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Presentation on theme: "Arthropods."— Presentation transcript:

1 Arthropods

2 Phylum Arthropoda - Arthropods
Largest and most successful phylum 75% of all animals! Segmented body Tough exoskeleton Joint appendages (legs and antennae) Cephalization Bilateral Symmetry

3 Exoskeleton: an external covering that protects and supports the body
Made from chitin Varies in size, shape, and roughness. Firm and leathery (caterpillars) Tough and hard (crabs and lobsters) Waxy (land dwelling arthropods)

4 Evolution of Arthropods
Fossilized Trilobites Evolution of Arthropods Typical primitive arthropod: many identical segments with a pair of appendages. Evolution led to fewer segments and specialized appendages Photo Credit: ©John Canculosi/DRK Photo. Trilobites, such as the fossilized one shown above, were marine arthropods that were abundant more than 500 million years ago. They were divided into many body segments, each with a walking leg.

5 Feeding Feeding Includes herbivores, carnivores, omnivores, detritivores, filter feeders, bloodsuckers, and parasites. Mouth parts adapted to type of food eaten Pincers, fangs, jaws

6 RESPIRATION Terrestrial arthropods: breathe through tracheal tubes
Air enters and leaves tracheal tubes through spiracles small openings located along the side of the body. Spiracles Tracheal tubes Tracheal tubes The grasshopper has organ systems typical of most arthropods. These organ systems carry out functions such as circulation, excretion, response, and movement. Arthropods have several different types of respiratory organs. In insects, tracheal tubes (inset) move air throughout the tissues of the body.

Book lungs organs that have layers of respiratory tissue (stacked like pages of a book.) Spiders, scorpions, horseshoe crabs

8 Circulation and Excretion
Arthropods have a open circulatory system No distinction between blood and other fluids Malpighian tubules (terrestrial): saclike organs that extract waste from the blood Diffusion (aquatic)

9 Response and Reproduction
Well developed nervous system Brain serves as central switchboard Reproduction Terrestrial arthropods: internal fertilization Place sperm inside female OR deposit sperm packet Aquatic arthropods: internal or external

10 Reproduction Separate sexessexual reproduction
Males directly transfer sperm to females Ex. Barnacle stretches out appendage to local females Mating occurs after female molts

11 Movement: Groups of well developed muscles coordinate movement
generating force by pulling on the exoskeleton Muscles flex (bend) or extend (straighten) the joint. MOVEMENT This diagrammatic representation shows how muscles attached to the exoskeleton bend and straighten the joints. (Actual muscles are much larger than those shown here.)

12 Growth and Development
Arthropods will outgrow their exoskeleton and undergo a period called molting. Molting: the shedding of its entire exoskeleton New/soft skeleton starting to form Controlled by the endocrine system Molting Cicada Video

13 Groups of Arthropods Classified by number of body segments and mouth parts 3 major groups Crustaceans Spiders and their relatives Insects and their relatives

14 1) Crustaceans Primarily aquatic
Includes crabs, shrimps, lobsters, crayfishes, and barnacles. 2 pairs of antennae, two or three body sections, and chewing mouthparts called mandibles. Abdomen Cephalothorax Antennae Antennules Mandible

15 Body Plan of Crustaceans
swimmerets Cheliped Cephalothorax Fusion of head with the thorax Mandible: Mouthpart adapted for biting and grinding food Cheliped: first pair of legs that have large claws modified to catch, pick up, crush, and cut food. Swimmerets: flipper-like appendages used for swimming


17 1) Small Crustaceans Copepods- extremely abundant, planktonic, filter feed Barnacles- usually sessile, filter feed, body enclosed by calcareous plates Krill- planktonic, shrimp-like, have carapace to cover anterior, filter feed



20 True Crabs Small abdomen and tucked under cephalothorax
V-shape ab. in males U-shape ab. in females Largest and most diverse of decapods Scavengers and predators


22 Male Jonah Crab

23 Female Jonah Crab

24 2) Chelicerates Horseshoe crabs, spiders, ticks, and scorpions
No antennae Have mouthparts called chelicerae 2 body sections 4 pairs of walking legs Divided into 2 main classes: Merostomata (horseshoe crabs) Arachnida (spiders, mites, ticks, and scorpions)

25 Horseshoe crabs Horseshoe Crabs
Appeared more than 500 million years ago changed little since that time. Have chelicerae, five pairs of walking legs, and a long spike-like tail (telson) that is used for movement.

26 Horseshoe Crab 1. Carapace 2. Telson 3. Compound eye 4. Anterior spine
Five pair of legs






32 Spiders Food and Digestion
Spin webs of a strong, flexible protein called silk No jaws for chewing must liquefy food using enzymes Use fanglike chelicerae to inject paralyzing venom

33 What does the spider use silk for?
Spinnerets Silk glands

34 Mites, Ticks, and Scorpions
Mites and ticks are small arachnids that are often parasitic Ticks can transmit bacteria that cause serious diseases chelicerae and pedipalps are specialized for digging into a host’s tissues and sucking out blood Scorpions inhabit warm areas around the world. Chew their prey

35 3) Uniramians Centipedes, millipedes, and insects
Characteristics of Uniramians Have jaws One pair of antennae Un-branched appendages Carnivores

36 Class Insecta (Insects)
Characteristics of Class Insecta Contains most species of any other animals Body divided into 3 segments Head, thorax, and abdomen

37 Characteristics continued…
Segmented body Exoskeleton Jointed appendages A typical insect also has: a pair of antennae a pair of compound eyes two pairs of wings on the thorax tracheal tubes that are used for respiration

38 Response Chemical receptors for taste and smell Well developed ears
Compound Eye: made up of many lenses Detect minute changes in color and movement Information from eye is assembled in the brain and directs the insects response Chemical receptors for taste and smell Located on the mouthparts, antennae, and legs Sensory hairs: detect movement in surrounding air or water Well developed ears


40 Feeding and Specialized Mouth Parts
3 pairs of appendages that are used as mouthparts, including a pair of mandibles Mandibles used to saw and grind food Ant

41 Specialized mouth parts continued…
Spongelike mouthpart used to lap up food Fly

42 Specialized Mouth Parts
Tubelike mouthpart used to suck nectar Moth

43 Movement and Flight 3 pairs of legs used for walking, jumping, capturing and holding prey. Legs have spines and hooks that are used for grasping and defense. Flying insects typically have two pairs of wings made of chitin

44 Metamorphosis Process of changing shape and form
Insects undergo either incomplete metamorphosis or complete metamorphosis Incomplete Metamorphosis Look very much like adult form Immature forms are called nymphs lack functional sexual organs and wings


46 Complete Metamorphosis
Animals hatch into larvae that look and act nothing like their parents Feed and grow rapidly and molt a few times Undergo a final molt and change into a pupa stage in which an insect changes from larva to adult.


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