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All in the Family
  Tree of Life | One Common Ancestor | Diagramming Trees | Comparing Traits | Why It Matters

What are evolutionary relationships?

Living things (organisms) have two broad categories of relationships: active ones that they carry on while they're living (ecological relationships), and passive ones that link them to their past (evolutionary relationships).

For example, you have an ecological relationship with vegetables because you choose to eat them. But you also have an evolutionary relationship with those same vegetables, not because you've chosen it, but because you share a common ancestor.

In fact, since all organisms share one common ancestor (a 3.8 billion year old organism which likely resembled bacteria), they all have evolutionary relationships with each other. Pick any pair of organisms: peanuts and peacocks. Mold and monkeys. Amoebas and apples. Some are close, and some are distant, but they all share evolutionary relationships. The diagram of all these relationships is what Darwin called the "tree of life".

  -> How do scientists diagram evolutionary relationships?
  Tree of Life | One Common Ancestor | Diagramming Trees | Comparing Traits | Why It Matters
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