Weird question about the Theory of Evolution

[USincognito]

We only have two species of egg-laying mammals left: the platypus and the echidna.

Echidnas are a family with 2 extant genera and 6 extant species.

 

[driewerf]

I have studied

Congratulations! The more we study, the better. Any subject you study (biology, astronomy, a foreign language, history) is a personal improvement.

evolution some

Congratulations again, for your excellent choice! The ToE is a fascinating subject.

but I really don't understand it.

That doesn't matter. All beginning is difficult. With the help of many you will start understanding it.

This is gonna sound odd, but I don't see how reproduction evolved.

Now here things go wrong. You admit that you don't understand the ToE, yet you start aking questions about a highly technical aspect. I would suggest to grasp the basics first (and grasp them firmly) and tackle the difficult ones later.

The theory of evolution says that everything happened gradually.
[...]

"Everything" might be a little too much, but "yes"

My problem is that I don't see how groups of a few cells started laying eggs.

Did you say "gradually" in the previous sentence? Do you consider the jump from "a group of cells" to egg laying animals "gradual"? Consider that for laying eggs an organism needs ovaries, an oviduct etc, that are quite complicated organs. I suggest that you reaaly study the basics of evolution. Really.

I also have a hard time understanding how a transition from birds and fish (who lay eggs) into mammals (who have sexual intercourse) could have happened gradually.

I understand that. Especially since fish and birds reproduce sexually too. And since mammals don't descend from birds. Here I would suggest to drop the subject of evolution altogether, and start with basic biology, first. And I mean really basic biology.

I especially have trouble imagining how the male/female division evolved. It doesn't make sense.

I can understand that.

Do you have any ideas? Thanks in advance!

I made some suggestions above.

 

[Loudmouth]

Echidnas are a family with 2 extant genera and 6 extant species.

Oh, my mistake. Glad to see that there are more than I thought.

 

[Naraoia]

Don't worry, I believe Christians should study evolution. God doesn't tell us how He created the Earth. I also think people should know what they don't believe, in addition to what they do!

Yes, and most importantly, they should know why. I'm a big fan of understanding my own beliefs.

And I would like to learn from you, you are good at explaining.

I do my best

Thank you for your post, it was very understandable and informative. The part that is probably hardest for me is imagining an organism going from laying eggs to internally growing their own. for example, I think a bird that suddenly tried to grow all it's eggs inside of it would die pretty quickly, as it might not be able to fly hunt defend itself, etc.

Some birds do actually do that! Remember that an egg contains pretty much everything (aside from air) that a baby bird needs to develop to hatching. So I don't think eggs would actually get any heavier after they are laid. Many birds stagger their egg laying over several days, but not all do. (Case in point: petrels, which of course fly, but still manage to lay scarily enormous eggs for their size.)

What you may find even more interesting are the tunicates. These are basal urochordates that split off early in vertebrate evolution. They are very simple vertebrates without a hard endoskeleton and many of the features you are familiar with in other vertebrate species. What we find is that these very simple vertebrates are hermaphroditic (i.e. they have both male and female gonads in the same individual).

Tunicate - Wikipedia, the free encyclopedia

They are not vertebrates, they are the living sister group of vertebrates

Being hermaphrodites is probably the least weird thing about tunicates.

 

[Loudmouth]

They are not vertebrates, they are the living sister group of vertebrates

They are chordates, which I consider to be vertebrates. Tomato . . . tomahto.

 

[Naraoia]

They are chordates, which I consider to be vertebrates. Tomato . . . tomahto.

Sorry, I'm like the grammar Nazi of systematics. I can't help it.

 

[JonasZ]

How did organisms that laid eggs turn into mammals? Can anyone shed some light on that?

There were mammals around at the time of the reptiles or dinosaurs. But the moist warm climate favored the dinosaurs. When the climate changed then the mammals became favored and they began to multiply. Amphibians like turtles and alligators were also able to survive the change.

 

[sfs]

Oh, my mistake. Glad to see that there are more than I thought.

There may not be for much longer. According to Wikipedia, there are only four extant species -- and three of the four are listed as "critically endangered".

 

[Naraoia]

There were mammals around at the time of the reptiles or dinosaurs. But the moist warm climate favored the dinosaurs. When the climate changed then the mammals became favored and they began to multiply.

Sorry, but where does all this nonsense about climate change come from?

Amphibians like turtles and alligators were also able to survive the change.

Never mind that neither turtles nor alligators are amphibians.

 

[CabVet]

I have studied evolution some, but I really don't understand it.

This is gonna sound odd, but I don't see how reproduction evolved.

You have to be very clear here, are you asking about reproduction or sex? These are two different things, and reproduction is very easy to explain. Sex is a bit more complicated.

The theory of evolution says that everything happened gradually. My problem is that I don't see how groups of a few cells started laying eggs.

Cells don't lay eggs.

I also have a hard time understanding how a transition from birds and fish (who lay eggs) into mammals (who have sexual intercourse) could have happened gradually.

You seem to be lacking a basic understanding of biology (either that or you are communicating your ideas poorly). Many fish have sexual intercourse (all sharks for example), and all birds do too. Some mammals lay eggs. I am not quite sure if I understand the question.

I especially have trouble imagining how the male/female division evolved. It doesn't make sense. Do you have any ideas? Thanks in advance!

Now you are talking about the evolution of sex, not reproduction. Well, for one, sexual reproduction generates much more opportunities for diversification than asexual reproduction. It introduces a lot more genetic variation in populations. The list goes one. Here is some interesting reading if you are up for it.

 

[Styx87]

Sexual separation may have it's origins in Flatworms. Largely considered to be the crown species for many extant genera as they are considered to be among the first chordates and among the first to adapt bilateral symmetry. What's interesting is that while they do preform a "mating ritual" (called Penis Fencing (I kid you not!)) there seems to be no division in the sexes. Both partners are both male and female...

It may be that it's more beneficial for one to produce the sperm and one to produce the eggs rather than both as more energy would be required to preform both functions which would explain why there's a division in the sexes as there is today in most terrestrial species although many can still change sex at any time (something seen most commonly in amphibians, mainly frogs).

Flatworms Penis Fencing - YouTube

 

[Wiccan_Child]

(I sh*t you not!)http://www.youtube.com/watch?v=S0c3NyupRuY

FYI, circumventing the forum's censor is against the rules.

 

[Styx87]

Gotcha! Thanks . ^^

 

[Naraoia]

Sexual separation may have it's origins in Flatworms.

What do you mean by sexual separation?

Largely considered to be the crown species for many extant genera...

As a biologist, this makes absolutely no sense to me. What's a crown species? Do you mean crown group? But that still makes no sense. Crown groups are all surviving members of a lineage.

BTW, flatworms were once considered to be "primitive" bilaterians, but that hypothesis is generally out of favour now.

as they are considered to be among the first chordates...

They have nothing to do with chordates. Chordates include vertebrates like ourselves, plus sea squirts and their kin, and these guys. Flatworms are in an entirely different part of the animal tree and possess none of the defining features of chordates.

...and among the first to adapt bilateral symmetry.

Again, that's an outdated idea (unless you are thinking of acoels, which - well, we're still not sure what they are, but one thing they almost certainly aren't is flatworms). Also, even if they were the furthest possible bilaterians you could find from a human vantage point, that doesn't mean "they" did anything first. That is a common misunderstanding of how phylogenies work. (It is also a giant pet peeve of mine.) The animal that first adopted bilateral symmetry would have been a common ancestor of flatworms and us. (Unless we come from flatworms, which to the best of anyone's knowledge isn't the case)

What's interesting is that while they do preform a "mating ritual" (called Penis Fencing (I kid you not!)) there seems to be no division in the sexes. Both partners are both male and female... It may be that it's more beneficial for one to produce the sperm and one to produce the eggs rather than both as more energy would be required to preform both functions which would explain why there's a division in the sexes as there is today in most terrestrial species although many can still change sex at any time (something seen most commonly in amphibians, mainly frogs).

Frogs can change sex? Which ones?

 

[keith99]

Since plants have gender as well, the advent of sex started a very, very long time ago.

Actually the vast majority of plants have only one gender, having both the male (pollen producing) parts and the female.

Of plants I am familiar with the majority of those called male or female actually reflect a failure in some to produce one or the other.

The relative fertility of some plants, like apples, when pollinated by a different variety as opposed to self pollination shows an interesting case of a balance between options when it comes to survival.

 

[Loudmouth]

Just for clarity, the correct terms are dioecious and monoecious which in Greek are two or one household. Humans are dioecious having two households or genders while plants and other species are monoecious having just one household or gender.

 

[SkyWriting]

So you aren't really interested in learning.

You need to realize that the reason we know anything at all is because there are those who are passionate about science and have devoted their careers to studying the very questions you ask, so that you might learn and understand the processes. And to claim that it takes more faith to believe something, because you don't understand it, is the argument from ignorance. Might it be more wise to claim that this information is difficult to understand, but that you'll devote the amount of time it takes to really understand the details? If you're being honest here, you would have to admit that your understanding of science is skewed by your religious dogma, and that there would be no amount of facts and evidence to sway you.

After you admit that your views about her dogma have a strangle hold on your opinions,
then we can consider your view. You have to admit that your just as likely to be wrong first.

 

[SkyWriting]

These links may shed some light on this topic. It's by no means simple or easy to understand!

No. You fail to understand that your links say that there is no clear answer. First sentence: "The evolution of sexual reproduction is described by several competing scientific hypotheses."

What this says is that there are several non-compatible theories, no clear answer how it might have happened.
Isn't that interesting? All this "stuff" to see in our world and no clear answer on how sex could have evolved? We have plenty of sexual and non-sexual things to look at but no real clues on how to get from one to the other.
Life is exactly the same. Not one thing to observe of non-life to life.

 

[sublime911]

A population of Chlorella vulgaris (a single-celled algae) over the course of a weekend obtained a mutation to the genes that transcribe for ligase proteins; due to environmental forcing (IE an infestation of predatory paramecium) the population became fixated with the mutation (IE all members of the population that survived the weekend was the ones with the ligase mutations). This was due to the fact that the mutated ligase protein failed to allow the sister cells to fully break away. This resulted in a colonial form that was too big for the paramecium to swallow.

So a single, random novel mutation, derived from a population without the mutation caused a major morphological change, that was acted upon by selection resulting in massive change in the population demographics.

I mean we have also a population of cervical cells evolving numerous mutations that resulted in them seceding from the humans they were derived from. Due to environmental forcing they have become independent single-celled organisms living as laboratory pests. The cells genomes aren't even recognizable as human anymore. You can't contest the morphological change (multicellular to unicellular), or the fact that they had a significant change in population demographics.

 

[Styx87]

What do you mean by sexual separation?

As in separation between male and female... didn't know how else to say it.

As a biologist, this makes absolutely no sense to me. What's a crown species? Do you mean crown group? But that still makes no sense. Crown groups are all surviving members of a lineage.

Yeah wrong term, I know. I understand that while Flatworms are primitive, they've evolved just as much as everything else and are far removed from their ancestors.

It is true however that scientist look to them and many other species with no clear gender to try and understand why there's a separation in the first place.

BTW, flatworms were once considered to be "primitive" bilaterians, but that hypothesis is generally out of favour now.

... news to me... but then I haven't really been looking into it for a while so I'm a bit out of the loop on that one.

They have nothing to do with chordates. Chordates include vertebrates like ourselves, plus sea squirts and their kin, and these guys. Flatworms are in an entirely different part of the animal tree and possess none of the defining features of chordates.

Didn't chordates come before vertebrates and are considered to be animals that possess a single nerve chord generally running the length of their body?

*DERP* You're right... they're not chordates... not even close. I was just completely mistaken on that one!

Again, that's an outdated idea (unless you are thinking of acoels, which - well, we're still not sure what they are, but one thing they almost certainly aren't is flatworms). Also, even if they were the furthest possible bilaterians you could find from a human vantage point, that doesn't mean "they" did anything first. That is a common misunderstanding of how phylogenies work. (It is also a giant pet peeve of mine.) The animal that first adopted bilateral symmetry would have been a common ancestor of flatworms and us. (Unless we come from flatworms, which to the best of anyone's knowledge isn't the case)

No, yeah, I get that. Like when people say we evolved from Chimps. Like no, we didn't... yes we have a common ancestor but neither one came from the other and since then we've both done the same amount of evolving.

Frogs can change sex? Which ones?

Reed Frogs and Wrinkled Frogs do this. That's all I know... so yeah, it's more common in fish.