Animal Diversity

• multicellular
• heterotrophic
• eukaryotic
• tissues developed from embryonic layers

cleavage- a series of mitotic cell divisions

blastula, taking the form of a hollow ball

process of gastrulation, where the embryonic tissues that will develop into adult body parts are produced.

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

Sets of morphological and developmental traits

• Two-sided symmetry
• 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

• 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

• 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

body cavities

• –Spiral Cleavage
• –Deterministic Cleavage
• –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.

• –Radial Cleavage
• –Indeterminate Cleavage
• •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

• –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
• –Ediacaran Biota
•  565 to 550 million years ago

• 542-251 MYA
• –Cambrian Explosion about 530 MYA
• –First fossils of arthropods, chordates and echinoderms

• 251 –65.5 MYA
• –DINOSAURS (and other animals)
• coral reefs formed

• cenozoic era
• 65.5 MYA to present

• 495-543 MYA
• 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

basal- most basic

true tissues

• animals having bilateral symmetry 
• most animal phyla are this

• chordates and some other phyla
• "second mouth organism"