Chapter 28: Arthropods & Echinoderms
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Echinoderms
28–1 Introduction to the Arthropods
A. What Is an Arthropod?
B. Form and Function in Arthropods
1. Feeding
2. Respiration
3. Circulation
4. Excretion
5. Response
6. Movement
7. Reproduction
C. Growth and Development in Arthropods
Phylum Arthropoda
“joint foot”
What Is an Arthropod?
• Arthropods have a bilateral
symmetry, a segmented body,
a tough exoskeleton (made of
chitin), and jointed
appendages.
• Arthropods are the largest
phylum of animals with more
than 750,000 species.
• Living arthropods generally
have fewer body segments
and more specialized
appendages than ancient
arthropods (600 mya).
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Crustacean
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Trilobite
Evolution of Arthropods
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The Anatomy of a Grasshopper
Antennae
Compound eye
Brain Digestive
Malpighian
tract
tubules
Ventral View
Legs
Heart
Reproductive
organs
Mouth
Salivary
glands
Anus
Ganglia
Tracheal tubes Nerve
cord
Spiracles
Tracheal
tubes
Spiracle
s
Arthropods
feed
on
respire
using
All types
of foods
Tracheal
tubes
reproduce
using
Internal
fertilization
Book lungs
have
well-developed
External
fertilization
Book gills
Heart
Brain
Muscles
Form and Function in Arthropods
Body Plan
Exoskeleton, jointed appendages, specialized appendages for feeding, bilateral
symmetry, cephalization.
Feeding
Herbivores, carnivores, omnivores, blood suckers, filter feeders, detritivores, and
parasites. Highly adapted mouthparts for eating (sponging, piercing, grasping,
grinding, lapping, chewing).
Respiration
Terrestrial Arthropods: Tracheal tubes extend throughout the body. Air enters
and leaves through spiracles (small openings). Spiders use book lungs (layers of
respiratory tissue stacked the pages of a book. Horseshoe crabs use book gills.
Aquatic Arthropods: Featherlike gills exchange oxygen & carbon dioxide.
Circulation
Open circulatory system. A well developed heart pumps blood through arteries and
then enters tissues. The blood is collected in a large sinus near the heart.
Excretion
Malpighian tubules (saclike organs) extract nitrogenous wastes from the blood
and add them to the feces, or digestive wastes that move through the gut.
Response
Well developed nervous system. All arthropods have a brain. Most haave sense
organs, such as eyes and taste receptors.
Movement
Muscle cells contract when stimulated by nerves. Muscles pull on exoskeleton to
allow for flying, walking, or swimming.
Reproduction
Terrestrial: Reproduce sexually through internal fertilization (sperm deposited
inside female body).
Aquatic: Reproduce sexaully by internal or external fertilization.
Growth and Development in Arthropods
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When they outgrow their exoskeletons, arthropods
undergo periods of molting (shed their entire
exoskeleton, and grow a new one.)
17 yr. Cicada video http://www.bio.indiana.edu/~hangarterlab/broodx/broodxmovies/NSFmovie.htm
28–2 Groups of Arthropods
A. Crustaceans
(Subphylum Crustacea)
B. Spiders & Their Relatives
(Subphylum Chilicerata)
1.
2.
3.
4.
Horseshoe Crabs
Spiders
Mites and Ticks
Scorpions
C. Insects & Their Relatives
(Subphylum Uniramia)
1. Centipedes
2. Millipedes
3. Insects
Groups of Arthropods
Subphylum Crustacea
Subphylum Chelicerata
Subphylum Uniramia
crabs, lobsters, shrimp,
crayfish, barnacles
horseshoe crabs, spiders,
mites & ticks, scorpions
Centipedes, millipedes,
insects
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•Crustaceans have two
pairs of antennae, two or
three body sections,
chewing mouthparts
called mandibles.
•Most are aquatic.
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•Chelicerates have
mouthparts called
chelicerae and two body
sections, and nearly all
have four pairs of
walking legs.
•No antennae.
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•Uniraminans have jaws,
one pair of antennae,
and unbranched
appendages.
•Largest group of
animals.
The Anatomy of a Crayfish (subphylum Crustacea)
Tail
Abdomen
Cephalothorax
Swimmerets
Carapace
First antenna
Mandible
Walking legs
Cheliped
Second antenna
The Anatomy of a Spider (subphylum Chelicerata)
Cephalothorax
Brain
Abdomen
Pumping
stomach
Heart
Intestine
Ovary
Malpighian
tubules
Eyes
Poison
gland
Pedipalp
Fanglike
chelicera
Anus
Spiracle
Bases of
walking legs
Airflow
Book Lung
Spinnerets
Silk glands
The Anatomy of a Grasshopper (subphylum Uniramia)
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28–3 Insects
A. What Is an Insect?
1. Responses to Stimuli
2. Adaptations for Feeding
3. Movement and Flight
4. Metamorphosis
B. Insects and Humans
C. Insect Communication
D. Insect Societies
1. Castes
2. Communication in Societies
Class Insecta
What Is an Insect?
• Insects have a body
divided into three parts
- head, throax, and
abdomen. Three pairs
of legs are attached to
the thorax.
• There are more insects
than any other animal
on earth.
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Section 28-3
Insect Diversity
Nonarthropod
invertebrates
(11%)
Noninsect
arthropods
(12%)
Vertebrates (4%)
Insects
(73%)
Response to Stimuli
• Compound eyes detect
changes in color and
movement.
• Chemical receptors for
taste and smell on their
mouthparts.
• Sensory hairs detect slight
movements in air or water.
• Well-developed ears hear
sounds far beyond human
range.
Adaptations for Feeding
• Three pairs of
appendages are used
as mouthparts,
including a pair of
mandibles.
• Variety of mouthparts
including; grinding,
tubelike, spongelike,
piercing, etc.
Movement and Flight
• Three pairs of legs
used for walking,
jumping, or capturing
and holding prey.
• Flying insects
typically have two
pairs of wings made
of chitin.
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Metamorphosis
Adult
Eggs
Adult
Eggs
Incomplete
Metamorphosis
Complete
Metamorphosis
Larva
Adult
Nymph
Nymph
Immature
Nymph
Adult
Larva
Pupa
Insects and Humans
Beneficial
•Bees, butterflies, and other insects
pollinate crops.
•Bees produce wax and honey.
•Some insects are eaten as
delicacies in Africa and Asia.
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Harmful
•Termites destroy wood structures.
•Wasps produce painful stings.
•Mosquitoes are a nuisance and can
spread disease like malaria and west
nile virus.
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Insect Communication
• Insects communicate
using sound, visual,
chemical (with
pheromones), and
dances.
• Much of their
communication
involves finding a
mate. Ex. Fireflies
light up to signal for a
mate.
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Insect Societies
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Queen
Winged
male
Major
worker
Minor
worker
• Ants, bees, termites, and some of their relatives
form complex associations called societies. Each
caste has a body form specialized for its role.
Reproductive castes are females called queens.
Reproductive males are called workers.
Communication in Societies
• Honey bees convey
information about the type,
quality, direction, and distance
of food by “dancing.”
• The round dance tells the
other bees that food is nearby.
• The waggle dance tells the
other bees that food is a
longer distance away. The
direction of the waggle
indicates the direction of the
food.
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Bee Dance Video: http://www.pbs.org/wgbh/nova/bees/dances.html
28–4
Echinoderms
A. What Is an Echinoderm?
B. Form and Function in Echinoderms
1. Feeding
2. Respiration and Circulation
3. Excretion
4. Response
5. Movement
6. Reproduction
C. Groups of Echinoderms
1. Sea Urchins and Sand Dollars
2. Brittle Stars
3. Sea Cucumbers
4. Sea Stars
5. Sea Lilies and Feather Stars
D. Ecology of Echinoderms
Phylum Echinodermata
“spiny skin”
What Is an Echinoderm?
• Echinoderms are
characterized by spiny
skin, an internal skeleton
(endoskeleton), a water
vascular system, and
suction-cuplike structures
called tube feet. Most
adult echinoderms have
five-part radial symmetry.
Sea star
Sea
cucumber
Sea urchin
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The Anatomy of a Sea Star
Echinoderm Active Art http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=cbe&wcsuffix=8284
Eyespot
Endoskeletal plates
Anus
Stomach
Digestive glands
Ring canal
Radial canal
Madreporite
Reproductive glands
Tube foot
Sucker
Form and Function in Echinoderms
Body Plan
Five-part radial symmetry, spiny skin, internal skeleton, water vascular
system, deuterostome (blastopore develops into an anus).
Feeding
Sea star pushes stomach into prey’s shell, digests prey in its shell, retracts
stomach.Sea urchin uses five-part jaw to scrape algae and eat kelp. Sea
cucumbers filter detritus in sand like a bulldozer. Sea lilies use tube feet to
catch plankton.
Respiration
Water vascular system carries oxygen through body. In most species, thin
walls of tube feet provide a surface for respiration. Some species use skin
gills.
Circulation
Water vascular system carries nutrients throughout the body.
Excretion
Digestive wastes are released as feces through the anus. Nitrogen waste is
passed into the water through tube feet and skin gills.
Response
Nerve ring surrounds the mouth and radial nerves connect the ring with body
sections. Most have sensory cells to detect light, gravity, and prey chemicals.
Movement
Tube feet fill with water from the water vascular system. Muscles move
plates of the endoskeleton.
Reproduction
Most Reproduce Sexually by external fertilization (sperm and eggs are
released into open water, where fertilization takes place. Larvae have bilateral
symmetry, adults have radial symmetry.
Groups of Echinoderms
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Sea urchins & sand dollars
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Sea cucumbers
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Sea stars
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Brittle stars
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Sea lilies
Groups of Echinoderms
Comparing Groups and Major Characteristics of Echinoderms
Characteristic
Sea urchins
and sand
dollars
Brittle
stars
Sea
cucumbers
Sea
stars
Sea lilies and
feather stars
Feeding
Detritivores
Detritivores
Detritivores
Most carnivores
Herbivores
Shape
Movement
Disc- or globeshaped, no arms
Star-shaped,
arms
Burrow in sandy
ocean bottom or Move rapidly
wedge in rock
along ocean
crevices using
floor using arms
moveable spines
attached to
endoskeleton
Cucumbershaped, no
arms
Move slowly
along ocean
floor using
muscular body
wall to crawl
Star-shaped,
arms
Creep slowly
along ocean
floor using arms
Stalk with
feathery arms
Cannot move;
attached to
ocean bottom
Ecology of Echinoderms
• Echinoderms control the distribution of
algae and other forms of marine life.
• Crown-of-thorns sea star feeds on coral and
is a serious threat to coral reefs around the
world.
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