So here we have an example problem that wants us to analyze the diagram and fill in the blanks, and then it says to consider an example of the complete cycle. So notice down below we've got this diagram showing a cycle, and at the very top here in green, what we have are environmental changes. Now recall from our previous lesson videos that the environment around us is constantly changing. And as the environment changes, it also alters the selective pressures on any particular population of a species. And so, of course, altering the selective pressures is going to drive evolutionary adaptations.

Now these evolutionary adaptations can go on to alter the dynamics of ecological interaction or the interactions that life has with its environment, and that can go on to drive or influence environmental changes, including influencing changes in the climate. And so now let's consider an example of the complete cycle. And so early on in Earth's history, one billion years ago, Earth's early atmosphere had lots of carbon dioxide gas and very little oxygen gas. And so this altered the selective pressures on life because most of the life was anaerobic, meaning that it did not utilize oxygen gas simply because there was not that much of it around. However, there was just enough oxygen gas for the process of photosynthesis to evolve.

And so photosynthesis alters the dynamics of ecological interactions because it changes the way that life can interact with the environment. And so now with the process of photosynthesis, life can now consume a lot of that carbon dioxide gas in the atmosphere and start to produce more of that limited oxygen gas in the atmosphere. And so over long periods of time, eventually, this is going to cause environmental changes because eventually the amount of oxygen in the atmosphere will surpass the amount of carbon dioxide in the atmosphere. And having more oxygen in the atmosphere can lead to the formation of the ozone layer, which can help to block solar radiation, again, changing the selective pressures on a population, and that can allow for evolutionary adaptations for aquatic life to now transition onto the land, now that it's safe to go onto the land with the ozone layer blocking some of the solar radiation. And now that life is on land, again, that can change ecological interactions and drive more environmental changes and so on.

And so the main point here is that environmental changes drive evolutionary adaptations, but evolutionary adaptations can go on to drive more environmental changes. So there is this dynamic interplay between the two. And so this here concludes this example problem, and I'll see you all in our next video.