Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 62 (9057 total)
61 online now:
dwise1, PaulK, Tangle, Theodoric, vimesey (5 members, 56 visitors)
Newest Member: drlove
Post Volume: Total: 889,717 Year: 829/6,534 Month: 829/682 Week: 64/445 Day: 10/10 Hour: 1/8


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Peppered Moths and Natural Selection
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 305 of 350 (670540)
08-16-2012 8:49 AM


It would appear that the peppered moths are a good example of how natural selection (as currently defined) is protected against in the natural world.

Darker and lighter moths are simply varieties in the available DNA pool and other alleles can exhibit recessive or dominant traits as demonstrated in experiments by Mendel.

Recessive traits which are only exhibited when set criteria are met are nevertheless still available in the DNA source. It might appear as though they have been selected against by observers and a good argument for natural selection. However, when the circumstances change and become favourable these traits will be manifested again. Mendels examples include the return of green and wrinkly recessive traits in subsequent generations.

Natural selection, rather than being defined as "survival of the fittest" might be better viewed as "allele domination under significant environmental and sexual selection pressures".


Replies to this message:
 Message 306 by NoNukes, posted 08-16-2012 2:04 PM Big_Al35 has responded
 Message 307 by Dr Adequate, posted 08-16-2012 2:38 PM Big_Al35 has not yet responded
 Message 309 by Percy, posted 08-17-2012 9:33 AM Big_Al35 has responded
 Message 313 by RAZD, posted 08-17-2012 1:11 PM Big_Al35 has not yet responded

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 308 of 350 (670669)
08-17-2012 3:52 AM
Reply to: Message 306 by NoNukes
08-16-2012 2:04 PM


NoNukes writes:

Are you suggesting that individual moths are changing their appearance in response to the environmental changes?

I think your comprehension skills are somewhat lacking. Try re-reading my post.

If instead you are suggesting that the ability to produce a dark (or light colored) moth is present in the population, but is recessive, then you are not expressing an issue with natural selection which is merely a screening process, but with mutation which is a source of diversity.

I have supplied you with two definitions for natural selection. An old darwinian definition "survival of the fittest" and another which I have conjured up myself. I am totally bemused as to how you have chosen to define natural selection, as "screening process" doesn't really tell me anything. Perhaps you would be kind enough to offer your own definition.

And as for mutation, I didn't even mention mutation once in my post. Does mutation have anything to do with this topic?


This message is a reply to:
 Message 306 by NoNukes, posted 08-16-2012 2:04 PM NoNukes has responded

Replies to this message:
 Message 310 by Theodoric, posted 08-17-2012 10:41 AM Big_Al35 has not yet responded
 Message 322 by pandion, posted 08-18-2012 1:48 AM Big_Al35 has responded
 Message 324 by NoNukes, posted 08-18-2012 9:58 AM Big_Al35 has responded

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 311 of 350 (670694)
08-17-2012 11:02 AM
Reply to: Message 309 by Percy
08-17-2012 9:33 AM


Percy writes:

What does it mean to say that natural selection is protected against the natural world?

Populations and species are protected from the harsh dangers of natural selection. Mendels laws of heridity provide a degree of protection. Where we might believe that certain traits have been wiped of the face of the earth through "survival of the fittest", those attributes can live on, hidden and preserved, within the genome. When more favourable circumstances arise, those traits will re-emerge continuing to offer variety where it appeared lost.

Natural selection is more accurately described in the way you just attempted, as varying allele frequencies in a population over time in response to changing environmental pressures.

I am glad that we can "kind of" agree on this more modern definition of natural selection.


This message is a reply to:
 Message 309 by Percy, posted 08-17-2012 9:33 AM Percy has responded

Replies to this message:
 Message 312 by Granny Magda, posted 08-17-2012 11:34 AM Big_Al35 has responded
 Message 317 by Percy, posted 08-17-2012 1:46 PM Big_Al35 has responded

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 314 of 350 (670710)
08-17-2012 1:14 PM
Reply to: Message 312 by Granny Magda
08-17-2012 11:34 AM


Granny Magda writes:

A recessive gene can't "hide" simply by dint of it being recessive. If two carriers of the recessive gene mate and produce offspring, it will be expressed.

Let's use your definition ie "survival of the just good enough". If the environment was so harsh that a particular trait could not even survive long enough to reproduce, then only individuals who are actively expressing that trait would disappear. The unexpressed allele would still linger on in the population at large. These harsh conditions could even continue for thousands or millions of years. In every generation where the allele is expressed, the individual would die.

However, after enough time had passed, circumstances or the environment might change. Individuals who are now expressing the gene may actually survive or even flourish. The example that I am thinking of is the peppered moths.


This message is a reply to:
 Message 312 by Granny Magda, posted 08-17-2012 11:34 AM Granny Magda has responded

Replies to this message:
 Message 315 by RAZD, posted 08-17-2012 1:27 PM Big_Al35 has responded
 Message 318 by Granny Magda, posted 08-17-2012 2:03 PM Big_Al35 has not yet responded

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 316 of 350 (670712)
08-17-2012 1:43 PM
Reply to: Message 315 by RAZD
08-17-2012 1:27 PM


Re: Sickle Cell mutation and Natural Selection -- new topic?
would you like to start a new thread on tht topic (Sickle Cell mutation and Natural Selection)?

Sorry, this would not be my area of expertise. I will leave that to someone who has an interest in sickle cell, or mutation.


This message is a reply to:
 Message 315 by RAZD, posted 08-17-2012 1:27 PM RAZD has acknowledged this reply

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 319 of 350 (670717)
08-17-2012 2:20 PM
Reply to: Message 317 by Percy
08-17-2012 1:46 PM


Percy writes:

I think what you're really trying to say is that detrimental alleles that are recessive can much more easily escape selective pressures than detrimental alleles that are dominant. I don't think anyone would argue with this.

Not exactly, some alleles can be both dominant and recessive. Let's say we had alleles A, B and C. A might be dominant to B but recessive to C. B is recessive to A but dominant to C. And C is dominant to A but recessive to B. This might allow A, B and C to be bulletproof from being selected out of the gene pool.


This message is a reply to:
 Message 317 by Percy, posted 08-17-2012 1:46 PM Percy has responded

Replies to this message:
 Message 320 by Percy, posted 08-17-2012 6:03 PM Big_Al35 has responded

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 325 of 350 (670802)
08-19-2012 10:02 AM
Reply to: Message 322 by pandion
08-18-2012 1:48 AM


pandion writes:

Natural selection is the differential reproductive success of organisms that possess benificial genetic traits (that lend a reproductive advantage).

Classic evolutionary tautology. The reproductive success of organisms that have traits which promote reproductive success. The reason this is nonsense is because it contains no information. Reproductive success (not quantified) used twice and traits (quantified only by reproductive success which remains undefined).

Sorry but your definition is garbage.


This message is a reply to:
 Message 322 by pandion, posted 08-18-2012 1:48 AM pandion has responded

Replies to this message:
 Message 328 by Dr Adequate, posted 08-19-2012 10:55 AM Big_Al35 has not yet responded
 Message 329 by pandion, posted 08-19-2012 12:57 PM Big_Al35 has not yet responded
 Message 332 by crashfrog, posted 08-19-2012 2:58 PM Big_Al35 has not yet responded

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 326 of 350 (670803)
08-19-2012 10:05 AM
Reply to: Message 324 by NoNukes
08-18-2012 9:58 AM


Re: Plonk
NoNukes writes:

I asked questions because I hoped you'd make your position more clear. Instead you elected to deal out insults to a complete stranger.

Ok...I might have been a little harsh with you but no harsher than others have been with me. I suggest you grow a pair.


This message is a reply to:
 Message 324 by NoNukes, posted 08-18-2012 9:58 AM NoNukes has not yet responded

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 327 of 350 (670804)
08-19-2012 10:22 AM
Reply to: Message 320 by Percy
08-17-2012 6:03 PM


Percy writes:

So what about your main point? Everyone who responded is still completely puzzled as to why you're using a prime example of natural selection at work to argue that some alleles are protected against natural selection.

I think everyone accepts that natural selection occurs but it's the nature of natural selection and the sequence of events that we are discussing here. I have used the example of the peppered moths. Two or more types of moth (namely dark and light existed prior to the event ie industrialization) and two or more types existed after the event. It was simply a case of which type of moth flourished when.
Therefore I wouldn't view this is as an example of evolution. Others might disagree.

You and some others here have introduced mutation into the equation. This may account for genuine micro-evolution but has nothing to do with the example I was discussing.


This message is a reply to:
 Message 320 by Percy, posted 08-17-2012 6:03 PM Percy has responded

Replies to this message:
 Message 331 by RAZD, posted 08-19-2012 2:19 PM Big_Al35 has not yet responded
 Message 336 by Percy, posted 08-20-2012 8:12 AM Big_Al35 has not yet responded

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 333 of 350 (670829)
08-20-2012 4:21 AM
Reply to: Message 320 by Percy
08-17-2012 6:03 PM


Percy writes:

You are correct that some parts of the genetic code *are* protected against natural selection (but not against mutation), but recessive alleles are not an example of this. A better example would be disabled genes that cannot be selected for or against because are not expressed, but the disabled gene is understood to be yet another mechanism of evolution, through further mutation and eventual re-enabling.

Actually, now that we covered the fact that some traits are offered a degree of protection from extinction by being recessive, maybe someone ought to cover why large chunks of dna, particularly the genes, are largely protected from mutation events.


This message is a reply to:
 Message 320 by Percy, posted 08-17-2012 6:03 PM Percy has responded

Replies to this message:
 Message 334 by Dr Adequate, posted 08-20-2012 5:11 AM Big_Al35 has not yet responded
 Message 335 by RAZD, posted 08-20-2012 6:44 AM Big_Al35 has not yet responded
 Message 337 by Percy, posted 08-20-2012 8:16 AM Big_Al35 has not yet responded

  
Big_Al35
Member
Posts: 389
Joined: 06-02-2010


Message 343 of 350 (670958)
08-21-2012 10:30 AM


Percy writes:

Where are you going with this, Al? What are you trying to say about the peppered moth example of natural selection?

I think everything that needed to be said has been said. Glad to see this has been thrown into summary mode so we can all move on.


  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2022