* Physical features: This could be anything from the number of legs an animal has to the shape of its skull to the presence of feathers or fur.

* Genetic makeup: Comparing DNA sequences helps scientists determine how closely related different species are.

* Developmental patterns: How an animal develops from embryo to adult can be a key indicator of its evolutionary history.

* Behavioral traits: Shared behaviors like mating rituals, communication methods, or feeding habits can also point to relatedness.

* Ecological niche: How an animal interacts with its environment, its food sources, and its predators can help scientists understand its evolutionary adaptations.

By looking at all these shared characteristics, scientists can create a system of classification that reflects the evolutionary relationships between different animals.