A population is best described as

Step 1: Analyze the question The question asks for the best definition of a population in ecology.

Step 2: Explain the concept In ecology, a population is a group of organisms of the same species living in the same area at the same time, and able to interbreed. Examples include all the tilapia fish in a pond or all the oil palm trees on a farm.

It helps to know the levels of ecological organization, from smallest to largest:

• Organism: a single living thing
• Population: the same species in one place
• Community: all the different populations (plants and animals) living together in an area
• Ecosystem: the community plus its non-living environment
• Biosphere: all ecosystems on Earth

Step 3: Evaluate the options

• A. A group of the same species of organisms living together. Correct. It has the key idea of "same species" in one place.
• B. A group of animals and plants living together. This mixes different species, so it describes a community.
• C. A group of insects and grasses. This is also a mix of different species, so it is not a population.
• D. Different species of wild animals. "Different species" rules this out immediately.

Step 4: Answer The correct option is A.

Exam tip: Think "Population = Pure one species" and "Community = Combination of species." If an option mentions different species or both plants and animals, it is not a population.