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CHAPTER 22: THE REPRODUCTIVE SYSTEMS

I.INTRODUCTION

All living organisms must reproduce in order to continue their species.  Humans reproduce by sexual reproduction with internal fertilization, where a flagellated sperm (from the male father) fertilizes an ovum (from the female mother) producing a zygote.  In sexual reproduction, the genetic information is contributed by both parents, and therefore a unique combination of genetic information results in each zygote.

II.THE FUNCTIONS OF THE REPRODUCTIVE SYSTEMS

The various reproductive organs work together to:

A.produce gametes;

B.transport gametes;

C.maintain gametes;

D.maintain developing zygote/fetus(female);

E.produce sex hormones:

1.male = testosterone;

2.female = estrogen and progesterone.

III.MEIOSIS

A.The genetic information of living organisms is DNA (deoxyribonucleic acid) that is carried on the genes of chromosomes.  

B.In humans, each somatic (body) cell is diploid, which means the cell contains 46 chromosomes or 23 pairs.

C.Human sex cells or gametes, however, are haploid, which means the cell contains only 23 chromosomes.

D.Meiosis is the type of cell division that results in gametes that possess half the chromosome number of the parent cell (i.e. meiosis reduces the chromosome number by one-half).

1.Male sperm (haploid)=23 chromosomes (1 set)

2.Female egg (haploid)=23 chromosomes (1 set)

__________________________________________________________

3.Fertilization

(zygote; diploid)=46 chromosome (2 sets).

*What happens to this diploid zygote now?

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