A mutation is considered positive when it

Some mutations have a positive effect on the organism in which they occur. They are called beneficial mutations. ... They increase an organism's changes of surviving or reproducing, so they are likely to become more common over time. There are several well-known examples of beneficial mutations.

Mutations can be beneficial, benign, or malignant,

Size and shape of continents

light dependent reactions:

release oxygen during the photolysis of wateroccur in the granaproduce atp

light independent reactions:

fix carbon dioxide occur in the stromaproduce glucose

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