OBJECTIVES:
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How do the arthropod and other little critter populations change
through time?
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Observing and classifying different types of arthropods over time
- Learn to use a graph to show collected data with multiple variables
VOCABULARY:
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arthropod
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insect
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head, thorax, abdomen, antenna, compound eye, wings
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molt
MATERIALS:
BACKGROUND:
In this long-term project, students collect data related to arthropods and
other bug. A
scientist that studies arthropods and other creepy crawlies is called an
entomologist They learn the characteristics of arthropods and various
subtypes. Students work as teams at different plant stations. They shake
vegetation to collect arthropods and other little critters on a white
cloth or sheet. They then classify them, using their identification cards,
count them, make observations, and record and ultimately graph their
results. Over time, they should see arthropod habitat preferences and
variations in arthropod populations due to seasonal change.
Arthropods are bilaterally symmetrical
and have jointed body segments with a pair of appendages attached to each
body segment. The body is covered with a cuticle (thickened substance)
which comes off ("molts") as the arthropod grows. There is no internal
skeleton. The circulatory system of arthropods is very simple, and they
reproduce by laying eggs. Many insects go through metamorphosis during
their life cycle. So, a butterfly is the adult insect, but the caterpillar
is the same insect in one of its early stages and looks more like a "worm"
than an insect. Many arthropods, like mosquitoes, spend most of their life
in an aquatic form before they metamorphose into flying insects.
Identification of arthropod types is
not easy, because there are so many "creepy crawlies" out there.
Arthropods are divided into two major groupings. One group (called
chelicerates) includes spiders, scorpions, ticks and horseshoe crabs. They
have no antennae and the first pair of appendages are pincher-like. The
second major grouping of arthropods (called mandibulates) include most of
the common arthropods, such as bees, flies, butterflies, ants and beetles.
We will be concentrating on the more common arthropods, which are
characterized by a three-part body – head (a), thorax (b) and abdomen (c).
Wing covers or elytra (d), wings (e) and antennae (f) are usually present.
PROCEDURE:
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INTRODUCTORY LESSON – Review key points from the Introductory
video/PowerPoint lesson: What are arthropods? What are their key
characteristics?
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INSECT AND OTHER ID CARDS – Students cut out the cards and assemble. They
punch a hole on the side of each card and tie cards together with yarn
to make a flip chart. Students will use these identification cards to
help them identify arthropod species.
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Students are grouped into 2 or 3-person teams and each team receives
the Observation Booklet they will use during the year.
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Class goes over experiment methodology, and each team fills in
Observation
booklet.
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Each team is given a specific location outside and team members
describe the area and types of plants in it (if known) in their
Observation Booklet.
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Each team goes to their designated area of plants and puts a tray
covered with cloth or white paper under the plants. One team member
shakes the plant 10 times carefully, but firmly. Teams categorize the
insects that have fallen onto the tray using their ID cards
and put counts in their booklet in the "Trial 1" column.
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The other two team members take turns shaking the plant 10 times each
in the same area and put counts into their booklets under the “Trial 2”
and “Trial 3” columns.
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Add up the totals of each type per day and enter in “Total” column.
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Fill in observations and in the booklet draw one of the arthropods.
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OBSERVATIONS OVER TIME – Teams should visit their stations and collect
data at least twice monthly in October and November, once a month in
December and January and twice a month in February and March. Note:
Students may find few insects in the winter months and rainy periods.
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RESULTS AND GRAPH – Students should graph their results at the end of
March and discuss what arthropod types were the most common, what
seasonal patterns they see overall and what patterns they see between
plant stations. For example, at what time of the year did they find
the most and least arthropods? Do certain arthropods prefer certain
types of plants over others? How does the information students learned
about arthropods fit with what they learned in 1st grade (light
changes over the seasons) and 2nd grade (plant growth rate changes
with the seasons)?
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