A Little Bit More
Although we use the term “lobster” to refer to a variety of edible crustaceans, it is the clawed lobsters that are best known from the cold waters of the North Atlantic. Two other groups of animals called lobster are the spiny (like the Florida lobster) and slipper lobsters; both without claws. The American Lobster is more closely related to the freshwater crayfish than it is to either the spiny or slipper lobsters.
The lobster’s specialization of its claws – one crusher and the other pincer - certainly must provide a feeding advantage to these animals. It’s interesting to note that a lobster may be left-handed or right-handed, depending on what you might consider the dominant claw. A lobster’s handedness is established soon after it settles to living on the bottom and remains the same throughout its life.
The lobster’s crushing claw has large molar-like lumps on the claw that help crush various food items. The muscles in this claw are the slow-twitch kind that provide power and endurance for long, strong contractions. The more delicate pincer or seizing claw has finer “teeth” on its edge and also tufts of sensory hairs to help the animal manipulate food items. These muscles are the fast-twitch kind and provide faster contractions and movement but of shorter duration.
The similar-looking freshwater crayfish does not have this specialization of its claws; its claws are both identical, or almost so, in size and shape.
Activities
Science – Write Your Name
Objectives: Graphic example how our own hands are “different”
Materials: Paper and pencil
We’ve seen how a lobster’s claws are different both structurally and functionally so now what about our own hands? Although human hands may seem identical –are they really?
Most people are either left or right-handed and strongly favor the use of one hand over another for most daily tasks. There are a few people, however, who are ambidextrous and are equally comfortable using either hand for activities. This activity is designed to help students focus on just how different their hands, or at least their hands’ abilities, are.
Ask students to write their full name as neatly as possible on a piece of paper
Now ask students to switch hands and write their name again as neatly as possible just below the first signature.
No matter how hard they might try, almost all students will find that their second writing attempt with their less dominant hand is not nearly as easy to do nor easy to read. There is a big difference in our ability to use one hand over another. Most humans are right-handed but a sizable percentage are left-handed – one is not BETTER than another, just different!
Would be interesting to see how many students are right or left-handed and maybe even see whether any is ambidextrous. About 10% of the world’s population is left-handed.
Might be interesting to discuss with students whether those with a right-handed writing dominance use the other hand in a dominant manner in some other way, and visa versa. Although I’m right-handed in most activities myself, my left hand is dominant when I shave. I’m sure some students will have similar examples to share.
Info on left-handedness
Key Concepts
Adaptations and Diversity, Behavior and Regulation, Growth and Development, Structures and Functions
Questions
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