Protists

Definition

Protists are a diverse group of eukaryotic microorganisms that are mostly unicellular, but can also be multicellular, and are found in various aquatic and moist environments. They play vital roles in ecosystems, acting as producers, consumers, and decomposers, which contribute to nutrient cycling and energy flow in their habitats.

5 Must Know Facts For Your Next Test

1. Protists can be classified into three main groups: algae (plant-like), protozoa (animal-like), and slime molds (fungus-like).
2. They contribute significantly to global carbon cycling, with many protists performing photosynthesis and producing oxygen.
3. Some protists are pathogens, causing diseases in plants and animals, such as malaria caused by the protozoan Plasmodium.
4. Protists often form the base of aquatic food webs, supporting higher trophic levels by serving as food for larger organisms like fish.
5. Many protists have complex life cycles that can include both asexual and sexual reproduction, allowing for genetic diversity and adaptation.

Review Questions

• How do protists contribute to ecosystem functioning and energy flow?
  • Protists play essential roles in ecosystems as primary producers, consumers, and decomposers. Photosynthetic protists, such as algae, produce oxygen and organic matter through photosynthesis, forming the base of aquatic food webs. Heterotrophic protists consume bacteria and other microorganisms, helping control population dynamics. By decomposing organic material, protists recycle nutrients back into the ecosystem, ensuring energy flow continues effectively.
• Discuss the ecological impacts of pathogenic protists on both plant and animal populations.
  • Pathogenic protists can have significant ecological impacts by affecting plant health and animal populations. For instance, the protozoan Plasmodium causes malaria in humans and can lead to declines in human populations, which affects local economies and ecosystems. In plants, diseases caused by protists can result in crop failures, threatening food security and altering community dynamics. These impacts showcase how single-celled organisms can influence larger ecological interactions.
• Evaluate the role of environmental changes on the diversity and distribution of protist populations across different habitats.
  • Environmental changes such as climate change, pollution, and habitat destruction can significantly influence the diversity and distribution of protist populations. For example, rising temperatures can alter the productivity of photosynthetic protists, which may lead to shifts in community composition. Pollution may favor certain species over others, leading to reduced biodiversity. These changes can have cascading effects on entire ecosystems due to the interdependent relationships among organisms. Understanding these dynamics is crucial for predicting future ecological outcomes.

Related terms

Eukaryotes:

Organisms whose cells have a nucleus enclosed within membranes, distinguishing them from prokaryotes.

Algae:

Photosynthetic protists that can be unicellular or multicellular, playing a crucial role in aquatic ecosystems by producing oxygen and serving as a food source.

Protozoa: A subgroup of protists that are primarily heterotrophic and often motile, including organisms like amoebas and paramecia.