Ch 28 Outline: Arthropods
What animals are in the
phylum Arthropods?
a.
b.
c.
d.
e.
Bumble bees
Spiders
Octopus
Lobsters
Millepedes
Answer: A, B, D, E
Answer all that apply by
holding up more than one
card.
There are 4 Subphyla of
Arthropods

List the three subphyla that are still
living. If you can’t remember the names
of the subphyla, write down the
representative species that are in each
group.
Answer: chelicerates, crustaceans, uniraminans
Which subphyla representatives
are are matched to the proper
names?




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A. uniramians – prawns
B. chelicerates – spiders
C. crustaceans – cockroaches
D. triobites – millepedes
4 Subphyla:


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Trilobites (now extinct)
Chelicerates – spiders, ticks, mites,
scorpions, horseshoe crabs
Crustaceans – crabs, shrimp, lobster
Uniramians – centipedes, bees, moths,
grasshoppers, flies, bettles
Evolution: Which insects have common
ancestors with modern annelids
(segmented worms)
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
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A. insects
B. Centipedes
C. millipedes
D. crustaceans
E. spiders (chelicerates)
(hold up multiple letters if more than
one answer apply)
Answer: A, B, C
Evolution


Insects, centipedes
and millipedes seem
to have common
ancestors with
modern annelids
Crustaceans and
spiders evolved from
different ancestors
What is special about the
Velvet worm?



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A. it is a living fossil
B. it is extinct, but has the characteristics of
arthropods
C. It seems to be a “transition” organism
between the annelids and the arthropods
D. It has larvae that are the same as insect
larvae
E. It makes a substance that resembles
velvet
Answer: C
The Velvet worm


Placed in its own
phylum (along with
others like it)
Has characteristics
of both annelids and
arthropods
The First Arthropods?
What Evolutionary trends are shown
within the Arthropods?


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A. early arthropods have a sac body plan; later
arthropods have tube-within-a-tube
B. early arthropods have bilateral symmetry; later
arthropods have radial symmetry
C. early arthropods have many smaller body
segments; later arthropods have fewer but larger
body segments
D. early arthropods do not fly; later arthropods do
E. early arthropods have many unspecialized
appendages, later arthropods have fewer, more
specialized appendages
Answer: C and E
Arthropod Evolutionary Trends


Far fewer body
segments (segments
in embryo fuse into
larger ones)
Appendages become
more and more
specialized
What are the names of the
three main body segments of
an insect?
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

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A. head, legs, wings
B. appendages, thorax, exoskeleton
C. head, thorax, abdomen
D. anterior, posterior, ventral
E. dorsal, ventral, posterior
Answer: c
Structure – head, thorax and
abdomen
List at least two
characteristics that unify the
phylum Arthropoda.

(Answer on next slide)
Arthropods – Characteristics
that Unify
Jointed appendages– antennae,claws, legs,
wings,flippers, etc.
 Exoskeleton
 Segmented body
 Open circulatory
systems

What is the main molecule in
exoskeletons, and what type
of molecule is it?


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A. cellulose, a complex carbohydrate
B. glucose, a simple carbohydrate
C. chitin, a complex carbohydrate
D. starch a complex carbohydrate
E. glycogen, a complex carbohydrate
Answer: C
What is a major DISADVANTAGE to
having an exoskeleton rather than an
endoskeleton?




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A. it is not as strong as an endoskeleton
B. it cannot heal like an endoskeleton can (if
it breaks)
C. it is more vulnerable to breaking since it
is on the outside of the body
D. it does not grow larger like an
endoskeleton can
E. it is not as flexible as an endoskeleton is.
Answer: D
Exoskeletons
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

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Made of chitin
Some
leathery/flexible
Some waterproof
Must be molted for
the animal to grow
There are 4
different structures
that insects use to
breathe. List at
least 2 of them

(Answer on next
slide)

Respiration

Arthropods have 4
basic structures for
respiration:
Gills, Book Gills,
book lungs and
Tracheal tubes
Respiration - Arthropods

Aquatic
arthropods
(crabs and
shrimp):
GILLS
Book Gills


Unique to
horseshoe
crabs
Tissues are
layered
Book Lungs – Layered Tissues

Unique to Chelicerates

Book lungs
How does the air come into the insect if it
is “Breathing” using tracheal tubes?
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A. the air moves through the tubes when the
muscles move the abdominal cavity
B. there is an area inside the expands and
contracts like our diaphragm – this draws
the air in
C. they have an incurrent siphon that pulls
the air through
D. they use their wings to “fan” the air in
Answer: A
What are “spiracles”?

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A. the sensory receptors on the ends of
antennae
B. The structures that are used for
hearing for insects
C. the structures that are used to spin
webs in spiders
D. the holes that allow air into the
tracheal tubes
E. the barbs on the sides of some insects
legs for extra traction.
Answer: D

Tracheal Tubes



Branching tubes
throughout the
tissues
Shrink and contract
when insect’s
muscles move
Causes air to pump
in and out of tissues
Attached to spiracles
(holes on outside of
body)
Tracheal Tubes
Feeding
What can insects eat?


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A. plants
B. animals
C. rotting organic matter
D. fungi (mushrooms)
E. bacteria
Answer: ALL of the above!

Modified appendages enable different arthropods
to eat almost anything
The Difference (s) between an open and closed
circulatory system is (are):
a. Closed systems have a heart (pump); open systems
do not.
b. Closed systems have blood vessels; open systems
do not.
c. Closed systems do not have sinuses (pools of blood
for nutrient exchange); open systems do.
d. Closed systems are more efficient at nutrient and
gas exchange; open systems are less efficient.
e. Humans have closed circulatory systems;
arthropods have open systems
Answer: C, D , E
Internal Transport
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OPEN circulatory system with a well-developed
heart (limits their size!!)
Heart pumps blood through blood vessels to
sinuses where gas and nutrient exchange
occurs with the tissue
Blood re-collects in large cavity surrounding
heart and then enters heart to be pumped
again
Open vs. Closed Circulatory Systems
Open vs Closed Circulatory
Systems
How do Arthropods get rid of their SOLID
wastes?
 A. the solid waste exits back through their
mouths
 B. The solid wastes exit through their anus
 C. The solid wastes exit through their
spiracles
 D. The solid wastes exit through their
Malpigian tubules
 E. The solid wastes exit through their
sinuses
Answer: B
How do Arthropods get rid of their
nitrogenous wastes?
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A. the N2 wastes are concentrated by
their Malpigian tubules
B. the N2 wastes are excreted through
their anus
C. the N2 wastes are excreted through
their spiracles
D. The N2 wastes are concentrated by
their tracheal tubes
E. The N2 wastes are excreted through
their gills
Answer: A, B, E
Excretion
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Solid waste exits
through anus
Insects and spiders
remove nitrogenous
wastes with
Malpighian tubules
that are in the blood
sinuses
Nitrogenous wastes
are concentrated by
tubules and added
to solid waste for
excretion.
Where (in their bodies) do Arthropods have structures
to get rid of nitrogenous waste structures?
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A. their head
B. their abdomen
C. the base of their legs
D. their tracheal tubes
E. the ends of their antennae
Answer: A, B, C
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
Some terrestrial
arthropods may also
have excretory
glands on base of
legs.
Some arthropod
have these glands
instead of
Malpighian tubules
Aquatic Arthropod
Excretion
Excrete
metabolic
wastes
through gills.
 Lobsters also
have a pair
of green
glands on
(green gland)
their head
that
eliminate
nitrogenous
wastes!

How are Arthropods’ nervous systems different than
humans?
 A. We have a brain, they only have ganglia
 B. Our brain controls all our body except for
reflexes; their brain controls some but not all of
their functions
 C. We have a nerve cord; they do not have a
nerve cord
 D. our nerve cord is on our dorsal surface;
theirs is on their ventral surface
 E. Our NS is higher functioning on all levels
than their nervous systems
Answer: B, & D
Response –well developed NS
Have brains in head that act as main coordinator,
and ganglia in each segment that coordinate
movement in that segment.
 Brain and ganglia are connected by a ventral
nerve cord
How do compound eyes differ from Human eyes?
a. Compound eyes do not have the ability to focus
an image as well as our eyes can
b. Compound eyes do not see color
c. Compound eyes can focus much better than our
eyes because they have SO many lenses to work
with. Our eyes only have one lens.
d. Compound eyes see motion much better than
our eyes can.
e. Compound eyes produce larger images than our
eyes
Answer: A, D
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Sense organs
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Have simple
organs –
statocysts and
chemoreceptors
Most also have
more
complicated
organs
Compound eyes
are common
> 2000
separate lenses
– excellent at
detecting colour
and movement
(better that we
can!)
Most can detect
UV light
Where do Arthropods have taste buds?
a.
b.
c.
d.
e.
Tongue
Mouth parts
Legs
Abdomen
antennae
Answer: B, C, E
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Crustaceans
and insects
have a good
sense of taste
“Taste-buds”
located on
mouthparts,
legs and
antenna
Also have hairs
that detect
motion very
well
How are insect ears different than human ears?
a. Human ears can hear much higher frequencies than
insect ears
b. Human ears hear much lower frequencies than insect
ears
c. Human ears have “ear drums” that are inside the
head and much more protected than the “ear drums”
of insects.
d. Human ears are much better at detecting sound than
insect ears
e. Human ears are not as good as insect ears at
detecting sound at normal ranges.
Answer: C
Where are the “ear drums” (tympanic
membranes) on a grasshopper?
a.
b.
c.
d.
e.
On
On
On
On
On
their
their
their
their
their
Answer: c
heads
thorax under their wings
abdomen behind their legs
abdomen at the very end
antennae

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Many insects
have ears that
hear frequencies
higher than we
can
Eardrums are in
different places –
eg. Grasshopper
have eardrums
behind their legs
How do insects protect themselves from
predators?
a. They sting or bite or pinch
b. They are poisonous
c. They can drop an appendage (sacrifice a limb) and
run away
d. They can camouflage themselves
e. They mimic other animals that are poisonous
Answer: All of the above!
Protection
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Exoskeleton and good NS help
Some sting, some bite, some pinch, some
are poisonous
Some crabs drop a claw that continues to
move while they escape
Some have camouflage
Some mimic other animals that are
poisonous
Bee Stinging
Camouflage
mandibles
Mimicry
Biting
Mimicry
How do insects move their bodies?
a. They use jet propulsion like octopi or squid. On
land they use their spiracles and tracheal tubes to
move air instead of water.
b. They have cilia that move them through the grass
or the water
c. They swim in the water
d. They use muscles to move their exoskeletons
similar to how humans use muscle to move their
endoskeletons
e. They have special tissue that moves their
exoskeleton from the outside.
Answer: D
Movement
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
Move with
muscles
coordinated
by NS
Muscles use
exoskeleton
as we use
endoskeleton
to move
What is the most common form
of reproduction for arthropods?
a.
b.
c.
d.
e.
External fertilization
Internal fertilization
Spore formation
Egg production
Internal development
Answer: B, D
Reproduction
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
Most is internal
fertilization via
special male organ
Spiders and some
crustaceans leave a
package of sperm
for the female to
pick up
How does an arthropod remove its
exoskeleton when it needs to molt?
a.
b.
c.
d.
The exoskeleton will crack when the
arthropod’s body becomes too large
The arthropods have a special internal
appendage that can break open the
endoskeleton from the inside.
The epidermal layer digests the inner
exoskeleton layer to re-cycle the chitin
The arthropod must find a sharp object to
scratch against to weaken the endoskeleton
until it break through
Answer: C
Growing Requires MOLTING
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Coordinated by
hormones
1. The epidermal
layer digests the
inner exoskeleton
layer to re-cycle the
chitin
2. Arthropod body
excretes a new
exoskeleton (inside
the old one)
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3. Animal cracks the
old exoskeleton and
crawls out
4. May eat the old
exoskeleton
5. Animal stretches
the new exoskeleton
to larger size (is
done by pumping
extra water into the
body in aquatic
arthropods)
New, larger
exoskeleton will
then harden
Grasshopper eating
exoskeleton
Metamorphosis – A Drastic
Change!

Insects demonstrate
2 forms of
metamorphosis –
complete and
incomplete
Incomplete metamorphosis:
a. Insects enter the pupae stage but
emerge without making the complete
change in
Incomplete Metamorphosis
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
grasshoppers,
mites, and
crustaceans
the egg hatches
into an immature
animal that looks
like the adult but
lacks sex organs
and other structures
such as wings
Complete Metamorphosis

Bees, moths, beetles
4 stages:

1. Eggs

1. Eggs

2. Larvae – hatch
from eggs. Look
different from adult
Grow bigger and
molt several times.
Hang upside down
In “j” the day before
It turns into a pupa
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3. Pupa – the last
molt of a larva
Often has a
protective coating
Body completely
changes and
rearranges. Old
parts are digested to
recycling the
materials
just about ready to emerge


4. Adult – emerges
from the pupal
coccoon.
Even the animals
behaviour will be
different than the
larval stage
Hormones, Molting and
Metamorphosis


Molting hormone
interacts with other
hormones such as
“juvenile” hormone
When juvenile hormone
is high, the animal
continues to molt into
the larval stage. Each
molt causes the animal
to produce less
hormone

At a critical lower
level of juvenile
hormone, the animal
will molt into the
pupa

When juvenile
hormone is
completely gone
from the system,
the pupa molts into
the adult


Some plants use
chemicals that
mimic insect
juvenile or molting
hormone as a
defence
mechanism
Insecticides will
also do this