Chapter 4: Reproduction of Organisms

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Chapter 4 Reproduction of Organisms

• Life Science
• 7th grade

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Inquiry

• Do you think ALL living things have two parents?
• What might happen if the penguins (on the chapter
  cover photo) did not reproduce?
• Why do you think living things reproduce?

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Bell work Ch4. L1

• Sexual reproduction reproduction in which the
  genetic materials from two different cells
  combine, producing an offspring.
• Egg female sex cell that forms in the ovary.
• Sperm male sex cell that forms in the testis.
• Fertilization the process during which an egg
  cell and a sperm cell join together to form a new
  cell.
• Zygote The new cell that is formed as a result
  of fertilization.
• Diploid cell Cells that have pairs of
  chromosomes
• Homologous chromosomes pairs of chromosomes that
  have genes for the same trait arranged in the
  same order
• Haploid cell Cells that only have one chromosome
  from each pair
• Meiosis The process by which one diploid cell
  divides to make four haploid cells

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Launch Lab (work in pairs)

• Each pair gets one male parent and one female
  parent bag
• Without looking in the bag, select three beads
  from each bag.
• Record bead colors from each bag
• The six beads you pulled represent one offspring
  (x4)
• Put beads back in respective bags after each
  offspring

Offspring 1 Offspring 2 Offspring 3 Offspring 4
Male bag
Female bag
1- How are the offspring similar? How are they
different? 2- Why were there differences between
offspring? Are differences beneficial? Why or why
not?
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What is sexual reproduction?

• Reproduction in which the genetic materials from
  two different cells combine, producing an
  offspring.
• Those cells are called sex cells
• Sex cells form in reproductive organs
• What are sex cells in humans and where do they
  form?

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Sex cells

• Egg
• Female sex cell
• Forms in ovary
• Sperm
• Male sex cell
• Forms in testis

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Fertilization

• An egg cell and a sperm cell join together
• This forms a new cell
• Zygote new cell that forms from fertilization
• Develops into an organism
• What process is responsible for the development
  of a zygote into an organism?

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Diploid cells

• Cells that have pairs of chromosomes
• Similar chromosomes occur in pairs
• This happens in body cells
• Diploid cells are produced via mitosis
• Video

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Chromosomes

• Homologous chromosomes pairs of chromosomes that
  have genes for the same trait arranged in the
  same order
• One from mom, one from dad make up a pair
• NOT IDENTICAL DIFFERENT FROM SISTER
  CHROMATIDS.
• Video

DO YOU THINK A MORE COMPLICATED ORGANISM HAS MORE
CHROMOSOMES THAN A SIMPLER ORGANISM?
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How many chromosomes?

• Human body cells have 23 pairs of chromosomes 46
  total chromosomes
• Number of chromosomes does NOT correlate with how
  complicated an organism is
• Dog has 78, Fern has 1,260 chromosomes

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Haploid cells

• Cells that only have one chromosome from each
  pair (in humans have 23 total, not 46 total)
• Sex cells are haploid
• Haploid cells are produced via meiosis

ONE STEP UP WHY do you think sex cells are
haploid?
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Meiosis overview

• Many similarities to mitosis
• Mitosiscytokinesis one division of nucleus
  one division of cytoplasm
• End result Two diploid cells
• Meiosis TWO divisions of nucleus and TWO
  divisions of cytoplasm
• End result FOUR haploid cells
• Happens in two phases- meiosis I and meiosis II
• Video

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Meiosis - phases

• Interphase- EXACTLY THE SAME AS IN MITOSIS.
  Period of growth and replication. Chromosomes are
  duplicated and each duplicated chromosome has two
  sister chromatids joined at the centromere.
• This only happens once

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Meiosis I - phases

• Prophase I chromosomes condense, homologous
  chromosomes form pairs. Nuclear envelope breaks
  apart, nucleolus disappears.

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Meiosis I - phases

• Metaphase I Homologous chromosomes line up along
  the middle of the cell. Spindle fiber attaches to
  centromere.

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Meiosis I - phases

• Anaphase I Chromosomes pairs (homologous
  chromosomes) are pulled apart. SISTER CHROMATIDS
  STAY TOGETHER.

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Meiosis I - phases

• Telophase I Nuclear membrane reappears around
  PAIRS of chromosomes, nucleolus reappears.
  Cytoplasm divides through cytokinesis. Two
  daughter cells form.

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Meiosis II - phases

• NO SECOND INTERPHASE. Daughter cells from meiosis
  I immediately undergo meiosis II
• Prophase II Because no replication, chromosomes
  stayed as thick sister chromatids
• Nuclear envelope breaks down
• Nucleolus disappears.

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Meiosis II - phases

• Metaphase II
• Sister chromatids line up along the middle of the
  cell
• Spindle attaches to centromere.

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Meiosis II - phases

• Anaphase II Sister chromatids pulled apart and
  move toward opposite ends of the cell

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Meiosis II - phases

• Telophase II
• Nuclear membrane forms around chromosomes
• cytoplasm divides via cytokinesis.
• Result four haploid cells.

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Meiosis

• Video

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Meiosis summary
Interphase Cell growth and replication. Sister chromatids attached at centromere.
Prophase I Homologous chromosomes form pairs, nuclear membrane breaks apart, nucleolus disappears
Metaphase I Homologous chromosomes line up in center of cell, spindle fiber attaches to each chromosome
Anaphase I Homologous chromosomes pulled apart towards opposite ends of the cell. SISTER CHROMATIDS stay together.
Telophase I Nuclear membrane forms around sister chromatids, cytokinesis divides cytoplasm. Two daughter cells formed.
Prophase II Nuclear membrane breaks apart, nucleolus disappears.
Metaphase II Sister chromatids line up along metaphase plate, spindle fiber attaches to centromere.
Anaphase II Sister chromatids pulled apart towards opposite ends of cell.
Telophase II Nuclear envelope reappears around individual chromosomes, nucleolus reappears. Cytokinesis divides cell.
End Result FOUR haploid cells
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Why is meiosis important?

• Maintains diploid cells
• When haploid cells join (via fertilization) they
  make a diploid cell zygote.
• Zygote then divides via mitosis to make the
  organism
• Creates haploid cells
• Maintains correct number of chromosomes in sex
  cells so when they join, they form a zygote with
  the correct number of chromosomes

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Mitosis vs Meiosis (table p.122)
Characteristic Meiosis Mitosis and Cell division
Number of chromosomes in parent cell Diploid Diploid
Type of parent cell Reproductive Body
Number of divisions of nucleus 2 1
Number of daughter cells produced 4 2
Chromosome number in daughter cells Haploid Diploid
Function Forms sperm and egg cell Growth, cell repair, some kinds of reproduction
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Advantages of sexual reproduction

• Genetic variation
• Inherit different genes from parents compared to
  siblings
• Occurs in all organisms that reproduce sexually
• Includes plants
• Selective breeding
• Choose the traits you like (breed individuals
  with those traits) and over time those can become
  dominant
• Video

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Disadvantages of sexual reproduction

• Takes time and energy
• Search for mate can be problematic
• Expose to predators, disease or harsh
  environments
• Limitations
• Gestational period (pregnancy)
• Cant get pregnant while already pregnant, have
  to wait for one to finish before can start
  another one

ONE STEP UP Can you think of a way some
organisms overcome the gestational limitation?
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HOMEWORK Ch4 L.1

• Vocabulary words on flash cards
• Memorize for quiz
• Lesson review questions p.126 1-10
• Outline lesson 1
• Quiz lesson 1

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Meiosis lab p.138

• Lets recreate mitosis and meiosis using pool
  noodles
• 8 volunteers to be chromosomes
• Each person gets one
• 8 volunteers to be nuclear envelope
• Surrounds chromosomes
• 8 volunteers to be spindle
• 8 volunteers to be narrators/puppeteers

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Bell Work Ch4 L.2

• Asexual reproduction the process by which one
  parent organism produces offspring WITHOUT
  meiosis and fertilization
• Fission cell division in prokaryotes that forms
  two genetically identical cells
• Budding the process by which a new organism
  grows by mitosis and cell division on the body of
  its parent.
• Regeneration occurs when an offspring grows from
  a piece of its parent
• Vegetative reproduction a form of asexual
  reproduction in which offspring grow form a part
  of a parent plant
• Cloning a type of asexual reproduction performed
  in a laboratory that produces identical
  individuals from a cell or from a cluster of
  cells taken from a multicellular organism

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Yeast launch lab p.129

• I warmed water to 34C (93F)
• I added 5g yeast and 5g sugar
• What does the mixture look like initially? After
  5 minutes?
• Drop of solution onto slide (cover with cover
  slip)
• Draw what you see under microscope.
• Evidence of reproduction?
• TURN THIS IN

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What is asexual reproduction?

• One parent organism produces offspring WITHOUT
  meiosis and fertilization.
• Inherit all DNA from one parent
• What are some advantages/disadvantages of
  reproducing this way?
• Mold a type of fungus that can reproduce
  sexually OR asexually. (fuzzy stuff on old food)
• Bacteria, protists, plants and some animals can
  reproduce asexually

ONE STEP UP How do parent/daughter cells compare
to each other in asexual reproduction?
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Types of asexual reproduction

• Fission cell division in prokaryotes that forms
  two genetically identical cells.
• Prokaryotes DNA is copied
• Each copy attaches to cell membrane
• Cell elongates, pulling copies of DNA apart
• Cell membrane pinches inward along middle of the
  cell
• Cell splits and forms two new identical offspring
  
• Example E.coli

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Types of asexual reproduction

• Mitotic cell division used by unicellular
  eukaryotes
• Organism produces two offspring through mitosis
  and cell division
• Example amoeba

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Types of asexual reproduction

• Budding a new organism grows by mitosis and cell
  division on the body of its parent.
• Bud is genetically identical to parent
• When bud gets big enough, it can break off from
  parent
• Example hydra (multicellular organism), yeast
  (unicellular organism).

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Types of asexual reproduction

• Animal regeneration occurs when an offspring
  grows from a piece of its parent. (varies
  greatly among animals)
• Producing new organisms each new organism is
  identical to starting organism
• Example planarian (can cut in half and each half
  makes a new organism), sea star (can cut an arm
  and if it contains part of central disk and
  conditions are right, that arm will make a whole
  new star)

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Types of asexual reproduction

• Animal regeneration contd
• Producing new parts regeneration
• Common in animals. Humans can regenerate skin or
  liver, some animals can regenerate limbs.
• THIS IS NOT CONSIDERED ASEXUAL REPRODUCTION
  BECAUSE IT DOES NOT PRODUCE A NEW ORGANISM

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Types of asexual reproduction

• Vegetative reproduction a form of asexual
  reproduction in which offspring grow form a part
  of a parent plant.
• Parent plant can grow long stems called stolons
• If a stolon touches the ground, it forms roots.
• Once roots are down, a new plant can grow.
• If stolon is broken from parent plant, the new
  plant can survive on its own.
• Example strawberries, raspberries and potatoes.

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Types of asexual reproduction

• Cloning a type of asexual reproduction performed
  in a laboratory that produces identical
  individuals from a cell or from a cluster of
  cells taken from a multicellular organism.

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Types of asexual reproduction

• Plant cloning do via tissue culture.
• Use cells from meristem to grow new plants in lab
• Animal cloning (Example sheep)
• Take cell from sheep 1, take unfertilized egg
  from sheep 2
• Remove DNA from unfertilized egg (its an empty
  egg now)
• Fuse cell from sheep 1 with empty egg from sheep
  2
• Cell develops into embryo in laboratory
• Implant embryo into sheep 2
• Sheep 2 gives birth to clone of sheep 1
• Video

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Advantages of asexual reproduction

• Dont need a mate
• Rapidly produce a large number of offspring

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Disadvantages of asexual reproduction

• Genetically identical to parent little variation
  within a population
• Variation can give better chance of survival
• Mutations
• Harmful mutations will be passed on to all
  offspring

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HOMEWORK Ch4 L.2

• Vocabulary wordsß on flash cards
• Memorize for quiz
• Lesson review questions p.137 1-9
• Outline lesson 2
• Quiz lesson 2
• OPTIONAL Extra credit (due on test day)
  p.141-145 (all)
• You MUST write the entire question and answer
  down for credit. Only answers will NOT be
  accepted.