Arthropods are the most successful animal phylum in terms of species diversity, distribution, and sheer numbers
body segmentation( modified metamerism)
often fuse into three tagmata (anatomical areas) in the adult stage
head- contains segments with feeding and sensory activities
abdomen- contains segments with locomotor and or reproductive activities
head and thoracic segments fused
the body of an arthropod is completely covered by the
an exoskeleton of arthropod is made out of
protein and chitin
strong, protects the animal and provides points of attachment for the muscles that move appendages.
thick and inflexible in some regions, such as crab claws, and think and flexible in others, such as joints
in order to grow, an arthropod must molt its old exoskeleton and secrete a larger one
leaves the animal temporarily vulnerable to predators and other dangers
its relative impermeability to water helps prevent desiccation and provides support on land
arthropods moved to land after the colonization of land by plants and fungi
terrestrial arthropods generally have internal surfaces specialized for gas exchange. For example, insects have tracheal systems, branched air ducts leading into the interior from pores in the cuticle.
Limulus- horseshoe crab
Argiope- garden spider
Limulus- horseshoe crab
Argiope- garden spider
both contain one pair of_______ and one pair of ______.
________ and ________ are absent
Both contain one pair of chelicerae, one pair of pedipalps. Antennae and mandibles are ABSENT.
contain two pairs of ______, 1 pair of ________
primarily found in aquatic environments.
contain two pairs of antennae, one pair of mandibles
contain one pair______ and one pair_______
they are found in terrestrial environments.
contain one pair of antennae and one pair of mandibles
gills used for what?
feathery gills like under the lateral extensions of a large, expanded exoskeletal plate called the carapace
expanded exoskeletal plate
small angular structure located just under the carpace near the posterior portion of the thorax
Internal anatomy of crayfish
large digestive glands fill much of the body cavity. the intestine extends from the stomach through the tain to the anus. the green glands lie near the brain in the head.
thin threads leading out from the heart
When blood collects in sinuses around the heart, the heart relaxes and these holes open to allow the heart to fill blood. the holes then close and the blood is pumped through the arteries which distribute it around the body. blood seeps back to the heat, since no veins are present
open circulatory system
long tubular structures that resemble nephridia but are compacted into a glandular mass.
Waste and excess water pass from these glads to the outside of the body through pores at the base of the antennae on the head.
lies in the midline with nerves extending posteriorly fusing to form central nerve chord
How does the pattern of segmentation differ in the crayfish and the earthworm
crayfish has 3 distinct parts while the earthworm has septa that divides the body cavity
condition in which body parts are repeated serially along the longitudinal axis of the body.
analids and arthropods
since all of the appendages of an animal such as the crayfish are believed to have evolved from the same basic ancestral structure they are said to be _____
because each appendage is homologous to the others on the animal, they demonstrate
1 pair on abdomen
biramous appendages that together with the medial telson make up the tail fan which is used in rapid escape movements and in fanning the eggs and young
5 pairs on abdomen
biramous, used for swimming
anterior two pairs are modified as copulatory organs in the male
their grooves direct sperm into the female's seminal receptacle. In the female, the swimmerets are also used t hold the fertilized eggs for incubation
5 pairs on throax
uniramous; all but the last also bear gills
the first pair are the chelipeds and bear the large pincers (chelae)
the second and third pair also possess small pincers at their tips
3 on thorax
biramous; used in food handling and chemosensation. The last two pairs have gills attached
2 pairs on head
biramous; used for food handling
second pair bears gill bailers which generate respiratory water currents through the gill chambers
1 pair on head
shred food for swallowing
nephridiopore drains the green gland
1 pair on head
most marine, some freshwater, few terrestrial
free living even though some are parasitic
bodies of crustacean consist of two tagmata
covered by a caprice and contains appendages used in sensing moving and feeding
contains two pairs of antennae, one pair of mandibles, 5 pairs of walking legs
contains appendages used in moving
all crustaceans have two pairs of ______, 2 pairs of _____, a pair of ______, and a pair of ______ ____ commonly found on stalks
2 pairs of antennae, 2 pairs of maxillae, a pair of mandibles, pair of compound eyes
one of the constituents of crustacean mouth parts
lie just behind the jaws and aid with detection and manipulation of food
arthropods evolved from an annelid-like ancestor containing identical appendages
during this evolutionary process some metameres and appendages became specialized to accomplish different roles
the appendages are thus said to have serial homology. they are homologous since they are evolved from the same ancestral structures and serial since they are metameric
only winged invertebrates
most successful species are small in size and have a great reproductive capacity
what sets insects apart from crustaceans
insects have one pair of antennae and crustaceans have 2 pairs
Insect body plan
have one pair of antennae and one pair of mandibles
usually has three pairs of walking legs and one or two pairs of wings
most internal organs and specialized structure for reproduction
3 part gut
insects have what kind of appendages
Insect bodies divided into three_____
head: containing appendages used in sensing and feeding
thorax: containing appendages used in moving
abdomen: containing no appendages and having visceral functions
Respiration in insects
uses a system of internal tubes- tracheae and sacs delivering oxygen directly to cells. Air is taken in through openings called spiracles (small openings in elastic air tubes)
narrow esophagus leading from the mouth expands into a large crop used for food storage
crop empties into
stomach where digestion takes place
six pairs of these fingerlike extensions that connect to the digestive tract where the crop and the stomach meet.
these pouches secrete digestive enzymes and aid in food absorption.
food passes from the stomach to the
intestine then into the rectum and out the anus
space between the body walk and the digestive tract
excretion in insects
accomplished via Malpighian tubules
blind ending tube like appendages of the intestine that open at the border between the mid and hindgut
as the hemolymph circulates in the hemocoel near these malpighian tubules, the uric acid is actively transported and discharged into the hindgut, from where the excretory products are passed with the feces
named for clawlike feeding appendages called chelicerae which serve as pinchers or fangs. In their cephalothorax they contain one pair of chelicerae. this is followed by one pair of pedipalps and 4 pairs of walking legs.
lack antennae and mandibles
limulus- horseshoe crab
argiope- garden spider
Bodies of chelicerata are divided into two magmata
cephalothorax- locomotor, sensory, feeding appendages
abdomen- visceral functions
do not have hemoglobin but rather hemocyanin to carry oxygen in their blood
horseshoe crab blood contains
amebocytes which can be harvested for medical applications
Horseshoe crab exoskeleton
tough and leathery
must be molted periodically as the animal grows
divided into two regions: cephalathorax, abdomen
bears six pairs of spines along the sides and on its ventral side has six pairs of flat, plate-like appendages.
covering the cephalothorax dorsally and laterally
concave below and convex above
used for food manipulation
1st pair of appendages
second pair of appendages
walking legs, chelae
next 4 pairs
all appendages except the chelicerae have spiny masticatory processes called this on the basal segments.
the chelae of the appendages pick up food and pass it to the gnathobases.
between the last pair of walking legs is a small rudimentary pair of appendages called the chilaria.
houses openings of the genital pores
2 on the underside of operculum
tail used for bracing when the animal is burrowing or plowing through the sand or in righting itself when turned over
anus located ventrally at the proximal end
book gills, lamellae
leaf like folds
in life the plates and lamellae fan back and forth like the pages of a book in a breeze. because of this characteristic the collective structures are called book gills.
simple and compound eyes
later cpd eyes
median simple eyes
poison from glands on the chelicerae to immobilize their prey which chewing their prey, spill digestive juices into the tissues and suck up the liquid meal
Arachnid cephalothorax has
6 pairs of appendages
-4 pairs of walking legs
-pair of pedipalps function in sensing or feeding
chelicerae usually function in feeding
how is gas exchange carried out in spiders
produced as a liquid by abdominal glands and spun by spinnerets into fibers that solidify
hard, thin, chitinous, somewhat flexible
cephalothorax and abdomen which includes the pedicel (slender waist)
spiders do not have compound eyes
they have 6 to 8 ocelli (simple eyes) which can't detect motion so they rely more on tactile cues
all parts of body have
used to eject poison from its poison gland
6 joined and sed for gripping prey
in the male it is modified as an intermittent organ to transfer sperm to the female
basal parts are used to squeeze and chew food
each leg is made up of seven segments as follows : coxa, trochanter, femur, patella, tibia, metatarsus, tarsus
tarsus has claws and a tuft of sensory hairs at its terminal end
occurs between the blood circulating inside the lamellae and the air flowing in the spaces between the lamellae
opening into a small chamber from which tracheal tubes extend into the body
a chitinous plate which is located on the ventral mid line between the spiracle, conceals the female genital pore
3 pairs of spinnerets on a raised surface
held apart by bars so that there are always air spaces between them
passage through 3 different stages
larva hatches out of the egg
feeds and grows undergoing several molts
after the larva reaches maximum size, it molts and immediately undergoes a transformation into a non feeding stationary pupa.
pupal case splits open and the adult emerges
radical reorganization occurs. most of the larval tissues are broken down completely and replaced by adult structures concurrently formed from the division and differentiation of strategically situated clusters of embryonic cells called imaginal discs.
clusters were formed in the embryo but remain undifferentiated during the larval stage
the immature form that somewhat resembles the adult transforms stepwise with each molt to reach the adult form.
adult never molts
resembles the adult but its head is disproportionately large and its wings are rudimentary.
as it feeds and grows it molts and with each molt it more closely approximates the adult form. finally after the last molt it is an adult with fully functional wings and a reproductive system.
in aquatic species the naiad, as the immature stage is called, looks less like the adult and usually has modifications like gills for aquatic life. Otherwise its development proceeds as for terrestrial species.
ex:odonata (dragonflies) and Ephemeroptera (mayflies)
all insects have a exoskel composed of chitin and proteins which have been made tough and rigid through a chemical process called sclerotization.