Download Phylum Arthropoda

Phylum Arthropoda
“jointed foot”
“jointed appendages”
the arthropods
Things that creep around on the ocean
bottom (some don’t really creep!);
also crustaceans
and other stuff
General Characteristics
– The largest phylum of animals on earth – three out of four
animals on earth are arthropods
– Include marine barnacles, shrimp and lobsters as well as all
insects
– Have a segmented body
– Bilateral symmetry
– Jointed appendages
– Hard exoskeleton made of chitin
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Tough and non-living
Covers all parts of the animal
Shed when the animal grows – “molting”
Limits size of the animal because it becomes too heavy in larger
animals to allow movement
Feeding and Digestion
• Because of the mandibles and specialized legs, arthropods
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have the ability to eat almost anything
Fill all niches of ecology – carnivores, filter feeders,
herbivores and parasites
Many marine species use their mouthparts or legs to filter
the water
Parasitic crustaceans have their appendages specialized for
sticking onto another organism
The mouth of these organism have the first real teeth like
structures made of chitin
They have a two chambered stomach connected to digestive
glands which release enzymes to aide in digestion
Digestion is extracellular and waste is sent out through the
anus
Respiration
• Arthropods use gills that resemble feathers located
just under their exoskeleton
• Movement of the mouthparts keeps water moving
in a steady stream over the gills
• Land crabs also have gills for respiration – the gills
are kept wet with body fluids and air is passed
over the moistened gills for oxygen absorption
Behavior and Response
• Crustaceans have a small and simple brain
• Most members of this phylum have well defined
sense organs
– Compound eyes – a bundle of light sensitive units
grouped together at the end of a stalk like antennae
– Sense of smell – very sensitive to chemicals in water
• Very complex communication is possible between
members through movement
– Used for courtship and territory protection
Reproduction
• Separate male and female individuals
• Internal fertilization occurs
• Females can store sperm for long periods of time
before they use it to fertilize their eggs
• Females tend to carry the eggs until they hatch
• The young are larvae that are plankton-like and
very rarely resemble the adults
Class Trilobites
• Oldest class from which
the rest of the phylum
evolved
• Lived in all the ancient
seas. Is now the most
common fossil.
Distinguishes the areas
that were occupied by
the organism
• All members of this
class are now extinct
Class Crustaceans
• Specialized for life in the ocean – all members have gills for
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respiration and appendages specialized for swimming
Over 35,000 species exist
Generally characterized by a hard exoskeleton, two pairs of
antennae and mouth parts called mandibles
Have two pair of antennae that are specialize for sensing the
environment
The mandibles are generally short, heavy and specialized for
feeding
Vary in size between microscopic plankton to large lobsters
Main body plan is a head, thorax (area behind the head) and
abdomen (the tail end of the animal)
Class Crustaceans
• Barnacles are part of this class even though they
look like mollusks
– The legs that stick out of the volcano shaped
exoskeleton capture plankton to eat
• Shrimp, lobsters and crabs belong to a group
called decapods have 10 legs
– Prized for food
– Two pairs of the legs are often specialized into claws for
feeding purposes
– Tend to be scavengers
Other Arthropods
– Horseshoe crabs – still the same after
thousands of years, are called living fossils
– Sea Spiders – resemble land spiders, most
common in cold waters and large
– Insects – have only three pairs of legs as
adults, not aquatic but worth mentioning
• Largest and most diverse group on earth; may be
as many as 1-3 million species
• Can live at the sea’s edge scavenging on seaweed
and barnacles