Homologous structures a. are structures in two or more...

Homologous structures a. are structures in two or more species that originate as the same structure in a common ancestor. b. $\quad$ are structures that look the same in different species. c. cannot serve different functions in different species. d. $\quad$ must serve different functions in different species.

Homologous structures
a. are structures in two or more species that originate as the same structure in a common ancestor.
b. $\quad$ are structures that look the same in different species.
c. cannot serve different functions in different species.
d. $\quad$ must serve different functions in different species.

Key Concepts

Homologous Structures

Homologous structures are anatomical features in different species that arise from the same structure in a common ancestor. This concept indicates that despite possible differences in function or appearance due to evolutionary divergence, the underlying similarity in structure reflects a shared evolutionary history.

Common Ancestry

Common ancestry is the idea that different species have descended from a shared ancestral organism. It underpins the explanation for homologous structures, as these similar anatomical features are inherited from the common ancestor and then modified by evolutionary processes over time.

Comparative Anatomy

Comparative anatomy is the study of the similarities and differences in the anatomical structures of different species. This field provides evidence for evolution and common ancestry by analyzing homologous structures, which may vary in function but reveal a shared lineage.

Transcript

00:02 So this question is pretty definitional.

00:05 So if you were in a test situation and you didn't know what homologous sorts of structures were, you might be kind of stuck because this is pretty much just asking what this word means.

00:21 So with that, homologous structures, you can think of it as having, there are going to be structures that they share a common ancestor.

00:33 So if we tracked a certain trait that if we had a trait, let's just say it's hand bones.

00:55 So i'm just going to put hands.

01:04 Yeah, hands works.

01:09 So then if we had five different critters, five different or we'll say four different organisms since i'm running out of space, we might be able to look at that trait.

01:21 And it might not look the same in all of the different organisms.

01:27 But there would be some similarities with them.

01:31 So a nice example of where you can see this is in mammal arms and hands.

01:38 So if you compare an example that you might see is a whale flipper versus a mouse hand or mouse arm, i guess i'll say, versus a human hand versus a bat.

02:05 So that's an example that we could see.

02:08 And if we zoomed in on all those and we looked at the skeletal structure of each of these, we would see that the bones are nearly the same.

02:16 The bones have different shapes.

02:18 Think of a whale.

02:19 It's going to be big and flat.

02:21 But on the inside, the bones are still there in the same structure.

02:26 So we can imagine once upon a time we all shared this common ancestor.

02:31 And then as they began to, you know, to go through natural selection in their own habitat.

02:38 So something that's more aquatic and living in water is going to have very different natural selective pressures, pushing it towards a different structure.

02:47 And then as we go up through that they would still have the same bones and things...

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