1. MEIOSIS AND SEXUAL LIFE CYCLES CHAPTER 13

2. REPRODUCTION Asexual reproduction – single parent passes on all of its genes to its offspring Sexual reproduction – two parents give rise to offspring that have a combination of genes inherited from two parents

3. Figure 13.1 The asexual reproduction of a hydra

4. VOCABULARY Karyotype – picture of an organisms chromosomes Homologous chromosomes – pair of similar chromosomes Haploid – single chromosome set (n=23 for humans) Diploid – two sets of chromosomes (2n=46 for humans)

5. HUMAN FEMALE

6. HUMAN MALE

7. Zygote – fertilized egg Fertilization or syngamy – fusion of sperm and egg Somatic cell – body cells Gametes – sex cells Sex chromosomes – determine gender Autosomes – all other chromosomes Sister chromatids – copies of same chromosome

8. Figure 13.x1 SEM of sea urchin sperm fertilizing egg

9. LIFE CYCLE Sequence of stages in the reproductive history of an organism Alternation of generations – includes both diploid and haploid multicellular stages Sporophyte – multicellular diploid stage that makes haploid cells called spores

10. Gametophyte – a multicellular haploid stage made by spores that divide mitotically

11. Figure 13.4 The human life cycle

12. Figure 13.5 Three sexual life cycles differing in the timing of meiosis and fertilization

13. MEIOSIS A process that halves the chromosome number Mitosis vs. Meiosis Genetic recombination

14. Figure 13.6 Overview of meiosis

15. Figure 13.7 Meiosis I

16. Figure 13.7 Meiosis II

17. Figure 13.8 Mitosis vs. Meiosis

19. Figure 13.9 Different possible sex cells

20. MORE GENETIC POSSIBILITIES Synapsis – pairing of homologous chromosomes in prophase I Chiasmata or crossing over – when homologous portions of two nonsister chromatids trade place

21. Figure 13.10 Crossing over during meiosis