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