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Chapter 4: Reproduction of Organisms

Chapter 4: Reproduction of Organisms. Life Science 7th grade. 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?. Bell work Ch4. L1.

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Chapter 4: Reproduction of Organisms

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  1. Chapter 4: Reproduction of Organisms Life Science 7th grade

  2. 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?

  3. 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

  4. 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 1- How are the offspring similar? How are they different? 2- Why were there differences between offspring? Are differences beneficial? Why or why not?

  5. 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?

  6. Sex cells • Egg • Female sex cell • Forms in ovary • Sperm • Male sex cell • Forms in testis

  7. 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?

  8. 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

  9. 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.****** DO YOU THINK A MORE COMPLICATED ORGANISM HAS MORE CHROMOSOMES THAN A SIMPLER ORGANISM?

  10. 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

  11. 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

  12. Meiosis overview • Many similarities to mitosis • Mitosis+cytokinesis = 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

  13. 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

  14. Meiosis I - phases • Prophase I: chromosomes condense, homologous chromosomes form pairs. Nuclear envelope breaks apart, nucleolus disappears.

  15. Meiosis I - phases • Metaphase I: Homologous chromosomes line up along the middle of the cell. Spindle fiber attaches to centromere.

  16. Meiosis I - phases • Anaphase I: Chromosomes pairs (homologous chromosomes) are pulled apart. SISTER CHROMATIDS STAY TOGETHER.

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

  18. 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.

  19. Meiosis II - phases • Metaphase II: • Sister chromatids line up along the middle of the cell • Spindle attaches to centromere.

  20. Meiosis II - phases • Anaphase II: Sister chromatids pulled apart and move toward opposite ends of the cell

  21. Meiosis II - phases • Telophase II: • Nuclear membrane forms around chromosomes • cytoplasm divides via cytokinesis. • Result= four haploid cells.

  22. Meiosis summary

  23. 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

  24. Mitosis vs Meiosis (table p.122)

  25. 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

  26. 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) • Can’t 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?

  27. 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

  28. Meiosis lab p.138 • Let’s 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

  29. 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

  30. Yeast launch lab p.129 • I warmed water to 34˚C (93˚F) • 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

  31. 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?

  32. Types of asexual reproduction • Fission: cell division in prokaryotes that forms two genetically identical cells. • Prokaryote’s 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

  33. Types of asexual reproduction • Mitotic cell division: used by unicellular eukaryotes • Organism produces two offspring through mitosis and cell division • Example: amoeba

  34. 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).

  35. 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)

  36. Types of asexual reproduction • Animal regeneration cont’d • 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

  37. 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.

  38. 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.

  39. 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 (it’s 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

  40. Advantages of asexual reproduction • Don’t need a mate • Rapidly produce a large number of offspring

  41. 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

  42. 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.

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