1 a) characteristics of the environment that affect living things, they can be biotic or abiotic.
b) The quantity of ecological factors that is above or below the point at which an organismcannot develop properly.
2. Lack of oxygen: this happens in high altitudes where there are less oxygen in the atmosphere and usually causes problems for land animals. Basically their bodied have to increase in red blood cells and the lungs capacity to obtain the right amount of oxygen, like llamas.
Lack of food: food can be scare at certain times of the year such as winter. Most organisms who suffer from the lack of food survive this siuation by storing energy resources in their bodies by accumulating fats and carbohydrates in their cells and tissues, like bears. Another thing they do is to store food in hidden places, like squirrels. Or migrate.