Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object, co-developed between NOAA and NSTA, is the first of four Science Objects in the Resources and Human Impact SciPack. It explores how human beings, who live within and depend on Earth’s ecosystems, modify the land, ocean, and atmosphere. In all environments, organisms, including humans, cooperate or compete with one another for resources. These resources include food, air, water, and space. The size and rate of growth of all species, including humans, are affected by these environmental factors. In turn, these environmental factors are affected by the size and rate of growth of a population. Populations are limited in growth by the carrying capacity of the environment, which is the amount of life any ecosystem can support with its available space, energy, water, and food.