Dimorphism is when a species has two different forms with very different characteristics. Sexual dimorphism is a very most common version (for example, when the male of a species looks different from the female). Trimorphism is less common than dimorphism and involves three different forms.
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The timeline below shows where the term Dimorphism appears in The Origin of Species. The colored dots and icons indicate which themes are associated with that appearance.
Chapter 9
Reciprocal Dimorphism and Trimorphism. Some plants look the same on the outside but have different reproductive organs,...
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