Transcript Arthropods 09
Arthropods
Phylum Arthropoda Arthropods
Largest and most successful phylum 75% of all animals!
Segmented body Tough exoskeleton Joint appendages (legs and antennae) Cephalization Bilateral Symmetry
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)
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
Feeding
Feeding
– Includes herbivores, carnivores, omnivores, detritivores, filter feeders, bloodsuckers, and parasites.
– Mouth parts adapted to type of food eaten Pincers, fangs, jaws
RESPIRATION
• Terrestrial arthropods: breathe through
tracheal tubes
• Air enters and leaves tracheal tubes through
spiracles
• small openings located along the side of the body.
Tracheal tubes Spiracles Tracheal tubes
RESPIRATION CONTINUED…
•Book lungs organs that have layers of respiratory tissue (stacked like pages of a book.) •Spiders, scorpions, horseshoe crabs
Circulation and Excretion
Arthropods have a open circulatory system No distinction between blood and other fluids Malpighian tubules organs that extract waste from the blood (terrestrial): saclike Diffusion (aquatic)
Response and Reproduction
Response
– 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
Reproduction
Separate sexes sexual reproduction Males directly transfer sperm to females Ex. Barnacle stretches out appendage to local females Mating occurs after female molts
MOVEMENT
Movement: Groups of well developed muscles coordinate movement – generating force by pulling on the exoskeleton – Muscles flex (bend) or extend (straighten) the joint.
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 – http://upload.wikimedia.org/wikipedia/c ommons/6/62/Cicada_molting_animate d-2.gif
Groups of Arthropods
Classified by number of body segments and mouth parts 3 major groups 1. Crustaceans 2. Spiders and their relatives 3. Insects and their relatives
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
Body Plan of Crustaceans
swimmerets
Cephalothorax
– Fusion of head with the thorax
Mandible :
– Mouthpart adapted for biting and grinding food
Cheliped
•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
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
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
Male Jonah Crab
Female Jonah Crab
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)
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.
Horseshoe Crab
1. Carapace 2. Telson 3. Compound eye 4. Anterior spine Five pair of legs
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
What does the spider use silk for?
Silk glands Spinnerets
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
3) Uniramians
Centipedes, millipedes, and insects Characteristics of Uniramians – Have jaws – One pair of antennae – Un-branched appendages – Carnivores
Class
Insecta
(Insects)
Characteristics of Class Insecta – Contains most species of any other animals – Body divided into 3 segments Head, thorax, and abdomen
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
Response
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
Feeding and Specialized Mouth
Parts
3 pairs of appendages that are used as mouthparts, including a pair of mandibles
Ant
Specialized mouth parts continued…
Spongelike mouthpart used to lap up food
Fly
Specialized Mouth Parts
Tubelike mouthpart used to suck nectar
Moth
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
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
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.