- Cutting down trees has a negative impact on an ecosystem / organisms living in an ecosystem
- Logging is when humans cut down trees / forests for wood
- Hence, logging has a negative impact on the ecosystem

- Logging has a negative impact on the ecosystem
- Surface mining has a negative impact on the lithosphere / the biosphere / the ecosystem
- So, surface mining and logging have negative impacts on the ecosystem

- Killing means harming something causing death
- Harming an animal species has a negative impact on the population size of that species
- So, killing an animal has a negative impact on that animal's population

- Killing an animal has a negative impact on that animal's population
- Hunting is when a human kills an animal for food / recreation in the wild
- Hence, hunting has a negative impact on animal populations

- An animal is a kind of organism
- Organisms are a part of an environment
- Hence, animals are a part of the environment

- Animals are a part of the environment
- Ecosystem can mean environment
- Therefore, animals are a part of the ecosystem

- Hunting has a negative impact on animal populations
- Animals are a part of the ecosystem
- Hence, hunting has a negative impact on the ecosystem

- Surface mining and logging have negative impacts on the ecosystem
- Hunting has a negative impact on the ecosystem
- So, surface mining and logging and hunting have negative impacts on the ecosystem

- Surface mining and logging and hunting have negative impacts on the ecosystem
- Limiting a source of something tht has a negative impact on something else has a positive impact on that something else
- Hence, limiting mining and logging and hunting has a positive impact on the ecosystem

- Limiting mining and logging and hunting has a positive impact on the ecosystem
- National parks limit mining / logging / hunting
- Therefore, national parks have a positive impact on the ecosystem by limiting mining and logging and hunting

Hence, national parks have a positive impact on the ecosystem by limiting mining and logging and hunting
[Question]In 1872, the United States created a national park called Yellowstone. The park includes more than two million acres in the three states of Idaho, Montana, and Wyoming. Which statement best explains why national parks have a positive effect on ecosystems?
[Context]- Cutting down trees has a negative impact on an ecosystem / organisms living in an ecosystem 
- An animal is a kind of organism 
- Organisms are a part of an environment 
- Surface mining has a negative impact on the lithosphere / the biosphere / the ecosystem 
- National parks limit mining / logging / hunting 
- Killing means harming something causing death 
- Logging is when humans cut down trees / forests for wood 
- Harming an animal species has a negative impact on the population size of that species 
- Ecosystem can mean environment 
- Hunting is when a human kills an animal for food / recreation in the wild 
- Limiting a source of something tht has a negative impact on something else has a positive impact on that something else