Invertebrates and Coral Reefs

Introduction to Invertebrates

• Invertebrates are animals that lack a backbone.
• Make up 96% of all described species of animals.
• Comprise a heterogeneous assemblage of over 35 phyla.
• No single positive character defines all invertebrates.
• Essential for ecosystem functioning, serving as a base for most food webs.

Importance of Studying Invertebrates

• Direct and indirect causes of diseases in humans, animals, and plants.
• Significant contributions to scientific understanding of:
  • Gene expression
  • Cell division
  • Embryonic development
  • Hemoglobin function
  • Animal behavior, ecology, and evolution.
• Source of unique chemicals and commercial products.
• Indicators of environmental health.

Taxonomy of Invertebrates

Major Groups

• Metazoa: All animals
• Eumetazoa: Animals with specialized tissues
• Bilateria: Animals with bilateral symmetry (triploblastic).
  • Protostomia: Groups include Ecdysozoa (e.g., arthropods, nematodes) and Lophotrochozoa (e.g., annelids, mollusks).
  • Deuterostomia: Chordates and echinoderms.
• Radiata: Animals exhibiting radial symmetry like Cnidaria.

Phylum Porifera (Sponges)

Characteristics

• Simplest metazoans, with cellular organization.
• Body plan is sac-like with numerous pores (ostia).
• Cells include:
  • Choanocytes: Generate water currents for feeding.
  • Amoebocytes: Distribute nutrients and aid in reproduction.
• Sessile filter feeders, reproducing both asexually (through fragmentation or budding) and sexually (produce both gametes).

Types of Sponges

• Small, tube-shaped sponges
• Flagellated canals
• Most complex: flagellated chambers and include bath sponges, glass sponges, and barrel sponges.

Phylum Cnidaria

Overview

• Body forms:
  • Medusa: Free-floating form, dominant in Scyphozoa.
  • Polyp: Attached form, dominant in Hydrozoa and Anthozoa.
• Tissue-level organization; diploblastic with radial symmetry.
• Gastrovascular cavity serves for digestion and nutrient absorption.

Specialized Structures

• Cnidocytes: Stinging cells around the mouth and tentacles, equipped with nematocysts.
• Two types of digestive systems:
  • Incomplete (single opening)
  • Complete (separate mouth and anus).

Diversity of Cnidarians

• Class Scyphozoa: Jellyfish, dominant medusa form.
• Class Hydrozoa: Primarily polyp stage; includes Portuguese man o' war.
• Class Anthozoa: Flower animals like sea anemones and corals; lack medusa stage.
• Class Cubozoa: Box jellies, some of which are highly venomous.

Coral Corals and Reefs

Structure and Function

• Corals possess symbiotic zooxanthellae which perform photosynthesis.
• Skeletons made of calcium carbonate, forming reefs that support diverse marine life.
• Vital for 25% of all marine species.

Coral Metabolism

• Requires warm, clear, tropical waters.
• Processes involve diffusion of gases and nutrients necessary for metabolism and growth.

Threats to Coral Reefs

• Major threats include climate change and ocean acidification due to increased levels of greenhouse gases, leading to severe alterations in ocean chemistry.
• Consequences include coral bleaching, loss of species diversity, and structural degradation of reef ecosystems.
• Projected loss of significant coral populations within decades if current trends continue.

Climate Change Impacts

• Increased temperatures leading to coral bleaching.
• Ocean acidification affecting calcium carbonate availability for coral growth.
• Changes in storm patterns and sedimentation affecting coral health.
• Algal blooms resulting in competition for light and resources.

Conservation Strategies

• Personal actions to reduce carbon footprint (e.g., driving less, using less water).
• Support sustainable seafood and avoid chemicals harmful to the marine environment.
• Engage in volunteer work to aid in clean-ups and conservation efforts.