Lesson video

Hello.

I'm Mr. Jarvis and I'm gonna be taking you through this lesson today.

Today, we are looking at impacts of environmental changes on the distribution of organisms, and this lesson forms part of the unit Maintaining Biodiversity and Human Impacts.

By the end of today's lesson, you should be able to evaluate evidence of the impacts of environmental changes on the distribution of organisms. There are five key words in today's lesson.

They are greenhouse gas, climate change, distribution, abundance, and biodiversity.

The definitions of these words are on the screen now.

You can pause the video if you want to read through those definitions for yourself now, but don't worry because we will go through them as we go through the lesson.

Today's lesson is broken down into two parts.

First of all, we're going to look at the changing conditions on the earth, and then we're gonna look at how those changing conditions affect the distribution of different species.

So if you're ready, let's get started with our first section, which is all about changing conditions.

The Earth's atmosphere has remained relatively stable for millions of years.

However, partly due to humans activities, the levels of carbon dioxide gas or CO2 in the atmosphere is increasing.

And here's some data in a graph.

It's from Mauna Loa in Hawaii.

And you can see since the levels of carbon dioxide in the atmosphere started to be recorded in 1960, the levels of carbon dioxide gas have increased in the atmosphere.

There are also seasonal fluctuations, which you can see by the lighter line, and this is because the plants use carbon dioxide in the summer when the temperatures are warmer and they grow really quickly and produce lots of leaves, and that reduces the amount of carbon dioxide in the atmosphere.

When it gets colder and the light intensity reduces, then they lose their leaves.

And when they lose their leaves, decomposers start to break down the organic material within them and that releases carbon dioxide.

And so during any one year, there are seasons which mean that the carbon dioxide concentration increases and decreases, but the overall trend is certainly upwards.

The earth receives infrared radiation, IR radiation from the sun.

Some of this radiation is reflected back into space.

Some of the infrared infrared radiation is absorbed by the Earth's surface and reradiated back into the atmosphere.

And the greenhouse gases in the atmosphere absorb and reradiate that infrared radiation, which has the effect of warming the atmosphere.

This is what we know as the greenhouse effect.

And the greenhouse gases include gases such as carbon dioxide, methane, and water vapour.

The greenhouse effect is useful up to a point.

It keeps the Earth warm enough for life to exist.

However, as the levels of greenhouse gases increase in the atmosphere, the greenhouse effect increases too.

And this is causing the mean temperature of the Earth's surface to increase.

This leads to climate change, and climate change has long-term changes in weather patterns.

So here's our first check of the lesson.

Which of the following are examples of greenhouse gases? A, nitrogen, B, oxygen, C, methane, or D, carbon dioxide? I'll pause for a few seconds and then we'll check your answer.

The correct answers are C, methane, and D, carbon dioxide.

Both of these are examples of greenhouse gases.

Well done if you got that.

Even small increases in the Earth's surface temperature can cause significant impacts.

This includes sea levels rising as a result of polar and ice melting or climate change, giving rise to severe and unpredictable weather events such as really intense storms and these storms taking place more frequently, more droughts, and more heavy rainfall and flooding.

As the Earth's surface temperature increases, the ocean temperature increases too.

And this results in more evaporation of water vapour into the atmosphere.

And remember, water vapour is a greenhouse gas, and so if there is more water vapour in the atmosphere, this is going to have the effect of warming the planet even further.

The increase in temperature also reduces the quantity of carbon dioxide that's dissolved in the oceans.

That means that carbon dioxide from the oceans is released and that then goes into the atmosphere, which again increases atmospheric carbon dioxide levels, which has the effect of increasing the greenhouse effect.

And so increasing the global surface temperature of the oceans means that we are enhancing the greenhouse effect further.

Changes to the environment can affect the distribution of a species, and distribution of a species is where they're located.

The main environmental factors that affect the distribution of organisms include temperature, the availability of water, and atmospheric gases in aquatic environments.

Here's a check.

Which of the following is not an abiotic factor that is closely linked to the distribution of species in an ecosystem? Is it A, increased mean temperature, B, a change in the availability of water, C, a change in the dissolved gases in aquatic environments, or D, the number of predators? I'll pause for a few seconds and then we'll check to see if you got the answer right.

The correct answer here is D.

The number of predators is not an abiotic factor.

Remember, abiotic factors are non-living factors that are linked to the environment.

Well done if you got that.

Climate change can have a significant impact on ecosystems. Changes in weather patterns can result in a change in the environmental conditions within ecosystems. And when conditions change, organisms that live there may be less well adapted to survive and may even become extinct.

And that was the case with the golden toad.

The golden toad lives in the mountain cloud forests in Costa Rica.

It was abundant in numbers in the mid-1980s, but then the ecosystem experienced significant climate change.

That the ecosystem became drier, there were droughts, and the rainfall patterns became later in the year.

And not only that, the rainfall became heavier at the start of the rainy season.

This meant that the shallow pools that the toad needed to reproduce in were no longer available.

The pools became much deeper and the heavy rains meant that many of the eggs and the tadpoles were washed away down the hillside.

And as a result of this, the species reduced in numbers quickly.

It was last seen in the early 1990s, and by 2004, it was declared extinct.

Species in polar regions are significantly impacted by climate change.

Here's an example.

Muskox live in the Arctic area and they have thick warm coats which they need to keep them warm in the cold arctic weather.

They find their food, which is lichens and mosses, by digging through the snow using their noses and their legs.

However, warmer temperatures mean that rain falls rather than snow, and the rain forms a thick layer of ice on top of the snow, and that means that the muskox are not able to break through that layer and feed on the lichens and mosses beneath the snow.

And the thick coats do not protect the muskox against heavy rain.

Once they're wet, the muskox gets cold and can even freeze to death.

Warming sea temperatures also impact species.

For example, during periods of stress, increased water temperature, corals expel the algae that live in their tissues and it's these algae that give coral their colour.

Without the algae, the corals look white or bleached.

And in this state, the corals are more at risk of starvation and disease, and as a result, the number of coral species are reducing where water temperatures have significantly increased.

Here's another check.

The population size of a species can be used to monitor changes in temperature of the environment.

What is the advantage of using a population rather than measuring the temperature with a thermometer? Is it A, thermometers can only record temperatures within a specific range, B, thermometers do not record temperatures accurately, or C, the population size will show long-term changes to the species? I'll pause for a few seconds, and then we'll check your answer.

The correct answer here is C.

The advantage of using a population is that the population size will show a long-term change to the species.

Well done if you got that answer correct.

That brings us to our first task of the lesson.

Adelie penguins spend most of their time on the ice in Antarctica.

The population of Adelie penguins has reduced by more than half in the last 60 years.

The ice around Antarctica has reduced in this same time, and you can see the map of the ice that surrounds Antarctica in two maps here on the screen.

Using this information, I'd like you to explain why the population of Adelie penguins has declined in the last 60 years.

You'll need to pause the video at this point, write down your answer, and then when you're ready, press play and we'll check to see how well you've done.

Good luck.

So how did you find that? I asked you to use the information to explain why the population of Adelie penguins has declined in the last 60 years.

And I've put the maps back onto the screen at the top here for reference as we go through your answer.

So your answer might have included that the penguins spend most of their time on the ice and there's been a reduction in the area of ice since 1960.

The reduction in the area of ice may be a result of increased sea temperatures caused by climate change.

And this means that there's less habitat for the penguins to live in.

For example, less places for the penguins to nest.

And the penguins may not therefore be as well adapted to the changing habitat.

Well done if you got that right.

That brings us to the second part of the lesson, and now we're going to look at the distribution of species.

So if you're ready, let's move on.

Climate change can have significant impact on ecosystems and the communities that live within them.

Environmental changes such as an increase in temperature, the availability of water, the concentration of dissolved atmospheric gases in aquatic environments can all result in a change in the distribution of species, where they're located, and the abundance of species, how many individuals there are.

Organisms have adaptations that allow them to survive within a range of different conditions, but as climate change takes place and the average temperature of the planet increases, the distribution, where you find species, and the abundance, the number of species changes.

And this affects the biodiversity of ecosystems. The picture shows an example of how some mountain plants have moved uphill by 10 to 50 metres as temperatures of the surface of the planet have risen.

And they're doing this because they're adapted to the conditions, and as the temperature increases at lower altitudes, they're having to move higher up the hillside to get the conditions that help them to survive best.

Here's another example.

The walrus lives on arctic sea ice and it uses sea ice as a diving platform to feed on the clams that provide it with food that are found on the seafloor.

They also use the sea ice to give birth to their young.

And as the ice is melting away from shallower water, the walrus is not able to find the food that it needs to survive.

Another example, other populations of birds.

Bird populations have declined in the UK.

This includes the kittiwake shown in the picture on the screen.

Kittiwake populations have declined by 29% since 2000.

These birds live around the coasts and feed in the shallow waters on sand eels.

But as those shallow waters have increased in temperature, the number of sand eels has also declined, and this means there's less food for the kittiwakes to eat, and that's being given as a reason for their decline.

Another example is how increasing temperatures impact migration.

Here's a picture of the European cuckoo.

Some birds migrate to take advantage of seasonal resources such as food.

Cuckoos arrive in the UK in spring and leave in the late summer to overwinter in Africa.

Climate change is reducing the availability of food, and this means that cuckoos are struggling to build up enough reserves to make the long journey of its migration.

And those that make the long journey are not then able to have as many chicks because they haven't had as much food as they did previously.

And so the cuckoo population is also declining.

Some species are moving as a result of changes in temperature.

We saw how some plant species were moving to higher altitudes in mountains where the conditions were cooler.

The wasp spider was originally found in Europe, and very, very rarely in the UK in very small numbers of spots that were sheltered on the south coast.

Over the past 20 years, the spider has moved up as far north as Derbyshire, and this is because the spider has been able to survive the warmer winter temperatures.

Let's move to a check.

As the average temperatures increase due to climate change, species distribution may change because, A, they're able to adapt to the changing conditions quickly, B, the organisms that they rely on for food may be impacted by the change in temperature, or C, the habitat in which the species lives may be significantly changed or destroyed.

I'll pause for a few seconds while you work out the answer and then we'll check to see how well you've done.

The correct answer here is B and C.

As the average temperatures increase due to climate change, species distribution may change because the organisms that they rely on for food may be impacted by the change in temperature and the habitat in which the species lives may be significantly changed or destroyed.

Well done if you've got both of those answers correct.

The availability of water is another important factor, which changes the distribution and abundance of species.

Changes in weather patterns as a result of climate change can alter levels of precipitation.

That's rain, sleet, and snow.

Some areas have reduced rainfall or even long droughts, and in places like Africa, long droughts can reduce the amount of water available and dry up water holes as seen in the picture on the screen.

Wildebeest migrate following the seasonal rains.

They're found in Africa, in Kenya and Tanzania.

You can see the map of Africa on the screen, and we're going to look in more detail of their patterns of migration through Kenya and Tanzania.

At the start of the year in January, you find these herds of wildebeest around the borders of Kenya and Tanzania.

They move south for the spring and then move back towards the border for the summer in June.

From June onwards, they move up north, and in the autumn they spend their time in Kenya following those seasonal rains.

That migration pattern takes the wildebeest around 1,000 kilometres in terms of total distance.

So it's a long and arduous journey, but it's worth it because they follow the seasonal rains, so that they're able to eat the fresh grass that grows after those rains.

And here you can see some wildebeest on the plains where there is some lush green grass to provide them with lots of food.

Good food and water is really important to allow them to make that long journey.

However, they have to cross some really dangerous rivers on that journey, as you can see in the picture on the screen.

And if the rainfall doesn't come or there's climate change, which means that the rains are seasonally at different times of the year, this means that good food isn't available.

Look at the graph showing the population of wildebeest.

You've got the population of wildebeest in thousands along the y-axis and the year along the x-axis along the bottom.

And I've also highlighted some periods of drought in green and periods of high rainfall, the El Nino, which is in the pink.

What do you think it shows? I'll pause for a few seconds so that you can have a look at the graph in a bit more detail and think about what that's showing.

Well, it shows that there are periods of drought that are increasing in frequency.

If you look between 1980 and 1990, there is one year of drought.

However, between 1990 and 2000, there were three and there were three between 2000 and 2010.

It also shows you that populations decline after droughts.

So a reduction in annual rainfall in areas where the wildebeest population migrate impacts the size of the population.

Well done if you thought to any of those.

Here's a check.

Why might the population of wildebeest decline during periods of drought? Is it A, there are more predators of wildebeest, B, there is less fresh grass for wildebeest to eat, or C, there are more water for wildebeest to drink.

I'll pause for a few seconds and we'll check your answer.

The correct answer is B.

There's less fresh grass for wildebeest to eat, and that means that the population is likely to decline because there's less food.

Well done if you got that.

So let's move to our final task of today's lesson.

Cetti's warbler is a small bird.

It was first seen in the UK in Hampshire in 1961.

It was first recorded as breeding in the UK in Kent in 1972.

The birds eat small insects.

Here are distribution maps of the species.

You can see the distribution of Cetti's warbler in 1975 and the distribution of the bird in 2020.

I'd like you to describe the change in distribution of the Cetti's warbler shown in the distribution maps.

And I'd like you to suggest why the distribution might have changed.

You'll need to pause the video at this point, write down your answer, and then when you're ready to check your answers, press play and we'll see how well you've done.

Good luck.

Let's see how you did.

I asked you to describe the change in distribution of Cetti's warbler shown in the distribution maps, and to suggest why the distribution might have changed.

You might have included in your answer that the bird's distribution has moved northwards and westwards since 1975.

As the average temperatures have increased due to climate change, the birds have been able to survive over winter and have successfully reproduced, and this has allowed the species distribution to increase.

You might have also said that the distribution of small insects that the bird feeds on may also have changed, which would've allowed the bird to move westwards and northwards too.

Well done if you got all or any of those answers.

That brings us to the summary of the lesson.

We've seen how greenhouse gases such as carbon dioxide, methane, and water vapour help to keep the Earth warm enough for life to exist.

And we've seen how increased levels of these greenhouse gases in the atmosphere can cause climate change, long-term shifts in weather patterns.

We've seen how even very small changes in ecosystems such as in temperature or water availability can have significant impacts on the distribution and abundance of organisms. And we've seen that the biodiversity of ecosystems may reduce.

Organisms that are not able to adapt to the changing conditions quickly enough may move or become extinct.

I hope you've enjoyed the lesson today.

It's been great learning with you as always, and I look forward to seeing you again sometime soon.

Bye bye for now.