Choose the correct word to complete the sentences to explain how different autotrophic organisms synthesize nutrients. Photosynthetic bacteria use (heat, light, chemical)
energy to manufacture organic compounds. Chemosynthetic bacteria derive energy from (chemicals, water, oxygen)

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".

unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.

c. establishing proper sleep hygiene