Animal Body Plans

Adapted fromhttp://userwww.sfsu.edu/~biol240/la

bs/lab_16animalbodyplan/pages/bodyplan.html

Metazoans

• “Animals”–Multi-cellular–Develop from embryos–Divided into two groups based on

the presence of a backbone

Metazoans

Body Plans

• This can also be described as way an animal is “built” or the architecture of a species

• There are some basics features of a body plan that can be used to compare animals

• The various body plans we will cover have been shaped through evolution and constraints on the animals

Cambrian Explosion

• Most major animal groups around today originated in the precambrian and cambrian era

• Explosion of diversity in a relatively short period of time

• Some major evolutionary branches occurred around symmetry and multicellularity

Embryology

– Protostomes-mouth forms first then the anus during embryological development

• Most invertebrate groups

– Deuterostomes- anus forms first then the mouth• Can split up cells at 4 cell stage and each will continue

to develop into a complete viable organism• Echinoderms and chordates

www.mhhe.com

Symmetry• Def-pattern of arrangement of body parts• Asymmetry- no pattern of symmetry around

an axis…– No way to divide the org into similar looking

halves• Radial-more than one line of bisection• Bilateral- one line of bisection ie a distinct

right and left side – Also typically have dorsal and ventral surface,

anterior and posterior surface

Body Cavity

• Also called a coelem• Fluid filled cavity found between body wall

and digestive tract• Many different types and ways that a body

cavity develops• Acts as a hydrostatic skeleton in some less

advanced animals

Endoderm

Mesoderm

Ectoderm

Gut

Pseudocoel

Coelem

Segmentation• Repeated grouping of parts or compartments

– Aids in movement and evolution of appendages– Groups of segments and their appendages have

become specialized for a variety of “jobs” among regions ie a division of labor

Cephalization

• Def-Having a head– Sensory organs, centralized nervous system and

feeding parts are all usually concentrated here– Are there advantages to this arrangement?– Is there a particular kind of symmetry associated

with this?

Cephalization Advantage-• Anterior end of a travelling animal will

encounter stimuli-food, danger etc… first• Adaptation for burrowing, crawling, swimming• Radial animals tend to be sessile or

planktonic- can meet environmental symmetry from all sides

• Active animals moving in a distinct direction “meet” the environment from one end and bilateral symmetry fits that lifestyle

WORD BANK

• Symmetry• Multicellularity• Pseudocoelem• Protostome deuterostome• Body cavities and blood vascular system• Tissues• Coelem

Hydrostatic skeleton- skeleton composed of fluid and under pressure in an enclosed body compartment

Main skeleton of cnidaria and some worms

Gastroderm- layer of tissue producing digestive enzymes