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 Ernst
Heinrich Philipp August Haeckel studied the embryos of many different
kinds of animals and made drawings, many of which
are still used in biology books. Seeing that the
embryos of very different types of animals often
looked remarkably similar during their earliest
stages of development, he formulated his theory
of recapitulation. |
 Jean
Baptiste Lamarck believed that if an
animal began using an organ more than it had in
the past, the size of that organ would increase
during its lifetime. For example,
if a giraffe stretched its neck to reach higher
leaves, a "nervous fluid" would flow
into its neck and make it longer over time. |
 Gregor Johann
Mendel was the first to conduct
detailed experiments in heredity by focusing on
individual characteristics within a single plant
species. His 30-plus years of study resulted in
his discovery of genes, and of how those genes
combine to create a wide diversity of
characteristics. |
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