Studying for bio test. Oh, what a joy.
I am sick and delirious right now, so if this seems silly, forgive me.
This is the most memorizing-dependent unit, it seems. Have fun. -____-

Hierarchy of Structure - Animals

So an animal is composed of many levels of structure. Here they are, ascending in size:

  1. 1.

    Atoms - yeah: carbon hydrogen oxygen

  2. 2.

    Molcules - groups of atoms: carbon dioxide, water, glucose

  3. 3.

    Organelles - tiny structures inside the cell: mitochondrion, nucleus, chloroplast

  4. 4.

    Cells - smallest unit of life: blood cells, skin cells, nerve cells

  5. 5.

    Tissues - groups of cells that perform specific limited functions: epithelial, cardiac muscle tissue

  6. 6.

    Organs - groups of tissues that perform specific function; may contain several types of tissues: the heart contains nerve, cardiac muscle, epithelial, connective tissues

  7. 7.

    Organ System - group of organs that work together to perform a major function: circulatory system contains heart, blood, spleen