Lesson video

Hello there and welcome to this lesson from the Oak National Academy.

Today's lesson is taken from the unit Adaptations, competition, natural selection and evolution, and it is called heritable variation.

We're gonna talk today all about the differences that exist between us and where those differences come from.

Hi there, I'm Mrs. Wheate, and I'll be taking you through today's lesson.

By the end of today's lesson, you'll be able to describe examples of different types of variation that can and cannot be passed on to an organism's offspring.

Let's look at our keywords.

We have five keywords for today's lesson.

We have variation, environmental variation, genetic variation, offspring, and heritable.

Let's have a look at our definitions.

So before I show you the definitions, please don't feel like you need to rush and memorise all of them now, take your time.

If you wanna take five seconds or you can pause the video, then you can read through them at your own pace, or you can write them down if that helps you, so you can refer back to 'em later.

So here they are.

Today's lesson is in two parts.

First of all, we'll talk about environmental variation, which are the differences between us that are caused by our surroundings, and then we'll talk about genetic variation, which are the differences between us that are caused by what we inherit from our parents.

But first of all, environmental variation.

Individuals of the same species can be very different.

Have a look at my three photos here.

I've got three examples of breeds of dog.

They are all the same species, but they are so, so different.

We've got a Bulldog, a Chihuahua, and a Great Dane.

Have a think about just some of the differences between these three different dogs.

You can take five seconds now, or you can pause the video and give yourself a bit more thinking or discussion time, and then click play when you're ready to hear some of our ideas.

There's so many things you could have said.

You could talk about sizes, the Chihuahua being the smallest, the Great Dane is by far the biggest, the Bulldog being somewhere in the middle.

You could have talked about the type of fur they have.

The Chihuahua is a lot more hairy than the other two.

You could have talked about muscle mass.

The Chihuahua, again, is a bit weedy.

The Bulldog and the Great Dane have a lot more muscle.

You could have talked about their ears, you could have talked about their tails.

There's so many differences between these three individuals of the same species.

These differences are known as variation, which we'll be talking a lot about today.

The differences between individuals that is caused by the environment is known as environmental variation.

Have a look at this photo.

Is there anything in it or that the photo reminds you of that's something the environment that could influence how an organism is, what it looks like, how it acts? Take five seconds or pause the video to give yourself some more thinking time.

Click play when you're ready to see the answer.

Okay, let's have a look at the types of things that you could have said.

So the environment is the surroundings of an individual organism, such as temperature, sunlight, pollutants, availability of nutrients, there we go, or soil pH.

There's lots of things as well that you could have said that would also count as environmental variation.

So don't worry if what you said isn't on the list.

We're gonna look at some examples of environmental variation and how they can affect an organism.

So for turtles, temperature, an environmental factor of eggs, controls the sex for many turtle species.

So if turtle eggs are kept at colder temperatures, then the eggs will be born as male offspring.

If the eggs are kept at higher temperatures, then the eggs will be born as female offspring.

Isn't that interesting? So the temperature is the environmental factor, and that's causing environmental variation that's changing, causing differences between the sex in the eggs.

So in this example, the environmental factor is water.

So lack of water causes plants like this herb to wilt.

So that's why the plant's looking very sad and droopy.

It is wilted.

So the environmental factor water has caused wilting, which is the variation in this plant.

A plant that had enough water would be a lot more upright and look a lot more happy.

So another example is sometimes we get damaged by our environment.

And in this example, that has caused a scar.

So a scar is something that has caused by environment, that causes us to be different from each other.

We each have different experiences of life, have different amounts of damage and injury, and some of us have scars, some of us don't.

And we could also have scars in different places.

Let's look at this example example with flowers.

So in this example, the environmental factor is soil pH.

Now remember, the word pH is to do with how acidic or how alkaline something is.

So this is about the soil.

So soil pH controls this hydrangea flower colour.

So if these flowers are planted in acidic soil, they'll grow blue.

If they're grown in more alkaline soil, they will grow pink and red.

And anything in the middle, neutral soil, you can get pink or you can get blue, or you can get purple as well.

Isn't that interesting? So for most flowers, flower colour is actually controlled by their genetics.

We'll talk about that in the next section.

But a specific example of environmental variation is the hydrangea flower, which is not controlled by what its parent's plant looks like.

It's controlled by the soil pH.

Some variation isn't just caused by our environment and the experiences that we have just walking around in the world.

It's caused by choices we make, and we call that a variation that's caused by lifestyle.

So the lifestyle of a person is the thing that they do and the choices they make, such as diet, exercise, and modifying their bodies.

And in biology, we're not really talking about cat or dog lifestyle.

This is really just applying to humans.

If we look at my examples, we've got someone getting a henna tattoo.

Again, that's a choice they made in order to make their skin look like that temporarily.

Someone's got a body piercing, an ear piercing, and someone is exercising.

Exercising is interesting, 'cause it changes not just what our bodies can look like.

Obviously it can increase our muscle mass and reduce the fat percentage we have in our body that makes us look different.

But on the inside as well, it changes our cardiovascular fitness and things like that.

So there are changes there, but maybe we can't see them, variation there, but we can't necessarily see all of the effects of exercise.

Something really important to note about environmental variation is that variation caused by environment or lifestyle cannot be inherited.

So if I got a tattoo and I had a baby, the baby wouldn't be born with a tattoo.

If I go to the gym and work really, really hard and get absolutely ripped with really, really strong, tonnes of muscle, that I'm not gonna have a super strong baby.

That's not how it works.

Can you look at this example of a mother and child and spot something that the mother has that's not gonna be passed on to her son? You can take five seconds or you can pause the video if you need a bit more thinking time.

Okay, did you spot it? So the thing that I noticed was the mom has got an ear piercing here.

The baby does not have an ear piercing.

So that's an example of variation that's caused by lifestyle that's not passed on from parents' offspring.

That's not inherited.

You could have maybe talked about hair, I don't know, maybe this person's hair looks dyed to you.

We can't really be sure about that, but kind of something that we can definitely tell is looking at the body piercing.

Okay, let's see if we understood that.

Complete the sentences about variation.

Use the words from the list.

Scar, environmental, lifestyle, inherited.

The differences between individuals that are caused by environment are known as blank variation.

Having a blank is an example of this type of variation.

Building muscle by exercising is an example of variation caused by blank.

Neither of these types of variation can be blank.

So you'll need to pause the video now to give yourself enough time in order to answer these questions.

Click play when you're ready to see the answers.

Okay, let's have a look.

The differences between individuals that are caused by environment are known as environmental variation.

Having a scar is an example of this type of variation.

Building muscles by exercising is an example of variation caused by lifestyle.

Neither of these types of variation can be inherited.

Great job if you got that right.

Well done, you've made it to the first practise task of today's lesson.

Let's have a go.

Below are three statements about inheritance and variation.

For each statement, state whether they are true or false, state what the variation is caused by, and explain why the statements are true or false.

Okay.

Parents with high muscle mass will definitely have children with high muscle mass.

If a parent has a scar, their child will be born with a scar.

A parent with a tattoo will not have a child that is born with a tattoo.

So you'll need to pause the video now to give yourself some time in order to think about these and write these down.

Click playing when you're ready to see the answer.

Good luck.

Okay, let's see how you did.

So parents with high muscle mass will definitely have children with high muscle mass.

This is false, having high muscle mass is an example of a variation caused by lifestyle as it's caused by exercise.

Variation due to lifestyle is not passed on from parent to child.

Okay, next one.

If a parent has a scar, their baby will be born with a scar.

This is false.

Having a scar is an example of environmental variation as it is caused by injury.

Environmental variation is not passed on from parent to child.

Okay, last one.

A parent with a tattoo will not have a child that's born with a tattoo.

This is true.

Having a tattoo is an example of variation caused by lifestyle.

Variation due to lifestyle is not passed on from parent to child.

Great job if you got those right.

We've completed the first part of the lesson.

We've talked about the variation that's caused by environment, and now we're gonna talk about the differences between us that's caused by our DNA or our genetic material, genetic variation.

Not all variation is caused by the environment or lifestyle.

Some variation is caused by an organism's genetic material.

This is called genetic variation.

So genetic variation is heritable, as it is caused by instructions stored in the genetic material passed on from parent to offspring through reproduction.

So in humans and mammals, that's DNA, we get half of our DNA from our mothers and half of our DNA from our fathers.

If I take myself as an example, my mom is Black, she's from Jamaica, my dad's White, he's White British.

And so my skin colour is caused by a combination of my parents' DNA.

If we look at another example, I wear glasses.

Both of my parents wear glasses, we're a family with very, very poor eyesight.

So again, that variation in people, whether you wear glasses, whether you don't, can also be caused by genetic variation, by what your parents have and how they pass that on to you.

If we look at my examples on the screen here, I've got a parent spider plant and their offspring.

And so spider plants can be different colours.

They can have different kind of stripes on their leaves called variegation.

And again, that's caused by what the parent spider plant look like.

We've also got some lions down there.

We've got a male lion and a female lion and they've had a cub.

And again, that cub will be a combination of their parents' DNA.

They'll look a certain way, they'll act a certain way, because not just 'cause of their environment, but also because of what their parents look like and their parents' genetic material.

This is just a quick summary of genetic material, so we are all on the same page.

So genetic material is a chemical substance.

It's made of DNA.

It's found in the cells that all organisms are made of.

So here we have an animal cell.

So the genetic material there is stored in the nucleus.

We've got a plant cell, again, it has a genetic material.

It's DNA stored in the nucleus.

Bacteria do have genetic material, but they don't have DNA.

They have something slightly different, which we don't need to get into now, but they have the genetic material kind of floating freely in a loop in the cytoplasm.

Genetic material stores instructions for building organisms and for life processes such as growth and respiration.

And as I've just said as well, the genetic material is responsible for a lot of the differences, the variation between different organisms, how we look, how we act, what we like, what we want to do, in part that's controlled by our genetic material as well.

Let's check how we're doing.

Which of these is the primary reason that this father and child had the same skin colour? Is it A, they have a similar environment, B, they share genetic material, or C, they have a similar lifestyle? Take five seconds or pause the video to give yourself extra thinking time.

Click play when you're ready to see the answer.

Okay, it is B, they share genetic material.

So you might have said A, they have a similar environment and they probably do have a similar environment based on what we can guess from this photo, but that's not the primary reason that they would have the same skin colour.

Environment can control skin colour depending on how much we're in the sun.

That can change our skin colour slightly, but it's not the main reason that we have the skin colour we have.

Again, you might have said lifestyle.

This baby is very unlikely to be out at a tanning bed or tanning on a beach.

So I see maybe why you put that one.

But the most correct answer is that they share genetic material.

There's a father and their child, the offspring.

And so this child has half of the father's DNA.

Well done if you got that.

We're gonna look at some examples now of genetic variation between organisms. There's so many things that we could have picked, but these are just a few examples to give you an overview of the differences that exist and how they're controlled.

So, whether or not your ear lobes are attached at the bottom, funnily enough, that's controlled by your genetics, your DNA.

So everyone now is probably either looking at the person next to them ears or touching their own ears to be like, "Do I have attached or detached ear lobes?" You might not have thought about this very much before, but weirdly that difference is controlled by our DNA.

So have a look now.

If you're in your room by yourself, maybe pause the video, go look around your family or whoever you've got at home.

What kind of ear lobes have we got going on? Okay, another perhaps less weird example is our blood type.

You might have heard that blood comes in different kind of types for human beings.

So it's to do with the proteins that you have on outside of red blood cells.

So you can have A proteins, you can have B proteins, you can have A and B proteins of which your blood type is AB, or you can have no proteins, none of these specific type of proteins on the outside of your red blood cells.

And then you would be O.

You might have also heard of negative and positive types of blood type as well.

So yeah, all of that is controlled by our DNA.

So for example, my blood type is B positive, which I love, because it's a catchphrase as well as a blood type.

So my dad also has B positive blood type.

So that's where I get that and that's where it comes from.

So we have a look at a non-human example, fur colour in lots of animals, that's controlled by the genetics as well.

There could be a combination of what does the father of these animals look like? What does the mother of these animals look like? And then that'll be expressed differently in all of the offspring.

Another perhaps weird example, whether you can digest milk.

So you might have heard of lactose intolerance that some people can't digest the sugar inside lots of dairy products called lactose.

That's whether you have this enzyme on your body called lactase.

And that's pretty much, that's controlled by your genetics.

You either have this enzyme or you don't have this enzyme.

And that means you can either, you can drink milk, you can enjoy milk if you like the taste of it, or it really upsets your stomach, it doesn't work with you.

It's 'cause you might not have this essential enzyme that you need.

And that's just controlled by your genetics, by your DNA.

So only features that result from the instructions in an organism's genetic material can be inherited.

We'll look at some examples.

So the petal shape of flowers or your natural eye colour.

I know you can wear colour contact lenses and that changes your eye colour, but you can't change your natural eye colour.

I was born with brown eyes, I have brown eyes.

Even if I put on blue contact lenses, my natural eye colour is brown.

So petal shape and eye colour are inherited, because they result from instructions in their genetic material.

My mom has brown eyes.

I inherited that from my mom.

That's in my DNA, I can't change that.

So damage is inherited.

Sorry, damage is not inherited, because it results from the environment or lifestyle.

So again, if one of my parents had a scar, because they fell off a bike as a kid, I don't have that specific scar.

Like, I wasn't there.

I wasn't in that environment when my parents fell off a bike, yeah? So things that we do to our bodies during the course of our childhood and our adulthoods, the vast majority of 'em, they don't affect the variation that we can pass onto our offspring.

Hopefully that made sense, let's check and see.

So which labelled features of the adult tiger could be passed down to its cub? So the tiger's got green eyes, it has a scar, it has a a torn ear and it has orange and black fur.

Which of these features could be passed on to the cub? Pause the video if you need a bit more thinking time, you'll have five seconds.

But if you want longer, pause the video, and then click play when you're ready to see the answer.

Okay, let's have a look.

So, the features that could be passed onto its cub.

So green eyes, that could be passed onto the cub, that's caused by instructions in our DNA, our genetic material.

And orange and black fur, that could be passed onto our cub as well.

The scar and the torn ear.

Those were caused by damage that the tiger has accrued during its lifetime, maybe by fighting, but those won't be passed onto the cub.

It got those scars, it got that damage from being in its environment, not through something in its DNA, causing it to be like that.

Well done if you got that right.

So just to actually make things even more complicated, most traits are caused by a combination of genetic, environmental, and lifestyle factors.

Very few traits actually fit neatly into just being an example of something being caused by genetic factors, something that's just caused by environmental factors.

Most things are a combination of all of them.

Let's look at an example.

So body mass is partly controlled our genes.

So partly our body mass will be determined by the DNA we inherit from our parents, but it's also influenced by our lifestyle.

Depending on what we eat and how active we are, our body mass will change.

You could also argue it's a result of our environment as well.

If you live right next door to somewhere that sells really cheap fresh fruit and vegetables, that's probably going to lead you to having a different body mass.

If you live somewhere that's just only exclusively sells chocolate and crisps, you're probably gonna have a different body mass.

So that's in your environment, you can't massively control that.

So our body mass, yeah, it's not as simple as just being exactly the same type of bodies that our parents have or exactly what's just an environment.

It's a combination of all of them.

Okay, let's put that into practise, see if we can figure out some of these examples.

So for each of the following features, identify whether they are caused by genes, environmental lifestyle, or both.

So natural hair colour, size of plant, nose piercing, natural eye colour, your hair colour or style, your height, your accent, your muscle mass.

For each of those, identify whether it's just controlled by your genes, whether it controls your environment and lifestyle.

That's kind of one category, or whether it's controlled by both of those things.

You can take five seconds or you can pause the video to give yourself some extra thinking time.

Click play when you're ready to see the answers.

Good luck.

Okay, let's have a look at some of those answers.

So natural hair colour, that is controlled by your genes.

Size of a plant, that's controlled by both.

So the size of the plant determined in part by the genes that it inherits from its parent plant.

So if it's a big parent plant, it's likely to be a big offspring plant, but it's also determined by its environment, right? So if the offspring has been planted somewhere that has very little sunlight, it's not gonna get, do enough photosynthesis, not gonna make enough glucose, it's not gonna grow very big.

So that's why it's a combination of both.

Whether you have a nose piercing or not, that's controlled by your environment, your lifestyle.

You choose to go out and get a nose piercing, you want one.

You're not just born with one because your parents had one.

Your natural eye colour, again, that's controlled by your genes.

Your hair colour and style, that's controlled by both.

Again, whether you have curly hair or straight hair or what colour hair you have that's in part inherited from your parents.

But if you wanna change that, if you wanna straighten your hair, if you wanna curl your hair, you wanna change your hair colour, you can do that.

That's a lifestyle choice.

Your height.

So our height is about 80% heritable and that last kind of 20% of what contributes to your height is your environment.

What kind of nutrition that you're getting.

Your accent, are babies born with Liverpudlian accents or Glaswegian accents? No, that's a result of their environment.

Yeah, what you hear growing up determines what your voice will sound like.

And your muscle mass, that's an example of both as well.

You might have parents that are super into fitness and so that's the environment you grow up in.

So that's why you have high muscle mass.

It could also be part of your genetics as well.

But yeah, largely it's controlled by both.

Well done if you got those right.

Okay, so this is our final practise task for today's lesson.

Well done so far, we're nearly there.

Sam's cousin has just given birth to identical twins.

This means they have the same genetic material.

Sam and Aisha are discussing what the twins will be like when they grow up.

Sam says, "The twins will always be exactly the same, because they have the same genetic material." Aisha says, "Genetics isn't important.

As long as the twins grow up in the same environment, they will be the same." Decide if each person's understanding is correct and explain why or why not.

So you'll probably need to pause the video now to give yourself enough time to think about that and to write your answer.

Click play when you're ready to see the answers.

Okay, let's have a look.

Sam is correct in saying that the identical twins have the same genetic material.

She is wrong to say that the twins will be exactly the same as there will be environmental or lifestyle factors that will cause variation between them.

For example, one may be more interested in exercise, to have a higher muscle mass, or one might dye their hair or cut their hair off.

You could have put kind of any example like that, that would be credit-worthy.

Aisha is wrong in saying that genetic material isn't a factor in how the twins will develop.

The twins' features are determined by the genetic material, DNA, and all the lifestyle environmental factors they experience just like everybody else.

Well done if you got that right.

Great job with today's lesson.

Let's summarise what we learned to help it stay in our memories.

There are differences in the features of individuals of the same species, and this is called variation.

Some variation is caused by the environment such as having a scar due to injury.

Some variation is caused by lifestyle such as having a tattoo.

Some variation is caused by genetic information such as our natural eye colour or fur colour in animals.

Only genetic variation is heritable.

Variation caused by our environment or lifestyle is not heritable.

Amazing work today, everyone.

Go have a well-deserved break and I'll see you back again really soon for our next lesson.