What are some environmental factors (stimuli) that organisms respond to

Plants will lean toward sunlight 

fish will swim in an opposite direction if a leaf from a tree falls on the top of a calm pond 

some animals will develop thicker fur coats because of climate 

turtles poke their heads into their shell when they hear a noise or are frightened 

a community may move to a different area where theres more food and water cause a stream dried up 

man .. this list can go forever .. 

you might want to try limiting the scope 

try looking up 1. Charles Darwin and evolution 2. natural selection, sexual selection & gene flow 3. response to stimuli / ecosystems. large topic. GOOD LUCK!

Gravitational force i believe