Question: would there have been stars in the very first second? how did the first animal appear on earth?

Laurence Perreault Levasseur answered on 18 Jun 2014:

These are two very different questions!
For the first. No, there was no stars in the very first second. Just after the Big Bang, the Universe was filled with a very uniform ‘soup’ of very VERY hot and very VERY dense plasma of particles. As the Universe expanded, the soup cooled down, and 400 000 years after the Big Bang, the plasma soup became cold enough to become a gas. (plasma is just a different state of matter, just like solid, liquid and gas, just much hotter than a gas!)

From here, we still have to wait for gravity to transform this (almost) uniform gas (mostly hydrogen) into clouds, and then further collapse and contract those clouds into balls of gas that were hot and dense enough to ignite the first stars. It’s difficult to know exactly how long this took, but we can estimate roughly 100 to 150 million years after the Big Bang.

For your second question, now. I don’t pretend to be an expert, or even a biologist, but here’s what I understand of it. The very first living things to appear on earth were not animals, they were very simple cells (each organism formed of a unique cell) with a very simple membrane and no nucleus inside to protect the DNA. Those cells are called procaryotes. There are many different types of organisms that are procaryotes, but all are made of this very simple type of cell.

Then, 2 billion years ago, a more complex and more resistant type of cell appeared, with a better (double layer) membrane and a nucleus in the middle to protect the DNA. By this time, still, only single cells organisms existed. 1 billion years ago, the first multicellular organisms appeared.

The first animal only came 600 million years ago, and are believed to have evolved from an eucaryote cell with a little tail that allowed it to move around (called a flagella). They looked like very early form of sponges (yes, sponges are animals!!)