Lesson video

Hi everyone, my name is Miss Hummel.

And in this lesson, we'll be answering the question, are the life cycles of mammals all the same? In this lesson, we will learn about sexual reproduction in mammals, we will also examine the life cycle of mammals, particularly the gestation period, and then we will learn about different groups of mammals.

Finally, we will present and interpret data.

Our lesson will follow this structure.

First, we will learn and recap our understanding of sexual reproduction.

Then, we will discuss life cycles from mammals.

We will learn about the gestation periods.

And then we will examine the differences between groups of mammals.

Finally, we will interpret and present data relating to mammal size and gestation periods.

In this lesson, you will need an exercise book or paper, a pencil or pen, a coloured pencil or pen, and a ruler.

If you haven't got those things, go get them now.

Great.

Our star words today are, lifecycle and mammals, which are included in the question we're investigating and sexual reproduction.

We will also need to know the meaning of gestation as well as have an understanding of the word species.

Finally, we will learn the words of placental, monotremes and marsupials, which all relate to groups of mammals.

In previous lessons, we should have learned that sexual reproduction is a form of reproduction in which genetic material from two individuals of opposite sexes mixes to create offspring.

We now know that both male and female sex cells fuse together, which results in a process called fertilisation.

This is also the case for mammals.

So we can say that mammals need both a male and a female to create offspring.

This offspring will grow once fertilisation has occurred.

Next, we're going to look at the life cycles of mammals.

Each mammal goes through various stages of life.

All mammals are born, grow, reproduce and die.

These are some of the characteristics of mammals.

We know some of these already, but some may be new information.

A mammal gets milk from its mother.

Has a backbone.

Has fur or hair on its body.

And is warm-blooded.

Like we mentioned earlier, each mammal goes through various stages of life.

All mammals are born, grow, reproduce and die.

We can imagine this as a circular life cycle, in which it continues to repeat once animals have reproduced.

These are some examples of some of the most common mammals on earth.

How many do you recognise? Can you name every one of them? Have you seen any of them in real life? I think I've seen almost all of these.

I think the only one I may not have seen is a donkey.

So, I'll have to look out for one of those.

In this next part of our lesson, we will learn about gestation period.

Before a mammal is even born, it grows and develops inside an egg or its mother, this is called the gestation period.

The gestation period, or the time when a mammal grows inside of its mother, is different across species.

This diagram here, shows us a little more about the gestation period for humans.

Humans know how quickly that baby is growing inside.

They know things like, when they develop fingernails, hair and facial features.

Did you know that a baby already has all of its fingerprints when they're 9 to 12 weeks old in the womb? Now, you may roughly know the gestation period of a human.

However, there are gestation period differences.

Mammal size and mammal group, affect the gestation period of mammals For example, an Asian elephant has a gestation period of 645 days, which is nearly two years.

On the other hand, mice have a gestation period of only 20 days.

So there is a huge difference, literally, between the gestation period of an elephant and that of a mouse.

I would like you now to pause the video, to complete this thinking task.

Do you know the gestation period of a human baby? How does that compare to an elephant or mouse? Resume once you've finished thinking.

Now you may have known that humans have a gestation period of about nine months, which is 266 days.

That is less than half of that of an Asian elephant.

It's also about 13 times longer than that of a mouse.

Now, in order to better understand life cycles of mammals, we need to learn about different groups of mammals.

Scientists have broken mammals up into three groups, placental mammals, monotremes and marsupials.

Have you heard of any of those before? Let's start with placental mammals.

Placental mammals are born prepared to continue their growth outside of their mother's wombs.

Examples include elephants, humans, cats and dogs.

In fact, most of the common mammals we looked at earlier, are considered placental mammals.

Our second group of mammals is monotremes.

There are another group of mammals which are among the oldest, rarest and most unusual animals on the planet.

They hatch from eggs.

The babies have to hatch out of an egg before they're prepared to continue growing outside.

Like other mammals, monotremes are warm-blooded.

They have hair on their bodies and they produce milk to feed their young.

The only difference is that they are born from eggs.

In Echidnas, the female lays eggs into a pouch of skin on her stomach, where she carries them until they hatch.

Did you know that they can only be found in nature in Australia and New Guinea? However, people have found fossils of them in South America.

Now the final group of mammals we need to know are marsupials.

You may have heard of these before, because they continue to grow inside their mother's pouches after they are born.

They include, kangaroos, wallabies, possums, wombats, Tasmanian devils and koalas.

Did you know that most marsupials are night creatures? This means that their sense of smell and hearing is incredibly strong.

Now that we've learned the different groups of mammals, I would now like to see if you can match the names of the groups of mammals with their definitions.

On the left-hand side, we have placental mammals, monotremes and marsupials, and then we've got some definitions on the right-hand side.

The first definition is, hatch from eggs.

The babies have to hatch out of an egg before they're prepared to continue growing outside of their mothers.

There's only two mammals that actually lay eggs and they include the echidna and the duck-billed platypus.

The second definition is, they continue to grow inside their mother's pouches after they are born.

Examples include kangaroos, wallabies, possums, wombats, Tasmanian devils and koalas.

And lastly, the third definition is, they're born prepared to continue their growth outside of their mother's wombs.

Examples include humans, elephants, dogs and cats.

I would like you to pause the video and complete the task above.

When you're finished, make sure to mark your work with a different coloured pen.

Now we match placental mammals with the third definition, monotremes with the first definition, and marsupials with the second definition.

For the final part of our lesson, we're going to think like scientists and interpret and present data.

Your task will be to use the table to help you draw a bar graph comparing the gestation periods of different species of mammals.

An Asian elephant has been drawn in the example for you.

Our table tells us all the information that we need to know.

It tells us the gestation period in days for different species.

Rabbit is 33 days.

Cow is 284 days.

Asian elephant is 645 days.

Dog is 63 days.

Chimpanzee is 227 days.

Black bear is 210 days.

A lion is 108 days.

And humans are 266 days.

Now let's take a look at the bar graph in full-size.

To best make your bar graph, I would ensure I use 14 lines or squares, and that I go from zero to 650, counting in 50s.

The reason I'm going up until 650, is because 645 is my largest number.

I will also need to make sure that I have enough room for my eight species of animals on my x-axis, which is the one that goes horizontally.

Finally, I would make sure that I have a title.

I would consider writing titles for my x and my y-axis as well.

Labelling the x-axis with species and the y-axis with days of gestation period.

It may be tricky to estimate where the bar should end.

For example, cows are 284 days, which will need to go in between 250 and 300, leaning closer towards 300.

Pause the video now to complete the task above.

You can resume once you are finished.

Have you finished your graph? If you follow the same structure as the example, yours should look something like this.

Check your work with a different coloured pen or pencil.

For our last activity, I would like you to pause the video to complete this task.

You should answer this question.

Is there a relationship between a mammal size and its gestation period? Resume the video once you've finished.

Now you may have noted that although there was some relationship between mammal's size and their gestation period, there were some anomalies.

For example, black bears are larger than humans, and yet they had shorter gestation periods.

So although we may notice a trend with gestation period and the size of the animal, there will be some exceptions as well.

We have now finished our lesson and it's time for you to complete your exit quiz.

You need to exit the video and complete the quiz to test your knowledge and your understanding of this lesson.

I hope you enjoyed the lesson.

Bye.