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The metabolism of prokaryotes is far more varied than that of eukaryotes, leading to many highly distinct prokaryotic types. For example, in addition to using photosynthesis or organic compounds for energy, as eukaryotes do, marine prokaryotes may obtain energy from inorganic compounds such as hydrogen sulfide.
Many protist species can switch between asexual reproduction and sexual reproduction involving meiosis and fertilization. [6] In contrast to the cells of prokaryotes, the cells of eukaryotes are highly organised. Plants, animals and fungi are usually multi-celled and are typically macroscopic. Most protists are single-celled and microscopic.
Their metabolism is far more varied than that of eukaryotes, leading to many highly distinct types. For example, prokaryotes may obtain energy by chemosynthesis. [34] Prokaryotes live nearly everywhere on Earth, including in environments as cold as soils in Antarctica, [35] or as hot as undersea hydrothermal vents and land-based hot springs. [33]
A protist is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus.While it is likely that protists share a common ancestor, the last eukaryotic common ancestor, [1] the exclusion of other eukaryotes means that protists do not form a natural group, or clade.
The cryptomonads (>100 species), also known as cryptophytes, are flagellated algae found in aquatic habitats of diverse salinity, characterized by extrusive organelles or extrusomes called ejectisomes. Their chloroplasts, of red algal origin, contain a nucleomorph, a remnant of the eukaryotic nucleus belonging to the endosymbiotic red alga. [88]
Cyanobacteria are globally widespread photosynthetic prokaryotes and are major contributors to global biogeochemical cycles. [25] They are the only oxygenic photosynthetic prokaryotes, and prosper in diverse and extreme habitats. [26] They are among the oldest organisms on Earth with fossil records dating back at least 2.1 billion years. [27]
The term Monera became well established in the 20s and 30s when to rightfully increase the importance of the difference between species with a nucleus and without. In 1925, Édouard Chatton divided all living organisms into two sections, Prokaryotes and Eukaryotes: the Kingdom Monera being the sole member of the Prokaryotes section. [23]
A protist (/ ˈ p r oʊ t ɪ s t /) is any eukaryotic organism (one with cells containing a nucleus) that is not an animal, plant, or fungus.The protists do not form a natural group, or clade, since they exclude certain eukaryotes with whom they share a common ancestor; [a] but, like algae or invertebrates, the grouping is used for convenience.