1. (but not the exciting bits)
SEX
(but not the exciting bits)

2. Definition of sexual reproduction
A pattern of reproduction involving fusion of cells from two parents (fertilization).
Fusing two cells results in twice as many chromosomes per cell.
Therefore, sexual reproduction also includes a process to reduce chromosome number by half (meiosis).

3. Vocabulary
Gametes: specialized cells that unite in fertilization (e.g. sperm, eggs)
Zygote: the cell produced by fertilization
Haploid: the number of chromosomes in a gamete (symbolized n)
Diploid: the number of chromosomes in a zygote (symbolized 2n)

4. Species n 2n Mosquito 3 6 Rice plant 12 24 Alligator 16 32 Human 23 46
Every species has characteristic haploid and diploid chromosome numbers
Species n 2n
Mosquito 3 6
Rice plant 12 24
Alligator 16 32
Human 23 46
Potato 48
Dog 39 78
Carp 52
104

5. Diplontic life cycle Animals
The mature organism is diploid.
Mitosis allows these cells to divide so the organism can grow.
Meiosis produces gametes.
There is no mitosis in the haploid state.

6. Figure 9.12 Fertilization and Meiosis Alternate in Sexual Reproduction
Gametes
Male (n) Female (n)
HAPLOID (n)
Meiosis
Fertilization
DIPLOID (2n)
Zygote
Elephant (Loxodonta africana)
Adult
(2n)

7. Haplontic life cycle Fungi
The mature organism is all haploid.
Mitosis allows these haploid cells to divide so the organism can grow.
Gametes are produced by mitosis.
The zygote is the only diploid cell.
There is no mitosis in the diploid state; the first thing the zygote does is go through meiosis, back to the haploid condition.

8. Figure 9.12 Fertilization and Meiosis Alternate in Sexual Reproduction
Adult
(n)
Gametes
(n) (n)
Spore
(n)
HAPLOID (n)
Meiosis
Fertilization
DIPLOID (2n)
Fungus (Rhizopus oligosporus)
Zygote
(2n)

9. Alternation of Generations Plants
Mitosis occurs in both haploid and diploid states. There is a multicellular body in both states.
Sporophyte: a diploid body, developed by mitosis from a zygote, producing spores by meiosis.
Gametophyte: a haploid body producing gametes (by mitosis)

10. Figure 9.12 Fertilization and Meiosis Alternate in Sexual Reproduction
Gametophyte
(n)
Spore
(n)
Gametes
Male (n) Female (n)
HAPLOID (n)
Fertilization
Meiosis
DIPLOID (2n)
Sporangium
Zygote
Sporophyte
(2n)
Fern (Osmunda cinnamomcea)

11. Reading Assignment
Chapter 9: pp. 165 – 171
Especially study the diagrams of meiosis on pp and , which are not discussed in this PowerPoint presentation.