New species develop from existing species {species evolution} {evolution, species}|.
cells
On early Earth, heat, light, lightning, and meteor collisions formed carbon-containing molecules {organic molecule, life} with attached hydrogen, oxygen, nitrogen, sulfur, and phosphorus atoms. Simple organic molecules combined to make sugars, amino acids, nucleotides, and fatty acids, which combined to make carbohydrates, proteins, nucleic acids, and lipids. Large molecules can have shapes and structures and can have multiple binding and reaction sites. Structural molecules combined to form cells, viruses, and bacteriophages.
species
The first cells were the first species. Cells evolved into single-cell Archaea. Archaea evolved into bacteria and single-cell plants and animals. Single-cell organisms evolved into multicellular plants and animals. Multicellular animals evolved into invertebrates. One invertebrate species evolved into vertebrates. One vertebrate species evolved into fish. One fish species evolved into amphibians. One amphibian species evolved into reptiles. One reptile species evolved into mammals. One mammal species evolved into primates. One primate species evolved into monkeys. One monkey species evolved into apes. One ape species evolved into anthropoid apes (great apes) (hominids). One hominid species evolved into hominins (human ancestors) and Homo sapiens.
features
Prokaryotes have no nucleus. Eukaryotes have nuclei. Multicellular eukaryotes have neurons, sense cells, and muscle cells. Invertebrates can have bilateral symmetry, as in flatworms. Prechordates have notochord beginnings. Chordates have notochord in one development stage. Vertebrates have vertebrae. First fish have cartilage. Bony fish have bones. Lobe-finned fish have fin stumps. Fresh-water lobe-finned fish live in fresh water. Amphibians live on land and in water. Reptiles can live only on land. Mammals make milk. Primates have forward eyes. Old World monkeys have tricolor vision. Hominids, hominins, Homo, Homo habilis, Homo erectus, and Homo sapiens follow.
requirements
Evolution requires objects that carry coded information about how to build and maintain structures and functions and about how to replicate themselves. Evolution requires mechanisms to build objects, maintain objects, replicate objects faithfully, and provide slight variations in coded information. Evolution requires environment that has scarce resources. Evolution requires competition among similar objects. Objects then replicate more or better.
levels
Evolution can affect whole Earth, biomes, ecosystems, clades, or demes. Evolution can act on kingdoms, phyla, classes, orders, families, genuses, species, and varieties. Evolution can act on organs, tissues, cell lines, chromosomes, genes, exons, DNA functional regions, and nucleotides. Different levels can have different selection laws.
environment
If organisms change, other organisms change in response, and relations between other organisms and environment change. Change can cause exponential change. However, change is disruptive and decreases survival for most organisms.
Universal Darwinism
Systems that make copies, have variations, and have a selection mechanism can evolve {Universal Darwinism} [Dawkins, 1976] [Dawkins, 1986] [Dawkins, 1995].
intelligent design
Religionists can believe that God helped form some species. God used special structures and functions that distinguish humans from other species. However, intelligent design does not seem to allow human-appendix creation or maintenance. Complex life forms need to eat less complex forms. Intelligent design allows arbitrary changes and so has no testable hypotheses.
criticisms
Perhaps, both intelligent design and evolution are incorrect. Really, physical laws determine all, with no higher principles. Evolution works only haphazardly, with most species dying out.
Natural selection can make more-complex higher-level organisms {macroevolution}.
Structural constraints allow special forms {orthogenesis}| and guide evolution. Evolution can proceed directly from primitive species to higher species, without side branches. Evolution can jump to new species, without gradual steps.
Food specializations, migrations, and dangerous predators increase ecological-or-environmental pressures and increase evolution. Available genes, gene variability, adaptable behaviors, and food types resist evolution {phylogenetic inertia}.
Interbreeding organisms {species, ecology}| are basic biological units. Similar organisms share gene sets. Related species share similar structures, functions, and genes.
New species can arise from existing species {speciation}|.
hybridization
Hybrids between two different species sum chromosome-pair numbers. If eggs are fertile, self-fertilization starts new species intermediate between parent species. Chromosome doubling created many plant species and some animal species.
chromosome change
New species can arise through chromosome-number or gene-order change. Human chromosomes differ from chimpanzee chromosomes by inversions in nine chromosomes and by fusion of two chromosomes.
New species can appear if species diverge {principle of divergence} {divergence principle}. Typically, species gradually diverge into varieties, then subspecies, and then species. Behavior traits can diverge in ten generations. Major changes, such as brain development, diverge in 100 generations. New species diverge in 2000 generations. Species formation by divergence typically requires subspecies geographic isolation, to prevent gene dilution by other subspecies. Species diverge if organisms have different niches in same geographic area. Species converge if organisms live in separate areas with similar niches.
Species have original varieties {holotype}.
Organisms can perform similar functions using different structures {homoplasy}.
Organisms can have similar internal structures {homogeny} {homology, organism}|. Homology can result from keeping fundamental internal structure during evolution {parallelism, evolution} or having same external pressures during evolution and evolving to similar structures {convergence, evolution}.
Early eukaryotes incorporated primitive bacteria {endosymbiont hypothesis}, which evolved to mitochondria and chloroplasts.
Larval stages can become sexually mature {heterochrony}, to make new species.
Larval stages can become sexually mature, to make new species {paedomorphosis}.
Adult stages can add features, to make new species {peramorphosis}.
Earth has 2,500,000 species in many categories {classification, biology}. Earliest life was one-celled organisms. Archaea included thermophiles. Bacteria included proteobacteria and later cyanobacteria blue-green algae. Eukaryota included metamonad, parabasalid, trypanosoma, ciliates, and flagellates. Multicellular organisms arose from eukaryotes.
Many-celled organisms {metazoa}| {multicellular organism} include fungi, plants, and animals. Metazoa have specialized tissues.
evolution
Only eukaryotes can be multicellular organisms. About 650 million years ago, protozoa clustered, and cells differentiated into different tissues. Later eukaryotes evolved neurons. Later, jellyfish evolved sodium-ion channels for action potentials, which allow neurons to communicate over any distance.
gene transfer
Early eukaryotes incorporated early alpha-proteobacteria to make mitochondria. Early eukaryotes incorporated early cyanobacteria to make chloroplasts. Perhaps, eukaryote cytoskeleton and internal membranes came from early spirochetes, flagellates, or ciliates.
Organism names are genus name followed by species name {binomial system} {binomial nomenclature}|, such as Escherischia coli.
One-celled organisms {prokaryote}| {Monera} {Prokaryota} can have no distinct nucleus or other cell organelles. Prokaryotes include archaebacteria and eubacteria. Eubacteria include blue-green-algae cyanobacteria.
Cells {eukaryote}| (Eukaryota) (Eukarya) can have one cell nucleus surrounded by membrane. Eukaryotes include protozoa, fungi, plants, and animals. Eukaryotes are not Archaea, bacteria, blue-green algae, viruses, or bacteriophages.
The largest organism groups {kingdom, classification}| include non-nucleated single-cell archaebacteria (Archaea), non-nucleated single-cell eubacteria (Bacteria), nucleated single-cell protozoa (Protista) {protist}, nucleated fungi (Fungi), nucleated multi-cell plants (Plantae), and nucleated multi-cell animals (Animalia).
domains
Domains are Archaea, Bacteria, and Eukaryota. Archaea include thermophiles. Bacteria include proteobacteria, cyanobacteria, and other bacteria. Eukaryota include protozoa, yeast and other fungi, algae and other plants, and animals.
algae
Bacteria include cyanobacteria blue-green algae. Other algae are plants.
yeast
Fungi include yeast.
Kingdoms have major organism types {phylum} {phyla} {division, classification}|.
Divisions/phyla have subdivisions {class, classification}|.
Classes have subclasses {order, classification}|.
Orders have suborders {family, classification}|.
Families have subfamilies {genus, classification}|.
Genuses have interbreeding subgenuses {species, classification}|.
Species have subspecies {variety}|.
Humans have varieties {race, people}, such as north European white {Caucasian, people}, south European white {Mediterranean, people}, European and American Indian {mestizo}, Spanish-speaking or Portuguese-speaking country of South and Central America {Hispanic}, Central America {Latino}, Mexico {Chicano}, Africa {Negro} {black, person} {African-American}, and Asia {Asian} {Oriental, people} {Asian-American}.
types
People have three races, totaling 30 varieties.
Races {Caucasoid race} can include the varieties Mediterranean, Nordic, Alpine, Armenoid, and Dinaric. It can have more pale red, white, or light brown skin color, be taller, have longer or broader head, have light to dark hair, and have higher nosebridge. Armenoid has Caucasian and Mongoloid. Dinaric has Caucasian, Negroid, and Mongoloid.
Races {Negroid race} can include the varieties African, South Pacific, Melanesian, Oceania, White Hottentots, Bushmen, extinct Tasmanian, and Negritos or pygmies. It can have browner skin color, longer head, thicker lips, darker and coarser hair, darker eyes, lower nosebridge, and broader nostrils.
Races {Asiao-American Race} {Yellow Race} {Mongoloid race} can include the varieties Tungus in Siberia, Oriental, Eskimo, Indonesian, American Indian, Ainu in Japan, Australoid, and Veddoid, as well as Beijing Man, Lantian Man, and Jinniushan Man. Oriental has Chinese and Japanese. Oceanian has New Guinean, Australian, and Aborigine. Eskimos are more separate from Oriental than Oceanian. Mongoloid race started in Central and East Asia and went to South Asia and Southeast Asia. It can have more yellow or red skin color, be average height, have broader head, have less body hair, have darker eyes, have more epicanthic fold, have lower nosebridge, have higher eye sockets, have flat face bones, have higher superciliary arches, have more spade-shaped incisor insides, and have darker, straighter, and coarser hair.
Aborigines in Australia, Dravidians in south India, Polynesians in South Pacific Ocean, and Ainu in north Japan are hard to classify.
dispersion
Gene differences show that original Homo sapiens split into proto-Africans-and-Europeans, proto-Oceania, proto-American Indians, and proto-Oriental peoples. Then African Negritos and Bushmen separated from European Germanic and Mediterranean, so Europeans were intermediate between proto-African and proto-Oriental peoples.
Alu-repeat and short-tandem-repeat polymorphisms divide people into sub-Saharan Africa, Europe and West Asia, East Asia, Polynesia, and Americas groups. Perhaps, sub-Saharan Africa had two groups, including Mbuti pygmies. Genetic variants are 90% same, so group differences are maximum 10%.
cold adaptations
In cold regions, people tend to have shorter limbs, larger bodies, thicker eyelids, flatter noses, flatter foreheads, and broader cheeks.
factors
Decreased environmental pressures, increased mutation-causing agents, more socially-useful genes, greater specialization, and faster environment changes affect human evolution.
Y-chromosome studies indicate that modern human did not arise from multiple origins {multiregional hypothesis}.
Y-chromosome studies indicate that modern human races arose from African population [-89000 to -35000] {out-of-Africa hypothesis}.
Organism-classification systems {cladistics}| can depend on evolutionary, gene, structural, and functional features.
Species can split into independently evolving lines {clade}|. Different clades have different speciation rates, which can change over time. Clades determine classes and hierarchies, shown in branching diagrams {cladogram}. Cladogram nodes represent shared homologies.
Species members make species members similar to themselves. Among variations, surviving and reproducing member adaptations increase percentages {natural selection, evolution}|. Natural selection affects phenotypes, which relate to genotypes, which vary by mutation or allele recombination.
purpose
Natural selection has no goals. Natural selection is not progress.
creation
Natural selection explains species diversity and adaptations materialistically. Creation mechanisms need have no creator.
examples
Peppered moths become darker or lighter in industrial or rural areas, because birds eat lighter or darker moths in industrial or rural areas. Bacteria develop antibiotic resistance. Insects develop insecticide resistance. Rats develop rat-poison resistance. People still have sickle-cell anemia, because it helps fight malaria. People still have tuberculosis, because it has vitamin-D-receptor gene. People still have cystic-fibrosis CTFR gene, because it helps fight typhoid.
In unpredictable environments, organisms tend to have fast development, many offspring, and offspring with few defenses {r-selection} {r selection} {opportunistic selection}, so population can increase in favorable periods. Unpredictable environments have fewer species. In predictable environments, organisms tend to have slower development, few offspring, and offspring with defenses {k-selection} {K selection}, so population is stable. Predictable environments have more species {selection, evolution}.
Societies evolve through time {social evolution}. Social evolution includes new defenses against predators, higher feeding efficiencies, higher reproductive efficiencies, lower child death rates, more population stability, and new territories and environmental changes. Social evolution is more in stable environments. Social evolution seldom happens in variable environments.
Species members with best adaptations have highest percentage of survival to reproductive age {survival of the fittest, selection}|.
Species die out {extinction, species}|. Extinction typically happens soon after species formation. Extinction can happen if environment capacity is not enough. Increased speciation increases species extinction. Better adaptation prevents extinction. Slow variation and slow environmental change prevent extinction.
Parents can care for relatives' children, or relatives {kinship group} can help each other {kin selection}.
Species members compete for food, mates, and territory {competition, evolution}. Different species compete as predators and prey. Territory competition can cause convergence in dominant species and divergence in dominated species. Species typically relinquish habitat to competitors to keep preferred food, rather than staying and eating new foods.
Animals {predator} can eat other animals {predation, competition}|. Predators kill young, weak, and sick population members.
Aggressive behavior {aggression, ecology} protects territory, establishes dominance, protects sexual property, gets sex partners, disciplines, weans, imposes morals, predates, prevents predation, causes fear, expresses anger, and irritates. Most aggressions happen in competitions between species members. Examples are sexual aggression and food, territory, and status competition. Aggressive behavior patterns and levels evolve to adapt to environments. Species members vary in aggression levels.
In one ecosystem, competition can separate two similar species into separate niches {competition exclusion principle} {Gause's principle} {Gause principle}.
Species members have different gene-allele combinations and so have different trait combinations {variation, species}|.
causes
Mutations or allele recombinations cause genetic variation. Sex increases variation by increasing gene combination.
causes: selection
Evolution typically changes population allele ratios. Climate changes increase variation by increasing environment variety. Isolation increases variation by increasing environment variety.
amount
On average, 6% of vertebrate genes vary from wild type. On average, 15% of plant and invertebrate genes vary from wild type.
effects
Most changes are not adaptive. Species with greater genetic variation evolve faster, because they can use more environmental niches.
effects: duplication
Gene duplication and body part duplication allow duplicates to perform new functions, while originals perform old functions.
effects: whole body
Isolated changes can happen, but, to be adaptive, changes must work together with whole body, which then evolves in response to changes. For example, brain and body evolved together. Finger muscles, bone, nerves, blood supply, and brain motor-and-sensory finger regions evolved together, because dexterity required linked development.
Populations have gene-frequency changes {microevolution}. Microevolution includes gene flow, mutation pressure, and segregation distortion.
natural selection
Natural selection causes most gene-frequency changes. Natural selection can cause adaptations in constant environments or make new genes in fluctuating environments. Natural selection typically stabilizes gene frequencies and decreases homozygote percentage. New species arise from microevolutionary changes by accumulated changes in one direction {progressive evolution}.
drift
Random gene-splicing errors can cause heterozygosity loss by genetic drift, but this factor only affects small populations with inbreeding and consanguinity.
Allele mutations can negatively affect other alleles {canalizing}.
Immigrations into populations {gene flow} have major and fast gene-frequency effects, mainly through hybridization.
Strain combinations {hybrid}| generally show the good results of outbreeding {hybrid vigor}.
Bluish pigmented areas {Mongolian spot} {Mongol spot} {blue spot}, near spine bases, are present at birth in some Asian, south European, American Indian, and black infants and typically disappears during childhood.
Minor gene-frequency-change factors {mutation pressure} include differing allele-mutation rates.
Minor gene-frequency-change factors {segregation distortion} {meiotic drive} include unequal allele production by heterozygous parents.
Males typically have larger size and different shape than females {sexual dimorphism}|.
Trait presence depends on making trait {proximate factor} and keeping trait during reproduction. Trait survival in species members depends on environment, reproduction accuracy, and protection from change {ultimate factor}.
In environments, organisms can adjust behavior {adaptation, organism}| to survive and reproduce.
survival
To reproduce, species members must survive to sexual maturity. They must get food, avoid predators, fight disease, and maintain temperature, in a struggle for survival.
adaptation
To optimize environment use, species can use different foods, decrease development time, increase temperature range, increase air or water pressure range, use protective coloration, use warning coloration, use mimicry, and use other species.
varieties
Genes alleles vary proportions and interactions. Alleles remain available to survive slow, catastrophic, or cyclic environmental changes and to use different environment niches.
Species evolve to new varieties that can occupy surrounding environments {adaptive radiation} {radiation, adaptive}.
As structures shift, functions and adaptations can be different {functional shift} {cooptation}. Small structure shifts are not necessarily adaptive.
Organisms tend to evolve to larger size {Cope's rule} {Cope rule}. Larger organisms typically compete better for sex and food and have better protection from predators. Evolution tends to build larger and more complex organisms.
Animal tops and bottoms can have different colors {countershading}|. For example, bottoms can be light to match sky, and tops dark to match sea.
Organisms can alter their surroundings {environment} [Bateson, 1916] [Cosmides et al., 1992].
Species can pass through trait-development stages {grade, development}.
Negative feedback keeps involuntary muscle actions and chemical levels within normal ranges {homeostasis, animal}.
Longer lives {longevity}| are adaptive in stable environments, harsh and unpredictable environments, low progeny-survival-rate conditions, and low-fertility conditions.
Species can imitate other species {mimicry}|.
Organism features {preadaptation} can find new uses in new environments.
Species can change color for disguise {protective coloration}|.
Species can change skin or coat color and pattern to scare predators {warning coloration}|.
Evolution can make similar structures and functions in different species {convergent evolution}, to adapt to similar environments.
Evolution can make new species varieties, then subspecies, and then new species {divergent evolution}, to adapt to environment niches.
Species try to stay in environment niches {habitat tracking}.
Different habitats cause differences among people {polygenesis}.
New species arise in geographic isolation {allopatry}.
New species do not arise in same location {sympatry}.
Reproductive fitness {fitness} is adaptations that maximize offspring that live to make offspring. Fitness maximizes number of genes passed to offspring, which pass those genes to offspring.
Replicate number and adaptability depend on how well environment and species members interact {differential fitness}.
Gene alleles can affect other-allele fitness {epistasis} {epistasy} {epistatic coupling}. Gene mutation can affect mutation expression at other loci.
Ecosystems can maintain stable alleles in stable species {evolutionary stable strategy}. Evolutionary stable strategies apply game-theory Nash equilibria to ecosystems. If allele change reduces other-species fitness, it reduces species fitness.
One or two organisms can make new organisms {reproduction, organism}|, by sexual or asexual reproduction. Reptiles determine sex by egg temperature, not by Y-chromosome. Birds and mammals determine sex by chromosome. More sexual selection, higher fecundity, and higher rates of survival to reproducing age {differential reproduction} improve survival.
Reproductive processes take time and energy {reproductive effort} away from predation and protection and escape from predation. Reproductive effort is more if reproductive rate is more. Higher non-social animals have low reproductive effort, but higher social animals have high reproductive effort. Societies perform predation and food gathering most, anti-predation next, and reproduction least. Function time varies with food shortage, danger, or mating season.
Net population growth rate {reproductive rate} depends on death rate and birth rate. Young, weak, and sick population members have low reproduction. Older population members have high reproduction, producing more offspring and guarding them better. Stronger and more active population members have high reproduction, especially if they start new colonies and occupy new habitats. Species have optimum fertility rates, based on reproductive rates.
Natural objects {replicator} can copy themselves {replication, nature}, using available resources.
similarity
Replicators and replicates are alike. If replicate survives, it is like replicator survives.
mechanism
Replication requires reproduction mechanisms to assemble parts. Replication requires template patterns to copy.
comparison
Organisms use resources for replication, eating, and escaping, so they must balance these activities. Survival to reproductive age requires eating and escaping.
properties
Replicators are purposive, because they replicate. They are selfish, because they use resources to replicate. They are problem solving, because they gather and use resources to replicate. They are decision making, because they decide when and whether to replicate.
Species members must reproduce more organisms than environment can support {superfecundity, reproduction}. Superfecundity forces species members to compete against each other for mates and food, as well as other resources needed to reproduce. Species members must survive until sexual maturity, with strength to reproduce and win competitions for mates.
Species members must reach reproductive age and development to reproduce {sexual maturity}. Before that stage, species members cannot reproduce {sexual immaturity}.
Parents use energy and time {parental investment} to bring offspring to reproductive age. Children survive better if parents protect, feed, and teach them longer. However, parents can transmit more genes if they have more children, so parental investment is in equilibrium with children number.
factors
Stable predictable environment, longevity, regular reproduction, large size, territoriality, few offspring, difficult environments, many predators, and food specialization favor more and longer parental investment.
kin
Child raising by parents and relatives is altruistic kin selection. In many societies, non-relatives raise offspring, to gain child-raising experience and to limit aggression.
insects
Societies typically have high societal investment in offspring. Insect societies have no parental investment, because adults do not directly affect offspring behavior.
Two opposite-sex animals can produce {mating}| offspring by uniting sperm and egg. Sexual reproduction allows more variation and more sexual selection.
polygamy
Animals can have more than one mate. Polygamy is typical, because parental investment in children is typically unequal. Abundant food at least once a year, heavy predation, precocious young, greater longevity, different gender maturation ages, and different gender niches favor polygamy. High competition for mates leads to polygamy and mate monopolization. Polygamous species tend to have high sexual dimorphism.
monogamy
Animals can have one mate. Monogamy is rare. Monogamy happens in territories with scarce resources that require two animals to maintain or defend. Monogamy happens in difficult environments. Monogamy happens in species with early breeding. Monogamous species tend to have low sexual dimorphism.
Mating {breeding}| related individuals {inbreeding, alleles} tends to pair recessive alleles. Mating unrelated individuals {outbreeding} mixes alleles more.
Species can choose mates for good survival characteristics {selective breeding}|. High competition for mates leads to polygamy and mate monopolization.
Organisms select mates {sexual selection}|. Sexual behaviors tend to resist social evolution.
males
Sexual behaviors can be strategies to ensure that parent has conceived cared-for offspring. For males, sexual selection can involve keeping other males away from females, to prevent reproduction. Males can transmit more genes if they produce more females, rather than males.
males: displays
In many species, male pattern and behavioral displays lure females. Displays are fewer if food is scarcer or predators are more numerous.
females
For females, sexual selection involves selecting mates. Species with more receptive females have less fighting among males. Females can transmit more genes if they produce one male.
One organism can make copies {asexual reproduction}| by budding, cell fission, regeneration, sporulation, or parthenogenesis.
Asexual reproduction can have growth of special cells {budding}|, as in plants, hydra, and yeast.
Asexual reproduction can split cells {fission, cell}|, as in most cells.
Asexual reproduction can have differential growth in broken-off pieces {regeneration, reproduction}, as in flatworms and starfish.
Asexual reproduction can uses special haploid or diploid cells {spore} that detach from organisms {sporulation}|, as in most plants and some animals.
Reproduction can be haploid egg developing into adult {parthenogenesis}|, as in honeybee, wasp, and other arthropods.
Two organisms can make organisms similar to themselves by uniting their DNA {sexual reproduction}|, using conjugation, copulation, or hermaphroditism.
In hermaphroditism and copulation, haploid sperm enter haploid eggs {fertilization, reproduction} to form diploid cells. Fertilization can happen in oceans, rivers, or lakes {external fertilization} or inside bodies {internal fertilization}.
Sex organs {gonad}| produce sperm or eggs.
Sexual reproduction can use DNA-region exchange, after temporary union of two one-celled organisms {conjugation, reproduction}, as in bacteria.
Sexual reproduction can use mutual egg fertilization by sperm from two individuals that have both sex organs {hermaphroditism}|, as in oysters, tapeworms, and earthworms.
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.
Lamarck said that organism actions cause body changes {Lamarckianism}. For example, giraffes have long necks through continual neck stretching. This theory is false in general, but organism actions can affect evolution in small ways by affecting mutation, crossing-over, and translocation.
learning
Perhaps, neurohormones and neurotransmitters sent from brain can affect germ cells by changing gene expression or causing structural changes. Thus, learned behaviors can trigger chemicals that can alter germ cells. Alterations can correspond to learned behavior.
strength
Perhaps, fittest individuals can sustain useless or harmful innovations that weaker individuals cannot have. Innovations can then evolve into useful traits, and species can evolve.
energy
Perhaps, fittest individuals have more energy, matter, and organization to implement innovations that have no chance in weaker individuals. Innovations can then evolve into useful traits, and species can evolve.
Perhaps, all traits are adaptive {panadaptationism}. This theory is not true, because most traits are side effects and some traits are not good adaptations [Gould and Lewontin, 1979].
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