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M.Ed., Stanford University
Winner of multiple teaching awards
Patrick has been teaching AP Biology for 14 years and is the winner of multiple teaching awards.
Plants have developed a number of adaptive mechanisms over time to aid in their reproduction and growth. Several things that plants have developed to aid in their adaptation include roots, vascular tissue, cuticles, seeds, flowers, fruits, cones, mutualistic relationships and protective chemicals.
Plants as they went to live on land, had to develop several different kinds of adaptations to deal with some of the special challenges that you find on land. Primarily, how do you deal with the fact that you're no longer in water? How can you get the water? And so plants started developing things such as the roots. Roots are special modifications that plants have, that not only just anchor them into the ground, but they're actually modified so that they're really great at pulling in water from the soil. The outer layers of the roots, the epidermal cells, will have extensions of their cell walls called root hairs, which help them pull in additional water from the ground water.
Then to help transport that water, up to the top of the plant, they'll have vascular tissue. Vascular tissue is specialized cells that function as tubes to help transport water, or in the case of what I call phloem cells, to transport other nutrients like glucose and plant hormones, etc, from where the plant is making them, to where the plant needs them. And this has made plants that have vascular tissue very successful. And it gives us things like sequoia trees which could be hundreds of feet tall and they're able to pump water up to that top of the plant, using their specialized vascular tissue.
A cuticle is a waxy layer that plants will have on their outer surfaces and again that's to help keep the water inside the plant so that they don't lose it straight out through their outer surfaces. Much like our skins produce grease and skin oils to help keep in water. Now the seed is another special modification that many of the plants came up with. The seed is a specialized structure that protects the embryo of the plant, so that it doesn't have to worry about drying out. And so seeds they are drought resistant. They can last for long periods of time without water.
Now flowers is something developed by the kind of plant called the angiosperms or simply flowering plants. What flowers do, is they set one of the challenges that plants have when they're engaging in sexual reproduction. With sexual reproduction, you're obviously trying to just, basically have sex with another member of your species. Now with humans, that's not so hard because we can walk and move and we can recognize who's a member of our species and who isn't. For plants however it's a lot harder. So instead of them looking and going, "What a beautiful rose over there!" Instead, if I'm a rosebush, I can have a special flower that attracts a specific insect and that insect only comes to rose flowers. And then he'll pick up pollen from this flower, and take it to other rose flowers and deliver that pollen over there and fertilize just other rose plants. That way the rose bush doesn't have to worry about wasting energy, creating pollen that are going to wind up fertilizing dandelions or sunflowers or corn. It's much more efficient and it takes advantage of the animals that are on land.
Fruit is another modification that the angiosperms came up with. Fruit is a bribe being used to say, "Hey, animal come on over here, take my seed and take it somewhere else." Because a lot of other plants they have to drop their seed basically, right below the parental plant. Which means that when the baby starts to grow, the baby is going to start competing with the parent for ground water. The parent may cause shade and thus choke off its own offspring. So by having fruit that an animal will then eat and then deposit, that seed twenty four to thirty six hours later in a big steaming pile of fertilizer, that was a big advantage for the flowering plants.
Now another thing that plants have done is they've engaged in a lot of mutualistic relationships with other organisms. Now mutualistic relationship is when two different species work together and both of them benefit. Some examples of this would be the obvious flowers and bees. Flowers get the advantage of much better sexual reproduction than other kind of plants can manage, and the bees get the advantage of being given food basically by the flowers. So the flowers make lots of food to attract the bees and the bees make sure there's plenty of flowers in the next generation by delivering the pollen to all the other flowers.
Other examples might include some of the plants that form special nodules in their roots that bacteria will live in. And those bacteria will get some food from the plant while the bacteria will start absorbing nitrogen from the atmosphere and making it available to the plant for it to grow for its own purposes.
Last adaptation I'll talk about are some of the protective chemicals that plants have developed to protect them against all the things that are trying to eat them. 'Cause if you stop and think about it, plants they make food and basically they are food. And they can't just run away from something that's trying to eat them, so instead they produce a wide variety of various poisons and other things, to protect them from things that are trying to eat them. They'll even use these protective chemicals to try to kill other plants. When I was growing up, one of my chores that I hated, was mowing the lawn. I had to mow the front lawn and I had to mow the back lawn. One of the things that I liked about my back lawn though, was that in our backyard we had a redwood tree. Redwood trees produce acids in their needles and in their bark. That's why if you've ever gotten a redwood splinter...ooh it hurts, it burns. That's the chemical that it's using to try to make you leave it alone. Well, when they drop their needles, it typically winds up poisoning the ground so that, grasses can't grow and compete with the redwood tree for soil, ground water soil, or ground water sorry. So the protective chemicals there is helping it wipe out its competitors for the soil nutrients. So there you go, plant adaptations.
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