If two species have similar ancestors và perform similar function then would they be called homologous & convergent evolution(sorry for not able to frame the question properly but hope u got the idea about my doubt)?


Yes, I think... Although if they have similar ancestors and perform similar functions keep in mind that they might be very closely related to each other. Convergent evolution happens if 2 different species evolve to have structure with similar functions rt(correct me if I'm wrong)? Based on that, you have an answer khổng lồ your question. Now I'm not sure I fully understood you question but hopefully this helps

Even though the bat và the eagle evolved independently from different ancestors, at some point in time, they must have shared the same ancestor. In fact, isn't it true that all living organisms have come from a single ancestor. So how vày we know if structures are homologous or analogous?


Just lớn let you know that our "Ancestors" were not even close lớn being ancestors of a bat và dolphin...

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Well is anyone watching this in 2021 and also if a bat has the same bone structure that means our "Ancestors" would have khổng lồ be half dolphin and bat...
- In these pictures, we might look at the fin of the shark, & say they are very similar khổng lồ the flippers of a dolphin. For the dolphins we don't call them as fins, we điện thoại tư vấn them as flippers. They look very similar and they're both used for swimming, so we could say, "Hey, maybe they are very related "to each other." and similarly, if you look at the wings of the bat, let me use a different color, wings of a bat, và the wings of, say, an eagle, again, both are used for flying, they look kind of similar, we might say they are related to each other. But it turns out that in reality, they are not as closely related to each other. And in fact it turns out, surprisingly, it's these two structures are more closely related than these two, or these two. Yeah, this sounds very confusing I know. Và so in this đoạn phim we will explore why certain structures, which might look similar & perform same function, did not necessarily mean that they are related to lớn each other. And on the other hand, we will see that, although some other structures might look very different and perform different functions, they can be related khổng lồ each other. To avoid confusions, let's get rid of this picture and start fresh. So if you take a look at the wings of a bat, the flippers of a dolphin, and our hands, then, although they look very different and they perform different functions, you look carefully, look at their bone structures, you will find the bone structures are very similar. Let me show you. If we zoom in a little bit, let me zoom in to the wings và the flippers và the hand, and here are the bones, look at them. Approximately this is how the bones would be. Look at them, vì chưng you see similarities? lớn make it more clear, let me color them appropriately. So if I color them, now look at these bones carefully. Over here we see one bone, one bone, one bone. And this now is an elbow, our elbow. You get two bones, two bones, two bones. Then we get the wrist bones, wrist bones, wrist bones. Then you get the hand bones over here, five of them, but there are only four here, again five of them. & then we have fingers, finger bones, & finger bones. So, can you see how similar structures they are? The number of bones và the kind of bones are very, very similar to each other. Of course there are, of course, some differences, và they are different species altogether, so some differences are fine, but because of so much similarity, we can say that all these bones evolve from a common ancestor, because of such similarity in the structure, right? So, let me just write that down. Let me zoom out a little bit. Same thing, I zoomed out a little bit. Và now we can say that all of these, all these bones, they have evolved from a common ancestor. Ancestor. So same structure from the common ancestor, performing different functions. Okay? Let me give you a separate example. An extreme example in plants of the same thing. If you were to lớn look at these three plants. This is a pitcher plant, which contains the pitcher, & what it does is, if insects fall into that, it'll close the lid, it'll not allow it to escape và start digesting it. Và this is a Venus flytrap, it's lượt thích a mouth-like thing, so if a fly comes in, it basically closes the mouth & starts digesting it. And this is our cactus, which has a lot of spines. The tongue-like structures, they are called spines, pointy spines. And what's interesting lớn see over here, is that, if you vày careful research, if you vị a careful study on these structures, then we can see that the pitcher of the pitcher plant, the mouth of the Venus flytrap, & the spines, they are all actually highly modified leaves. Now I know it's hard lớn believe how a leaf can modify into these different different things, but it turns out to be true. We'll trust our biologists, okay? On this. So again, what does this mean? Since they are all modified from the leaf itself, from the same leaf itself, we can again say, "Hey, that means these structures "also must have come from a common ancestor." Common ancestor. So with these couple of examples of evolution, what is the common underlying feature you can find out in these examples? What is common in these evolutions? Can you think about it? Well, in both these examples, we see structures that evolve from the same ancestors, but, they kết thúc up performing different functions. See over here, they perform flying & swimming, and our hands can do so many things like, lượt thích I don't know, maybe scratching or climbing. Over here, these are used for catching insects, here also they catch insects, but the spines are used as a protection. So different functions but same ancestry. Such structures, which have different functions, but same ancestry, we gọi them homologous, homo-- logous structures. Or homologous function. I just write homologous, okay? So what's important is that the word "homo", homo means same. Same. Same what? Same ancestors, & that's important. Same ancestor. But they can have different functions. Can have different, different functions. And I say the word, "they can have different functions" is because they can also have same functions. For example, if you compare our hands with the hands of a chimpanzee, okay? They are also homologous, I have not drawn the bone structure, but bone structures would be very similar, và chimpanzee's hands also perform the same function as our hands. So homologous structures can perform same functions, they can also perform different functions, as we see over here. What's important though, is that they have the same ancestry. Homo, same ancestry. On the other hand, if you compare the wings of a bat and an eagle, let's see what we get. You've already seen the wings of the bat, you already saw the bone structure of this. Now let's look at the wing of an eagle. If I zoom in and I look at the bone structure, it looks somewhat like this. So again, we see one bone here, then we have two bones over here, you can see the wrist & a little bit of there as well, and, when it comes lớn fingers & hand, that's where things get a little different. But again, the bone structures are pretty similar. So we can say the forelimbs, forelimbs means, you know, the front limbs, in humans forelimbs are just hands, so the forelimbs we can say, still came from the same ancestry because of the same structure. So we can still say the forelimbs of the bat, and the forelimbs of the eagles, they are homologous, okay. The structures are the same. But let's look at the wings now, that's important. Concentrate on the wing structures. For the bat, look at how the wings are formed. The wings are actually skin. This is the skin of the bat. & the skin of the bat kind of makes a website over here. Right? It's attached lớn the fingertips, can you see that? The skin is stretched over the fingertips, và that's how they have evolved, because of which they can fly. But look at the wings of the eagle. These are not skin, these are feathers, & the feathers are attached khổng lồ the entire arm. They're not web-shaped, lượt thích in the case of the bats, they're not skin, they're not connected to the fingers, like at the bat's. So a completely different structure if you look at the wings, isn't it? So can we say that these wings might have evolved from the same ancestor? I don't think so. Because they have such different structures, we can now say that maybe this wing evolved separately from some ancestor, I'm gonna gọi this as ancestor one, may have evolved from some ancestor, và this wing might have independently evolved from a different ancestor altogether. From a different ancestor altogether. Và so, are the bat wings và eagle wings homologous? The answer is no. Because they have such different structures, they must have evolved from different ancestors. So they are not homologous. So if they are not homologous, what vì chưng we call them? Now before I tell you the name of this, let me show you another example. If you look now at the flipper of a dolphin, and compare that with the fin of a shark, and if you look at the bones of the shark, it might look somewhat lượt thích this. This is an approximate drawing, okay? và if you're wondering why I haven't colored it, mainly because there's nothing similar between them lớn color. Okay? These are made of bones very similar to lớn our hands, these are not even bones. These turn out to lớn be made of cartilages. Very different structure. So, because they have such different structure, we can now again say, "Hey, they must have evolved separately "from different ancestors." So this must have evolved from a different ancestor compared khổng lồ this one. These are separate examples okay, not related to each other. So now, again, if you look at these two, what common feature vày you find in this kind of evolution? In this we see that structures come from different ancestry, but they perform the same functions. Such structures are called analogous structures. Analogous structures, or analogous organs. Okay? What's important over here, they have different ancestors. Different ancestors. Different ancestors. But the important thing, is that they have the same functions, they carry out same functions. Have lớn carry out the same functions. Lượt thích over here, both of them swim. Over here, both of them are used in flying, but underlying structures are super different, therefore, different ancestors. So what is the big picture that I'm trying to lớn paint over here? Well the main thing that I'm trying to lớn tell over here is, when we are starting evolutionary biology, just because we see certain structures which look very different at first & perform different functions, they can still have the underlying same structure và so they could still be related by a common ancestor, homologous structures. And on the other hand, just because we find some structures in some species khổng lồ be very similar và look very similar, and they perform same function, need not necessarily mean that they are related khổng lồ each other. It's totally possible that they evolved independently from separate ancestors altogether. & so these are called analogous structures. Now, one last thing before we wind up, is that if you look at the homologous structures, you see it from one common ancestry, from the same underlying structure, we are getting different functions. So, diversification is happening over here, right? Same structures used for many different things. So homologous structures give us something called divergent evolution. All right? Same structure used for many different things, many different functions. Divergent evolution. On the other hand if you look at analogous structures, they're exact opposite. Two completely different structures from completely different ancestry, have the same functions. Have evolved independently to give us the same functions. So, different structures are coming together, sort of, to give us the same functions, so it's lượt thích converging, this evolution is converging, right? Converging khổng lồ give same functions, so we điện thoại tư vấn this convergent evolution. So analogous structures are are evidence for convergent evolution. All right? Convergent evolution. That's pretty much it.

In What is a Sentence? we saw the minimum requirements for the formation of a sentence. Now we can look in more detail at the four types of sentence structure.


Simple Sentence Structure

A simple sentence consists of one independent clause. (An independent clause contains a subject and verb and expresses a complete thought.)

I lượt thích coffee.Mary likes tea.The earth goes round the sun.Mary did not go to the party.

Compound Sentence Structure

A compound sentence is two (or more) independent clauses joined by a conjunction or semicolon. Each of these clauses could form a sentence alone.

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I like coffee và Mary likes tea.Mary went to work but John went khổng lồ the party.Our car broke down; we came last.

There are seven coordinating conjunctions:

and, but, or, nor, for, yet, so

Complex Sentence Structure

A complex sentence consists of an independent clause plus a dependent clause. (A dependent clause starts with a subordinating conjunction or a relative pronoun, & contains a subject và verb, but does not express a complete thought.)

We missed our plane because we were late.Our dog barks when she hears a noise.He left in a hurry after he got a phone call.Do you know the man who is talking khổng lồ Mary?

Here are some common subordinating conjunctions:

after, although, as, because, before, how, if, once, since, than, that, though, till, until, when, where, whether, while

Here are the five basic relative pronouns:


Compound-Complex Sentence Structure

A compound-complex sentence consists of at least two independent clauses và one or more dependent clauses.


John didn"t come because he was ill so Mary was not happy.He left in a hurry after he got a phone điện thoại tư vấn but he came back five minutes later.

A dependent clause is also called a subordinate clause.

The above sentences are basic examples only. In some cases other arrangements are possible (for example, a dependent clause can come before an independent clause).

Contributor: Josef Essberger

Sentence Structure Quiz
Club :Learn English :Grammar : Sentence Structure

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