Orson lives near train tracks. Trains pass by several times a day sounding their horns. After living there for several years, he often doesn't even notice the sound of the trains passing by. What is this an example of?

Sensory adaptation

Explanation:

Sensory adaptation  is defined as the mechanism in which sensitivity decreases towards any component due to the continuous exposure towards it.This process increases attention towards other element in surroundings by decreasing alertness towards the already exposed stimulus for long time.

According to the question,Orson is impacted with sensory adaptation as he does not become aware by train's sound anymore as he has heard it from many years due to constant exposure.Thus, his senses are adapted to that sound of train and sensitivity is reduced.

how many characteristics are used to describe living things?

explanation:

the old way of life was represented by superstition, an angry god, and absolute submission to authority. the thinkers of the age of reason ushered in a new way of thinking. this new way championed the accomplishments of humankind. individuals did not have to accept despair. science and reason could bring happiness and progress. kings did not rule by divine right. they had an obligation to their subjects. europeans pondered the implications for nearly a century. americans put them into practice first.