Warm Up What are the three groups of mollusks?

Invertebrates - Arthropods “Jointed Legs”

Mollusks, Arthropods, and Echinoderms Arthropods “Jointed Legs” Chapter 10 Section 2

Discover Activity Will it bend or move? Page 335

Objectives: To identify four major groups of arthropods and the main characteristics of arthropods. To describe how crustaceans, arachnids, and centipedes and millipedes differ.

Arthropods Arthropoda is the phylum of invertebrates that contains the greatest number of species. Animals that make up this phylum include crustaceans, centipedes and millipedes, arachnids and insects.

Characteristics The three characteristics shared by all arthropods: 1. An exoskeleton. 2. A segmented body. 3. Jointed appendages.

Exoskeleton An exoskeleton is the most striking characteristic of arthropods. An exoskeleton is a rigid outer covering. (Think of a suit of armor.) One drawback of an exoskeleton is that it doesn't grow as the animal grows. It must be shed and replaced from time to time in a process called molting. Helps prevent water loss, so arthropods can live in very dry climates.

Lobster Exoskeleton Dismantled The exoskeleton of a lobster is divided into a series of segments, each of which performs specialized functions. The cephalothorax, consisting of the head and thorax, bears all of the limbs used in sensory perception, locomotion, breathing, and the detection and capture of prey. The abdomen is divided into six segments that are responsible for rapid locomotion.

Systems Open circulatory system Blood is not contained within small tubes Pumped by a heart throughout spaces within the arthropod’s body Respiratory system, may have one or two of the following systems Gills Book lungs System of air tubes Reproduce sexually

Generalized Anatomy of a Crustacean Crustacean anatomy is characterized by an external skeleton and a segmented body. In different crustacean species these segments and the accompanying limbs have evolved into specialized appendages for respiration, swimming, crawling, and feeding. The extended inner cavity contains the digestive and nervous systems.

Crustaceans

Crustaceans include Crabs Lobsters Barnacles Shrimp

Body Divided into segments Pair of appendages is attached to each segment Some crustaceans can regenerate certain parts of their bodies Live in watery environments Have gills

Fairy Shrimp Hermit Crab Gooseneck Barnacles

Brine Shrimp Spider Crab Spot Prawn

Coconut Crab Climbing Tree

Pill bug

Centipedes and Millipedes

Centipedes one pair of legs in each body segment carnivores. Millipedes two pairs of legs in each body segment herbivores.

Centipede Millipede Peruvian Centipede

Arachnids

spiders scorpions ticks mites

Arachnids An arachnid's body is divided into two parts: 1. A head and chest part. 2. An abdomen part. All arachnids have four pairs (8) of walking legs. Spiders usually feed on insects (which is good!)

Spiders Many spiders make webs. All spiders produce silk, which is 5 times stronger than steel. Catch prey in a variety of ways. Inject venom or poison using fangs, which either kill their prey or paralyze it. Have book lungs, which are several sheets of tissues which resemble pages.

Generalized Anatomy of an Arachnid

African Wolf Spider

Wolf Spider Web of the Funnel Spider

Scorpions Usually found in dry desert areas Primarily active at night Hide under logs, stones or in holes during the day Capture prey, hold it with their front claws and inject it with venom through the stingers in their tails

Scorpion Sahara Fat-tailed Scorpion

Scorpion Tail A scorpion’s tail usually curves upward and forward over the back. A stinger at the tip of the tail contains a pair of poison glands. A scorpion paralyzes prey by a sting with its tail. Microsoft ® Encarta ® © Microsoft Corporation. All rights reserved.

Ticks and Mites Ticks and mites live on other organisms. Many mites suck fluid from plants. Some ticks and mites are very tiny and live on insects. Many ticks suck blood from larger animals. They spread diseases like Rocky Mountain spotted fever or Lyme disease.

Dust Mite

Sheep Tick Chigger

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