1. Reproduction How Life has continuation (or babies)

2. Section 10.2 Summary – pages 263-273
Asexual Reproduction
When cells divide by mitosis, the new cells have exactly the same number and kind of chromosomes as the original cells.
This is one form of asexual (or without sex) reproduction that occurs in mostly single celled organisms.
(Take notes on underlined words)
Section 10.2 Summary – pages

3. Sexual Reproduction
Sex requires a mixing of DNA between two similar organisms.
Every offspring will have some DNA from both parents.
In higher organisms, DNA will be present in homologous chromosomes, one from mom and one from dad.

4. Section 10.2 Summary – pages 263-273
Homologous chromosomes have the same type of
genes but one copy is from each parent.
Homologous Chromosome 4
On homologous chromosomes, the genes are arranged in the same order, but because there are different possible alleles for the same gene, the two chromosomes in a homologous pair are not always identical to each other. a A
Terminal
Axial
Inflated D d
Constricted T t
Short
Tall
Section 10.2 Summary – pages

5. Section 10.2 Summary – pages 263-273
A cell with two of each kind of chromosome is called a diploid cell.
Why would it be called a diploid?
What would happen if a diploid cell from a male combined with a diploid cell from a female?
Section 10.2 Summary – pages

6. Mom 46 + Dad 46 = Baby 92 chromosomes
This is a problem!

7. Section 10.2 Summary – pages 263-273
If two diploid cells combined, then each generation would have a double number of chromosomes.
Each pea plant parent, which has chromosomes, would produce gametes that contained a complete set of 14 chromosomes.
The F1 pea plants would have cell nuclei with 28 chromosomes, and the F2 plants would have cell nuclei with 56 chromosomes.
How can it work?
Section 10.2 Summary – pages

8. Section 10.2 Summary – pages 263-273
Haploid cells
In the sex organs, organisms produce gametes that contain one of each kind of chromosome.
A gamete contains one of each kind of chromosome or half the number of chromosomes is called a haploid cell.
Now, what would happen if two haploid cells got together? 
Section 10.2 Summary – pages

9. Section 10.2 Summary – pages 263-273
Another type of cell division is needed for sexual reproduction that would produce gametes containing half the number of chromosomes as a parent’s body cell.
It is called meiosis.
Section 10.2 Summary – pages

10. Section 10.2 Summary – pages 263-273
Diploid and haploid cells
This fact supports Mendel’s conclusion that parent organisms give one allele for each trait to each of their offspring.
Chromosome Numbers of Common Organisms
Organism
Body Cell (2n)‏
Gamete (n)‏
Fruit fly 8 4
Garden pea 14 7
Corn 20 10
Tomato 24 12
Leopard Frog 26 13
Apple 34 17
Human 46 23
Chimpanzee 48 24
Dog 78 39
Adder’s tongue fern
1260
630
Section 10.2 Summary – pages

11. Section 10.2 Summary – pages 263-273
What is meiosis?
Meiosis consists of two separate divisions, known as meiosis I and meiosis II.
*Meiosis I begins with one diploid (2n) cell.
*By the end of meiosis II, there are four haploid (n) cells.
*Or from one cell, four gametes are made.
Section 10.2 Summary – pages

12. Section 10.2 Summary – pages 263-273
Why meiosis?
*These haploid cells are called sex cells— gametes.
*Male gametes are called sperm.
*Female gametes are called eggs.
*When the egg is fertilized, the resulting zygote once again has the diploid number of chromosomes.
Section 10.2 Summary – pages

13. Section 10.2 Summary – pages 263-273
Why meiosis?
This pattern of reproduction, involving the production and subsequent fusion of haploid sex cells, is called sexual reproduction.
Meiosis
Haploid gametes
(n=23)‏
Sperm Cell
Meiosis
Egg Cell
Fertilization
Diploid zygote
(2n=46)‏
Multicellular
diploid adults
(2n=46)‏
Mitosis and Development
Section 10.2 Summary – pages

14. Sect ion 10.2 Summary – pages 263-273
The Phases of Meiosis
Click image to view movie.
Sect ion 10.2 Summary – pages

15. When have I seen this before?

16. Section 10.2 Summary – pages 263-273
Interphase
*At the end of interphase, each chromosome replicates to form two identical sister chromatids, held together by a centromere.
Interphase
Section 10.2 Summary – pages

17. Section 10.2 Summary – pages 263-273
Prophase I
The chromosomes coil up and a spindle forms.
*As the chromosomes coil, homologous chromosomes line up with each other gene by gene along their length, to form a four part structure called a tetrad.
Prophase I
Section 10.2 Summary – pages

18. Section 10.2 Summary – pages 263-273
Prophase I
*Homologous chromosomes can break and exchange genetic material in a process known as crossing over
Crossing over can occur at any location on a chromosome, and it can occur at several locations at the same time.
Prophase I
Section 10.2 Summary – pages

19. Section 10.2 Summary – pages 263-273
Crossing Over
It is estimated that during prophase I of meiosis in humans, there is an average of two to three crossovers for each pair of homologous chromosomes.
Sister chromatids
Nonsister chromatids
Crossing over in tetrad
Tetrad
Homologous chromosomes
Why?
Gametes
Section 10.2 Summary – pages

20. Section 10.2 Summary – pages 263-273
Prophase I
*Crossing over results in new combinations of alleles on a chromosome for more genetic variety.
Sister chromatids
Nonsister chromatids
Crossing over in tetrad
Tetrad
Homologous chromosomes
Gametes
Section 10.2 Summary – pages

21. Section 10.2 Summary – pages 263-273
Metaphase I
*During metaphase I, the centromere of each chromosome becomes attached to a spindle fiber.
The spindle fibers pull the tetrads into the middle, or equator, of the spindle.
Metaphase I
*This is where independent assortment occurs as different chromosomes are pulled apart.
This and crossing over is why you look different from your siblings.
Section 10.2 Summary – pages

22. Section 10.2 Summary – pages 263-273
Anaphase I
*Anaphase I begins as homologous chromosomes, each with its two chromatids, separate and move to opposite ends of the cell.
This critical step ensures that each new cell will receive only one chromosome from each homologous pair.
Anaphase I
Section 10.2 Summary – pages

23. Section 10.2 Summary – pages 263-273
Telophase I
Events occur in the reverse order from the events of prophase I.
*In telophase, the spindle is broken down, the chromosomes uncoil, and the cytoplasm divides to yield two new cells.
Telophase I
Section 10.2 Summary – pages

24. Section 10.2 Summary – pages 263-273
Telophase I
Each cell has half the genetic information of the original cell because it has only one chromosome from each homologous pair.
Telophase I
Section 10.2 Summary – pages

25. Section 10.2 Summary – pages 263-273
The phases of meiosis II
* During prophase II, a spindle forms in each of the two new cells and the spindle fibers attach to the chromosomes.
Prophase II
Section 10.2 Summary – pages

26. Section 10.2 Summary – pages 263-273
The phases of meiosis II
* During metaphase II, the chromosomes, still made up of sister chromatids, are pulled to the center of the cell and line up randomly at the equator.
Metaphase II
Section 10.2 Summary – pages

27. Section 10.2 Summary – pages 263-273
The phases of meiosis II
*Anaphase II begins as the centromere of each chromosome splits, allowing the sister chromatids to separate and move to opposite poles.
Anaphase II
Section 10.2 Summary – pages

28. Section 10.2 Summary – pages 263-273
The phases of meiosis II
* In Telophase II, nuclei reform, the spindles break down, and the cytoplasm divides.
Telophase II
Section 10.2 Summary – pages

29. Meiosis Provides for Genetic Variation
Cells that are formed by mitosis are identical to each other and to the parent cell.
In meiosis, reassortment of chromosomes and the genetic information they carry, either by crossing over or by independent segregation of homologous chromosomes, is called genetic recombination.
Thus, variability is increased.

30. Meiosis video more life like
Flower reproduction roles

31. Section 24.1 Summary – pages 633-640
Asexual reproduction
Some plants can make new plants from cuttings or buds from the original plant
The new plants from asexual reproduction have the same genetic makeup as the original plant. (Clone)
Section 24.1 Summary – pages

32. Section 24.1 Summary – pages 633-640
Sex for plants (sounds familiar)
The female gamete is an egg and the male is a sperm.
When a sperm fertilizes an egg, a diploid zygote (later embryo) forms. This is sexual reproduction.
The embryo develops to maturity as a seed. Many seeds are surrounded by fruit (the ovary) to provided nourishment to develop the seed into a plant .
Section 24.1 Summary – pages

33. Section 24.2 Summary – pages 641-645
The structure of a flower is for plant sex
Petals are colorful structures at the top of a flower stem. Petals are to attract birds and insects that transfer pollen between plants.
The flower stem is called peduncle and supports the flower.
Sepals are usually leaf-like and encircle the peduncle below the petals. Sepals protect the flowers before blooming
Section 24.2 Summary – pages

34. Section 24.2 Summary – pages 641-645
The structure of a flower – male parts
Inside the petals are the stamens. A stamen is the male reproductive organ of a flower. It is made up of the filament that holds up the anther.
At the tip of the stamen is the anther. The anther produces pollen that contain sperm. A flower makes millions of pollen grains.
Section 24.2 Summary – pages

35. Section 24.2 Summary – pages 641-645
The structure of a flower
Stigma
Petals
Style
Pistil
Ovary
Anther
Stamen
Filament
Sepal
Peduncle
Section 24.2 Summary – pages

36. Section 24.2 Summary – pages 641-645
The structure of a flower
The pistil is the female organ of the flower. The pistil is made of the stigma which is sticky to catch the pollen and the style that hold up the stigma.
At the bottom portion of the style is the ovary, a structure with one or more ovules, each usually contains one egg.
A plant makes fewer eggs than sperm (‘cause most sperm get lost and never reach the eggs).
Section 24.2 Summary – pages

37. Section 24.3 Summary – pages 646-657
Development of the female ovules
In flowers, the female ovule forms within the ovary.
In the ovule, a cell undergoes meiosis and produces haploid cell (half the genetic info).
In most flowering plants, these haploid cells undergoes mitosis three times, producing eight haploid nuclei. Only three of the eggs cells will be fertilized.
Section 24.3 Summary – pages

38. Section 24.3 Summary – pages 646-657
Development of the male parts (pollen)
Haploid cells (sperm) are produced by meiosis within the pollen sac.
The nucleus of each haploid cell undergoes mitosis.
A thick, protective wall surrounds these cells. This structure is the immature male cells or pollen grain.
Section 24.3 Summary – pages

39. Section 24.3 Summary – pages 646-657
Pollination
In flowering plants, pollination (sex) is the transfer of the pollen grain from the anther (male part) to the stigma (top of female part).
Depending on the type of flower, the pollen can be carried to the stigma by wind, water, or animals (birds and bees) that are attracted by nectar (sugar water).
Section 24.3 Summary – pages

40. Two plants having artificial sex
This is what Mendel did to control the cross pollination of his plants.

41. Section 24.3 Summary – pages 646-657
Fertilization
Inside each pollen grain are two haploid nuclei, the tube nucleus (grows tube) and the generative nucleus (to fertilize egg). Sperm is delivered by the pollen tube to the ovules (female).
Pollen grain
Stigma
Two sperm nuclei
Style
Pollen tube
Tube nucleus
Ovary
Central cell
Ovule
Egg cell
Section 24.3 Summary – pages

42. Section 24.3 Summary – pages 646-657
Fertilization
Double Fertilization
One of the sperm unites with the egg forming a diploid zygote which begins the new baby plant as the beginning of a seed.
One sperm fertilizes the central cell (3n)
The wall of the ovule becomes the seed coat, which can aid in seed dispersal and help protect the embryo until it begins growing.
One sperm fertilizes the egg cell (2n)
Seeds are alive just dormant!
Section 24.3 Summary – pages

43. Section 24.3 Summary – pages 646-657
Seed formation
Click this to view movie.
Section 24.3 Summary – pages

44. Section 24.3 Summary – pages 646-657
As the seeds develop, the surrounding ovary enlarges and becomes the fruit.
Fruit
Ovary
Ovules
Sepals
Stamen
Fused petals
Seeds and Fruits
Section 24.3 Summary – pages

45. Section 24.3 Summary – pages 646-657
Fruit formation
Click this to view movie.
Section 24.3 Summary – pages

46. Section 24.3 Summary – pages 646-657
Germination – the dormant seed wakes up
Water is important because it activates the embryo’s metabolic system.
The first part of the plant embryo to appear is the embryonic root that will grow toward the pull of gravity.
A second shoot grows away from gravity to make leaves. It straightens, bringing with it the cotyledons and the plant’s first leaves.
Section 24.3 Summary – pages