Are protists a polyphyletic group?

Because groups of protists do not share a common ancestor with each other that is not also shared with plants, fungi, and animals, “protists” represent a polyphyletic group. Only the characteristic of being eukaryotic unites, but is not exclusive to, this group.

Protists are paraphyletic

The contemporary protists form a paraphyletic group, as the representative taxa do not contain all descendants of their stem species, i.e. the multicellular taxa, which evolved several times independently.

Protista (Not monophyletic group; is paraphyletic because does not contain all descendants of its most recent common ancestor).

Protists are organisms in the Kingdom Protista. These organisms are eukaryotes, meaning they are made up of single or multiple cells which all contain a nucleus enclosed by a membrane. The protists are a diverse group of eukaryotes that cannot be classified as animals, plants, or fungi.

Because groups of protists do not share a common ancestor with each other that is not also shared with plants, fungi, and animals, “protists” represent a polyphyletic group.

However, the origin of eukaryotes is not comparable to the origin of these groups, and the bacterial contribution to eukaryogenesis should not be neglected. Eukaryotes are of polyphyletic origin, as their ancestor, LECA, sits on both branches of life—The archaeal (Asgard) and the bacterial branch (Alphaproteobacteria).

A polyphyletic group or assemblage is a set of organisms, or other evolving elements, that have been grouped together based on characteristics that do not imply that they share a common ancestor that is not also the common ancestor of many other taxa (of course, if “life” is monophyletic, then any set of organisms …

Examples of monophyletic groups include: Mammals, birds, angiosperms, and insects. Examples of paraphyletic groups may include: fish, gymnosperms, protists, and invertebrates.

Protists have nuclear membranes around their DNA. They also have other membrane-bound organelles. Many protists live in aquatic habitats, and most are motile, or able to move. Protists have complex life cycles that may include both sexual and asexual reproduction.

The first three kingdoms are well-defined monophyletic groups, but the “Kingdom Protista” is not monophyletic; It contains organisms which are more closely related to members of other kingdoms than they are to other protists.

The eukaryote Tree of Life (eToL) Represents the phylogeny of all eukaryotic lineages, with the vast bulk of this diversity comprising microbial ‘protists’.

Protists constitute a paraphyletic taxon since the latter is Based on the plesiomorphic character of unicellularity and does not contain all descendants of the stem species. Multicellularity evolved several times independently in metazoans, higher fungi, heterokonts, red and green algae.

The prokaryotes (single-celled life forms without cell nuclei) are a paraphyletic grouping, because they exclude the eukaryotes, a descendant group. Bacteria and Archaea are prokaryotes, but archaea and eukaryotes share a common ancestor that is not ancestral to the bacteria.

In fact, Archaea and Eukarya form a monophyletic group, not Archaea and Bacteria.

The supergroup archaeplastida includes the red algae, green algae and land plants. Each of these three groups have multicellular species and the green and red algae have many single-celled species. The Land plants Are not considered protists.

Why are protists considered paraphyletic? They include some but not all descendants of their most recent common ancestor.