Answer:
The starfish Pisaster ochraceus is a keystone species in the rocky marine intertidal communities off the northwest coast of North America. This predatory starfish feeds on the mussel Mytilus californianus and is responsible for maintaining much of the local diversity of species within certain communities. A keystone species is an organism that helps define an entire ecosystem. Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether. This means that if the species were to disappear from the ecosystem, no other species would be able to fill its ecological niche.
Explanation:
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Chemical change because a chemical change is any change that results in the formation of new chemical substances.
        
             
        
        
        
I think this would be the environment. That's my guess
        
             
        
        
        
Answer:
The correct answer is A) Have diverse cell wall compositions
Explanation:
Both bacteria and archaea comes under prokaryotes because they both lack a membrane-bound nucleus. The difference between archaea and bacteria is in their cell wall composition.
The bacterial cell wall is made up of peptidoglycan and the archeal cell wall is made up of pseudo-peptidoglycan. In bacteria, peptidoglycan contains N acetyl muramic acid and N acetyl glucosamine unit but in archaea, the N acetyl muramic unit is replaced by some other unit and the linkage of two units is also different in archaea. So the right answer is A.
 
        
                    
             
        
        
        
Answer:
B
Explanation:
Because the roots of the tree were what where controling the erosion 
Hope this helps :))