How Ecosystems and Biodivercity works

Firstly how does an ecosystem work, an ecosystem works when organisms work together and interact with each other.
When more organisms interact with each other, the more complex it is, and if it is more complex it is more secure.

Why is it better for it to be more complex than a simpler ecosystem? 
One reason is biodiversity, biodiversity is when there are a lot of organisms in an ecosystem thus being more biodiverse.

What is biodiversity

and why is it important in a food chain?
well, there are organisms that work in a food chain, for example, let's take a deer, a plant, and a lion,
the order of the food chain would be Plant > Deer > Lion.

The plant is what is called a "Producer" as the plant produces the vegetables for the deer to eat, and then the lion can eat the deer, and then when the lion poops, the plant takes back the nutrients in the poop and make more vegetables for the other deer to eat, and the cycle repeats.

What is the lack of biodiversity?

Okay, let's try another example of biodiversity, let's take the internet, it is like an ecosystem right?

Let's take your phone and Google as examples, if your phone randomly disconnects from the internet the whole internet is still intact, as it is not heavily reliant on it but if Google randomly stopped working, the ecosystem of the internet would collapse.

This is exactly like if you remove the plant from the Plant > Deer > Lion example, as that would cause the deer to die due to lack of food, and the Lion because no more deers.

But that's when a complex ecosystem comes in. It is for the deer to feed even if one species of plant is dead, there are more to eat and to keep the deer population alive.

The same with Lions, as they don't only eat deer, they also eat other animals. And that is why a more complex biodiversity ecosystem is pessary for a large ecosystem to thrive.

And why when animals go extinct it is bad for biodiversity as removing the Lions would cause a large amount deer population to skyrocket and if there is more than the carrying capacity of an ecosystem it can collapse.