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Third Grade Integrated NGSS |
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OBJECTIVE  · Identifying arthropods.· Grouping invertebrates and vertebrates. · arthropod· insect · metamorphosis MATERIALS: · Set of different groups of insects
·
Entomologist Sets
·
Life
Cycle of Mosquito VIDEO
Metamorphosis video (explains difference between
complete and incomplete) https://www.youtube.com/watch?v=wFfO7f8Vr9c BACKGROUND:
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") when the arthropod
gets larger. There is no internal skeleton. Many arthropods go through
metamorphosis or physical changes. So a butterfly is the adult
insect but the caterpillar is one of the 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 it metamorphoses into a flying
insect.
Identification of arthropods is not easy, because there are so many
"creepy crawlies" out there.
Insects develop from egg to adult in a process called metamorphosis.
Different groups undergo metamorphosis in different stages. Some
arthropods have a different phase that looks totally different than the
adult. This is called
complete metamorphosis. which
may be generally classified as either gradual or complete. Gradual or
metamorphosis has three stages – egg, nymph, and adult. Nymphs generally
look much like their adult stage except for being smaller and lacking
wings, if the species has winged adults. Common examples include stink
bugs, grasshoppers, and cockroaches.
About 75% of all insect species go through the four stages of complete
metamorphosis - egg, larva, pupa, and adult. The larva is a specialized
feeding stage that looks very different from the adult.
I. Simple Metamorphosis
Note: Some naming conventions provide sub-categories for simple
metamorphosis as follows: 
II. Complete Metamorphosis
(Egg > Larva (more precisely: larval instars) > pupa > adult
)
These insects also have a resting stage known as a pupa. The pupal stage
is a transition stage, when the larva transforms into the adult. Wings, if
present, develop internally within a pupa. The pupa molts to the adult
form.
Insects with complete metamorphosis include lacewings (Order Neuroptera),
beetles (Order Coleoptera), butterflies and moths (Order Lepidoptera),
true flies (Order Diptera) and wasps and bees (Order Hymenoptera). In some
insect orders, larvae are referred to by other names, such as maggots
(flies), caterpillars (butterflies and moths) or grubs (beetles). Larvae
of insects with complete metamorphosis usually have chewing mouthparts;
many are pests of various crops.
III. No Metamorphosis (Egg-Adult)
no change in appearance.
Example would be a silverfish.
PROCEDURE:
1.
Today we will be talking about the life cycle
of insects. The majority go
through metamorphosis though not all do.
The word metamorphosis means to change shape.
2.
There are two kinds of metamorphosis:
complete metamorphosis or incomplete/simple metamorphosis.
(No metamorphosis means hatched insect just gets bigger over time.)
Play video on complete/incomplete (simple) metamorphosis.
3.
Put the specimens from an entomologist on the table (as a display).
They were collected in the 1980’s so please tell the students the
importance of not touching them. This is a typical way in which an
entomologist collects his specimens and identifies them. Have
them try and determine which one is which, and try to have them guess what
type of metamorphoses they go through. Remember it is difficult to
determine the different stages, so the more they go over it the more they
will be familiar with the changes. Important part is for them to
realize that they look very different. Look at following site for
charts on the type of metamorphoses
(https://www.uky.edu/Ag/Entomology/ythfacts/4h/unit2/metavari.htm). 5.
Sorting
Arthropods.
Tell students that the models that
are left are all Arthropod or animals that have an exoskeleton.
An exoskeleton is when the “skeleton” is on the outside.
Vertebrates have their skeletons inside.
Having an exoskeleton poses a problem for Arthropods.
Ask students what that problem is….. after they guess, tell them
the problem is when they grow they will not fit into their exoskeleton so
they have to lose it (molt) in order to grow bigger.
Order Odonta (Dragonfly)
- they go through incomplete metamorphoses, with the eggs laid on
the surface of the water and then they change to a nymph that looks
nothing like a dragonfly,.
They emerge from the water and then become a land insect.
Order Hymenoptera – Ants, bees, wasps
- complete
Order Lepidotera – Moths and Butterflies go through complete – so egg to
larva to pupa to adult
Order Diptera -
Mosquitoes and Flies -
complete metamorphosis (many have aquatic stage, like mosquito)
Order Orthoptera – Grasshoppers - gradual
Read the following and see if students at each table can determine which
of the models is the correct one. Read the information below and have each
table select the correct stage.
(Mass
of Eggs)
A female mosquito needs a water source in which to lay her eggs.
Stagnant water, such as ponds and marshes, make ideal nesting
grounds. She will lay her
eggs one at a time, laying several hundred in total.
Some species lay their eggs in connected rafts, which others’ eggs
stay separated in the water.
(White with tuffs of hairs)
Larva.
In just a couple of days mosquito eggs will hatch into larvae.
This is an active, growing stage in which the larvae must eat often
and shed their skin as they grow.
The larvae stay in the water in which the eggs were laid, eating
whatever organism matter is present.
(Tan with big head).
Pupa.
After the larvae shed their skin several times, they enter the pupa
stage. As with most insects, this is an inactive stage in which the
mosquito transitions into an adult only about two days to complete the
stage, after which the mosquito is an adult Mosquito. After its pupa skin splits open, an adult emerges still in the water in which the eggs were laid. It takes a few minutes for its winds to dry before the mosquito can take flight. Only female mosquitoes feed on blood, which is needed for them to lay eggs.
Play the video showing Mosquito metamorphosis:
https://www.youtube.com/watch?v=wFfO7f8Vr9c
(3 min)
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