protist

Examples of protist in the following topics:

• Cell Structure, Metabolism, and Motility

  • The cells of protists are among the most elaborate and diverse of all cells.
  • Many protist cells are multinucleated; in some species, the nuclei are different sizes and have distinct roles in protist cell function.
  • Protists exhibit many forms of nutrition and may be aerobic or anaerobic.
  • The majority of protists are motile, but different types of protists have evolved varied modes of movement .
  • Protists use various methods for transportation.

• Protists as Primary Producers, Food Sources, and Symbionts

  • Protists function as sources of food for organisms on land and sea.
  • Protists function in various ecological niches.
  • Protists are essential sources of nutrition for many other organisms.
  • In some cases, as in plankton, protists are consumed directly.
  • Protists do not only create food sources for sea-dwelling organisms.

• Protist Life Cycles and Habitats

  • Protist life cycles range from simple to extremely elaborate.
  • There are over 100,000 described living species of protists.
  • Paramecia are a common example of aquatic protists.
  • In addition to aquatic protists, several protist species are parasites that infect animals or plants and, therefore, live in their hosts.
  • Other protist species live on dead organisms or their wastes and contribute to their decay.

• Rhizaria

  • Rhizaria are a supergroup of protists, typically amoebas, that are characterized by the presence of needle-like pseudopodia.
  • Pseudopodia function to trap and engulf food particles and to direct movement in rhizarian protists.
  • The protist then transports its cytoplasm into the pseudopod, thereby moving the entire cell.
  • This type of motion, called cytoplasmic streaming, is used by several diverse groups of protists as a means of locomotion or as a method to distribute nutrients and oxygen.
  • Radiolarians display needle-like pseudopods that are supported by microtubules which radiate outward from the cell bodies of these protists and function to catch food particles.

• Protists as Plant Pathogens

  • Many protists act as parasites that prey on plants or as decomposers that feed on dead organisms.
  • Protist parasites prey on terrestrial plants and include agents that cause massive destruction to food crops.
  • The fungus-like protist saprobes are specialized to absorb nutrients from non-living organic matter, such as dead organisms or their wastes.
  • Saprobic protists have the essential function of returning inorganic nutrients to the soil and water.
  • Describe the ways in which protists act as decomposers and the actions of parasitic protists on plants

• Archaeplastida

  • Archaeplastida are a supergroup of protists that comprise red and green algae, which include unicellular, multicellular, and colonial forms.
  • It is well documented that land plants evolved from a common ancestor of these protists; their closest relatives are found within this group.
  • Molecular evidence supports that all Archaeplastida are descendants of an endosymbiotic relationship between a heterotrophic protist and a cyanobacterium.
  • Other protists classified as red algae lack phycoerythrins and are parasites.
  • It is well supported that this group of protists share a relatively-recent common ancestors with land plants.

• Protists as Human Pathogens

  • Many protists exist as parasites that infect and cause diseases in their hosts.
  • A significant number of protists are pathogenic parasites that must infect other organisms to survive and propagate.
  • Protist parasites include the causative agents of malaria, African sleeping sickness, and waterborne gastroenteritis in humans.
  • However, T. brucei has thousands of possible antigens; with each subsequent generation, the protist switches to a glycoprotein coating of a different molecular structure.

• Early Eukaryotes

  • Protists are eukaryotes that first appeared approximately 2 billion years ago with the rise of atmospheric oxygen levels.
  • Others invade the cells of other protists, animals, and plants.
  • Not all protists are microscopic.
  • Some protists are multicellular, such as the red, green, and brown seaweeds.
  • It is among the protists that one finds the wealth of ways that organisms can grow.

• Pre-Cambrian Animal Life

  • Early animal life (Ediacaran biota) evolved from protists during the pre-Cambrian period, which is also known as the Ediacaran period.
  • It is believed that early animal life, termed Ediacaran biota, evolved from protists at this time.
  • Some protist species called choanoflagellates closely resemble the choanocyte cells in the simplest animals, sponges.

• Protozoa

  • Originally, protozoa had been defined as unicellular protists with animal-like behavior (e.g., movement).
  • Protozoa were regarded as the partner-group of protists to protophyta, which have plant-like behavior (e.g., photosynthesis).
  • In general, protozoa are referred to as animal-like protists because they are capable of movement, or motile.
  • While there is no exact definition for the term protozoa, it often refers to a unicellular heterotrophic protist, such as the amoebas and ciliates.