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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

Animal cells

Animal Cells

Plant cells

Plant Cells

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

The cell cycle

The Cell Cycle

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

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