Lesson video

This lesson is called Climate Change and Evolution, and is from the unit fossil evidence, selective breeding and explaining evolution.

Hi, there.

My name is Mrs. McCready, and I'm here to guide you through today's lesson.

So thank you very much for joining me today.

In our lesson today, we're going to explain how climate change could affect the evolution of species and lead to extinctions and some of the actions that we can take to help prevent the loss of species.

Now we're gonna cover a number of keywords in our lesson today, and they're listed up here on the screen for you now.

You may wish to pause the video to make a note of them, but I will introduce them to you as we come across them.

Now in our lesson today, we're going to first of all look at natural selection and climate change.

Before we consider climate change and extinction, before considering actions that we can take to protect against species loss.

So are you ready to go? I certainly am.

So let's get started.

So firstly, we need to consider what a species is and understand that not all of the individuals within the same species are exactly alike.

And I'm sure you're already aware of that.

Now these differences between individuals within the same species is called variation.

There is variation between the members of the same species.

As you can see in the photograph there, there is variation between those cats.

Now some of those differences between the individuals are caused by genetic variation, which is differences in the genetic information that is stored within their genome, the DNA that codes for their body.

Now genetic variation is heritable.

It can be passed on from parents to their offspring.

And if we look at the cats in the example there in the photograph there, we can see that they have all inherited different alleles, different versions of genes from their parents.

So some of them look a little bit more like their mum than the others, and they all look similar to each other.

But none of them are the same.

And there is variation in their phenotypes what they look like.

So who explains correctly what is meant by variation? Is it Alex who says variation means passing characteristics from one generation to the next? Is it Aisha who says variation is the differences between members of a species? Or is it Lucas who says variation is all the genetic information stored in the genome? I'll give you five seconds to think about it.

Okay, so did you decide that Aisha is correct? Well, done if you did.

Now, variation means that there is differences between all members of the species, and this means that some members of the species will be better adapted to survive and reproduce in the conditions that they're living in in their habitat than other members of their species.

So let's look at an example.

Let's take the red squirrel.

Most squirrels are well adapted to be camouflaged from their predators and find food.

However, some squirrels are born with a condition called albinism, and albinism causes white fur and red eyes.

So these scribbles are naturally less well camouflaged and they have poorer eyesight.

So they're less well adapted to the environmental conditions in which they are living because they don't blend in with the background with the trees that they're living in.

And they find it harder to find food.

However, environmental conditions can change and are changing as a result of climate change.

And this can lead to natural selection.

Now, natural selection is a process by which a species changes gradually over time.

So if the climate in the habitat where the squirrels are living becomes much snowier, for instance, then the albino squirrels would be better camouflaged against the white snow rather than the red of the fur of the red squirrel.

Now this would give the albino squirrels an advantage.

They would be better camouflaged, so they would be better adapted than the non-albino squirrels in their ability to compete for survival.

They would be less likely to be preyed upon by a predator, and therefore, more likely to survive.

And as a result, if the climate conditions change so that snowy conditions were more common, then the albino squirrels would be more likely to survive and reproduce to pass on the allele for albinism onto their offspring.

And so we would see over time, over a number of generations, the proportion of albino squirrels in the population would increase in each new generation.

Now, scientists believe that this variation, this heritable variation arises randomly.

They are random differences that are introduced into the genome by mutations in the DNA, and some of those variations in the genome.

Some of those heritable variations produce advantageous adaptations.

Many of them don't.

Many of them produce no change to the advantage of the adaptation at all, and some are deleterious, some are quite damaging, and reduce the advantage of the organism.

We also believe that environmental changes drive natural selection.

Now, natural selection causes advantageous adaptations to become more common over generations.

So as conditions change, the adaptations that are best suited to those conditions will change, and the organisms which have them will be more likely to survive.

And therefore, if they've survived, they can reproduce and pass those conditions on.

So if this happens over a very long period of time, and causes the general characteristics of the organism to change over generations, we call this process evolution.

So we've got heritable variation arising randomly through genetic mutation, and some of those variations are advantageous.

That means that the organism is better equipped to survive within the habitat.

This means that they are more likely to survive and reproduce and pass that advantageous allele onto their offspring.

Now this process is called natural selection.

And if over many generations it causes the common characteristics of a species to change, we call that evolution.

So which of the following are necessary for natural selection to take place? Variation, advantage, competition, or reproduction? I'll give you five seconds to think about it.

Well, hopefully you decided that variation is necessary for natural selection to take place.

So is advantage and competition and reproduction.

Well done if you got all of those correct.

Now, many scientific agencies across the world are monitoring climate change and the evidence that they have collected over the last 140 years confirms that climate change is occurring on Earth.

So if we look at the graph here, we can see data from NASA, from the Met Office, from the National Climatic Data Centre and from the Japanese Meteorological agency as well.

And looking at that data, we can see that there is strong agreement by all those four agencies in the data that they have collected.

That means that nobody's made grotesque errors in their data collection because they're all in agreement with each other.

We can also see how there are year to year fluctuations in the global temperature.

But the general trend is an increase in temperature over the past 100 years.

Now even a small increase in Earth's surface temperature can lead to significant impacts.

For instance, the polar ice caps will increase the speed at which they are melting.

The sea level will rise and climate change leads to more frequent severe weather events such as cyclones and intense storms, heat waves and droughts, and heavy rainfall and flooding.

Now, global warming, which leads to climate change is causing changes in the environmental conditions of habitats across the Earth.

Some of those habitats are becoming hotter and drier.

Some of them are becoming wetter or ravaged by storms more frequently or flooded through sea level rises.

And all of these changes are driving natural selection.

How well adapted organisms are to the changing conditions.

So those organisms and the species that they belong to, which are more tolerant to the new conditions, to the drier or hotter conditions, to the wetter or cooler conditions will become more common, whereas those which are less tolerant may struggle to survive.

And this is driving not only natural selection but also changes in biodiversity.

So let's look at this graph again.

What does the graph show about the global surface temperature of Earth? Does it show A, the trend is an increase over the last 100 years? B, the temperature rises every year compared to the previous year? Or C, there is a lot of disagreement between the four scientific agencies who collected the data? I'll give you five seconds to think about it.

Okay, hopefully you chose A that the trend is an increase.

Well done if you did.

Okay, let's consider an example of an organism and its response to climate change.

The Mexican beaded lizard.

Now scientists started studying these lizards in Mexico in 1975, and they saw that there was variation in the population.

Some lizards were able to tolerate high body temperature, and a lack of water, whereas others were not.

So what I'd like you to do is to firstly suggest how the population of lizards might have changed since 1975 due to global warming and climate change.

And then I would like you to explain your answer.

So pause the video and come back to me when you are ready.

Okay, let's review your work.

So firstly, I asked you to suggest how the population of lizards might have changed since 1975 due to global warming and climate change.

And you might have said that the lizards able to tolerate high temperatures and lack of water might have become more common than the lizards that are unable to tolerate those conditions.

And I then asked you to explain your answer.

And you might have said that the lizards able to tolerate the high body temperatures and the lack of water had an advantage as their habitat became hotter and drier due to climate change.

And this led to natural selection.

These lizards were better adapted to survive and reproduce and so became more common in each new generation.

So just check over your work.

Did you get all of those key points? Well done if you did.

Okay, let's move on, and have a look at how climate change is impacting extinction.

Now as we've just seen, evolution is the change in the common characteristics of a species over generations.

Now this happens when the alleles, the different versions of genes that cause advantageous features are passed from one generation to the next through reproduction.

So seeds and eggs are both examples of plants and animals reproducing.

Now the rate of evolution is limited by the rate of reproduction because until new offspring are produced, no changes can occur.

If offspring are produced frequently, then the rate of change can be faster than if offspring are not produced very frequently.

So let's look at this in a bit more detail.

Let's consider the case of the gorilla.

Now, gorillas were classified as critically endangered by the International Union for Conservation of Nature, the IUCN.

Female gorillas take 10 years to reach section maturity at which point they can reproduce.

Whereas male gorilla require 15 to 20 years before they can reproduce.

Now what this means is that firstly it takes a long time for advantageous alleles housed within the parent to be spread through to their offspring.

It takes at least 10 years for a female gorilla to be able to pass on her advantageous alleles, and 15 to 20 years for a male or gorilla to pass on his advantageous alleles.

So therefore, the rate of evolution is slow at least a decade and up to two decades.

So if climate change is happening faster than reproductive rate, then the advantageous alleles within the parent gorillas may not necessarily confer advantage to their offspring by the time that offspring are born.

So this has a potentially significant problem for the gorillas that there is nothing that they can do about because they are unable to reproduce fast enough to necessarily keep up with the pace of climate change.

So all species will evolve quickly to adapt to climate change.

True or false? So hopefully you've said that's false, but can you explain why? So hopefully, you've said that some species evolve slowly, such as the gorilla.

And the rate of evolution can be limited by the rate of reproduction.

Well done if you got both of those correct.

Now in the previous practise task, we looked at the study of lizards in Mexico, the Mexican beaded lizard.

And we suggested that due to climate change and natural selection, the lizards that were able to tolerate high temperatures and lack of water might have become more common than lizards that are unable to do so.

However, scientists concluded from the study that they started in 1975 that 12% of the lizard species that the scientists followed became extinct during the 30 year study.

And that 54% of lizard species in Mexico are likely to be extinct by 2080.

Why though? So let's go and have a look at some reasons.

Now because of natural selection, most species have evolved to be well adapted to a narrow range of environmental conditions within the habitats in which they live.

So living organisms are well adapted to survive within the conditions that they are present in which they are living in.

Because they are living in those conditions all of the time, they need to be able to survive well in them.

And so natural selection has driven good adaptation to those conditions.

However, climate change is happening and at a quickening pace, and in order to survive climate change, species must either migrate, move to a place which has conditions more similar to their original conditions and their existing adaptations.

Or adapt.

Change to suit the new conditions, have more advantageous variations within their body in order to be able to survive the new climate, the new conditions within their habitat.

But this process of adaptation only occurs through natural selection, and it only occurs through random mutations that may be passed on to offspring.

It does not occur by decision.

It does not occur by choice.

Organisms aren't thinking, oh, well I could do with being a little bit cooler because of the warmer conditions, and so I'll have a thinner layer of blubber and less thick fur.

They can't influence those conditions about their own body.

So any changes occur in the following offspring due to advantageous adaptations and chance mutations.

Now the United Nations Intergovernmental Panel on Climate Change, the IPCC, reported in 2023 that half of the 4,000 analysed species that they looked at have moved due to climate change.

For instance, butterfly populations in Europe have shifted up to 200 kilometres further north in response to rising temperatures.

But for some organisms, migration simply is not possible.

For instance, the lizards and other reptiles and amphibians may struggle to find suitable conditions within 50 kilometres of their existing habitats because of the requirement that they have for water for either living in or breeding in.

And so they are very much bound and restricted to the existing location that they are living within, and therefore they are not necessarily going to be able to find somewhere more suitable close enough to them.

That situation is compounded by human activity such as habitat destruction for agriculture and urbanisation for house building and towns and so on.

And so even if they can move to a different location, they might not be able to move by actions that humans are having within that habitat space as well.

So migration is not always possible for organisms. Evolution by natural selection, as I've already said, depends upon advantageous heritable variation appearing spontaneously by mutation within a population.

And that is entirely random.

So it is really difficult to predict whether a species will be able to undergo adaptation to survive climate change because these adaptations arise randomly.

So they may not appear when they are needed.

And even if they do appear when needed, they might not be able to be passed on quickly enough to their offspring in order to build up a sizable population with this more advantageous set of adaptations in order for the whole species to survive.

Because of the rate of reproduction that limits the process of passing on advantageous alleles.

So many species simply cannot evolve fast enough to keep up with the pace of climate change because of their rate of reproduction.

And if we go back to the beaded lizard in Mexico, the temperatures increased so quickly that some species may not have been able to adapt or migrate fast enough in order to survive, which may account for why there was such a high extinction rate within the lizard populations in Mexico.

Now if organisms, if species cannot migrate or adapt fast enough, this could lead to extinction.

Now extinction is the permanent loss of a species when all living members have died out.

And the first example of extinction attributed to climate change was of the Bramble Cay mosaic-tailed rat.

And this was declared extinct by the IUCN in 2015.

The climate changed so quickly that despite their relatively speedy reproduction rate, they simply weren't able to adapt fast enough and became extinct as a result.

So who is correct? Is Andeep correct when he says, "Evolution depends on random variations?" So evolution isn't deliberate or planned.

Is Izzy correct when she says, "Species can choose to evolve to help them survive climate change?" Or is Laura correct when she says, "Some species may not evolve in response to climate change, they may just die out?" I'll give you five seconds to think about it.

Okay, so did you choose Andeep as being correct? And did you choose Laura as being correct as well? Well done if you did.

Now, an internet governmental science-policy organisation estimated that there are eight million different species of plants and animals on Earth.

Now their report identified the top five causes of ongoing extinctions as first, land use change where we're changing land from one purpose to another, such as for agriculture, then direct exploitation of species such as overfishing, over hunting, then climate change, then pollution, and then invasive species.

So species that have been introduced to an area which shouldn't be there and then go and invade and take over that space.

So these are the top five causes of ongoing extinctions as identified by scientists.

And the IPCC estimates that up to 1/3 of species could be extinct by 2070 if emissions contributing to climate change continue to rise.

If in other words, human activity continues as it is and does not change.

So starting with the biggest cause, can you remember which was first, second, third, fourth, and fifth in order of causes of extinction? I'll give you five seconds to think about it.

Okay, let's see how well you remembered that.

Did you start off with D, land use change then list direct exploitation of species letter, C, and then list climate change A, then pollution E, and finally, invasive species B.

Did you get them in the right order? Well done if you did.

Good job.

Okay, what I'd like you to do now is to consider this example, please.

So sea turtles reproduced by laying eggs in sand and the sex of the hatchlings depends on the temperature.

So at higher temperatures, more females are born, and at lower temperatures, more males are born.

And actually this is quite common across reptiles.

So what I'd like you to do is to suggest what effects climate change could have on the balance of sexes within the sea turtle population.

Then I'd like you to describe two ways that populations of sea turtles may be able to respond to help them cope with climate change before suggesting what might happen to the sea turtles if they are not a able to respond to climate change in these ways.

So pause the video now and come back to me when you are ready.

Okay, let's consider your responses.

So firstly, I asked you to suggest what effect climate change could have on the balance of sexes within the sea turtle population.

And you might have said that increasing temperatures will cause more females to be born than males, which is going to skew the sex ratio within the population towards females.

Then I asked you to describe two ways populations of sea turtles may be able to respond to help them to cope with climate change.

And you might have said firstly, that they could migrate.

In other words, they could move to places where the temperatures remain more suitable, which enables them to maintain a balanced ratio of males and females.

Or they could adapt.

They could evolve to suit higher temperatures with advantageous variations, which would become more common through the process of natural selection, for instance, adaptations, which will allow males to be born at higher temperatures.

And then I asked you to suggest what might happen to the sea turtles if they are not able to respond to climate change in these ways.

And you might have said that sea turtles could become extinct due to a lack of males being born if they cannot migrate to habitats with suitable temperatures to maintain a balanced ratio of males and females and if they cannot evolve quickly enough to allow to be born at higher temperatures.

So just check over your work, make sure you've got the correct answers and well done indeed.

So let's move on to the last part of our lesson today, which is about how we can protect against species loss.

So we've heard a lot of very negative stories in our lesson today of quite significant changes happening to many different species across the globe.

But it's good to know that we can all take actions in our lives to help reduce the top causes of extinction.

So for instance, we can talk about the issues and what we can do to help them.

And this is useful, it helps because it helps to prompt others into taking action, which means that your efforts are multiplied.

We can also provide and protect habitats where we live.

And this is really useful because this maintains the populations of plants and pollinators and other animals local to you.

And if we all did that, then many species and populations would be protected.

We can also choose to eat less meat and reduce food waste.

Now this is helpful because it reduces agricultural emissions and land use.

And in fact, reducing the amount of meat we eat is particularly useful here.

We could also choose to travel sustainably without burning fossil fuels.

Use an electric car, travel by train or bus or other public transport, for instance, and fly less frequently, always of travelling more sustainably.

And this is important because it helps to reduce emissions, helps to reduce the amount of carbon dioxide and other greenhouse gases being put back into the atmosphere.

And we could also use less plastic and produce less waste.

And this is useful because it reduces emissions and other pollution, both of which are causes of extinction.

So there are many, many things that we can do as individuals to help reduce extinctions and help reduce the impact of climate change.

And maybe you can consider some of those that you might be able to do in your life.

Now, farmers and scientists can also take action to help protect species from extinction by climate change.

For example, they can use this process called selective breeding.

Now many crops that are produced around the world have been selectively bred by humans to grow well and produce high yields of crops within the current conditions.

Now this means that they are adapted to grow within a very specific and narrow range of conditions and not necessarily conditions that are more common now through climate change.

However, wild varieties these crops such as wheat also still grow, and they are able to cope with a much wider range of conditions.

So farmers and scientists can use the process of selective breeding to produce new commercial varieties of variety of crops from the wild varieties, which would be better adapted to warmer drier conditions.

Another way that we can help protect against species loss is through the use of gene banks.

Now gene banks are specialised facilities where genetic material from endangered species can be stored and then used subsequently within breeding programmes.

So this is a bit like an IVF egg freezing facility for all of the species across the world rather than just for humans.

And you can see in the photo there, the Svalbard Global Seed Vault based in Norway.

Now genetic material from plants can be stored as seeds, whereas genetic material from animals can be stored as egg cells, sperm cells, which are frozen in liquid nitrogen.

And these gene banks offer a last resort protection against extinction of endangered species.

So let's go back and have a look at selective breeding because this is relatively common, and it's also an important part of the biology curriculum.

So let's see, how would we describe how to selectively breed wheat that is more tolerant to higher temperatures.

Well, firstly, we would choose two wheat plants that have good tolerance to higher temperatures.

We only want to breed the plants which are already showing that they are well adapted to those conditions that we are after.

We would then crosspollinate those two wheat plants together and then select the most tolerant offspring from the seeds that germinate.

And then we would cross pollinate those seeds and continue that, repeat that generation after generation after generation until we have all seeds demonstrating high tolerance to the higher temperatures.

So that's how we would selectively breed wheat.

What about selectively breeding frogs that are more tolerant to higher temperatures? So use the example on the left, and work out how we would do that for frogs.

I'll give you a few moments to think about it, but you may wish to pause the video to have longer to do.

Firstly, you should have said that we are gonna choose two frogs that have good tolerance to the high temperature conditions.

Then we're gonna breed them together.

Then we're gonna select the most tolerant offspring and breed them together, and continue that for several generations until all of the frogs are tolerant to the higher temperatures.

Did you get that correct? Well done if you did.

Now, to finish off our lesson today, what I'd like you to do is to consider this final example.

Firstly, understand that billions of people depend on maize as a staple food.

Now, commercial maize, sweet corn produces a high yield of edible corn, lots of edible corn, but it dries out and dies during drought.

It is not drought tolerant.

However, wild maize which produces low yields of edible corn has deeper roots, and therefore is more tolerant of drought conditions.

So what I would like you to do is to explain how selective breeding could be used to produce a new variety of commercial maize that has a high yield of edible corn, and is more tolerant to drought caused by climate change.

So pause the video, consider that, and come back to me when you are ready.

Okay, let's review your work.

So I asked you to explain how selective breeding could produce commercial maize that has high yield and is drought tolerant.

And you should have said that, firstly, we will pollinate commercial maize, which produces a high yield with pollen from wild maize, which has deep roots for good drought tolerance.

So we are going to cross breed commercial maize with wild maize.

Then we're going to select the offspring, which has the best combination of these two characteristics and pollinate them with pollen from either the wild maize or the commercial maize.

We're gonna keep breeding them together, breeding them together.

And we're gonna repeat that over several generations until all the offspring produce high yield and have deep roots for good drought tolerance.

So just review your answer.

Have got that? Well done if you have.

Okay, we've come to the end of our lesson today.

So thank you very much.

I hope you've enjoyed it.

We've seen in our lesson today how variation within a species affects how well different individuals can survive when environmental conditions change, and how this leads to natural selection of individuals which are better adapted to survive and reproduce in the conditions that they are living in.

And the species evolves over time as these individuals characteristics become more common over generations.

We've also seen how climate change could result in natural selection of individuals that are more tolerant to conditions such as drought or high temperature.

We've also seen how some species may not be able to migrate or evolve quickly enough to keep up with climate change, and how this could lead to the extinction of some species.

But we also have learned that humans can use a variety of methods to help protect against species loss due to climate change, such as selective breeding and the process involved in that.

So I hope you've enjoyed our lesson today.

Thank you very much for joining me, and for working so hard today.

And I hope to see you again soon.

Bye.