A Little Bit More
Scientists refer to organisms arriving at a similar evolutionary “solution”, even though not related, when faced with similar environmental requirements in behavior and function as having performed “convergent evolution”. It’s really an impressive concept and you’ll see examples of this over and over again in the natural world once you know it exists.
Convergent evolution can take the form of similar behaviors, or similar form and function. When we look at a whale, we immediately see its similarities with fish. It has a long, tapered body, lives all its life in water, doesn’t have arms and legs but fin-like appendages, and a broad, flat tail for propelling itself through water. But a closer look at whales also shows us that they’re mammals – they have hair (not very much though) and nurse their young with milk. Of course, we know from the fossil record that fish evolved much earlier than mammals did and fossils also show us that whales evolved much later than the first land-based mammals. But over time, these “mammals that went back to water” developed adaptations very similar to the fishes in the sea. In fact, the whales, porpoises and dolphins look so fish-like that it’s hard to imagine them ever being terrestrial. I like to look at the hippopotamus of today and wonder if, given enough time, they too might become fully aquatic; who knows?
So, in a sense, convergent evolution can be viewed as different animals traveling down an evolutionary “road” that converges with another very different animal. No, these animals are not now closely related, it’s just that they both came up with similar “solutions”, if you will, to a similar environment.
Activities
Science – Copy Cat
Objectives: Find some examples of Convergent Evolution
Materials: Library reference material or online materials
One college biology text defined Convergent Evolution as “evolution of similar features by unrelated organisms in response to similar selective pressures”. Thus, if two different kinds of organisms are adapting to a similar environment, they MAY very well come up with similar solutions of anatomy or behaviors to that environment. We gave you 4 different organisms on the unit poster that came up with very similar front “leg” structures that are clearly very similar in function so I hope this makes sense.
This is an activity for older students although you may want to simply use my examples below and have younger students find pictures of these. Let’s see if your students can find some other similarities that different animals or plants have achieved over time. I’ll give you some examples to help but you may want to see if the students can come up with their own first. Even if they only can find one or two examples, this exercise will be worth it. Although plants also exhibit convergent evolution, I think the students will find animals much easier to work with on this exercise so we’ll stick with animals.
Organisms that exhibit Convergent Evolution:
- Penguin, shark, porpoise
- snake, legless lizard
- bat, bird, butterfly
- cactus, spurge
- sphinx moth, hummingbird
- ducks, grebes, pelicans
- Ostrich foot and antelope
- old world vultures (hawks) and new world vultures (storks)
There are all kinds of examples of convergent evolution that we can see in the natural world. All we need to do is look around and we’ll see them. Try having your students see if they can come up with some examples.
- Have your students look through some photography books on animals to see if they can find some examples of convergent evolution.
- When they find an animal that has some kind of adaptation that is very similar to another different kind of animal this should be noted (ie. They see a whale, this may bring to mind the fact that this animal is very similar to fish)
- Once they’ve found two animals (maybe even three with the same adaptation) they should write down what it is that has led them down that same path (ie whales and fish must both be able navigate in water)
- If your students are younger, you may want to give them some animal pairs and see if they can come up with what behaviors or anatomical parts are similar to each other.
Here are some examples of animals that you might want to share.
Feet – antelope, horses and ostrich have reduced numbers of toes
Feet/Toes – ducks, Beavers, and pelicans all have webbed feet/toes
Body – herons and cranes both have very similar body shapes (long legs and bills)
Tails – woodpeckers and creepers have very similar tails that support their weight on a tree trunk
Wings – swallows, swifts, and falcons have very similar wing shapes
Wings – birds, bats, and butterflies all have wings
Bills – herons and cranes both have long, thin bills
Camouflage – many kinds of birds, mammals, insects and amphibians have ways of blending in
Warning colors – some amphibians, snakes and insects have warning colors
Legs – kangaroos and jumping mice have large hind legs
Key Concepts
Adaptations and Diversity, Structures and Functions
Questions
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