What does the nucleus contain? what role do its contents play in the cell?

Assume that a student is given two different models of bacteria, with one model consisting of big bacteria and the other consisting of small bacteria. how can the student demonstate the theory of endosymbiosis using the models

How many trophic levels are there in the following food chain? phytoplankton - shrimp - perch - pike - osprey

Ineed a chemical reaction takes place in which erlergy is released. arrange the reaction's characteristics in order from start to finis lower energy of reactants higher energy of products higher energy of reactants transition state sd lower energy of products