Because all organisms are made up of cells and there are different types of cells which carry different functions.
There is quite a lot, but the fact that both mitochondria and chloroplasts have their own circular DNAis what I would call "key" evidence. That is, these organelles are not "manufactured" by the cell (i.e., there are no "genes for mitochondria" in eukaryote genomes): like their ancestral bacteria, they reproduce by binary fission.
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Answer:
Plasmodesmata play roles in both cellular communication and in molecule translocation. Plant cells must work together as part of a multicellular organism (the plant); in other words, the individual cells must work to benefit the common good. Therefore, communication between cells is crucial for plant survival.
<span>Heterotrophs, organisms that must get energy from food indirectly from sunlight or inorganic substances, go through the process of cellular respiration to get the energy needed.</span>
