Relacionar Columnas Origin and evolution of lifeVersión en línea Theories of evolution por Isabel Pérez Cotorruelo 1 Endosimbiosis theory 2 Darwinism 3 Neutralism 4 Puntuated equilibrium 5 Neo-darwinism 6 Evolutionary development biology 7 Fixism 8 Lamarckism Living things do not change, species always stay the same Some genes act as switches for other gene groups during embrionic development. Individuals of a species that have more favourable characteristics survive more. The evolutionary process does not always take place in a slow gradual way. Instead in many cases new species are form rapidly. The necessity creates the organ. The acquired characteristics are transmitted to offsrping. Eukariotic cells originated as a result of two different types of bacteria joining together. Most mutations are neither benefitial nor harmful for the individuals that have them, so natural selection does not affect them. The reasons behind the variation within a species are mutations, genetic recombination and sexual reproduction.