Multicellular Organisms

Multicellular Organisms Key Area 2.2 Stem cells and Meristems

Stem Cells Learning Intention: To learn about stem cells and how they are used for research and treating illnesses Success Criteria: Define the term ‘stem cell’ Describe the role of stem cells in animals Be able to describe the advantages and disadvantages of using stem cells for research and treating illnesses.

Think, Pair, Share • Have you heard of the term “stem cell”? • What do you know about them? • Discuss your ideas with your partner and be ready to share them with the class!

Stem Cells • Stem cells are found in animals. • They can divide to produce more stem cells or can develop into specialised cells. • Stem cells have the ability to turn into any type of body cell and are involved in growth and repair of body tissues.

Stem cell • Stem cell – a type of unspecialised cell that is capable of dividing into cells that can develop into different cell types. Twig Clip: Stem Cells

Types of stem cells • Scientists are researching treatments for certain illnesses that involve the use of stem cells. • There are two main types of stem cells: • Embryonic stem cells • Adult stem cells

(Image: Steve Gschmeissner / SPL) (Image: Miodrag Stojkovic/Science Photo Library) Coloured scanning electron micrograph of human embryonic stem cells

Embryonic stem cells • These are found in embryos. • Stem cells that come from embryos can develop into any type of body cell. • This allows the organism to grow from an embryo into a fully formed individual. • Research into the use of these cells is ongoing but there are ethical issues involved. • Scientists may now be able to use cells from placentas which are no longer needed.

Adults stem cells • Adult stem cells can be found among other specialised cells in a tissue or organ. • They have been found in tissues such as bone marrow, skeletal muscle, blood vessels, skin, liver, brain, heart and teeth. • Adult stem cells are like built-in repair kits, regenerating surrounding cells damaged by disease, injury and every day wear and tear.

Adult stem cells • Adult stem cells are found throughout the body. • Can be found in children as well as adults. • They do not have the same properties as embryonic stem cells as they are slightly more specialised.

Medical uses of stem cells Learning Intention: Learn about how stem cells are used and the ethical issues involved with their use Success Criteria: State the medical uses of stem cells Describe the ethical issues surrounding the use of stem cells Describe the advantages and disadvantages of using stem cells for research and treating illnesses.

Starter • What are stems cells? • Where are they found?

Medical applications Stem cells have important medical applications. Some of these include:

Future medical applications • In the future, scientists hope that stem cells will be used to cure conditions such as Alzheimer’s disease, diabetes, spinal-cord injuries and stroke. • Stem cells may also provide a useful alternative to animals for testing experimental drugs. Twig Clip: Uses of Stem Cells BBC Learning Zone: Stem Cell Research and Medicine

Stem cell debate • Read the article on the next slide before completing a table of advantages and disadvantages for the use of embryonic and adults stem cells. • Discuss your findings with the rest of the class.

Ethical issues with embryonic stem cells • Embryonic stem cell research gives us a moral dilemma. It forces us to choose between two moral principles important to humans. The first is the duty to prevent or ease suffering by doing all we can to improve medical treatments for illness. The second is our duty to respect the value of human life. • In the case of embryonic stem cell research, it is very difficult to respect both of these moral principles. • Embryonic stem cell research could lead to new medical treatments, which could save human lives and relieve human suffering. On the other hand, to obtain embryonic stem cells, an early stage embryo has to be destroyed meaning the loss of a potential human life. • Which moral principle should be followed in this situation? Does the answer lie in our attitude to the embryo – does it have the status of a person? • What do you think about this issue?

Adult Stem Cells Embryonic Stem Cells Disadvantages Disadvantages Advantages Advantages

First Task… Discuss your advantages and disadvantages to using embryonic stem cells for research.

Learning Outcomes • Practise discussing and debating issues and expressing an opinion. • Understand the arguments for and against the use of embryonic stem cells. • Consider social, ethical and factual issues in an integrated way. • Think about different points of view. • Learn to back up opinions with facts.

The key players:

Additional characters:

Read your card in your pair/group. • One person will read out the first section of the card to the class. • Class vote: for or against the statement. • Each group will then take it in turns to read out their fact from their character card. • Class vote: has anyone’s position changed? • Each group will then read the issue on their character card. • Class vote: any changes in the way people feel? • Class debate: A representative from each group will play the character of their card, using the questions from the bottom of the card to carry out a debate with the other characters. • Final class vote about the use of embryonic stem cells for research and which position they agree with the most.

Meristems Learning Intention: To learn about meristems and their role in plants Success Criteria: Define the term ‘meristem’ Describe the role of meristems in plants

Starter • Discuss with your partner- • Advantages and disadvantages of the use of stem cells.

Think, Pair, Share • What is ‘growth’? • How do animals grow? • At which points on their bodies do they grow? • How do plants grow? • Which parts of a plant can grow?

Growth • Growth is an irreversible increase in the number of cells in an organism. • This is usually accompanied by an increase in the mass of the organism. • Animals show growth all over their bodies. • Plants can only grow at special points called meristems. BBC Clip: Plant Growth Twig Clip: Human Growth

Meristems • Meristems can be found at the root tips and shoot tips of plants. • They are the only sites of cell division (mitosis) in plants. • Cell division produces non-specialised cells. • These cells have the potential to become any type of plant cell. • Cell division allows plants to grow.

Meristems • Meristem – a region of actively dividing cells in plants. • Meristems are growing points in a plant. meristem meristem root cap protects meristem

Root tip and shoot tip

Viewing Meristems Your teacher will provide you with some slides of plant material. Observe the slides under low magnification and then high magnification. Can you identify the meristems in the root tips and shoot tips?

Multicellular Organisms