BIO Exam 3 (4) Symmetry, Orientation & Protostomes

What are the three main types of animal symmetry?

Asymmetrical, radial, and bilateral.

What does asymmetrical mean?

No definite plane divides the body into matching halves.

Which animal group is commonly asymmetrical?

Many sponges (Porifera).

What does radial symmetry mean?

Body parts are arranged around a central axis.

What body directions describe radial symmetry?

Oral (mouth side) and aboral (opposite the mouth); no distinct front or back.

Which animal group is commonly radially symmetrical?

Cnidarians, such as jellyfish.

What does bilateral symmetry mean?

One plane divides the body into left and right halves.

What body directions are used for bilateral animals?

Anterior, posterior, dorsal, ventral, left, and right.

What does anterior mean?

Front or head end.

What does posterior mean?

Back or tail end.

What does dorsal mean?

Top or back side.

What does ventral mean?

Bottom or belly side.

From whose perspective are an animal's left and right defined?

The animal's own perspective.

What is the blastopore?

The opening formed during gastrulation.

In protostomes, what does the blastopore develop into?

The mouth.

In deuterostomes, what does the blastopore develop into?

The anus.

What cleavage pattern is typical of protostomes?

Usually spiral and determinate cleavage.

What cleavage pattern is typical of deuterostomes?

Usually radial and indeterminate cleavage.

How does the coelom usually form in protostomes?

By splitting of mesoderm.

How does the coelom usually form in deuterostomes?

From outpocketings of the archenteron.

What is an acoelomate?

A triploblastic animal with no body cavity; example: flatworms.

What is a pseudocoelomate?

A triploblastic animal with a false body cavity; example: nematodes.

What is a coelomate?

A triploblastic animal with a true coelom; example: humans.

Which body-cavity categories apply to triploblastic animals?

Acoelomate, pseudocoelomate, and coelomate.

An animal has a mouth-side and an opposite side, but no front or back. What symmetry is this?

Radial symmetry.

An animal has a distinct head end, tail end, back, and belly. What symmetry is expected?

Bilateral symmetry.

A developing embryo's blastopore becomes its mouth. What developmental group is it?

Protostome.

An embryo has radial, indeterminate cleavage and the blastopore becomes the anus. What group is it?

Deuterostome.

What three features distinguish protostome and deuterostome development?

Blastopore fate, cleavage pattern, and coelom formation.