Natural Selection - Crash Course Biology #14
ฝัง
- เผยแพร่เมื่อ 24 มิ.ย. 2024
- Hank guides us through the process of natural selection, the key mechanism of evolution.
Table of Contents:
1) Natural Selection 1:27
2) Adaptation 2:56
3) Fitness 3:36
4) Four Principals 3:54
a. Variations 4:01
b. Heritability 4:17
c. "The Struggle for Existence" 4:25
d. Survival and Reproductive Rates 5:00
5) Biolography 5:59
6) Modes of Selection 7:40
a. Directional Selection 8:17
b. Stabilizing Selection 8:56
c. Disruptive Selection 9:27
7) Sexual Selection 10:22
8) Artificial Selection 11:24
References:
curiosity.discovery.com/topic/...
www.globalchange.umich.edu/glo...
blogs.scientificamerican.com/o...
www.aibs.org/bioscience-press-...
faculty.clintoncc.suny.edu/fac...
www.irac-online.org/about/resi...
www.pbs.org/wgbh/evolution/lib...
evolution.berkeley.edu/evolibr...
This video uses the following sounds from Freesound.org:
"20071104.forest.04.binaural.mp3" by dobroide
"ForestBirds.wav" by HerbertBoland
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One way to understand Evolution is to first understand “Artificial Selection”. Wolves and Dogs are descended from common ancestors (which looked more like modern wolfs than dogs). Over many generations, Humans selected the “favourable” traits (e.g., long shiny fur, or stocky legs etc) to produce the many different types / breeds of modern dogs that we have today. The keyword here is “over many generations”. There are modern dogs that, of course, are still very much wolve-like in appearance (e.g., Huskies, German Shepherd etc). Some dog breeds are much less wolf-like in appearance (Chihuahua, Shih Tzu etc) as they have been artificially selected for their small size and “cute” traits. So why is it known as artificial selection? This is because the Human (the dog breeders) are the ones determining which individual dogs they would prefer to produce offsprings, thereby continuing the genes they would like to retain. Prior to this, it is also important to understand the idea of Variation. This means that in a litter of puppies, not every puppy is physically identical (even though they may look identical to the untrained eyes). Some puppies have slightly longer legs, some shorter legs. Very small differences, but, yes, the differences are there. It is due to this physical variations that the breeders (humans) select which dogs possess the traits he wants, thus the term “Artificial Selection”. This Selection process is repeated over many generations and the result is the modern dog breeds we have today.
Once we understood Artificial Selection, it will be easy to understand Natural Selection. In Natural Selection, the environment aka Mother Nature (instead of Human) is the factor deciding which traits survive through the generations. How? One example is Food Source. Many species of birds have developed the ability to swim to obtain their food (Adaptability). One pre-requisite of aquatic birds is having water-proof feathers. In this case, this is the “Favourable Trait”. One group of birds may live nearer to the seasides and Individual birds with better waterproof feathers is seen by Mother Nature as a “favourable trait”. And so individual birds with this trait has a much higher chance of survival and passing on this gene to the next generations. Birds with “less waterproof” feathers may probably not even live to adulthood as they had difficulties obtaining their food (in the sea), resulting in their genes being eliminated from this group of birds. Using an analogy, you may think of this process as a kind of filtration process, where only the finest particles is able to pass through the fine filter. This is Adaptation, and it has to be highlighted that Adaptation takes place over many, many, many generations. Physical Adaptations (e.g., change in body shapes) DO NOT take place in just one generation. In other words, an individual animal will not change its form physically to obtain that trait in its lifetime, unless it’s metamorphosis which is a totally different thing.
We also observed this in rabbits living in deserts and rabbits living in cold countries. The long ears in rabbits act as effective heat radiators. This enables the rabbits to lose body heat efficiently, just as how humans lose heat efficiently by sweating. The rabbits living in deserts adapted (over many generations) to the environment by developing very long and erect ears for highly efficient lowering of their body temperature. But rabbits living in cold countries tends to have shorter ears (some even have lop ears). Shorter ears is the “favourable trait” here as it enables them to lose less body heat. All animals (and yes, that includes Humans) are still in the midst of Evolution. If Evolution is constantly ongoing, why can’t we see it happening? We need to understand that Evolution is a very, very slow on-going process. Evolution will never be “complete”, as change is the only constant. If Evolution is true, why are there no animals that are “neither here nor there” (i.e., in-between two species)? We need to remember humans are the ones who gave distinct names to different distinct species of animals in the first place. Let us look at the Seals / Walruses. Their ancestors are land animals, but their body shapes (flippers and hydrodynamic bodies) are hard evidence that they are in the midst of “transition” from land animals to aquatic animals, as their main source of food is in the sea. Of course, we cannot see an appreciable change in their appearances in our lifetime, as the change is happening far too slowly over many generations. So presently, we can only imagine the current physical appearances of Seals / Walruses as being “frozen-in-time”, as with the rest of the millions of species of animals currently living on this planet Earth. And do appreciate their beauty in their current physical form (and the diversity of the Tree of Life), as they will never be the same again one million years from now.
Anyone Binge-watching the bio videos the day before your exam?
+Kloud Chulikavit me
me
haha Im watching them the same morning as my biology AS exam 😂
+Truewildspirit There's no natural selection in Unit 1!
+Zak Zoka I do Aqa and anything could be on either of the exams
4:39 " This leads to what Darwin called 'the struggle for existence' "
Did you mean: my life
+
-
TRue
same
schmood
So we can all agree that youtube teaches better than school? Only 2 weeks I've been studying here, and I already learned almost half a semester of this year.
Could you have a test at the end of videos as an option maybe? would help people study better. Just as an option
www.khanacademy.org/science/biology/her/evolution-and-natural-selection/e/natural-selection-and-darwin
KB Miller ya
NotYourAverageJesusFreak it's not possible to get an 80% on that test, you probably got a 75%
Easy Hundo, lets goooo baby @@freakypeep727
I got 100% it was literally common sense
Study? No I'm gonna watch crash course videos and hope for the best!
+sasha paul this is what i have been doing whole day knowing the fact that i got an exam tomorrow.
+Salwa Chy How did it go?
sasha paul sadly he failed.Fact for the reason he never responded.
How did that go?
Who else is cramming for a bio final or sat
Basically yeah
here here tomorrow
yup
goodluck
julianna weil 👋👋
julianna weil AP test so kind of yes
I swear, this dude never blinks????
He has glasses so he probably doesn't need to blink...
Maybe at 1:11??
Maybe he just has extra moist eyes so he doesn't need to?
He blinks at the end when he talks about the dogs lol
+Googelplus Sucksys Do... you know how eyes function?
why dont colleges just send you to this channel and save us hours of useless lectures
Seriously i think some college classes should just be at home without instructors. I always learn much more from the textbook or through youtube videos. Not necessarily because they're bad teachers, but I just learn better that way instead of hearing someone lecture.
brandon2932 same here idk what it about that but sometimes i would rather just learn it on my own
because that wouldn't make them any money.
spinct83 Truer words have never been spoken.
ive just been given this video as a homework so nice
I have to say, after finding this chanel I've been able to understand my biology class a lot better. This channel is very helpful.
I KNEW IT I KNEW THAT YOU'D BRING UP THE PEPPERED MOTHS
EyeOfTheLauren and Daphnia come up in our course too! although for Caffeine stimulation
#IBbiology
+EyeOfTheLauren Haha same here!! :D Got a test tomorrow...._.
+EyeOfTheLauren ayyyyyyyyyy IB
Me too
nobody:
him: I'm human but let's just pretend i'm a m o t h
You guys are saving my English major butt from failing my one Bio class... THANK YOU!!!
This is one of the only reasons why i am passing Biology!!!! Thank you soooooo much
I can't believe that the video released 8 years ago 👀
Thank you for your videos. I wish all my science teacher were like you :)
You saved me I have such a better understanding about this unit. I wish you
were my biology teacher.
The explanation in the first minute almost exactly explains why humans evolved in Africa to have dark brown/black skin and why less pigmented humans went else where. The less pigmented humans where harassed and eaten by birds because they were more visible to the birds, and the darker humans where not as easily seen.
Feed the troolll!!
***** sorry, my joke was apparently, not apparent.
RETiredGM i got it, industrial melanism. but moth of your facts are wrong
its true though its just their skin evolved by how it affects the sun for example, pale blonde hair absorbs more vitamin c
@@nmarbletoe8210 im moth so i must like lamp
Thank you, thank you, thank you, thank you, thank you. I just started Biology and I'm feeling overwhelmed. My notes + your crash courses make it all sink in! I may stand a chance!
"The Hungry Birds of London" is a GREAT band name
you save my ass every time i have a biology exam. thanks buddy.
This is all wrong
The answer to life
the universe
and everything is
42
Truth.
Ah, but the important part is the question.
HA HA He's right 42 is the answer I saw it on my Video The Hitchhiker's Guide to the Galaxy YAY! *I LOVE THAT VID. I have it on VCR cassette tape(;)
M = 13
A = 1
T = 20
H = 8
13 + 1 + 20 + 8 = 42
Conclusion = maths is the meaning of life
please have 42 likes!!!!!!!!!!!
Anyone else have a bio final coming up? Mine is tomorrow. And just like a few (or most) of you, I've waited until last minute.
Kkjjj
THATS ME RIGHT NOW AND ITS 4AM AND I STILL HAVENT SLEPT
LMAO BIG MOOD TOMORROW 12/19/17 😩
I always watch a crash course before every test for my AP Biology class. Helps me remember what I've learned. I'm not very good at studying so visuals always help.
Thank you for all these biology videos! Best study tool ever
i think this is my favourite crash course biology!! It was interesting and easy to follow. Soooo much less complex than previous videos :)
I'm gonna binge Hank's videos for my semester exam tomorrow. Luckily he has a video on everything I need to know, evolution, classification, and human systems. Yay!
"So thanks to the soot-covered everything, I've got problems."
lolololol
Pshhh. I hate it when people put comments that are not related to the video. Evolution does not explain how the world is first created. If you want to ask questions about theories on how the world began, then watch a video of how the universe is developed, and not a video about natural selection
+0xJamica0x It's not so much natural selection that is the problem with creationists, it is more so mutations, as natural selection does not create any variation in the DNA, but only selects based on what is available. Mutations on the other hand, are what cause the variation from species to species (for the most part).
I've learned more in an hour of watching Hank's videos than in a month of actual Bio class. Thanks for the videos. :)
I'm using these for finals, and I think my bio class is fantastic. There is just something really helpful about being able to call up another version of the lesson on demand, start it, stop it, and review whatever I don't get for hours! I asked my prof if she'd be down for this, but she said she had something else to do...
Kid: dad what does stove do
*goes to touch*
Dad: Don't you-
Dad: *sigh* natural selection.
Ya Boi #parentoftheyear
Tbh, I think this is more of an example of a that is irrelevant to natural selection.
If a preference to touch stoves would be detrimental to reproduction, it would be selected against and kids touching stoves would be a rare occurence. Wouldn't it?
Quitschi especially if the dad knows not to to touch it, it should (loosely should) be hardwired in the kid too. This would be more learning, which is change within a lifetime
@@ChalkLitIScream but the kid is a kid, probably dad was dumb when he was little too. He only learned after touching the stove. Teaching as much as learning... I guess.
why.... why......@@Diamondraw4Real
I do online school and basically skip the lessons and go straight to the assessments. I literally just learned 6 lessons worth of Biology in this video 😂😂😂😂
Thank you I've been cramming for the last three days and this video helped the most
This video contained more visually explained examples than your other videos, which made me understand the concepts better. So I would suggest using more of those.
Who is watching this because your Biology teacher forced you to do it? 🙋🏼♀️
Lets goooo
1 week ago, and I’m just now doing it
You should thank your teacher
Up top
I have to write down 10 things I learned from this video🙄
I learned more in a day, than I did with my teacher for 1 year
This is a very good presentation of the facts. Thank you CrashCourse.
I home school my 2 teenage kids and these crash course videos help out so much. Thank You!!
Thank you for the wonderful video😊 I've learned a lot from this video i knew that this kind of selection is the process that results in the adaptation of an organism to its environment by means of selectively reproducing changes in its genotype constitution.
these would be excellent to have in a podcast and I'm sure you'd get a huge audience !
I'd actually argue that peacock tails would be a great example of stabilizing selection. They need a big enough tail to attract the ladies, but not so huge that they can't move to find food or escape predators before they've had a chance to pass on their genes. Thoughts? Love this channel : ) -BOGO
Hi! Thanks for this helpful blog. As a student it is very important for us to know more about the artificial selection. I also learned that we should give importance to the plants and animals because they are the ones who produce our food in our daily lives . And now because of your blog I knew the advantages ad disadvantages of artificial selection. Thank you for sharing your knowledge with us .
love love LOVE UR VIDEOS, I LEARN SOO MUCH FROM THEM....thank u sooo much
it's 2019 already and I always used this if I have an exam in Biology :)
You forgot to mention Alfred Russel Wallace
Thomas Haynes Poor Wallace. Forgotten by history and future scientists.
Awesome videos Hank is just a blast!!!! Super smart. Thanks!!!
This blog is very informative and useful especially to those people who are engaged in Agricultural Industry. Being able to give the advantages and disadvantages of the said topic is good. With that, readers can think wisely whether to engage to Artificial Selection or not. Also, clipping many pictures makes it appealing to read and easy to understand. In the end, I learned that Artificial Selection is important in terms that people will benefit from it through lots of agricultural produce but should be wise enough because it can affects the economy, environment and God’s plan of creation.
Thank you! This is how I study for my tests!!! ❤️👍😄😂
Do you guys have a video about cellular evolution?
i wish we had these channels when i was growing up, would've aced the exams
You can turn the closed caption on at the bottom of the video on the right side. I live in the city and it is often loud outside my windows, so I usually read along with Hank. Hope this helps!
10:48 - so that's why gingers, nerds and shy guys have such a hard time at school. Thank you, Darwin!
Marcin Pasternacki You had Shy Guys at your school? Were there any Goombas?
+Marcin Pasternacki HAHAHAHA TRUUUU I am 5"4 and every freshman in my high school is about 5"10-6"3 (I am talking about males and I am a male). It is very difficult!!
+Tricell CEO looool references
Marcin Pasternacki your profile picture goes with your comment
I'm here cause my country is completely ignoring a disease and all social with eachother spreading it atm.
I love how i'm watching this in my free time during the summer :)
So, you just summed the first six chapters of my physical anthropology textbook in 12 minuets. This is amazing!
ALFRED RUSSEL WALLACE! Never Forget
Right?!? Everyone leaves him out.
+Olivia G and herbert spencer
I was just thinking that. He says Charles Darwin was the first? Eh! Wrong.
Great strategy: be cute so humans take care of you!
THIS VIDEO omgoodness, thankyou this has been a lifesaver, i had to take a biology test first day of school and you just summed up EVERYTHING in the theme evolution that i had to learn, love love love it :'D
Thank you, Crash Course team, for these videos!
exams today...... Thank god for these videos
I think I have a crush on Hank
thank you for making this video to help me understand this for my biology class
This is such an awesome channel!! Thank you !!!
Thumbs up if your Biology teacher forced you to watch this!
I wish my biology teacher did stuff like this
Oh no! Teachers educating kids. How evil of them. Whatever next?
Edge you katon is over eated.
Thumbs up if you came on your own cause you actually like science!
@@frosty_1000 I originally came to understand meiosis a little better, but now I'm on this video which is just from curiosity. I am starting to like biology more and more.
1:15
Turn on Captions
Hi Hank, I'm not sure if anyone has mentioned this before but the peppered moths were first collected from Manchester not London. It was another case of the city being at the forefront of scientific discovery. Sorry for the pedantry, your videos are great!
This helped so much! Thank you!
All of these comments are from 3+ years ago I just got sent here for school 🤦🏽♀️🌝
Mr.olsen if you can see this, I’m falling asleep watching the videos your making us watch 😡
You can download the transcript and just read it
Thanks for the subtitles
my science teacher shows us these in class and she always talks over the video so I just gave up on trying to hear him and I'm watching this on my own time at home.
comments 2010: oh cool video!
comments 2020: 90% MEMES
For people who don't get it here is the difference between macro and micro evolution.
Macro Evolution allows for slight variation that will help shape a distinct feature in the future but is not easily noticable yet.
The only difference between the two is time. Longer periods of time causes an accumulation of these changes wich causes the earlier mentioned distinct features this is called micro evolution.
Given enough time there is even species creation, because of a significant change in DNA.
***** God made evolution happen. Not to call it bullying, but i'm going ot let the Almighty have his way on this one.
***** This is BS. High School Biology classes spend ONE week on ONE chapter on evolution, then moves on. I had to go outside of school to research it in further depth, as our childhoods are spent indoctrinated into our parents religion, and we're effectively sheltered from the facts and truths that science sheds light on. You should lay blame on indoctrination where blame is due, within the archaic, science-denying lies of religious myth that had people believing the earth was flat and Antarctica penguins tottled all the way from their frigid habitats to the desert climate of Noah. You're fucking insane.
You switched the two. Macro is the longer one :)
You switched the two. Macro is the longer one :)
+Why not realisitc Zoidberg? That's not strictly true.
The distinction is strange, but in most cases macro-evolution is just speciation. It requires more than time in most cases. If two populations interbreed then they're the same species and will remain the same species because this interbreeding prevents them from diversifying on their own. For "macro-evolution" two populations must become separated, either by time (as you said) or by space, the latter being far easier to observe. Once separated the two populations can diversify independently and eventually be unable to interbreed once reintroduced but it's not possible to do *unless* you have that initial separation.
I can't begin to say how happy I was when I found out this was a video for our high school biology class.
Great GREAT video! Thank you so much for all of the information. I will be subscribing and watching all or your videos now. lol
anyone else being forced to watch this during coronacation?
R.I.P Lemon
awesome video!!! Thanks for helping me on my science project
please could you make a video of convergent evolution, that would really emphasize the impact of natural selection on different classes of species. and thank you for your great work.
Who’s watching this during home school because of quarantine
Is anyone else here out of pure interest and not for an exam?
Me, I got sacked from work so I´m trying to get as smart as possible before my mum kicks me out of the house
Hopefully if I get smart enough I can find a mate to pass my genes on then die in a ditch
nope
ismellrudolph damn
catrina g I'm here cause I need to improve my english :3
I find myself rewatching these constantly before my bio exam
Why didn't I know about this channel when I was in 6th grade? It would have made my test grades higher XD I'm glad I found out about this channel it's like I have a teacher's help when I'm at home. I'm pretty sure I will see improvement in my grades soon with the help of this channel. Thanks guys :D
Do creationists always try to argue with people in the TH-cam comment section?
+crue woe They don't have anywhere else to go.
+crue woe Usually Creationist say something stupid, then an Atheist calls them stupid, then another Atheist calls that Atheist stupid, and so on and so on till you have a flamewar
lol, so true although it often gets started by atheists, and a creationist calls the atheist stupid, and then another creationist calls that creationist stupid, etc.
Alec Reilly I don't see anyone even arguing lmao
im creatiion ist
Thank you hank so much this helped so much as I go to a Christian school so we only talk about how natural selection is wrong
smbatman123 that’s really sad
*"...only talk about how natural selection is wrong:* It is, smbatman123. It is.
_“We have both spent effort and ink… to show that Darwin’s theory of natural selection is fatally flawed.”_
_“We think this argument_ [natural selection] _although ubiquitous in the literature, is fallacious.”_
~Jerry Fodor and Massimo Piattelli-Palmarini
@@IsaacNussbaum please continue...
I also go to a Christian school, I'm taught that natural selection is NOT equal to evolution 1.) Because no new creatures were created, even within population shifts.
2.) Most mutations are harmful and do not help the creature
3.) It's just nature taking care of itself
@@melylamash Im creationist its sad seeing this many people not even beliving God created each and every one of them :( :( :(
As for me expression at 1:17 is priceless, Love you Man
Because its the beauty of evolution caught and recorded! its fantastic.
your face on that moth😂
Bad genes will eventually die off, and only the best/most desired genes will survive.
I ❤️❤️ Crash Course. It helps so much
Hand and his corgi are so cuuuute!
Does anyone else take notes while watching these videos?
+canonme1 yes, I think it helps to build nice coherent notes. A good summary of large book chapters of same topics
canonme1 I do all the time even if I don't have an exam or its above my grade level
I do to because it is a lot easer then when a teacher is explaining a lot of things
so I. think its good to take nots on this video Evan tho Im forced to to get a good grade by way teachers.
He does not blink because it is made of lots of little videos.
I love crash course. Thank you so much.
You look more natural and fitted out side the studio. Thanks to the selection of your natural characters.
Makes me sad that Darwin gets all the credit
Lily Griffin well,Alfred agreed to let Darwin be the main spokesman for evolution and get most of the credit because Darwin had gathered much more proof
Darwin said it was just a theory he never said it was a sure fact
@@smartave5882 another person who doesn't understand what 'theory' means in a scientific context.
@@angryoldcanadian3905 Yeah. An educated guess. Not a fact. Evolution can't and never will be proven.
Edit: I just looked it up and it says a theory is a reliable account. Basically an educated guess.
@@smartave5882 False
A scientific theory is an explanation of an aspect of the natural world that can be repeatedly tested and verified in accordance with the scientific method, using accepted protocols of observation, measurement, and evaluation of results. Where possible, theories are tested under controlled conditions in an experiment.
Evolution is a FACT. An educated guess is called a Hypothesis. Evolution is proven more than gravity... which is also a theory AND a fact.
This is the problem with those who lack a scientific education. To say that evolution is not a fact shows your ignorance, nothing more
4:44 Looks like hank predicted 2020.
Yeah but that wasn’t because of overpopulation
This episode was great!
Dude you make Bio so much easier Thanks Dude !!!!! Keep it up