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Nuptial Pad
A nuptial pad (also known as thumb pad, or nuptial excrescence) is a secondary sex characteristic present on some mature male frogs and salamanders. Triggered by androgen hormones, this breeding gland (a type of mucous gland) appears as a spiked epithelial swelling on the forearm and prepollex that aids with grip, which is used primarily by males to grasp (or clasp) females during amplexus. They can also be used in male–male combat in some species. Historical background Austrian biologist Paul Kammerer experimented on midwife toads' nuptial pads. He used the offspring's apparent enlargening from generation-to-generation as evidence of Lamarckian evolution. Examples Many amphibian species manifest nuptial pads for use in amplexus, an example being the rough-skinned newt The rough-skinned newt or roughskin newt (''Taricha granulosa'') is a North American newt known for the strong toxin exuded from its skin. Appearance A stocky newt with rounded snout, it ranges from l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplexus
Amplexus (Latin "embrace") is a type of mating behavior exhibited by some externally fertilizing species (chiefly amphibians and horseshoe crabs) in which a male grasps a female with his front legs as part of the mating process, and at the same time or with some time delay, he fertilizes the eggs, as they are released from the female's body. In amphibians, females may be grasped by the head, waist, or armpits, and the type of amplexus is characteristic of some taxonomic groups. Amplexus involves direct contact between male and female, distinguished from other forms of external fertilization, such as broadcast spawning, where sperm and eggs are freely shed into water without direct contact by individuals. In order for amplexus to be initiated, male frogs must first find a mate by attracting one through calls, typically in the evening. Once a male has successfully attracted a mate, the process of amplexus begins, while the unsuccessful males are forced to continue their search fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphibian Anatomy
Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this. The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to reptiles like lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; in recent decades there has been a dramatic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rough-skinned Newt
The rough-skinned newt or roughskin newt (''Taricha granulosa'') is a North American newt known for the strong toxin exuded from its skin. Appearance A stocky newt with rounded snout, it ranges from light brown to olive or brownish-black on top, with the underside, including the head, legs, and tail, a contrasting orange to yellow. The skin is granular, but males are smooth-skinned during breeding season. They measure 6 to 9 cm in snout-to-vent length, and 11 to 18 cm overall. They are similar to the California newt (''Taricha torosa'') but differ in having smaller eyes, yellow irises, V-shaped tooth patterns, and uniformly dark eyelids. Males can be distinguished from females during breeding season by large swollen vent lobes and cornified toe pads. Distribution and subspecies Habitats of rough-skinned newts are found throughout the Pacific Northwest. Their range extends south to Santa Cruz, California, and north to Alaska. They are uncommon east of the Cascade ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphibian
Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial animal, terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this. The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to reptiles like lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; in re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lamarckian Evolution
Lamarckism, also known as Lamarckian inheritance or neo-Lamarckism, is the notion that an organism can pass on to its offspring physical characteristics that the parent organism acquired through use or disuse during its lifetime. It is also called the inheritance of acquired characteristics or more recently soft inheritance. The idea is named after the French zoologist Jean-Baptiste Lamarck (1744–1829), who incorporated the classical era theory of soft inheritance into his theory of evolution as a supplement to his concept of orthogenesis, a drive towards complexity. Introductory textbooks contrast Lamarckism with Charles Darwin's theory of evolution by natural selection. However, Darwin's book ''On the Origin of Species'' gave credence to the idea of heritable effects of use and disuse, as Lamarck had done, and his own concept of pangenesis similarly implied soft inheritance. Many researchers from the 1860s onwards attempted to find evidence for Lamarckian inheritance, but the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Midwife Toad
Midwife toads are a genus (''Alytes'') of frogs in the family Alytidae (formerly Discoglossidae), and are found in most of Europe and northwestern Africa. Characteristic of these toad-like frogs is their parental care; the males carry a string of fertilised eggs on their backs, hence the name "midwife". The female expels a strand of eggs, which the male fertilizes externally. He then wraps them around his legs to protect them from predators in the water. When they are ready to hatch, the male wades into shallow water, where he allows the tadpoles to leap out of their eggs. Five separate species of midwife toads are found across western Europe, northern Africa, and Majorca. Midwife toads can be found in the snows of the Pyrenees, living at heights of 5,000–6,500 feet in areas such as the Néouvielle massif. Unlike the thin tongue of many amphibians, the midwife's tongue is round and flattened; its former family name, Discoglossidae, means "round tongue". In parts of France, midwi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paul Kammerer
Paul Kammerer (17 August 1880, in Vienna – 23 September 1926, in Puchberg am Schneeberg) was an Austrian biologist who studied and advocated Lamarckism, the theory that organisms may pass to their offspring characteristics acquired in their lifetime. Biography Education He began his academic career at the Vienna Academy by studying music but graduated with a degree in biology.Koestler, Arthur (1973). ''The Case of the Midwife Toad''. Vintage (first published 1971). Biological research Kammerer's work in biology largely involved altering the breeding and development of amphibians. He made ovoviviparous fire salamanders become viviparous, and viviparous alpine salamanders become ovoviviparous. In lesser-known experiments, he manipulated and bred olms. He made olms produce live young and bred dark-colored olms with full vision. He supported the Lamarckian theory of heritability of acquired characteristics, and he experimented extensively in an effort to prove the theory. Kamm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Sex Characteristic
Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a species, but unlike the sex organs (primary sex characteristics), are not directly part of the reproductive system. Secondary sex characteristics are believed to be the product of sexual selection for traits which display fitness, giving an organism an advantage over its rivals in courtship and in aggressive interactions. Secondary sex characteristics include, for example, the manes of male lions, the bright facial and rump coloration of male mandrills, and horns in many goats and antelopes. These characteristics are believed to be produced by a positive feedback loop known as the Fisherian runaway produced by the secondary characteristic in one sex and the desire for that characteristic in the other sex. Male birds and fish of many species ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forearm
The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anatomy, technically, means only the region of the upper arm, whereas the lower "arm" is called the forearm. It is homologous to the region of the leg that lies between the knee and the ankle joints, the crus. The forearm contains two long bones, the radius and the ulna, forming the two radioulnar joints. The interosseous membrane connects these bones. Ultimately, the forearm is covered by skin, the anterior surface usually being less hairy than the posterior surface. The forearm contains many muscles, including the flexors and extensors of the wrist, flexors and extensors of the digits, a flexor of the elbow (brachioradialis), and pronators and supinators that turn the hand to face down or upwards, respectively. In cross-section, the for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epithelial
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellular matrix. Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs. An example is the epidermis, the outermost layer of the skin. There are three principal shapes of epithelial cell: squamous (scaly), columnar, and cuboidal. These can be arranged in a singular layer of cells as simple epithelium, either squamous, columnar, or cuboidal, or in layers of two or more cells deep as stratified (layered), or ''compound'', either squamous, columnar or cuboidal. In some tissues, a layer of columnar cells may appear to be stratified due to the placement of the nuclei. This sort of tissue is called pseudostratified. All glands are made up of epitheli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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