Download Insects and Their Relatives

Intro to Arthropods
Arthropods and Their Relatives
• Characteristics
– Exoskeleton (external covering made of CHITIN)
– Molts or sheds exoskeleton to grow
– Jointed appendages - groups very often named in
relation to number or type of feet.
– Tend to undergo metamorphosis or pass through a
number of distinct growth stages during their lives
– Tendency toward high degree of cephalization,
especially in Class Insecta
Arthropods
• Relative abundance.
– 3/4 of all known species of animals are
arthropods. (
– More known species of arthropods than
known species of plants and animals
combined. Great diversity in form and
habitat.
Major Groups of
Arthropods
• Subphylum
Trilobita - all
forms extinct
(believed) perhaps
some of earliest
arthropods
Major Groups of
Arthropods
• Subphylum Chelicerata First pair of appendages
form chelicera or pincherlike structures used for
feeding. 4 pair of walking
legs, no antennae. The
Arachnida is the only
important group.
Other examples of Chelicerates: horseshoe
crabs, sticks, scorpions
Chelicerates Include the
Horseshoe Crab
Major Groups of
Arthropods
• Subphylum Crustacea - mostly aquatic, most
have gills, two pair of antennae. Biramous
appendages, meaning limbs have more than one
branch. Also have mandibles. Some are
parasitic but we will not cover them.
Examples of Crustaceans:
Pill bugs, crabs, crayfish, lobsters
Major Groups of
Arthropods
•Subphylum Uriramia – single branch
or uriramous appendages, mandibles,
one pair of antennae
• Diplopoda - Millipedes - two pair of legs
per body segment
• Chilopoda - Centipedes - one pair of legs
per body segment
• Insecta - 3 pair of legs on adults, many
with wings, most important group
Fundamental External
structure
• Insects
– 3 body regions
• head
• thorax
• abdomen
– 3 pair legs attached to thorax
– 1 pair antennae
– wings usually present in adult state.
Hind Wing
Fore Wing
Antennae
Simple Eye
Compound Eye
Jumping Leg
Mouth
Cerci
Ovipositor
Palps
Spiracles
Abdomen
Walking Legs
Thorax
Head
External structure of Subphylum
Chelicerata, Class Arachnae
• Chelicerates have specialized mouthparts called
chelicerae – think of the hooked grabbers!
• Arachnids (spiders and mites)
– 2 body regions
• Cephalothorax
• abdomen
– usually 4 pair legs
– no wings
– no antennae
Body of Arachnids
The Spider Body
A spider's body is
divided into two parts:
Cephalothorax Fused head & thorax.
The legs are located
on the cephalothorax
Abdomen - Similar to
that of insects..
Other Members of Phylum
Arachnida (4 Pairs of Walking
Legs)
1. Spiders
2. Ticks and Mites
3. Scorpions
Nature Says Don’t Bug Me
with the Colour Red!
How Nature Says Do Not
Touch
Feeding and Digestion
-Arthropods can be herbivores,
carnivores, and omnivores.
-They can be bloodsuckers, filter
feeders, detritivores, or parasites
Feeding and Digestion
Their mouthparts range from pincers
to fangs to sickle-shaped jaws
Chelicera = Fangs, for example,
on a Spider
Respiratory System
• Some arthropods have a network of branching
tracheal tubes that extend throughout the body.
Air enters and leaves the tracheal tubes through
spiracles (small openings located along the side of
the body)
• Gills or lungs, as you’ll see on the next slide 
• Organism is too large to rely on surface area.
That is, the internal volume is too great to be
supplied with oxygen from a minimal SA.
Book Gills – folded Gills
increase SA for Respiration
Horseshoe Crab
Book Lungs are Characteristic of
Arachnids
Circulatory System
•
•
•
•
Open circulatory system
Well developed heart pumps blood
Heart is long and narrow
Arteries branch into blood vessels
and return blood to the heart via
veins – cool, just like us!
Excretion
• Recall the Nephridia in Annelids
• The Malphigian Tubules in Arthropods collect
nitrogenous wastes in the tubules from blood
• Wastes are concentrated (like a kidney does.)
• Excreted out anus
- In aquatic arthropods, cellular wastes are
diffused into the water
Response and Sensory
Adaptations
• Well developed nervous
system – brain!
• Have nerve cords connected
to ganglia that coordinate
the movements of legs and
wings
• Compound eyes with many
lenses give Mosaic Vision or
multi-images
Ultravision – Seeing in
the UV Spectrum
The Compound Eye
Each crystalline eye
generates an image. All
images together generate a
mosaic effect
Simple Eye (Ocelli)
• Do not form the picture
• Just gather light
• Tell whether it’s light or dark
Movement
• Arthropods have muscles coordinated
by the nervous system
• Different muscles flex or extend the
joint, pulling on the exoskeleton
Exoskeleton
of Chitin and
Muscles
attach on
Inside
Reproduction
• Terrestrial arthropods: internal
fertilization
 male places sperm in female
 male deposits sperm packed
that is picked up by female
• Aquatic arthropods: internal OR
external fertilization
Metamorphosis
• Simple or gradual
– three changes
• egg
• nymph
– Lack adult structures
• adult
– adults and nymphs
• eat same food
Metamorphosis
• Complex or complete
– four changes
•
•
•
•
egg
larva
pupa
adult
– larvae and adults
• eat different food
– larvae are destructive
How do You Grow Larger if you
Skeleton is on the Outside?
Molt, or
shed the
outer
covering
Today’s task
•
In your groups, summarize and present
one of the following topics.
Make sure to include labelled diagrams
and key terms!
Groups 1 + 2: Crustaceans (pp.720-721)
Insects and Relatives (p.725)
Groups 3 + 4: Spiders and relatives (pp.722724)