In this ecosystem there are many different species living together with all of the other animals.
At this time all of the species are producing offspring. With species such as ladybugs they are going to overproduce because they have a lot of predators, and this will give a better chance of some of this generation surviving.
When the ladybugs do produce there is some variation within their species. Most of them had the dominant gene that made them red, but a couple of them had the homozygous recessive gene the made them yellow.
Ladybugs have many predators within their ecosystem such as birds. And birds are used to going after the red ladybugs, so they are going to go and eat all of them.
But the other ladybugs, the yellow ones, they blend into their surrounding flowers, so the birds don't look and find the recessive ladybugs. And then these ones will end up surviving.
Then these are the ladybugs that will end up surviving throughout all of the upcoming generations and the yellow gene will be passed down to the other ladybugs. And then they will have adapted to this situation in order to stay alive.