Chapter TwentySeven

1
Chapter Twenty-Seven

• The Animal Kingdom III
• Arthropods Part II

2
The Terrestrial Mandibulates Myriapods

• Many-footed
• Single pair of antennae
• Mandibles
• Respire through tracheae
• Excretion by way of Malpighian tubules

http//www.brookview.karoo.net/Sellafield_Zoo/Bear
s/Bear_with_many_feet.jpg
3
Myriapods -Classes Chilopoda Diplopoda

• Class Chilopoda (centipedes) Diplopoda
  (millipedes) are most familiar myriapods
• Prefer damp area and are carnivorous feeding on
  other insects however, millipedes are
  herbivorous and feed on decaying vegetation
• Centipede-one pair of appendages on each body
  segment
• Millipede-two pairs of appendages per body segment

http//donaxtell.home.att.net/jamaica/2002/centipe
de.jpg
4
Myriapods Classes Pauropoda Symphyla

• 300 species of Class Pauropoda
• 130 species of Class Symphyla
• Unlike other arthropods, they are soft-bodied,
  living in moist soil, leaf litter, and other
  decaying matter
• Although both classes are abundant, they are
  quite small and they usually go about unnoticed
  by the human eye

5
The Terrestrial Mandibulates Class Insecta

• Largest class of arthropods, in fact more than
  70 of all animal species are insects
• Only invertebrates capable of flight
• Four largest orders
• Diptera two-winged
• Lepidoptera scale-winged
• Hymenoptera membrane-winged
• Coleoptera shield-winged

http//www.anatomorphex.com/picts/animals/AN040_FL
YING_BEETLE.jpg
6
Insect Characteristics

• Three body regions head, thorax, abdomen
• Three pairs of legs
• One pair of antennae
• Set of complex mouthparts used for many different
  things
• Most adult insects have two pairs of wings made
  up light, strong sheets of chitin

http//www.enchantedlearning.com/ggifs/Grasshopper
_bw.GIF
7
Digestive, Excretory, and Respiratory Systems

• The stomach, or midgut, which lies mainly in the
  abdomen, is the chief organ of absorption
• Excretion is carried out through Malpighian
  tubules
• To promote water conservation, nitrogenous wastes
  are eliminated in the form of dry crystals of
  uric acid
• The respiratory system consists of a network of
  cuticle-lined tubules through which air
  circulates to the various tissues of the body,
  supplying each cell directly

8
Insect Life Histories

• Most biological function of larvae seems to be
  the invasion and selection of new habitats at
  some distance from the parental habitat
• Insect young are voracious feeders
• In many insects, some degree of parental care has
  evolved, with one or both parents protecting and
  feeding the young, or both
• Young growing insects change not only in size but
  often in form, a phenomenon known as
  metamorphosis
• Immature, nonreproductive forms are known as
  nymphs
• In 90 of insect species, a complete
  metamorphosis occurs, and the adults are
  drastically different from the immature forms, or
  larvae

9
Insect Life Histories

• Complete metamorphosis occurs in four different
  forms(1)the egg or embryo,(2)larva, (3)pupa,
  (4)adult
• Stages between molts are know as instars
• This metamorphosis is the famous transition from
  caterpillar to butterfly
• Molting and metamorphosis are under the control
  of hormones, which are organic molecules secreted
  by one tissue of an organism that regulate the
  functions of another tissue or organ of the same
  organism

http//www.wcer.wisc.edu/NCISLA/MUSE/naturalselect
ion/materials/section4/lesson4A/handouts/usgs1.jpg
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Arthropod Success

• Nature of exoskeleton which waterproofs, provides
  protection, makes possible for evolution of
  specialized appendages
• Small size and the high specificity of diet
• Complete metamorphosis that occurs in the vast
  majority of insect species
• Arthropod nervous system, with control of carious
  appendages and sensory organs

http//www.zadams.com/vita/photographs/despair/suc
cess.jpg
11
Arthropod Senses and Behavior The Compound Eye

• Basic structural unit of this eye is the
  ommatidium, repeated over and over
• Light sensitive portion of ommatidium is the
  rhabdom, which is the central core of the
  ommatidium
• Although the compound eye is deficient in acuity,
  offering less detail than the vertebrate eye, it
  is better for detecting motion because each
  ommatidium is stimulated separately and so has a
  separate visual field (very important adaptation
  for flight)
• In addition to, or instead of, compound eyes,
  many of the arthropods possess simple eyes, or
  ocelli, which seem generally to serve only for
  light detection.

12
Touch Receptors

• Body surfaces of terrestrial arthropods are often
  covered with sensory-receptor units known as
  sensilla or little sense organs
• In addition to being stimulated by direct
  contact, they can also be stimulated by
  vibrations and air currents

http//www.holyhacker.com/images/michaelangelo-cre
ation_hand.jpg
13
Proprioceptors

• Proprioceptors are sensory receptors that provide
  information about the position of various parts
  of the body and the stresses and strains on them
• Touch receptors can also serve as proprioceptors,
  like praying mantis do

http//www.1000plus.com/Hbirds/01092220DSBG20Pra
ying20Mantis20.JPG
14
Communication by Sound

• Arthropods, particularly insects, have developed
  complex forms of communication
• Five distinct types of calls are known(1)calling
  by males,(2)calling by females,(3)courtship
  sounds by males,(4)aggressive sounds by males,
  and (5)alarm sounds
• Recognition of and response to the sound may be
  based on its pattern, rhythm, or frequency (pitch)

http//highroad.org/ranch20images/Insects/cricket
-grey.jpg
15
Communication by Pheromones

• Many insects communicate by chemicals known as
  pheromones. These chemical messengers are
  discharged into the environment, where they act
  on other members of the same species
• Among the best studied pheromones are the mating
  substances of moths
• Female gypsy moths, by emission of minute amounts
  of a pheromone commonly known as disparlure, can
  attract male moths that are several kilometers
  downwind.