Download Chpt 28 Arthropods - Phylum Arthropoda o Arthro = jointed o Poda

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Chpt 28 – Arthropods
Phylum Arthropoda
o Arthro = jointed
o Poda = feet
They are animals with jointed appendages
They also have an exoskeleton
Have segmented bodies
o There is a great amount of diversity
They have been around for over 600 million years
o Aquatic – fresh and marine
o Terrestrial
o Air???
Do not live in water, nor the ground therefore air
Body Plan
o Have an exoskeleton
Outside of their body
Mostly make up of chitin (a carbohydrate)
May be leathery and flexible
• Ex) a caterpillar
May be hard and ridged
• Ex) crab or beetles
Its function is to provide protection and for terrestrial and aerial
arthropods, it also protects against water loss
o Have jointed appendages
Mostly for movement
• With an exoskeleton, without joints, the animals could not move
• Ex) antenna, claws, legs, wings, flippers
o Has segmentation with cephalization
Some of the animals have some segments that are fused together
• Gives them a 2 part body plan instead of a 3 part body plan
• Ex)the head and thorax of a crayfish is fused together therefore it
is called a cephalothorax
o There are all types of feeders
Detritus – crabs and crayfish
Filter feeders – barnacles
Carnivores – spiders, praying mantises
Herbivores – most insects
Parasitic – ticks, mites, lice
o Some may have a very selective diet
Ex) the monarch butterfly larva eats only milkweed
o Some have general diets
Ex) locusts and grasshoppers will eat all types of plants
o Have a tube digestive system
Mouth to anus
Some specialized organs in between
Also have specialized mouth parts depending on their feeding style and
o There are 3 major types of respiratory structures
1 – gills – aquatic – ex) crabs
• Are feather-like appendages under the exoskeleton
• Form from parts of the mouth or legs
o Movement of the mouth or legs keeps water flowing over
the gills
2 – book gills or book lungs –
aquatic or terrestrial
• Ex) horseshoe crab (aquatic)
• Ex) some spiders (terrestrial)
• Consist of several sheets of tissue layered like pages in a book
• Found ventrally on the animal
• There are openings called spiracles to allow air flow
3 – tracheal tubes – terrestrial only
• Ex) all insects and some spiders
• Openings (spiracles) on the abdomen lead to long branching
tracheal tubes that reach into the animals body tissue
• Movement of the body’s tissue cause the tracheal tubes to shrink
and expand allowing for air to flow
Internal transport
o Have a very well developed heart
o Have an open circulatory system
o Some insects have cyanoglobin instead of hemoglobin
Makes their blood green
o Aquatic
Generally done by diffusion
Some aquatic arthropods have a green gland near the base of their
antennae where metabolic waste is emptied
o Terrestrial
Have structures called malpighien tubes that concentrate and excrete the
waste into the intestine
Metabolic waste is removed along with undigested waste
o Have a very well developed nervous system
All have a brain (anterior)
• The brain also has 2 ganglia
From the brain a long nerve cord runs ventrally along the body
There are more ganglia along this nerve cord
• The ganglia coordinates movement of the wings and legs
o They have well developed sensory organs
• On or near the mouth, antennae or legs
Receptors to detect vibrations
• To detect sounds and movement
They have a compound eye
• An eye with 2000 or more separate lenses
• Can detect movement
• Can detect colours (including UV)
Many have the ability to communicate
• Ex) Crickets rub wings (sounds)
o Moths use pheromones to attract a mate (chemicals)
o Bees do a wiggle dance to indicate where flowers can be
found (physical)
• Venom – bite or sting
o Other chemical
o Have bright colours
• Powerful claws
• Camouflage
o Mostly separate sexes
Some hermaphrodites
o Internal fertilization
o Some asexual reproduction
Some can regenerate as well
o There are very complicated life cycles
As they grow, exoskeletons become too small
• Molt – shedding of the exoskeleton
• The new exoskeleton is softer and lacks pigments (for a while)
There are 2 types of life cycles
• 1 – incomplete metamorphosis –
o Metamorphosis = to change
o Has 3 stages
Nymph = small looking adult
• Ex) stick bugs, crickets,
• 2 – complete metamorphosis –
o Has 4 stages
• Ex) butterflies, beetles