It occurs without energy input. Passive transporters let something across a membrane "with the gradient" in other words, substances travel from high concentration to low concentration, which is energetically favorable.
During the time of Fransesco Redi, the 17th century, people believed in spontaneous generation of organisms from non-living thing, or abiogenesis.
The people of that time believed that living things, such as flies, arise from non-living things spontaneously. Fransesco Redi challenged this belief and set up the famous fruit fly experiment to demonstrate that life comes from pre-existing life, and not from non-living things such as meat and fruit.
The characteristic variation is necessary.
1. Biology is the study of living organisms, divided into many specificalxed fields that covers their not
C. <span>smooth endoplasmic reticulum I am positive that this is the correct answer. </span>