Ecosystems — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Farmers spray pesticides to kill insects that damage their crops. How could this harm the broader ecosystem?
A) Pesticides only affect the target insects and have no impact on other organisms.
B) Pesticides can enter waterways, poison other organisms, and reduce biodiversity in the area.
C) Pesticides make the soil more fertile, which causes plants to grow too quickly.
D) Pesticides attract more predators to the farm, creating overcrowding.
The correct answer is B) Pesticides can enter waterways, poison other organisms, and reduce biodiversity in the area.. Farmers spray pesticides to kill insects that damage their crops. How could this harm the broader ecosystem — the answer is Pesticides can enter waterways, poison other organisms, and reduce biodiversity in the area..
2. A city builds houses on a wetland that once filtered water and provided habitat for many species. What is the most likely long-term effect?
A) Water quality downstream will improve because the houses block sediment.
B) The new neighborhood will attract more wildlife than the wetland did.
C) Nearby waterways may become polluted and species that depended on the wetland may decline.
D) The wetland will quickly regrow around the houses within a few months.
The correct answer is C) Nearby waterways may become polluted and species that depended on the wetland may decline.. A city builds houses on a wetland that once filtered water and provided habitat for many species. What is the most likely long-term effect — the answer is Nearby waterways may become polluted and species that depended on the wetland may decline..
3. Rising global temperatures cause sea ice to melt earlier each spring. How does this most directly affect polar bear populations?
A) Polar bears benefit because warmer water has more fish for them to eat.
B) Polar bears lose hunting platforms they need to catch seals, reducing their food supply.
C) Polar bears are unaffected because they can easily switch to eating land plants.
D) Polar bears move south and thrive in warmer forest ecosystems.
The correct answer is B) Polar bears lose hunting platforms they need to catch seals, reducing their food supply.. Rising global temperatures cause sea ice to melt earlier each spring. How does this most directly affect polar bear populations — the answer is Polar bears lose hunting platforms they need to catch seals, reducing their food supply..
4. A community creates a protected wildlife reserve where hunting and logging are banned. Which outcome is most likely over time?
A) Biodiversity in the reserve will decrease because species are confined to one area.
B) The reserve will have no effect because animals will simply move elsewhere.
C) Plant and animal populations will have a better chance of recovering and increasing.
D) Only predators will benefit because they no longer need to avoid humans.
The correct answer is C) Plant and animal populations will have a better chance of recovering and increasing.. A community creates a protected wildlife reserve where hunting and logging are banned. Which outcome is most likely over time — the answer is Plant and animal populations will have a better chance of recovering and increasing..
Part B: Fill in the Blank
Write the correct answer on each line.
1. The release of harmful substances into air, water, or soil is called pollution.
Pollution occurs when harmful substances like chemicals, trash, or exhaust fumes contaminate air, water, or soil, damaging ecosystems and the organisms in them.
2. When a species has no living members left anywhere on Earth, it is considered extinct.
Extinction means every single member of a species has died, like the dodo bird or woolly mammoth, and the species can never come back naturally.
3. Protecting and managing natural resources so they last for future generations is called conservation.
Conservation involves carefully protecting and managing natural resources like forests, water, and wildlife so they remain available for future generations to use and enjoy.
4. Burning coal and oil releases greenhouse gases that trap heat in Earth's atmosphere.
Greenhouse gases like carbon dioxide and methane act like a blanket around Earth, trapping heat from the sun and raising global temperatures when their levels increase.
5. A species whose population has dropped so low that it may become extinct is called endangered.
An endangered species has so few members left that it risks disappearing forever unless humans take steps like habitat protection and breeding programs to save it.