Natural Selection - Crash Course Biology #14 

Anyone Binge-watching the bio videos the day before your exam?

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.

4:39 " This leads to what Darwin called 'the struggle for existence' " Did you mean: my life

Could you have a test at the end of videos as an option maybe? would help people study better. Just as an option

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.

Study? No I'm gonna watch crash course videos and hope for the best!

nobody: him: I'm human but let's just pretend i'm a m o t h

Who else is cramming for a bio final or sat

I swear, this dude never blinks????

why dont colleges just send you to this channel and save us hours of useless lectures

I KNEW IT I KNEW THAT YOU'D BRING UP THE PEPPERED MOTHS

I can't believe that the video released 8 years ago 👀

You saved me I have such a better understanding about this unit. I wish you were my biology teacher.

Thank you for your videos. I wish all my science teacher were like you :)

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.

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

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

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.

This is all wrong The answer to life the universe and everything is 42

i think this is my favourite crash course biology!! It was interesting and easy to follow. Soooo much less complex than previous videos :)

Thank you for all these biology videos! Best study tool ever

you save my ass every time i have a biology exam. thanks buddy.

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.

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 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.

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

This is a very good presentation of the facts. Thank you CrashCourse.

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.

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.

Thank you I've been cramming for the last three days and this video helped the most

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

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.

Who is watching this because your Biology teacher forced you to do it? 🙋🏼‍♀️

I home school my 2 teenage kids and these crash course videos help out so much. Thank 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

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 😂😂😂😂

these would be excellent to have in a podcast and I'm sure you'd get a huge audience !

Awesome videos Hank is just a blast!!!! Super smart. Thanks!!!

So, you just summed the first six chapters of my physical anthropology textbook in 12 minuets. This is amazing!

it's 2019 already and I always used this if I have an exam in Biology :)

I learned more in a day, than I did with my teacher for 1 year

Thank you, Crash Course team, for these videos!

thank you for making this video to help me understand this for my biology class

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

Do you guys have a video about cellular evolution?

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.

awesome video!!! Thanks for helping me on my science project

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

Thank you! This is how I study for my tests!!! ❤️👍😄😂

I love how i'm watching this in my free time during the summer :)

This is such an awesome channel!! Thank you !!!

exams today...... Thank god for these videos

anyone else being forced to watch this during coronacation?

very useful. Peppered Moth example even useful for my Primary KS2s. Good work.

This helped so much! Thank you!

Thumbs up if your Biology teacher forced you to watch this!

Is anyone else here out of pure interest and not for an exam?

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

10:48 - so that's why gingers, nerds and shy guys have such a hard time at school. Thank you, Darwin!

Great strategy: be cute so humans take care of you!

Thanks for the subtitles

your videos are good to watch for science fair projects

You forgot to mention Alfred Russel Wallace

1:15 Turn on Captions

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!

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!

ALFRED RUSSEL WALLACE! Never Forget

I think I have a crush on Hank

I love crash course. Thank you so much.

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.

All of these comments are from 3+ years ago I just got sent here for school 🤦🏽‍♀️🌝

I'm here cause my country is completely ignoring a disease and all social with eachother spreading it atm.

Great, very interesting video. Thanks.

I find myself rewatching these constantly before my bio exam

comments 2010: oh cool video! comments 2020: 90% MEMES

Anyone watching this to revise for their exams

This episode was great!

This was nicely explained, thanks.

R.I.P Lemon

Who’s watching this during home school because of quarantine

Dude you make Bio so much easier Thanks Dude !!!!! Keep it up

thanks anthro for redirecting me to crash course, I miss these guys

Mr.olsen if you can see this, I’m falling asleep watching the videos your making us watch 😡

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. 

Thanks you charles darwin for your astounding theory. I got to hand it to ya it blew my mind once I've absorb every bit of information that for me sometimes I had to redo over again just to make out what you are tying to say. :)

Really good man, very interesting and a good way of explaining, not just because the specific vocabulary but the exitement you put while speacking. If there is any big spelling mistake its because english is not my mother language so i apologyse

What is the point on spending $5,000 per semester in college, just to have my professors make me watch this hooligan on RU-vid WHICH I COULD HAVE DONE FOR FREE. What an absolute rip off.

Do creationists always try to argue with people in the RU-vid comment section?

Thanks for the help! Great video

Thx, Literally answered my question in the first 45 seconds

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

Makes me sad that Darwin gets all the credit

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

Good explanation, thanks a lot