UNIT 11
INVERTEBRATES
READING:
Chapter 27
Chapter 28
Chapter 29
Chapter 30
Chapter 31
Introduction of Animals
Simple Invertebrate
Mollusks and Annelids
Arthropods
Echinoderms and Invertebrate Chordates
OBJECTIVES:
At the end of this unit of study the student will be able to:
1.
List characteristics of the Kingdom Animalia and distinguish between invertebrates and
vertebrates.
2.
Define symmetry; list the four types of symmetry and give examples of each.
3.
Summarize embryonic development; list and define the three germ layers.
4.
Name and describe the four body types or plans.
5.
List characteristics of the Phylum Porifera.
6.
Describe the basic body plan and biological processes of a sponge.
7.
Define the basis of sponge classification; list and describe the four classes.
8.
List the three common characteristics of all cnidarians.
9.
Identify the three cnidarian classes and give examples of each.
10.
State the distinguishing characteristics of flatworms.
11.
Name and describe the classes of flatworms.
12.
List the characteristics of nematodes and identify some representative organisms.
13.
List the distinguishing characteristics of the Phylum Annelida.
14.
Name and distinguish between the classes of annelids.
15.
List evidence that indicates a close evolutionary relationship between mollusks and annelids.
16.
Name the characteristics of the mollusks.
17.
Name and describe the four major classes of mollusks and give an example of each.
18.
List the three distinguishing characteristics of arthropods.
19.
Name the four subphyla of Arthropods and list the characteristics of each.
20.
Name and describe the major classes of Arthropods - Crustacea, Archnida, and Insecta.
21.
Distinguish between complete and incomplete metamorphosis.
22.
Describe Insect defense mechanisms.
23.
Describe social behavior of insects.
24.
List the characteristics of the Phylum Echinodermata.
25.
Name, describe, and give representatives of the five classes of Echinoderms.
ASSIGNMENTS:
1.
7.
2.
8.
3.
9.
4.
10.
5.
11.
6.
12.
INVERTEBRATES
I.
UNIT 11
Kingdom Animalia
A. Characteristics
1. Eukaryotic
2. Multicellular
a. METAZOAN - multicellular animals.
b. Structural characteristics of invertebrates suggest evolution from protozoans
1) Single celled organisms' growth limited by volume to surface area ratio.
2) Can't get food and oxygen fast enough.
c. Specialization - adaptation of cell for specific function - advantage of multicellular life
1) Enables adaptation to many environments.
2) Specialized cells lose ability to survive on their own - disadvantage
3. Heterotrophic - nutrients obtained by ingesting food.
4. Terrestrial and aquatic species - some adapted to both
5. Reproduction usually sexual but lower species may reproduce asexually.
6. Largest kingdom in terms of number of species.
B. Classification
1. Separated into two broad informal categories
a. INVERTEBRATES - animals without backbones - composed of about 97% of all animal species.
1) Don't share a common characteristic - share common lack of a characteristic.
2) Diverse group - over a million species
b. Vertebrates - animals with a backbone.
2. Separated into 16 phyla - Ones we will study marked with a *
a. Porifera *
i. Bryozoa
b. Cnidaria (Coelenterata) *
j. Brachiopoda
c. Ctenophora
k. Mollusca *
d. Platyhelminthes *
l. Annelida *
e. Rotifera
m. Arthropoda *
f. Nematoda *
n. Echinodermata *
g. Nematamorpha
o. Hemichordata
h. Acanthocephala
p. Chordata * our phylum
C. Patterns of Symmetry
1. SYMMETRY - arrangement of body parts around a point or central axis.
2. Types of symmetry
a. ASYMMETRICAL - no definite shape or symmetry - ameba, sponge.
b. SPHERICAL - shaped like globe or sphere - may be divided many ways
1) Earliest ancestors of multicellular animals may have been hollow ball of cells
2) example - volvox (Protist)
c. RADIAL - divided into similar halves by any plane that passes through its longitudinal axis.
1) LONGITUDINAL AXIS - axis formed by drawing imaginary line from end to end through
center of organism.
2) Observed in jellyfish, hydra
d. BILATERAL - divided into similar halves by only one specific plane passing through
longitudinal axis - right mirrors left.
1) Observed in insects, worms, humans
2) Have specialized front and rear ends
a) ANTERIOR - front end
b) POSTERIOR - hind end
3) Definite upper and lower surface.
a) DORSAL - top surface
b) VENTRAL - bottom/belly surface
4) Most exhibit CEPHALIZATION - nerve tissue/sensory organs concentrated in anterior end.
a) Sense organs enters new environment first - provides information.
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D. Patterns of Development
1. Body plan and specialized structures of animals arise early in development.
a. Development begins with fertilized egg or ZYGOTE.
b. Zygote divides and forms EMBRYO - name given organism in earliest stages of development.
c. Cell divisions produce a hollow ball of cells called BLASTULA
d. Cells on blastula move inward forming slight depression called a BLASTOPORE.
e. Further infolding forms cup shaped embryo called a GASTRULA.
2. During GASTRULATION either 2 or 3 germ layers form
a. GERM LAYER - layer of cells in developing embryo that give rise to specific structures.
b. Types of germ layers
1) ECTODERM - cells on outside gastrula - will form covering of animal – “outer skin”.
2) ENDODERM - cells inside the gastrula - will form gut lining – “inner skin”.
3) MESODERM - third cell layer formed between endoderm and ectoderm - will become
muscle and other interior body linings – “middle skin”.
II. Body Plans/Types
A. Scientists identify 4 types of body plans in animals.
B. Body plans determined by the relationship between the germ layers.
C. Body types defined by presence or absence of COELOM - body cavity
1. Important evolutionarily.
2. Permits gut to move independently of body.
3. Animal doesn't have to move whole body to move food.
D. Body Types - from least complex to most complex.
1. Acoelomate with 2 germ layers
a. ACOELOMATE - "without a coelom"
b. Least complex
c. 2 germ layers - endoderm and ectoderm
d. Germ layers not separated by cavity
e. Found in sponges and cnidarians.
2. Acoelomate with 3 germ layers
a. 3 germ layers not separated by cavity - ectoderm, mesoderm, and endoderm.
b. Found in flatworms.
3. Pseudocoelomate
a. PSEUDOCOELOMATE - "False coelom” - Cavity forms between mesoderm and endoderm
b. Ectoderm, mesoderm, and endoderm present
c. Found in roundworms and rotifers
4. COELOMATE
a. Characterized by a coelom within the mesoderm
b. Ectoderm, mesoderm, and endoderm present.
c. Most complex
d. Found in mollusks, annelids, arthropods, echinoderms and all chordates including human
III. Phylum Porifera - Sponges
A. Phylum name is Latin for "porebearer"
B. Characteristics
1. Has many small pores
2. Most are marine; there are some freshwater species
3. May be almost any color - white, gray, red, yellow, purple, black
4. Size varies - 1 cm to 2 m.
5. Forms crustlike layer on rocks - resemble plants
a. SESSILE - attach themselves firmly to surface and don't move.
6. No true tissues or organs
C. Body Structure
1. Hollow body
a. Body wall composed of 2 layers of cells
b. Cell layers separated by layer of jellylike substance.
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c. Inner layer of cells has COLLAR CELLS - have flagella in center.
d. Water enters sponge body through INCURRENT PORE.
e. Water exits sponge body through EXCURRENT PORE or OSCULUM.
f. Movement of water aids in gathering food and oxygen, and excreting wastes.
2. Sponges able to maintain shape by simple skeleton
a. Network of protein fibers called SPONGIN.
b. Some skeletons have tiny, hard particles - shaped like spiked stars called SPICULES.
1) Composed of silica dioxide or calcium carbonate.
2) Type of skeleton is basis for classifying sponges into classes.
D. Feeding
1. Because they are sessile they can't pursue food.
2. Collar cells which pump water through body also screen food out of water - FILTER FEEDING.
3. Collar cells engulf food and take it into cell to be digested.
4. Digested nutrients distributed by specialized cells called AMEBOCYTES in the jellylike layer.
a. Also carry carbon dioxide and other wastes away - released into water.
E. Reproduction
1. Asexual
a. Some freshwater sponges may form GEMMULES - protective ball of amebocytes, spicules, and
food
b. Can REGENERATE - ability to regrow missing parts; can grow new organism.
2. Sexual
a. Sperm shed into water; enters another sponge
b. Sperm taken in by collar cells and carried to egg by amebocytes
c. Fertilized egg develops into immature form called LARVA; has flagella to swim to new site.
d. Some species have separate sexes.
e. In most species each individual produces both egg and sperm - called HERMAPHRODITE
1) Self-fertilization rarely occurs - usually don't produce egg and sperm at same time
2) Common in sessile invertebrates.
F. Classification
1. Classes of sponges based on skeletal composition
2. Sponge Classes
a. Class Calcarea - spicules of calcium carbonate.
b. Class Hexactinella - spicules of silicon dioxide (silica)
c. Class Demospongiae - Spongin or combination of spongin and silica spicules
d. Class Sclerospongiae - Spongin with both silica and calcium carbonate spicules.
IV. Phylum Cnidaria or Coelenterata
A. Names
1. Cnidaria - for cnidocytes or stinging cells
2. Coelenterata - for coelenteron or "hollow gut"
B. Characteristics
1. Have stinging cells.
2. Have a coelenteron (hollow gut)
3. Have flexible tentacles.
C. Structure and Function of Coelenterate Body.
1. Body either vase-shaped or bell-shaped
a. Vase-shaped body called POLYP - specialized for sessile life.
b. Bell-shaped body called MEDUSA - specialized for swimming.
c. During life cycle some cnidarians go through both polyp and medusa stage.
2. 2 cell layers - ectoderm and endoderm separated by jellylike material called MESOGLEA.
3. Foodgetting
a. Tentacles capture prey and paralyze it with coiled stingers called NEMATOCYSTS - located in
the cnidocytes
b. Tentacles draw prey to mouth and into coelenteron - gastrovascular cavity - (hollow gut)
c. Enzymes released into coelenteron break up prey
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d. Specialized cells lining coelenteron absorb food.
e. Undigested food and wastes expelled through mouth.
D. Classification - 3 classes
1. Hydrozoa - includes polyps, medusae and species that alternate between the 2 - Hydra, Obelia,
Portuguese Man-of-War.
a. Portuguese Man-of-War - colony of modified polyps and medusae
1) Tentacles bear polyps - feeding, digestion, reproduction
2) Large Medusa - gas-filled float
3) Prey on fish; nematocyst poison may be fatal to humans.
2. Scyphozoa - Spend most of their life cycle as medusae - true jellyfish.
a. Means “cup animal”
b. Dominant form is medusa.
3. Anthozoa - Live only as polyp - anemones, corals.
a. Means “flower animal”
b. Corals
1) Thousands of small polyps living in colonies; secrete calcium based skeleton
2) Build rock like reefs; skeletons cemented together.
3) Corals live in warm, shallow, clear waters.
4) Types of Reefs
a) FRINGING REEF - close to the beach
b) BARRIER REEF - forms farther out from beach; Great Barrier Reef off Australian east
coast is world's largest.
c) ATOLL - circular reefs with open lagoons; form far out to sea
V. Phylum Platyhelminthes
A. Worm doesn't refer to specific taxon of animal
1. 3 groups generally called worms
a. Phylum Platyhelminthes - flatworms
b. Phylum Nematoda - roundworm
c. Phylum Annelida - segmented worms.
B. Characteristics
1. Bilaterally symmetrical
2. Lack respiratory and circulatory systems
3. Show cephalization - nerves and sense organs concentrated in anterior
C. Classification - separated into 3 classes
1. Class Turbellaria - free living
2. Class Trematoda - parasitic
3. Class Cestoda - parasitic
D. Parasitism
1. PARASITE - organism that lives on or in another organism.
2. HOST - organism on or in which parasite lives.
3. Parasite deprives host of nutrients; interferes with host's internal organ systems
4. Majority of parasites don't kill host - ensures host will not become extinct.
5. Parasites modified for parasitism
a. Some lack mouth or well developed digestive system
b. Have hooks or suckers to grip host.
c. May have protective outer covering - prevents digestion by the host.
1) TEGUMENT - thick covering of cells.
2) CUTICLE - nonliving layer secreted by epidermis.
VI. Phylum Nematoda
A. Commonly called roundworms
B. Characteristics
1. Have a pseudocoelom - body cavity lined on inside by endoderm and on outside by ectoderm.
a. Contains organs
b. Supports body.
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C.
VII.
A.
B.
C.
c. Provides hydrostatic pressure against which muscles can contract.
d. Serves as storage area
1) For waste
2) For eggs and sperm.
2. Long slender bodies - tapered at both ends
3. Most covered with flexible, protective cuticle
4. Digestive tract now 1 way - has 2 openings; Anterior opening - mouth; Posterior opening – ANUS – opening
through which waste eliminated.
5. Separate sexes
6. Vast majority are freeliving - habitats include land, marine, and freshwater.
7. Parasitic species cause economic damage and physical suffering.
Representative Species
1. Ascaris
a. Parasitic roundworm of intestinal tract - pigs, horses, humans
b. Female lays up to 200,000 eggs per day; fertilized eggs shed through genital pore; exits with
host's feces; eggs enter body in contaminated food or water; hatch in intestine; larvae bore into
bloodstream; carried to lungs and throat; coughed up, swallowed, and returned to intestine
where worms mature and mate.
c. Disorders
1) Can block intestines
2) Larva cause respiratory illness
2. Hookworm - Ancylostoma and Necator
3. Trichinella
a. Causes disease Trichinosis in humans.
b. Become infected by eating undercooked pork contaminated with trichina cysts.
c. Cysts release larvae; burrows into small intestine wall - mature into adults.
d. Adults mate; larvae pass to bloodstream; form cysts in muscle - cause pain/stiffness
e. Now rare in United States
1) Farmers cook meat scraps before feeding hogs.
2) Meat packers freeze pork - kills worms.
Phylum Annelida
Name annelid means "little rings"; refers to many segments that make up the body.
Characteristics
1. Have true coelom.
2. Body divided into many segments - phenomenon called METAMERISM.
a. Some segments fuse during development.
b. Other segments remain separate; called METAMERIC UNITS.
3. All organ systems well developed in most of the group.
4. Have external bristles called SETAE.
Classification
1. Classes based on number of setae and presence or absence of fleshy appendages called PARAPODIA
2. 3 Classes
a. Class Polychaeta
1) Have many parapodia.
2) Have numerous setae.
3) All members are marine.
b. Class Oligochaeta - earthworm
1) No parapodia
2) Few setae
c. Class Hirudinae - leeches - smallest class
1) No setae
2) Have suckers - used to effect crude walking motion
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3) Sucks blood from vertebrates
a) Salivary glands secrete substance that prevents blood from clotting.
b) Used medically to "bleed" patients both in the past and at the present.
VIII.Relationship Between Mollusks and Annelids
A. Comparative studies indicate members of Phylum Mollusca probably share a common ancestor with members of
Phylum Annelida (Segmented Worms)
B. Cleavage Patterns
1. CLEAVAGE - division of 1 cell into 2 cells.
2. Early cleavages form cells of equal size in most organisms.
3. In mollusks and annelids - get unequal cleavage - produces cells with different amounts of cytoplasm.
a. Leads to cell differentiation at very early stage.
b. Leads to early determination of cells - called DETERMINANT CLEAVAGE.
c. Continued division results in smaller cells
1) Small cells form 1 pole of developing organism.
2) Large cells form another pole
4. Cells twist to fill space caused by unequal division.
a. Creates spiral pattern.
b. Cleavage called SPIRAL CLEAVAGE.
C. Mesoderm Formation
1. Mesoderm develops from special cells that move to inside of gastrula -move between endoderm and
ectoderm.
2. Mesodermal cells form layer between ectoderm and endoderm.
3. True coelom develops from split in mesoderm layer.
a. Separation of gut muscles from muscles of body wall allows food to move through
body
independent of locomotion.
b. Coelom provides space in which circulatory system can function without interference of other
organ systems.
4. Primitive gut formed of endoderm cells; lined on outside by mesoderm.
5. Blastopore becomes mouth of animal; second opening in endoderm becomes the anus.
D. Trochophore Larvae
1. Strongest evidence of common ancestry
2. Pear-shaped larvae
a. Tufts of cilia at its ends.
b. Ciliated band around its middle.
3. First stage of larval development
4. Free-swimming in marine mollusks; remains within egg membrane of terrestrial mollusks and
marine annelids.
5. Differences between annelids and mollusks begin to show after trochophore stage.
IX. Phylum Mollusca - Mollusks
A. Diverse group
1. Only Phylum Arthropoda has more species.
2. Includes sedentary filter feeders and jet-propelled predators.
B. Importance
1. Can damage crops - snails and slugs
2. Serve as alternate hosts for some parasites - flukes
3. Serve as food - clams, oysters, mussels, squid, octopus
4. Shell can serve as jewelry - abalone.
C. Characteristics
1. Have true coelom.
2. Body has 3 distinct parts - muscular foot; head; and visceral mass.
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D.
E.
F.
G.
H.
3. Organ systems present
a. Circulatory
d. Excretory
b. Respiration
e. Nervous
c. Digestive
f. Reproductive
4. Most are bilaterally symmetrical
5. Most have one or more shells secreted by mantle.
Body Plan
1. All mollusks have 3 main body parts.
a. Muscular Foot - Large organ used for locomotion
b. Head - Contains mouth, sense organs, and cerebral ganglia (primitive brain)
c. Visceral Mass - contain heart and organs of digestion, excretion, and reproduction.
1) Surrounded by coelom
2) Covered by MANTLE - epidermal layer that secretes a shell
2. Shell (Valves)
a. Usually of calcium carbonate
b. Protects soft body from predators
c. Secreted by the mantle
d. Reduces surface area available for gas exchange.
1) Problem overcome by special organs of gas exchange - Gills
2) GILLS - specialized organs of gas exchange with water.
3) Gills hang in space between mantle and visceral mass
Classification
1. Classified into 4 to 7 classes using structural differences
2. 4 Major Classes
a. Class Polyplacophora
c. Class Bivalva
b. Class Gastropoda
d. Class Cephalopoda
Class Polyplacophora - Chitons
1. Name means "many plates"
2. Shells divided into 8 separate, overlapping plates.
3. Primarily animals of seashore that live on rocks.
Class Gastropoda
1. Name means "stomach foot"
2. Largest and most diverse group - snails, slugs, abalones, conches
3. Most have single shell or valve - slugs lack shell.
4. In terrestrial snails, mantle cavity acts as modified lung
a. Gases exchanged through thin membrane lining cavity.
b. Lining must be kept moist - snails usually active when air has high moisture - usually at night.
c. Inactive during dry periods - retreats into shell; opening sealed with mucus
5. Have OPEN CIRCULATORY SYSTEM - blood does not circulate entirely in vessels
a. Blood collected from lungs or gills
b. Pumped through heart
c. Released into space in the tissues; HEMOCOEL - blood cavity; blood filled cavity
d. Blood returns via gills or lungs to the heart.
6. Feeding
a. Snails and slugs eat garden plants
b. Scrape surface with tonguelike structure called RADULA - "scrapper"; has chitinous teeth.
Class Bivalva (Pelecypoda)
1. Includes clams, oysters, scallops, and mussels
2. Name means "2 valves" - shell has 2 valves.
a. Hinge connects 2 valves of shell.
b. Valve consists of 3 layers - secreted by mantle.
1) Outer layer - thin; protects against acidic water conditions
2) Middle layer - Calcium Carbonate Crystals - strengthens the shell
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3) Inner layer - Smooth, iridescent - protects animal’s soft body.
a) Irritant - sand in shell - mantle coats with secretion called MOTHER OF PEARL
b) Layers of secretion forms PEARL.
c. Animal closes valves with powerful adductor muscles - when muscles relax, valves open.
3. Movement - burying itself.
a. Muscular foot pushed into sand.
b. Blood swells end of foot, causing it to spread and forms hatchet-shaped anchor.
c. Foot muscle contracts - pulls animal down into sand.
4. Doesn't have distinct head region - ganglia in anterior region is considered the head.
5. Filter Feeders
6. Respiration - water over gills, oxygen diffuses to blood; carbon dioxide diffuses out.
7. Nervous System - well developed
8. Reproduction
a. EXTERNAL FERTILIZATION - outside body - egg and sperm shed to the water.
b. Fertilized egg becomes trochophore larvae - settles to bottom; becomes an adult.
c. A few species are hermaphroditic.
I. Class Cephalopoda
1. Name means "head-foot"
a. Large, well developed head
b. Foot divided into tentacles
2. Includes octopus, squid, cuttlefish, and chambered nautilus
3. Prey captured by tentacles with strong suckers; killed and eaten with help of radula & strong beak.
4. Have CLOSED CIRCULATORY SYSTEM - blood circulates entirely in vessels - efficient rapidly transmits food and oxygen in the active animal.
5. Shell either reduced or missing
X. Phylum Arthropoda
A. Characteristics - (* - Distinguishing Characteristic)
*1. Have jointed appendages
a. APPENDAGES - extensions of the body - includes legs and antennae
b. Phylum name means "jointed foot"
*2. Body is segmented
a. Pair of appendages attached to each segment.
b. In some species the appendages are lost or reduced in size.
*3. Have an exoskeleton
a. EXOSKELETON - hard external covering that provides protection and support.
b. Exoskeleton composed of 3 layers - all secreted by epidermis.
1) Waxy layer
2) Rigid layer of chitin - nitrogen-containing polysaccharide, combined with protein.
3) Flexible layer
c. Exoskeleton divided into plates
d. Limits size of organism.
4. Have the following systems
a. Ventral nervous system
b. Open circulatory system
c. Digestive system
d. Specialized sensory receptors
B. Movement and Growth
1. Arthropod muscles occur in bundles
a. Attached on inside of exoskeleton on either side of joints.
b. Muscle groups control movements of specific joints
c. Essentially a system of levers that move body parts and appendages.
2. Exoskeleton can't grow as body grows.
a. Must be shed periodically and new one formed
b. MOLTING (Ecdysis) - shedding of exoskeleton.
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c.
d.
e.
f.
g.
Arthropod tissue growth exerts pressure on exoskeleton walls - hormones induce molting.
Epidermal cells secrete enzymes that digest inner, flexible layer of exoskeleton.
Epidermis begins synthesis of new exoskeleton - uses digested materials from old exoskeleton.
Old exoskeleton breaks along specific lines and is shed.
New exoskeleton flexible at first - stretches to fit enlarged arthropod.
1) Some crustaceans take in water to swell.
2) Vulnerable to predators - soft-shelled crabs
3) Terrestrial species may dry out - go into hiding.
C. Evolution
1. Animals with arthropod characteristics evolved more than 600 million years ago.
2. Current studies indicate 4 separate lines of arthropod evolution.
D. Classification
1. Distinguished on basis of differences in embryological development and structural morphology of
appendages and mouthparts
a. CHELICERAE - pincer like mouthparts
b. MANDIBLES - chewing mouthparts
c. Antennae may be branched or unbranched.
2. Four Subphyla
a. Trilobita
1) All extinct
2) Trilobites
b. Crustacea
1) Branched antennae; mandibles
2) Shrimp, lobster, crabs, crayfish, barnacles, isopods (pillbugs)
3) Largest class - Class Crustacea
c. Chelicerata
1) No antennae; chelicerae
2) Spiders, scorpions, ticks, mites, sea spiders, and horseshoe crab.
3) Largest class - Class Arachnida
d. Uniramia - "one branch"
1) Antennae; mandibles - all appendages unbranched
2) Centipede, millipede, and all insects
3) Three classes
a) Diplopoda
c) Insecta
b) Chilopoda
XI. Class Crustacea
A. Mostly aquatic species.
B. Characteristics
1. Exoskeleton containing calcium carbonate in most.
2. Body divided into 3 parts - head, thorax, abdomen
3. Five head appendages
a. 2 pair of antennae
b. Chewing mouthparts - mandibles
4. Median and lateral eyes
5. Most respire by gills.
6. Have a nauplius larva - has 3 pair of appendages - develop into antennae and some mouthparts.
XII.Class Arachnida
A. Class includes spiders, scorpions, ticks and mites
B. Characteristics
1. 2 body segments
a. Cephalothorax
b. Abdomen
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2. 6 pair of jointed appendages
a. Chelicerae
b. Pedipalps - aid in chewing; sensitive to touch and chemicals
c. 4 pair of walking legs
3. Have simple eyes - most spiders have 8
4. Respiration by booklungs, tracheae, or both - most species are terrestrial; have openings called
spiracles.
a. BOOK LUNG - paired sacs in abdomen with pagelike components - large surface area.
b. TRACHEA - tubes that carry air directly to tissues.
C. Diversity
1. Spiders vary in size - feed mostly on insects.
2. Scorpions - tropical, semitropical, desert, and dry, temperate areas.
a. Pedipalps enlarged - hold prey
b. Abdomen ends in stinger that injects paralyzing venom
1) Only few species fatal to humans
2) Used mostly on large insects
3. Mites and Ticks
a. Feed on humans and animals as well as plants
b. Some transmit organisms that cause disease - Rocky Mountain Spotted Fever, Lyme Disease
D. Structure and Function
1. Shares many structural characteristics with crustaceans.
2. Respiratory system adapted to terrestrial life
3. Excretory system modified for life on land
a. Main excretory organ is MALPIGHIAN TUBULE - hollow projections of digestive track that
collect body fluids, remove wastes and carry wastes to intestine.
b. Intestine reabsorbs water.
4. Many spiders spin webs
a. 3 pair of spinnerets at tip of abdomen - made up of hundreds of microscopic tubes
b. Fluid from silk glands pass through tubes - hardens into thread that can be spun into webs
c. Silk used to build nests and egg cocoons.
5. Mating
a. Male (usually smaller than female) transfers sperm to specialized tips of pedipalps.
b. Sperm placed in female's seminal receptacle - male must be quick - he may become a meal.
c. Eggs fertilized as they pass through genital pore into nest or cocoon - laid in fall; hatch in
spring - female then dies.
XIIIMyriapods
A. Members of the Subphylum Uniramia
1. Name Myriapod means "many feet"
2. Includes centipedes and millipedes
B. Class Diplopoda
1. Millipedes - term means "thousand feet"
2. Have 2 pair of legs on each segment except last 2 segments
3. Head has short antennae and 2 groups of simple eyes
4. Body rounded
5. Use maxillae and mandibles to chew decayed matter - feed on plants
6. If threatened they roll into coil and spray noxious chemical that contains cyanide.
C. Class Chilopoda
1. Centipedes - term means "hundred feet"
2. Have only 1 pair of legs per segment - except 1st and last two.
3. Body flattened
4. Head has long antennae and 2 clumps of simple eyes
5. Appendages of 1st segment of body are poisonous claws
a. Active predators
b. Eat earthworms and insects
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XIV.Class Insecta
A. Most successful group of animals in terms of both diversity and numbers
B. Characteristics
1. Body has 3 parts - Head, Thorax, and Abdomen
2. Head has 1 pair of antennae
3. Thorax has 3 pairs of jointed legs and 1 or 2 pair of wings (if present)
4. Abdomen divided into 11 segments - no wings or legs
5. Sexes separate - reproductive organs in 8th, 9th, and 10th abdominal segments
6. Respiration through branched tracheae
C. Variation has allowed them to succeed in diverse environments
1. Structural Variations - example - differences in mouthparts
a. Wasp - chewing mouthparts
b. Aphid - piercing, sucking mouthparts
2. Physiological Variations - differences in how internal systems function
a. Female mosquito - enzymes to digest blood
b. Grasshopper - enzymes to digest grass.
3. Behavioral Variations - Ways insects respond to environment
a. Honeybees - complex societies
b. Some Bumblebees - solitary life style
XV.
Insect Development
A. Only a few insects begin life as small versions of adults - silverfish
B. Most undergo METAMORPHOSIS - series of developmental changes
C. Types of Metamorphosis
1. Incomplete Metamorphosis - has 3 stages - grasshopper, termites
a. Egg
b. NYMPH - immature form that looks like adult but smaller
1) Undeveloped reproductive organs
2) Lacks wings
3) May molt several times
c. Adult
1) Winged
2) Capable of reproducing.
2. Complete Metamorphosis - has 4 stages - Butterflies, beetles and most other insects
a. Egg
b. Larva
1) Commonly called a CATERPILLAR - wormlike
2) Eating machine
c. PUPA
1) Resting of immobile stage
2) Larval tissues breakdown and reorganize into adult tissues.
3) COCOON - in moths; woven or spun fibers
4) CHRYSALIS - in butterflies; harden material
d. Adult
1) Winged
2) Sexually mature
XVI Defense
A. Adaption that enhances survival
B. Aggressive Mechanisms
1. Bombardier Beetle - sprays predators with hot stream of noxious chemical.
2. Bees and Wasps - barbed stingers
C. Passive Mechanisms
1. CAMOUFLAGE - ability to blend into surroundings
a. Green color of grasshoppers and other insects.
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b. Leaflike appearance of Katydid
c. "Sticklike" appearance of many species - Walking Stick
2. WARNING COLORATION - bold, bright color pattern that makes insect recognizable and warns
predators away - usually have bad taste or are poisonous.
a. MULLERIAN MIMICRY - warning pattern where several poisonous or dangerous species have
similar warning coloration - black and yellow stripes of bees.
b. BATESIAN MIMICRY - coloration of harmless insect that mimics warning coloration of
dangerous or foul-tasting insect
1) Monarch Butterfly - has bitter taste due to milkweed.
2) Viceroy Butterfly - looks like monarch - not foul-tasting; predators avoid it though.
XVII. Insect Behavior
A. Societies - Ants, Termites, and Honeybees
1. Some insects live in complex societies - exhibit a division of labor
2. Honeybee Societies
a. Hive consists of 3 types of individuals.
1) WORKERS - Sterile females; ovipositor modified into stinger.
a) Perform different functions during 6 week lifetime
b) 1st week - feed honey and pollen to queen, drones, and larva; called nurse bees - produce
high protein rich substance called ROYAL JELLY - fed to queen and youngest larva
c) 2nd week - secrete wax to build and repair hive; also guard hive, remove dead bees and
wastes, and fan wings to circulate fresh air in hive.
d) Last 4 weeks - gather nectar and pollen
2) QUEEN - fertile female; only one
a) Only function is to reproduce
b) Must be fed by workers
c) Develops from same type of fertilized egg as workers - larva fed diet of royal jelly
d) Secretes QUEEN FACTOR -prevents other female larva from maturing sexually
e) Mates only once in her 5 year lifetime
3) DRONES - males; limited number
a) Develop from unfertilized egg.
b) Sole function is to fertilize queen
c) When honey supply runs low - workers kill drone by stinging them
d) Must be fed by workers.
b. If hive becomes overcrowded, queen may leave with about half of the workers to form new hive;
or if queen dies.
1) Queen factor disappears
2) Workers begin to raise new queen by feeding a group of larva royal jelly.
3) New queen emerges, produces queen factor - workers then destroy other developing queens.
3. Termite Societies
a. Queen
b. King
c. Soldiers - protect colony; both male and female
d. Workers - take care of colony; both male and female
B. Communication
1. Chemical - by PHEROMONES - chemicals released by an animal that affects behavior or
development of members of the same species.
a. Ants - follow chemical trail.
b. Some insects attracted to mates by pheromones - gypsy moth
2. Sound
a. Cricket chirping
b. Mosquito buzzing
3. Light - firefly flashes
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4. Dance Language of honeybee
a. Round Dance - used to indicate location of food close to the hive.
b. Waggle Dance - used to indicate location of food more than 50 meters from hive.
XIX.Phylum Echinodermata
A. Name means "spiny skin".
B. Important in that they appear to bear an evolutionary relationship to chordates.
1. May share a common ancestor with lower chordates and hence vertebrates.
2. Early cleavage is radial in both not spiral
3. Mesoderm arises from 2 outpocketings of endoderm not from cells between ectoderm and endoderm.
4. Blastopore becomes anus not the mouth; called deuterostomes.
C. Characteristics
1. Most undergo metamorphosis from free-swimming, bilaterally symmetrical larva to bottom
dwelling adult with PENTARADIAL SYMMETRY - 5 radii or multiples thereof.
2. Have an endoskeleton - calcium plates which may have protruding spines.
3. Have WATER-VASCULAR SYSTEM - network of water-filled canals
4. Have numerous small, movable protrusions called TUBE FEET - aid in movement, feeding,
respiration, and excretion.
5. Have no circulatory, respiratory, or excretory systems.
6. Nervous system present but lacks head or brain.
7. Sexes separate - may reproduce both sexually or asexually.
D. Evolution
1. Fossil record dates echinoderms back to Cambrian Period.
2. Early adult forms were probably sessile.
3. Radial symmetry - adaptation for sessile existence.
E. Five Classes
1. Class Crinoidea - "lilylike" - Includes sea lilies and feather stars
a. Sessile - long stalks attached to rocks or sea bottom.
b. Only class where members' mouths don't face ocean bottom.
c. 5 arms branch to form more arms.
2. Class Asteroidea - "starlike" - Includes seastars or starfish
a. Live in coastal waters and along rocky shores.
b. Economically important because they prey on oysters, clams, and other bivalves used by
humans as food.
3. Class Ophiuroidea - "snakelike" - Include basket stars and brittle stars
a. Largest echinoderm class - live primarily on sea bottom, often beneath stones and in crevices
and in holes of coral reefs.
b. Have long, narrow arms that move quickly - resemble snakes
c. Brittle stars named because arms break off easily - can regenerate.
d. Feed by raking in food with arms, by gathering from ocean bottom with tube feet,or by trapping
suspended particles with tube feet or with aid of mucous strands.
4. Class Echinoidea - "hedgehoglike" - Includes sea urchins and sand dollars
a. Internal organs enclosed in a TEST - compact, rigid endoskeleton
b. Most grind food with complex jaw mechanism called ARISTOTLE'S LANTERN
5. Class Holothuroidea - Includes armless sea cucumber
a. Lives on bottom.
b. Lack large endoskeleton - body is soft.
c. Tube feet present on aboral side - side opposite of mouth
d. Fringe of tentacles - modified tube feet - surrounds mouth.
e. Feed by sweeping up sediment, then stuffing tentacles into mouth and cleaning food off of them
f. When threatened, they may eject their internal organs through anus - process called
EVISCERATION - lost parts regenerate later.
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