This lesson is called Variation Within Species and is from the unit Variation Differences Within Species.

Hi there, my name's Mrs. McCready and I'm here to guide you throughout today's lesson.

So thank you very much for joining me.

In our lesson today, we're going to describe some examples of variation between individuals with the same species and explain what causes this variation.

We're gonna come across a good number of keywords in our lesson today.

I will introduce them to you as we go, but if you want to pause the video and make a note of them, please do so.

So in our lesson today, we're going to firstly look at species and variation before we look at the causes of this variation.

So if you are ready, I certainly am, let's go.

So we know that there is a huge variety of living organisms on earth.

In fact, some estimates put the number of unique species living on earth at nearly 9 million.

It's an absolutely incredible number.

And we can see that even in one specific ecosystem such as a rainforest, there are thousands of different species there and I'm sure plenty more that we haven't yet discovered.

Now we know that a species is a group of organisms that when they reproduce with each other they produce fertile offspring.

So that means that their offspring can themselves go on and have their own children.

So for instance, geese, when they reproduce together, produce babies and when they have matured we'll be able to go on and produce babies themselves.

Similarly with silver birch trees, they make baby silver birch trees, which when they grow up will be able to make more birch trees as well.

So let's have a think what is a species, I've just given you the definition, but which of these three explanations is correct? Is it A, a group of organisms living in the same habitat? Is it B, a group of organisms that can produce fertile offspring.

Or is it C, a group of organisms with identical features? I'll give you five seconds to decide.

Okay, so have you got your decision? Well, hopefully you have decided it's B, a species is a group of organisms that can produce fertile offspring, well done.

So we know that there are many more differences between members of different species than there are between members of the same species.

So let's just consider the picture and the giraffes and the zebras which are in there.

You can see that giraffes are one species, zebras are a separate species and there is quite significant differences between those two members of species.

There are certainly differences between them than there are similarities.

So let's just complete this sentence then.

Differences something species are greater than differences.

Something species use the words between and within to complete the sentence.

I'll give you five seconds to come back to me.

Okay, so did you put differences between species are greater than differences within species? I hope so, well done.

Now we know that differences between species are important and that provides this great variety on earth.

It also means that different species are able to live more comfortably in specific habitats and therefore all the various ranges of habitats on earth can be lived in by a variety of different organisms. So for instance, giant lilies are adapted to live on water, but you wouldn't find an orangutan living in water because they are adapted to live in trees.

So the variation that is present on earth is reflected in the differences within species and the adaptations that they have.

Now, differences between species is fair and obvious, but there are also differences between members of the same species and we call these types of differences variation.

So we can see in this group, in this photograph of the giraffes that there is variation just even amongst these four giraffes.

And variation can occur in height and other size differences, but also in strength as well.

Now the variation between members of the same species is really important because that means that members of the same species have their own strengths and weaknesses.

And this means that there is variation in the adaptation of those organisms. So let's say there is some awful event, some of those members of the species will survive, whereas others will not.

If they were all identical, it's very likely that they would all just die out and that would be the end of that species.

Whereas by having variation between each member, then hopefully some of them will survive, others might not, but the species itself can carry on and this is really important.

So let's have a think about this question.

There will be more differences between these cats in the photograph than similarities, true or false? Well hopefully you've said false to that, but why can you justify your answer with one of the two sentences below? So hopefully you've justified your answer by saying that members of the same species show more similarities and fewer differences.

Well done.

And let's have a think about this question.

Which word describes differences between members of a species? Is it fertile, habitat, variation, or variety? What do you think? I'll give you five seconds.

Okay did you choose variation? Well done.

So what I'd like you to do now is to choose an organism that you are familiar with.

So maybe a pet, for instance, cat, dog, horse, snake, fish, or maybe a flower, if you are very good at nurturing plants.

Choose an organism, perhaps a specific one that you can really visualise in your mind and then create a map, a mind map of all the features that make that one individual different from other members of its species.

So if you've chosen a cat, choose your house cat and compare it to any other cat in the whole wide world.

Consider behavioural and physical characteristics.

So I have included that my pet has black socks fur on its feet, it's about 30 centimetres long.

It has a scar on its ear, it likes hiding behind rocks.

They're the kind of ideas that I've come up with.

So you stop and think about your ones come back to me when you are ready.

Okay, let's have a look then.

So with my pet, I've said that it's got white fur on the tip of its tail.

It's got a scar on its leg, it has a short twisted tail.

It likes hiding in bags, it likes sweet food, which is, I have to say, very peculiar for a cat and very irritatingly, it meows for everything except for wanting the door open, which you would think that it really need to meow the most for, but it doesn't, it claws the carpet instead just typical.

So hopefully you've got some good ideas for your animal, whatever it, or plant, whatever it is that you've chosen.

Well done.

Okay, so let's have a look at what causes this variation.

We've seen that there is great variation, but why does it occur? So there are lots of different reasons why variation happens.

Some of it is caused by the environment.

For instance, our skin darkens and our hair colour lightens if we stay in sustained bright sunlight.

Some species, and this is fascinating, turtles and crocodiles for instance, their hatchlings if they have been incubated at a very low temperature, are all male.

Whereas if the temperatures are wee bit higher by only a few degrees, then they'll all be female.

Interesting, huh? And you've probably observed that plants grow taller in shadier conditions so that they can get up towards the light.

And plants growing in bright sunlight don't need to worry about that.

So they'll maintain a more modest height.

Other variation is due to lifestyle.

For instance, humans.

Well, we know that we are what we eat to many, in many respects.

And the amount of food that we eat with the kind of food that we eat, the exercise that we do, whether we smoke or drink alcohol, all these sorts of things will significantly affect the appearance of us and our general physical health as well.

We'll also see out and about in the environment that stags for instance, often have scars on their body where they have bashed into each other in rough fighting called rutting.

And goldfish interestingly, grow to the size of the container that they're kept in.

So if you keep a goldfish within a very small aquarium, then their body will be much, much smaller than if you were to put them into a large pond for instance.

The same fish will grow to be a much larger size in a much larger environment.

Other variation is caused by genetics.

And obviously these genetics, this is what we are inheriting from our parents.

So for instance, our blood type might be either A, B, AB, or O, but it's one, or the other, or the other, or the other.

And there's no variation in between and this has come from our parents.

Similarly, our eye colour is something that we have inherited from our parents.

The ability for us to roll our tongue and you can see in the picture the girl there is puckering her tongue, the pulling it up into a real pinch point.

So some people can do that and other people can't.

And again, that is genetic.

And then other conditions such as cystic fibrosis and down syndrome, these are genetic conditions which are inherited from genetics that we've received from our parents as well.

And these examples are all features that are only caused by genes by the genetic information that we have within our body.

So quick check for understanding all variation is caused by in the environment.

True or false, what do you think? Okay, so hopefully you've said false for that, but why, try and justify your answer.

So hopefully you've justified your answer by saying that some variation is caused by genes and others caused by lifestyle.

Well done.

Now most variation is caused actually by a complex combination of genetics, environment and lifestyle factors.

So it's not clear cut really, which one specifically has the greatest influence they'll all be a combination.

For instance, asthma is significantly genetic but also is impacted by the environment.

For instance, air pollution.

So if you have inherited genetic component for asthma, but you are living a really clear and clean environment with no air pollution, then your cases of asthma, the number of asthma attacks for instance that you have are likely to be much less than you would've had if had you been living in a city where air pollution is likely to be much, much worse.

Height is also affected by genetics, but it is also amended by the diet that you have as a child.

So if you live somewhere where you have a very poor diet, then your height is likely to be restricted and less than it would've been had you lived in a very, in an area where there was a very rich diet and you could have had a very plentiful supply of various different types of food.

So have a look at the plant.

There's this drawing of a plant and parts of it have been labelled.

It's tall stem, it's green leaves, it's white petals and some insect bites that have been taken outta the leaf.

And what I'd like you to do is use the words all, some or none to complete the sentences.

So something of a plant's features are caused by genetic information in cells.

Something of a plant's features are caused by its environment and something of a plant's features can be changed by environment.

So all, some or none, what do you reckon? Come back to me in a few seconds time.

Okay, so did you put some of a plant's features are caused by genetic information.

Some of a plant's features are caused by its environment and some of a plant's features are changed by its environment.

Did you use that word only? Well done.

So what I'd like you to do next is to complete a table showing genetic environment and lifestyle only features and then any features which are a combination of two or more of those.

So really think very broadly about that and you can put down whatever you can think of that fits into those four categories.

Then once you've done that, I'd like you to explain to me why identical twins do not look identical by the time they are 60 years old.

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

Okay, so in the first task I asked you to complete the table to list various human features which are controlled by genetics, or environment or lifestyle, or a combination of all three.

So in genetics only, you might have included things like blood type, whether you can tongue roll, whether your earlobe is attached or unattached.

And then genetic diseases like cystic fibrosis and down syndrome.

I'm sure you've got a few other ideas there as well.

Within environment only, you might've included how tanned your skin looks, whether you've got any injuries or scars.

And in lifestyle only, you might've included things like piercings, tattoos, makeup, hairstyle, things like that.

I'm sure you've also added other things into those lists too.

And then in combination of two or more of those things, you might have included ideas like weight, height, general health, things like asthma and general immunity.

So the ability to resist certain diseases you might have been more specific about that.

So just have a look over what I've put.

How does that compare to what you've included? I'm sure you've got plenty of other things that I haven't included that you have so well done.

Add anything that you might need to.

And then let's consider the second question, explain why identical twins do not look identical by the time they are 60 years old.

So this answer you might have included things like the fact that identical twins have the same genetic information and therefore many features will be identical such as their blood type and any genetic conditions that they have.

However, the effect of the environment and their lifestyle on their appearance will have been significant over time.

By the time they get to the age of 60, that's a lot of time that has passed to have the effect on them and therefore they will look different because of the impact of the environment and their lifestyle choices.

For instance, one of the twins might eat less healthily and might smoke, and therefore be overweight and have stained teeth and fingers when compared to their twin.

You might have given some other examples and maybe you've said another, a few other bits and bobs, just review your answer over, make sure you've got all the key salient points.

And well done again that was quite a challenge.

Okay, so in our lesson today we have seen that there is greater difference between different species than there are between members of the same species.

And that differences between members of the same species is called variation.

We've also seen how variation is caused by many different factors.

For instance, the environment, injuries for instance, lifestyle such as your weight and genetic factors such as your blood type, are all examples which generate variation between individuals in different ways.

We've also seen how actually variation is the result of many of these factors working together over the course of the lifespan of the organism.

So I hope you've enjoyed our lesson today.

These lions certainly look like they have done, they look very chilled, don't they? And I hope to see you again soon.

Take care, bye.