1. Temperature: Organisms have an optimal temperature range for survival and growth. Temperatures that are too hot or too cold can be fatal.

2. Water Availability: All living things require water for survival. The amount of water available in an environment can vary greatly, from deserts to rainforests.

3. Sunlight (or lack thereof): Photosynthetic organisms like plants rely on sunlight for energy. Some organisms live in environments with low light availability (like deep ocean trenches), while others thrive in bright sunny areas.

4. Nutrient Availability: Nutrients are essential for growth and development. The type and availability of nutrients in the soil, water, or air can significantly impact the types of organisms that can survive in a particular environment.

These are just a few of the many factors that can vary in an environment. Organisms have evolved adaptations to cope with the specific conditions of their habitats.