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Bikont

life science Maturity 11-13 Next article →

Bikonts are a major group of eukaryotic organisms. The name Bikonta means "two flagella." A flagellum is a tiny, whip-like tail used for movement. Most members of this group possess two of these tails. This characteristic is shared by their presumed ancestor as well. Some bikonts consist of only a single cell. Other members are complex, multi-celled organisms. Understanding this group helps scientists map the history of life.

One unique way to identify bikonts involves their internal chemistry. They share a specific trait involving the fusion of two genes. These are the genes for thymidylate synthase (TS) and dihydrofolate reductase (DHFR). In bikonts, these two genes fuse into a single unit. This unit encodes one single protein that performs two different functions. In a different group called unikonts, these genes are translated separately. This genetic fusion is a key biological marker for the group.

Scientists use these traits to study evolutionary relationships. Research suggests that a unikont was the ancestor of several groups. Unikonts are eukaryotic cells that have only a single flagellum. These ancestors led to the opisthokonts, which include animals and fungi. They also led to the Amoebozoa. In contrast, a bikont is believed to be the ancestor of the Archaeplastida. This group includes plants and their relatives. Other descendants of bikonts include the Excavata, Rhizaria, and Chromalveolata.

Classification within the bikonts is a complex and changing field. The scientist Thomas Cavalier-Smith offered specific ways to group these organisms. He suggested that the Excavata and Rhizaria belong to a group called Cabozoa. He also proposed that the Archaeplastida and Chromalveolata form the Corticata. However, other scientific studies have suggested different connections. For example, one study suggests that Rhizaria and Chromalveolata form a single clade. A clade is a group that includes a common ancestor and all its descendants.

Newer research continues to challenge and refine these categories. In 2015, researchers including Derelle et al. proposed alternative names. They suggested using the term Opimoda for unikonts and Diphoda for bikonts. The name Diphoda is a new acronym. It is formed from the letters in DIscoba and diaPHOretickes. This change was meant to replace the older, traditional terms. These shifting names show how much our understanding of biology evolves.

Relationships between specific groups remain difficult to resolve. For instance, the Archaeplastida may be paraphyletic. This means the group might not include all the descendants of its common ancestor. Some groups, like Haptophyta and Cryptophyta, are usually seen as monophyletic. Scientists also study the SAR supergroup and the Viridiplantae. Recent reconstructions tried to link Archaeplastida and Hacrobia together. They called this the "HA supergroup" or "AH supergroup." This group was thought to be a sister clade to the SAR supergroup.

Even these newer groupings have faced scientific debate. The idea of the HA supergroup has fallen out of favor recently. This happened because the monophyly of Hacrobia has come under dispute. Scientists use cladograms to visualize these complicated family trees. A cladogram is a diagram that shows how different species are related. Some cladograms use data from 2012 and 2015. Others use more recent data from 2015 and 2016. These diagrams help us see where the roots of life might lie.

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