Protists: Diversity, Classification, and Ecological Roles in Biology

Why are protists difficult to classify?

Protists do not fit into a kingdom and constitute a polyphyletic group.

What are the four supergroups of protists?

Excavata, SAR, Archaeplastida, and Unikonta.

What is a key characteristic of the supergroup Excavata?

Excavata is characterized by its cytoskeleton and often has an excavated feeding groove.

What are the three major clades of the SAR supergroup?

Stramenopiles, Alveolates, and Rhizarians.

What types of nutritional modes do protists exhibit?

Photoautotrophs, heterotrophs, and mixotrophs.

How do protists reproduce?

Some reproduce asexually through mitosis, while others reproduce sexually via meiosis and fertilization.

What is the significance of diatoms in the ecosystem?

Diatoms are a major component of phytoplankton and have various human uses, including water filtration and abrasives.

What are dinoflagellates and their ecological impact?

Dinoflagellates are abundant in phytoplankton, can be bioluminescent, and cause toxic 'red tides' that can kill fish and affect human health.

What is the life cycle of Plasmodium, the malaria-causing protist?

Plasmodium requires both mosquitoes and humans to complete its life cycle, with mosquitoes acting as the vector.

What are some examples of organisms in the Stramenopiles clade?

Diatoms, golden algae, and brown algae.

What distinguishes red algae from other protists?

Red algae are part of the Archaeplastida supergroup and are known for their unique pigments and multicellularity.

What is the role of protists in ecological communities?

Protists play critical roles in nutrient cycling and as primary producers in aquatic ecosystems.

What is the difference between a polyphyletic and a paraphyletic group?

A polyphyletic group includes organisms from different evolutionary lineages, while a paraphyletic group includes a common ancestor and some, but not all, of its descendants.

What is a common feature of Euglenozoans?

Euglenozoans often have unique flagella and modified mitochondria.

What are the characteristics of amoebozoans?

Amoebozoans include slime molds and tubulinids, characterized by their amoeboid movement.

What are the ecological roles of ciliates?

Ciliates, such as Paramecium, are freshwater predators that use cilia for movement and feeding.

What is the significance of mixotrophs among protists?

Mixotrophs can switch between autotrophic and heterotrophic modes based on environmental conditions.

What is the primary mode of nutrition for heterotrophic protists?

Heterotrophic protists absorb organic molecules or ingest larger food particles.

What is the importance of genetic data in classifying protists?

Genetic data has revealed that protists are not a monophyletic group, leading to significant changes in their classification.

What are some human uses of diatomaceous earth?

Diatomaceous earth is used in water filters, pest control, and as an abrasive in products like toothpaste.

What is the lifecycle stage of malaria that infects red blood cells?

Merozoite

What are the two main types of gametes involved in the malaria lifecycle?

Male and female gametes (haploid)

What is the supergroup that includes red algae, green algae, and plants?

Archaeplastida

What pigment gives red algae their color?

Phycoerythrin

What are foraminiferans, or forams, known for?

Their porous shells called tests, which are useful for paleontological studies.

What role do photosynthetic protists play in aquatic ecosystems?

They are primary producers, converting CO2 to organic compounds and producing at least 50% of atmospheric oxygen.

What is the ecological significance of dinoflagellates?

They nourish coral polyps that build reefs, forming mutualistic relationships.

What is the main characteristic of the supergroup Unikonta?

It includes animals, fungi, and some protists.

What is the significance of the genus Entamoeba?

Entamoeba histolytica causes amoebic dysentery, a leading cause of human death due to eukaryotic parasites.

What are the two main groups of green algae?

Charophytes and chlorophytes.

What are the effects of climate change on photosynthetic protists?

The biomass of photosynthetic protists has declined as sea surface temperatures have increased.

What is a key morphological characteristic of the group Euglenozoans?

They have a spiral or crystalline rod inside their flagella.

What are the two roles that protists play in ecological communities?

Symbionts and producers.

What is the primary function of pseudopodia in foraminiferans?

Used for swimming and feeding.

What type of algae are characterized by their green chloroplasts?

Green algae.

What are slime molds and how were they historically classified?

Slime molds were once thought to be fungi due to their spore-producing fruiting bodies.

What is the function of phytoplankton in marine ecosystems?

They are the main producers, forming the base of the aquatic food chain.

What is the significance of foram tests in marine sediments?

They form an extensive fossil record useful for studying historical ocean conditions.

What is the ecological relationship of mutualism in protists?

Some protist symbionts benefit their hosts, such as dinoflagellates with coral.

What type of protists are considered the closest relatives of plants?

Green algae.