Arthropoda By: Torrey, Tracy, and Erin 2 nd period

Symmetry Most Arthropods have bilateral symmetry. But there are some exceptions.

Germ layers & Coelom Arthropods are mostly triploblastic, which means they have 3 layers: ectoderm, mesoderm, and endoderm. The germ layer, mesoderm, forms coelom which is a cavity in the body that holds organs.

Body Development of Arthropods Body is completely covered by the cuticle which is an exoskeleton constructed from layers of protein and chitin Exoskeleton protects animal and provides places for the muscle to attach and move the appendages Molting – in order for Arthropods to grow they must shed the old exoskeleton and produce a larger one Arthropods have well developed sensory organs – compound eyes, olfactory receptors and antennae which are used for touch and smell Arthropods have an open circulatory system where hemolymph is propelled by the heart through arteries and then to hemocoels surrounding the tissues and organs. Hemolymph can reenter the heart through pores The skeleton of an Arthropod is very strong and impermeable to water. These qualities are mostly responsible for why many arthropods moved onto land Specialized organs have developed over time for gas exchange. They must allow for the diffusion of respiratory gases. Examples: gills in aquatic arthropods and tracheal systems in terrestrial arthropods

External Anatomy

Movement Movement is achieved by paired appendages Appendages are located under the exoskeleton Some have swimming appendages, some have wings and others have walking legs

Reproduction/Life Style Most have separate sexes; Sperm usually passed to female in a sealed package (spermatophore); often preceded by elaborate behaviors; Newly hatched juveniles are smaller and often differ from parents in form, food, and habitat; become adults through hormone- controlled metamorphosis.

Specialized Tissue Book lungs - stack of alternating air pockets and hemolymph-filled tissue gills in some Spiracles – small openings that lead to the respiratory system. They are located on the exoskeleton and allows air to enter the trachea. ExoskeletonExoskeleton – external skeleton constructed from protein and chitin. Provides protection for the Arthropod. Compound eyes and Jointed appendages Segmented body Open circulatory system

Classes of Arthropoda Insecta (insects) Crustacea (crustaceans) Myriapoda (millipedes and centipedes) Aracnida (spiders and scorpions) Onychophora (velvet worms) Tardigrada (water bears) Pentastomida( tongue worms) Pycnognida (sea spiders)

Insects: Orders Odonata (dragonflies) Lepidoptera (butterflies and moths) Hymenoptera (ants, bees, and wasps) Dictyoptera (cockraoches and mantids) Siphonaptera (fleas)

Arthropods!

Vocabulary Cuticle – a multi-layer structure outside the epidermis of many arthropods, in which it forms and exoskeleton. It is made of chitin. Molting – the shedding of the cutivle. Arthropods such as insects owe a large part of their evolutionary success to their exoskeleton. Chelicerae – first pair of appendages. Antennae – I think we all know! Malpighian Tubules – is a type of excretory system. Had tubules that extend and absorb water, wastes.

Vocabulary Open circulatory system – hemolymph (fluid) is propelled by the heart through arteries and then into hemocoels (sinuses surrounding the tissues and organs). Mandibles – mouth parts used for biting, cutting and holding food. Compound eyes – visual organ in arthropods that consist of ommatidia. Metamorphosis – how an animal physically develops. –1) complete - egg  larvae  pupa  adult. –2) incomplete – egg  nymph  adult.

Review 1. Describe metamorphosis in your own words. 2. What is the difference between complete and incomplete metamorphosis? 3. What are three classes of Arthropod? 4. What are the three germ layers of Arthropoda?