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Natural selection in peppered moths

The video discusses natural selection, illustrated by the peppered moth's color changes in London. Darker moths became predominant during the Industrial Revolution due to pollution, providing better camouflage against predators. With recent environmental improvements, lighter moths are reemerging. This demonstrates how environmental shifts can influence the prevalence of certain traits in a species over time. Created by Sal Khan.

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  • blobby blue style avatar for user SuperSwetter
    Can the dark allele which may be recessive change into a dominant allele due to natural selection?
    (5 votes)
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    • piceratops ultimate style avatar for user FrozenPhoenix45
      First off, in the peppered moth example the dark allele is dominant. Just wanted to clear that up before going further.

      Usually, I would say no, the recessive allele cannot become the dominant one. It may seem so due to natural selection. If that dominant phenotype is detrimental to the organism's existence, it is less likely to survive long enough to reproduce. Then all the organisms with the recessive phenotype (and therefore only recessive alleles) will reproduce and pass on those recessive alleles, while much fewer of the dominant alleles pass on. This would make it seem like the recessive allele is the dominant one simply because more of the recessive phenotype survives.

      However, in a few extremely rare occasions, I believe there have been cases where a genetic mutation made the recessive allele dominant over the dominant one. However, this is localized to a single organism (the one with the mutation) and is not "natural" at all, due to mutation.

      Does that help?
      (14 votes)
  • winston default style avatar for user JD lG
    think of natural selection like a salad bar, you can put as many ingridients in your plate as you like but if there is no broccoli then you will never get no broccoli! In the same way natural selection can only select from wat is already in existence. So you have to start with a huge salad bar it is possible to get a huge variety of items. And so there must have been a creator or god! But evolutionists say that there was nothing just a void and then there was a explosion but that explosion needed plenty of energy and according to the laws of physics "Energy can not be created nor destroyed".
    Please take this into consideration. Thank you.
    (6 votes)
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    • starky ultimate style avatar for user 64
      This is making my brain rot.
      The big bang is a topic for a later date, lets just focus on Natural Selection.
      An organisms energy is going to whatever organism consumes or decomposes it, so its not destroyed if that's what you meant.
      "but if there is no broccoli then you will never get no broccoli"

      So you will always get broccoli if there's no broccoli, that s a double negative so it inverts ( its also not grammatical, use better syntax please ).

      "In the same way natural selection can only select from wat ( you mean 'what' right? I sure trust this guy. ) is already in existence. "

      Mutations occur which can make new traits, if its favorable to natural selection and happens enough it will become a common trait.
      You can't pick what traits you get, I may hate my freckles but I can't just ask god to remove them from me, and Parents don't pick what traits their child gets either.
      Call me a satanic, call me the devil. See if I care about your opinion.
      Let's see if you care about mine.
      (1 vote)
  • blobby green style avatar for user juan lara
    what is soot?
    (2 votes)
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  • duskpin ultimate style avatar for user StrangeKiller
    is pollution that bad?
    (3 votes)
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  • aqualine tree style avatar for user ✨Aysha✨
    What is soot?
    (2 votes)
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    • hopper cool style avatar for user Deni
      Soot is a byproduct of the incomplete combustion of organic (i.e., carbon-containing) materials such as wood, fuel oil, plastics, and household waste. The fine black or brown powder may contain a number of carcinogens such as arsenic, cadmium, and chromium.
      (5 votes)
  • blobby green style avatar for user coolkoo888
    hi, hows your day?
    (4 votes)
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  • starky seedling style avatar for user jonhill
    Can i also change color if i lock myself in a blue room?
    (3 votes)
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  • blobby green style avatar for user TabbyCat
    Does Sal believe in God
    (3 votes)
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  • blobby green style avatar for user OVEYMARM
    What are butterflies and moths?
    How many kinds of butterflies and moths exist?
    What is the difference between butterflies and moths?
    Are there endangered butterflies and moths?
    Are butterflies poisonous?
    Which butterflies are poisonous?
    Why are butterflies and moths such good insects?
    How did butterflies get their English name?
    How do you say "butterfly" in other languages?
    How do I identify a caterpillar?
    How much do butterflies weigh?
    How long do butterflies live?
    Do butterflies have brains and hearts?
    Are butterflies and moths pollinators?
    (1 vote)
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    • piceratops ultimate style avatar for user lauren
      Great questions!

      *What are butterflies and moths?*
      Butterflies and moths are insects that belong to the order Lepidoptera. They are known for their beautiful, often colorful, wings and their unique life cycle that includes stages of egg, larva (caterpillar), pupa (chrysalis), and adult.

      *How many kinds of butterflies and moths exist?*
      There are about 20,000 species of butterflies and 160,000 species of moths.

      *What is the difference between butterflies and moths?*
      There are several differences, including their behavior, wing structure, and body shape. For example, butterflies are usually active during the day, while most moths are nocturnal.

      *Are there endangered butterflies and moths?*
      Yes, there are several species of butterflies and moths that are endangered due to habitat loss, climate change, and other factors.

      *Are butterflies poisonous?*
      Some butterflies are indeed poisonous, or more accurately, toxic. They accumulate toxins from the plants their caterpillar eats.

      *Which butterflies are poisonous?*
      One example is the Monarch butterfly, which is toxic due to the milkweed its caterpillars consume.

      *Why are butterflies and moths such good insects?*
      They play crucial roles in ecosystems, such as pollination and serving as a food source for other animals. They’re also indicators of a healthy environment and ecosystem.

      *How did butterflies get their English name?*
      The origin of the word “butterfly” isn’t completely clear, but one theory suggests that it comes from the yellow color of many species’ wings, which could be likened to butter.

      *How do you say “butterfly in other languages?*
      In Spanish it’s “mariposa”, in French, it’s “papillion”, and in Italian, it’s “farfalla”.

      *How do I identify a caterpillar?*
      Identifying a caterpillar can be difficult as there are many species, and they can look different at various stages. A good start is to note its color, size, shape, and any distinctive features like hairs or spikes. Then, you can compare it to a picture in a field guide or online resource.

      *How much do butterflies weigh?*
      Butterflies are very lightweight. On average, they weigh around 0.5 to 2 grams.

      *How long do butterflies live?*
      The lifespan of a butterfly varies greatly depending on the species. Some live only a week, while others, like the Monarch, can live up to 9 months.

      *Do butterflies have brains and hearts?*
      Yes, butterflies do have brains and a heart. Their brain controls behavior, while their heart (located along the back of the insect) pumps hemolymph (similar to blood in mammals) throughout their body.

      *Are butterflies and moths pollinators?*
      Yes, butterflies and moths play a significant role in pollination. As the travel from flower to flower to feed on nectar, they pick up pollen on their bodies and transfer it to other flowers, helping plants reproduce.
      (4 votes)
  • duskpin ultimate style avatar for user Power
    I speek for thee treees
    (3 votes)
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Video transcript

- [Narrator] You might be familiar with the idea of evolution, that species change over time. And you can see that if you look at old bones, old fossils, how they change through the fossil record. But the obvious question is, how do these species actually do that? What is the mechanism? Well, one of the major mechanisms is natural selection. So natural selection is all based on at any given point in time, there is variation in a species. There are different traits that are expressed in different ways. And many times, a lot of those variations are fine, but then you can have environmental factors which make some of those traits more favorable than others. And if those traits are more favorable to be able to survive, to be able to get food, or to be able to reproduce, well then the genes that code for those traits are more likely to be passed on generation after generation. And to make this very tangible, I will give you the example of the peppered moth, which is probably the most common example when people show evidence of natural selection. If you were to go to the mid 1800s in London, most of the peppered moths were the white peppered moths. There were very few black peppered moths, but there was variation. There would be some lighter ones, there would be some darker ones, and in-between. Now what's interesting is between the mid 1800s and the late 1800s, you have the industrial revolution in London really hitting full gear. And so there was a lot of pollution in the air. And so a lot of the surfaces that the moths might rest on like trees, or the wall of a building, became darker and darker. So as where these moths could rest became darker and darker, what do you think might have happened? Well, some of you might guess. In this different environment now, as the environment has gradually changed, all of a sudden having the traits that make you darker will be more favorable than they were even 30 or 40 or 50 years ago. And the white trait, which might've been okay in the mid 1800s, now all of a sudden makes these moths very obvious to see. So if there was a bird that was looking for lunch, it'd be very easy to pick off the white moths versus the black moths. And what we saw is actually by the 1900s, most of the peppered moths in London were now darker in color. And so what you had happening generation after generation is variation in the moth color. But as the background environment became darker, the ones that were white colored were easier to pick off by predators. And if they're picked off by a predator, they're definitely not reproducing and passing on their genes. And then the ones that were able to survive and pass on their genes were the darker moths. Now it's been interesting over the last 50 or so years as environmental regulations have gone into effect, and the air has started to clean up in places like London, you're seeing a return of the white peppered moth. Because once again, the surfaces are no longer covered with soot, and so the variants that are lighter in color now have a decent chance of not being spotted. And if anything, now the darker ones might have a better chance of being spotted in this cleaner environment.