An ecosystem is a system that has , , and . A is a group of the same species that lives in the .

Multiple populations of different form a .

Which nucleotide component contains nitrogen

2. which is the last step in the scientific method?

Which statements explains what the fossil records indicates? check all that apply. a) earth is 4.5 billion years old b) many organisms have become extinct c) mammals have always existed on earth d) mass extinctions have occurred several times on earth e) the amount of water on earth has decreased over time?