13. phylum arthropoda notes
Post on 19-Oct-2014
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Phylum Arthropoda
Kingdom Animalia
Phylum Arthropoda
Subphylum Crustacea
Class Cirripedia
Class Copepoda
Class Malacostraca
Order Decapoda
Order Euphausiacea
Subphylum Chelicerata
Class Merostomata
Class Pycnogonida
Arthropods Largest phylum of
animals 1 million species
(some estimates say up to 20 million)
Includes mainly terrestrial bugs
3 out of every 4 animals are arthropods
General Characteristics of Arthropods
Segmented body Bilateral Symmetry Jointed
appendages Chitinous
exoskeleton
Sub Phylum Crustacea
Includes: Shrimps Crabs Lobsters Barnacles Potato Bugs
(terrestrial)
General Characteristics of Crustaceans
Two pairs of antennae
Mandibles for chewing
Pair of appendages on each body segment
Gills for oxygen
Molting
To grow, arthropods must molt their exoskeleton
Digestion Smaller crustaceans
are filter feeders, catching particles in bristles on their appendages
Some have specialized appendages that push food towards their mouths
Nutrients passed to an open circulatory system
Nervous System
Can vary from simple ladder-like to centralized nervous systems
Most have compound eyes
Keen sense of smell Communicate with
each other via body postures
Compound Eyes
Bundles of up to 14,000 light sensitive units grouped together
Some on stalks that can be used like periscopes
Class Cirripedia
Filter feeders Attached to surfaces
including living ones Look like mollusks
because of their shells Others lack plates and
are highly developed parasites
Class Copepoda
Abundant and important in the role of plankton
Can use their antennae to swim
“Sea Monkeys”
Importance of Copepods
1. Most numerous multi-cellular animals on Earth
2. Eat the tiniest plankton and are in turned eaten by fish & krill
3. Fecal pellets shorten the nutrient cycle of the ocean
Order Decapoda
“ten legs” Largest
crustaceans in terms of size
Extended carapace Shrimp, lobsters,
and crabs
Order Decapoda
Five pairs of walking legs (pereopods) of which one is usually heavier (claws)
Carapace encloses the cephlalothorax with the rest of the body being the abdomen
Order Decapoda
Shrimp and lobsters can range from scavengers to parasite removers
Crabs tend to be scavengers
Order Euphausiacea Krill Planktonic Shrimp-like Head fused with body
pieces to form a unique carapace
Major food source for larger organisms (whales, seals, penguins, etc.)
Sub Phylum Chelicerata Includes Horseshoe
crabs, spiders, mites Chelicerae are the
only small appendages before the mouth
Range from small pinchers to venomous fangs
Class Merostomata Horseshoe Crabs Not true crabs and have
not evolved for millions of years
Six pairs of appendages No mandible jaw Chelicerae, Walking Legs,
four pairs of Pushing Legs Telson or tail used for
steering and flipping itself right side up.
Class Pycnogonida
Sea Spiders Have four or more pairs of
legs A large proboscis with a
moth on the tip allows it to feed on soft invertebrates
No respiratory system as gases diffuse through body
Tiny muscles consist of one cell covered with connective tissue