Ch.32 Animal origins

What are the main characteristics of animals?

They are multicellular, heterotrophic, and eukaryotic, with tissues that develop from embryonic layers.

How do animals obtain their food?

Animals are heterotrophs and must ingest their food.

Do animal cells have a cell wall?

No, instead, they are held together by proteins like collagen.

What tissues are unique to animals?

Nervous tissue and muscle tissue.

What happens after the formation of the blastula in most animals?

Gastrulation occurs, leading to the formation of embryonic tissue layers.

What are the three types of symmetry in animals?

1. Bilateral (like a beetle)

2. Radial (like a coral polyp)

3. None (like a sponge)

What are the characteristics of bilaterally symmetrical animals?

They have left and right sides that are mirror images, as well as dorsal (top) and ventral (bottom) sides, and anterior (front) and posterior (back) ends.

How many layers do diploblastic and triploblastic animals have?

• Diploblastic: Have two tissue layers.

• Triploblastic: Have three tissue layers.

What is a coelomate?

An animal with a true coelom, a fluid-filled body cavity completely lined by mesoderm tissue. Examples include annelids, mollusks, arthropods, and chordates.

What is a pseudocoelomate?

An animal with a pseudocoelom, a body cavity that is partially lined by mesoderm and endoderm. Example: Roundworms (Nematodes).

What is an acoelomate?

An animal without a body cavity between the digestive tract and outer body wall. Example: Flatworms (Platyhelminthes).

Why is the coelom important?

It protects internal organs, helps with circulation, and acts as a hydrostatic skeleton for movement in soft-bodied animals.

What is the cleavage pattern in protostomes?

Spiral and determinate cleavage, where cells divide in a twisted pattern and their fate is determined early.

What is the cleavage pattern in deuterostomes?

Radial and indeterminate cleavage, where cells divide in a straight pattern, and each cell can become a full organism.

How does coelom formation differ between protostomes and deuterostomes?

• Protostomes: Coelom forms from solid masses of mesoderm splitting (schizocoely).

• Deuterostomes: Coelom forms from folds of the archenteron (primitive gut) (enterocoely).

What is the fate of the blastopore in protostomes?

The blastopore becomes the mouth.

What is the fate of the blastopore in deuterostomes?

The blastopore becomes the anus.

Why is the distinction between protostomes and deuterostomes important?

It helps classify animal groups and understand their evolutionary differences. Humans and vertebrates are deuterostomes, while insects, worms, and mollusks are protostomes.

What is the difference in cleavage between protostomes and deuterostomes?

• Protostomes: Spiral and determinate.

• Deuterostomes: Radial and indeterminate.

How does coelom formation differ between protostomes and deuterostomes?

• Protostomes: Schizocoely (splitting of mesoderm).

• Deuterostomes: Enterocoely (folding of archenteron).

What happens to the blastopore in protostomes and deuterostomes?

• Protostomes: Blastopore becomes the mouth.

• Deuterostomes: Blastopore becomes the anus.

Give examples of protostomes.

Mollusks, annelids, arthropods.

Give examples of deuterostomes.

Echinoderms (sea stars) and chordates (humans).