Download Document

Earth Began as a Conglomeration
Dust and Gases were attracted to
each other because all mass has
some gravitational pull
Friction between the particles caused
an explosion
Meteor crashes bring more debris and
possible single celled organisms.
Earth’s harsh environment selects for
extremophiles
Some organisms evolve to survive in extreme
temperatures, others in extreme salts, and others in
harsh chemicals.
Mutations Provide Diversity
Blastula Development
• Blastula: ball of cells
formed in early
development of the
organism
• Single celled =
cytoplasmic*****no
cellular division of
labor, all chemical
reactions and cellular
functions take place
in the cytoplasm of
the cell
Diploblastic
• Cells are organized into tissues in which there
is a division of labor
• Very simple form of tissue organization
• Endoderm tissue in the embryo develops into
tissue that lines the gut
• Ectoderm tissue in
the embryo develops
into the outer layer
of the body wall
• Mesoglea – is found
between the other
two layers but does
not provide an
independent function
Hydra
Triploblastic
•
•
•
•
Three layers of embryonic tissue:
Endoderm
Ectoderm
Mesoderm: supportive tissue (bones),
contractile tissue (muscles) and blood cells are
formed from this layer
Types of Triploblastic Body Plans
• Acoelomate : no coelom present, solid mass
of mesoderm cells between endo and ecto
derm, no specialization of mesoderm cells
•
• Psuedoceolomate: body cavity present but not
completely lined by mesoderm, no muscle or
connective tissue in gut, no suspended organs
• Coelomate: body cavity is completely
surrounded by mesoderm, structures are
suspended in the body cavity ( ie…lungs,
stomach, pancreas…)connective tissues and
muscles are present
• Muscles and connective tissue increase organ
function (ie…muscle can contract in intestines
to move food through tract for better
absorption)