Reproduction

1. Reproduction

2. Invertabrates – How do they “Do It” • Hydra – Budding - asexual • Earthworm – hemaphroditic and exchange sperm with each other – the fertilized egg capsule gets dropped off in the soil • Grasshopper – separate sexes -Female grasshoppers deposit fertilized eggs in batches in the ground, the female uses four horn-like appendages at the tip of the abdomen, and twists her body and forces her ovipositor into the ground - metamorphosis

3. Vocab • Regeneration – lobster claw or sea star arm grows back • Parthenogenesis – egg cells can become an organism without sperm – ie bees • Haploid – n – one set of chromosomes (unfertelized egg) • Diploid – 2n - two sets of chromosomes

4. Males

5. Side View

6. Male Reproductive system • Major functions • Produces sperm • Produces semen – the fluid vehicle that acts as nourishment for sperm as they make their way through the female reproductive system • Produces Testosterone – male hormone for secondary sex characteristics and tells the body to make testosterone

7. Feedback Mechanism

8. Female Reproductive system

9. Side view

10. Meiosis • How we get SEX CELLS • Gametogenesis • Two division stages – Meiosis I and Meiosis II • Meiosis I is the reduction phase – Meiosis II is the division stage (similar to mitosis)

11. Gametogenesis

12. Meiosis I • Interphase I – DNA replicates, sister chromatids are joined by a centromere • Prophase I – Chromosomes line up in homologous pairs in a process called synapsis forming a tetrad – crossing over occurs during this stage.

13. Metaphase I – Tetrads move to the “equator” or metaphase plate – attach to spindle fibers • Anaphase I – homologous chromosomes separate (keeping chromotids intact) • Telophase I – events occur in the reverse order from the events in prophase I…spindle broken down two new cells are formed, chromosome number reduced in half

14. Non disjunction • During Meiosis I – an abnormality that can happen is that one pair of tetrads doesn’t separate so both chromosomes go to one side while the other side doesn’t get a copy of that chromosome at all – this is the cause of down’s syndrome. • non disjunction animation

15. Meiosis II • Meiosis II can occur immediately (in males) can be put on hold (in females) • Names are the same – prophase II, metaphase II, anaphase II, telophase II • Similar to mitosis the chromosomes line up in the middle (NOT tetrads) – chromotids separate to opposite poles – (only DNA doesn’t get replicated BEFORE this stage!)

16. Vocab • Meiosis – making sex cells • Gametogenesis – making sex cells • Gamete = sex cell • Spermatogenesis – making sperm • Sperm = male sex cell • Oogenesis – making egg • Ova = female sex cell

17. The menstrual cycle • The functioning of the reproductive system is dependent on the cyclical fluctuation of hormone levels that repeat regularly every 28 days.

19. Feedback Mechanism

20. If an egg is fertilized • Must be fertilized in the oviduct • 24 – 48 hours after ovulation • Pregnancy occurs • Fertilized egg travels down oviduct and implants into uterus • Most development occurs within the first trimester (month 1 – 3) • The last trimester is mainly for growth

21. Genetic Variation • If a plant has seven pairs of chromosomes – and there are two different ways it can line up at the equator…how many sperm are possible? • 2n = 27 = 128 combinations of sperm – also then 128 combinations of egg how many possible zygote • 128 x 128 = 16,384 possible outcome

22. Human variation • We have 23 chromosome – 2n = 223 = over 8 million combinations • 223 x 223 = 70 trillion different zygotes are possible.

23. In the Beginning • Gastrulation • More human Development