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Chapter 7

Page history last edited by Shelly Turner 7 years, 11 months ago

Chapter 7:  Meiosis and Sexual Reproduction




 Click here for Flashcards for this chapter


Section 1 - Meiosis

I.     Meiosis (forms 4 haploid cells - pgs 142-3)

A.   Prophase I

1.    chromosomes become visible

2.    nuclear envelope dissolves

3.    spindle forms (the spindle is made of the centrioles and microfibers that move the chromosomes during mitosis)

B.  Metaphase I

1.    chromosomes line up along the equator

C.  Anaphase I

1.    centromeres divide (duplicate copies of chromosomes are separated)

2.    chromatids (now called chromosomes) move toward opposite sides of the cell

D.  Telophase I & Cytokinesis

1.    nuclear envelope forms around each set of chromosomes

2.    chromosomes uncoil

3.    spindle dissolves

4.    cytokinesis begins, two identical diploid cells form

E.  Prophase II

1.    new spindle forms in both cells

F.   Metaphase II

1.    chromosomes line up at the equator of both cells

G.  Anaphase II

1.    centromeres divide

2.    chromosomes are pulled apart into individual homologues

H.  Telophase II & Cytokenesis

1.    nuclear envelopes develop in all four cells

2.    cytoplasm divides, resulting in four haploid cells




II.     Meiosis in male vs. female animals (pg 146)

A.  Male meiosis (spermatogenesis) produces 4 functional haploid sperm

B.  Female meiosis (oogenesis) produces 1 viable egg and 3 non-functional polar bodies






Section 2 – Sexual Reproduction

I.     Asexual Reproduction

A.  A single parent passes all of its genes to the offspring, creating an identical copy; it is a simple method of reproduction that can produce many offspring quickly; however the lack of variety in the DNA of the species can limit the potential for adaptation

B.  Examples: cloning, budding (growth of a new individual on the body of the parent), binary fission (splitting of a single celled organism into two) 

II.   Sexual Reproduction (3 different cycles exist)

A.  Haploid Life Cycle

1.    Individual spends most of its life as haploid cells with only the zygote existing as a diploid cell

2.    Example: Unicellular fungi and algae



B.  Diploid Life Cycle

1.    The cells Individual are primarily diploid, only the sex cells (aka germ cells) are haploid

2.    Example: All animals including humans



C.  Alternation of Generations (pgs 152 & 524)

1.    Plants reproduce in two phases that alternate

a)    Sporophyte - diploid individual (formed from zygote after fertilization) that produces spores by meiosis

b)    Gametophyte - haploid individual (formed from spores) that produces gametes by mitosis









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