1. The life cycle of a multicellular organism includes
How to Make a Sea Star
The life cycle of a multicellular organism includes
development
reproduction
This sea star embryo (morula) shows one stage in the development of a fertilized egg (fusion of egg and sperm)
The cluster of cells will continue to divide as development proceeds by a series of cell division

2. Some organisms can also reproduce asexually
This sea star is regenerating a lost arm
Regeneration results from repeated cell divisions

3. CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION
Cell division is at the heart of the reproduction of cells and organisms
Organisms can reproduce sexually or asexually
Asexual reproduction- no variety
Sexula reproduction Variety

4. 8.1 Like begets like, more or less
Some organisms make exact or identical copies of themselves, asexual reproduction
Figure 8.1A

5. Other organisms make similar but not identical copies of themselves in a more complex process, sexual reproduction
Figure 8.1B

6. 8.2 Cells arise only from preexisting cells
All cells come from cells
Cellular reproduction is called cell division
Cell division allows an embryo to develop into an adult
It also ensures the continuity of life from one generation to the next

7. 8.3 Prokaryotes reproduce by binary fission
Prokaryotic cells divide asexually
These cells possess a single chromosome (packaged DNA during cell division) containing genes
The chromosome is replicated
The cell then divides into two cells, a process called binary fission
Prokaryotic chromosomes
Figure 8.3B

8. Binary fission of a prokaryotic cell
Plasma membrane
Prokaryotic chromosome
Cell wall
Duplication of chromosome and separation of copies
Continued growth of the cell and movement of copies
Division into two cells
Figure 8.3A

9. THE EUKARYOTIC CELL CYCLE AND MITOSIS
8.4 The large, complex chromosomes of eukaryotes duplicate with each cell division
A eukaryotic cell has many more genes than a prokaryotic cell
The genes are grouped into multiple chromosomes, found in the nucleus
The chromosomes of this plant cell are stained dark purple
Figure 8.4A

10. Chromosomes contain a very long DNA molecule with thousands of genes
Individual chromosomes are only visible during cell division

11. Before a cell starts dividing, the chromosomes are duplicated
Sister chromatids
This process produces sister chromatids
Centromere
Figure 8.4B

12. Chromosome distribution to daughter cells
When the cell divides, the sister chromatids separate
Chromosome duplication
Two daughter cells are produced
Each has a complete and identical set of chromosomes
Sister chromatids
Centromere
Chromosome distribution to daughter cells
Figure 8.4C

13. 8.5 The cell cycle multiplies cells
The cell cycle consists of two major phases:
Interphase, where chromosomes duplicate and cell parts are made
The mitotic phase, when cell division occurs
Figure 8.5

14. 8.6 Cell division is a continuum of dynamic changes
Eukaryotic cell division consists of two stages:
Mitosis
Cytokinesis

15. In mitosis, the duplicated chromosomes are distributed into two daughter nuclei
After the chromosomes coil up, a mitotic spindle (microtubules) moves them to the middle of the cell

16. Centrosomes (with centriole pairs) Early mitotic spindle Centrosome
INTERPHASE
PROPHASE
Centrosomes (with centriole pairs)
Early mitotic spindle
Centrosome
Fragments of nuclear envelope
Kinetochore
Chromatin
Centrosome
Spindle microtubules
Nucleolus
Nuclear envelope
Plasma membrane
Chromosome, consisting of two sister chromatids
Figure 8.6

17. The sister chromatids then separate and move to opposite poles of the cell
The process of cytokinesis divides the cell into two genetically identical cells

18. TELOPHASE AND CYTOKINESIS
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS
Cleavage furrow
Nucleolus forming
Metaphase plate
Nuclear envelope forming
Spindle
Daughter chromosomes
Figure 8.6 (continued)

19. 8.7 Cytokinesis differs for plant and animal cells
In animals, cytokinesis occurs by cleavage
This process pinches the cell apart
Cleavage furrow
Cleavage furrow
Contracting ring of microfilaments
Figure 8.7A
Daughter cells

20. In plants, a membranous cell plate splits the cell in two
Cell plate forming
Wall of parent cell
Daughter nucleus
In plants, a membranous cell plate splits the cell in two
Cell wall
New cell wall
Vesicles containing cell wall material
Cell plate
Daughter cells
Figure 8.7B

21. Most animal cells divide only when stimulated, and others not at all
8.8 Anchorage, cell density, and chemical growth factors affect cell division
Most animal cells divide only when stimulated, and others not at all
In laboratory cultures, most normal cells divide only when attached to a surface
They are anchorage dependent

22. Cells continue dividing until they touch one another
This is called density-dependent inhibition
Cells anchor to dish surface and divide.
When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).
If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition).
Figure 8.8A

23. Cell Cycle control
The cell cycle has critical checkpoint which determine whether the cycle will continue, pause or stop. Signals affecting critical checkpoints determine whether the cell will go through a complete cycle and divide
These checkpoints are controlled by specific proteins inside cells and growth factor signaling from outside the cell.
G1 checkpoint
Control system
M checkpoint
G2 checkpoint

24. Cell cycle control system
Growth factors are proteins secreted by cells that stimulate other cells to divide
They act by binding to the cell surface receptor and activate signalling mechanisms inside the cell to regulate proteins affecting the cell cycle control checkpoints
Growth factor
Plasma membrane
Relay proteins
Receptor
protein
G1 checkpoint
Signal transduction pathway
Cell cycle control system
Figure 8.8B
Figure 8.8B

25. Cancer cells have abnormal cell cycles
8.10 Connection: Growing out of control, cancer cells produce malignant tumors
Cancer cells have abnormal cell cycles
They divide excessively and can form abnormal masses called tumors
Radiation and chemotherapy are effective as cancer treatments because they interfere with cell division

26. 8.11 Review of the functions of mitosis: Growth, cell replacement, and asexual reproduction
When the cell cycle operates normally, mitotic cell division functions in:
Growth (seen here in an onion root)
Figure 8.11A

27. Cell replacement (seen here in skin)
Dead cells
Epidermis, the outer layer of the skin
Dividing cells
Dermis
Figure 8.11B

28. Asexual reproduction (seen here in a hydra)
Figure 8.11C