What is a structure that is similar across species similar in structure but different in function?

Is this evidence of evolution?

Take a close look at this gorilla hand. The similarities to a human hand are remarkable. Comparing anatomy, and characterizing the similarities and differences, provides evidence of evolution.

Just as Darwin did many years ago, today’s scientists study living species to learn about evolution. They compare the anatomy, embryos, and DNA of modern organisms to understand how they evolved.

Comparative embryology is the study of the similarities and differences in the embryos of different species. Similarities in embryos are evidence of common ancestry. All vertebrate embryos, for example, have gill slits and tails. Most vertebrates, except for fish, lose their gill slits by adulthood. Some of them also lose their tail. In humans, the tail is reduced to the tail bone. Thus, similarities organisms share as embryos may be gone by adulthood. This is why it is valuable to compare organisms in the embryonic stage. Seehttp://www.pbs.org/wgbh/evolution/library/04/2/pdf/l_042_03.pdf for additional information and a comparative diagram of human, monkey, pig, chicken and salamander embryos.

Structures like the human tail bone and whale pelvis are called vestigial structures. Evolution has reduced their size because the structures are no longer used. The human appendix is another example of a vestigial structure. It is a tiny remnant of a once-larger organ. In a distant ancestor, it was needed to digest food. It serves no purpose in humans today. Why do you think structures that are no longer used shrink in size? Why might a full-sized, unused structure reduce an organism’s fitness?

In search of the common ancestor of all mammals, University of California Santa Cruz scientist David Haussler is pulling a complete reversal. Instead of studying fossils, he's comparing the genomes of living mammals to construct a map of our common ancestors' DNA. He also specializes in studying the DNA of extinct animals, asking how the DNA has changed over millions of years to create today's species. His technique, referred to as computational genomics, holds promise for providing a better picture of how life evolved. Seehttp://www.kqed.org/quest/televis...lution-machine for more information.

Have you ever thought about how different kinds of animals have body parts that work in similar ways? Like bats and bees? Both creatures have wings - even though their bodies are structured very differently.

The key to understanding these differences lies in knowing what homologous and analogous structures are. In this article, we'll talk about each type of structure and discuss the similarities and differences between them.

What Are Homologous Structures?

Homologous structures are similar structures in related organisms. The most important thing to remember about homologous structures is that they share common ancestry. In other words, only organisms that are somehow related to each other can have homologous structures.

For example, a chimpanzee’s arm and a human’s arm are homologous structures. Both sets of arms have a similar structure and use and chimpanzees and humans share a common ancestor.

What Are Analogous Structures?

Analogous structures are similar structures in unrelated organisms. These structures are similar because they do the same job, not because they share common ancestry.

For example, dolphins and sharks both have fins, even though they aren’t related. Both species developed fins because of how (and where) they live.

What’s the Difference Between Homologous and Analogous Structures?

Homologous and analogous structures have several key differences. Let’s take a look at them:

Homologous Structures Example

A great example of homologous structures are the wings of a bat and the arms of a human. Bats and humans are both mammals, so they share a common ancestry.

Both a bat’s wing and a human’s arm share a similar internal bone structure, even though they look very different externally. The wing and the arm also perform different functions - wings help bats fly, while arms help humans interact with their world in a very different way.

Analogous Structures Example

A great example of analogous structures are a bat’s wing and a bee’s wing. Bats and bees do not share common ancestry, so the structures cannot be homologous.

Both bat wings and bee wings serve a common purpose - helping bats and bees fly! The structures look similar on the outside, too. However, their internal structures are very different - bat wings have a bony structure with muscles, while bee wings are membranous extensions.

Homologous and Analogous Structures - Key Takeaways

Many animals have body parts that look similar, even though they don’t share common functionality. Other animals have body parts that look totally different, but have a shared background. Here’s the difference between homologous and analogous structures:

• Homologous structures are structures that may look or function differently from related organisms.

• Analogous structures are structures that look and function similarly from unrelated organisms.

What’s Next?

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