Atolls and Animal Phyla: Porifera & Cnidaria

Which of the following statements about sponges is NOT true?

What is the primary function of the flagella in sponges?

Which type of sponge is characterized by having silica spicules for support?

What is the name of the elastic fibers found in demosponges?

Which of the following is NOT a characteristic of cnidarians?

What are the two main body forms found in cnidarians?

Which of the following is an example of a colonial cnidarian?

What distinguishes corals that build reefs from those that do not?

Which type of coral builds reefs?

What is the primary component of a stony coral's skeleton?

Which of the following is an example of a soft coral?

What is the primary characteristic that differentiates hydrocorals from true corals?

What is the function of the gas-filled float in the Siphonophora (Man of War)?

Atolls

Atolls are ring-shaped coral islands
Feature a lagoon in the center
Formed from coral reefs growing up from a submerged volcano
Have a reef flat, back reef, and reef front/fore reef
Parts of an atoll include a lagoon, back reef, reef flat, reef front, and shoreline

Animal Phyla: Porifera & Cnidaria

Porifera (Sponges):
- Simplest invertebrates (lack a backbone)
- Mostly marine; some freshwater
- Bodies have pores, hence the name "Porifera"
- Organized at a cellular level, without tissues or organs
- Pump large volumes of water through pores (up to 20,000 times their volume) to feed on bacteria and plankton
- Digestion occurs in amebocytes
- Sponges serve as habitat for many marine organisms
- Reproduction can be sexual or asexual
  - Asexual: external buds, internal gemmules
  - Sexual: broadcast gametes into the water; meroplanktonic larvae settle into sessile adults
- Three types:
  - Calcareous – with supporting spicules
  - Glass sponges – silica spicules, found in great depth
  - Demosponges – elastic fibers (spongin); used as commercial sponges
Cnidaria (Jellyfish, Anemones, and Corals):
- Two tissue layers (epidermis, gastrodermis)
- Nerve net and stinging capsules (nematocysts)
- Radial symmetry with two body types: polyp (attached) and medusa (free-floating)
- Corals can live as a free-floating polyp or build colonies into reefs (not all build reefs)
- Coral types:
  - Stony – hermatypic reef builders; calcium carbonate body
  - Soft – tentacles; do not build reefs; keratin bodies
  - Hydrocoral – resemble anemones; powerful neumatocysts; cause skin irritation (fire coral)

Animal Kingdom Numerical Distribution

173,000 Porifera
43,000 Cnidaria
4,500 Vertebrates (4%)
774,000 mammals (>1%)
79% Insects
17% Invertebrates

Explore the fascinating world of atolls and learn about their structure and formation. Dive into the characteristics of Porifera and Cnidaria, the simplest invertebrates that contribute to marine ecosystems. This quiz covers their anatomy, reproduction, and ecological significance.