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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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t he cell theor y
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
so what s the difference
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

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

cell organelles continued
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

cell organelles continued1
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

cell division

Cell Division

Part One: Mitosis

in the nucleus
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
draw a double stranded chromosome label chromosome chromatid and centromere
Draw a double stranded chromosome. Label chromosome, chromatid and centromere





  • 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
phase one prophase
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
phase two metaphase
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
phase three anaphase
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
phase four telophase
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
  • 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)
what s the point of mitosis
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)
asexual reproduction
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
binary fission
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
  • 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
  • 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
  • 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
vegetative reproduction
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
  • short underground stem with thickened storage leaves
  • small new bulbs sprout from the old ones
  • Eg. onions, tulips
  • short underground stems with no fleshy leaves
  • Eg. gladiolas, crocuses
  • enlarged part of an underground stem that contains stored food
  • potatoes (eyes are tiny buds)
  • AKA stolon
  • is a stem that runs sideways and contains buds
  • Eg. strawberry
  • a stem that grows sideways under the ground
  • ferns, irises
  • a stem, root or leaf cutting used to make a new plant
  • part of a stem is bent and covered in soil
  • once it roots the original can be cut off
  • Eg. raspberries, roses
  • stem or bud removed from one plant and permanently joined to another plant
  • Eg. grapes and many seedless fruits