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Topic: Reproduction and Development Aim: How do cells divide? Do Now: Explain the differences between sexual and asexual reproduction. What types of things reproduce sexually? Asexually? HW: PAGE 96-97 10 MAIN POINTS & FINISH HANDOUT What are the two types of reproduction? • Asexual reproduction MITOSIS • Sexual reproduction MEIOSIS What is ASEXUAL Reproduction? • Requires one parent that divides – Asexual “A”parent • Offspring are identical to parents • Same # of chromosomes How does ASEXUAL reproduction occur? • MITOSIS – cell division • One cell divides into two identical daughter cells (same # of chromosomes as parent) • Occurs in all body cells EXCEPT sex cells What are the steps of Mitosis? • • • • • Interphase Prophase Metaphase Anaphase Telophase – Cytokinesis Interphase CHROMATIN The mass of DNA inside the nucleus during interphase is known as CHROMATIN. Prophase Metaphase Anaphase Telophase What are the steps of Mitosis? 1. INTERPHASE: cell grows to mature size 2. 3. 4. 5. and chromatin replicate (makes copy of DNA) PROPHASE: chromatin forms chromosomes, nuclear membrane disappears and spindle fibers form METAPHASE: chromosomes line up in the Middle of the cell ANAPHASE: chromosomes separate and move Away from each other TELOPHASE: nuclear membrane starts to form What is Cytokinesis? • Part of telophase • Cell membrane pinches in (cytoplasm separates) resulting in 2 new cells CYTOKINESIS How is mitosis different in plant cells? 1. Cell membrane DOES NOT pinch in • Instead a CELL PLATE forms between 2 new cells 2. Plant cells do not have centrioles (animal cells do) CELL PLATE Cytokinesis – Animal and Plant What is Cancer? • Abnormal and uncontrolled cell division What are the different types of ASEXUAL Reproduction? 1. Binary Fission – one celled organism divides into two identical cells (mitosis) • • Binary Fission means “equal division” Examples: ameba and paramecia 2. Budding – unequal division of organisms • Examples: hydra, yeast 3. Sporulation – spores (specialized cells) develop into new organisms (mitosis) • Examples: mold, mushrooms What are the different types of ASEXUAL Reproduction? 4. Vegetative Propagation – Asexual reproduction used by plants a. Runners (strawberries) b. Buds (potatoes) c. Grafting (roses) d. Bulbs (onions) Binary Fission & Budding BINARY FISSION BUDDING Sporulation Vegetative Propagation RUNNERS GRAFTING BUDS BULBS Topic: Reproduction and Development Aim: What is sexual reproduction? Do Now: Why does sexual reproduction require two parents? What is sexual reproduction? • Requires 2 parent cells, each with half the normal number of chromosomes • Involves sex cells • Human: sperm + egg → zygote 23 + 23 → 46 What is meiosis? • Cell division occurs only in sex organs to produce sex cells (sperm and egg) • Produces 4 daughter cells with half the number of chromosomes as parent cell (23 in humans) • 2 divisions (1 → 2 → 4) Meiosis How does meiosis occur in males? • Occurs in testes to produce sperm • Produces 4 new sperm cells How does meiosis occur in females? • Occurs in ovaries • Produces 1 egg cell and 3 polar bodies What is fertilization? • Union of egg and sperm to form a zygote • Two types: • Internal fertilization: occurs inside the female (humans) • External fertilization: occurs outside the female (frogs); can occur on land or in water What happens to the zygote after fertilization? • Zygote divides by MITOSIS to form 3 layers that will develop into different parts of the embryo 1. Outer layer: forms the skin and nerves 2. Middle layer: forms muscles 3. Inner layer: forms heart and stomach Outer layer Middle layer Inner layer