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I like to think of life science as one big pyramid.
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Let's call the pyramid, "biological organization".
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Let's work our way from very small and specific concepts
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to very large and complex topics.
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So let's start at the tip of the pyramid,
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with something so small, it can't be seen by the human eye,
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A cell by itself is the most basic component of life.
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A single cell, which is capable of living on its own,
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is called a unicellular organism,
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organisms like bacteria or protists.
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These organisms are everywhere you look,
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you just can't see them.
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But, when cells join together,
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with more than one cell like itself
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to perform a similar function,
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it's no longer a unicellular organism.
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It's then called a tissue.
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No, not that kind of tissue.
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There are four types of tissues found in the human body:
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Bone tissue is a type of connective tissue
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and it's not flimsy like a Kleenex at all.
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Blood is also an example
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of the same cells working together to perform the same job,
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but it's a liquid,
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again, not like a Kleenex at all.
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No matter what the consistency is,
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a tissue is a group of the same cells,
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working together to perform a similar function.
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Any time there are different tissues working together,
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we then call it an organ.
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That's the next level of the pyramid.
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Animals aren't the only ones with organs;
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plants have organs too.
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When we find multiple different organs
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working together to perform the same job,
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we then call it an organ system.
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Take the digestive system, for example.
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It's made up of a mouth,
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small intestine,
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and large intestine,
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