The answer depends on what characteristic of the plants and animals you are measuring: their mass, height, volume, rate of growth, etc. And since you have not bothered to share that crucial bit of information, I cannot provide a more useful answer.
A megabyte.
The most appropriate metric unit to measure the mass of a concrete block is kilograms (kg).
A metric ruler is the most common device used to measure millimeters.
A metre.
The most appropriate measure is a metre.
Most plants and animals can also live only in environments that have Moderate Temperatures
It would be millimetres.
metric ruler
Metric
The metric unit used most often to measure liquids is the liter (L). It is a unit of capacity and is commonly used in everyday life and in the scientific community.
Animals get most of their energy and nutrition from plants. Animals either eat the plants, or eat animals that ate the plants. Also, it gives animals a place to live. Such as Spiders, ants, moles, and other animals. Plants also provide animals oxygen.
why do you think many animals and plants did not become fossils