Quick Look at the Levels of Biological Organization.
biosphere is the region on, below, and above the Earth's
surface where life exists. Living things can be found well into the atmosphere,
the deepest parts of the ocean, and at least in some areas, microbes live
in rock several kilometers below the surface of the earth.
Earth contains numerous ecosystems. Ecosystems are distingushable
groups of species and the abiotic(non-living) components of the environment
with which the living creatures interact. Examples of ecosystems include
ponds, forests, prairies.
community is all the populations of different species living and
interacting together in a distinct area. (e.g: all the species in a prarie)
Abiotic means the nonliving parts of this distinct area which interact
with the community. These two make up the ecosystem. For instance the particles
of sand silt or clay in prairie soil are abiotic components of the prairie
is the technical name given for a kind of organisms for example all people
are considered to be one species distinct from other primates based on
common appearence and more importantly that all races can and do interbreed
with each other.
population is group of freely interacting and breeding individuals
of the same species. For example, all the bull frogs in a pond can be considered
a population of bullfrogs. Typically populations are subdivided into smaller
groups: a pack of wolves, pride of lions, colony of ants.
organism or individual is that level of biological organisation
that has its own distinct existance as a complex, self reproducing unit.
We are multicellular organisms in that we are made of many highly specialized
cells which cannot exist independently of other cells in the organism.
Many organisms are unicellular, that is consist of a single independent
organisms, especially animals typically are organized into organ
systems, groups of organs that function together to carry out broad
sets of functions. For instance an organ system in humans is the digestive
system. Some of the organs in the digestive system are the stomach, liver,
small intestine, pancreas.
are groups of tissues organised together to carry out a particular set
of functions. Organs typically have several kinds of tissue. The stomach
has an inner lining of tissue that secretes digestive enzymes
outside the stomach has several layers of muscle and connective tissue.
tissue is a group of distinct and similar cells that carry out a
specific set of functions. For example, muscle tissue is for contraction.
Connective tissue is tissue consisting of cells surrounded by a large amount
of non living material. Nerve tissue is for the conduction of nerve impulses
and secretion of specialised chemicals called neurotransmitters.
cell is the smallest unit of biological organisation that biologists
consider alive. All true cells are surrounded by a plasma membrane, carry
out complex chemical reactions, and are at least potentially capable of
self reproduction. Cells come in
a wide variety of shapes and sizes. Not all cells have a nucleus, but again
all true cells have genetic material in the form of DNA.
organ") area specialised structures inside of a cell. Often organelles
are "membrane bound" (surrounded by a plasma membrane) but not always!
Examples of organelles you will be come familiar with are the nucleus,
mitochondria, endoplasmic reticulum, chloroplast, cilium, vacuole. The
line between organelles and molecular assemblies is not clear. Sometimes
is not considered an organelle because it's not a membrane bound structure.
assemblies are large organised sets of molecular units that make
up parts of organelles. For example one common macromolecular assembly
is the microtubule which important in forming structures in the cell related
to maintaining the cell structure or related to cell movement. The cell(plasma)
membrane that surrounds many organelles, and the cell, is a highly
organised molecular assembly.
molecules are large molecules consisting of many subunits. Good
examples are starch molecules which consist of many glucose units,(Glucose
is a simple sugar) and proteins some of which consist of 1,000 or more
amino acids. amino
acids and proteins.
molecules I mean those molecules that are the small building blocks
from which larger molecules are made. Some of the basic building blocks
include; glucose, glycerol, amino acids, fatty acids, nucleotides. Some
of these smaller molecules have other functions than as building blocks.
are the smallest unit of matter that have the chemical properties of a
particular chemical element. Atoms of an element have the same number of
protons and electrons but two atoms of the same element may differ in terms
of the number of neutrons. Most of the atom is empty space, in the center
is the nucleus with the protons and neutrons, "Orbiting" the nucleus are
and protons are in the atomic nucleus. Protons have a positive electrical
charge, neutrons have no charge. Electrons
have a negative electrical charge. Electrons occurr in only certain energy
levels or shells and only so many electrons can occupy each energy level.
An important concept is that electrons
can carry and release energy. The last subatomic particle you need
is the photon. A photon is a packet of light
energy. It has no mass moves at the speed of light and is associated with
electrons in that electrons can absorb and release photons.
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Revised 05/3/01 pgd