Cycles occur in nature.

1
Lesson 1
The Cell Cycle

• Cycles occur in nature.

• The life cycles of living organisms such as
  trees are affected by the change in seasons.

Bill Brooks/Alamy
2
Lesson 1
The Cell Cycle (cont.)

• Most cells in an organism go through a cycle of
  growth, development, and division called the cell
  cycle.

• There are two main phases in the cell
  cycleinterphase and the mitotic phase.

3
A LIFE CYCLE
What would a human life cycle look like?
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LETS MAKE. A FOLDABLE!
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MITOSIS
MEIOSIS
Growth, development, and repair (asexual)
Sexual Reproduction
6
6.1 Chromosomes and Meiosis

• Humans have 23 pairs 46 chromosomes

Genes NOT related to sex of an organism.
Relate to sexual characteristics
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Lesson 1
Different organisms have different numbers of
chromosomes.
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Lesson 1
Interphase (cont.)

• The cells DNA is copied arranged as pairs of
  identical chromosomes called sister chromatids.

• Sister chromatids are held together by a
  structure called the centromere.

9

• You have two types of cells. Somatic (body) cells
  and sex cells. What are the male and female sex
  cells called?

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6.1 Chromosomes and Meiosis

• Humans have 23 pairs 46 chromosomes

Genes NOT related to sex of an organism.
Relate to sexual characteristics
11
Lesson 1
46
46
46
12
Lesson 1
Haploid Cells

• Haploid cells are cells that have only one
  chromosome from each pair of chromosomes.

haploid from Greek haploeides, means single
13
Lesson 1
Diploid Cells

• Organisms that reproduce sexually form body cells
  and sex cells.
• In body cells of most organisms, similar
  chromosomes occur in pairs.
• Pairs of chromosomes that have genes for the same
  traits arranged in the same order are called
  homologous chromosomes.
• Diploid cells are cells that have pairs of
  chromosomes.

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Sex cells are ______________(haploid or diploid)
because they have _______ (46 or 23) chromosomes.
This is half the normal amount. Body cells are
_______________ (haploid or diploid) because they
have all ______ (46 or 23) chromosomes.
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6.1 Chromosomes and Meiosis

• HAPLOID

DIPLOID
16
2n
MITOSIS
MEIOSIS
Growth, development, and repair (asexual)
Sexual reproduction
n
n
2n
2n
17
Lesson 1
Haploid Cells (cont.)

• In meiosis, one diploid cell divides and makes
  four haploid sex cells.
• Meiosis occurs only during the formation of sex
  cells.
• Meiosis involves two divisions, meiosis I and
  meiosis II.

18
Lesson 1
What is sexual reproduction?

• Sexual reproduction is a type of reproduction in
  which the genetic materials from two different
  cells combine, producing an offspring.
• The female sex cell, an egg, forms in an ovary.
• The male sex cell, a sperm, forms in the testis.

19
Lesson 1
What is sexual reproduction? (cont.)
During a process called fertilization, an egg
cell and a sperm cell join together to create a
zygote.
20
Lesson 2
What is asexual reproduction?

• In asexual reproduction, one parent organism
  produces offspring.

21

• Plant pollination sexual or asexual?

BrainPOP Pollination
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• Mitosis / meiosis CARD SORT!

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• NOVA Interactive Animation
• http//www.pbs.org/wgbh/nova/body/how-cells-divide
  .html

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• Draw Mitosis and Meiosis stages in your foldable.

25
Lesson 1
The Phases of Meiosis (cont.)

• There are four phases of meiosis I.

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Lesson 1
The Phases of Meiosis (cont.)

• There are four phases of meiosis II.

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Lesson 1
Why is meiosis important? (cont.)

• The fertilized egg, formed when sex cells join
  together, divides by mitosis to create a diploid
  organism.

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Lesson 1
Why is meiosis important? (cont.)
Why is meiosis important?
29
Lesson 1
How do mitosis and meiosis differ?

• During mitosis and cell division, a body cell and
  its nucleus divide once and produce two identical
  cells.
• The two daughter cells produced by mitosis and
  cell division have the same genetic
  information.

30
Lesson 1
How do mitosis and meiosis differ? (cont.)

• During meiosis, a reproductive cell and its
  nucleus divide twice and produce four cellstwo
  pairs of identical haploid cells.
• Meiosis forms sex cells used for sexual
  reproduction.

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Lesson 1
How do mitosis and meiosis differ?

• Create a Venn Diagram. With your partner, come up
  with at least one thing for each category.

32
Lesson 1
Advantages of Sexual Reproduction

• Genetic variation occurs in all organisms that
  reproduce sexually.
• Due to genetic variation, individuals within a
  population have slight differences.

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Lesson 1
Advantages of Sexual Reproduction (cont.)

• Genetic variation may enable one plant to be more
  disease-resistant than another within the same
  species.

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Lesson 1
Advantages of Sexual Reproduction (cont.)

• Selective breeding has been used to develop many
  types of plants and animals with desirable traits.

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35
Lesson 1
Disadvantages of Sexual Reproduction

• Organisms have to grow and develop until they are
  mature enough to produce sex cells.
• Organisms must form sex cellseither eggs or
  sperm.