Download Insects and Their Relatives

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
• Subphylum Chelicerata - First pair of
appendages form chelicera or
pincher-like structures used for
feeding. 4 pair of walking legs, no
antennae. The Arachnida is the only
important parasitic group.
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.
• Subphylum Uriramia – single branch or
uriramous appendages, mandibles, one pair of
antennae
Major Groups of
Arthropods
• 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
Metamorphosis
• Simple or gradual
– three changes
• egg
• nymph
– 3-5 instars
• 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
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
Circulatory System
•
•
•
•
Closed 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.) Why concentrated?
• Excreted out anus
Book Gills – folded Gills
increase SA for Respiration
Horseshoe Crab
Respiratory System
• 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 Lungs are Characteristic of
Arachnids
Sensory Adaptations
• Well developed nervous
system
• 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
Exoskeleton
of Chitin and
Muscles
attach on
Inside
How do You Grow Larger if you
Skeleton is on the Outside?
Molt, or
shed the
outer
covering
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
Chelicera = Fangs, for example,
on a Spider
Chelicerates Include the
Horseshoe Crab
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