1. Cell Division allows for reproduction and growth of organisms.

2. Learning Outcomes
state that mitosis occupies only a small percentage of the cell cycle and that the remaining percentage includes the copying and checking of genetic information

3. Chromosomes Are found in the nucleus of eukaryotic cells
Are made up of DNA and histone proteins
Hold instructions for making new cells
Specific lengths of DNA are called genes
The number of chromosomes in each cell is characteristic of each species
There are 46 chromosomes in humans
Daughter cells must contain a full set of chromosomes
Before a cell divides the DNA of each chromosome must be replicated

4. Structure of a chromosomes
Chromatid
A replica strand of DNA
Each one will end up in a different daughter cell
Centromere
Holds the two copies together.
Chromatin is supercoiled to form visible chromosomes, this allows them to be moved around..

5. The Cell Cycle describes the events that take place as one parent cell divides to produce new daughter cells which then each grow to full size. M
Nuclear division (mitosis)
Cytokinesis (cleavage of cytoplasm)
Interphase G1
Biosynthesis – proteins are made and organelles replicate, S
Synthesis of new DNA
Replication of chromosomes
G2 - growth

6. The Cell Cycle (recap) The cell cycle has 3 main phases Interphase
cell grows to normal size
carries out normal biochemical functions
DNA replication takes place
Nuclear division
mitosis, this has 4 stages;
prophase, metaphase, anaphase and telophase
Cell division
cytoplasm divides by cytokinesis

7. The Cell Cycle

8. Learning Outcomes Recap
state that mitosis occupies only a small percentage of the cell cycle and that the remaining percentage includes the copying and checking of genetic information
explain the meaning of the term homologous pair of chromosomes;
describe, with the aid of diagrams and photographs, the main stages of mitosis (behaviour of the chromosomes, nuclear envelope, cell membrane and centrioles);

9. Nuclear Division
looking at the Karyotype of a human male, you can see:
Homologous pairs – each pair has distinctive banding when stained.
22 pairs of autosomes
1 pair of sex chromosomes (female XX; male XY)

10. Karyotype

11. Human body cells are diploid (2n), meaning that they have 2 sets of chromosomes. Human gametes are haploid (n), where n is the number of chromosomes in a single set

12. Learning Outcomes
describe, with the aid of diagrams and photographs, the main stages of mitosis (behaviour of the chromosomes, nuclear envelope, cell membrane and centrioles);

13. Mitosis
Nucleus of a cell divides resulting in two nuclei which are genetically identical to the parent nucleus.
4 stages
Prophase
Metaphase
Anaphase
Telophase

14. Prophase Chromosomes become visible and the nuclear envelope disappears

15. Metaphase Chromosomes arrange themselves at the centre (equator) of the cell.

16. Anaphase Chromatids migrate to opposite poles

17. Telophase The nuclear envelope reforms

18. Learning Outcomes
explain the significance of mitosis for growth, repair and asexual reproduction in plants and animals;
state that cells produced as a result of meiosis are not genetically identical (details of meiosis are not required);

19. Requirements of Nuclear Division
There are two requirements of nuclear division
Growth (Mitosis);
where a diploid zygote grows into a multi-cellular adult, all daughter cells have the same number of chromosomes as the parent cell.
sexual reproduction (Meiosis);
the number of chromosomes is halved so that gametes are haploid

20. Human Life Cycle Diploid Zygote 46 Haploid Sperm 23 Adult 46 Haploid
Egg 23
fertilisation

21. Meiosis
Chromosome number is halved so human gametes have 23 chromosomes
This reduction in chromosome number ensures that when gametes fuse to form a zygote (fertilisation) the diploid chromosome number is restored.

22. Meiosis

23. Learning Outcomes
outline, with the aid of diagrams and photographs, the process of cell division by budding in yeast;

24. Cell Division
In most cells, the nucleus divides first then the cytoplasm (cytokinesis).
This is mitosis and can be used for:
Growth and repair
Replacement of cells
Asexual reproduction
In bacteria, cell division takes place by binary fission
DNA replicates
Cell divides

25. Cell division in yeast Yeast is a single celled fungus
It reproduces asexually by budding
Cell produces a swelling (bud)
Nucleus divides into two – the bud gains a nucleus
The bud breaks off leaving a bud scar
Sometimes buds produce their own buds before separating.

26. Learning outcomes To define the term stem cell
Explain the meaning of the terms tissue, organ and organ system;
explain, with the aid of diagrams and photographs, how cells are organised into tissues, using as examples
squamous and ciliated epithelia,
xylem and phloem
discuss the importance of cooperation between cells, tissues, organs and organ systems

27. Stem Cell Stem cells are omnipotent or totipotent
The are cells which contain a full set of genetic information, and are capable of becoming any one of the different cell types found in a fully grown organism.

28. Stem Cells
There are a small number of stem cells found in adult mammals in the bone marrow, these are responsible for the formation of bone cells and blood cells.
Stem cells are currently being used in medical research.

29. Differentiation Unspecialised cells which show totipotency include
Stem cells in animals
Meristematic cells in plants
These cells divide and then specialise, this is differentiation.

30. Differentiation and organisation
There is a physical limit to the size a single cell can reach, therefore multicellular organisms need specialised cells.
These specialised cells are organised into tissues which carry out a specific function.
Tissues are organised into organs.

31. Differentiation of cells
Cells differentiate in a number of ways, by changing:
The number of a particular organelle
Muscle and liver cells contain many mitochondria
The shape of the cell
Red blood cells are a biconcave shape
Some of the cell contents
Red blood cells do not contain a nucleus
Differentiation means to specialise to carry out a particular role or function.

32. Examples of specialised cells
Erythrocytes
Neutrophils
Sperm
Root hair cells

33. Structure of specialised cells Try to write out the specific function of each specialisation
Lose their nucleus, mitochondria, Golgi apparatus and RER
Contain Haemoglobin
Erythrocytes
Granular cytoplasm due to large numbers of lysosomes
Neutrophils
Energy for movement of the undulipodium comes from the large number of mitochondria.
Head contains specialised lysosomes
Sperm
Hair-like extension, to increase the surface area for water absorption.
Root hair cells

34. Tissues, organs and systems
a group of similar specialised cells in a many celled organism, that carries out a specific function or several related functions
Organ
group of different tissues forming a distinct structure and functioning together
animal – lungs, heart, kidneys
plant – roots, stems, leaves
System
collection of organs with a particular function
cardiovascular and digestive systems

35. Tissues
A tissue is a group of similar, specialised cells which carry out a specific function, or several related functions.
Animal tissues
squamous and ciliated epithelium
Plant tissues
Xylem and phloem

36. Animal Tissues
Tissues that form sheets covering surfaces are called epithelial tissues, epithelial tissues are one cell thick and rest on a basement membrane (a network of collagen and glycoproteins), which holds the cells in position.
Two examples of animal tissues are squamous and ciliated epithelium.

37. Ciliated Epithelium
This tissue is found lining the ends of the bronchioles in the lungs.

38. Squamous Epithelium
This tissue covers many surfaces in the human body including the inner lining of cheeks and lining the walls of the alveoli in the lungs.
In the alveoli, the thinness of cells allows rapid diffusion of gases between alveoli and blood.

39. Squamous Epithelium

40. Plant Tissues
Examples of plant tissues include xylem and phloem, which are transport tissues in plants.
Xylem transports water and ions, phloem transports sugars and other compounds made by plants.
Tissues can be presented in plan diagrams, plan diagrams DO NOT show any individual cells.

41. Plan Diagrams – dicotyledonous leaf

42. Plan Diagrams - dicotyledonous leaf