Potential number of living creatures in one gram of soil. (In less biodiverse soils, the number may be as low as 10,000 organisms.) Most of these creatures are bacteria, fungi, algae, and protozoans, along with larger but still microscopic insects and insect larvae. According to soil scientists, no environment on earth is more biologically diverse, per unit area, than soil. The picture above is one of the creatures, called a tardigrade.