Transcript Cells
Hierarchy of Living Organisms Levels of Organisation What are CELLS? • Microscopic units that make up all living things – (microscopic = too small to see, need the help of a microscope) • Are alive • Reproduce • Grow Cell Theory • Three major ideas based on experiments by Brown, Schleiden, and Schwann: 1. 2. All living things are made of cells Cells are the basic unit of structure and function in living things 3. New cells are made by existing cells Cells • Simple – no nucleus– prokaryotes: bacteria • More complex – have a nucleus (a special compartment that contains the genetic material – DNA) and organelles – eukaryotes: plant and animal cells Unicellular Organisms • Unicellular organisms have ONLY one cell. – The one cell carries out all the functions, does all the jobs – Example: Amoeba, Euglena, Paramecium, Yeast Multi-cellular Organisms • Made up of many cells – Cells are specialized – The cells in each group do a specific job/ have a specific function – This is called the Division of Labor • Example: cells that line the small intestine make the villi – needed for greater absorbtion Levels of Organization Each level of organization builds on the level below it but often demonstrates new features. Emergent properties: new properties present at one level that are not seen in the previous level Emergent property - Homeostasis 7 Atom • The most basic unit of matter • Subatomic particles – Nucleus contains protons and neutrons – Electrons orbit nucleus • Ex: An oxygen atom (8 protons, 8 neutrons, 8 electrons) Molecule • Group of atoms held together by bonds Organelle • Structure within cell that perform specific function Cell • The most basic unit of life • Some organisms are unicellular (bacteria); others are multicellular (plants, animals, fungi) Tissue • Group of similar cells that perform a specific function Plant Tissues: epidermis, palisade and spongy mesophyll, xylem, phloem epidermis palisade mesophyll photosynthesis xylem water and mineral intake phloem sugar and amino acid export spongy mesophyll evaporative cooling (photosynthesis) epidermis regulates water loss and gas exchange http://gecko.gc.maricopa.edu/~lsola/Leaf/Leafxs.jpg window, lens Organ • A structure usually composed of several tissue types that form a functional unit blade petiole Organ System • Two or more organs working together to perform a specific function • Ex: branch with stem, buds, petioles, leaves Organism • Individual living thing • Unicellular or multicellular Cellular Organization • Cells Tissues Organs Organ Systems • Cells make tissues, tissues make organs, organs make organ systems Division of Labor • In single celled organisms the one cell has to do every job. • In multi-cellular organisms the cells are specialized or differentiated to perform different jobs – This division of the jobs among different tissues, organs, and organ systems is known as the division of labor or differentiation Cell Development • Changes that take place in cells as they develop is called differentiation • Cells differentiate in organisms to perform different functions • Cells differentiate for Stem Cells • Cells take on particular forms for particular functions – Example: nerve cells differentiate into a form that can conduct electrical impulses Stem Cells Cells that are not specialized, undifferentiated – can become specialized, turn into different cell types Fertilized egg (zygote) – ultimate stem cell – can and will become many different types of cells with different functions Embryonic Stem cells Fetal stem cells After 8 weeks embryo is called a Fetus Cord blood stem cells Umbilical cord after birth is a valuable source of stem cells. Adult Stem cells Our Bodies have a limited number of stem cells that can differentiate (become specialized) – Adult stem cells The process of Differentiation: Unspecialized Undifferentiated Stem cell becomes Specialized Differentiated Specialized