The oviduct of female jawed vertebrates. It develops in both sexes from embryonic mesoderm, in association with the Wolffian duct, but becomes vestigial in the male. In most vertebrates it is paired (single in birds) and extends from a ciliated funnel, which opens into the coelom near the ovary, to the cloaca (when present). In [...]
Consisting of many cells. The oldest fossils of multicellular organisms are about 550 million years old (the start of the Cambrian). Large more complex multicellular organisms with specialized cell types require mechanisms to transport substances between cells, mechanisms of gene regulation, and an epigenetic system of cellular memory. See unicellular.
See quantitative inheritance.
(typological species concept) Pre-neoDarwin-ian definition of a species in which the members of a species are defined by their similarity to the standard bodyform for that species. The PHENETIC SPECIES CONCEPT is a modern version of the morphological species concept.
A vast late JURASSIC deposit in the USA stretching from Montana in the north to New Mexico in the south and from Nebraska in the east to Idaho in the west, named for the town of Morrison, Colorado. It was formed from flat areas of lowland swamps, lakes, and a network of rivers. Although the [...]
Evolutionary change in a taxon that occurs at different rates for different phenotypic characters.
Stone tools (200 000– 40 000 years ago) found at sites in Africa, Europe, and the Near East, most closely associated with NEANDERTHAL MAN but sometimes also associated with early Homo sapiens. The tools were more refined than ACHEULIAN TOOLS and included cutters and scrapers involving shaped blades, and spears with handles. See also Oldowan [...]
Jointed appendages on the heads of arthropods, modified in various ways for dealing with food. They consist of the labrum (upper lip), which is a single plate; a pair of mandibles (upper jaws), which have serrated edges; and a pair of maxillae (lower jaws), which also have serrated regions. In insects the second pair of [...]
Describing a type of dentition in which an animal has only one set of teeth during its lifetime, which are not replaced if they fall out. Compare di-phyodont; polyphyodont.