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Chapter 7

Chapter 7. Sexual Reproduction and the Diversity of Life. Ways of Reproduction. The Difference Between Asexual and Sexual. Asexual Reproduction – a single cell ( the mother cell) duplicates the same genetic information and becomes two daughter cells.

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Chapter 7

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  1. Chapter 7 Sexual Reproduction and the Diversity of Life

  2. Ways of Reproduction

  3. The Difference Between Asexual and Sexual • Asexual Reproduction – a single cell ( the mother cell) duplicates the same genetic information and becomes two daughter cells. • Sexual Reproduction – genetic information from two cells is combined to form the new genetic code for a new organism.

  4. Sexual Reproduction Types: Conjugation, Hermaphrodites, Separate Sexes • Conjugation – two cells come together and exchange small pieces of their genetic information (bacteria) • Hermaphrodites – organisms that create both male and female sex cells. Occurs in organisms that have restricted movement (sponges)

  5. Sexual Reproductions continued • Separate Sexes – In complex organisms specialized sex cells (sperm and egg) combine to form a zygote. Offspring are not identical to either the parent or further offspring (humans and some plants)

  6. Fertilization

  7. Homework • Read Section 7.1, pages202-205 • Do questions 1-6 on page 205

  8. Answers to 7.1 • 1. A zygote is a fertilized egg. • 2. Conjugation is a genetic recombination mechanism. • 3. Animals that contain both male and female sex cells are referred to a hermaphroditc. Sponges, tapeworms, earthworms, and barnacles are both male and female. • 4. a) internal fertilization: mammals, birds, earthworm • B) external fertilization: fish, amphibians, invertebrates • 5. Females contain two X chromosomes, while males contain a single X and a Y. • 6. a) 11 b) 22 c) 22 d) 11

  9. Meiosis • The process of forming sex cells, A human body cell contains 23 pairs of chromosomes. The gametes - sperm or eggs - contain half this number of chromosomes, which is why meiosis is sometimes called 'reduction division'.

  10. Meiosis continued • Organisms that reproduce sexually contain 2 types of cells. • 1) Somatic- cells that reproduce by mitosis, when cells divide each daughter cell is identical as the mother cell (skin and muscle cells • 2) Reproductive- produce sex cells which only have half the number of chromosomes (haploid cell)

  11. Meiosis • View video link http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio19.swf::Stages%20of%20Meiosis • Draw stages of meiosis into your notebooks (page 206/7 from textbook)

  12. Homework • Read section 7.2, pages 206-207 • Do questions 1-8 on page 207

  13. Answers to 7.2 Questions • 1. Somatic have a full compliment of chromosomes (diploid). Reproductive cells have one of the pairs of homologous chromosomes (haploid cells). • 2. Chromosomes that are simiar in size, shape, and gene arrangement are homologous. • 3. Meiosis 1 is the reduction division phase and Meiosis 2 is the division of the double stranded chromosomes.

  14. Answers continued • 4. Comparison of Mitosis and Meiosis 5. Meiosis reduces the chromosome number in sex cells from diploid to haploid. 6. 39 chromosomes • Yes they have the same number. • Genes code for the same characteristic but they may not be identical.

  15. Parts of the Flower Use diagram as reference to part descriptions on next slide

  16. The Male Parts Pollen – the male sex cells of the flower Filament - This is the stalk of the Anther. Anther - The Anthers contain pollen sacs. The sacs release pollen on to the outside of the anthers that brush against insects on entering the flowers. * The filament and the anthers are collectively known as the Stamen

  17. The Female Parts of the Flower • Egg the female sex cells of the flower • Stigma Is covered in a sticky substance that the pollen grains will adhere to. • Style The style raises the stigma away from the Ovary to decrease the likelihood of pollen contamination. • Ovary This protects the egg and once fertilization has taken place it will become the fruit.

  18. Homework • Read section 7.3, pages208-209 • Be prepared to label the parts of the cell as seen on page 210 in the textbook • Do questions 1-6 on page 209

  19. Answers to page 209 • 1. Flowering plants contain both male and female sex cells. • 2. Male sex cell (pollen) and female sex cell (eggs). • 3. During reproduction, the pollen sends a sperm down through the pistil with the male gamete in it. The sperm makes its way to the female sex cells in a process called fertilization.

  20. Answers Continued • 4. Once fertilized, the female sex cells of the flower become seeds. The petals of the flower slowly shrivel and disappear. The surrounding ovary becomes larger and develops into the fruit. • 5. Seeds (b,c) have spikes that get entangled in animal’s fur. Maple and poppyseed have large flat structures that catch the wind. Dandelions act as parachutes that get carried by the wind. • 6. Since the fruit is generally appetizing, animals eat fruits and scatter the seeds via the hind end.

  21. Strategies for Increasing Food Production

  22. Homework • Read section 7.5, pages212-213 • Do questions 1-3 on page 213

  23. Answers • 1. As the world population increases, food production must increase or people will starve. • 2. Grafting allows a tree to produce a different type of fruit quickly. Selective breeding identifies plants with the most desirable traits. • 3.In both cloning and grafting no sexual reproduction takes place so no new combination of genes will take place; therefore no diversity

  24. Atypical Meiosis • Atypical meiosis is the term given when meiosis does not separate the chromosomes correctly. • Nondisjunction is the failure to separate two homologous chromosomes * Understand Figure 1 on page 222

  25. Nondisjuction Video

  26. Nondisjunction Orders • Down Syndrome: too many chromosomes, mental disabilities (47) • Turner Syndrome: too few chromosomes, females don’t mature sexually/shorter (45) • Klinefelter Syndrome: too many chromosomes, males cannot reproduce (47)

  27. Homework • Read section 7.9, pages 222-223 • Do questions 1-5 on page 223

  28. Chapter 7 Review • Do questions 3-13 on pages 228-229

  29. Answers to Chpt. Review Questions • 3. Sexual reproduction causes the recombination of genetic info from different organisms. The new combination of genes can produce new traits. • 4. a) asexual b) sexual c) sexual d) asexual • 5. Because only one chromosome pair from each parent combines is a fertilized egg, different children, formed by different sperm and egg cells, will have new gene combinations.

  30. 6. • 7. The sperm cells unite with the female sex cells in a process called fertilization. The fertilized cells become seeds which in turn grow new plants. • 8. Male- pollen, anther and filament Female- stigma, style, ovary

  31. 9. • 10. a) female A b) 9,8,7 respectfully c) fertilization d) zygote

  32. 11. a) 23 b) Meiosis occurred c) 46 • 12. a) stage 2 b) fertilization c) mitosis d) 23 pairs • 13 Genetic information from two different individuals is combined. This creates genetic diversity.

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