This lesson is all about sexual selection – how the traits that individuals prefer in mates affects how they evolve. While trying to impress their mate in the game, students will learn how different preferences can shape how organisms evolve over 5 generations.


Playing up Cha Cha Island

When first starting the game, your students will need to calibrate the game to make sure that the visuals and audio occur at the same time. They will just need follow along to the instructions and tap the screen to the music. Once complete, they’ll be welcomed by their new little creatures.

The goal of the game is for students to try and impress their mate by dancing.

Students will be able to do this by playing 4 different instruments. Their job is to figure out which instruments their mate likes to listen to.

If they tap their instrument when the heart is in the centre (the green area) of their rhythm bar, they will find out what their female thinks.

When they tap the correct instrument at the correct time, they will receive points. Keep track of the points and your mates smiling face in the upper right hand corner to make sure you’re tapping the correct instruments!

Each female likes two different instruments. It’ll be your students’ job to figure out which ones. These are chosen at random at the start of each game. That means that different students will likely have different goals for their game.

once they successfully win that round, they will get the chance to upgrade and “evolve” their instruments. Evolved instruments will get you more points and allow you to more easily impress your mate. They can then choose which instrument to evolve – best be careful when selecting!

They will continue this way for 5 rounds, after which the game ends and students get to compare the different creatures they created.

How to read and use the figures


This game also has a leaderboard so that students can have a little bit of competition to see who does best – there are always some really high scorers out there! And as you can see, it does get students really into it.

The mean number of wrong dance moves

The first figure shows the average number of times players played the wrong instruments – # of Wrong Moves (y-axis) – in each of the five rounds (x-axis). Your graph may not look exactly like this, but you will notice that there will be a rapid drop off in mistakes. That’s because you don’t impress a mate (and don’t get any points!) when you play the wrong instrument.

This is similar to the dots in Week 3 – the individuals that play the wrong instruments all the time would not impress their mate and wouldn’t get a chance to mate. This time, rather than selection being a result of predators, selection is a result of your mate’s preferences.

This is where you can talk about why everyone stopped making mistakes and what benefit that would be to play the right versus the wrong instruments.

The Time to reach a winning score

Every mate has a certain threshold they have to reach before they agree to mate with you. In our game, that threshold is determined by a score – if you reach a certain score, then your mate will agree to mate with you.

This graph thus shows how long it took to convince your mate (Time, y-axis) in each of the rounds (x-axis). As you can notice, players reached and impressed their mate more quickly in each round – except for the little bump in Round 4 where it took longer than the previous round.

This is where you can ask your students why they are getting faster at impressing their mate. Their answers should be that they are evolving their instruments and getting more points each time they sing and dance to their mate. Additionally, as students play, they will be getting and unlocking more combos. And those combos are worth a lot of points, which decreases the amount of time it takes to impress your mate.

In biological terms, this means that players are getting better at impressing their mates with their complex dance moves (combos) and instruments that they evolve each round. Oh, and that jump in Round 4? That’s because the mate gets a bit more picky at that stage, which makes it a bit harder to impress them. That bump should happen to your class as well and is a fun thing to discuss.

The Cumulative Number of Combos Discovered

This figure shows the cumulative number of new combos discovered (y-axis) each round (x-axis). Your graph will look very similar to this as your students will naturally find more combos as they play. That’s because they will have new and evolved instruments to show off.

In this sense, individuals are evolving more complex dance moves as they are also evolving more complex instruments. This is your opportunity to talk about how selection (in this case, through the preference of your mate) can affect the evolution of lots of different traits and behaviours. You can chat about why you are discovering more combos and how that helps you potentially convince your partner to mate with you.

The idea of combos in our game is similar to the idea that individuals are evolving more complex dance moves to go along with their more complex instruments. This is a very common thing in nature – in birds for example, we commonly see species evolving more complex songs with more complex notes.

The different Creatures your class created!

This is where you get the chance to view all the different creatures that each of your students made. You can compare the differences and ask your students why they think they look different to one another.

Have a discussion on the different strategies your students used. you can also ask why some players (like Gabe below) invested in one trait instead of multiple traits (like Faz and Salty). There is no right answer and the point is to demonstrate that there are different solutions (which instruments to use) to the same problem (how to impress a mate).

But of course, these pictures will likely lead your students to ask why the animals look different. This is where you can lead the class to a discussion to realise that their mates had different preferences to begin with, and that shaped how their creatures looked. This is exactly what happens in nature! It’s why we have so many different species of animals that look so similar to one another (like birds!).

Have fun chatting about this and you can let students play as many times as they like and see what kind of new creatures they can evolve.

Extension questions

This experiment really allows students to quickly understand what happens to animals that don’t find and impress a mate. Ask your students to play one more time, and this time, get them to only use instruments their partner DOESN’T like. What happens? Ask them to explain why that happened.

How does that relate to what we learned in Week 3 with dots and predators? Is it the same? Or is it different? (Hint, it’s the same!). In both cases, selection (Week 3: the students as predators; Week 4: the mates) was acting on the variation in the population (Week 3: the speed and agility of the dots; Week 4: the instruments and combos discovered) and because offspring inherited the new larger traits (heritability!), the traits ended up evolving.

You can ask your students to look up examples of sexual selection and explore concepts of runaway selection – that’s the constant evolution of larger traits because potential mates prefer larger traits! (think about deer antlers or bird colours and feathers).


In this lesson, students learned about Sexual Selection, a very potent selection pressure which has shaped all organisms on this planet. At times, it is thought that Sexual Selection is much stronger than Natural Selection. If you can’t convince a partner to mate with you, it doesn’t matter that you survived because you won’t have offspring that carry your genes in the next generation.