The Arthropods

*Phylum Arthropoda

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*Arthropods are by far the most successful of all animals

*Well over 1,000,000 species

*Some say over 30 million species of insects alone!

*There are around 200 million individual insects alive at any given time for each human!

*Arthropods exhibit these key features:

*Exoskeleton: made of chitin, and must be molted (shed) in order to grow

*Segmentation: the body is divided into sections

* Jointed appendages: (arthropod means ‘jointed feet’) they may be modified into antennae, mouthparts or legs!

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*Key features of Arthropods cont.

*Circulatory System: they have an open circulatory system (no veins or arteries) but a heart is present

*Nervous system: they have a brain but also ganglia are in each segment. This results in the arthropod being able to carry out functions like eating, moving and reproducing without a brain present!

*They also have compound eyes: hundreds or more of independent eyes www.teachersparadise.com

*Key features of Arthropods cont.

*Respiratory System: Marine arthropods have gills

*Spiders have book lungs (leaf-like plates within a chamber)

*Terrestrial arthropods have tracheae (small branched ducts that eventually network to each cell) with the opening to the air called spiracles

*Excretory System: aquatic arthropods diffuse most waste through gills, terrestrial insects have Malpighian tubules (slender projections from the digestive tract into the blood, wastes diffuses into them)

2004, Pearson Education

*Spiracles and trachea: Malpighian tubules:

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*Digestion/feeding: varied and complex, range from predators to herbivores, complete digestive system present

*Reproduction: sexual, lay eggs, may include metamorphosis

*Movement: jointed appendages! Fly, walk, or swim

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*Class Chelicerata: spiders, mites, ticks, horseshoe crabs

*Class Crustacea: crabs, shrimps, lobsters, and pill bugs

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*Class Crustacea: crabs, shrimps, lobsters, and pill bugs

*Class Crustacea: crabs, shrimps, lobsters, and pill bugs

Class Crustacea: crabs, shrimps, lobsters, and pill bugs

*Class Crustacea: Even barnacles!

*Crustacea anatomy: the crayfish

*Chelipeds: for defense and prey capture

*Swimmerets: for locomotion and reproduction (holds eggs)

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*Class Hexapoda: The insects!

*Class Hexapoda: The insects!

*Insect Anatomy:

*Body divided into three segments: head, thorax and abdomen

*Mandible for crushing food

*Class Myriapoda: Centipedes and Millipedes