Post on 24-Feb-2016
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Phylum Arthropoda:
Blueprint for SuccessChapter 14 and 15
Characteristics of Arthropods “Jointed foot” Modified segmentation –
body regions specialized for specific functions (tagmatization).
Chitinous exoskeleton used for support and protection
Paired, jointed appendages Growth accompanied by
molting (ecdysis)
Characteristics of Arthropods
Ventral nervous system True, but reduced
coelom Open circulatory system
where blood is released into tissue spaces (hemocoel)
Complete digestive tract Metamorphosis often
present
Arthropods Successful in almost all habitats on the earth. Most abundant animals – Several million species
identifiedo 30 to 50 million species may yet be undescribed
Triploblastic, protostome development Exhibit bilateral symmetry Four aspects contribute to arthropod success.
o 1. Metamerismo 2. Exoskeletono 3. The Hemocoelo 4. Metamorphosis
Metamerism Segmentation, most evident
externally Each external segment bears a pair
of appendages Body cavity not divided internally Permits the specialization of regions
of the body for specific functions Regional specialization =
Tagmatizationo Body regions (tagmata) specialized for:
feeding, sensory perception, locomotion, visceral functions.
The Exoskeleton External, jointed skeleton which encloses
arthropods Provides support, protection, and prevents water
loss System of levers for muscle attachment and
movement Secreted by epidermal cells
o Epidermis covered by exoskeleton on outside Consists of two layers:
o 1. Epicuticle = outermost, waxy lipoprotein layero 2. Procuticle/Endocuticle = bulky inner layer made of
chitin
The Exoskeleton Hardening of the
procuticle provides armor-like protection
Modifications of the exoskeletono Formation of jointso Sensory receptors
(bristles, lenses, etc)o Gas exchange
Must be periodically shed for growth (ecdysis)
The Exoskeleton Epicuticle and Procuticle:
epicuticle
exocuticle
endocuticle
epidermis
procuticle
The Hemocoel Provides an
internal cavity for the open circulatory system of arthropods
Allows for the exchange of nutrients, wastes, and (sometimes) gases
Metamorphosis Indirect
development, a significant change in physiology as the immature form becomes an adult
Reduces competition between adults and immature stages
Metamorphosis Evolution of arthropods has resulted in an
increasing divergence of body forms, behaviors, and habitats between immature and adult stages.o Ex: Larval crabs feed on plankton, adult crabs prowl
sandy bottoms for live prey.o Ex: Caterpillar feeds on leafy vegetables, adult butterfly
feeds on nectar from flowers.
Subphylum Crustacea Examples:
o Crayfish, crabs, lobster, shrimp, barnacles and copepods.
Two unique characteristics:o 1. Two pairs of antennae o 2. Biramous appendages
Five classes of crustaceans and numerous orderso Class Malacostraca**o Class Maxillopoda**o Class Branchiopodao Class Remipediao Class Cephalocarida
Class Malacostraca “Soft Shell” Largest class of crustaceans:
o crabs, lobsters, crayfish, shrimp, krill, isopods Body divided into two regions
o 1. Cephalothorax (fusion of sensory/feeding and locomotion tagmata)
o 2. Abdomen (a muscular tail)
Class Malacostraca Paired, biramous appendages in both body regions Appendages on Cephalothorax:
o Pairs 1 and 2 – Antennae (TWO pairs!)o Pairs 3 through 5 – Mouth appendages
• Mandible Pair (Chewing)• Maxillae (Food handling)
o Pairs 6 through 8 – Maxillipeds • Accessory sensory and food handling appendages
o Pairs 9 through 13 – Pereopods (Walking legs)• Cheliped (Pincher-like: capturing prey)
Appendages on Abdomeno Pleopods (Swimmerets)o Telson used
Class Malacostraca
Class MalacostracaReproduction
All crustaceans are dioecious
Mating occurs after molting of the female
In females, developing eggs attach to pleopods and are brooded until hatached
In males, pleopods are modified into claspers and used for sperm transfer
Crayfish have direct development
Class MalacostracaFeeding
Predators, herbivores, scavengers
Foregut includes an enlarged stomach, specialized for grinding
Midgut = “intestine” Short hindgut ends in
anus and used for water and salt regulation
Class MalacostracaGas Exchange &
Circulation Gills in gill chamber
o Between the carapace and body wall
Muscular Heart Dorsal, anterior, and
posterior arteries empty into sinuses of hemocoel
Sensory & Regulation Ventral nervous
system Compound eyes Crayfish: Excretion
organs are called “green glands”
Other crustaceans: maxillary glands
World’s Weirdest Crustaceans
http://video.nationalgeographic.com/video/animals/invertebrates-animals/crabs-lobsters-shrimp/deadliest-mantis-shrimp/
http://video.nationalgeographic.com/video/animals/invertebrates-animals/crabs-lobsters-shrimp/deadliest-pistol-shrimp/
http://video.nationalgeographic.com/video/animals/invertebrates-animals/crabs-lobsters-shrimp/lobster_locomotion/
Class Maxillopoda Includes Barnacles
and Copepods Copepods are most
abundant crustaceano Marine and
Freshwater Barnacles are
sessileo Marine onlyo Most monoeciouso Attach to various
substrateso Some are parasitic
Subphylum Chelicerata Class Arachnida Spiders, scorpions,
ticks, and mites Eights Legs No antennae or
wings Book lungs Only two body
segmentso Cephalothoraxo Abdomen
http://video.nationalgeographic.com/video/animals/bugs-animals/spiders-and-scorpions/weirdest-black-widow/
Subphylum Myriapoda “Ten thousand
foot” Terrestrial Contains millipedes
and centipedes Two body
segmentso Heado Trunk
Subphylum Hexapoda “six foot” Most successful land
animals in terms of numbers of species and individuals
Bodies divided into three tagmata
Five pairs of head appendages
Three pairs of legs on thorax
World’s Weirdest Insects
http://video.nationalgeographic.com/video/animals/bugs-animals/ants-and-termites/deadliest-army-ants/
http://video.nationalgeographic.com/video/animals/bugs-animals/bees-and-wasps/weirdest-bees-dance/
http://video.nationalgeographic.com/video/animals/bugs-animals/grasshoppers/weirdest-praying-mantis/
http://video.nationalgeographic.com/video/animals/bugs-animals/beetles/weirdest-burying-beetle/
Class Insecta 30 Orders within Class Insecta! Adult Generalized Insect Characterized by:
o Body divided into head, thorax, abdomeno Three pairs of legso Two pairs of wings
Class Insecta Body Plan
Heado Single pair of antennaeo Mouthpartso Compound eyeso 0 to 3 ocelli (simple eyes)
Thoraxo Three segments: prothorax, mesothorax, metathoraxo One pair of legs attaches to each thoracic segmento Pair of wings attach at margin between mesothorax and
metathorax Abdomen
o 10 to 11 abdominal segments
Insect Flight Insects utilize many forms of
locomotion: walk, run, jump, swim, but flight is perhaps the most important
Insects were the first animals to flyo Important from an evolutionary
perspective! Wings most likely evolved from
outgrowths of the thorax which protects the legs
Required thermoregulation Some insects use a synchronous
(direct) flight mechanism which others use an asynchronous (indirect) flight mechanism.
Insect Flight Synchronous (Direct) Flight
o Used by butterflies, dragonflies, and grasshoppers.
o Flight muscles act on wing baseso A single nerve impulse in flight muscles
results in a single wing cycle Asynchronous (Indirect) Flight:
o Used by flies and waspso Flight muscles act on body wallo Changes in shape of the thorax cause wing
movements.o A single nerve impulse results in many
cycles of the wings
Insect Feeding Variations in mouthparts include
specializations for sucking or siphoning plant or animal fluids
Mouthparts:o Labrum- upper liplike
structure, sensory and not derived from paired appendages
o Mandibles- chewing mouthparts
o Maxillae- have cutting surfaces and a sensory palp
o Labium- sensory lower lipo All aid in food handling
Insect Digestive System
Long and straight and consists of the foregut, midgut, and a hindgut.
Foreguto Behind pharynx is a crop that is used for storageo Proventriuculus or gizzard moves food to midgut helps
grind Midgut
o Aids in digestion and absorptiono Gastric cecae increase surface area
Hindguto Primarily involved with reabsorption of water
Insect Gas Exchange Gas exchange with air requires a large surface
area for the diffusion of gaseso Accomplished through highly branched systems of
chitin-lined tubes called tracheae Tracheae open to outside of body through
spiracleso Spiracles can close to prevent water loss
Most insects have ventilating mechanismso Moves air into and out of tracheal systemo Contracting flight muscleso Passive suction (vacuum) draws air ino Abdominal muscle contraction (pump)
Insect Circulation Open circulatory system similar to other
arthropods but blood vessels less well developed Blood carries nutrients, hormones, wastes Blood is not important in gas exchange Most insects are ectotherms, but some generate
heat using flight muscles
Insect Sensory Functions
Ganglion in head region Sense organs specialized for
functioning on land Insects are capable of some learning
have a memoryo Bees recognize flowerlike objectso When bees are rewarded with nectar,
they will choose flowers with that same odor in subsequent trials
Capable of detecting lighto Used in orientation, navigation, feeding,
etc Compound eyes are well developed
in adults