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RIDDLE:                Alive without breath, as cold as death, clad in mail never clinking, never thirsty, ever drinking.  (A FISH)

Bilbo Baggins didn’t stump Gollum with that riddle deep under the Misty Mountains, and I couldn’t stump my students with it either!  To focus on fish, our nature study class met beside Little Limestone Creek at Mill Spring Park in beautiful, historic Jonesborough, Tennessee.  It was a warm, overcast day, but the thunderstorms held off and at least the moms were able to stay relatively dry.  The kids were another story — as you will see!  We started off by collecting specimens from the creek in large, clear containers:  Minnows, aquatic insects and even a crayfish.  We brought them to the gazebo, spread out the quilts, got out our hand lenses, and sat down for a good, close look.

 

FIELD WORK:

  • How many fins has the fish?
  • Are the fins constantly moving? Do they move together or alternately?  How is each fin used?  How are they used when the fish swims backward? What are the fins doing when the fish is at rest?
  • Is the tail square, rounded, or notched?
  • What covers the fish? Are the scales large or small?  In what direction do they seem to overlap?  Of what use to the fish is this scaly covering?
  • Can you find a long line running down the fish’s side? That’s called the lateral line.
  • Describe the pupil and iris of the fish’s eyes. Can the fish see in all directions?   Does it do so by moving its eye or its body?  Does the fish wink?  Can you see that the eye is spherical?
  • Can you see the nostrils? Is there a little wart-like sac connected to the nostril?
  • What sort of teeth does the fish have?
  • Does the gill cover move with the opening of the mouth?

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OBJECT LESSON:

The fish usually has 7 fins, which play a different role in the fish’s movements:

Dorsal Fin – like a fan, protects the fish against rolling and assists in sudden turns and stops

Tail (Caudal) Fin — propels the body through the water like a scull

Anal Fin – used to keep the fish stable in the water

Ventral (Pelvic) Fins (2) – The pelvic fins assist the fish in going up or down through the water, turning sharply, and stopping quickly

Pectoral Fins (2) – help fish rise or sink in the water

Sight — The eyes of fish have no eyelid.  Fish are nearsighted because the lens is spherical which enables the fish to see underwater.

Smell — The fish’s sense of smell is located in a little sac to which the nostril leads, but the nostrils have no connection whatever with breathing.

Taste — The tongue of the fish is very bony or gristly and immovable, and they have very little sense of taste.  A fish’s teeth can be located on the jaws, inside the mouth, on the tongue and even in the throat!  Fish without teeth expand their jaws and create a huge vacuum so they can literally inhale their food 😉  Check this out!

Hearing — Fish have poor hearing.  They have only an inner ear and it has no exterior outlet.  Instead, it is found inside the fish’s head behind the eye.  Since fish have approximately the same density as water, sound passes right through their bodies.  That doesn’t mean they don’t respond to auditory stimuli, though.  Recent research indicates that fish may exhibit the Lombard Effect when exposed to loud or unfamiliar sounds.  (The Lombard Effect is the involuntary tendency of speakers to increase their vocal effort when speaking in loud noise to enhance the audibility of their voices.)  You read that right:  Fish communicate out loud.  Here’s a short video of minnows “growling” and “knocking”:

Touch – A fish’s “lateral line” consists of different scales that extend along the sides of the body containing small tubes connecting with nerves; it is used to detect motion and vibration in the water – like touch at a distance.  This lateral line is especially important when fish need to gather and/or travel in “schools” because it allows each fish to sense the motions of its neighbors.

The shape, number and position of a fish’s teeth vary according to the food habits of the fish.  Some have blunt teeth suitable for crushing shells; others  have sharp teeth with serrated edges for harvesting vegetables, while some have incisor-like teeth who feed on crabs and snails.  In some species there are several types of teeth, while others (goldfish and minnows) have no teeth at all.  Fish teeth can be on the jaws but also in the roof of the mouth, on the tongue and in the throat.

The covering of fishes varies:  Some have scales, others have a smooth skin.  All fish are covered with a slimy substance which somewhat reduces friction as they swim through the water.

In order to understand how a fish breathes, we must examine its gills.  They are filled with tiny blood vessels, and as the water passes over them, the impurities of the blood pass out through the thin skin of the gills and the life-giving oxygen passes in.  A fish constantly opens and closes its mouth to draw water into the throat and force it out over the gills – the act of breathing.  Fish can’t make use of the air unless it contains enough oxygen, so it’s important that the water they’re in have enough surface area (definitely NOT like Dr. Seuss’s McElligot’s Pool!)  McElligots Pool 2

 

MAKING OBSERVATIONS:

I’ve been so pleased with the progress of our students in just a few short weeks!  They’re paying closer attention and  noticing so much more.   Maybe these nature observation prompts we’ve been using (from John Muir Laws http://www.johnmuirlaws.com/natural-history/deep-observation) have helped played a role.  For each journal entry they are asked to complete these thoughts:

I notice ______________.  (Example: …this flower has five petals, red anthers and serrated leaves.)  Requires close attention.

I wonder _____________.  (Example: …how it disperses its seeds?)  You can help them follow up with this.

It reminds me of ________.  (Example: …the wild strawberries we saw growing by our boat dock.)  This will eventually lead to classifying specimens by leaf shape, color, and other physical characteristics.  It can also help us make connections to previous learning — a poem, story, work of art.

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My 12yo son’s journal entry this week included a sketch and these observations:
I notice that this tree has shallow roots and the roots are in the creek.
I wonder why the bark is in vertical patterns?  Maybe so rain water will run down to the roots?
It reminds me of elves.  ( He’s a huge Lord of the Rings fan!)

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It’s so important to take a moment to make a short sketch or note a small detail while you’re in the field.  If you goal is a lovely nature journal page you can always flesh things out in living color later.  But that tinge of blue on the tip of a wing or the dew drops collecting on an upturned leaf — those lovely bits may be forgotten if you don’t note them as  you see/hear/smell them.

I’ll leave you with image of a single Cardinal Flower (Lobelia cardinalis) we found growing by the creek and a blue darner damselfly — so very lovely!  (All photos in this post were taken by the lovely and talented Beth Waugh.)

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