1. Genetic Variation
LHS Biology B

2. Sexual and Asexual Reproduction
Organisms produce offspring in 2 different ways
Sexual reproduction requires 2 parents
Asexual reproduction only requires 1 parent
Most organisms use one or the other, but some can do both

3. Sexual Reproduction
2 parents’ genes combine to form a genetically unique offspring
Genetic variation comes from mutation, meiosis, and random fertilization
Usually takes more energy than asexual reproduction
Most organisms that you are most familiar with use sexual reproduction
Mammals, reptiles, birds, fish, amphibians, and many plants

5. Asexual Reproduction 1 parent produces a genetic copy of itself
Genetic Variation comes from mutation only
Usually takes less energy and time than sexual reproduction
Some organisms that can use asexual reproduction are: bacteria, some plants, sea stars, and hydra

7. Summary Disadvantages: Slower Takes more energy More complicated
Sexual Reproduction
Asexual Reproduction
Disadvantages:
Slower
Takes more energy
More complicated
Rare organisms
Major Advantage
Genetic Variation
Disadvantage:
Little genetic variation
Advantages:
Faster
Saves Energy
Less Complicated
Only 1 parent required

8. What type of reproduction?

9. Meiosis A type of cell division that produces reproductive cells
The cells produced are haploid, but come from a diploid parent cell
Diploid: A cell with 2 sets of chromosomes, one from each parent
Haploid: A cell with only one set of chromosomes

11. Meiosis

12. Results of Meiosis Produces 4 haploid cells called gametes
Reproductive cells, sperm, egg
2 gametes (1 sperm and 1 egg) come together at fertilization, resulting in a zygote
This keeps the chromosome number from changing each generation

13. Cell Division: Meiosis I
Diploid: 4 chromosomes
Cell Division: Meiosis I
Cell Division: Meiosis II
Haploid: 2 chromosomes

14. Meiosis is different from Mitosis
2 Divisions: Meiosis I and Meiosis II
Daughter cells are genetically unique
Different from each other and the original cell
Only occurs in certain organs of sexually reproducing organisms

15. Challenge Question #1 Is Meiosis happening in your body right now?
Is Mitosis happening in your body right now?
Explain :)

17. How to Keep them Straight
MiTOsis happens in TOES
Produces identical body cells
MeIosis is why I am unique, why I am ME
Produces unique gametes

19. Chromosomes Review

20. Meiosis I Pairs of chromosomes are divided
One chromosome from each pair goes to each daughter cell
Produces cells with the haploid number of chromosomes
Each daughter cell gets one chromosome from each pair
The pairs split up randomly

21. Meiosis I Diploid: 4 chromosomes Diploid: 4 chromosomes
Haploid: 2 chromosomes
Haploid: 2 chromosomes

22. Meiosis II Results in 4 haploid daughter cells Basically like mitosis
Chromotids seperate at the centromere like mitosis
Results in 4 haploid daughter cells
4 functional sperm
1 functional egg and 3 nonfunctional haploid cells (called polar bodies)

23. Challenge Question #2
Explain the purpose of Meiosis in just a few sentences.

24. Meiosis II Diploid: 4 chromosomes Diploid: 4 chromosomes
Haploid: 2 chromosomes
Meiosis II
Haploid: 2 chromosomes

25. Fertilization Random Fertilization
Joining of egg and sperm to produce a zygote
Zygote is a diploid cell
Random Fertilization
Any sperm is equally likely to fertilize any egg
Another source of genetic variation

26. Challenge Question #3
Draw and label a picture that models the process of meiosis.

27. Discovery of DNA DNA is the genetic material that makes up chromosomes
When it is not condensed it is called chromatin
It wasn’t that long ago that we didn’t know about DNA
See timeline on page 292
World War II lasted from 1939 to 1949 for reference

28. Image Credits
Bruce the shark: ucetheshark.jpg
Sven the Reindeer: ages/8/83/SVEN2.png
Aphie and the Queen: mages/e/eb/Queenbugslife.png
Bacteria:
Strawberry plant:
Hydra: Simmons/pages/hydra2.htm
Sea Star: armed-sea-critter.html

29. Image Credits Continued
Meiosis Diagram 1:
Mitosis & Meiosis side by side: cellcycle-mitosis-meiosis
Chromosomes: htm
Meiosis I: /bio%20101%20lectures/meiosis/meiosis.htm
Meiosis II: czi5F0idF74/UFySnBEmB5I/AAAAAAAAAXM/MjWg4VsX34I/s640/Meio sis+II.jpg
Telophase II/Cytokinesis: k4/4webimages/figure photo.jpg
Anaphase II: k4/4webimages/figure photo.jpg
Fertilization: