Anthozoa Characteristics Quiz

General Characteristics of Anthozoa

• Mostly sessile organisms primarily existing as polyps.
• Lack alternation of generations and exhibit polymorphism.
• One oral opening for intake and expulsion of food and waste.

Tentacles and Movement

• Tentacles encircle the mouth, aiding in feeding and protection.
• Generally sessile; movement is minimal and only when necessary.
• Utilize a pedal disc to anchor themselves to surfaces.

Feeding and Digestion

• Tentacles with nematocytes sting and paralyze prey for ingestion.
• Food enters the gastrovascular cavity for digestion; undigested matter is expelled through the mouth.

Respiration

• Respiration occurs via diffusion as cnidarians lack lungs and a heart.

Protective Structures

• Tentacles house cnidocytes containing nematocytes, which release neurotoxins for defense and prey capture.

Reproductive Strategies

• Reproduction can be asexual or sexual.
• Sexual reproduction involves external fertilization, leading to planula larvae formation.
• Asexual methods include budding, longitudinal fission, pedal laceration, and fragmentation.

Skeleton and Coral Structures

• Sea anemones possess a hydrostatic skeleton maintained by osmotic pressure.
• Corals can be hard (secreting a skeletal cup) or soft (connecting tissue in colonies).

Coral Reefs

• Not all corals contribute to reef formation; most reef-building occurs with stony corals.
• Healthy coral reefs flourish in bright, clear water with salinity and temperature conditions around 70°F.

Symbiotic Relationships

• Reef-building corals and zooxanthellae engage in mutualism: zooxanthellae provide photosynthetic benefits, while corals offer habitat.
• This relationship supports coral health, coloration, and skeletal growth.

Habitat Requirements

• Coral reefs thrive in shallow waters (less than 300 feet deep) where light penetration is sufficient for photosynthesis.

History and Classification

• Historically misclassified as plants until the 19th century, corals are recognized as animals, hosting symbiotic zooxanthellae.
• Corals reproduce mostly at night and consist primarily of limestone structures made from calcium and carbon.

Importance of Coral Reefs

• Serve as vital ecosystems for marine life, housing approximately 25% of marine species while covering only 7% of the ocean.
• Provide ecological benefits by safeguarding shorelines and materials for valuable resources (e.g., medicines).

Types of Corals and Reefs

• Three main types of coral reefs: fringing reefs, barrier reefs, and atolls.
• Reefs develop very slowly—approximately 1-16 feet every thousand years.

Threats to Coral Reefs

• Coral bleaching leads to "white corals," indicating dead corals due to stressors that kill zooxanthellae.
• Physical damage from boat anchoring and other human activities jeopardizes reef health.

Larval Mobility and Energy Sources

• Planula larvae swim using cilia for propulsion.
• Corals obtain 90% of their energy from symbiotic zooxanthellae and 10% from ingested food/water.