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Embryo Drawings
Embryo drawing is the illustration of embryos in their developmental sequence. In plants and animals, an embryo develops from a zygote, the single cell that results when an egg and sperm fuse during fertilization. In animals, the zygote divides repeatedly to form a ball of cells, which then forms a set of tissue layers that migrate and fold to form an early embryo. Images of embryos provide a means of comparing embryos of different ages, and species. To this day, embryo drawings are made in undergraduate developmental biology lessons. Comparing different embryonic stages of different animals is a tool that can be used to infer relationships between species, and thus biological evolution. This has been a source of quite some controversy, both now and in the past. Ernst Haeckel at the University of Basel pioneered in this field. By comparing different embryonic stages of different vertebrate species, he formulated the recapitulation theory. This theory states that an animal's embry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comparative Anatomy
Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny (the evolution of species). The science began in the classical era, continuing in the early modern period with work by Pierre Belon who noted the similarities of the skeletons of birds and humans. Comparative anatomy has provided evidence of common descent, and has assisted in the classification of animals. History The first specifically anatomical investigation separate from a surgical or medical procedure is associated by Alcmaeon of Croton. Leonardo da Vinci made notes for a planned anatomical treatise in which he intended to compare the hands of various animals including bears. Pierre Belon, a French naturalist born in 1517, conducted research and held discussions on dolphin embryos as well as the comparisons between the skeletons of birds to the skeletons of humans. His research led to modern comparative a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caenogenesis
Caenogenesis (also variously spelled cenogenesis, kainogenesis, kenogenesis) is the introduction during embryonic development of characters or structure not present in the earlier evolutionary history of the strain or species, as opposed to palingenesis. Notable examples include the addition of the placenta in mammals. Caenogenesis constitutes a violation to Ernst Haeckel's biogenetic law and was explained by Haeckel as adaptation to the peculiar conditions of the organism's individual development. Other authorities, such as Wilhelm His, Sr., on the contrary saw embryonic differences as precursors to adult differences. See also *Ontogeny *Recapitulation theory The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"—is a historical hypothesis that the development of the embryo of an ... References Bibliography Gould, S.J. 1977. Ontogeny and Phylogeny. Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palingenesis
Palingenesis (; also palingenesia) is a concept of rebirth or re-creation, used in various contexts in philosophy, theology, politics, and biology. Its meaning stems from Greek , meaning 'again', and , meaning 'birth'. In biology, it is another word for recapitulationthe largely discredited hypothesis that the development of an advanced individual organism mirrors the development of entire, more primitive species. In political theory, it is a central component of Roger Griffin's analysis of fascism as a fundamentally modernist ideology. In theology, the word may refer to reincarnation or to Christian spiritual rebirth. Philosophy and theology The word ''palingenesis'' or rather ''palingenesia'' () may be traced back to the Stoics, who used the term for the continual re- creation of the universe. Similarly, Philo designated Noah and his sons as leaders of a renovation or rebirth of the earth, Plutarch spoke of the transmigration of souls, and Cicero focused on his own retur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastrula
Gastrulation is the stage in the early embryonic development of most animals, during which the blastula (a single-layered hollow sphere of Cell (biology), cells), or in mammals, the blastocyst, is reorganized into a two-layered or three-layered embryo known as the gastrula. Before gastrulation, the embryo is a continuous Epithelium, epithelial sheet of cells; by the end of gastrulation, the embryo has begun Cellular differentiation, differentiation to establish distinct cell lineages, set up the basic axes of the body (e.g. Anatomical terms of location#Dorsal and ventral, dorsal–ventral, Anatomical terms of location#Anterior and posterior, anterior–posterior), and internalized one or more cell types, including the prospective Gastrointestinal tract, gut. Gastrula layers In Triploblasty, triploblastic organisms, the gastrula is trilaminar (three-layered). These three germ layers are the ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer).Mundlos 2009p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylotype
In taxonomy, a phylotype is an observed similarity used to classify a group of organisms by their phenetic relationship. This phenetic similarity, particularly in the case of asexual organisms, may reflect the evolutionary relationships. The term is rank-neutral, so that phylotypes can be described at different levels, such as species, class, 97% genetic similarity, or homology. The term is often used in microbiology, since the genomes of prokaryotes, which freely exchange genetic material, do not lend themselves to classification via Linnean taxonomy as easily as do many eukaryotes The eukaryotes ( ) constitute the domain of Eukaryota or Eukarya, organisms whose cells have a membrane-bound nucleus. All animals, plants, fungi, seaweeds, and many unicellular organisms are eukaryotes. They constitute a major group of ... such as plants and animals. See also * Phylotypic stage References Taxonomy {{Biology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morphology (biology)
Morphology (from Ancient Greek μορφή (morphḗ) "form", and λόγος (lógos) "word, study, research") is the study of the form and structure of organisms and their specific structural features. This includes aspects of the outward appearance (shape, structure, color, pattern, size), as well as the form and structure of internal parts like bones and organs, i.e., anatomy. This is in contrast to physiology, which deals primarily with function. Morphology is a branch of life science dealing with the study of the overall structure of an organism or taxon and its component parts. History The etymology of the word "morphology" is from the Ancient Greek (), meaning "form", and (), meaning "word, study, research". While the concept of form in biology, opposed to function, dates back to Aristotle (see Aristotle's biology), the field of morphology was developed by Johann Wolfgang von Goethe (1790) and independently by the German anatomist and physiologist Karl Fried ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Descent
Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. According to modern evolutionary biology, all living beings could be descendants of a unique ancestor commonly referred to as the last universal common ancestor (LUCA) of all life on Earth. Common descent is an effect of speciation, in which multiple species derive from a single ancestral population. The more recent the ancestral population two species have in common, the more closely they are related. The most recent common ancestor of all currently living organisms is the last universal ancestor, which lived about 3.9 billion years ago. The two earliest pieces of evidence for life on Earth are graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. All currently living organisms on Earth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karl Ernst Von Baer
Karl Ernst Ritter von Baer Edler von Huthorn (; – ) was a Baltic German scientist and explorer. Baer was a naturalist, biologist, geologist, meteorologist, geographer, and is considered a, or the, founding father of embryology. He was a member of the Russian Academy of Sciences, a co-founder of the Russian Geographical Society, and the first president of the Russian Entomological Society, making him one of the most distinguished Baltic German scientists. Life Karl Ernst von Baer was born into the Baltic German noble Baer family ( et) in the Piep Manor ( et), Jerwen County, Governorate of Estonia (in present-day Lääne-Viru County, Estonia), as a knight by birthright. His patrilineal ancestors were of Westphalian origin and originated in Osnabrück. He spent his early childhood at Lasila manor, Estonia. He was educated at the Knight and Cathedral School in Reval (Tallinn) and the Imperial University of Dorpat (Tartu). In 1812, during his tenure at the univer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haeckel Drawings
Ernst Heinrich Philipp August Haeckel (; ; 16 February 1834 – 9 August 1919) was a German zoologist, naturalist, eugenicist, philosopher, physician, professor, marine biologist and artist. He discovered, described and named thousands of new species, mapped a genealogical tree relating all life forms and coined many terms in biology, including ''ecology'', ''phylum'', ''phylogeny'', ontogeny, and ''Protista.'' Haeckel promoted and popularised Charles Darwin's work in Germany and developed the debunked but influential recapitulation theory ("ontogeny recapitulates phylogeny"), wrongly claiming that an individual organism's biological development, or ontogeny, parallels and summarizes its species' evolutionary development, or phylogeny, using incorrectly drawn images of human embryonic development. Whether they were intentionally falsified, or drawn poorly by accident is a matter of debate. The published artwork of Haeckel includes over 100 detailed, multi-colour illustrations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes. During gene expression (the synthesis of Gene product, RNA or protein from a gene), DNA is first transcription (biology), copied into RNA. RNA can be non-coding RNA, directly functional or be the intermediate protein biosynthesis, template for the synthesis of a protein. The transmission of genes to an organism's offspring, is the basis of the inheritance of phenotypic traits from one generation to the next. These genes make up different DNA sequences, together called a genotype, that is specific to every given individual, within the gene pool of the population (biology), population of a given species. The genotype, along with environmental and developmental factors, ultimately determines the phenotype ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
