UC Berkeley
Image Caption
Trilobites, animals in the same clade as modern insects and crustaceans, lived over 300 million years ago. Their fossil record clearly suggests that several lineages underwent similar increases in segment number over the course of millions of years.
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This image is part of a series:
Patterns in macroevolution (1 of 5) Stasis
Many lineages on the tree of life exhibit stasis, which just means that they don't change much for a long time.
Patterns in macroevolution (2 of 5) Character change
Lineages can change quickly or slowly. Character change can happen in a single direction, such as evolving additional segments, or it can reverse itself by gaining and then losing segments.…
Patterns in macroevolution (4 of 5) Lineage splitting
Patterns of lineage-splitting (or speciation) can be identified by constructing and examining a phylogeny. The phylogeny might reveal that a particular lineage has undergone unusually frequent lineage-splitting, generating a "bushy"…