Problem 13 - Biology Today and Tomorrow with Physiology

Question

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

Step-by-Step Solution

Answer

The correct answer is b. lichen.

Step 1: Understanding the Question

The question is asking for the definition or identification of a type of organism composed of two specific components: a fungus and a single-celled photosynthetic species. You need to identify which of the given options matches this description.

Step 2: Analyzing Each Option

Let's examine each option: - a. Mycorrhiza: This is a mutualistic relationship between fungi and plant roots, not mentioned as a single photosynthetic species. - b. Lichen: This is indeed a composite organism formed by the symbiotic relationship between a fungus and an algae or cyanobacteria, which is a photosynthetic organism. - c. Decomposer: This term refers to organisms that break down dead or decaying matter, not a composite organism with photosynthesis. - d. Ringworm: This is a fungal infection and not related to a photosynthetic organism.

Step 3: Choosing the Correct Answer

Based on the analysis of the options, option b (lichen) is the only choice that matches the definition of a composite organism composed of a fungus and a single-celled photosynthetic species.

Key Concepts

Symbiotic relationship

Lichens are fascinating examples of symbiotic relationships, where two different organisms live together in such a way that they benefit from each other's presence. In the case of lichens, the partnership typically includes a fungus and a photosynthetic partner such as algae or cyanobacteria. This close relationship is mutually beneficial, as each organism provides something essential for the other's survival.

The fungus acts as the structure that houses and protects the photosynthetic partner. It absorbs moisture and minerals from the environment, providing a suitable and stable habitat. In return, the photosynthetic partner conducts photosynthesis, a process where it converts sunlight into chemical energy. This energy is then shared with the fungus.

This relationship is a perfect example of mutualism, a type of symbiosis where both partners gain benefits that neither could achieve alone. This partnership allows lichens to inhabit environments where neither the fungus nor the photosynthetic partner could survive independently, such as rocky surfaces, tree bark, and even harsh arctic regions.

Fungus and algae

Fungi and algae are the two main components of lichen. They combine their unique abilities to create a resilient and flexible partnership. The fungal part is usually from the group Ascomycota and occasionally from Basidiomycota. This part forms the main body of the lichen, providing structural support and anchoring the organism to various surfaces.

The algal component can be from a variety of single-celled photosynthetic species. Sometimes, it’s algae, and other times, it’s a type of bacteria known as cyanobacteria. Both of these photosynthetic partners have the ability to produce their own food through the process of photosynthesis.

In lichens, the fungus plays a protective role, encasing the algae within its tissues, preventing it from drying out and ensuring that it gets the nutrients it needs from the surrounding environment. Meanwhile, the photosynthetic algae generate organic carbon per the needs of their fungal companion, making this partnership a truly complementary symbiosis.

Photosynthetic species

The photosynthetic species in lichens are either algae or cyanobacteria, both of which are capable of photosynthesis. Photosynthesis is a biochemical process by which these organisms convert light energy into chemical energy, stored as sugar, which can then be utilized for growth and energy.

Algae, when involved in lichen partnerships, are typically green algae. Cyanobacteria, often referred to as blue-green algae, can also act as the photosynthetic component. These microorganisms reside within the scaffold of the fungal tissue, where they bask in the sunlight.

By producing food through photosynthesis, these species offer essential nutrients not only to themselves but also to their fungal partners. Because of this, lichens have the ability to thrive in environments that would otherwise be inhospitable to both organisms independently, demonstrating the incredible adaptability of these symbiotic relationships.