Answer:
Explanation:
Evidence for evolution comes from many different areas of biology:
Anatomy. Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
Molecular biology. DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are.
Biogeography. The global distribution of organisms and the unique features of island species reflect evolution and geological change.
Fossils. Fossils document the existence of now-extinct past species that are related to present-day species.
Direct observation. We can directly observe small-scale evolution in organisms with short lifecycles (e.g., pesticide-resistant insects).
Introduction
Evolution is a key unifying principle in biology. As Theodosius Dobzhansky once said, “Nothing in biology makes sense except in the light of evolution.”^1
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But what, exactly, are the features of biology that make more sense through the lens of evolution? To put it another way, what are the indications or traces that show evolution has taken place in the past and is still happening today?
Evolution happens on large and small scales
Before we look at the evidence, let's make sure we are on the same page about what evolution is. Broadly speaking, evolution is a change in the genetic makeup (and often, the heritable features) of a population over time. Biologists sometimes define two types of evolution based on scale:
Macroevolution, which refers to large-scale changes that occur over extended time periods, such as the formation of new species and groups.
Microevolution, which refers to small-scale changes that affect just one or a few genes and happen in populations over shorter timescales.
Microevolution and macroevolution aren’t really two different processes. They’re the same process – evolution – occurring on different timescales. Microevolutionary processes occurring over thousands or millions of years can add up to large-scale changes that define new species or groups.
The evidence for evolution
In this article, we'll examine the evidence for evolution on both macro and micro scales.
First, we'll look at several types of evidence (including physical and molecular features, geographical information, and fossils) that provide evidence for, and can allow us to reconstruct, macroevolutionary events.
At the end of the article, we'll finish by seeing how microevolution can be directly observed, as in the emergence of pesticide-resistant insects.
Anatomy and embryology
Darwin thought of evolution as "descent with modification," a process in which species change and give rise to new species over many generations. He proposed that the evolutionary history of life forms a branching tree with many levels, in which all species can be traced back to an ancient common ancestor.
