In Greek Arthropoda means “jointed legs”

All Arthropods have 4 common characteristics:

ExoskeletonSegmented body“open” circulatory systemJointed legs

…. But why do they need jointed legs?

Phylum Arthropoda

Arthropods have an “outer” skeleton called an Exoskeleton.

How do arthropods grow bigger, if their skeleton is on the outside of their body?

http://www.youtube.com/watch?v=9c1prdBo4aE

Planaria Feeding

What are Planaria?Freshwater flatworms (phylum:

Platyhelminthes)Live in freshwater under leaves and stonesAvoid light (“negative phototaxis”)Free living – not parasitesCarnivores – eat decaying meat, insects and

larvae (egg yolks or liver in the lab)1-20 mm in sizeLong livedUse sexual or asexual reproduction

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Overview of Brown Planaria

Dugesia tigrina

Planaria are complex organisms

GastrovascularSystem