UNIT 1 LESSON 4 Specialised cells
Aims:
- To recognise that some living organisms are made up of only one cell but that others are made up of many cells.
- To recognise that in multi-celled organisms cells are adapted for certain functions and become specialised.
Learning objectives
Pupils should be taught
7 1/4a ways in which some cells, including ciliated epithelial cells, sperm, ova, and root hair cells, are adapted to their functions.
7 1/4b to relate cells and cell functions to life processes in a variety of organisms.
Activity 1 [Objective 7 1/4b]
Begin with a quick vocabulary test as a starter.
Read out the meanings and the students have to write down the key word. They get one mark for the correct word and a second mark if it is spelt correctly:
- surrounds the cell and controls what goes in and out – cell membrane
- controls the cell and contains instructions to make more cells – nucleus
- the jelly-like part of the cell where chemical reactions take place – cytoplasm
- found only in plant cells, these capture light energy and use it in photosynthesis – chloroplasts
- found around the outside of a plant cell. It is strong and supports the cell – cell wall
Activity 2 [Objective 7 1/4a]
Discuss the idea with pupils that the cells we have been looking at so far are generic (typical cells). Some organisms consist of only one cell .
There are many cells which contain all of the above, but have different shapes to help them carry out their functions.
Give out U1.4W1 Specialised cells sheet.
In pairs ask the students to match up the shape of the cell with its description. When they think they have done this ask them to check with another group sitting near them that they have the same answers and then draw diagrams and descriptions into their books. Use PowerPoint U1.4P1 for initial worksheet and answers.
Activity 3 [Objective 7 1/4a]
Pupils need to be taught about three other types of specialised cells: Use PowerPoint U1.4P1 for support.
Ova
Ciliated epithelial
Root hair cell
The ova is the cell with the largest volume in the human body. Its function is to produce new offspring. Introduce the discussion by showing the pupils a hen’s egg , crack it and show the contents. Point out the cell membrane which holds the contents of the egg together, the nucleus which is fertilised by the male sperm to form a new chicken (if it is visible), the albumen (egg white) which forms the cytoplasm. The ova is a specialised cell having its own food store in the yolk which is designed to provide nutrients for the growing embryo.
Relate this to the human ovum in the female body where the nucleus is also fertilised by sperm to form a baby, The cell is large as it has a large cytoplasm which is needed to help the ovum to survive until it is implanted in the uterus.
The ciliated epithelial cell is a surface cell having lots of tiny hair-like projections. Their job is to move substances within the body. They are found in the bronchus and the lungs where their function is to move mucous (which has trapped bacteria and dirt) out of the body. They are also found in the fallopian tubes where they move the egg from the ovary to the uterus. (Remind the students that a sperm is able to move itself, an egg cannot.)
Root hair cells can be shown to the students from a plant and using a magnifying glass. They are specialised in that their function is to transfer water to the plant, they therefore have lots of tiny hairs to increase the surface area to absorb more water.
Activity 4 [Objective 7 1/4a 1/4b]
U1.4W2 ‘Hairy Cells’ from 7a.4c Spectrum support pack PDF p37
Homework
This is a two week homework.
Pupils are to design and make a 3-d model of a cell. It could be a plant or animal cell and can be as imaginative as they like.
Examples:
Jelly with sweets in (in a rectangular box for plants; a plastic bag for animal).
A loaf of bread cut in half and filled with dried peas etc.
Wallpaper paste in bags or boxes.
Traditional cardboard box / paper models.
Resources: Lesson 4
Activity /Resources required
2 / U1.4W1 Specialised cells sheetPowerPoint U1.4P1
3 / PowerPoint U1.4P1
4 / U1.4W2 ‘Hairy Cells’ from 7a.4c Spectrum support pack pp37
Homework / Model making