Picking up from where we left off, we talked about organisms in particular. I'll be brief...
The structural hierarchy of life continues to unfold as we explore, I guess the architecture of more and more complex organisms. We come across things like organs and organ systems!
I suppose, in a sense... an organ is a part of a body/organism that carries out a particular function in the body. Stems and roots are the major organs of plants for instance. This may some completely obvious to you but that's pretty much it. Examples from the human body include: brain, heart, etc.
If we look into complex organisms such as humans ourselves and plants are organised into organ systems. In other words, each organ system is like a team of organs with a role of fulfilling a larger function. For instance, the human digestive system includes organs such as the tongue, stomach, etc.
These organs themselves, consist of multiple tissues.
These require a microscope for us to see... Each tissue is made up of a group of cells that essentially work together in order to perform a specialised function.
The cell is life's fundamental unit of structure and function. Some have only one cell, such as amoebas and most bacteria. So everything else, such as plants and animals are multicellular.
Here we have a division of labour among particular specialised cells. Like the human body consists of trillions of cells of different kinds: nerve cells, muscle cells and so on.
Inside a cell, there are small structures known as organelles, the various functional components in cells. These can only be seen with a strong microscope... Most cells have similar organelles which are responsible for certain types of chemical reactions!
Speaking of chemical reactions, we have molecules such as chlorophyll in plant cells, one of the most important molecules on Earth. They absorb sunlight when photosynthesis occurs in plants and so on. And we also have chemical reactions occurring in the cells of human bodies and other animals... which goes into Organic Chemistry/Biochemistry!
For those interested in Organic Chem, there are different structures of chlorophyll, here's one of 'em...
Looks like chlorophyll c1, there are others like a, b, and stuff. You can check them out on websites like Wikipedia. x'D
That's pretty much, I guess you could view this as the range of Biology. As you can see, it is a pretty broad subject!