Arthropodsand

Echinoderms

Phylum Arthropoda Most diverse phylum Most successful of all time About 1 million species have been identified = more than 3 times the number of all other

animal species combined!!

What is an Arthropod Includes insects, crabs, centipedes, and

spiders All have segmented bodies, tough

exoskeletons, and jointed appendages

Exoskeletons Provide protection and support Made of protein and carbohydrate called

chitin Vary in shape, size and toughness Terrestrial arthropods have waxy covering

to prevent water loss

Appendages Appendages: structures such as legs and

antennae that extend from the body wall All are jointed Include antennae, claws, walking legs,

wings, flippers, mouthparts, tails, and other specialized structures

Named for this: arthron means “joint” in Greek, and podos means “foot”

Evolution of Arthropods First arthropods appeared in the sea more

than 600 million yrs. Ago Live in every habitat on Earth: sea,

freshwater, land, and air Evolution has led to fewer body segments

and highly specialized appendages for feeding, movement, and other functions

Form and Function Use complex organ systems Feeding: herbivores, carnivores, and

omnivores Bloodsuckers, filter feeders, detritivores,

and parasites Mouthparts modified for chewing, sponging,

sucking, and probing

Form and Function Respiration Terrestrial arthropods breathe through network of

branching tracheal tubes that extend throughout the body

Air enters and leaves the tubes through spiracles: small openings located on outside of body

Spiders have book lungs: organs with layers of respiratory tissues stacked like a book

Aquatic arthropods use featherlike gills or book gills

Form and Function Open circulatory system Well-developed heart pumps blood through

arteries that branch and enter the tissues Leaves vessels moves through sinuses or

cavities Collects in large sinus surrounding heart Re-enters heart and is again pumped

through body

Form and Function Excretion Terrestrial arthropods use malpighian

tubules: saclike organs that extract wastes from the blood and then add them to feces that move through the gut

Aquatic arthropods use diffusion to move cellular wastes from the body to the water

Form and Function Well developed nervous systems Have brains that receive information and send it

out to muscles Two nerves connect brain to a ventral nerve cord Along nerve cord are several ganglia that

coordinate movements of individual legs and wings

Sophisticated sense organs: compound eyes may have more than 2000 separate lenses to detect color and motion very well

Form and Function Movement by well-developed groups of

muscles made of individual muscle cells that contract and pull on exoskeleton

At each joint, different muscles either flex or extend

Form and Function Reproduction Terrestrial arthropods have internal

fertilization Some put sperm inside female, others

deposit sperm packet that female picks up Aquatic arthropods may have internal or

external fertilization

Growth and Development Exoskeleton does not grow, must be shed as

arthropod gets bigger Molting: shedding of entire exoskeleton and

making a new one Controlled by hormones Can take several hours Makes them vulnerable to predators while

shell is still soft Most hide during molting or molt at night

Groups of Arthropods Arthropods are classified based on the

number and structure of their body segments and appendages – particularly their mouthparts

Subphylum Crustacea Mostly aquatic Includes crabs, shrimps, lobsters, crayfishes,

and barnacles Range in size from small terrestrial pill bugs to

enormous spider crabs up to 20 kilograms Typically have 2 pairs of antennae, 2 or 3 body

sections, and chewing mouthparts called mandibles

Subphylum Crustacea Cephalothorax: anterior, fusion of head with

the thorax Thorax: holds internal organs Abdomen: posterior part of the body Carapace: part of the exoskeleton covering

the cephalothorax

Subphylum Crustacea 1st 2 pairs of appendages are antennae

covered in sensory hairs Used as sensory organs, filter-feeding, or

swimming 3rd pair are the mandibles adapted for biting

and grinding food Gills are attached to appendages associated

with the cephalothorax

Subphylum Crustacea Decapods: crayfish, lobsters, and crabs Largest group of crustaceans Five pairs of legs 1st pair of legs called chelipeds, bear large claws

modified to catch, pick up, crush and cut food 4 pairs of walking legs Along abdomen are several pairs of swimmerets:

flipperlike appendages used for swimming Final abdominal segment is fused to form a large, flat

tail: uropod

Subphylum Chelicerata Includes horseshoe crabs, spiders, ticks, and

scorpions Have mouthparts called chelicerae and two

body segments and 4 pairs of walking legs No antennae Cephalothorax contains brain, eyes, mouth,

and walking legs Abdomen contains internal organs

Subphylum Chelicerata Chelicerae contain fangs used to stab and

paralyze prey Pedipalps used to grab prey Respire with either book gills or book lungs Two main classes: Merostomata and

Arachnida

Subphylum Chelicerata Class Merostomata Includes horseshoe crabs Oldest living arthropods: first appeared 500 mya Not true crabs at all Anatomy similar to spiders Have chelicerae, five pairs of walking legs, and long

spikelike tail Can grow to size to frying pan Common along eastern US coast

Subphylum Chelicerata Spiders: largest group of arachnids Capture food in a variety of ways: webs

made of protein called silk, stalk and pounce on prey (turantula), lie in wait then grab

Feed on animals ranging from other arthropods to small birds

No jaws for chewing, must liquefy food to swallow it

Subphylum Chelicerata Once prey is caught, fangs inject paralyzing

venom Once prey is dead, spider injects digestive

enzymes into the wounds Spider sucks out tissues into a specialized

pumping stomach Food then moves to the rest of the digestive

tract being further broken down by enzymes

Subphylum Chelicerata All spiders produce silk even if they don’t spin webs Stronger than steel! Used for webs, cocoons for eggs, wrappings for prey Force liquid silk through spinnerets: organs that

contain silk glands As silk comes out it hardens into single strand Spinning webs seems to be preprogrammed

behavior

Subphylum Chelicerata Mites and Ticks: small and often parasitic Specialized chelicerae for piercing tissue

and sucking out blood Pedipalps are often equipped with claws for

holding on to host Parasitize plants and animals Can cause itching, painful rashes, and

transmit diseases such as Rocky Mtn. spotted fever and Lyme disease

Subphylum Chelicerata Scorpions: widespread in warm areas

including southern US Pedipalps enlarged into claws Long, segmented abdomen has a venomous

stinger that can kill or paralyze prey Chew up prey with chelicerae

Subphylum Uniramia Includes centipedes, millipedes, and insects Response to stimuli Compound eyes Chemical receptors for taste and smell on

mouthparts, antennae and legs Sensory hairs to detect movement Well-developed ears that hear above human

range; found in strange places (behind legs in grasshoppers)

Subphylum Uniramia Adaptations for feeding 3 pairs of appendages for mouthparts

including mandibles Saliva contains digestive enzymes Bee saliva help change nectar into honey Glands in bee’s abdomen secrete wax, used

to build beehives

Subphylum Uniramia Movement and Flight Legs used for jumping, walking, capturing

and holding prey Flying insects usually have two pairs of

wings made of chitin Flight has allowed for movement worldwide

and wide variety of habitats

Subphylum Uniramia Metamorphosis: process of changing shape

and form 2 types: incomplete and complete Incomplete metamorphosis: gradual change

with nymph immature forms Nymphs lack sexual organs and wings and

usually look similar to the adult form Complete metamorphosis: dramatic change

with larval stage and pupa

Insect Communication Use sound, visual, chemical, and other types

of signals Most communication is for mating Sound: crickets chirping by rubbing legs

together; cicadas buzz by vibrating special membranes on their abdomens

Visual cues: fireflies lighting up Chemical signals: pheromones used for alarm

or alerting other insects and for mating

Insect Societies Ants, bees, termites, and some of their

relatives form complex associations called societies

Societies work together for the benefit of the whole group

Can have more than 7 million individuals Castes: groups of individuals performing a

certain job or role in the society (queen, workers, drones, etc)

Classification for Subphylum Uniramia

Centipedes: Class Chilopoda Millipedes: Class Diplopoda Insects: Class Insecta

Order Orthoptera: Crickets, grasshoppers, locusts Order Isoptera: termites Order Hymenoptera: bees, wasps, and ants Order Lepidoptera: butterflies and moths Order Diptera: true flies Order Coleoptera: beetles Order Hemiptera: true bugs Order Anoplura: human louse (lice) Order Odonata: dragonflies Order Dictyoptera: cockroaches and mantids