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- 1From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Geologists define rocks as aggregates of minerals, which are naturally occurring, inorganic substances with specific chemical compositions and structures. A rock can consist of many crystals of one mineral or...
- 2From:The Gale Encyclopedia of Science (Vol. 4. 6th ed.)The history of how the modern human species, Homo sapiens sapiens, evolved is reconstructed by evidence gathered by paleontologists, anthropologists, archeologists, anatomists, biochemists, behavioral scientists, and...
- 3From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Protozoa are a diverse group of single-celled organisms that include more than 50,000 species. The vast majority are microscopic, many measuring less than 1/200 mm, but some, such as the freshwater Spirostomun, may reach...
- 4From:The Gale Encyclopedia of Science (Vol. 4. 6th ed.)Often referred to as a living fossil, the horseshoe crab has changed relatively little morphologically over the past 450 million years. The large greenish brown, helmet-like dorsal plate, called either the cephalothorax...
- 5From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Fossils are a window into Earth's history and the evolution of life. The term fossil literally means something that has been “dug up, ”but its modern meaning is restricted to preserved evidence of past life. Such...
- 6From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Flora describes the assemblage of plant species that occurs in some particular area or large region. Flora can refer to a modern assemblage of plant species or to a prehistoric group of species that is inferred from the...
- 7From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Paleobotany endeavors to reconstruct past climates and regional vegetation systems by studying the fossilized remains of plants or preserved pollen samples. Such studies have yielded information regarding global climate...
- 8From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Paleontology is the study of ancient animal life and how it developed. It is divided into two subdisciplines, invertebrate paleontology and vertebrate paleontology. Paleontologists use two lines of evidence to learn...
- 9From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Eukaryotae, or eukaryotic cells, are cells that have their genetic material contained within a specialized membrane (the nuclear membrane) that is located inside the cell. Eukaryotic cells are ancient. Fossils of...
- 10From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Although historical time covers centuries and archeological times covers millennia, geologic time describes the span of time—billions of years—revealed in the fossil and rock record. Geochronology is the science of...
- 11From:The Gale Encyclopedia of Science (Vol. 4. 6th ed.)Liverworts are one of three classes in the plant phylum Bryophyta. The other two classes are mosses and hornworts. Liverworts are small green terrestrial plants. They do not have true roots, stems, or leaves. Instead,...
- 12From:The Gale Encyclopedia of Science (Vol. 4. 6th ed.)The koala (Phascolarctos cinereus) is a tree-living Australian marsupial, or pouched mammal, which early English settlers in Australia called the native bear. The koala is not a bear, but is the only living species in...
- 13From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Geology is the study of Earth. Modern geology includes studies in seismology (earthquake studies), volcanology, energy resources exploration and development, tectonics (structural and mountain building studies),...
- 14From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Rates of evolution change vary widely, among characteristics and among species. Evolutionary rate of change can be estimated by examining fossils and species that are related to each other. The rate of change is governed...
- 15From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)That all existing varieties of life have evolved from simpler, interrelated ancestors is one of the most solidly established facts known to modern science, and it is the basis of all modern biological science. Evidence...
- 16From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)In the modern era of Earth history, our planet, the third planet outward from the Sun, is home to millions of species. However, approximately 4.54 billion years earlier, Earth was just forming—devoid of, and very hostile...
- 17From:The Gale Encyclopedia of Science (Vol. 3. 6th ed.)Fauna is a generic term for the list of animal species occurring in a particular region. Fauna can refer to a prehistoric collection of animals, as might be inferred from the fossil record, or to a modern assemblage of...
- 18From:The Gale Encyclopedia of Science (Vol. 6. 6th ed.)Palynology is the study of fossil pollen (and sometimes plant spores) extracted from lake sediment, peat bog, or other matrices. The most common goal of palynological research is to reconstruct the probable character of...
- 19From:The Gale Encyclopedia of Science (Vol. 2. 6th ed.)Diatoms are microscopic, single-celled algae found in both freshwater and marine ecosystems. Many diatom species are planktonic, although some are found clinging to surfaces or in sediments. Diatoms are surrounded by...
- 20From:The Gale Encyclopedia of Science (Vol. 1. 6th ed.)Animals are multicellular, eukaryotic organisms that are capable of voluntary, spontaneous movements, often in response to sensory input. Animal cells are differentiated from cells of other eukaryotes in that they do not...