1. Sexual and asexual reproduction

2. Among living organisms, there are two types of reproduction-asexual and sexual.
Each type of reproduction has advantages and disadvantages.

3. Sexual Reproduction
Two parent cells join together to form offspring that are different from the parents.
These parent cells are called sex cells and are different from ordinary body cells.
Human body cells have 46 (or 23 pairs of) chromosomes.
Sex cells have only 23 chromosomes, half of the usual number.

4. Sexual Reproduction
Information contained on chromosomes determines many of our traits.
Eye color
Hair color
Blood type
Sex chromosomes determine gender.
In humans, females carry two X chromosomes.
Males have one X chromosome and one Y chromosome.

5. Sexual Reproduction
Sex cells in females are called eggs and carry an X chromosome.
Sex cells in males are called sperm and carry either an X or a Y chromosome.
Egg and sperm combine to form either XX (female) or XY (male).

7. Sexual Reproduction
The result: the offspring will carry half of each parent’s traits. Each time offspring are formed, a new combination of traits is passed.
So, sexual reproduction produces offspring that have a different combination of traits than their parents and their siblings.

9. Sexual Reproduction
Advantage- variation among offspring allows for adaptations and natural selection to occur.
Disadvantage- organisms must find a mate in order to reproduce.

10. sexual reproduction in plants

11. Asexual Reproduction
In asexual reproduction, a new organism (sometimes more than 1) is produced from only one organism.
New organisms have the exact same DNA as the parent.
This is known as Mitosis

12. Mitosis:
Happens in all cells
Cell division process
5 major stages

13. Prophase: Nuclear envelope disappears
Chromosomes condense – can see sister chromatids
and centromere
Spindle forms

14. Prophase:

15. Metaphase: Chromosomes move to the equator of spindle
Each chromatid is attached to spindle with centromere

16. Metaphase:

17. Anaphase: Centromeres split
Sister chromatids are pulled apart to opposite poles of the cell
Each chromatid is now a separate chromosome

18. Anaphase:

19. Telophase:
Nuclear envelopes (2) reform
Chromosomes begin to uncoil

20. Telophase:

21. Cytokinesis:
Cytoplasm divides
Two new daughter cells are now separate

22. Cytokinesis:

23. Organisms can asexually reproduce by:
Budding- new organism grows from the parent.
Examples- prickly pear cactus and potatoes.

24. Organisms can asexually reproduce by:
Fission- single celled bacteria without a nucleus copies its genetic material and divides to form an exact copy of itself.

25. fission in bacteria

26. Organisms can asexually reproduce by:
Regeneration- some organisms can grow an entirely new organism from a broken piece (sea stars for example).

27. Asexual Reproduction
regeneration

28. Asexual Reproduction Advantage- no need to find a mate!
Disadvantage- offspring are exact copies of their parents, so organisms don’t change much over generations. Doesn’t allow for adaptations and natural selection.

29. Meiosis:Terms you need to know 
Zygote: The fusion of sperm and egg.
Gamete: A mature male (sperm) or female (egg) germ cell that is able to unite with another of the opposite sex to form a zygote.
Homologous Chromosomes: are chromosome pairs, one from each parent, that are similar in length, gene position and centromere location.

30. Meiosis
Meiosis is a special type of cell division that produces gametes with half as many chromosomes.
In sexual reproduction, two parents provide an offspring with an unique gene combination. Each parent gives 1/2 of his/her genes (Chromosomes) to the offspring.

31. Video Clip

32. Prophase 1
Homologous chromosomes pair up and form tetrad

33. Metaphase 1
tetrads of homologous chromosomes become attached to the spindle fibers and move to equator

34. Anaphase 1
Microtubules of the spindle fiber shorten and pull the chromosomes toward the poles, taking both sister chromatids with them.

35. Telophase 1
The nuclear membrane reforms around the daughter nuclei. Each daughter nucleus contains two sister chromatids for each chromosome, attached to a common centromere.

36. Prophase 2
Nuclear envelope breaks down and a new spindle forms.

37. Metaphase 2
Spindle fibers bind to both sides of the centromere.

38. Anaphase 2
Spindle fibers contract and the sister chromatids move toward the opposite side.

39. Telophase 2
Nuclear envelope reforms around the set of daughter chromosomes.

40. Four daughter cells are created with the perfect amount of DNA.

41. Video Clip