So where did Darwin's ideas come from? I mean, he didn't just think them up one day. He actually came up with these ideas based on his experiences, and one of the most influential experiences that Darwin had, was his travel on the boat, the Beagle. Yes, like the dog, like Snoopy. And he voyaged on the Beagle to the Galápagos Islands, amongst other places, and there he noticed some variation between the finches on the different islands. And this got him thinking, he said, difference between these finches. Get the gears turning, boom, evolution. No, it wasn't that simple actually. Darwin came up with some various ideas that helped him piece together the puzzle we talked about on the previous page. One of these ideas was something he called fitness, which is the ability of an organism to survive and reproduce. So different features are going to affect an organism's fitness. Now, another idea he came up with is an adaptation. This is a trait that is maintained and evolved by natural selection that enhances the fitness of an organism. So in looking at all these different finches, he noticed that the morphology of these finches, the way they appeared was pretty different and he assumed that due to different pressures on the different islands, different adaptations were favored in some places and not in others and it caused these finches to become so different from each other even though they were all kind of in this small area, these chain of islands. Now, a nice example of evolution at work is with the Peppered Moth and it relates to this idea called Industrial Melanism. So basically, Industrial Melanism is simply when organisms evolve darker pigmentation due to industrial pollution. So, you know, rewind time a little bit to industrial England. And before the Industrial Revolution, all the peppered moths, or most of the peppered moths anyway, looked like this. Like they had pepper on them, hence the name. But after the Industrial Revolution, pretty much all the moths looked like this one, basically, solid black. What caused the change? Well, the idea here is that, because the environment changed, right, because of the Industrial Revolution, because of the pollution that was getting into the environment, it made everything darker. So as the environment got darker, these light peppered moths became easier to see. Whereas, the few peppered moths who were all dark colored, they had, they were more fit. Their fitness was better because they were harder to spot on the now darkening environment. So, over generations, what happened was these light colored peppered moths, they got picked off. They were the ones who got eaten because they were easier to see. So, they contributed less and less to the gene pool. The dark moths, they had more fitness so they contributed more and more to the gene pool. So over successive generations, there were fewer and fewer light colored peppered moths and more and more dark colored peppered moths. Now you don't need to worry about knowing about the peppered moths in particular or industrial melanism, I just think this is a really nice example of evolution at play that was recorded by humans during human history. So, another process in evolution that we can observe quite readily is artificial selection and this is the process by which humans breed organisms for certain traits. And this was something that Darwin was quite familiar with and influenced his thinking about evolution. So a great example are dogs. Various breeds of dogs have been selected by humans. The various traits of those breeds were selected for when humans were breeding these animals. And today, we have a huge range of traits that different breeds of dogs can have. And just to illustrate that wide range of traits, we have here a Great Dane, a very, very large dog, and you might notice his coat is a lighter color. And then right here we've got this itty bitty little black chihuahua. So, a lot of variation in color, size, shape, artificial selection can produce a lot of different forms just like evolution can produce all the forms that we see today. Now, one other example before we turn the page is corn. Yeah. Corn actually used to look like this garbage, but you don't wanna eat that. And you spend all this hard work trying to grow this plant, you just get this little dinky stalk of edible material, that's not going to fly. So humans selectively bred corn until boom, it looks like this like we know it today. So artificial selection has been a big part of human history because, well, humans have selected for various traits in farm animals, farm crops, all sorts of agricultural things. Alright. Now let's turn the page to talk about some more detail.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny40m
- 26. Prokaryotes4h 59m
- 27. Protists1h 6m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
21. Evolution
Introduction to Evolution and Natural Selection
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