Title: Cell Division-measuring growth
1Cell Division-measuring growth
- How would you measure growth?
- Write your answers on pupil white boards
2draw sketch graph for
human height against time
human mass against time
describe differences explain
3Cell Division-measuring growth
- Two methods to measure growth are height and
mass. - Other measurements of growth are cell
length number of cells dry mass - Dry mass is the mass of the organism after all
the water content is removed. It is found by
drying in an incubator until there is a constant
mass.
4Measurements of growth
Method Advantages Disadvantages
Cell length Easy to measure under a microscope Often irregular shape No reference to number of cells
Number of cells Good indication of overall size Difficult to count them all Doesnt take into account the size of cells
Dry mass Accurate indication of growth Time consuming Organism or part (e.g. leaf) is killed in process
name an organism which could be measured by each
method
5Questions
- Jane is 20 years old and has had her height and
mass measured at regular intervals over one year.
Suggest why her mass showed greater variability
than her height. - Suggest why organisms need to be dried until
there is a constant mass. - Explain why dry mass is likely to be a more
accurate measurement of plant growth than mass
without drying.
6Mitosis
- It is important that when cells divide during
growth that the new (daughter) cells produced
have the same genetic make up as the original
(parent) cell- they are clones of the parent
cell. - This means that they have the same number and
type of genes and chromosomes as the parent cell. - This type of cell division is known as mitosis.
7- Chromosomes make an identical copy of themselves
before the cell divides. - The copies are called chromatids and are held
together at the centromere.
8centromere
chromatid
chromosome
chromosome
9Mitosis
- Mitosis is the type of cell division used in
- Growth
- Replacing worn out cells
- Repairing damaged tissue.
103. Chromatids in each chromosome separate are
pulled to opposite ends of the cell by spindle
fibres
2. Chromatids line up along the centre (equator)
of the cell
by spindle fibres
1. Each chromosome replicates into 2 identical
chromatids held together at the centromere
4. Once chromatids reach the opposite ends the
cell divides in 2
5. The 2 new cells contain exactly the same
chromosomes as each other and the parent cell
11Mitosis Hand jive-start at 23 seconds
12Asexual Reproduction in Plants
- This produces genetically identical offspring.
- Cells from the parent plant reproduce identical
copies of themselves. - An example is strawberry runners producing new
plants. - Because the new plants are genetically identical
to the parent they are called clones.
13Propagation of Strawberry Plants
New strawberry plants developing from buds on the
runner. Each plant is genetically identical to
the parent.
Parent plant
The runner provides food reserves that allow the
new plants to become established.
14Taking Cuttings
- The use of cuttings is a form of cloning that is
often carried out by gardeners to make larger
numbers of identical plants
15Taking Cuttings
Dip cutting into compound that contains hormones
to stimulate root growth
Place in compost until established
Cut a section with a few leaves
16Activity
- Take your own plant cuttings from a geranium
plant and pot them up! - Think about what apparatus you will need and plan
how you will carry this out.
revise from y11 1.6 coordination in plants
17Tissue Culture
- This is a type of cloning that can be carried out
all year round in a lab. - It must be carried out by scientists in sterile
conditions producing disease free varieties - This is used to conserve very rare plants, e.g.
orchids
18sterilise in dilute bleach to kill bacteria
fungi
containing glucose for respiration N to make
amino acids
Control temperature pH
19Advantages of Plant cloning
- Only plants with desirable qualities are
produced. - It is a quick process producing lots of plants
20Disadvantages of Plant cloning
- The lack of variation means that all plants may
be equally susceptible to disease or have other
weaknesses.
21Twitter-see booklet
22Cancer
Cancer is produced by uncontrolled cell division.
23Some causes of cancer
- UV radiation- this is produced from the sun or
sunbeds and causes skin cancer. - Chemicals in cigarette smoke namely TAR can cause
lung cancer. - Viruses eg Human papilloma virus which can cause
cervical cancer.
24Skin Cancer
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26A cancer causing virus
27DNA
28- Abnormal cells
- may vary in size
- may have several nuclei
- may be unspecialised in shape and function
- may have irregular, thickened and enlarged
nuclear membranes - may contain chromosomes that stick together
29Cancer cells grow in clumps called TUMOURS
30- Benign tumours
- Enclosed in a capsule and dont invade
surrounding tissue - Remain in one place
- Resemble the tissue from which they arise
31Malignant Cancer
Malignant tumour
Lymphatic vessel
Malignant cells
Blood vessel
32- Malignant tumours
- Can grow into the surrounding tissue
- Cells may break off from the main tumour and
spread around the body. - Do not resemble cells around them.
- Are arranged in a haphazard irregular fashion
33The cells of a malignant tumour can be carried to
other parts of the body in the blood or lymphatic
systems THEREFORE The cancer can spread and
new tumours can grow in different parts of the
body
34The importance of detecting cancer early
- If a cancer is detected early the tumour will be
smaller and will have caused less damage to the
body. - It is also important to detect a malignant tumour
before it spreads to other parts of the body. - Therefore early detection improves survival rates.
35Screening programmes
- These programmes aim to identify the cancer
before it spreads too far. - These are available to detect breast, cervical,
skin and testicular cancer.
36Treating Cancer
- Once cancer has been identified there are a
number of treatment options - Surgery-cancer is removed from the body
- Radiotherapy
- Chemotherapy
37Meiosis
- Meiosis is another type of cell division
- It occurs in the testes and ovaries to produce
sperm and eggs(gametes). - The purpose of meiosis is to produce gametes with
half the number of chromosomes of all the other
cells in the body. - As meiosis halves the chromosome numbers in the
daughter cells it is also known as reduction
division.
38- Most human cells have 46 chromosomes arranged in
23 pairs. - Sperm and eggs produced by meiosis have only 23
chromosomes. - It is not just any 23 chromosomes from the 46 but
one chromosome from each pair that passes to the
sperm or egg.
39What are the possible different chromosome
combinations?
40- It could be either chromosome of a particular
pair that passes into the sperm or egg. So there
are millions of potential chromosome combinations
223 possibilities. - This random independent assortment of chromosomes
in meiosis at gamete formation gives unique
gametes helps produce variation in offspring.
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42Haploid and diploid
- The chromosome number in the gametes is termed
the haploid number (23 in humans). - The normal number in and organism is termed the
diploid number (46 in humans). - Therefore fertilisation restores the diploid
number in the offspring and combines the
different arrangements of chromosomes produced
during meiosis.
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44Mrs Monroes Hand Signals
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46Design a Poster to illustrate differences between
mitosis and meiosis
47Tracking test