32: Animal Origins and the Evolution of Body Plans

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Which is more speciose, plants or animals?

Animals

Traits that distinguish the animals (4)

1. Multicellular
2. Heterotrophs
3. Internal digestion
4. Motile

1. (T/F) Sponges have no distinct tissue types
2. Animals other than sponges are called ______________
3. Groups under eumetazoans (2)

1. True
2. Eumetazoans
3. Diploblastic and triploblastic (bilaterians)

Characteristics of eumetazoans (4)

1. Symmetry
2. Gut
3. NS
4. Tissues organized into organs

Zygote development sequence

1. Zygote
2. Cleavage
3. Eight cell stage
4. Cleavage
5. Blastula
6. Gastrulation
7. Gastrula

1. Diploblastic animals have what germ layers?
2. Triploblastic anmials have what germ layers?

1. Ecto and endo
2. Ecto, meso, and endo

(T/F) Tissues are collections of specialized cells isolated from other tissues by membranous layers

True

Most triploblastic animals possess a _____ ______ (coelom)

Body cavity (coelom)

1. Coelom is derived from which germ layer?
2. Term for animals with a true coelom

1. Mesoderm (which is why they are triploblastic)
2. Coelomates

For the following coelomates, name the germ layer the following structures derive from:
1. Digestive tract
2. Body covering
3. Tissue layer lining coelom and suspending internal organs

1. Endoderm
2. Ectoderm
3. Mesoderm

1. What tissue layer/s surround the cavity in a pseudocoelomate?
2. What tissue layer/s surround the cavity in a coelomate?

1. Mesoderm (superficial) and endoderm (deep)
2. Mesoderm

Triploblastic animals that lack a body cavity (term)

Acoelomates

What animal groups are protostomes?

1. Arrow worms
2. Lophotrochozonas
3. Ecdysozoans

1. Protostome development, cleavage is __________(spiral/radial) and _________(determinate/indeterminate)
2. Deuterostome development, cleavage is ________(radial/spiral) and _______(indeterminate/determinate)
3. What makes it possible for identical twins and embryonic stem cells (term)?

1. Spiral, determininate
2. Radial, indeterminate
3. Indeterminate cleavage

What animal groups are deuterostomes? (3)

1. Echinoderms
2. Himichordates
3. Chordates

Protostomes and deuterostomes are under which group?

Bilaterians (triploblastic)

Pouch formed by gastrulation (term)

Archeteron

Protostome or deuterostome development?
1. The splitting of solid masses of mesoderm forms the coelom, closer to blastophore
2. The mesoderm buds from the wall of the archeteron to form the coelom, opposite the blastophore

1. Protostome development
2. Deuterostome development

Forms during gastrulation and connects the archenteron to the exterior of the gastrula (term)

Blastophore

Protostome or deuterostome development?
1. Blastopore becomes the anus
2. Blastopore becomes the mouth

1. Deuterostome development
2. Protostome development

(T/F) Choanoflagellates are the closest living relative of animals

True

How do sponges eat? What is the spongocoel? Choanocytes (what type of cell)? Do they use energy?

Sponges are suspension feeders. Water is drawn through pores into a cavity called the spongocoel, and out through an opening. Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food. They expend energy to eat.

Small needlelike or sharp-pointed structures of calcite or silica that make up the skeleton of a sponge (term)

Spicule

Radial vs bilateral symmetry

Bilaterally symmetric animals have right/left side, anterior/posterior ends, and cephalization (development of heads)

Cnidarians are diploblastic/triploblastic and radial/bilateral?

Diploblastic and radial

The digestive compartment of a cnidarian (term)

Gastrovascular cavity

Two variations on body plan of cnidarian

1. Sessile polyp
2. Motile medusa
*most hydrozoans alternate between polyp and medusa forms

How do cnidarians eat? What are cnidocytes? What are nematocysts?

Cnidarians are carnivores that use tentacles to capture prey. The tentacles are arms with cnidocytes, unique cells that function in defense and capture prey. Nematocysts are specialized organelles within cnidocytes that eject a stinging thread.

Four major classes of phylum cnidaria

1. Hydrozoa ex. colonial polyps
2. Scyphozoa ex. jellies
3. Cubozoa or box jellies ex. sea wasp
4. Anthozoa or corals ex. sea anemone

Type of coelom?
1. Flat worms
2. Roundworms

1. Acoelomate
2. Pseudocoelomates

Protostomes vs deuterostomes. Differences. Blastophore development? Notochord/exoskeleton?

In protostomes the blastophore develops into a mouth and in deuterostomes the blastophore develops into an anus. Protostomes also have exoskeleton molting and deuterostomes have notochord.

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