Temporal range: Mid Cambrian
Tichkaella is a genus of helcionellid from the Middle Cambrian. It has a strongly spiralled, smooth shell with concentric ridges that have low relief. Other than its looser coiling, it is very similar to Protowenella .
Protowenella is a genus of helcionellid from the Middle Cambrian of Australia. It has a strongly spiralled, smooth shell with concentric ridges that have low relief. Other than its tighter coiling, it is very similar to Tichkaella.
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped, meaning "two feet". Types of bipedal movement include walking, running, or hopping.
A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail: these five anatomical features define this phylum. Chordates are also bilaterally symmetric; and have a coelom, metameric segmentation, and a circulatory system.
Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce. Also called Darwinian theory, it originally included the broad concepts of transmutation of species or of evolution which gained general scientific acceptance after Darwin published On the Origin of Species in 1859, including concepts which predated Darwin's theories. It subsequently referred to the specific concepts of natural selection, the Weismann barrier, or the central dogma of molecular biology. Though the term usually refers strictly to biological evolution, creationists have appropriated it to refer to the origin of life, and it has even been applied to concepts of cosmic evolution, both of which have no connection to Darwin's work. It is therefore considered the belief and acceptance of Darwin's and of his predecessors' work—in place of other theories, including divine design and extraterrestrial origins.
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms and molecules.
Human evolution is the evolutionary process that led to the emergence of anatomically modern humans, beginning with the evolutionary history of primates—in particular genus Homo—and leading to the emergence of Homo sapiens as a distinct species of the hominid family, the great apes. This process involved the gradual development of traits such as human bipedalism and language, as well as interbreeding with other hominins, which indicate that human evolution was not linear but a web.
Homo habilis is a proposed archaic species of Homo, which lived between roughly 2.1 and 1.5 million years ago, during the Gelasian and early Calabrian stages of the Pleistocene geological epoch.
Zoology is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. The term is derived from Ancient Greek ζῷον, zōion, i.e. "animal" and λόγος, logos, i.e. "knowledge, study".
Social Darwinism is the application of the evolutionary concept of natural selection to human society. The term itself emerged in the 1880s, and it gained widespread currency when used after 1944 by opponents of these ways of thinking. The majority of those who have been categorized as social Darwinists did not identify themselves by such a label.
Agnatha is a superclass of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct species. The group is sister to all vertebrates with jaws, known as gnathostomes.
Amniotes are a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals. Amniotes lay their eggs on land or retain the fertilized egg within the mother, and are distinguished from the anamniotes, which typically lay their eggs in water. Older sources, particularly prior to the 20th century, may refer to amniotes as "higher vertebrates" and anamniotes as "lower vertebrates", based on the discredited idea of the evolutionary great chain of being.
Theistic evolution, theistic evolutionism, evolutionary creationism or God-guided evolution are views that regard religious teachings about God as compatible with modern scientific understanding about biological evolution. Theistic evolution is not in itself a scientific theory, but a range of views about how the science of general evolution relates to religious beliefs in contrast to special creation views.
Evolutionary biology is the subfield of biology that studies the evolutionary processes that produced the diversity of life on Earth, starting from a single common ancestor. These processes include natural selection, common descent, and speciation.
The simians are monkeys and apes, cladistically including: the New World monkeys or platyrrhines, and the catarrhine clade consisting of the Old World monkeys and apes.
The creation–evolution controversy involves an ongoing, recurring cultural, political, and theological dispute about the origins of the Earth, of humanity, and of other life. Creationism was once widely believed to be true, but since the mid-19th century evolution by natural selection has been established as an empirical scientific fact.
Sociocultural evolution, sociocultural evolutionism or cultural evolution are theories of cultural and social evolution that describe how cultures and societies change over time. Whereas sociocultural development traces processes that tend to increase the complexity of a society or culture, sociocultural evolution also considers process that can lead to decreases in complexity (degeneration) or that can produce variation or proliferation without any seemingly significant changes in complexity (cladogenesis). Sociocultural evolution is "the process by which structural reorganization is affected through time, eventually producing a form or structure which is qualitatively different from the ancestral form".
Paleornithology also known as Avian Paleontology is the scientific study of bird evolution and fossil birds. It is a mix of ornithology and paleontology. Paleornithology began with the discovery of Archaeopteryx. The reptilian relationship of birds and their ancestors, the theropod dinosaurs, are important aspects of paleornithological research. Other areas of interest to paleornithologists are the early sea-birds Ichthyornis, Hesperornis, and others. Notable paleornithologists are Storrs L. Olson, Alexander Wetmore, Alan Feduccia, Cécile Mourer-Chauviré, Philip Ashmole, Pierce Brodkorb, Trevor H. Worthy, Zhou Zhonghe, Yevgeny Kurochkin, Bradley C. Livezey, Gareth J. Dyke, Luis M. Chiappe, Gerald Mayr and David Steadman.
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres (110 ft) and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal often refers only to non-human animals. The study of non-human animals is known as zoology.
The history of molecular evolution starts in the early 20th century with "comparative biochemistry", but the field of molecular evolution came into its own in the 1960s and 1970s, following the rise of molecular biology. The advent of protein sequencing allowed molecular biologists to create phylogenies based on sequence comparison, and to use the differences between homologous sequences as a molecular clock to estimate the time since the last common ancestor. In the late 1960s, the neutral theory of molecular evolution provided a theoretical basis for the molecular clock, though both the clock and the neutral theory were controversial, since most evolutionary biologists held strongly to panselectionism, with natural selection as the only important cause of evolutionary change. After the 1970s, nucleic acid sequencing allowed molecular evolution to reach beyond proteins to highly conserved ribosomal RNA sequences, the foundation of a reconceptualization of the early history of life.
Polysporangiophytes, also called polysporangiates or formally Polysporangiophyta, are plants in which the spore-bearing generation (sporophyte) has branching stems (axes) that terminate in sporangia. The name literally means many sporangia plant. The clade includes all land plants (embryophytes) except for the bryophytes whose sporophytes are normally unbranched, even if a few exceptional cases occur. While the definition is independent of the presence of vascular tissue, all living polysporangiophytes also have vascular tissue, i.e., are vascular plants or tracheophytes. Fossil polysporangiophytes are known that have no vascular tissue, and so are not tracheophytes.
Homo erectus is a species of archaic humans that lived throughout most of the Pleistocene geological epoch. Its earliest fossil evidence dates to 1.8 million years ago. However, a 2017 analyses points to these specific fossils being more archaic, being related to H. naledi, which was considered one of the first homo species.