<span>Plants take in oxygen all the time for respiration.
Photosynthesis which begins by combining water and CO2, continues in the
"dark phase" in making the glucose molecule. Light is not used for this
part of the reaction so it is called dark , because light is needed for
the first part.
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This change in chromosome number is the result of B. Fertilization. Both of the individual gametes from the male and female combine together to produce a zygote or developing offspring that is diploid in most cases, and possess both sets of genetic content or chromosomal information, one from each parent.
