Environmental Pressures
Analyze environmental pressures and how they drive natural selection in Grade 8 science. Students learn that predators, food scarcity, and harsh weather create survival challenges that affect organisms differently based on trait variation, favoring adaptive traits over non-adaptive ones.
Key Concepts
Environments are difficult places to live. Organisms face environmental pressures , such as predators, lack of food, or harsh weather.
These pressures create a struggle for survival. Because of variation , not all individuals struggle equally. Those with adaptive traits (like higher poison) are better equipped to handle the pressure than those without them.
Common Questions
What are environmental pressures in natural selection?
Environmental pressures are challenges in an ecosystem that affect survival—predators, food competition, disease, extreme weather. These pressures create conditions where some traits provide survival advantages while others do not, driving natural selection.
How does variation determine who survives environmental pressure?
Because individuals vary in their traits, they do not respond identically to environmental pressure. An individual with a beneficial variation—like higher poison against a predator—survives the pressure more easily than one without it. This differential survival is the engine of natural selection.
Can environmental pressures change over time, and what happens when they do?
Yes—environmental pressures change as ecosystems change. When pressures shift, previously non-adaptive traits may become adaptive and vice versa. A trait that was neutral (like high poison in the absence of predators) becomes strongly selected for when a new predator arrives.