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

Hi there.

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

So, thank you very much for joining me.

In our lesson today, we're going to have a look at why offspring look similar, but not identical, to their parents and each other.

We're gonna explore why that is the case.

In our lesson, we're gonna have a look at a number of new words, a number of important keywords, and they're shown on the screen now.

I will introduce these to you as we go throughout the lesson, but if you'd like to pause the video and make a note of them, please do so now.

So, in our lesson today, we're going to have a look firstly at species and family resemblance.

Then we're gonna have a look at DNA and inheritance, before looking at how variation occurs.

So, are you ready? I know I am.

Let's go.

So, species, just to remind you, is a group of organisms that, when they reproduce, they make offspring that can themselves go on and reproduce.

In other words, they are fertile.

So, their children are fertile and can make more species, more members of the species.

And all of those offspring are members of the same species.

They don't change the species just because they've had children or because they have been born.

So, chimpanzees reproduce to make more chimpanzees, geese produce geese, and wild boar produce wild boar.

And I'm sure that is a concept that you are very familiar with; this idea of reproduction making more members of the same species.

And that's a really critical feature of the term species, that the reproduction process makes fertile offspring.

Now, the offspring, so the children, share characteristics with other members of the same species.

And these similarities, these resemblances are called species resemblances.

So, for instance, goldfish.

So, all goldfish have the same sort of body shape, and they live in fresh water; whereas cows, for instance, they all need roughly the same diet, and they share very similar facial and body shapes with each other.

So, these resemblances, these characteristics, are common to the species.

It doesn't make each organism identical to each other, it just gives them a set of shared ideas, shared characteristics that they can share.

When you look at individual families, then offspring, so children, you will see that they share characteristics with their parents and with any other siblings that they might have.

And these shared characteristics are called family resemblances.

So, if we look at these families, we can see that the children both resemble their parents and each other, but they don't look identical to either parent; neither do they look identical to each other.

Similarly, with this dad and his daughter, they share characteristics; she has resemblances to him, but she is not identical to her father.

So, there is family resemblance.

You can see which members of the family, who's related, roughly there or thereabouts to each other.

But you can also see the species resemblance as well.

And none of them are identical to each other.

So, these two girls, Laura and Sofia, are having a discussion about family resemblance and species resemblance, and they've got their definitions here.

But what I'd like you to do is to match the term to their definition.

So, Laura says, "Organisms look like other members of their species, as they have similar characteristics to each other." Whereas Sofia says "Children look like their parents, and they are similar to their grandparents.

You can tell who is related to each other." But which definition is describing which term? So, pause the video for about five seconds, and come back to me when you're ready.

Okay, so have you got your decision? Well, Laura, her definition is for species resemblance; whereas Sofia, her definition is for family resemblance.

Did you get those right? Well done if you did.

Excellent job.

What I'd like you to do now is to look at these two dogs, Skippy and Bouncer, in quite a lot of detail, and then draw a Venn diagram, as on the left of the screen, where you can show the similarities in the overlap sections in the middle and the differences between the dogs in the sections on the outer sides.

So, have a look at the dogs in relative detail.

They're from different families, but they are of the same species.

And how are they similar? How are they different? So, pause the video and come back to me when you're ready.

Okay, so let's have a look at what you've maybe put down on your sheet.

So, comparing Skippy to Bouncer, you might have said that Skippy's ears point up, whereas Bouncer's ears flop down.

You might have said that, whilst Skippy has just white fur, Bouncer has white fur with black sections.

And you might have been a bit more specific like black ears, for instance.

And you might have said that Skippy's fur is short and straight, whereas Bouncer, yes he has short fur, but it's also curly as well.

So, it's not straight like Skippy's.

Whereas, with shared characteristics, they've both got short legs, they've both got a black nose, they both have teeth which are similarly arranged, and they've both got a very similar body shape.

Now, I'm sure you've included many other things besides those.

So, just check your work and make sure it actually makes sense, add anything that you want to.

And well done.

That was quite a lot of detailed observation to do.

Good job.

So, let's move on and have a look at DNA and inheritance.

So, we know that there is variation between organisms of the same species.

We've just been discussing that; these species and family resemblances means that they look similar to each other, but they are not identical.

So, there are differences in their features because there is variation.

So, for instance, there is variation between the offspring of these boar, and there is variation also between the parents and their offspring, such as in these rhino.

So, we can see that there is similarity, but there are also many differences.

Now, we know that offspring share characteristics with their parents because they inherit characteristics from them, and you inherit characteristics via DNA.

So, DNA are instructions, and those instructions are passed on from parents to offspring when the child is made in the first place, in the very initial stage of fertilisation.

And therefore, the characteristics that a child can inherit can only be inherited from their parents.

Now, within that DNA; and there's a lot of it within a cell, absolutely incredible amounts of it; all of those, all of that information is chopped up into very small sections called genes.

And we have two copies of every gene.

We have inherited one copy of every gene from our biological mother, and one copy of every gene from our biological father.

Therefore 50% of our DNA comes from our mum, 50% from our dad, and we have two copies of every gene.

So, quick check for understanding.

If this couple has a baby girl, she will only inherit features from her mother.

True or false? What do you think? Well, hopefully you've said false to that.

But why? Can you justify your answer with one of these two justifications? So, hopefully you've said that children inherit a mix of features from both of their parents.

We inherit our characteristics from both our biological mother and our biological father.

Okay, well done.

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

We have many, many, many genes, and let's just look at a small subsection of that.

One copy of each of those genes has come from our biological father, and one copy of each of those genes has come from our biological mother.

So, the baby has got two copies of each gene, but one has come from dad and one has come from mum.

And you can see that there that, in gene one, they've got the sort of teal colour from dad and the pink from mum, the red from dad and the red from mum, and the blue from dad and the purple from mum.

And therefore, you can see that not only are mum and dad different from each other, but the baby is different from its parents, as well, because the inheritance of those genes is random, entirely random, and entirely dependent on the genes that are available from the parents in the first place.

And it's this variation, this randomness, that causes variation within the offspring and makes them look different from their parents.

So, let's have a quick check.

So, we can see here this couple.

Flo has blue eyes, and her husband Joe has green eyes.

Flo really wants their baby to have blue eyes.

So, which of these statements are right or wrong? What do you think? Can Flo have a baby with blue eyes if she decides to? Is it that the baby's eyes will depend on genetic information it gets from its parents? Is it that the baby will inherit half of its genes from each parent? And is it right that the baby's eyes could be blue or green? So, what do you think? Just pause the video for a few seconds.

Come back to me when you're ready.

Okay, so let's have a look and see.

Well, Flo can decide to have a baby with blue eyes if she decides to.

That is absolutely wrong.

She cannot impact that decision at all.

The baby's eye colour will depend on the genetic information it gets from its parents.

That's absolutely correct.

The baby will inherit half of its genes from each parent.

That also is correct.

And the baby's eyes could be blue or green.

That also is correct.

How did you get on? Did you get them all right? Well done if you did.

Good job.

So, what I'd like you to do now is to firstly spend some time discussing these questions with your partner, before you then go on to write your own explanation.

The questions are about this scenario, the next generation of mobile phone.

"This phone has inherited all the best features of the earlier models," says Sell Phones Magazine.

So, in what ways could the advert give the wrong idea about how characteristics are inherited? And how would you explain biological inheritance to somebody who was confused by the advert? So, do take your time over this, pause the video, and come back to me when you're ready.

Okay, well hopefully you've had a good amount of time to both discuss this with your partner and also consolidate your ideas and put them onto paper.

So, what might you have written? So, in what ways could the advert give the wrong idea about how characteristics are inherited? So, your answer may have included that mobile phones cannot reproduce to pass on characteristics because they must be designed and built; they are not living organisms. And mobile phones do not have DNA or genes, so they cannot pass this on to the next generation of phones.

And therefore, new mobile phones cannot inherit characteristics from previous generations; they are not alive.

In answer to question two, how would you explain biological inheritance to somebody who was confused by the advert? Well, you might have included ideas along the lines that only biological characteristics can be inherited, and only characteristics affected by genes or DNA can be inherited.

And therefore, only really some of our characteristics are inherited.

And as we'll see in a little bit, quite a lot of our characteristics aren't inherited at all.

Also that offspring receive half of their DNA from one parent and half from another, and they have two biological parents, so they get 50% of their DNA from one and 50% from the other.

Just check your work over, make sure you've got all those key points in there.

Well done.

That was quite a lot of intensive analysis and explanation, so that's quite a tricky job.

Well done indeed.

Okay, let's have a look then at variation.

So, we see that there's variation between members of the same species, and we've also identified that this variation comes from the different mix of genes that each individual has.

And we can see that baby one has a mixture of the genes of its biological father and biological mother.

If we had a look at the gene mix from baby two, we would see that baby two has got a teal-colored from dad and a teal-colored gene from mum, the grey gene from dad and the light green one from mum, and the orange gene from dad and the purple one from mum.

And therefore baby two has quite a significant difference in its DNA makeup compared to baby one.

Now, the visible features that are controlled by genes and genes alone, so these are the features that we can see, include things like eye colour; whether your earlobe is attached or unattached; the ability to tongue roll, so turn your tongue into a straw or pucker it up at the end; and your blood type.

And there are plenty of other things, as well, but these are really obvious visible things that are quite easy to identify.

And we can see that there is great variation in the genes just from these two examples, and therefore why these sorts of variations like eye colour and blood type can be so different between individuals.

However, not all of our variation is caused by genes alone.

Much of our variation is caused by the environment as well.

So, things like piercings and tattoos, these are changes that we choose to make to our physical appearance.

And scars are also similarly environmentally caused.

We are choosing to make these changes to our body, or they are being made to us perhaps through an accident or that sort of thing.

And they aren't under the remit, in any way at all, from genes.

So, there's nothing genetic about ear piercings, tattoos, and scars, and we cannot pass these things onto our offspring as a result.

Therefore, we can say that these types of variation cannot be inherited.

Then there are also parts of our variation which depend in part on our genes, and in part by our environment.

So, body mass, for instance, is an example of this.

It is influenced by our genes but also on our lifestyle.

So, depending on how much we eat, what kinds of things we eat, and how active we are, our body mass will change.

Well, you probably already know that.

So, in part, our body mass is directed by our genes; and to a larger part, it's directed by our environment and our lifestyle choices.

So, these sorts of features are determined not only by inheritance but by lifestyle and our environment.

So, what I'd like you to do now is match the statements on the left with the features that they influence on the right.

So, some of these features are influenced only by genes, some of them are caused only by environment or lifestyle, and some of them are affected by genes and the environment or lifestyle.

But which one is which? So, pause the video and come back to me when you're ready with your decision.

Okay, so let's have a look.

So, we should say that hair colour and style is affected by genes and the environmental lifestyle.

Our eye colour is caused only by genes.

Our height is caused by genes and our environment and lifestyle.

The musculature within our arms is caused by genes and environmental lifestyle; so is our weight.

And nose piercings are caused only by our environment or lifestyle, and certainly not by genes or a mixture of both.

So, did you get them all right? Well done.

So, what I'd like you to do now is to return to that Venn diagram that you created in task A, and use a key to identify each characteristic for the two dogs, Skippy and Bouncer, as being either caused only by genes, caused only by the environment or lifestyle, or being affected by both.

So, I've just taken the letters G, E, and B to give myself a key, but you might have a different idea for doing that.

Just make sure that your key clearly identifies which one is for which characteristic type.

Then, once you've done that, I'd like you to explain to Jacob why his suggestion is incorrect.

So, Jacob says you could use a baby's genetic information to work out exactly what it will look like when it's older.

So, why is he incorrect, and which type of features would this work for only? So, pause the video, and come back to me when you're ready.

Okay, let's have a look at what you've done then.

So, for the first task, I asked you to use a key to code up which of these features are caused by which type of characteristic for Skippy and Bouncer.

So, you might have put that ears pointing up or flopping down is a genetic feature.

White fur, or white fur with black sections will be partly genetic, partly environmental.

And that the fur being short and straight or short and curly, well, you might have decided that's only genetic, but you might also have decided it's both genetic and lifestyle; and that would depend on how you interpret whether they've been to dog grooming or something like that recently.

So, either-or will be fine.

For short legs, you should have noted that this is both genetic and environment or lifestyle, because if they didn't get well fed, then their legs are likely to be shorter than if they were very well fed.

Their black nose is genetic only.

Their teeth are likely to be genetic and environment and lifestyle, because depending on how good a diet they've had and how well their teeth are being looked after will depend on how their teeth have survived and whether they've lost any; that sort of thing.

And then, their body shape is also a mixture of genetics and environment or lifestyle; again, down to things like diet and exercise.

So, just quickly review your work, and then let's move on to the next question, which was asking you to explain why Jacob is incorrect and which of the features his suggestion would work for.

So, you might have said that the environment or lifestyle has a huge impact on an organism's appearance, and only few visible features are solely determined by genetics, such as eye colour, ear lobe attachment, the ability to curl your tongue and blood type; whereas actually, most of our features are influenced by the environment or our lifestyle choices.

So, whilst we could get a rough idea of certain features using the genetic information from a baby, we wouldn't be able to say for sure precisely what it's going to look like because of all the environmental and lifestyle influences that will affect it as well.

That was, again, quite a tricky thing to explain.

So, well done of having a really good go at that.

So, in summary, we have seen that members of the same species resemble one another, and that offspring inherit features from both parents, so they look similar to their parents and similar to any siblings, but not identical, and there is therefore variation between them.

Now, some features are inherited when DNA is passed from parent to offspring during reproduction; things like eye colour, blood type, the ability to roll your tongue, for instance; whereas many features are caused or changed by the organism's lifestyle and environment; things like weight and height, plus whether you have scars and tattoos and piercings.

I hope you found today's lesson interesting.

Thank you very much for joining me, and I hope to see you again soon.

Bye.