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Homolog
In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the Bat wing development, wings of bats and Origin of avian flight, birds, the arms of primates, the front flippers of whales and the forelegs of Quadrupedalism, four-legged vertebrates like Canidae, dogs and crocodiles are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adaptation (biology), adapted to different purposes as the result of descent with modification from a Common descent, common ancestor. The term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was later explained by Charles Darwin's theory of evolution in 1859, but had been observed before this, from Aristotle's biology, Aristotle onwards, and it was explicitly analysed by Pierre Belon in 1555. In devel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sequence Homology
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a speciation event (orthologs), or a duplication event (paralogs), or else a horizontal (or lateral) gene transfer event (xenologs). Homology among DNA, RNA, or proteins is typically inferred from their nucleotide or amino acid sequence similarity. Significant similarity is strong evidence that two sequences are related by evolutionary changes from a common ancestral sequence. Alignments of multiple sequences are used to indicate which regions of each sequence are homologous. Identity, similarity, and conservation The term "percent homology" is often used to mean "sequence similarity”, that is the percentage of identical residues (''percent identity''), or the percentage of residues conserved with similar physicochemical properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology Vertebrates-en
Homology may refer to: Sciences Biology *Homology (biology), any characteristic of biological organisms that is derived from a common ancestor *Sequence homology, biological homology between DNA, RNA, or protein sequences *Homologous chromosomes, chromosomes in a biological cell that pair up (synapse) during meiosis *Homologous recombination, genetic recombination in which nucleotide sequences are exchanged between molecules of DNA * Homologous desensitization, a receptor decreases its response to a signalling molecule when that agonist is in high concentration *Homology modeling Homology modeling, also known as comparative modeling of protein, refers to constructing an atomic-resolution model of the "''target''" protein from its amino acid sequence and an experimental three-dimensional structure of a related homologous p ..., a method of protein structure prediction Chemistry *Homology (chemistry), the relationship between compounds in a homologous series *Homologous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genes
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a basic unit of heredity and 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 noncoding genes. During gene expression, the DNA is first copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes. Genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes (many different genes) as well as g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid resid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serial Homology
Serial homology is a special type of homology, defined by Owen as "representative or repetitive relation in the segments of the same organism."R:Webster 1913 in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913 Ernst Haeckel preferred the term "homotypy" for the same phenomenon. Classical examples of serial homologies are the development of forelimbs and hind limbs of tetrapods and the iterative structure of the vertebrae. See also * Deep homology * Evolutionary developmental biology Evolutionary developmental biology (informally, evo-devo) is a field of biological research that compares the developmental processes of different organisms to infer how developmental processes evolved. The field grew from 19th-century beginn ... References {{Reflist Evolutionary biology Comparative anatomy ... [...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. All living beings are in fact descendants of a unique ancestor commonly referred to as the last universal common ancestor (LUCA) of all life on Earth, according to modern evolutionary biology. 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 are they 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 s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended from a Common descent, common ancestor is now generally accepted and considered a fundamental concept in science. In a joint publication with Alfred Russel Wallace, he introduced his scientific theory that this Phylogenetics, branching pattern of evolution resulted from a process he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding. Darwin has been described as one of the most influential figures in human history and was honoured by Burials and memorials in Westminster Abbey, burial in Westminster Abbey. Darwin's early interest in nature led him to neglect his medical education at the University of Edinburgh Medical School, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aristotle's Biology
Aristotle's biology is the theory of biology, grounded in systematic observation and collection of data, mainly zoological, embodied in Aristotle's books on the science. Many of his observations were made during his stay on the island of Lesbos, including especially his descriptions of the marine biology of the Pyrrha lagoon, now the Gulf of Kalloni. His theory is based on his concept of form, which derives from but is markedly unlike Plato's theory of Forms. The theory describes five major biological processes, namely metabolism, temperature regulation, information processing, embryogenesis, and inheritance. Each was defined in some detail, in some cases sufficient to enable modern biologists to create mathematical models of the mechanisms described. Aristotle's method, too, resembled the style of science used by modern biologists when exploring a new area, with systematic data collection, discovery of patterns, and inference of possible causal explanations from t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Testicles
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testosterone. Testosterone release is controlled by the anterior pituitary luteinizing hormone, whereas sperm production is controlled both by the anterior pituitary follicle-stimulating hormone and gonadal testosterone. Structure Appearance Males have two testicles of similar size contained within the scrotum, which is an extension of the abdominal wall. Scrotal asymmetry, in which one testicle extends farther down into the scrotum than the other, is common. This is because of the differences in the vasculature's anatomy. For 85% of men, the right testis hangs lower than the left one. Measurement and volume The volume of the testicle can be estimated by palpating it and comparing it to ellipsoids of known sizes. Another method is to use calip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ovaries
The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. The ovaries also secrete hormones that play a role in the menstrual cycle and fertility. The ovary progresses through many stages beginning in the prenatal period through menopause. It is also an endocrine gland because of the various hormones that it secretes. Structure The ovaries are considered the female gonads. Each ovary is whitish in color and located alongside the lateral wall of the uterus in a region called the ovarian fossa. The ovarian fossa is the region that is bounded by the external iliac artery and in front of the ureter and the internal iliac artery. This area is about 4 cm x 3 cm x 2 cm in size.Daftary, Shirish; Chakravarti, Sudip (2011). Manual of Obstetrics, 3rd Edition. Elsevier. pp. 1-16. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reproductive Organ
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, are called the ''primary sex organs''. All others are called ''secondary sex organs'', divided between the external sex organs—the genitals or external genitalia, visible at birth in both sexes—and the internal sex organs. Mosses, ferns, and some similar plants have gametangia for reproductive organs, which are part of the gametophyte. The flowers of flowering plants produce pollen and egg cells, but the sex organs themselves are inside the gametophytes within the pollen and the ovule. Coniferous plants likewise produce their sexually reproductive structures within the gametophytes contained within the cones and pollen. The cones and pollen are not themselves sexual organs. Terminology The ''primary sex organs'' are the gonads, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebral Column
The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordates has been replaced by a segmented series of bone: vertebrae separated by intervertebral discs. Individual vertebrae are named according to their region and position, and can be used as anatomical landmarks in order to guide procedures such as lumbar punctures. The vertebral column houses the spinal canal, a cavity that encloses and protects the spinal cord. There are about 50,000 species of animals that have a vertebral column. The human vertebral column is one of the most-studied examples. Many different diseases in humans can affect the spine, with spina bifida and scoliosis being recognisable examples. The general structure of human vertebrae is fairly typical of that found in mammals, reptiles, and birds. The shape of the verte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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