Download Sexual Reproduction

Section 6.1
Sexual Reproduction
Text Pages 170 - 179
Key Terms
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Sexual Reproduction
Gamete
Fertilization
Zygote
Embryo
Diploid
Haploid
Meiosis
Homologous Chromosomes
Interkinesis
Section 6.1 Learning Objectives
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Define sexual reproduction
Define gamete, fertilization, zygote, and embryo
Define diploid and haploid
Describe the role of meiosis in sexual reproduction
State and briefly describe the eight phases of meiosis
Sexual Reproduction: Genetic variety
• Sexual Reproduction: reproduction that combines the genetic
information from two different parents to produce offspring
that are genetically unique.
Sexual Reproduction: Genetic variety
• Brothers may look similar, and look something like their
parents, but neither one is exactly the same as anyone else in
their family. (Unless they are identical twins!! This is a special
case)
Sexual Reproduction: Genetic variety
• Since sexual reproduction creates unique individuals, it
increases the genetic variety in a species. It is like
shuffling DNA around without ever knowing exactly what
the combination will be.
Sexual Reproduction: Genetic variety
• This can give some individuals a better chance of surviving!
Unfortunately, sometimes it makes others less likely to
survive!
• Overall this can help the species to survive in changing
environments.
Sexual Reproduction: The Role of Gametes
• You have 46 chromosomes in each of your body cells:
• They are found in 23 pairs of similar chromosomes.
• In each pair, one chromosome came from your father and one
came from your mother.
Sexual Reproduction: The Role of Gametes
In Section 5.1, you learned that Mitosis is the process of
cell division that creates genetically identical cells. Body
cells formed by mitosis are known as Diploid cells.
Diploid cells: same # of chromosomes as the parent cell (46 in
humans)
If humans reproduced through mitosis like
Bacteria or Fungi, we would all have exactly the
same 46 chromosomes (with the occasional
mutation).
So what makes us unique?
Sexual Reproduction: The Role of Gametes
Sexual reproduction involves combining cells called gametes.
Sexual Reproduction: The Role of Gametes
• Gametes: cells that combine during sexual reproduction.
Sperm in males and eggs in females. They are haploid cells.
Haploid Cells: half the number of chromosomes as normal body
cells (23 in human gametes)
Diploid
• Formed by mitosis
• Same # of chromosomes as
parent cells
• Humans = 46 chromosomes
• Body cells
Haploid
• Formed by meiosis
• Half the # of chromosomes
as parent cells
• Humans = 23 chromosomes
• Sperm and eggs (gametes)
Fertilization: a sperm
cell penetrates an egg
cell and the 23
chromosomes in each
combine to create a new
diploid cell called a
zygote
• Zygote: The diploid cell formed as a result of fertilization.
• Embryo: A zygote
that is growing larger.
It creates more cells
through mitosis.
• Salmon Reproduction
In Nature
Aquaculture
MEIOSIS: HOW GAMETES ARE FORMED
Meiosis: How Gametes are Formed
• Meiosis: the process through which gametes are created
from diploid cells. It involves two cell divisions (Meiosis I and
Meiosis II)
• Meiosis occurs in the sex organs: - testicles in males (sperm)
- ovaries in females (eggs)
• Meiosis must create haploid cells. If sperm and eggs
were diploid they would combine to create a zygote with
twice the number of chromosomes as the parents (92
instead of 46)!
Meiosis occurs in two distinct stages: Meiosis I and Meiosis II
Meiosis I
i) Prophase I
ii) Metaphase I
iii) Anaphase I
iv) Telophase I
Interkinesis
- cell grows and
makes various
proteins
Meiosis II
i) Prophase II
ii) Metaphase II
iii) Anaphase II
iv) Telophase II
Meiosis: How Gametes are Formed
• Meiosis Video
Comparing Mitosis and Meiosis
Homologous
Chromosomes
Homologous
Chromosomes
Mitosis
Meiosis
Type of Cells
In body cells
In sex organs to produce
sex cells (gametes)
Number of
Daughter Cells
Produced
Two daughter cells
Four daughter cells
Genetic Material in Same # of chromosomes
each Cell
as in parent cell
Genetically identical cells
Half the # of
chromosomes as in the
parent cell
Genetically different cells.
Function
Grow new body cells or
replace dead/damaged
cells.
Creating haploid cells for
sexual reproduction.