phylum arthropoda. arthropoda classification phylum arthropoda subphylum uniramia- (terrrestrial...
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Phylum Arthropoda
Arthropoda Classification
Phylum ArthropodaSubphylum Uniramia- (terrrestrial mandibulates)
Class Chilopoda- centipedesClass Diplopoda- millipedesClass Insecta- insects
Subphylum Crustacea- (aquatic mandibulates) lobsters, crabs, crayfish, shrimp, sow bugs (pill bugs), krill and barnacles
Subphylum ChelicerataClass Arachnida- spiders, scorpions, ticks, and mitesClass Merostomata- horshoe crabClass Pycnogonida- sea spiders
Subphylum Trilobita- trilobites (extinct)
ARTHROPODS
The phylum Arthropoda includes lobsters, spiders, scorpions, millipedes, & insects; it encompasses over one million species. They
are the most abundant of all the visible animals.Arthropods live virtually everywhere, and their influence on man &
the environment is great.
Negative Influences1. Can destroy crops2. Compete with other animals
for food3. Transmit deadly diseases4. Annoying pests
Positive Influences1.Produce valuable things such as
wax, honey, drugs, & silk.2.Help maintain plants & crops by
assisting cross-fertilization3.Help control the number of
harmful arthropods4. New & better machines have
been designed after them5. Food source for other organisms6. Recycle nutrients by
decomposing things
Arthropoda Influence
Characteristics of Arthropods1. Exoskeleton--non-living body covering secreted by the
epidermis.Three layers of the exoskeleton:
A. Outer layer--coating of proteins and lipids that repel water and prevent water loss (in land species)
B. Middle layer--supporting layer; primarily protein & chitin Chitin--chemical component (polysaccharide) that gives the body
covering toughness & flexibility. C. Inner layer--similar to middle layer but provides more flexibility at the
joints.
• Mineral salts in the exoskeleton protect the animal from harsh chemicals in its environment and from the attacks of predators.
Important Polysaccharides
Four Important Polysaccharides:• Starch ~ used for energy storage for plants; major source
of energy for animals.• Glycogen ~ starches from plants are broken down and
made into glycogen for temporary storage in animals• Cellulose ~ chains of glucose molecules found in plant
cell walls; structural; large molecules that most animals can’t digest.
• Chitin ~ strong, insoluble yet very flexible, similar to cellulose. One of the most abundant polysaccharides in nature, makes up the exoskeletons of arthropods (insects, crustaceans, spiders); structural
Figure 3.7
Starch granulesin potato tuber cells
Glycogen granulesin muscletissue Glycogen
Glucosemonomer
Starch
Cellulose
Hydrogen bonds
Cellulosemolecules
Cellulose microfibrilsin a plant cell wall
ExoskeletonPros1. Provides more
protection from predators and the environment
Cons1. The weight of the armored
body covering limits the size of the animal
2. Poses an obstacle to growth
• Molting--to shed its covering in order to grow. To molt, the arthropod epidermis produces enzymes that eat away at the inside of the old exoskeleton while a new exoskeleton is produced beneath it. Once free from its former exoskeleton, an arthropod may go into seclusion until its new, expanded exoskeleton hardens.
2. Jointed Appendages--"arthropoda" means "joint-footed" and describes the appendages of this group. The muscles of the arthropod move the limbs from within the exoskeleton. Variety of form & function in arthropod appendages: A.Limbs, legs--ex. spider, grasshopper--for locomotion B.Fangs--ex. centipede--enable it to capture & chew its food. C.Claws--ex. lobster, crabs--means of defense. D.Antennae--ex. insects--sensory reception. E.Stinging tail--ex. scorpion--defense and predation.
Characteristics of Arthropods
3. Body Segmentation--body of the typical arthropod is divided into 3 segments:
A. headB. thoraxC. abdomen
• the head and the thorax are often united into what is referred to as the cephalothorax
• these body segments are designed for specific functions.
Characteristics of Arthropods
4. Open circulatory system w/ a dorsal heart--the dorsal heart pumps blood through short vessels that empty into cavities within its body and bathe its organs.
Characteristics of Arthropods
5. A ventral nervous system--arthropod nervous system consists of a "brain" (a pair of ganglia) centered over the esophagus and joined by 2 major nerves to a ganglion below the esophagus, and a ventral nerve cord.
Characteristics of Arthropods
VENTRAL NERVE CORD
*Ventral location provides protection and places it in close proximity to the appendages which are the structures most often requiring nervous commands and coordination.
Nervous system organs:
• Antennae--appendages in the head region; provide taste, smell & touch sensation to most arthropods.
• Compound eyes--(in most insects & crustaceans) contain thousands of individual lenses set at slightly different angles providing a mosaic view.
• Simple eyes--(like in spiders) contain only one lens and have very limited view.
ANTENNAECOMPOUND EYES
SIMPLE EYES