AP February 9, 11
Journal: The “snout” of a frog tadpole bears a
sucker. A salamander tadpole has a mustacheshaped structure called a balancer in the same area.
If ectoderm from the side of a salamander embryo is
transplanted to the snout of a frog embryo, the frog
tadpole later has a balancer. If ectoderm is
transplanted from the side of a slightly older
salamander embryo to the snout of a frog embryo,
the frog tadpole ends up with a patch of salamander
skin on its snout. Explain the results of this
experiment in terms of animal development.
Development in the frog embryo
Cleavage…succession of rapid cell divisions, G1 and G2 are
skipped so the cell size gets smaller and smaller
Morula…solid ball of cells until a fluid cavity called a blastocoel
develops
Blastula…hollow ball of cells
Gastrulation…the development of the three tissues layers due to
migration of cells called invagination. A blastopore develops and
leads to an archenteron
Neurulation…development of the notochord and nerve cord. The
notochord develops from the mesoderm, while the nerve cord
develops from the ectoderm. The notochord serves as a support in
lower chordates, but in frogs and higher chordates provides the
attachments for the spine and associated muscles of the
vertebrae.
From Campbell site…signal transduction
Organogenesis
Ectoderm
Mesoderm
Endoderm
How are cells joined together?
Desmosomes-plaque-like structures
made up of cytoskeleton fibers from
one cell into the other
Tight junctions-fusing of the
phospholipid bilayer
Gap junctions-protein pores from one
cell into another cell
How are tissues’ structure
related to their function?
Major Tissue Types
Epithelial
Nerve: neuron
Connective
Muscle: skeletal, smooth, cardiac
Bone
Blood
Adipose
Cartilage
Fibrous Tissue:Tendons and ligament
Cubodial Epithelial
Columnar Epithelial
Skeletal (striated) note sacromere
crossbridges
Smooth muscle
Cardiac Muscle-note intercalated
discs
Neurons
Bone-note Haversian canal