Examples
|
bryophytes |
- Bryophytes were long considered a natural group, defined as those land plants which lacked vascular systems. Molecular evidence shows that the bryophytes are not monophyletic since mosses, liverworts and hornworts are in fact separate lineages, with mosses closest to vascular plants. However, the three clades have a similar degree of complexity, and the "bryophyte grade" is a useful benchmark when analysing early plants - it contains information about the status of fossils which cannot always be classified into extant groups.
- Fish represent a grade, inasmuch as they have given rise to the land vertebrates. In fact, the three traditional classes of fish (Agnatha, Chondrichthyes and Osteichthyes) all represent evolutionary grades.
- Amphibians in the biological sense (including the extinct Labyrinthodonts) represent a grade, in that they are also the ancestors of the amniotes.
- Reptiles are composed of the cold-blooded amniotes, this excludes birds and mammals
- Dinosaurs were proposed to be the ancestors of birds as early as the 1860s. Yet the term sees both popular and scientific use as an evolutionary grade excluding birds, though some scientists insist on using "dinosaur" to cover birds too.
- Lizards as a unit represent an evolutionary grade, defined by their retention of limbs relative to snakes and Amphisbaenans.
Read more about this topic: Evolutionary Grade
Famous quotes containing the word examples:
“There are many examples of women that have excelled in learning, and even in war, but this is no reason we should bring ‘em all up to Latin and Greek or else military discipline, instead of needle-work and housewifry.”
—Bernard Mandeville (1670–1733)
“No rules exist, and examples are simply life-savers answering the appeals of rules making vain attempts to exist.”
—André Breton (1896–1966)
“It is hardly to be believed how spiritual reflections when mixed with a little physics can hold people’s attention and give them a livelier idea of God than do the often ill-applied examples of his wrath.”
—G.C. (Georg Christoph)