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