Has the earth been around long enough for a single celled organism to evolve into a plant or a fish or any other complex animal?

yes. you are the product of such an evolution. so am i and everybody else.

 

every multicellular organism is.

Has the earth been around long enough for a single celled organism to evolve into a plant or a fish or any other complex animal?

 

More than enough time! This is a common argument that creationists use, especially when they are arguing for a young earth. The reasoning is: if the earth is less than 20,000 years old, then evolution must be false because there is not enough time for evolution to work.

 

However, if you accept the overwhelming data that the earth is 4.55 billion years old and that the first fossilized life is 3.8 billion years old, there is way more than enough time.

 

One thing that shook up the evolutionary world was a recent study showing that natural selection can work up to 10,000 times faster than is commonly seen in the fossil record! Which means that the question got turned around from: "Can natural selection work fast enough to produce the diversity of life we see today?" to a new question: "Why has natural selection been so slow when it can be so fast?"