What does a scientific theory include

What are tissues? a groups of tissues that work together b basic units of structure and function c groups of cells that perform the same function d multiple organs that perform a major function

Which part of cellular respiration must occur before any of the other steps can occur

How can a geological time scale best be reconstructed? a) comparing vestigial structures in living species b) comparing homologous structures in living species c) examining homologous structures in fossil remains d) examining the written records of scientists from past cultures