Question

Describe the similarities and differences between the lichen and coral symbioses. (Sections 22.1, 22.14)

Short answer

Both involve mutualistic relationships for nutrition and support; lichens are fungus-algae/cyanobacterium symbioses, while corals involve animals and zooxanthellae and are marine.

Step-by-step solution

- Define Symbiosis

Understand that symbiosis is a close and often long-term interaction between two different biological species.

- Define Lichen Symbiosis

Recognize that lichens are formed from a symbiotic relationship between a fungus and a photosynthetic partner, usually an alga or cyanobacterium. The fungus provides structure and protection, while the photosynthetic partner produces food through photosynthesis.

- Define Coral Symbiosis

Corals are formed from a symbiotic relationship between coral polyps and dinoflagellates called zooxanthellae. The coral polyps provide a protected environment and compounds needed for photosynthesis, while the zooxanthellae supply oxygen and organic products of photosynthesis that the corals can use for nourishment.

- Similarities

Both lichen and coral symbioses involve a mutualistic relationship where both partners benefit: lichens gain food from photosynthesis and structural support from fungi, while corals provide a habitat for zooxanthellae and in return gain nutrition.

- Differences

Lichen symbiosis occurs between a fungus and a photosynthetic partner (alga or cyanobacterium), while coral symbiosis involves an animal (coral polyp) and a plant-like protist (zooxanthellae). Lichens can survive in a wide range of environments, including extreme conditions, whereas corals are mostly found in marine environments.

Key concepts

Lichen Symbiosis

Lichens are fascinating organisms that result from a symbiotic relationship between a fungus and a photosynthetic partner, such as algae or cyanobacteria. The fungus provides a protective structure and supplies moisture, while the photosynthetic partner creates food via photosynthesis. This combination allows lichens to thrive in diverse environments, including extreme ones like deserts and arctic tundras. The resilience of lichens is one of their most remarkable traits.

Coral Symbiosis

Coral symbiosis is integral to the health of coral reefs. Corals consist of tiny animals called coral polyps that form a mutualistic relationship with dinoflagellates known as zooxanthellae. Coral polyps offer a safe habitat and the necessary compounds for photosynthesis to the zooxanthellae. In return, zooxanthellae produce oxygen and organic molecules that nourish the coral. This symbiosis is vital for the formation and maintenance of coral reefs in tropical marine environments.

Mutualistic Relationships

A mutualistic relationship is a type of symbiosis where both species benefit from the interaction. In the case of lichens, the fungus and its photosynthetic partner both gain from each other's presence, contributing to their survival and growth. Similarly, coral polyps and zooxanthellae benefit mutually; the coral gains nutrients and oxygen, while the zooxanthellae receive protection and compounds for photosynthesis. Such relationships enhance the thriving of these organisms in their respective habitats.

Fungus and Photosynthetic Partner

In lichen symbiosis, the partners bring different strengths to the relationship. The fungus creates a sheltered structure that can absorb moisture and provide a stable environment. Meanwhile, the photosynthetic partner, whether it's an alga or cyanobacterium, produces food through photosynthesis. This cooperation ensures the lichen has a continuous supply of energy and protection against environmental stress. This type of mutualism demonstrates how different organisms can work together for survival.

Coral Polyps and Zooxanthellae

Coral reefs owe much of their existence to the symbiosis between coral polyps and zooxanthellae. The coral polyps, with their stony exoskeletons, provide a base and protection for the zooxanthellae. These microscopic algae perform photosynthesis, supplying the coral with essential nutrients and oxygen. This partnership enables coral reefs to flourish in nutrient-poor tropical waters. Understanding this relationship is crucial for efforts to protect and conserve coral reef ecosystems.