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Lack's Principle
Lack's principle, proposed by the British ornithologist David Lack in 1954, states that "the clutch size of each species of bird has been adapted by natural selection to correspond with the largest number of young for which the parents can, on average, provide enough food". As a biological rule, the principle can be formalised and generalised to apply to reproducing organisms in general, including animals and plants. Work based on Lack's principle by George C. Williams and others has led to an improved mathematical understanding of population biology. Principle Lack's principle implies that birds that happen to lay more eggs than the optimum will most likely have fewer fledglings (young that successfully fly from the nest) because the parent birds will be unable to collect enough food for them all. Evolutionary biologist George C. Williams notes that the argument applies also to organisms other than birds, both animals and plants, giving the example of the production of ovu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feeding Time, All The Time - Flickr - Lip Kee
Eating (also known as consuming) is the ingestion of food, typically to provide a heterotrophic organism with energy and to allow for growth. Animals and other heterotrophs must eat in order to survive — carnivores eat other animals, herbivores eat plants, omnivores consume a mixture of both plant and animal matter, and detritivores eat detritus. Fungi digest organic matter outside their bodies as opposed to animals that digest their food inside their bodies. For humans, eating is an activity of daily living. Some individuals may limit their amount of nutritional intake. This may be a result of a lifestyle choice, due to hunger or famine, as part of a diet or as religious fasting. Eating practices among humans Many homes have a large kitchen area devoted to preparation of meals and food, and may have a dining room, dining hall, or another designated area for eating. Most societies also have restaurants, food courts, and food vendors so that people may eat when away ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ovule
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center. The female gametophyte — specifically termed a ''megagametophyte''— is also called the ''embryo sac'' in angiosperms. The megagametophyte produces an egg cell for the purpose of fertilization. The ovule is a small structure present in the ovary. It is attached to the placenta by a stalk called a funicle. The funicle provides nourishment to the ovule. Location within the plant In flowering plants, the ovule is located inside the portion of the flower called the gynoecium. The ovary of the gynoecium produces one or more ovules and ultimately becomes the fruit wall. Ovules are attached to the placenta in the ovary through a stalk-like structure known as a ''funiculus'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biological Rules
A biological rule or biological law is a generalized law, principle, or rule of thumb formulated to describe patterns observed in living organisms. Biological rules and laws are often developed as succinct, broadly applicable ways to explain complex phenomena or salient observations about the ecology and biogeographical distributions of plant and animal species around the world, though they have been proposed for or extended to all types of organisms. Many of these regularities of ecology and biogeography are named after the biologists who first described them. From the birth of their science, biologists have sought to explain apparent regularities in observational data. In his biology, Aristotle inferred rules governing differences between live-bearing tetrapods (in modern terms, terrestrial placental mammals). Among his rules were that brood size decreases with adult body mass, while lifespan increases with gestation period and with body mass, and fecundity decreases with lif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Survival Of The Fittest
"Survival of the fittest" is a phrase that originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection. The biological concept of fitness is defined as reproductive success. In Darwinian terms, the phrase is best understood as "Survival of the form that will leave the most copies of itself in successive generations." Herbert Spencer first used the phrase, after reading Charles Darwin's ''On the Origin of Species'', in his ''Principles of Biology'' (1864), in which he drew parallels between his own economic theories and Darwin's biological ones: "This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called 'natural selection', or the preservation of favoured races in the struggle for life." ^ "Herbert Spencer in his ''Principles of Biology'' of 1864, vol. 1, p. 444, wrote: 'This survival of the fittest, which I have here sought to express in mechanical terms, is that whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules. The theory of evolution by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group Selection
Group selection is a proposed mechanism of evolution in which natural selection acts at the level of the group, instead of at the level of the individual or gene. Early authors such as V. C. Wynne-Edwards and Konrad Lorenz argued that the behavior of animals could affect their survival and reproduction as groups, speaking for instance of actions for the good of the species. In the 1930s, R.A. Fisher and J.B.S. Haldane proposed the concept of kin selection, a form of altruism from the gene-centered view of evolution, arguing that animals should sacrifice for their relatives, and thereby implying that they should not sacrifice for non-relatives. From the mid 1960s, evolutionary biologists such as John Maynard Smith, W. D. Hamilton, George C. Williams, and Richard Dawkins argued that natural selection acted primarily at the level of the gene. They argued on the basis of mathematical models that individuals would not altruistically sacrifice fitness for the sake of a group unless ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. However, only about 14% of these had been described by 2011. All species (except viruses) are given a two-part name, a "binomial". The first part of a binomial is the genus to which the species belongs. The second part is called the specific name or the specific epithet (in botanical nomenclature, also sometimes i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reproductive Fitness
Fitness (often denoted w or ω in population genetics models) is the quantitative representation of individual reproductive success. It is also equal to the average contribution to the gene pool of the next generation, made by the same individuals of the specified genotype or phenotype. Fitness can be defined either with respect to a genotype or to a phenotype in a given environment or time. The fitness of a genotype is manifested through its phenotype, which is also affected by the developmental environment. The fitness of a given phenotype can also be different in different selective environments. With asexual reproduction, it is sufficient to assign fitnesses to genotypes. With sexual reproduction, recombination scrambles alleles into different genotypes every generation; in this case, fitness values can be assigned to alleles by averaging over possible genetic backgrounds. Natural selection tends to make alleles with higher fitness more common over time, resulting in Darwinia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seed Plant
A spermatophyte (; ), also known as phanerogam (taxon Phanerogamae) or phaenogam (taxon Phaenogamae), is any plant that produces seeds, hence the alternative name seed plant. Spermatophytes are a subset of the embryophytes or land plants. They include most familiar types of plants, including all flowers and most trees, but exclude some other types of plants such as ferns, mosses, algae. The term ''phanerogams'' or ''phanerogamae'' is derived from the Greek (), meaning "visible", in contrast to the cryptogamae (), together with the suffix (), meaning "to marry". These terms distinguished those plants with hidden sexual organs (cryptogamae) from those with visible sexual organs (phanerogamae). Description The extant spermatophytes form five divisions, the first four of which are traditionally grouped as gymnosperms, plants that have unenclosed, "naked seeds": * Cycadophyta, the cycads, a subtropical and tropical group of plants, * Ginkgophyta, which includes a single living sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Biologist
Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life forms on Earth. Evolution is based on the theory that all species are related and they gradually change over time. In a population, the genetic variations affect the physical characteristics i.e. phenotypes of an organism. These changes in the phenotypes will be an advantage to some organisms, which will then be passed onto their offspring. Some examples of evolution in species over many generations are the Peppered Moth and Flightless birds. In the 1930s, the discipline of evolutionary biology emerged through what Julian Huxley called the modern synthesis of understanding, from previously unrelated fields of biological research, such as genetics and ecology, systematics, and paleontology. The importance of studying Evolutionary biology is ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fledgling (birds)
Fledging is the stage in a flying animal's life between hatching or birth and becoming capable of flight. This term is most frequently applied to birds, but is also used for bats. For altricial birds, those that spend more time in vulnerable condition in the nest, the nestling and fledging stage can be the same. For precocial birds, those that develop and leave the nest quickly, a short nestling stage precedes a longer fledging stage. All birds are considered to have fledged when the feathers and wing muscles are sufficiently developed for flight. A young bird that has recently fledged but is still dependent upon parental care and feeding is called a fledgling. People often want to help fledglings, as they appear vulnerable, but it is best to leave them alone. The USA National Phenology Network defines the phenophase (or life cycle stage) of fledged young for birds as "One or more young are seen recently departed from the nest. This includes young incapable of sustained fli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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