Chapter 28: Invertebrates

Question 1

What are the structural components of sponges (Porifera)?

Answer 1

Ostia: Small pores for water intake.
Spongocoel: Central cavity lined with choanocytes.
Osculum: Large opening for water expulsion.
Choanocytes: Collar cells with flagella to filter food.
Amoebocytes: Mobile cells distributing nutrients and forming spicules (silica/calcium carbonate).

Question 2

How do sponges reproduce?

Answer 2

Asexual: Budding, fragmentation, or gemmules (survival pods).
Sexual: Hermaphroditic; sperm released into water → eggs fertilized internally → larvae (parenchymula) released.

Question 3

Describe the two body forms in Cnidaria.

Answer 3

Polyp: Cylindrical, sessile (e.g., corals, Hydra).
Medusa: Umbrella-shaped, free-swimming (e.g., jellyfish).
Alternation of generations: Some species switch between forms (e.g., Obelia).

Question 4

What is the function of the gastrovascular cavity in Cnidaria?

Answer 4

Digestion, gas exchange, and waste expulsion.
Single opening (mouth/anus) surrounded by tentacles with cnidocytes (stinging cells).

Question 5

Name the four classes of Cnidaria.

Answer 5

Hydrozoa (e.g., Hydra, Portuguese man-o-war).
Scyphozoa (true jellyfish, e.g., Aurelia).
Cubozoa (box jellyfish, e.g., Chironex).
Anthozoa (corals, sea anemones).

Question 6

Describe key traits of Platyhelminthes.

Answer 6

Acoelomate: No body cavity.
Classes:
Turbellaria (free-living, e.g., planarians).
Trematoda (flukes, e.g., Schistosoma).
Cestoda (tapeworms, e.g., Taenia).

Question 7

How do tapeworms absorb nutrients?

Answer 7

Scolex: Head with hooks/suckers for attachment.
Proglottids: Segments containing reproductive organs.
No digestive system; nutrients absorbed through tegument.

Question 8

What distinguishes Rotifers?

Answer 8

Corona: Ciliated crown for feeding.
Parthenogenesis: Females produce diploid eggs without males.
Mastax: Jaw-like grinding structure.

Question 9

Describe Nemertea.

Answer 9

Proboscis: Retractable structure in rhynchocoel for capturing prey.
Complete digestive tract (mouth → anus).
Marine; some species exceed 30 meters.

Question 10

Name the three major classes of Mollusca.

Answer 10

Gastropoda (snails, slugs): Radula for scraping food.
Bivalvia (clams, oysters): Filter feeders with two shells.
Cephalopoda (squid, octopus): Advanced brain, closed circulatory system.

Question 11

How do cephalopods evade predators?

Answer 11

Chromatophores: Pigment cells for camouflage.
Ink sacs: Release melanin to confuse predators.
Jet propulsion via siphon.

Question 12

Define Annelida (segmented worms).

Answer 12

Metamerism: Body divided into repeated segments.
Setae: Bristles for movement (e.g., earthworms).
Clitellum: Secretes cocoon for reproduction.

Question 13

Contrast Oligochaeta and Hirudinea.

Answer 13

Oligochaeta: Few setae; detritivores (e.g., earthworms).
Hirudinea: No setae; parasites with anticoagulants (e.g., leeches).

Question 14

What is ecdysis?

Answer 14

Molting of the cuticle/exoskeleton to allow growth.
Occurs in Nematoda (roundworms) and Arthropoda.

Question 15

Describe Nematoda.

Answer 15

Pseudocoelomate: Body cavity partially lined by mesoderm.
Longitudinal muscles: Cause thrashing movement.
Examples: Caenorhabditis elegans (model organism), Trichinella (parasite).

Question 16

Why are tardigrades extremotolerant?

Answer 16

Survive extreme conditions via cryptobiosis (dehydrate into a tun state).
Tolerate radiation, vacuum, and temperatures from -272°C to 150°C.

Question 17

Key traits of Arthropoda.

Answer 17

Exoskeleton: Made of chitin and proteins.
Jointed appendages: Legs, antennae, mouthparts.
Tagmata: Fused segments (e.g., head-thorax-abdomen).

Question 18

Compare Chelicerata and Mandibulata.

Answer 18

Chelicerata: No antennae; use chelicerae (fangs) (e.g., spiders, scorpions).
Mandibulata: Jaw-like mandibles; have antennae (e.g., insects, crustaceans).

Question 19

What defines deuterostomes?

Answer 19

Radial cleavage: Embryonic cells divide parallel/perpendicular to axis.
Blastopore becomes anus (mouth forms secondarily).
Includes Echinodermata and Chordata.

Question 20

Unique traits of Echinoderms.

Answer 20

Water vascular system: Hydraulic tube feet for movement.
Pentaradial symmetry (adults); endoskeleton of calcareous ossicles.
Examples: Starfish, sea urchins.

Question 21

Open vs. closed circulatory systems.

Answer 21

Open: Hemolymph flows freely in hemocoel (e.g., arthropods).
Closed: Blood confined to vessels (e.g., annelids, cephalopods).

Question 22

Direct vs. indirect development.

Answer 22

Direct: Offspring resemble adults (e.g., earthworms).
Indirect: Larval stage (e.g., butterfly caterpillars).