It's also defined on the absence of characters i. Not surprisingly then, the Kingdom Protista is difficult to define: Generally they are eukaryotes that are unicellular, though if multicellar e.
Life at small scales What are the advantages and disadvantages? Uncellularity restricts the size of the organism. As cell size increases, volume increase faster than surface area. Why is this important? All protists have one or more nuclei as well as other cell structures associated with multicellular life cell membrane, vacuoles, ribosomes, etc. Are protists simplier than multicellular organisms at a cellular level? Protista make up all or part of each group, but one of the groups below also include plants and another the animals and fungi.
This re-organization recognizes that the kingdom Protista is not monophyletic. Group Characteristics Examples Excavata many with "excavated groove on cell body Giardia Chromalveolate with plastids or pastid genes from endosymbiosis with red algae Diatoms Rhizaria often amoeboid forms with threadlike pseudopodia; united mainly based on molecular systematics radiolarians Archaeplastida with chlorplasts from endosymbiosis with cyanobacteria also includes plants green alga Unikonta extremely diverse group that includes amoeboid forms, animal-like protists, and fungi-like protists that are united mainly based on molecular systematics also includes fungi and animals slime molds.
Does molecular phylogeny sometimes complicate our attempt to describe taxonomic groupings? They are also common in the digestive tracts of animals and in the vascular tissues of plants. Others invade the cells of other protists, animals, and plants. Not all protists are microscopic. Some have huge, macroscopic cells, such as the plasmodia giant amoebae of myxomycete slime molds or the marine green alga Caulerpa , which can have single cells that can be several meters in size.
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. The organisms found in this kingdom are varied, and often seem like they might be more closely related to organisms in another kingdom: some protists resemble bacteria, some resemble fungi, and some resemble plants.
One group of these plant-like protists are the micro-algae. Watch this video to learn how these microscopic organisms could serve as a future fuel source:.
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