New species develop from existing species {evolution theory} {organic evolution} {theory of organic evolution} {theory of evolution}.
reproduction
Species members can make one or more organisms similar to themselves. Species members must reach sexual maturity to reproduce. Species members vary in fecundity.
competition
Species members reproduce more organisms than environment can support {superfecundity, evolution}, so species members compete against each other for mates and food. In environments, species members must get food, avoid predators, fight disease, and maintain temperature {struggle for survival} to reach sexual maturity, have health and strength to reproduce, and win competitions for mates.
adaptation
Species members have traits that affect the struggle for survival.
variation
Species members differ over species-characteristic ranges. Parents and reproduced organisms typically have similar values. Mutation, crossing over, and development can change values, add new values, or add or subtract characteristics. Characteristics and values can affect adaptation, competition, and fecundity by altering strength, size, or skill. See Figure 1. Species members with best-adapted characteristics and values have highest percentage of survival to reproductive age {survival of the fittest, evolution}.
environment
Environments have food sources, predators, diseases, climates, and cycles. Environments constrain species-member reproduction. Environments do not have enough food for all species members to stay alive, or be healthy and strong enough, to reproduce at reproductive age. Predators and diseases eat, kill, or harm species members, so they cannot reproduce at reproductive age. Environments have temperature cycles. Environments affect reproductive methods, such as how mates get together. See Figure 1.
natural selection
Species members compete for resources to reach reproductive age and reproduce. Species members vary in characteristics, so some species members have higher probability to win competitions and reproduce. Species members typically make members similar to themselves, so their characteristics increase percentages {natural selection, evolution theory}. Evolution shifts allele frequencies. See Figure 1. Evolution can also cause new genes.
species
Natural selection makes higher percentage of better-adapted species members, so species are better able to avoid extinction. Natural selection typically makes more surviving species members than before. Competition for food and mates becomes greater, causing higher pressure for survival. Over time, new species varieties arise. Over time, species varieties differ enough to be new species. For sexually reproducing species, new species members cannot reproduce with old species members. New species typically arise in isolated environments different from previous environments. New species can arise by combining two closely related species to make hybrids.
genes
Cells, body, and environment supply energy and needed chemicals to make DNA physical structures that can be stable, vary slightly, replicate accurately, copy more or less, and contain enough information. DNA has four different nucleotides chemically bonded in long or short sequences. DNA positions can have any nucleotide. Genes are templates for making DNA by replication, RNA by transcription, and protein by translation. Copying mechanisms have one error per million DNA units. Besides copying errors, DNA and RNA can suffer physical and chemical mutation damage that changes nucleotides or disrupts sequence {rearrangement}. In sexual reproduction, combining DNA from two sexes mixes sequence segments by crossing-over. These processes cause sequence changes. DNA reproduces, varies, and depends on environment and individual, so it faces competition, has adaptation, and goes through natural selection. Different species have different genes and alleles.
copying instructions
Copying instructions is more accurate than copying products, because products have more and different parts than instructions, and products typically have damage [Blackmore, 1999].
selection levels
Perhaps, natural selection applies to cell lines, organisms, demes, species, and clades, as well as genes. Selection levels can work synergistically, in opposition, or independently.
history
Evolution is not best or perfectly adapted but constrained by history, random effects, and physical laws [Feynman, 1965].
evolution theory: Summary 1
Objects that can reproduce same structures and functions with small changes, and that occupy environments in which they can die before reproduction, tend to evolve characteristics that fit environment. Objects retain only changes that make them survive better.
evolution theory: Summary 2
Organisms produce more offspring than survive to reproduce. Though people can think that God makes organisms that almost all survive to reproduce, except for natural accidents, or that match reproduction rate with death rate, all species actually produce extra offspring, as shown by Darwin. Offspring vary traits. It is easily observable fact that species members vary in observable traits. Observable traits have microscopic traits that vary. Offspring pass microscopic and so observable traits to offspring. It is easily observable fact that all organisms try to reproduce and that offspring typically resemble reproducers. Offspring with traits more favorable for survival to reproductive age produce more offspring with same traits.
evolution theory: Summary 3
Natural selection removes unfit and designs fit. Organisms vary in random ways. Variations typically are harmful but can be adaptive. Variations can accumulate over generations. Natural selection can make more-complex higher-level organisms.
evolution theory: Summary 4
Because organisms over-reproduce, nature has competing organisms and species, so new ones must replace or push aside existing ones {wedge, evolution}, leading to better adapted species. Typically, environment changes slowly compared to species changes.
evolution theory: Summary 5
In geographic areas, organism number increases geometrically through reproduction, but food and mating resources have limits. Species members and all organisms have struggle for existence. Individuals have various trait values. On average, process selects individuals with the most-fit trait values. Over time, natural selection causes organism gene-frequency changes [Darwin, 1859] [Darwin, 1871] [Judson, 1979] [Gould, 2002] [Huxley, 1884] [Ridley, 2003].
Specialized germ plasm reproductive cells transmit protein-coding genes that underlie physiological traits {gene theory}. Body cells do not affect germ-plasm genes, so genes cannot directly inherit learned behaviors {acquired characteristic} [Dubos, 1968] [Keller, 2000].
Evolution has general requirements {generalized theory of evolution}.
variation
Evolution requires objects with properties, such as size or color, with different values. Evolution requires mechanisms to switch among property values and/or mechanisms that can make new values or new properties.
reproduction
Evolution requires objects to have mechanisms that produce new objects with similar property values. Reproductive mechanisms typically use templates that carry coded information about object properties. Reproductive mechanisms do not copy perfectly but allow unit changes, such as mutations.
competition
Objects and reproductive mechanisms require resources. Object reproductions produce more objects than environment resources can support.
species
Systems can have only one object type or can have multiple objects, object groups, and/or hierarchies.
environment
Random events from inside or outside objects can affect objects, to cause new properties and values or affect reproduction.
evolution
Selective systems with variations among reproducing individuals who can pass on traits always evolve.
In small populations, new species can arise quickly under new environmental conditions {punctuated equilibrium} {quantum speciation}. Nature has many small populations. Fossils show many rapid species-evolution examples.
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Date Modified: 2022.0225