How many known bird species are there on the planet?

• Approximately 1,000

• Approximately 5,000

• Approximately 10,000

• Approximately 20,000

What is the classic definition of a species?

• Groups of organisms that share similar physical characteristics.

• Groups of organisms that live in the same geographical area.

• Groups of actually or potentially interbreeding natural populations that are reproductively isolated from other groups.

• Groups of organisms that have the same diet and habitat.

What is the initial step for speciation to occur?

• When individuals from different groups start interbreeding more frequently.

• When groups become separated in space or become reproductively isolated due to differences in form and behavior.

• When a population experiences a sudden increase in genetic diversity.

• When all individuals within a group develop identical traits.

When populations of a species become geographically isolated and evolve different mating behaviors over many generations, what is a common outcome regarding their ability to reproduce?

• They become more genetically similar, leading to increased interbreeding.

• They develop identical physical traits but remain genetically distinct.

• They may no longer be able to produce viable offspring, even if they attempt to mate.

• They always merge back into a single species once the isolation ends.

What are the main evolutionary processes that drive the formation of new species from existing ones?

• Only random genetic drift and environmental changes.

• Increased gene flow between different populations.

• Geographic isolation, natural selection, and sexual selection.

• Rapid changes in individual organisms during their lifetime.