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Lab 7 - Exam Review (Phylum Arthropoda).docx

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McGill University
Biology (Sci)
BIOL 111
Suzanne Gray

Lab 6 Invertebrates II Phylum Arthropoda  The most diverse and complex of the invertebrate phyla  Exhibit cephalization (sense and control organs focused at the anterior end)  Also, exoskeleton and jointed appendages  Example: Crustaceans are highly adapted to aquatic life and very few live on land (i.e. crayfish) Phylum Arthropoda  Crayfish External Anatomy: bilateral symmetry  Body covering: the body of the crayfish is covered by a hard cuticle composed largely of chitin o The covering acts as a protective outer layer (exoskeleton) to which muscles are attached  Body region: consist of the head and throax that are covered by a fused dorsal shield called the carapace with a cervical groove dividing the two regions. Together, the head and thorax are called the celphalothorz o Compound eyes on the head: separate anterior pointed projection of the dorsal shield (called the rostrum) o Abdomen: half the total length  Body Segments: covered by thin flexible chitin permitting movement at the joints  Appendages: Crustaceans o Basal stack: attached to the ventral surface of the body o Two distal branches: exemplified by the swimmeret o Biramous form: two branches o Appendages are said to be homologous o Serial homology: similar structures in different segments  8 segments in the thorax region and 6 in the abdomen region  Biramous form: antennules, maxillipeds, swimmerets, uropods  Serial homology: pharynx, esophagus, crop, gizzard, intestine Table 8.1. Appendages of the crayfish. There are 19 segments with paired appendages. Lab 6 Invertebrates II BODY BODY APPENDAGE FUNCTION REGION SEGMENT Antennule (with statocyst in 1 base) Touch, taste, and equilibrium 2 Antenna (with excretory pore Touch and taste at base) HEAD 3 Mandible (jaw) Crushing and chewing food 4 1 maxilla Food handling Food handling and draws water 5 2 maxilla (with gill bailer) over gills st 6 1 maxilliped Touch, taste, and food handling 7 2 maxilliped* Touch, taste, and food handling 8 3 maxilliped* Touch, taste, and food handling st Defense, food capture and 9 1 walking leg (cheliped)* handling THORAX 10 2 walking leg* Walking and grasping 3 walking leg* (with female 11 Walking and grasping genital pore at base) th 12 4 walking leg* Walking th 13 5 walking leg* (with male Walking genital pore at base) * gills attached to their bases Respiration st 1 swimmeret – male Transfer sperm to female – male 14 1 swimmeret – female No function – female 2 swimmeret – male Water circulation – both sexes 15 2 swimmeret – female Transfer sperm to female – male Carry eggs – female Water circulation – both sexes 16 3 swimmeret ABDOMEN Carry eggs – female th Water circulation – both sexes 17 4 swimmeret Carry eggs – female 18 5 swimmeret Water circulation – both sexes Carry eggs – female 19 Uropod Backward swimming Lab 6 Invertebrates II Respiratory System:  Gills: some extend from the bases of the walking legs and others are attached to the inner wall of the gill chamber (a lateral chamber underneath the carapace)  Can respire on land for a short period of time, as long as there is water trapped in the gill chamber  The gills featherey structure provides an enormous surface area for the diffusion of gases o Water enters under the carapace and is moved over the gills by the beating activity of the gill bailer and the movement of the legs o The stream of water after pas
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