Evolution doesn’t have goals or dated deadlines, but simply responds to environmental change.
Evolution doesn’t have goals or dated deadlines, but simply responds to environmental change. Seen through continual changes in genotypic frequencies (1:09), the fossil record (2:01) and antibiotic resistance (4:26) - evolution isn’t about the destination, but the pathway of change.
The Question of the Day asks (7:45) N,N-diethyl-meta-toluamide is an insect repellent developed by the US Army in 1946. What is it commonly known as?
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Hi and welcome to the APsolute RecAP: Biology Edition. Today’s episode will recap Continuing Evolution
Let’s zoom out:
Unit 7 – Natural Selection
Topic – 7.8
Big idea – Evolution
What??? There’s still more evolution? Yup - life is never finished. If all of the organisms on Earth are in an evolutionary race, they might be disappointed to learn that there is no finish line for completion nor medals for most advanced. The organism that didn’t leave the starting mark is equally as successful as the organism which leaped past every obstacle to climb the tallest mountain. At least evolutionarily. If the environment changes, life continues to evolve within it.
Let’s zoom in:
Populations of organisms continuously evolve. Ah, there's that word again - populations. Remember, organisms have phenotypes on which natural selection acts. Some survive to reproduce, whereas others do not. But it is on the population level where reproduction actually occurs, with members of the same species interacting in the same geographic area. And so populations evolve over time, with allele frequencies fluctuating from one generation to the next. And it’s genomic changes which affect phenotypic changes over time! After that you have the community level, with multiple populations interacting. Then the ecosystem, where populations interact with the abiotic factors of the environment.
One of the great pieces of evidence for evolution is the continuous change in the fossil record. A fossil is a record of an organism that may show the size, shape and even texture of different body parts. Some common examples include skin, teeth, skulls, nests, tracks, and even dung. Yup, poop can be classified as fossil evidence. But it’s often true form fossils that tell the greatest story about an organism’s past. Consider the evolution of cetaceans, oceanic mammals like whales and dolphins. Evolved from a wolf-like land mammal, skull fossil evidence shows the migration of the nostril opening from snout to blowhole. 47 million years ago was Articocetus, with nostril opening at the end of the snout, right near the mouth. 36 mya was Prozeuglodon, with a nose opening halfway between the eyeballs and the snout’s end. Now, the extant skull of the Amazonian dolphin has a nostril opening at top of the skull, positioned right in between the eyeballs. Having a respiratory opening on the top of the skull is advantageous, since this is the part of the cetacean which interacts with the air first when approaching the ocean’s surface.
Antibiotic resistance - a monster we unfortunately created in the “for better or for worse” path of modern medicine. Let’s break it down with the four steps of natural selection from the bacterial perspective. 1st - overproduction of offspring. Well that's very true, some bacteria reproduce by binary fission every 30 minutes. 2nd - genetic variation. Less so for prokaryotes since bacteria are identical through asexual reproduction. However, random mutations and conjugation ensure that there is diversity in the population. 3rd - struggle to survive. This is where antibiotics come in. Most, but not all the bacteria will meet their maker. And 4th. Successful reproduction. The few remaining bacteria will reproduce, passing on their inherent and random antibiotic resistance gene to the next generation. Over time, more and more bacteria in the population will be resistant to that antibiotic. We see a similar pattern of evolution with pesticides, herbicides and chemotherapy drugs.
Lastly, and this one hits a bit too close to home in 2021, pathogens also evolve to cause new diseases. Yikes. Pathogens are any bacteria, virus, or microorganism that can cause disease. Yes, even though viruses are technically non-living, they do contain genomes that change overtime. This means that some pathogens evolve to infect new hosts from one year to the next and can be classified and categorized with common ancestry. The COVID-19 virus is the chemical cousin to several other viruses, and shares a recent common ancestor with bat coronaviruses. RNA viruses have high mutation rates, through base substitution, insertion, deletion or antigenic drift. Mutations are the reason why we currently need an updated annual flu vaccine. But remember, a virus can only penetrate a host cell with a specific matching receptor. And so, just as COVID evolved to infect humans, it may also evolve away from human hosts.
Time for unit connections. Like most topics in evolution, there is a connection to Unit 5: Heredity, as genotype frequencies change over time within a population. Viral infection involves cell communication, so there's a cross-over to unit 4 with ligands. And of course, populations fall within the ecosystem hierarchy discussed in Unit 8: Ecology. Alright, what about the exam? This is a good topic to interpret graphs and practice distinguishing between variable groups. Specifically as it relates to science skill 6 - develop and justify scientific arguments using evidence.
To recap…
Evolution doesn’t have goals or dated deadlines, but simply responds to environmental change. Seen through continual changes in genotypic frequencies, the fossil record and antibiotic resistance - evolution isn’t about the destination, but the pathway of change.
Coming up next on the Apsolute RecAP Biology Edition – Responses to the environment
Today’s question of the day is about pesticides
Question: N,N-diethyl-meta-toluamide is an insect repellent developed by the US Army in 1946. What is it commonly known as?