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Reproduction

Reproduction. T he Cell Theor y. The 4 main points of the cell theory are: All living organisms are made of one or more cells Cells are the basic unit of structure and function in all organisms All cells come from previously existing cells

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Reproduction

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  1. Reproduction

  2. The Cell Theory • The 4 main points of the cell theory are: • All living organisms are made of one or more cells • Cells are the basic unit of structure and function in all organisms • All cells come from previously existing cells • Organisms are controlled by single cells working together

  3. Animal Cells

  4. Plant Cells

  5. So what’s the difference? • Plant cells – rigid cell wall which provides structure and support for the cell • Plant cells – have chloroplasts that enable them to make their own food through photosynthesis

  6. Organelles A typical cell has many organelles, specialized structures that perform specific functions in the cell Nucleus – the control center of the cell Nuclear Membrane – encloses the cells genetic material or DNA (Deoxyribonucleic Acid) Nucleolus – darker area within the nucleus that makes ribosome parts

  7. Cell Organelles Continued… Ribosomes – small, cell structures involved in the making of proteins Cell Membrane – the membrane that holds all the cell contents together Cytoplasm – the gel-like substance within the cell that supports the structures of the cell

  8. Cell Organelles Continued… Endoplasmic Reticulum – transports materials to different parts of the cell Mitochondrion – an oval-shaped organelle that makes energy for a cell to use. The power-house of the cell Golgi Body – packages and moves (secretes) waste out of a cell Vacuole – stores water, food, wastes and other materials in the cell Lysosome – breaks down food, wastes and worn-out cell parts

  9. Cell Division Part One: Mitosis

  10. In the nucleus • In non-dividing cells, the genetic material is stored as thin DNA super coils called CHROMATIN • When a cell divides, the chromatin will shorten and thicken into CHROMOSOMES • One strand of a double stranded chromosome is called a CHROMATID

  11. Draw a double stranded chromosome. Label chromosome, chromatid and centromere Chromatid Chromosome Chromatid Centromere

  12. Mitosis • MITOSIS: a process by which the nucleus of a cell divides while maintaining the chromosome number • One cell  two cells • New cells have identical genetic material (DNA) of the parent cell • Four stages of division (Prophase, Metaphase, Anaphase and Telophase - PMAT) plus a period of growth and metabolism called Interphase

  13. The Cell Cycle

  14. Phase One: Prophase • Chromatin contracts and becomes visible (spaghetti). It is now called CHROMOSOMES • Each is a double chromosome with a pair of SISTER chromatids which are joined to each other by a centromere • Chromosomes begin to move towards the equator (center) of the cell • Nuclear membrane disintegrates (breaks down) • CENTRIOLES will form SPINDLE FIBERS that will attach to each centromere and move around the chromosomes

  15. Prophase

  16. Phase Two: Metaphase • The centromeres of each chromosome line up along equator ( looks like praying hands) • Centromeres divide so the doubled chromosomes become two identical single stranded sister chromatids • Centrioles are now at the poles of the cell and are attached to each centromere by spindle fibers

  17. Metaphase

  18. Phase Three: Anaphase • The spindle fibers begin to shorten and the chromosomes begin moving to opposite ends or poles of the cell (fingers) • Each side gets one chromatid from each double stranded chromosome

  19. chromosomes Anaphase

  20. Phase Four: Telophase • Begins when single stranded chromosomes reach the poles • Chromosomes uncoil and turn into chromatin • Nuclear membrane reappears • Reverse of prophase • Division of the cytoplasm or CYTOKINESIS is completed by pinching off in animals or by building a cell wall in plants

  21. Telophase

  22. Interphase • Period between divisions • Longest part of the cell cycle • Cell is growing and metabolizing • Nuclear membrane present • Genetic information in the form of chromatin and cannot be seen with a microscope • Before division each strand of DNA will replicate (copy) itself to become double stranded • Near the end of interphase the DNA begins to condense (shorten)

  23. Interphase

  24. What’s the point of Mitosis? • Mitosis creates identical copies of cells for: • 1. growth • 2. Repair/regeneration of damaged tissue • 3. Asexual reproduction (animals) or vegetative reproduction (plants)

  25. Asexual Reproduction • Reproduction that involves only one parent; parent and offspring have identical genetics • No special reproductive cells or organs used to create offspring • Occurs through mitosis and cytokinesis • Both single and multi-celled organisms, plants and simple animals can reproduce asexually • In multi-cellular organisms, the offspring develop from undifferentiated, unspecialized cells from the parent • Usually a rapid form of reproduction

  26. Binary Fission • Simplest form of asexual reproduction • Parent divides into two approximately equal sized daughter cells • Bacteria: circular chromosome attaches to plasma membrane then replicates, cell wall separates each copy • Protozoa: eg. Amoeba become circular and use mitosis

  27. Budding • New individuals develop from small outgrowths of the parent (buds) • May develop colonies (sponges) or break off to be individuals (hydra, yeast) • Some organisms can both bud and reproduce sexually

  28. Spores • Specialized single cells that are released from the parent organism, germinate and grow by mitosis • New cells differentiate to form a new organism • Can reproduce quickly and in large quantities • Often have thick protective coats • Eg. Fungi, algae, protozoa

  29. Regeneration • The ability to regrow lost body parts • Some animals can regrow entire new organisms from parts • Ability to regenerate decreases as organisms increase complexity • Even simple organisms that can regenerate entire organisms generally prefer to utilize a differentmethod to reproduce

  30. Vegetative reproduction • MERISTEM: area on plant with unspecialized cells (cells that can become any kind of cell) that frequently divide using mitosis • Meristematic cells can be found in the vegetative structures of a plant (roots, stems, leaves) • Given proper treatment, meristem cells can reproduce mitoticlly then differentiate into new independent plants • Structures include bulbs, corms, tubers, runners, rhizomes • Can also be artificially propagated using cuttings, layerings or grafting

  31. Bulb • short underground stem with thickened storage leaves • small new bulbs sprout from the old ones • Eg. onions, tulips

  32. Corm • short underground stems with no fleshy leaves • Eg. gladiolas, crocuses

  33. Tuber • enlarged part of an underground stem that contains stored food • potatoes (eyes are tiny buds)

  34. Runner • AKA stolon • is a stem that runs sideways and contains buds • Eg. strawberry

  35. Rhizome • a stem that grows sideways under the ground • ferns, irises

  36. Cutting • a stem, root or leaf cutting used to make a new plant

  37. Layering • part of a stem is bent and covered in soil • once it roots the original can be cut off • Eg. raspberries, roses

  38. Grafting • stem or bud removed from one plant and permanently joined to another plant • Eg. grapes and many seedless fruits

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