Unit 3 Flashcards
Radial symmetry
Body is shaped like a pie or barrel and can be divided into mirror imaged halves by any plane through its central axis
Bilateral symmetry
Central longitudinal plane divides the body into two equal but opposite halves
Cephalization
Evolutionary trend towards the concentration of sensory equipment at the anterior end of the body
Blastula
Hollow ball of cells that marks the end of the cleavage stage during early embryonic development in animals
Ectoderm
The outermost of the three primary germ layers in animal embryos. Gives rise to skin, nerves
Endoderm
Innermost of the three primary germ layers. Gives rise to gut lining
Mesoderm
Middle primary germ layer in a triploblastic animal embryo. Gives rise to muscle, skeleton, circulatory system. Develops into notochord
Gastrula
Embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, endoderm
Determinate cleavage
Embryonic development in protostomes that casts the fate of each embryonic cell very early
Cell types fixed early
Indeterminate cleavage
Early embryo cells can each form a complete organism
Epidermis
Outermost layer of cells in an animal
Suspension feeder
Aquatic animal such as sponge that feeds by sifting small organisms or food particles from water
Polyp
Sessile variant of the cnidarian body plan
Medusa
Floating, flattened, mouth-down version of cnidarian body plan
Gastrodermis
Stomach skin layer, lines gastrovascular cavity
Diploblastic
2 tissue layer (ectoderm &; endoderm, no mesoderm)
Cnidocytes
Stinging cells
Protonephridia
An excretory system, such as flame bulb system of flatworms, consisting of a network of tubules lacking internal openings
Simple organ for proper dilution
Septae
Segmented dividers
Ingestion
First stage of food processing in animals
Nephron
Tubular excretory unit of vertebrate kidney
Mantle
Surrounds visceral mass, secretes shell
One of three parts of mollusc
Visceral mass
Contains organs
Part of mollusc
Foot
For movement
Part of mollusc