Intro To Arthropods
HW: Complete page 1 in RB 2 (Resource
book 2 – the pink one)
Overview
Arthropods have been around for 500 million years.
There are about a million known species of
arthropods.
– This are more species in this one phylum than you would
get by grouping all members of all other phyla together.
There are 160 million insects for each person on this
Earth.
There are so many copepods & tiny crustaceans that
together they outweigh all the whales on Earth.
Habitat
Given that there are a million of different species, they are
found in almost all habitats on Earth.
– Many crustaceans live in the sea at depths exceeding 4,000
metres. (That’s 2.5 miles deep)
– Insect collembolans and jumping spiders have been found on
Mount Everest at heights exceeding 6,700 metres. (That’s 4
MILES high.)
– Collembolans and the orbatid mites live in Antarctica.
– Brine shrimp are found in some saltwater lakes.
– Beetles, mites, and various crustaceans can live in hot springs.
– Tiny crustaceans inhabit underground waters.
– Deserts support a large arthropod population, especially insects
and arachnids.
Niches
All are free-living, and the aspects of their niche that affect
humans include:
– Many species of insects and mites attack food crops and timber.
– Two-thirds of all flowering plants are pollinated by insects.
– Soil and leaf-mold arthropods, which include insects, mites,
myriapods, and some crustaceans (pill bugs),
play an important role in the formation of humus from decomposed
leaf litter and wood.
– To protect themselves many arthropods (insects) will sting their
attacker.
Medical Importance
Medically, arthropods are significant as carriers of
diseases, including:
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Malaria
Yellow fever
Dengue fever
African sleeping sickness (via tsetse flies)
typhus fever (via lice)
bubonic plague (via fleas)
Rocky Mountain spotted fever (via ticks)
Lyme disease (via ticks)
Arthropod Characteristics
What makes an organism an arthropod?
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Exoskeleton
Segmented Body with paired appendages
Bilateral symmetry
One way digestive system (mouth and anus)
Open circulatory system
Separate sexes
Arthropod Subphyla & Classes
There are many different classes of Arthropods,
including:
– Class Merostomata (horseshoe crabs, eurypterids:sea
scorpions)
– Class Arachnida (spiders, ticks, mites)
– Class Crustacea
– Class Chilopoda (centipedes)
– Class Diplopoda (millipedes)
– Class Insecta