IBDP CORE>TOPIC 2>2.1 CELL THEORY
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ASSESSMENT STATEMENT2.1- CELL THEORY
2.1.1 Outline the cell theory. 2.1.2 Discuss the evidence for the cell theory. 2.1.3 State that unicellular organisms carry out all the functions of life. 2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses,bacteria, organelles and cells, using the appropriate SI unit. 2.1.5 Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification. 2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size. 2.1.7 State that multicellular organisms show emergent properties. 2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others. 2.1.9 State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways. 2.1.10 Outline one therapeutic use of stem cells. |
- students will watch the cell theory video and there will be class discussion that will lead to the outline ad evidences of cell theory. (2.1.1 and 2.1.2)
- watch video on amoeba biology and class discussion leading to stating that unicellular organisms carry out all functions of life. (2.1.3)
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2.1.3 State that unicellular organisms carry out all the functions of life.
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2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses,bacteria, organelles and cells, using the appropriate SI unit.
CHECK THIS SITE------SIZES OF CELLS
All organisms are made up cells that are tiny….visible only through a microscope They have different shapes and are of different sizes. Why do cells need to be small? What is the significance of cells taking different shapes? |
2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size. (ACTIVITY- LAB)
We perform an activity as shown in the video beside to find the importance of surface area to volume ratio for a cell.
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Pictures, the observation and conclusion by Heet Ghodasara and Jhanvi Kalaria
Solve the stencil given beside up-to question 11
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Surface area to volume ratio as a factor limiting cell size
1.As size increases both surface area and volume increase,
2.However volume increases more / ratio of surface area to volume decreases as size of cell increases; 3.Rate of metabolism is a function of its mass to volume ratio; 4.Surface area limits/affects the rate at which substances can enter (or leave) the cell; 5.Volume determines the rate at which material is produced/used; 6.Oxygen/nutrients/substances will take too long to diffuse into/out of the centre of the cell if it is too big; 7.Excretory products would take too long to be eliminated; 8.Heat will take too long to be eliminated; 9.Example of cell adaptation to increase the ratio of surface area: volume e.g. root hair cell; |
Why doesn’t the cells grow to a large size?
1.The larger the size the smaller the surface area to volume relationship;
2.If a cell becomes too large it cannot absorb oxygen / CO2 (in plants) fast enough; 3.If a cell becomes too large it cannot absorb foods / nutrients fast enough; 4.If a cell becomes too large it cannot excrete waste products / CO2 fast enough; diffusion in the cell becomes too slow; 5.Centre of the cell is too far from the membrane; nucleus cannot control a cell above a certain size; 6.Heat not lost quickly enough; 7.Not enough mRNA / proteins / enzymes produced; 8.Large cells may be structurally weak; 9.Cell wall / membrane provides support; 10.Larger blood cells would not fit through capillaries; 11.Sperm / large cells might not move quickly enough; 12.Having many small cells allows differentiation; |
2.1.5 Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification.
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http://www.youtube.com/watch?v=yf2oop3pbMY
Collect information on timeline of microscopy and prepare a presentation for the same. Include the differences between light and electro microscope It can be in any format a movie or prezi Time limit less than 4 mins. For the presentations check link… microscope presentations |
Light microscope
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Electron microscope
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LAB-2 CALCULATING THE LINEAR MAGNIFICATION
LINEAR MAGNIFICATION- FOR REFERENCE
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Stencil to be solved in class- The answers for these will be uploaded.
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2.1.7 State that multicellular organisms show emergent properties.
- Organisms can achieve more than the sum of what each part could achieve individually.
- Cells perform their task when they interact with each other rather than when they are alone.
2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.
Students watch the video and class discussion leading to cell differentiation
Differentiation is development in specific ways Cells carry out specialized functions Considering a differentiated cell in a multicellular organism- Cells have all genes so could develop in any way. Some genes are expressed but not others. The position / hormones / cell to cell signals / chemicals determine how a cell develops; A group of differentiated cells is a tissue |
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2.1.9 State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways. (ACTIVITY- DEBATE)
students watch the videos…..class discussion leading to what are stem cells?, where do we get stem stems from and what is its importance?
then have a debate in the class- "Embryonic stem cells- boon or bane."
then have a debate in the class- "Embryonic stem cells- boon or bane."
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RULES AND RUBRICS FOR THE DEBATE
Answer the following questions-
1. what are stem cells?
2. Mention the types of stem cells.
3. Why are embryonic stem cells preferred?
4. What are the limitations of using embryonic stem cells?
5. List some of the incurable diseases that can be cured with stem cells.
1. what are stem cells?
2. Mention the types of stem cells.
3. Why are embryonic stem cells preferred?
4. What are the limitations of using embryonic stem cells?
5. List some of the incurable diseases that can be cured with stem cells.
2.1.10 Outline one therapeutic use of stem cells.
- Stem cells are cells that retain the capacity to divide and have the ability to differentiate along different paths into all types of cells
- These cells are pluripotent/totipotent;
- Stem cells are derived from blastocysts/human embryos, left over from IVF/placenta/umbilical cord/some adult tissues;
- New techniques/technologies rely on replacing diseased/dysfunctional cells with healthy/functioning ones;
- Need to identify desired type of stem cell and grow in culture/special solutions/controlled conditions;
- Develop biochemical solution that will cause cells to differentiate into desired cell type;
- Develop means of implanting/integrating cells into patient’s own tissues so that they function with the body’s natural cells;danger of rejection of cells therefore need to suppress immune system;
- Must make sure new cells do not become overgrown/develop into cancerous tumours;
- E.g. retinal cells; replace dead cells in retina to cure presently incurable diseases such as glaucoma and macular degeneration;
- E.g. graft new skin cells; to treat serious burn victims;
- E.g. nerve tissue; help repair catastrophic spinal injuries / help victims of paralysis regain movement;
Stem cells can cause cancer.
Read the link …. How is the scientific community responsible for conveying information to the society.
Read the link …. How is the scientific community responsible for conveying information to the society.
References-
Damon, Alan et al, Higher level Biology for the IB diploma. Pearson Baccalaureate
Clegg, CJ, Biology for the IB diploma. London: Hodder Murrray, 2007, 978-0340926529
Taylor, Stephan, Science Video resources Wordpress,
Burell, John. Click 4Biology(online)
All picture have been downloaded from Google images for educational purpose only
Damon, Alan et al, Higher level Biology for the IB diploma. Pearson Baccalaureate
Clegg, CJ, Biology for the IB diploma. London: Hodder Murrray, 2007, 978-0340926529
Taylor, Stephan, Science Video resources Wordpress,
Burell, John. Click 4Biology(online)
All picture have been downloaded from Google images for educational purpose only