Speciation can happen even when groups of living things are not separated by physical barriers, and this is called sympatric speciation. This means that a group of one species can split into two different species while still living in the same area.

Here are a couple of examples of Sympatric Speciation:

1. Diet Choices: Imagine two groups of animals that eat plants. If these groups start to prefer different types of plants, they may develop unique traits and choose different mates. Over time, this can lead to them not being able to breed with each other anymore.

2. Polyploidy in Plants: Some plants can have genetic changes that cause them to have more than two sets of chromosomes. This is called polyploidy. When this happens, a new plant species can form. This new species won't be able to mate with the original parent plants, even though they live in the same place.

In summary, sympatric speciation shows us that new species can form due to changes in behavior or genetics, not just because of physical barriers like mountains or rivers.