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.
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Date Modified: 2022.0225