“ Meiosis and Sexual Reproduction” Chapter 7 Notes
I. MEIOSIS
A. Formation of Haploid Cells <ul><li>1.  Meiosis  reduces the number of chromosomes by  half  to form  gametes . </li></u...
MEIOSIS
<ul><li>Picture of a sperm cell fertilizing an egg cell  </li></ul>
B. Meiosis and Genetic Variation <ul><li>1. Genetic variation is necessary for  evolution  to occur. </li></ul><ul><li>2. ...
a.  independent assortment
b.  crossing-over
c.  random fertilization
SEGREGATION & CROSSING OVER together make even more combinations See ananimation
http://www.tokyo-med.ac.jp/genet/anm/mimov.gi
C. Meiosis and Gamete Formation <ul><li>1.  Spermatogenesis  – process by which  sperm  are produced in males.  </li></ul>...
C. Meiosis and Gamete Formation <ul><li>2.  Oogenesis  – process by which an  ovum  (egg cell) is produced in females. </l...
 
II. SEXUAL REPRODUCTION
A. Sexual and Asexual Reproduction <ul><li>1 .  Asexual  – formation of offspring from  1  parent. Produces  clones  that ...
A. Sexual and Asexual Reproduction <ul><li>2.  Sexual  – formation of offspring through union of  gametes  from  2  parent...
B. Sexual Life Cycles in Eukaryotes <ul><li>1.  Haploid life cycle  – simplest of all life cycles. Haploid cell major port...
 
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Chapter 7 notes

  1. 1. “ Meiosis and Sexual Reproduction” Chapter 7 Notes
  2. 2. I. MEIOSIS
  3. 3. A. Formation of Haploid Cells <ul><li>1. Meiosis reduces the number of chromosomes by half to form gametes . </li></ul><ul><li>2. During fertilization the gametes unite to form a zygote and restore the original diploid number. </li></ul><ul><li>3. Result of meiosis is 4 haploid gametes from 1 diploid cell. </li></ul>
  4. 4. MEIOSIS
  5. 5. <ul><li>Picture of a sperm cell fertilizing an egg cell </li></ul>
  6. 6. B. Meiosis and Genetic Variation <ul><li>1. Genetic variation is necessary for evolution to occur. </li></ul><ul><li>2. Three events during meiosis contribute to genetic variation: </li></ul><ul><ul><li>a. independent assortment – random distribution of homologous chromosomes during meiosis. </li></ul></ul><ul><ul><li>b. crossing-over – exchange of genetic material between homologous chromosomes during meiosis </li></ul></ul><ul><ul><li>c. random fertilization – random fertilization of an egg by a sperm </li></ul></ul>
  7. 7. a. independent assortment
  8. 8. b. crossing-over
  9. 9. c. random fertilization
  10. 10. SEGREGATION & CROSSING OVER together make even more combinations See ananimation
  11. 11. http://www.tokyo-med.ac.jp/genet/anm/mimov.gi
  12. 12. C. Meiosis and Gamete Formation <ul><li>1. Spermatogenesis – process by which sperm are produced in males. </li></ul><ul><li>A diploid cell increases in size to become a germ cell , goes through meiosis , forms 4 haploid sperm cells. </li></ul>
  13. 13. C. Meiosis and Gamete Formation <ul><li>2. Oogenesis – process by which an ovum (egg cell) is produced in females. </li></ul><ul><li>A diploid cell increases in size to become a germ cell . Unequal division of the cytoplasm during meiosis results in a larger cell that becomes the egg and 3 smaller cells that become polar bodies and die. </li></ul>
  14. 15. II. SEXUAL REPRODUCTION
  15. 16. A. Sexual and Asexual Reproduction <ul><li>1 . Asexual – formation of offspring from 1 parent. Produces clones that are genetically identical to parents. </li></ul><ul><ul><li>a. fission </li></ul></ul><ul><ul><li>b. fragmentation </li></ul></ul><ul><ul><li>c. budding </li></ul></ul><ul><ul><li>Disadvantage of asexual reproduction is lack of genetic variation . (always produces a clone) </li></ul></ul>
  16. 17. A. Sexual and Asexual Reproduction <ul><li>2. Sexual – formation of offspring through union of gametes from 2 parents. </li></ul><ul><li>Offspring are genetically different than the parents. </li></ul>23 chromosomes 23 chromosomes 46 chromosomes
  17. 18. B. Sexual Life Cycles in Eukaryotes <ul><li>1. Haploid life cycle – simplest of all life cycles. Haploid cell major portion of life cycle. Ex: algae and fungi </li></ul><ul><li>2. Diploid life cycle – adults are diploid and are major portion of life cycle. Only haploid cells are gametes . Ex: animals including humans </li></ul><ul><li>3. Alternation of Generations – some organisms such as plants have a life cycle that alternates between haploid and diploid phases . </li></ul>

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