1. Cell Division

2. Cell Division
A process by which a cell, called the parent cell, divides into two or more cells, called daughter cells.

3. Why Do Cells Divide? For growth, repair, and reproduction

4. Genetic Material During Cell Division
DNA (deoxyribonucleic acid) – genetic material in cells contain info that determines traits that living things inherits found in nucleus of cell
DNA wraps around protein to form a complex material called chromatin before cell division DNA is duplicated

5. Genetic Material During Cell Division
Chromatin- organized into specific lengths called chromosomes
Chromosomes – threadlike structure that condense in early stages of cell division
a duplicated chromosome consists of 2 identical structure called chromatids held together by a centromere

6. Mitosis

7. Mitosis Part of cell cycle during which nucleus divides
In eukaryotic (nucleus and multicellular) cells undergo mitosis
Prokaryotes (no nucleus and unicellular) do not undergo mitosis

8. Mitosis Results in two nuclei identical to original nucleus
At end cell has 2 identical sets of chromosomes in two separate nuclei
Makes body cells

9. Meiosis

10. Difference in body and sex cells
A parent produces sex cells
have half of genetic information that body cells have when genetic info combines from two parents – offspring has full set of genetic info
(same # of chromosomes as parents)

11. Homologous chromosomes
each chromosome found in pairs are identical to the other in size and structure (carry genes for same trait)
only one pair differs - sex chromosomes X or Y

13. Terminology: Diploid vs. Haploid
Diploid - two sets of chromosomes (2n), in humans 23 pairs or 46 total
Haploid - one set of chromosomes (n) - gametes or sex cells, in humans 23 chromosomes

14. What is Meiosis?
A type of cell division that produces haploid sex cells
When an egg cell is fertilized by sperm cell a new diploid cell is formed which may develop into offspring

15. Mitosis vs. Meiosis

16. Mitosis
Meiosis
Meiosis

17. Based on the diagram,
The difference between mitosis and meiosis is that mitosis produces two identical daughter cells and meiosis produces four genetically different daughter cells

18. Mitosis Meiosis Parent cell Diploid (2n) Daughter cell Parent cell
1st division
2nd division
Daughter cell
Haploid (n)
Parent cell
Diploid (2n)
Daughter cell

19. The cells created from mitosis are diploid or 2n.
The numbers
The cells created from mitosis are diploid or 2n.
The cells created from meiosis are haploid or n.

20. One last thing… [the] where?
Mitosis occurs in normal body cells (i.e. skin cells), and meiosis occurs in sex cells (i.e. sperm and egg) only.

21. The reason why: mitosis
To replace other cells that have been damaged or worn out
To allow multicellular organisms to grow
For asexual reproduction
Because the cells get too big!

22. The reason why: meiosis
Meiosis results in four cells with half the number of chromosomes so that when the sex cells (sperm and egg) combine, the original or normal number of chromosomes will be restored.

23. Fill in the Venn diagram with your table mates.

24. Review Mitosis & Meiosis
Both are forms of nuclear division
Both involve replication
Both involve disappearance of the nucleus, and nucleolus, nuclear membrane

25. DIFFERENCES
Meiosis produces daughter cells that have 1/2 the number of chromosomes as the parent. Go from 2n to 1n.
Daughter cells produced by meiosis are not genetically identical to one another.
In meiosis cell division takes place twice but replication occurs only once.

26. Reproduction

27. A biological process by which new individual organisms are produced.
Reproduction
A biological process by which new individual organisms are produced.
Fundamental feature of all known life; each individual organism exists as the result of reproduction.

28. Asexual Reproduction
One organism produces one or more new organisms that are genetically identical to self.
The organism that produces the new organism are called a parent.
Each new organism is called an offspring
May differ if genetic mutation happens.

29. Types of Asexual Reproduction
Binary fission is the form of asexual reproduction in prokaryotes
Parent organism splits in two, producing 2 new cells (ex- bacteria)
Budding is when an organism develops tiny buds on its body
Grows until new organism formed
Result of mitosis (ex- single-celled yeasts and multicellular hydras)
Budding ex. hydra, parasites

30. Types of Asexual Reproduction
A spore is a specialized cell that can survive harsh conditions
Both prokaryotes and eukaryotes can form spores (ex- fungus)
New plants may grow from stems, roots, and leaves called vegetative reproduction
Runners- aboveground stems
Tubers- underground stems ex- potato
Plantlets- tiny plants that grow along plant's leaves

31. Sexual Reproduction
Sexual reproduction requires two parents that each combine a sex cell to produce a genetically unique organism.
Half the genes come from each parent
Offspring not identical to parent
Combination of traits from each parent

32. Fertilization Need one parent to be female (x)
Need one parent to be male (y)
sex cell – sperm cells
Need one parent to be female (x)
sex cell – egg cells
Sex cells have only half of genetic material found in body cells
Sperm and egg join together in process called fertilization to form a zygote
Cell has full set of genetic material and new organism develops
Zygote divides by mitosis to form all of the offspring’s cells

33. Advantages of Asexual Reproduction
Can replicate quickly
Identical to parent – favorable traits are passed on
Don’t need partner to reproduce
All offspring are able to produce offspring

34. Disadvantages of Asexual Reproduction
Offspring are genetic clones. Very little genetic variation may cause extinction to occur.
A negative mutation can make organisms susceptible to disease.
Unfavorable conditions, such as extreme temperatures can wipe out entire colonies.
Some methods of asexual reproduction produce offspring that are close together and compete for food and space.

35. Advantages of Sexual Reproduction
Increases genetic variation
Offspring have different traits
improves chances that at least some offspring will survive
true if environment changes
Not identical to parents
may produce new trait to survive better

36. Disadvantages of Sexual Reproduction
Finding a reproductive partner and producing gametes demands a lot of time and energy
Slower reproduction rate
many organisms never become parents
Genetic results are unpredictable
genetic “errors” happen more frequently because meiosis is complex
diploid organisms have more chromosomes to double

37. Advantages of Both Some organisms use both
For ex- In favorable conditions- plants and fungi reproduce asexually
If environment changes- switch to sexual reproduction to increase survival
Asexual & sexual reproduction