What do you think the embryological steps we see in the early development of the invertebrates tells us about evolutionary history? How did those steps evolve? Please use specific examples and be prepared to defend your answer.
Since this is not my area of expertise, I searched Google under the key words "embryology invertebrates evolution" to get this:
http://www.google.com/search?client=safari&rls=en&q=embryology+invertebrates+evolution&ie=UTF-8&oe=UTF-8
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
The embryological steps observed in the early development of invertebrates provide crucial insights into their evolutionary history. By examining these steps, scientists can identify similarities and differences among different species, which help unravel the evolutionary relationships between them.
One important concept that emerges from embryological studies is the principle of recapitulation, also known as the biogenetic law. This theory, proposed by Ernst Haeckel, suggests that during embryonic development, animals go through stages that resemble the evolutionary history of their ancestors.
For example, the development of the pharyngeal arches in vertebrates provides evidence for the common ancestry between different vertebrate groups. These arches are seen in the early embryonic stages of all vertebrates, including humans, and are reminiscent of the gill slits in fish. In fish, these structures are used for respiration, but in humans, they develop into various structures such as the jaws and inner ear. This similarity in embryonic development suggests a shared ancestry among vertebrates and highlights the evolutionary modification of these structures over time.
Another example is the development of limb buds in tetrapods (four-limbed vertebrates) like amphibians, reptiles, birds, and mammals. In the early stages of development, all tetrapods display limb buds, even though the final form of the limbs differs greatly among these groups. This similarity in embryonic development provides evidence for a common ancestor that possessed limb-like structures, which have undergone subsequent modifications in different lineages.
To analyze how these embryological steps evolved, scientists compare the development of related species, looking for similarities and differences. By comparing these patterns, they can infer evolutionary relationships and hypothesize how different morphological features might have evolved over time.
For example, researchers have uncovered the evolutionary origin of insect wings by studying the development of wings in different orders of insects. It is believed that insect wings evolved from branches of the ancestral appendages that were present in their crustacean ancestors. By examining the genes and developmental pathways associated with wing development, scientists have been able to reconstruct the step-by-step evolutionary changes that led to the emergence of wings in insects.
In summary, the study of embryological steps in invertebrates provides valuable information about their evolutionary history. By recognizing similarities and differences in embryonic development across species, scientists can infer common ancestry, trace the evolution of specific traits, and piece together the story of how different species have diverged and adapted over time.