Unit 6L.1: Cells. All living organisms are made of cells. A collection of specialized cells makes tissues.

Transcription

1 Unit 6L.1: Living things are made of Specialized cells Tissues and Organs Cell Division By the end of this unit you will know: All living organisms are made of cells. A collection of specialized cells makes tissues. Organs are made up of tissues of different types. Living organisms are made of many organs that have different functions. 1

2 6.5.1, Living things are made of cells All living things are made up of small parts called Organs. These organs are made up of lots of even smaller bits called cells. The cells are the building blocks of all living things Some organisms such as BACTERIA are made up of only one cell. Large organisms like mice and insects are made up of many cells. A human for example is made up of trillions of cells Do you know how man zeros in a trillion. Can you imagine how many cells a whale must have?!!!!! 2

3 are very small. You need a microscope to see them. Microscopes make things look a lot bigger. We say that they magnify them. (Look at box 1 on Page 4). If you magnify cells a hundred times or more, you can even see the smaller parts inside them. The Microscope was invented in the 16 th century, but it was not until 1665 that a Scientist called Robert Hook published a book that showed drawings of a part of plant he had seen under the microscope. He called the tiny boxes he had seen because they reminded him of the small rooms (cell means little room in Latin). Hook microscope The Cell Theory: Matthias Schleiden in 1838 and Theodor Schwann in 1839 realized that all plants and animals were made up of cells. The Cell theory changed the way that Scientists thought about living things for ever. 3

4 You must handle the microscope with care. It is delicate and very expensive! Follow you teacher s instructions before using it! Life Science Eye Lens Optic tube Arm Objective Lens Stage Coarse Focus Fine Focus Light Base 4

5 UThe light microscope The Microscope is an instrument used to magnify the tiny things. Look at the picture (on page 4) and identify the main parts of the microscope. Read them out to yourself. Notice that it is made of 2 lenses: The eye piece lens and the objective lens. The total magnification= Magnification of the eye lens x Magnification of the objective lens The eye piece lens is usually (*10) There are three Uobjective lenses (that rotates round)u: - (x4),(x10), (x40) The highest magnification in this microscope is (10x40) = 400 times the size! Do you know what this is? It has been magnified 400x! Rewrite the words below in reverse and find out: The first word has been done for you in red... GEL FO A OTIUQSOM LEG 5

6 ULet s see what a cell from your body looks like. Activity: You will need the following: A microscope. A cotton bud. A dropper with water. A glass slide and a cover slip. A Methylene Blue stain. What you should do: 1. Put a drop of water on the centre of a glass slide. 2. Gently wipe the inside of your cheek with the cotton bud. 3. Put the end of the cotton bud on the drop of water. Stir a few times. 4. Add a drop of stain. 5. Hold the cover slip by its edges. Hold it at one end of the slide (look at the picture below). 6

7 6. Slowly move the cover slip until it is over the water. 7. Carefully drop the cover slip. 8. Put the slide on the microscope. Turn to a low magnification. Look into the lens. Focus it. What do you observe? (You should see many purple dots. They are cheek cells!) 9. Draw what you see in your notebook. 7

8 You should see something like the following under a low magnification (Fig.1). If you can put it on high magnification you should see something like (Fig.2). Fig.1 Fig.2 UWhat do cells look like? UPlant cellu UAnimal cell are made of lots of different parts. Each part has a different job to do, to keep the cells alive and working. 1. UAnimal cellu: Most cells have the same basic structure. The cell itself is made of smaller parts. Most cells have three main parts: 8

9 Cell part Cell Membrane Nucleus Function controls what passes in and out of the cell controls what happens in the cell. Cytoplasm which is a jellylike material made mostly of water that fills the space in the cell. Cell membrane Cytoplasm Nucleus Animal cell 9

10 2. UPlant cellu: Plant cells have the same parts as animal cells. They also have certain parts that animal cells do not have. These extra parts are: Cell part Cell wall Chloroplasts A large Vacuole Function outer skeleton of the plant contains the chlorophyll. a store of water in the plant cell. Nucleus Large Vacuole Cytoplasm Chloroplast Cell Wall Cell membrane Plant cell 10

11 Activity: Preparing to look at onion cells under a microscope. Follow the directions: (Note: Onion cells do not have chloroplasts. If you want to look at them, find a moss plant.) 1. Cut out a small piece of onion. 2. Use forceps or your finger nails to peel off the inner surface (this looks like tissue paper). 3. Put the piece of onion skin flat on a slide and add 2 drops of iodine solution. 4. Gently lower the cover-slip onto the slide using a mounted needle. 5. Place the slide onto the stage of the microscope. 6. Focus carefully onto the onion skin using the lowest power objective lens in your microscope. 7. Turn on the high power objective lens to see details of the onion cells. 11

12 Key words: Nucleus Cell membrane Cytoplasm Cell Cell wall Chloroplasts A large vacuole. Key ideas: All living things are made of tiny bits S called All cells have: o Nucleus o Cell membrane o Cytoplasm Plant cells also have: o Cell wall o Chloroplasts o A large vacuole. are too small to be seen by naked eye. So we need a microscope that magnifies them. Project: Use the following materials to make a model of a plant cell: Material A plastic jar A small plastic bag A large plastic bag A balloon modelling clay Sand + water Cell part 1. Plan your project by deciding on what will represent the cell parts 2. Make the model - label each part so it is clear, don t forget to write your name! 12

13 Key Questions: Q(1) Complete the following gaps : 1-All plants and animals are made up of tiny units called. 2- A which controls what happens in the cell. 3- is made mostly of water that fills the spaces in the cell. 4- A that covers the cell and controls what goes in and out of the cell. Q(2) Can we use a magnifying lens to see the cells? Explain your answer Q(3)Using Venn diagram compare between the parts of Animal and plant cell? Q(4) Draw Animal cell and label all parts? 13

14 6.5.3 Life Science Specialized cells Large organisms have millions of cells of different types (multicellular organisms). These cells are different from each other because they have their own jobs to do. Specialized cells: that have different shapes and do different jobs Animals and plants are large living organisms. They need food, they need to breathe and move. To do all these jobs they need millions of specialized cells. 14

15 Activity: Looking at pre-prepared slides 1. Use the microscope to look at two different animal cells, and two different plant cells. 2. Make sure to look for the main parts of the cells. (Nucleus, Cell Wall, Shape, Cytoplasm, Vacuole) 3. Make a table, draw what you see for each slide and tick off the parts you can see, so that you can compare. Animal Cell Plant Cell Slide 1 Slide 2 Slide 1 Slide 2 What did you see? Draw a sketch here Nucleus Yes / No Yes / No Yes / No Yes / No Cell Wall Yes / No Yes / No Yes / No Yes / No Cytoplasm Yes / No Yes / No Yes / No Yes / No Vacuole Yes / No Yes / No Yes / No Yes / No 15

16 Some examples of specialized cells and their functions are shown in the following table: Cell Function Special characteristics Animal Muscle cells Contracts so that we can move Has fibres that can become short or long to help in movement. Sperm cells Fertilization (from male) Has a tail to swim Nerve cells Plant cells Conducts nerve impulses (messages from and to the brain) Has a long fibre that can reach 2 meters Palisade Xylem and phloem Catch the light Transports water and nutrients Has a large number of Chloroplasts. - Tube like cells to carry water and nutrients. - Xylem cells have no cytoplasm 16

17 Key Words: Specialized, Palisade cells, Xylem and Phloem. Sperm, muscle, nerve cells. Project: Find the function of the following specialized cells: Make a poster and comment on the: shape, what it does, where you find it. Egg cell Root hair cell Red blood cell Key ideas: Large living organisms have millions of cells that have different functions and different shapes. These cells are called Specialized. Muscle, nerve and sperm cells are examples of Specialized animal cells. Xylem, Phloem and Palisade cells are examples on specialized plant cells. 17

18 Key Questions: Q (1): Put (T) if the statement is true or (F) if the statement is false: 1- Sperm cells have fibres that can become short or long to help in movement ( ). 2- Xylem cells have no cytoplasm ( ). Q (2): Look at the pictures and answer the following questions: A B 1- Write the name of cell (A)? Write the function of cell (B)? What characteristic does picture (A) help to movement? 18

19 6.5.4 Life Science Tissues and Organs One Xylem cell will not be able to carry water and nutrients to the whole plant. One muscle cell will not be responsible for the movement of your whole body. Specialized cells have to work together to do the job. A collection of cells with the same shape and function is called a Tissue. All the cells in a UtissueU look the same and do the same job. For example: Your Umuscle tissueu is made of identical muscle cells. 19

20 Activity: You can see what a tissue looks like: Get some raw hamburger meat (it is muscle tissue that looks a lot like muscle tissue that is in the human body). Materials: Microscope, a dropper with water, a glass slide and a cover slip. What you should do: 1. Put three drops of water on the slide. 2. Put a cover slip over the hamburger. 3. Put the slide under the microscope. You should see tissue ( that look alike). Draw what you see. 20

21 Examples of Animal tissues: Example picture Muscle tissue Epithelial tissue (on the skin) Brain tissue Blood tissue Nerve tissue 21

22 Examples of plant tissue: U1.Stem tissue This is how a part of the stem looks like under the microscope. Notice the Xylem and Phloem cells that have the same shape and same function. U2.Leaf tissue: Palisade cell 22

23 Organs: Like plants, our body has many different parts called Organs. Different organs in our body do different jobs. An organ is made up of different tissues that work together to do a particular job. An organ is a body part made of different tissues that work together to do a particular job. Examples of organs: Your heart is an organ. It is made of different tissues that work together to pump blood around your body. Your stomach is an organ; it helps your body break down your food. 23

24 The stomach is made of many tissues shown in the following picture. It is made of layers of different tissues like a hard boiled egg you can peel the layers off and see them! Other examples of organs are lungs, livers, leaves and stems. 24

25 This picture shows how organisms are made, you can see that the cells, are the building block for the living organisms, then groups of cells together form a tissue. A tissue is a group of similar cells that work together to do one job. Each cell in a tissue does its part to keep a tissue alive. Tissue organized into organ, different organs make organ system. Cell Tissue Organ Organ system Organism. Project: 5 tissue types in your body are: connective, muscle, nervous, and epithelial. Make a poster, explaining what jobs they do and why they are so important. 25 Here is an example.

26 Key words: Specialized cells Collection Tissue Organ Key Ideas: - A tissue is a group of cells that look alike and work together to do a specific function. - An organ is made of many layers of different tissues. Key Questions: Q(1) : complete the following gabs : The different parts of your body are called A group of specialized cells that work together are called Q(2): Sort these lists into the correct sequence of cells, tissue, organ, organism: a. Heart, muscle, human, muscle b. Shark, nerve, eye, retina Q(3) : List three organs in plants

27 6.5.5 Cell Division How do living things change so much as they grow? A bird starts out in a hard shelled egg you can hold in your hand. How does it end up as an eggle made of billons and billons of cells and covered with feathers? What happens when you grow? Do cells get bigger or do they increase? where do new cells come from? Cell Division are basic units of living things. Most of the organisms such as dogs, cats, birds and trees made of many cells. When the cells of these organisms divide, they do not separate. The cells stay together and keep on dividing. As the cells divide, the organisms grow and changes. 27

28 A single bird or tree is made up of billions of cells. Your body has billion of cells too. All the time you are growing, your body's cells are dividing. Notice how much the child in the picture has grown. Your cells will keep on dividing, even when you stop getting bigger and taller. Your body need to make new cells because the new cells replace old cells that wear out or die. How cell division happened? When a cell starts to divide,it make a copy of all its part After the cell divides,the new cells will have parts that are identical to the ones the original cell had. The information that a cell needs in order to control all its acivites is stored inside 28

29 the Ucells nucluesu. This information is located in a set called chromosomes. Look at the picture of the dividing cell. 29

30 Sequence of cell division: 1-Chromosomes are copied First, the cell copies its chromosomes. It makes two complete sets. 2- Chromosomes line up The two set of chromosomes line up in the canter of the cells. 3-Chromosomes separate Then the two sets of chromosomes separate each set moves toward on opposite side of the cell 4-Chromosomes Divide Finally, the cytoplasm divides, formatting two new cells. 30

31 Key words: Cell division Chromosomes Key Ideas: - As the cells divide, the organisms grows and changes. - Even when you stop getting bigger and taller. Your body need to make new cells because the new cells replace old cells that wear out or die. Key question 1- Why is cell division important? 2- Draw and describe how cell divide in the space below? 31