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Phylum Arthropoda:

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Arthropods . Successful in almost all habitats on the earth. Most abundant animals Several million species identified. 30 to 50 million species may yet be undescribed – PowerPoint PPT presentation

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Title: Phylum Arthropoda:


1
Phylum Arthropoda
  • Blueprint for Success
  • Chapter 14 and 15

2
Characteristics of Arthropods
  • Modified segmentation body regions specialized
    for specific functions (tagmatization).
  • Chitinous exoskeleton used for support and
    protection
  • Paired, jointed appendages
  • Growth accompanied by molting (ecdysis)

3
Characteristics of Arthropods
  • Ventral nervous system
  • Reduced coelom
  • Open circulatory system where blood is released
    into tissue spaces (hemocoel)
  • Complete digestive tract
  • Metamorphosis often present

4
Arthropods
  • Successful in almost all habitats on the earth.
  • Most abundant animals Several million species
    identified
  • 30 to 50 million species may yet be undescribed
  • Triploblastic, protostome development
  • Exhibit bilateral symmetry
  • Four aspects contribute to arthropod success.
  • 1. Metamerism
  • 2. Exoskeleton
  • 3. The Hemocoel
  • 4. Metamorphosis

5
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 Tagmatization
  • Body regions (tagmata) specialized for feeding,
    sensory perception, locomotion, visceral
    functions.

6
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
  • Epidermis covered by exoskeleton on outside
  • Consists of two layers
  • 1. Epicuticle outermost, waxy lipoprotein layer
  • 2. Procuticle/Endocuticle bulky inner layer
    made of chitin

7
The Exoskeleton
  • Hardening of the procuticle provides armor-like
    protection
  • Modifications of the exoskeleton
  • Formation of joints
  • Sensory receptors (bristles, lenses, etc)
  • Gas exchange
  • Must be periodically shed for growth (ecdysis)

8
The Exoskeleton
  • Epicuticle and Procuticle

epicuticle
exocuticle
procuticle
endocuticle
epidermis
9
The Hemocoel
  • Provides an internal cavity for the open
    circulatory system of arthropods
  • Allows for the exchange of nutrients, wastes, and
    (sometimes) gases

10
Metamorphosis
  • Indirect development, a significant change in
    physiology as the immature form becomes an adult
  • Reduces competition between adults and immature
    stages

11
Metamorphosis
  • Evolution of arthropods has resulted in an
    increasing divergence of body forms, behaviors,
    and habitats between immature and adult stages.
  • Ex Larval crabs feed on plankton, adult crabs
    prowl sandy bottoms for live prey.
  • Ex Caterpillar feeds on leafy vegetables, adult
    butterfly feeds on nectar from flowers.

12
Subphylum Crustacea
  • Examples
  • Crayfish, crabs, lobster, shrimp, barnacles and
    copepods.
  • Two unique characteristics
  • 1. Two pairs of antennae
  • 2. Biramous appendages
  • Five classes of crustaceans and numerous orders
  • Class Malacostraca
  • Class Maxillopoda
  • Class Branchiopoda
  • Class Remipedia
  • Class Cephalocarida

13
Class Malacostraca
  • Soft Shell
  • Largest class of crustaceans
  • crabs, lobsters, crayfish, shrimp, krill, isopods
  • Body divided into two regions
  • 1. Cephalothorax (fusion of sensory/feeding and
    locomotion tagmata)
  • 2. Abdomen (a muscular tail)

14
Class Malacostraca
  • Paired, biramous appendages in both body regions
  • Appendages on Cephalothorax
  • Pairs 1 and 2 Antennae (TWO pairs!)
  • Pairs 3 through 5 Mouth appendages
  • Mandible Pair (Chewing)
  • Maxillae (Food handling)
  • Pairs 6 through 8 Maxillipeds
  • Accessory sensory and food handling appendages
  • Pairs 9 through 13 Pereopods (Walking legs)
  • Cheliped (Pincher-like)
  • Appendages on Abdomen
  • Pleopods (Swimmerets)
  • Telson used

15
Class Malacostraca
16
Class Malacostraca
  • Reproduction
  • 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

17
Class Malacostraca
  • Feeding
  • 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

18
Class Malacostraca
  • Gas Exchange Circulation
  • Sensory Regulation
  • Gills in gill chamber
  • Between the carapace and body wall
  • Muscular Heart
  • Dorsal, anterior, and posterior arteries empty
    into sinuses of hemocoel
  • Ventral nervous system
  • Compound eyes
  • Crayfish Excretion organs are called green
    glands
  • Other crustaceans maxillary glands

19
Class Maxillopoda
  • Includes Barnacles and Copepods
  • Copepods are most abundant crustacean
  • Marine and Freshwater
  • Barnacles are sessile
  • Marine only
  • Most monoecious
  • Attach to various substrates
  • Some are parasitic

20
Subphylum Hexapoda
  • 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

21
Class Insecta
  • 30 Orders within Class Insecta!
  • Adult Generalized Insect Characterized by
  • Body divided into head, thorax, abdomen
  • Three pairs of legs
  • Two pairs of wings

22
Class Insecta Body Plan
  • Head
  • Single pair of antennae
  • Mouthparts
  • Compound eyes
  • 0 to 3 ocelli (simple eyes)
  • Thorax
  • Three segments prothorax, mesothorax, metathorax
  • One pair of legs attaches to each thoracic
    segment
  • Pair of wings attach at margin between mesothorax
    and metathorax
  • Abdomen
  • 10 to 11 abdominal segments

23
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 fly
  • 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.

24
Insect Flight
  • Synchronous (Direct) Flight
  • Used by butterflies, dragonflies, and
    grasshoppers.
  • Flight muscles act on wing bases
  • A single nerve impulse in flight muscles results
    in a single wing cycle
  • Asynchronous (Indirect) Flight
  • Used by flies and wasps
  • Flight muscles act on body wall
  • Changes in shape of the thorax cause wing
    movements.
  • A single nerve impulse results in many cycles of
    the wings

25
Insect Feeding
  • Variations in mouthparts include specializations
    for sucking or siphoning plant or animal fluids
  • Mouthparts
  • Labrum- upper liplike structure, sensory and not
    derived from paired appendages
  • Mandibles- chewing mouthparts
  • Maxillae- have cutting surfaces and a sensory
    palp
  • Labium- sensory lower lip
  • All aid in food handling

26
Insect Digestive System
  • Long and straight and consists of the foregut,
    midgut, and a hindgut.
  • Foregut
  • Behind pharynx is a crop that is used for storage
  • Proventriuculus or gizzard moves food to midgut
    helps grind
  • Midgut
  • Aids in digestion and absorption
  • Gastric cecae increase surface area
  • Hindgut
  • Primarily involved with reabsorption
  • of water

27
Insect Gas Exchange
  • Gas exchange with air requires a large surface
    area for the diffusion of gases
  • Accomplished through highly branched systems of
    chitin-lined tubes called tracheae
  • Tracheae open to outside of body through
    spiracles
  • Spiracles can close to prevent water loss
  • Most insects have ventilating mechanisms
  • Moves air into and out of tracheal system
  • Contracting flight muscles
  • Passive suction (vacuum) draws air in
  • Abdominal muscle contraction (pump)

28
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

29
Insect Sensory Functions
  • Ganglion in head region
  • Sense organs specialized for functioning on land
  • Insects are capable of some learning have a
    memory
  • Bees recognize flowerlike objects
  • When bees are rewarded with nectar, they will
    choose flowers with that same odor in subsequent
    trials
  • Capable of detecting light
  • Used in orientation, navigation, feeding, etc
  • Compound eyes are well developed in adults
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