Bozeman science: Abiogenesis

hi it's mr. Andersen and welcome to biology essentials video number 10 this video is on abiogenesis in other words how life came to be through natural processes now one of the first people to kind of tackle this you know really deep questions with somebody named Aristotle and he came up with this idea of weird like Ella elements there's certain elements and there's an element that can breathe life into inanimate objects and so that's kind of reflected here in this this is from a Roman poet in 20 ad this is a recipe to make be so if you want to make bees you kill a bowl you build a shed you place the dead Bowl in the shed on some branches and herbs you wait for summer and then the decaying body of the bowl will produce bees and so this idea back then was called spontaneous generation in other words people knew for example the a seed if you plant it would eventually turn into a plant but they didn't really understand this in animals in other words how we went from nothing to animals showing up and so they didn't really understand it and they thought somehow that inanimate objects were creating animate objects um once scientists actually started taking a look at this you could say they could figure it out really easy in other words let's say they put a stake out and I leave it there for a day well maggots are going to start to build up on the steak and so they wondered well we're was the steak actually creating these maggots how are they getting there and so a really simple experiment would be to take two steaks let's have one steak that looks like this and once take that we're going to actually cover it and so nothing can get to it after we put it out there so no things like flies can land and put their eggs on it and so once we did that then we figured out that life wasn't coming from life life is coming from actually inanimate objects it was actually coming from life and one of the most famous experiments is pest juror and we'll talk more about him when we talk about bacteria and his arrival at the past your flask and really saying that spontaneous generation is not true in other words you don't create life this way so what did that leave unanswered it left unanswered how did life come to be on our planet and so scientists have been working at this for hundreds of years but especially in the 1900s they had really a few studies that showed us how life could come from nonliving material in other words how we could get life from nothing and so let's get started first of all most scientists agree that it just didn't happen like that with a snap of the finger we had to go from life no life to life and to get there we had to go through a series of steps where each of those steps make sense and so the idea is that we went from chemistry too simple monomers the building blocks of life an example could be amino acids those were then polymerized or added together to create polymers and made what are called protocells or simple cells that aren't really alive and then eventually we have cells and eventually we have life now once we have that then natural selection is going to take over and then we're going to have the life that we have today and we can see that we've talked about that in this whole unit on evolution now the first thing you should understand is that the primitive earth looked a lot different than the earth that we have today in other words the atmosphere didn't contain oxygen and as a result of that it was a reducing kind of an atmosphere oxygen has a tendency to really pull on electrons and so life was different back then and so if we're going to study this we can't study it in our atmosphere we actually have to study in the lab and so how do we figure out this progression well we start in science by making what are called hypotheses to answer all of these questions we make a hypothesis with is simply just a guess and then we test it now it's an educated guess and so we think we know what we're going to find every time we make a hypothesis but one of the first things is to figure out where life came to be and we think that Darwin had suggested maybe it starts in some you know warm pond and so this idea of a primordial soup and a lot of people are starting to look at the surfaces in other words maybe it's on clay it's a great place where you could actually make some of this polymerization take place and then what's the sequence there are some scientists that are looking at maybe genes show it up first and the others that looked at metabolism maybe metabolism showed up so let's get started let's start by tackling the monomer side in other words how do we go from chemistry to simple building blocks of life and the most famous experiment is called the miller-urey experiment stanley miller here and then Harold Urey over here and what they did is they try to in the lab get rid of oxygen and try to simulate what this early Earth's atmosphere looked like and so this would be the chemicals they thought that we're in this primitive atmosphere now you can see there's a vacuum pump over here so we can get rid of our atmosphere and then we just add energy to it energy in the form of electricity in their experiment but it's simulating like lightning in this early Earth's atmosphere so why is this famous well it's famous because they stuck their probe in here or they stuck their probe in here and they found the building blocks of life in other words they found amino acids now they found a few amino acids we've actually looked through their work and found that they found in these experiments 25 amino acids now there are only 20 amino acids used in living things and so they found that you could go from simple chemicals or chemistry two monomers which eventually could become polymers okay another thing interesting the miller-urey experiment is that the amino acids that showed up right away our old amino acids in other words they show up in the latest Universal ancestor in other words the one ancestor that's shared by all organisms if we look at the most ancient organisms on our planet in other words those that show the most DNA that's shared by all living organisms we find that those genes actually code for the amino acids that were found in the miller-urey experiment and so this is showing evidence showing that life could have formed a biotic Lee now once we go from monomers the next step is to go from a monomer to eventually a polymer in other words amino acids are the building blocks of life but they're not life what are as life made up of life is made up of proteins and so how do we go from simple monomers to polymers well first we have to figure out where that could occur a lotta organ a lot of scientists think it started some kind of a primordial soup some scientists think it started in thermal vents it was probably shielded from from space because we'd have a lot of radiation that would quickly break down any of these polymers the next thing is to figure out what's the sequence of events early studies most people thought that RNA was showing up first in other words we had nucleotides eventually building into RNA and that's shared by all organisms so a lot of scientists think maybe that showed up first and so we had this hereditary material that's passed from one to another but a lot of scientists are now looking at metabolism and finding that things like the kreb cycle that's what this is the it's shared by almost all organisms so that means it goes way back to that latest Universal ancestor and so which of these is right well there's fields of science that are studying both of these ideas and the answer we're starting to realize is probably a combination of the two and so the the tricky part about figuring of the origin of life is that they didn't leave really good fossils these first life-forms didn't leave great fossils and so we don't have super evidence of that one thing I know is true that once we go from these protocells to the first cells then natural selection is going to take over and once we have charles darwin's mechanism for evolution take over then it's really going to start rolling and so what were these first life forms aren't our planet well the first fossil evidence are what are called stromatolites and so these are rock taking this is from Glacier National Park and so stromatolites formed really ancient in our life and they're essentially bacterial mats these are some stromatolites that are forming today in Australia and so what you have is bacteria forming up on the top you have sediment forming on top of that and then you have bacteria forming on that and it eventually builds up like this and you can sign kind of see that built up pattern like this and so once life shows up which is 3.5 3.8 billion years ago then natural selection is going to take over and i'll talk more about specific evidence that scientists are grabbing on to to kind of test those hypotheses in the next podcast so i hope that's helpful