Arthropods Insects by mikesanye

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									              Chapter 36 Arthropods
               & Chapter 37 Insects




                          “The real rulers of the Earth”
Sources used include textbook, (Holt Modern Biology)
http://www.ucmp.berkeley.edu/arthropoda/arthropoda.html
http://evolution.berkeley.edu/evolibrary/article/_0_0/arthropods_intro_01
      Just how dominant are
           arthropods?
• More than 83% of all described animal
  species are arthropods.
• That's about 160 million insects for
  each person on Earth.
• Have evolved to fill a variety of
  ecological niches — from tiny internal
  parasite to giant bird-eating predator.
• Arthropods are a lot more than just
  delicious feasts and disgusting pests.
• What are the characteristics of an
  arthropod ?
5 Characteristics of all
     Arthropods
         Bilateral symmetry
• High degree of Cephalization
• Variety of segmented appendages around
  the mouth
• Segmented antennae- sense environment
• Compound eyes- made of many individual
  light detectors, each with their own lens.
               Segmented Body
• Each body segment tends to repeat the same
  suite of structures (ie, a pair of legs, a set of breathing
  organs, & a set of nerves),
• sets of segments are grouped into a larger unit,
  such as the abdomen & cephalothorax.
           Hard Exoskeleton
• Made of protein & Chitin (a polysaccharide)
• Must molt many times as grows
• Enzymes digest the layer of exoskeleton
  inside soften & then
  shed. It takes a few
  days for the newly
  excreted exoskeleton
  to harden.
                 Jointed Legs
• How can an animal with a rigid body covering move
  its legs? a problem for arthropods: flexibility.
• All arthropods (arthro = joint, pod = foot) have
  jointed limbs.
• In most of the leg, the exoskeleton is hard, but at the
  joints it is softer and bendable, allowing movement in
  the same way that a suit of armor does.
• The limb can be controlled by contracting muscles
  connected to the exoskeleton on both sides of the
  joint.
            Many pairs of limbs
• ancestral arthropod had
  many body segments
  with one pair of limbs
  on each segment.
• in modern arthropods,
   – some limbs have even
     been lost completely as
     they evolved to be
     smaller and smaller,
     while others have
     evolved into new shapes.
     functions.
• Tagma-specialized
  segements
         Systems in Arthropods
• All- Open circulatory system
• Respiration-
  – gills (aquatic crustaceans)
  – tracheae
  – book lungs (spiders)
• Excretion-
  – Green glands (Crusteaceans)
  – Malpighian tubules(spiders)
• Many arthropods have wings.
• The two major types of mouthparts are:
  – mandibles, which are jawlike
  – chelicerae (singular, chelicera), which are pincerlike
The five major subphyla of the
     phylum Arthropoda.
Arthropods
  usually divided
  into 5 subphyla
  based on:
  – differences in
    development
  – in the structure
    of
    appendages,
    such as
    mouthparts.
         Trilobites

• Extinct
• Many body appendages with one pair of
  appendages per segment
• Trilobites, living in shallow seas, flourished as
  swimmers, crawlers and burrowers for some 350
  million years. They evolved rapidly into many
  beautiful, bizarre and, even by today's
  standards, futuristic forms.
• Fossil evidence of these extraordinary marine
  creatures are found on all continents, entrapped
  in the hardened sediments of Ancient Seas.
                                  http://www.trilobite.com/
Subphylum Myriapoda
•   Means”many feet”
•   One pair of branched antennae
•   Many body segments
•   Includes class:
    – Diplopoda (millipedes)
      • Up to 100 body segments
      • 2 pairs of legs on each segment
    – Chilopoda (centipedes)
      • In tropical regions can reach 12 inches long
      • From 15 to 175 pairs of legs
          Subphylum Crustacea
• contains about 38,000 known species.
• Terrestrial & Marine
• so diverse their single defining characteristic is having two
  pairs of antennae.
• Most also have:
  – a pair of mandibles
  – a pair of appendages on each body segment
  – some branched appendages
  – 16 to 20 segments &
  – several tagmata
• Many have a free-swimming
larval stage called a nauplius.

                      http://copepodes.obs-banyuls.fr/images/NAUPLIUS.jpg
   a. Terrestrial Crustaceans


• Sow bugs and pill bugs are terrestrial isopods.

• They lack adaptations for conserving water and
  live only in moist environments.

• They generally feed on decaying vegetation.

• Pill bugs roll into a ball when disturbed or
  threatened.
b. Aquatic Crustaceans (many species)

• Copepods -important part of the
  ocean’s plankton.
• In freshwater, much of the                          www.divediscover.whoi.edu
  plankton are water fleas such as
  Daphnia species.
• Barnacles are sessile as adults.
  – Free-swimming barnacle larvae attach to            www.microscopyu.com
    surfaces and develop a shell that encloses
    the body.
  – Barnacles use their cirri (singular, cirrus) to
    sweep food.
                                                      www.ryanphotographic.com
    More aquatic crustaceans
• Order Decapoda -means“10 feet”
• Decapods have five pairs of legs
• Crayfish, lobsters, crabs, and shrimp are
  decapods
• Respiration through gills
• (see more about crayfish in detail at end of
  chapter- know parts for dissection lab)
 4. Subphylum Chelicerata
• Defined by presence of chelicerae
   – The first pair of appendages
   – Modified into pincer or fangs

• Class Arachnid- spiders, scorpions, mites, ticks
• Some important Parts :
   – Chelicerae ( in spiders = fangs to inject poison)
   – Pedipalps (hold food)
   – 8 simple eyes at anterior of cephalothorax (NOT compound eyes!)
   – Spinnerets- 3 pairs on tip of abdomen, for making silk
   – Book lungs- like folds in a book= lots of surface area for gas
     exchange (some spiders use Tracheae for respiration instead)
   – Malpighian Tubes- excretory tubes collect wastes, liquids. The
     liquid is reabsorbed (to conserve water) & waste is nearly solid.
 Spiders-A full facial view of any
 spider shows its killing ability.
• Two powerful chelicerae, protrude down
• Each chelicera bears a hinged fang.
• Both fangs have ducts that lead up to the venom
  glands within the head.


• Spiders fall into two groups, each being classified
  upon how they strike their prey.
   – The fangs of Tarantulas are so hinged that they articulate in
     a front-to-back motion allowing them to strike their prey
     from above.
   – Most other spiders have fangs that are hinged laterally,
     providing a left-to-right strike.
                            www.microscopix.co.uk/spiders/fangs/index.htm
               Spider Chelicerae




Fangs and Chelicerae of           Fangs, Chelicerae of Zebra Jumping Spider
Tarantula Spiderling                            Salticus scenicus
Brachypelma smithi
(Mexican Red-Knee Tarantula)


              www.microscopix.co.uk/spiders/fangs/index.htm
           Anatomy of a spider




** Mites and ticks differ from spiders because they
have a fused cephalothorax and abdomen.
             Life of a Spider
• Spiders feed on insects and other small animals.
  Many species are adapted to capture certain prey.

• Spiders rarely harm humans, but two species in
  the United States are dangerous:
   – the black widow
   – the brown recluse

• A male spider is usually smaller than the female.
• Females lay eggs in a silken case.
  5. Subphylum Hexapoda
• Class Insecta
• By many standards- the most successful group of
  animals on earth.
• Entomology- the study of insects &
  terrestrial arthropods.
• Body of an insect is divided into
  3 tagmata:
  – Head
  – Thorax
  – Abdomen
               “bugs”
• Because they dominate all
  terrestrial environments that
  support human life, insects are
  usually our most important
  competitors for food, fiber, and
  other natural resources.
   See page 743 for common
         insect orders

• See Example organism: Grasshopper
• Please note parts for dissection lab,
  see p 745 text.
   The crayfish- next 4 pages are
      notes for dissection lab
• an abundant freshwater crustacean that is
  structurally similar to lobsters, which are
  marine crustaceans.

• Crayfish, lobsters, crabs, and shrimp are
  decapods, or members of the order
  Decapoda. Decapoda means “10 feet.”

• Decapods have five pairs of legs that are
  used for locomotion.
                 External Structure
• The crayfish’s body is divided into
   – the cephalothorax, which is covered by the
     carapace and is divided into
        • the head, which has five segments
        • the thorax, which has eight segments
   – the abdomen, which is is divided into six segments
• A pair of appendages is attached to each segment of the
  crayfish. Several pairs have specialized functions.

• These appendages include:
   –   Antennae
   –   Antennules
   –   Mandibles
   –   Maxillae
   –   Maxillipeds
   –   Chelipeds
   –   Walking legs
   –   Swimmerets
Crayfish -Parts for lab
Excretion
• Green glands assist in excretion of excess water that
  enters the body by osmosis.

Digestion
• Digestive gland near the stomach secretes enzymes for
  digestion.

Respiration
• gills.

Circulation
• open.

Nervous & Sensory Organs
• Many small sensory hairs. (sense water vibrations & chemicals)
  Compound eyes are set on two stalks.
      Chapter 37 Insects
• Entomologists classify insects into more
 than 25 orders based on characteristics
 such as:
  – structure of mouthparts
  – number of wings
  – type of development
Factors responsible for their success include:
  –ability to fly             -exoskeleton
  –jointed appendages         -small size
  –large numbers offspring    -short life span
Just how dominant are insects?
Comparison of 2 of the 5 groups of
          Arthropods
                    Insects as Food
•   http://www.cals.ncsu.edu/course/ent425/text01/index.html

•   Insects were undoubtedly an important source of nutrition for our early
    human ancestors. Even today, they are still collected and eaten by people
    of many cultures. In Mexico, dried grasshoppers are sold in village
    markets. High in protein and low in fat, they may be fried or ground into
    meal and mixed with flour to make tortillas. Sago grubs, the larvae of a
    wood-boring beetle, are considered a delicacy in Papua New Guinea. The
    islanders boil the larvae or roast them over an open fire. Ants, bees,
    termites, caterpillars, water bugs, beetle larvae, flies, crickets, katydids,
    cicadas, and dragonfly nymphs are among a long list of edible insects that
    provide nutrition for the people of Australia, Africa, South America, the
    Middle East, and the Far East. Indeed, Americans and other descendents of
    western European culture appear to be unique among peoples of the world
    in having such a strong cultural taboo against the use of insects as food.


•   Silkworm pupae for
    human food in
    Thailand
A Recipe for Maggot Crispies
• 1/4 cup margarine
  4 cups small marshmallows
  3 cups crispy cereal
  3 cups dry roasted maggots or mealworms
  In a saucepan, melt margarine and
  marshmallows. Remove from heat and stir
  in cereal and maggots. Spread mixture in
  a 9x13 greased pan and allow to cool.
            Insect body –
  is divided into three tagmata:

1. Head -has mandibles and one pair of
   unbranched antennae.
2. Thorax -has three pairs of jointed legs
   and, in many species, one or two pairs
   of wings.
3. Abdomen -has 9 to 11 segments but
   neither wings nor legs in adults.
        Insects and People
• Insects negatively affect humans by:
  – competing for food
  – transmitting diseases
  – destroying buildings & other manufactured
    products


• Insects benefit humans by:
  – serving as food for other animals
  – pollinating flowers
  – making valuable products such as honey
  – recycling nutrients in ecosystems
External Anatomy Grasshopper
Internal Anatomy Grasshopper
   Grasshopper body- three
          tagmata:
– The head
  • mouthparts -labrum & labium are mouthparts that
    function like upper and lower lips, respectively.
  • a pair of unbranched antennae
  • pairs of simple and compound eyes.

– The thorax is composed of:
  • Prothorax
  • Mesothorax
  • Metathorax
– The   abdomen has upper and lower plates
Insect mouthparts
    Circulation, Respiration, &
             Excretion

• Insects have an open circulatory
  system that transports nutrients through
  the body.

• Gas exchange occurs by means of air-filled
  tracheae that reach deep into the body.

• Malpighian tubules remove cellular
  wastes from the hemolymph while
            Nervous system
• The grasshopper’s central nervous system
  consists of a brain and a ventral nerve
  cord with ganglia located in each body
  segment.
• Nerves extend from the brain to sensory
  structures.
• Insect sensory structures include :
  – simple and compound eyes
  – sensory hairs on antennae and other body
    parts
  – in some species, a sound-sensing tympanum
         Reproduction
• Grasshoppers have separate sexes,
   – as do all insects.
• During mating, the male deposits sperm
  into the female’s seminal receptacle,
  where the eggs are fertilized internally.
• The last segment of the female’s
  abdomen forms the ovipositor, which
  she uses to lay fertilized eggs.
       Most insects go through
         metamorphosis.
• In incomplete metamorphosis, a nymph
  hatches from an egg and resembles the adult
  but has undeveloped reproductive organs and
  no wings. The nymph molts several times to
  become an adult.

• In complete metamorphosis, a wormlike
  larva called a caterpillar hatches from an
  egg and molts several times before becoming a
  pupa. The pupa molts to produce the adult,
  which resembles neither the larva nor the
  pupa.
           Incomplete vs. Complete
                 metamorphosis




Complete metamorphosis
     -allows larvae and adults of the same species to avoid competing
            for space and food.
     -allows survival in periods of harsh weather or scant resources.
See writing assignment sheet

								
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