Botany 101, Part 2: The Knees of the Bees (and of the Trees)

Evolutionary Morphology: Form Follows Function

There are some decidedly weird shapes in nature. Take tree knees, for instance:

Cypress knees, a woody growth of cypress trees in swampy areas.
Cypress knees, a woody growth of cypress trees in swampy areas.

How and why did they form in such ways? These odd marshy lumps, as well as the rest of the forms of nature, have evolution to thank for their existence.

According to our current understanding of evolution, the living thing that is best able to survive in an environment survives and reproduces, leaving behind more living things similar to it that are well-adapted to survive in that same environment. Living things that are not as good at surviving don’t live to make more of themselves, and therefore over time they disappear from an environment.

Imagine that each circle below is a living creature. Some are pink, some are green, some are dark blue, and some are light blue. The dark and light blue circles are targeted by a predator in the area that’s eyesight allows it to see those colors well, but not to see pink or green well at all. And so the predator skips pink or green meals and snacks so much on blue meals that the blue circles disappear from the population. Since just pink and green circles survive, only green and pink circles are born, and over time the look of the population reflects that.

This, of course, is a simplified example of evolution, but you can imagine how this might work with real organisms. If a snake living in Pennsylvania isn’t well-adapted to cold winters, for example, it will not survive there and eventually there will be no more of that kind of snake in Pennsylvania.

Morphology, or the physical shape of a living thing, is important to an organisms’ ability to survive in an environment. In simple terms, form follows function: if something doesn’t have the hardware to do a thing it needs to do to live, it can’t do that thing – and won’t live.

Morphology is very important to botany. It’s what is largely used to categorize and identify plants. Scent can also be used, especially with aromatics such as mint. Morphology is, for example, important for pollinator-plant relationships.


Take, for example, the humble hummingbird. Their long beaks are well-formed to reach into the deepest flowers, where small pollinators like bumblebees can’t reach. This creates an advantageous relationship between flowers like lillies and hummingbirds, where both parties win a victory.

Hummingbirds have long probing beaks.
A hummingbird feeds from a lily flower.

And it might seem like bumblebees lose when hummingbirds have dibs on certain flowers, but bees have their own favorite nectar meals. And the flowers in both relationships win, too; pollinators are called such because when they come to snack on plant matter, they help to spread that plant’s pollen and create baby plants.

y the way, if you were wondering, research shows that tree knees seem to be for increased gas exchange, specifically oxygen, in swamp environments.

Next installment, on Plant Anatomy, coming soon!

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