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AP®︎/College Biology
DNA spells evolution
Genetic mutations lead to variations in traits. These variations can provide survival advantages, resulting in new species over generations. For example, brown bears evolved into polar bears due to beneficial mutations. Created by NOVA.
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At 2 minutes 6 seconds what are double helical threads?(4 votes)
Hello! He is referring to how DNA or genetics connects all living things. "Double helical threads" describe the structure of DNA which is a double stranded helix. Basically a twisted ladder. DNA is made of two backbones made of alternating sugar and phosphate which are connected by nitrogenous bases. Hope this helps!(4 votes)
If variation occurs because of a falsely copied base pair in the DNA, wouldn't it mean that eventually, there would be all sorts of combinations, not just adenine with thymine, and cytosine with guanine? It seems like if mutations occur, then the pairs would not match up, causing many wrong base pairs. Or does it eventually fix itself?(4 votes)
No, because a false copied pair only results in changes in one strand of DNA otherwise known as RNA and then the corresponding nucleotide is made to match that RNA even if it has mutations, I Hope that makes sense. =D(1 vote)
Isn't it just Natural Selection when the fur of one one bear becomes lighter in shade and color then another? Because that doesn't really give any more support for the evolutionary theory than if some one with brown hair had a child with blond hair. The species doesn't change.(1 vote)
No, evolution is the change in heritable characteristics of biological populations over successive generations.
DNA and genes are how heritable characteristics are passed on from one generation to the next.
Selection both natural and artificial determines which of these inherited changes are beneficial and which are detrimental.
What you are referring to is speciation, speciation is an effect of the buildup of genetic changes in separate population of the same species to the point where members of the two populations can no longer produce viable offspring.
Speciation doesn't happen from one generation to the next, it takes many generations for the changes to build up.
Look at the species okapi and giraffe. They are both decedents of a common ancestor with short necks. For their ancestor a major selection pressure was neck length. Ones with longer necks we better able to get to high branches for food. The longer the neck the more resources it had access to so the ones with long necks were able to stay put where the food was high but ones with a shorter neck either went hungry or found places with lower food. This spit the population which allowed for speciation and we now have shorter necked okapi and long necked giraffe.
If you look at the DNA and the physical characteristics of okapi and giraffe they are very similar. There are even issues like a nerve the recurrent laryngeal nerve that connects the brain and the larynx. In okapi this nerve branches off the vagus nerve down in the chest, in a giraffe this is the case as well but because of this the nerve has to travers from the brain down into the chest and all the way up to the top of the neck where the larynx is. This design is better explained by progressive elongation of the neck of giraffe over time than it being made that way to begin with.(4 votes)
- At2:06; what are double helical threads?(1 vote)
- Hi, Hailey! He is referring to how DNA or genetics connects all living things. "Double helical threads" describe the structure of DNA which is a double stranded helix. Basically a twisted ladder. DNA is made of two backbones made of alternating sugar and phosphate which are connected by nitrogenous bases. Hope this helps!(3 votes)
- At0:53, is it possible for adenine to pair with guanine or cytosine?(2 votes)
- how long would dna last with it being still fresh(0 votes)
2:06Video transcript
If Darwin came back today, what would he be
most excited by in modern science? I think it would be the whole world of genetics. That’s the answer to all the big questions
he had – how does variation emerge? And how could that be transmitted? Let’s return to our brown bears stranded
in the Arctic to consider the impact of genetics on our understanding of evolution. Each bear is made up of cells. And if we take a brown bear cell, and tunnel
into its nucleus, we find DNA – the molecule with the genetic instructions for building,
in this case, a brown bear, written in a four-letter code. Now, the thing about DNA—it’s not perfect. When it’s copied, mistakes get made. Mutations, in other words, that sometimes
affect an organism’s traits and that sometimes can be passed from parent to offspring. So the variation at the heart of evolution—it’s
genetic variation. Slight differences in DNA that—for example—could
make some bears a bit lighter in color, a bit more insulated against the cold, and a
bit more capable of digesting fattier foods like seals. Evolution is essentially any change in the
genetic composition of a population. Mutations are random, so they’re not always
helpful. But the bears with mutations that gave them
some advantage for Arctic living survived and reproduced more often than bears without
them. They passed the genes responsible for those
adaptations onto their cubs. Over generations, more bears inherited and
elaborated on these and other changes in the DNA. The eventual result – a polar bear. And when we tunnel into its cells, we find
polar bear DNA. Think of DNA as the raw material that—across
billions of years—evolution has molded and built into countless forms of life. We are all related, tied to one another by
the most spectacular of double helical threads.