process of gastrulation, where the embryonic tissues that will develop into adult body parts are produced.
what is the gastrula
the developmental stage following gastrulation
covers the surface and becomes the outer covering and in some phyla the central nervous system
is the innermost germ layer that lines the digestive tract and organs such as the lungs and liver in vertebrates
is the third layer (between the other two) forming muscles and most other organs
•Not all animals have mesoderm
Early Embryo Development in animals
Body plans are?
Sets of morphological and developmental traits
the dividing plane is called the saggital plane
Bilaterally symmetrical animals have
a Dorsal (top/back) side and a Ventral (bottom/front) side
a right and left side
Anterior (head) and Posterior (tail) ends
Cephalization- the development of a head
the development of a head
what is a germ layer
any of the 3 layers of cells differentiated in embryos following gastrulation
often in vertebrates
animals more complex than a sponge have at least 2
having only two germ layers
having three germ layers
common to all bilaterally symmetric animals
fluid or air filled space separating digestive tract from outer body wall
The body cavity of triploblastic animal
fluid-filled body cavity that allows inner organs to shift
what are animals with these called?
formed from mesoderm
Animals with a true coelom are coelomates
If the coelom is formed from both endo - and mesoderm tissue
triploblast lacks a body cavity
protostome (first mouth) development
–Cells are rigidly cast early in development
–Mesoderm cells split and then form A developmental mode distinguished by the development of the mouth from the blastopore; often also characterized by spiral cleavage and by the body cavity forming when solid masses of mesoderm split.
A pattern of animals with protostome development, in which the planes of cell division are diagonal to the vertical axis of the embryo.
A form of cleavage in which the developmental fate of each embryonic cell is cast very early.
Deuterostome (second mouth) development
•If very early embryo’s cells are removed they will produce a complete individual
–Coelom forms from mesoderm that buds from the archenteron
–The blastopore becomes the anus
A cleavage pattern found in deuterostomes, in which the cleavage planes are either parallel of perpendicular to the vertical axis of the egg, with tiers of cells aligned
A form of cleavage in which each cell produced retains the ability to develop into a complete embryo.
The central cavity of the gastrula, which ultimately becomes the intestinal or digestive cavity.
collections of specialized cells isolated by membranous layers
Almost all animals have tissues
Tissues arise from germ layers
protostome and deuterostome development
how long have animals been on earth
–Some estimates place the ancestors diverging from fungi about 1 billion years ago
–Others place it at 675-875 million years ago
Morphological and molecular evidence suggests choanoflagellates are the closest living relatives to animals
1 BYA –542 MYA
565 to 550 million years ago
–Cambrian Explosion about 530 MYA
–First fossils of arthropods, chordates and echinoderms
251 –65.5 MYA
–DINOSAURS (and other animals)
coral reefs formed
what era came after the Mesozoic era
65.5 MYA to present
Almost all animal phyla appeared in a span of 48 million years-all over the world
Burgess Shale Fauna (520-515 MYA), British Columbia
Explosion of body plans, tissue types, developmental patterns–Bilateral symmetry, segmentation, heads, appendages