1. The Building Blocks of Life: Cell Division and Reproduction
Cells
The Building Blocks of Life:
Cell Division and Reproduction

2. All living things are made of cells
Plant Cells
Animal Cells

4. Cell Theory The current cell theory states that:
All living things are made of cells.
Cells are the basic unit of structure and function in living things.
Living cells only come from other living cells.

5. What Are Cells Made Of?
Organelles, or “tiny organs”, are the structures that make up a cell.
Organelles were discovered by Robert Hooke in 1665 while looking at cork cells.
Nucleus, mitochondria, chloroplasts, cell wall, cell membrane, lysosomes, vacuoles, ribosomes, cytoplasm, etc.

6. How Do Organisms Grow? Organisms do not grow by increasing cell size.
Why Not?
Instead organisms grow by creating more cells.
This process is called cell division.

7. Cell Division Cell division occurs in a series of stages or phases.
The most important concept is that:
A parent cell divides into two daughter cells.

8. Two Types of Cell Division
Meiosis forms daughter cells with half the chromosomes of parent cell
Mitosis forms identical daughter cells

9. Cellular Reproduction

10. Why is Reproduction Needed?
Cell reproduction is necessary to:
keep the species going
replace the death of cells
increase the size of organisms (due to size limit of cells)
produce new individuals.

11. 2 Forms of Reproduction Asexual Reproduction Mitosis A single parent
No special sex cells
No special sex organs
Genetically identical to parents
Sexual Reproduction
Meiosis
2 parents
Special sex cells = gametes (sperm/egg)
Special sex organs = gonads (ovaries/testes)
Not genetically identical to parent (1/2 chromosomes from mom, ½ from dad)

12. Mitosis – Asexual Reproduction Result is two identical cells

13. Meiosis - Sexual Reproduction Result is daughter cells with half the chromosomes

14. Egg and Sperm Cells – Fertilization
Fertilization is the fusion of two cells, a sperm cell and an egg cell.
Each of these cells contains ½ of the chromosomes needed.

15. What are Chromosomes?
Chromosomes are found in the nucleus of the cell.
Chromosomes are made of DNA = genetic material that directs the cell’s activities.
DNA codes for traits and is passed on from parent to offspring (in both sexual and asexual reproduction)
All organisms have a characteristic number of chromosomes.
Humans have 46 chromosomes (2N)
Chromosomes are arranged in pairs: 23 pairs (N = ½ the number of chromosomes; 1 from each pair)

16. What are the Phases of Cell Division
Phase 1: Interphase
Phase 2: Prophase
Phase 3: Metaphase
Phase 4: Anaphase
Phase 5: Telophase
Phase 6: Cytokinesis

17. Cell Division – Interphase: Chromosomes are Copied
Chromosomes look threadlike – called chromatin.
Centrioles appear outside the nucleus.
Near the end of phase 1 cell division begins:
Chromosomes are copied

18. Interphase

19. Cell Division – Prophase: Mitosis Begins
Mitosis is the process of cell division where the nucleus divides into two nuclei and two identical daughter cells are formed.

20. Prophase

21. Cell Division – Metaphase: Chromosomes attach to spindle
In metaphase the chromosomes attach themselves to the spindle fibers.
The centromere is what attaches the chromosomes to the spindle fiber.

22. Metaphase

23. Cell Division – Anaphase: Chromosomes begin to separate
In anaphase the chromosomes begin to separate.
The centromere splits and each pair of chromatids begin to move toward the ends of the cell.

24. Anaphase

25. Cell Division – Telophase Two new nuclei form
In telophase two new nuclei form
Chromosomes uncoil and are surrounded by a nuclear membrane.
A nucleolus reappears.
Cell division is complete.

26. Animal and Plant Telophase

27. Cell Division – Cytokinesis Two daughter cells form
In Cytokinesis two new daughter cells form.
Cell membrane “pinches” cell in the middle forming two identical daughter cells.
In plant cells a cell wall forms around each daughter cell.
Process of cell division is now over.

28. Plant Cell Cytokinesis

29. Cell Reproduction: Key Terms
Cell = the basic building block of all living things
Organelles = tiny organs, structures, that make up a cell and are responsible for cell function.
Chromosomes = genetic material found in the nucleus that directs the cell’s activities, made of DNA.
Cell division = the process of cell reproduction where a parent cell creates new daughter cells.

30. Cell Reproduction: Key Terms
Mitosis = cell division that results in two daughter cells that are genetically identical to parent.
Meiosis = cell division that results in 4 daughter cells, each having ½ the chromosomes of the parent.
Asexual reproduction = process where a new individual organism is created from only one parent; offspring is genetically identical to parent.

31. Cell Reproduction: Key Terms
Sexual reproduction = process where a new individual organism is created from two parents; offspring is not genetically identical to parent.
Gametes = specialized sex cells involved in sexual reproduction (male = sperm, female = egg)
Gonads = specialized sex organs where gametes are created by meiosis (male = testes, female = ovaries)
Fertilization = the fusion of gametes that results in the formation of a new organism, or offspring.

32. Cell Reproduction: Key Terms
Internal fertilization = fertilization that takes place inside an organism.
External fertilization = fertilization that takes place outside an organism.

33. What Is Cell Specialization?
In multicellular organisms, cells not only complete their own life activities, but also perform a function that contributes to the life of the organism.
Within multicellular organisms there is division of labor or specialization.
The work of keeping the organism alive is divided up among different parts of the organism.

34. Levels of Specialization
Cells combine to form
Tissues combine to form
Organs combine to form
Organ systems combine to form
Organism

35. More Specialization Students combine to form Classes combine to form
Grades combine to form
Schools combine to form
District