Protists

Protists- Groups

-Archaeplastida

Photosynthetic Organisms Overview

  • All organisms in this group are photosynthetic, including land plants and algae.

  • The group is undergoing changes; potential reorganization of the protist kingdom is expected.

Red Algae (Rhodophyta)

  • Characteristics:

    • Smaller group in terms of species count, known for possessing phycoerythrin, a red pigment.

    • The presence of the pigment may not always give algae a red appearance.

    • Multicellular

    • Non-Motile

  • Examples:

    • Gelidium: Used to make agar, a gel-like substance used in Petri dishes.

    • Porphyra: Used in sushi paper (nori) and farmed in various regions for culinary purposes.

Green Algae (Chlorophyta)

  • Characteristics:

    • The largest group of algae in terms of species diversity, often referred to as seaweeds.

    • Can be unicellular, multicellular, or colonial; most are non-motile.

    • Some unicellular green algae can tolerate extreme cold (e.g. pink algae found on snow).

  • Ecological Importance:

    • Photosynthetic, considered as close relatives to land plants.

Unikonta (Amorphea) (Excavata Supergroup)

  • Characteristics:

    • All members are heterotrophic.

  • Subgroups (Opisthokonts):

    • Nuclearids: Related to early fungal evolution.

    • Choanoflagellates: Considered some of the earliest forms linked to animals, possess similarities to sponges.

Slime Molds (Amoebozoans)

  • Types:

    • Plasmodial Slime Molds: Syncytial, meaning multiple nuclei share the same cytoplasm, appearing as a giant cell.

    • Cellular Slime Molds: Composed of distinct, individual cells packed closely together.

  • Differences:

    • Plasmodial molds are multinucleated and lack distinct cellular boundaries.

    • Cellular molds maintain individual cell walls.

  • Biological Significance:

    • Considered decomposers and play roles in nutrient cycling within ecosystems.

Unicellular Forms and Movement

  • Amoebas:

    • Utilize pseudopods for movement by rearranging their cytoskeleton.

    • Some form groups within the apistocon supergroup, including:

    • Gymnamoebas: Heterotrophic decomposers.

    • Entamoebas: Parasitic, known to cause diseases (e.g., amoebic dysentery).

  • Syncytial Tissue: Notably found in skeletal muscle in humans, showcasing the concept of syncytial structures in biology.

Summary

  • The study highlights the diversity of algae, specifically red and green algae, and their pivotal roles in ecosystems.

  • The evolving classification of eukaryotic organisms is considerable, especially regarding photosynthetic and heterotrophic supergroups.

  • Understanding slime molds and amoebas provides insight into earlier forms of life and their ecological functions.