Download Phylum Arthropoda

• 1,000,000 + species
• “jointed appendages”
• Eumatazoan, triploblastic coelomates
• Bilaterally symmetrical protostomes
Major features of Arthropods:
1. Evolved segmentation
2. Exoskeleton
3. Jointed appendages
4. Open circulatory system
• The most biologically successful of all animals
• Well developed senses
• Prolific reproductively
• Over half of all known species belong to the arthropod phulym
• Diverse organisms
• Specialized structures (wings)
• Well adapted senses (compound eyes & antennae)
• Live in a great variety of environments (exoskeleton – not bound to water)
• aquatic & terrestrial
• High reproductive potential (quickly reproduce)
• Many lay 1,000’s of eggs during life
• Immeasurably vast ecological impact
• Food sources
• Detrivores – eat dead, decaying organisms (nature’s recyclers)
• Pollinators
• Help plant populations
• Pests
• Fleas, ticks, mosquitoes
• Agricultural pests
• “Home invaders”
• Exoskeleton – a hardened cuticle of protein and chitin
• For protection, body structure, and muscle attachment
• Prevents water loss
• Thick and hard in some areas
• Paper thin and flexible in others (jointed areas)
• Ecdysis – molting process
• Allows arthropods to grow
• Molting is energetically expensive and leaves arthropods
vulnerable
• Evolved segmentation
• Fusion of segments and specialization via function of body
• Tagmata – head, thorax (chest), abdomen
• Efficient body plan (division of labor)
• Modified, specialized, and adapted for:
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Locomotion (walking legs, “tails”, wings)
Feeding (mouthparts, pincers)
Sensory reception (antennae)
Defense (pincers, stingers)
Copulation (egg and sperm deposit)
• Digestion system is complete (annelid like)
• Respiratory
• Internalized lungs or gills for diffusion of gas, despite having an
exoskeleton
• Most insects have a tracheal system that is branched leading to pores
along the exoskeleton (believed that this system limits the size of
bugs)
• Open circulatory system
• Hemolymph is the fluid pumped by the heart through short arteries
and spills into sinus spaces, called hemocoels, surrounding tissues
and organs (not part of the body cavity)
• Reproductive
• Extremely prolific
• Males seek females
• Mostly egg layers
• Sensory system is highly developed and Complex
• Compound eyes (most insects)
• 1,000’s of lenses – vision looks like a tile mosaic
• Excellent at detecting motion
• Antennae (touch/vibrations and smell sensors)
• Pheromones - Chemical messages or “smells”
• Used by insects of a species to communicate with
members of the same species.
• Reproduction (mate attraction)
• Trail markers (ants)
• Alarm signals (ants, bees)
• Queen – messages to colony
• Subphylum Chelicerata
• Class Merostomata (horseshoe crabs)
• Class Arachnida (spiders, scorpions, ticks, mites)
• Subphylum Crustacea
• Class Malacostraca (lobsters, crabs, shrimp)
• Class Maxillopoda (barnacles & copepods))
• Subphylum Hexapoda
• Class Insecta (beetles, butterflies, ants, etc.)
• Subphylum Myriapoda
• Class Chilopoda (centipedes)
• Class Diplopoda (millipedes)
• Examples: Crayfish, lobster, crab, aquatic isopods, rolly
pollies
• Three body sections- head, chest, and abdomenusually the head and chest are fused into the
“cephalothorax.”
• Most are aquatic
• Use gills for respiration
• Examples: ants, bees, house flies
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Adult insects have 3 body parts: head, thorax, and
abdomen.
Adult insects have 6 legs
Adult insects have compound eyes
Most adult insects have antennae, 2 pairs of wings, and
can fly.
Most insects have 4 stages in their life cycle: egg, larva,
pupa, adult
Have spiracles and trachea for breathing
• Examples: horseshoe crabs, spiders,
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Body consists of two main parts: a fused head and thorax
(cephalothorax) and an abdomen.
Most live on land and breathe by means of book lungs (so
called because their thin membranes are arranged like the
pages of a book)
Six pairs of appendages on the body
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the first pair are clawlike fangs near the mouth used for grasping
and cutting
the second pair serve as general-purpose mouth parts that may be
modified for special functions
the last four pairs of appendages are the walking legs
• Example: Centipedes
• Characteristics:
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1 pair of legs per body segment
1 pair of poison claws/fangs underneath the head
Antennae present
Simple eyes
Flatter body
• Characteristics
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Simple eyes if present, although many have no eyes
1 pair of antennae
Chewing mouthparts
Although it looks like millipedes have 2 pair of legs on each segment, closer
examination shows that each body segment is actually 2 segments fused together.
• Millipedes are timid invertebrates and unlike centipedes, do not have poisonous claws
so to protect themselves and to discourage predators they roll into a tight spiral and
often discharge a foul smelling, distasteful
• More circular shaped body
Digestive system
Mouth-pharynx-esophagus-crop-gizzard-intestineCrop- stores food
Gizzard- grinds food
Digestive Gland (Gastric caeca)- makes digestive
enzymes
• Open circulatory system
• Heart- on dorsal side of body
• Dorsal blood vessel leading towards and away
from heart
• Blood flows out of heart towards the head, down
to the ventral side of the body towards the tail and
back to the heart
• Some insects have 2 tympanic membranes- These vibrate
when sound waves hit it
• Honeybees
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Can see color
four of the visual cells in each lens respond best to yellow-green light
two respond maximally to blue light
the remaining two respond best to ultraviolet light
• Monarch butterflies, which can migrate over 2000 miles,
navigate by ultraviolet light in the sky.