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2 From the Greek ἄ ρθρον (árthron - "joint“) & ποδός (podós - "leg“) Includes insects, arachnids, and crustaceans Most abundant and diverse phylum: make up 80% of all living animals Occupy the widest variety of habitats They affect humans both adversely and positively They are the most successful group of land animals PAGE 79

BODY PLAN OF ARTHROPODS 3  Bilaterally symmetrical  Have a coelom  is reduced and replaced by a haemocoel = blood filled space  Triploblastic tissue layers  Cephalisation  A through gut  Segmentation Nervous system similar to Annelids, but sensory organs are more advanced

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HAEMOCOEL 7  A blood filled space  Forms an open blood system with a heart to pump the fluid around  Less efficient than a closed blood system

CLASSIFICATION OF ARTHROPODA 8 Are classified into five subphyla:1. Trilobites2. Chelicerata3. Myriapoda4. Crustacea5. Hexapoda

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TRILOBITES 10  Group of marine animals  Died in the the Permian-Triassic extinction

CHELICERATA 11  Includes spiders, mites and scorpions  Have chelicerae (pincer like mouthparts)  Four pairs of legs  Cephalothorax

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MYRIAPODA 13  Includes millipedes and centipedes  Have many body segments, each bearing one or two pairs of legs

CRUSTACEA 14  An aquatic group  Include lobsters, crabs, barnacles and crayfish  Have branched appendages  And chewing mandibles (mouthparts)

HEXAPODA 15  Made up of insects  Have:  Six thoracic legs  Body divided into head, thorax and abdomen  A single pair of antennae  And compound eyes

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SUCCESS Have an adaptable body plan: Waterproof skeleton made of chitinous cuticle A degree of segmentation Paired, jointed appendages Complex muscle system Development involves metamorphosis 17 Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation.animaldevelopsbirthbodygrowthdifferentiation

18 Chitinous Cuticle Made of lipd, protein, chitin molecules & may be impregnated with calcium carbonate Hardened to various degrees Prevents water loss so that they can live on land Cuticles must be shed regularly to allow animals to grow – called moulting

TO DO 19 PAGE 81LEARNING ACTIVITY 2BODY PLANS OF ARTHROPODS

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