Question

A ___ is a composite organism composed of a fungus and a single-celled photosynthetic species. a. mycorrhiza b. lichen c. decomposer d. ringworm

Short answer

The answer is b. lichen.

Step-by-step solution

Understand the Question

The problem asks us to identify a term that describes a composite organism made up of a fungus and a single-celled photosynthetic partner.

Identify Key Characteristics

Composite organisms mentioned involve two different species, one being a fungus and the other a photosynthetic organism (usually algae or cyanobacteria). This should be a symbiotic relationship.

Analyze the Options

Review each provided option: - **a. Mycorrhiza**: This is a symbiotic relationship between fungi and plant roots, not a composite organism with a photosynthetic single-celled species. - **b. Lichen**: This is indeed a symbiotic relationship termed a composite organism, typically involving a fungus and an algae or cyanobacteria. - **c. Decomposer**: This term refers to organisms that break down dead material, not a composite organism. - **d. Ringworm**: This is a type of fungal infection, not a composite organism.

Choose the Correct Answer

Based on the characteristics and analysis, the correct term for a composite organism composed of a fungus and a single-celled photosynthetic species is **lichen**.

Key concepts

Symbiotic relationships

In nature, a symbiotic relationship is a close and often long-term interaction between two different biological species. These relationships are crucial for the survival and success of many organisms and can take several forms:

• Mutualism: Both species benefit from the interaction. For instance, in a lichen, both the fungus and its photosynthetic partner benefit. The fungus provides a protected environment and nutrients like moisture, while the photosynthetic organism produces food through photosynthesis.
• Commensalism: One species benefits without affecting the other. An example outside the scope of lichens is certain barnacles attaching to whales, where the barnacles benefit from mobility while the whale is unaffected.
• Parasitism: One species benefits at the expense of the other. Unlike lichens, parasites harm their hosts, such as tapeworms in the intestines of mammals.

In the case of lichens, the relationship is mutualistic, illustrating how unique collaborations among species can lead to survival in even the harshest conditions. These partnerships enable lichens to inhabit areas where other organisms might struggle, such as rocky surfaces or arctic tundras.

Fungal biology

Fungi are fascinating organisms that play vital roles in ecosystems. They have distinct features that differentiate them from plants and animals. Among these important organisms are the fungi that form part of lichens. Let’s explore some key aspects of fungal biology:

• Structure: Fungi typically consist of elongated cells called hyphae, which form a network known as a mycelium. This structure helps them efficiently absorb nutrients.
• Reproduction: Fungi can reproduce both sexually and asexually. Sexual reproduction often involves spores that are dispersed by the wind, while asexual reproduction can involve simple division or the development of spores directly from the parent organism.
• Nutrient acquisition: Fungi absorb nutrients through their mycelium, often by breaking down and decomposing organic material. In lichens, however, they rely on the photosynthetic organism for nutrients derived from photosynthesis.

Fungi's adaptability and various roles make them key players in recycling nutrients, supporting ecosystems, and forming complex symbiotic relationships like those seen in lichens.

Photosynthetic organisms

Photosynthetic organisms, such as algae and cyanobacteria, play a crucial role in lichen formation. These organisms possess the remarkable ability to convert sunlight into food through photosynthesis. Here’s how they contribute to life on Earth and lichen symbiosis:

• Basic Process: Photosynthesis occurs in chloroplasts (or similar structures) where sunlight, carbon dioxide, and water are converted into glucose and oxygen. The equation for this process is: \[ 6CO_2 + 6H_2O + light ightarrow C_6H_{12}O_6 + 6O_2 \]
• Role in lichens: As part of a lichen, the photosynthetic organism produces the food necessary for both itself and its fungal partner. This provides the energy that fuels the lichen's metabolic processes.
• Environmental Impact: These organisms help in oxygen production and carbon dioxide reduction, playing a significant role in maintaining atmospheric balance.

By powering the lichen partnership with energy and contributing to essential ecological processes, photosynthetic organisms reveal the importance of symbiotic relationships in nature's complex web.