Transcript Arthropods & Echinoderms

Arthropods
&
Echinoderms
Phylum Arthropoda
Well-Known Subdivisions of Phylum
Arthropoda
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Class Arachnida
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Order Scorpiones (scorpions)
Order Opiliones (daddy-longlegs)
Order Acari (mites & ticks)
Order Araneae (spiders)
Class Chilopoda (centipedes)
Class Diplopoda (millipedes)
Class Insecta (insects)
Evolution
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Precambrian seas over 600 million years ago
well established by 500 million years ago
Constantly evolving
very diverse phylum
Symmetry
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Bilaterally symmetrical
Advantages:
 Specialization of body organs
 Cephalization
 Efficient movement
 Defined
direction of movement
 Less resistance to water and substances
 Finding food, mating, avoiding predators
Body Cavity
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Coelomate
mesoderm lines body cavity and surrounds and
supports the endodermic gut
 mesoderm forms tissues of attachment for organs
located in coelom (liver, lungs, etc.)
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Structural Support
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Exoskeleton
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3 Layers:
Waxy outer layer made up of proteins and lipids; repels
water; helps prevent drying out
 Middle layer provides primary protection; made of protein
and chitin; sometimes calcium carbonate
 Inner layer contains protein and chitin; flexible at jointsallows arthropod to move freely;
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Muscles attached to inner layer at joints move body
segments
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Parts of a Crayfish
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Sensory- antennules,
antennae
Defense- chelipeds
Feeding- mandible, mouth,
maxillipeds, maxilla
Walking- walking legs
Swimming- swimmerets,
uropods
Appendage
Antennule
Antenna
Mandible
Maxilla
Function
Touch, taste, equilibriium
Touch, taste
Chew food
Manipulate food, draw water
currents over gills
Maxilliped
Touch, taste, manipulate food
Cheliped
Walking leg
Capture food, defense
Swimmeret
Create water currents,
transfer sperm (males), carry
eggs and young (females)
Uropod
Propulsion during tailflips
Locomotion over solid
surfaces
Nutrition & Digestion
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Crayfish (crustacean):
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DIET: omnivores; they eat plants, animals, and decaying organisms
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Ex: shrimp, fish, water plants, plankton, insects
food passes through esophagus to stomach
teeth made of chitin and calcium carbonate grind food into fine paste
enzymes secreted by digestive gland mix paste
Paste enters intestine and digestive gland for further digestion and
absorption
indigestible material leaves through anus
Nutrition and Digestion (cont.)
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Scorpions:
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Spiders:
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DIET: mainly insects and spiders
DIET: mainly insects; some can eat fish, frogs, or birds; consume body fluids of
prey
Similar digestive system to crustaceans (like crayfish)
Parasitic mites: suck fluids from leaves of fruit trees; feed on blood, dead
skin, hair, and feathers of vertebrates, like humans, cattle, and dogs
Parasitic ticks: feed on blood of host
Millipedes: use mandibles and maxillae to chew on plants and decaying plant
matter
Centipedes: use poisonous claws to kill prey (earthworms, insects, etc.) and
use mandibles and maxillae to tear apart food
Transportation
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Some are sessile as adults
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Ex: Barnacles
Isopods: “equal legs”
Have 7 pairs of identical legs
 Ex: sow bugs, pill bugs
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Decapods: “ten feet”
5 pairs of legs
 Ex: crayfish, lobsters, shrimps, crabs
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Transportation (cont.)
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Tailflip: muscles of a crustacean (such as a crayfish) can bend
the abdomen and propel it backwards very rapidly
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Uropods on the abdomen of a crayfish help propel crayfish during
tailflips
Arachnids: have 4 pairs of walking legs
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Ex: spiders, scorpions, mites, ticks
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Mites and ticks can also be parasitic
Myriapods:
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Millipedes have 2 pairs of legs on each body segment except the last two;
move slowly
Centipedes have anywhere from 15 to 175 pairs of legs; can move
quickly
Circulation
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All have open circulatory systems
Crustaeans:
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Dorsal heart pumps hemolymph into blood vessels
Vessels carry it to different parts of body
Hemolymph leaves vessels, enters hemocoel and surrounds tissues
Passes through the gills, where it exchanges CO2 and O2 with H20
Hemolymph returns from gills to dorsal heart
Spider’s and scorpion’s circulatory systems are similar to
crustaceans
Respiration/Gas Exchange
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Crustaceans:
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All except smallest crustaceans use gills
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Gills extend from base of each walking leg into a chamber
under carapace
Legs circulate water across gills as the crustacean walks
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Small crustaceans- CO2 and O2 diffuse through thin parts of the
exoskeleton
Feathery branches on maxillae also help direct water over gills
A thin extension of the exoskeleton covers each gill and
permits gases to diffuse across gill surface
Respiration/Gas Exchange (cont.)
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Spiders:
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Book lungs- paired sacs in abdomen with several
parallel folds
Like pages in a book
 Allow for large surface area for efficient gas exchange
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Tracheae- tubes that carry air from openings in the
exoskeleton to tissues in the body
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Openings- spiracles
Some spiders have either book lungs or tracheae, and
some have both
Water Balance/Excretion
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Crayfish:
Hypertonic to environment
 Excess water eliminated by green glands- excretory
organs
 Water and other fluids leave crayfish through a pore at the
base of the antennae
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Spiders:
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Malphighian tubules- hollow projections of the
digestive tract that carry body fluids and wastes to the
intestine
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Help spiders conserve water
Some spiders have coxal glands
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Remove wastes through openings at the base of the spider’s legs
Reproduction/Development
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Crustaceans:
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Mate in fall
Male transfers sperm to female using first and second swimmerets
Sperm fertilize eggs and are released in spring; eggs stay on the female’s
swimmerets
Eggs hatch after 6 weeks
Have several larval stages
 Naupilus- free-swimming larva; has one eye and three pairs of
appendages
Emerge from larval stages as a smaller version of adult firm
Molt 7 times first year; molte 2 times in their remaining life
Reproduction/Development (cont.)
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Spiders:
Mature male transfers sperm to pedipalp sacs
 Male places sperm in female’s seminal receptacle
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Male must leave as soon as mating is finished- female might eat
him otherwise
Female fertilizes eggs and passes them into a cocoon
which she spins herself
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She will either carry the case around or attach it to a plant or web
Spiders undergo their first molt within two weeks of
entering the cocoon; they leave the cocoon after those
two weeks
 Can grow to as large as 9 cm long
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Unique Characteristics
& Interesting Facts
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Arthropods make up 75% of all animals!
Centipedes can have anywhere from 15 to 175 pairs of legs!
Arthropods go through a process called molting
 Their exoskeleton cannot grow, so they have to periodically shred it
in order to get larger
Copepods, crustaceans that are less than a centimeter long, are the most
abundant animals in the ocean. There are so many of them that they
outweigh all the whales on Earth!
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Unique Characteristics
& Interesting Facts
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Only arthropods have all five characteristics!
Subphylum Crustacea
Procambarus fallax
Pond crayfish
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Class Arachnida
Nephila clavipes
Golden Silk Banana Spider
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Pandinus imperator
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Black Emperor
Scorpion
Class Diplopoda
Deseret Millipede
Orthoporus ornatus
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Class Chilopoda
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Desert Millipede
Scolopendra
Subphylum
Insecta
Symmetry/Body Cavity/
Structural Support
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All insects have bilateral symmetry
Insects are coelomate arthopods
hard exoskeleton of insects allows for structural
support of muscles
thorax provides structural support for the legs
and, if present, wings.
Nutrition/Digestion
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Insects obtain nutrients from the food they eat
three regions in the digestive system
foregut (stomodeum)
 midgut (mesenteron)
 hindgut (proctodeum)
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All insects have a complete digestive system
food processing occurs within the alimentary
canal, a tube-like enclosure, which runs lengthwise
through the body
 Ingested food travels in only one direction
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Nutrition/Digestion (cont.)
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An Insect’s mouth is specialized
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Grasshopper’s mouths are used for cutting and
chewing leaves and blades of grass
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Labrum & Labium: mouth parts that function and
upper and lower lips
Mosquitoes have long, thin mouth parts used for
piercing flesh and sucking blood
 Flies have soft, sponge-like mouths used for soaking
up liquids, such as fruit juices
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Digestion/Excretion
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food enters the mouth and passes through the
esophagus to the crop
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Food then travels to the gizzard where it is shredded
Shredded food moves to the midgut where nutrients are
absorbed through the wall and into the coelom
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Moistened by saliva from salivary glands
Gastric ceca: pockets that branch from the digestive track
which secrete enzymes
Any undigested material travels to the hindgut and exits
the body through the anus
Stomodaeum
Mesenteron
Proctodeum
Circulation
All insects have an open circulatory system
 responsible for movement of nutrients, salts,
hormones, and metabolic wastes
 Large dorsal vessel (aorta) carries hemolymph
through the insect’s body
 The heart, located in the abdomen and
thorax, pumps hemolymph to the “head” of
the insect
 The hemolymph then moves back through
the coelom and reenters the heart through
small pores
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Transportation
Insects have three pairs of jointed legs
 Most have one or two pairs of wings
 Grasshopper:
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 Two
pairs of walking legs
 One pair of hind legs
 Used
 Two
for jumping
pairs of wings
Gas Exchange/Respiration
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insects are aerobic organisms
 respiratory system transports carbon
dioxide and oxygen
 separate from the circulatory system
 Insects use a tracheal system,
complex network of tubes that brings
oxygen-containing air all around the
body
Gas Exchange/Respiration (cont.)
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Air enters the body through spiracles, valve-like
openings in the exoskeleton located along the
thorax and abdomen of most insects
Air travels through the tracheae which have ends
filled with fluid
Oxygen diffuses through the fluid and into the
cells
Carbon dioxide diffuses the opposite way
Water Balance
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The exoskeleton contains a waxy covering which helps
to keep moisture in
Insects can lose water in 3 ways by evaporation
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general surface of the body wall
spiracular system
both
Some insects keep their spiracles closed to conserve
water only opening them to receive enough oxygen
Malphighian Tubes: collect water and cellular wastes
from the hemolymph as well as return water to the
hemolymph
Reproduction
All insects have separate sexes
 Male places sperm in female’s seminal
receptacle, and they are stored there until
eggs are released by the ovaries
 Eggs are fertilized internally
 In grasshoppers, the female has an
ovipositor on the last segment of her
abdomen
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Ovipositor: organ which the female grasshopper
uses to dig a hole in the ground to lay the
fertilized eggs
Development
After hatching, a young insect must molt
several times before becoming fully mature
 Most insects go through metamorphosis,
a developmental change in form
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 Two
main kinds: incomplete and
complete
Development (cont.)
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incomplete
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A nymph, an immature version of the adult, is hatched from
the egg, gradually develops into an adult
Grasshoppers, mayflies, dragonflies, and termites undergo
incomplete metamorphosis
Complete
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Worm-like larvae hatches from the egg
Exoskeleton falls off and larvae develops into a pupa, stage
of development where the larvae becomes an adult
After metamorphosis is complete, the pupa molts into a
mature adult
Butterflies, moths, and bees undergo complete
metamorphosis
Unique Characteristics
& Interesting Facts
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95% of all the animal species on the earth are
insects
one out of every four animals on earth is a beetle
Scientists estimate that 10% of the animal
biomass of the world is ants, and another 10% is
termites
About 1,000,000,000,000,000,000 (a billion
billion) insects are alive at any time. This is about
160 million insects for each person on Earth!
Monarch Butterfly
Order:
Lepidoptera
Scientific Name:
Danaus plexippus
Honey Bee
Order:
Hymenoptera
Scientific
Name:
Apis mellifera
Common House Mosquito
Order: diptera
Scientific Name:
Culex pipiens pallens