs, burrows and droppings are trace fossils. Trace fossils give us information about how the animal lived. Droppings, for example, can tell us what the animal ate and footprints tell us if the animal walked on two or four legs. Unit 3 The importance of South African fossils Key words arthropod - an animal with a hard outer covering coelacanth - large bony marine fish with three lobed tail fins and paired fins archaeologist - people who study ancient societies by looking at their remains dinosaurs - a group of reptiles that first appeared on Earth about 225 million years ago

20 20 Many fossils have been discovered in South Africa. These include fossils of plants, animals and early human beings. Some fossils were the first organisms that appeared on Earth. There are a lot of fossils in the Karoo. Arthropod fossils have also been found in South Africa. Arthropods are animals that have a hard outer covering. Insects, crabs, crayfish and spiders are all arthropods that are alive today. Fossils of early mammals have been found in various parts of South Africa such as Langebaanweg, in the Western Cape, and Sterkfontein, in Gauteng. Image of the Sterkfontein caves in Gauteng

21 Coelacanths The fossil record shows that the Coelacanths date back to more than 360 million years ago. When they stopped appearing in the fossil record 80 million years ago, it was believed that they had become extinct. Then, in 1938, a Coelacanth was caught off the coast of South Africa, near East London. This caused much excitement, as it was almost identical to Coelacanths that lived millions of years ago. The Coelacanth is often called a living fossil because it has changed very little from the fossil Coelacanths that lived millions of years ago. More were discovered in Isimangaliso National Park in the year African dinosaurs About 225 million years ago, dinosaurs first appeared on the Earth - they were land reptiles. They became extinct about 65 million years ago. The illustration is an example of a dinosaur called Euparkeria that archaeologist found near Aliwal North in South Africa. It was about the size of a cat and lived about 200 million years ago. Stegosaurus dinosaurs lived in South Africa about 125 million years ago. Fossils of these huge dinosaurs have been found near Bushman s River in the Eastern Cape. They were herbivores, about 5m long and 2m tall.

22 Checke The Cradle of Humankind The Sterkfontein Caves are situated about 40km away from Johannesburg. The fossils that have been found in the caves are assumed to be evidence of the world of early humans. The area has been named the Cradle of Mankind. These caves are a World Heritage Site. This means that it is recognised by the world as an important site and is highly protected. In 1947, Dr Robert Broome and John Robinson found the skull of an adult Australopithecus and named it Mrs Ples. (It is believed that the Australopithecus walked upright, like a human) In 1998, Dr Ron Clarke, Nkwane Molefe and Stephen Motsumi discovered the first example on an entire skull and its skeleton, from our early ancestors. It is over 4 million years old. Some foot bones had been discovered in the 1970 s and 28 years later the rest of the skeleton was discovered. It was called little foot. Bibliography: Platinum Natural Sciences and Technology- Maskew Miller and Longman Day by Day Natural Sciences and Technology- Maskew Miller and Longman Thunderbolt kids Natural Science and Technology- Dept of Basic Education Checked GM 2016