This constancy of the chemicals involved denotes that no particular reaction is taking place on the cells involved. For instance, during photosynthesis it would require CO2, H2O and photons to initiate the process. Thank you for your question. Please don't hesitate to ask in Brainly your queries.
Answer: Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population. If they are met, natural selection automatically results.
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