Sexual selection

differential survival and reproduction of individuals in nature due to differences in phenotype; a key mechanism of evolution

condition where the two sexes of the same species exhibit different characteristics beyond the differences in their sexual organs

permanent pointed projection on the head of various animals

Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages. Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book On the Origin of Species. He also identified sexual selection as a likely mechanism, but found it problematic.

mode of natural selection

principle that allele and genotype frequencies in a population will remain constant over generations in the absence of other evolutionary influences

quantitative representation of natural and sexual selection within evolutionary biology

thumb|upright=1.2|Esther is crowned in this 1860 [[woodcut by Julius Schnorr von Karolsfeld.]] Hypergamy (colloquially referred to as "dating up" or "marrying up") is a term used in social science for the act or practice of a person dating or marrying a spouse of higher mating value than themselves.

features that occur in an organism at sexual maturity

1871 book by Charles Darwin

mating pattern in which individuals with similar phenotypes (e.g. size, colour) mate with one another more often

parental expenditure (e.g. time, energy, resources) that benefits offspring

social value from sexual attractiveness

hypothesis in evolutionary biology

A roar /rɔːr/ is a type of animal vocalization that is loud, deep and resonating. Many mammals have evolved to produce roars and other roar-like vocals for purposes such as long-distance communication and intimidation. These include various species of big cats, bears, pinnipeds, deer, bovids, elephants, and simians.

how sexually reproducing multicellular organisms could have evolved from a common ancestor species

set of ritualized behaviours that enable an animal to communicate to other animals about specific stimuli

right|thumb|220px|During pregnancy, a two-way traffic of immune cells may occur through the placenta. Exchanged cells can multiply and establish long-lasting cell lines that are immunologically active even decades after giving birth. Microchimerism is the presence of a small number of cells in an individual that have originated from another individual and are therefore genetically distinct. This phenomenon may be related to certain types of autoimmune diseases although the responsible mechanisms are unclear. The term comes from the prefix "micro" + "chimerism" based on the hybrid Chimera of G

body of theoretical work examining communication between individuals

darts that some snails shoot into each other during mating

process of selection a romantic or sexual partner

passing of genes on to the next generation in a way that they too can pass on those genes

term in evolutionary biology

Sexual selection mechanism

system of sexual reproduction in a population

any process that contributes to the success of sperm fertilization in multiply-mated females.

thumb|300px|This Leucism|leucistic Indian peacock, Pavo cristatus, is unlikely to find a mate and reproduce in a natural setting due to its unusual coloration. However, its striking colour is appreciated by humans, and may be included in artificial [[selective breeding to produce more individuals with the leucistic phenotype.]]

evolutionary effects of sexual selection on humans

postulate in biology

lack of visible changes in ovulating females

competition between women over a potential mate

thumb|230px|A gynomorphic sculpture of Bacchus, Roman Imperial (2nd century CE), at the [[Musée du Louvre.]] Gynomorph is a word used to describe an organism with female physical characteristics.

species of arachnid

A quantitative ratio of sexually active population