Chapter 33 Invertebrates

Question 1

What does the phylogenetic tree of invertebrates look like?

Answer 1

Porifera, Cnidaria, Lophotrochozoa, Ecdysozoa, and Deuterostomia

Question 1

Lophophores

Answer 1

Some lophotrochozoans develop a structure called a lophophore, a crown of ciliated tentacles that functions in feeding

Question 2

Trochophore larva

Answer 2

Distinctive larval stage in some lophotrochozoans, including some annelids and mollusks.

Question 3

Which invertebrate group was grouped together using molecular phylogenetics?

Answer 3

Lophotrochozoans

Question 4

Describe Sponges

Answer 4

• lack tissues and are the sister group to animals
• have choanocytes: collar/flagellated cells that ingest bacteria and food particles
• are suspension feeders
• made of spongin
• are hermaphrodites

Question 5

Describe Cnidarians

Answer 5

• includes hydras, sea anemones, jellies, and coral
• have nematocytes (stinging structures) in cnidocytes
• radial symmetry with no anus; instead have a gastrovascular cavity
• alternate medusa (sexual) and polyp (asexual) phases
• are diploblastic

Question 6

Describe Platyhelminthes

Answer 6

• includes flatworms
• usually free-living and parasitic
• no body cavity or digestive tract but has a gastrovascular cavity for circulation
• most are hermaphrodites and asexually reproduce

Question 7

Describe Annelida

Answer 7

• includes segmented worms
• have celomic spaces divided by septa
• have a through-gut (mouth and anus)
• have a circulatory system
• most are hermaphrodites or gonochoristic

Question 8

Describe Mollusca

Answer 8

• includes clams, snails, and squids
• have a foot for burrowing/crawling
• are gonochoristic
• have hard exoskeleton secreted by dorsal epidermis/mantle
• three main body parts: mantle, foot, and visceral mass

Question 9

Describe Nematoda

Answer 9

• includes roundworms
• usually parasites or pests
• have no circulatory system
• undergo ecdysis

Question 10

Describe Arthropoda

Answer 10

• includes spiders, centipedes, crustaceans, and insects
• have segmented bodies, jointed appendages, and an exoskeleton made of protein and chitin
• undergo ecdysis
• generally gonochoristic
• have specialized structures for gas exchange

Question 11

What are the medusa and polyp stages in Cnidarians?

Answer 11

Polyps are the sessile variants of the cnidarian body plan. Medusa is the floating, mouth-down form of the cnidarian body plan. If the specimen goes through both a medusa and polyp stage, medusa is sexual while polyp is asexual.

Question 12

Lophotrochozoans

Answer 12

• includes Platyhelminthes (flatworms), Mollusks, and Annelids

Question 13

Ecdysozoans

Answer 13

• includes Nematoda and Arthropoda

Question 14

Deuterostomes

Answer 14

• includes Echinoderms and Chordates