Question

Which informal ecological group of protists includes photoautotrophs? a. protozoa b. algae c. fungus-like protists d. ciliates e. All of the above groups include photoautotrophs.

Short answer

The correct answer is: b. algae.

Step-by-step solution

Understanding the question

The question is asking about the group of protists that includes photoautotrophs. Photoautotrophs are organisms that can create energy from sunlight through photosynthesis and utilize this energy to convert carbon dioxide into organic material for growth (carbohydrates).

Analysing the options

Now, let's analyse the groups of protists present in the options. Protists are divided primarily on the basis of their nutritional mode. For example, protozoa are heterotrophs, ciliates are a type of protozoa that are also heterotrophs. Fungus-like protists also primarily obtain their nutrients through absorption. Therefore, these cannot include photoautotrophs, as they do not perform photosynthesis.

Identifying the correct group

On the other hand, Algae are protists that are photoautotrophs, as they perform photosynthesis to produce their food. Therefore, the correct answer is Algae which corresponds to option b.

Key concepts

Ecological Groups of Protists

Protists are incredibly diverse organisms that can be found in a variety of ecological niches. This diversity is reflected in the way protists can be categorized into different ecological groups, based on their nutritional requirements and lifestyle. The main ecological groups include protozoa, algae, fungus-like protists, and ciliates.

Protozoa are typically heterotrophic and often act as predators or parasites in their ecosystems. Algae, contrasting with protozoa, are primarily photoautotrophs, meaning they utilize sunlight to create their food through photosynthesis - just as plants do. Fungus-like protists, such as slime molds, resemble fungi in their mode of nutrition, which includes absorbing nutrients from their environment. Lastly, ciliates, a subset of protozoa, are characterized by the presence of cilia and are also heterotrophic, feeding on other microorganisms. Understanding these groups is crucial for studying protist biology and ecology.

Photosynthesis in Protists

Photosynthesis is a process that is not exclusive to plants; several protists also perform this life-sustaining reaction. Algae, for instance, represent a large group of photosynthetic protists. They contain chloroplasts, the cellular organelles that harness sunlight, turning it into chemical energy through the process of photosynthesis. This energy is later used to convert carbon dioxide from the atmosphere into organic compounds, primarily sugars, which serve as food for the algae and for other organisms in the ecosystem.

Chlorophyll and other pigments absorb light of various wavelengths, giving algae their distinctive green, brown, or red hues. These colors are indicative of the different types of algae, such as green algae, brown algae, and red algae, each utilizing unique pigment compositions to optimize energy absorption for photosynthesis.

Protist Nutritional Modes

The nutritional modes of protists are diverse, aligning with their ecological diversity. Broadly, protists can be categorized as photoautotrophs, heterotrophs, or mixotrophs. Photoautotrophs, like algae, produce their own food through photosynthesis. Heterotrophs, which include groups like protozoa and ciliates, obtain their nutrients by consuming organic materials - feeding on other organisms or decaying matter. Mixotrophs are versatile; they combine photosynthesis and heterotrophic nutrition, depending on environmental conditions.

This means a mixotrophic protist might use photosynthesis when light is abundant, and switch to feeding on other organisms when it is not. This adaptability reveals how protists have evolved various nutritional strategies to thrive across different habitats and play numerous roles in their ecosystems, from primary producers to decomposers.