Download Phylum Arthropoda

Phylum Arthropoda
Arthropoda Classification
Phylum Arthropoda
Subphylum Uniramia- (terrrestrial mandibulates)
Class Chilopoda- centipedes
Class Diplopoda- millipedes
Class Insecta- insects
Subphylum Crustacea- (aquatic mandibulates) lobsters,
crabs, crayfish, shrimp, sow bugs (pill bugs), krill and
barnacles
Subphylum Chelicerata
Class Arachnida- spiders, scorpions, ticks, and mites
Class Merostomata- horshoe crab
Class 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.
Arthropoda Influence
Negative Influences
1. Can destroy crops
2. Compete with other animals
for food
3. Transmit deadly diseases
4. Annoying pests
Positive Influences
1.Produce valuable things such as
wax, honey, drugs, & silk.
2.Help maintain plants & crops by
assisting cross-fertilization
3.Help control the number of
harmful arthropods
4. New & better machines have
been designed after them
5. Food source for other organisms
6. Recycle nutrients by
decomposing things
Characteristics of Arthropods
1. 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 granules
in potato tuber cells
Glycogen granules
in muscle
tissue
Cellulose microfibrils
in a plant cell wall
Starch
Glucose
monomer
Glycogen
Cellulose
Hydrogen bonds
Cellulose
molecules
Exoskeleton
Pros
1. Provides more
protection from
predators and the
environment
Cons
1. 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.
Characteristics of Arthropods
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. head
B. thorax
C. 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.
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.
ANTENNAE
COMPOUND EYES
SIMPLE EYES