Arthropods Chapter 28. Arthropod characteristics Segmented bodies Tough exoskeleton made of chitin...
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Transcript of Arthropods Chapter 28. Arthropod characteristics Segmented bodies Tough exoskeleton made of chitin...
ArthropodsChapter 28
Arthropod characteristics
• Segmented bodies
• Tough exoskeleton made of chitin– Multiple shapes and textures
• Jointed appendages: legs and antennae
Arthropod evolution
• Modern arthropods have fewer body segments and more specialized appendages.
Fossil of a Trilobite, extinct class of Arthropod
Fossil of Leanchoilia, Phylum Arthopoda
www.burgess-shale.bc.ca/ gallery/gallery.htm
Feeding• Herbivores, carnivores, omnivores,
parasites, blood suckers, filter feeders, and detritovores
• Variety of mouthparts: pincers, fangs, sickle-shaped jaws, feeding tubes
stag beetle pincers
Respiration
• Most arthropods– Tracheal tubes: branching network of tubes
that deliver and expel air through spiracles
• Some arthropods (including spiders)– Book lungs: layers of respiratory tissue
stacked like pages of a book
Circulation
• Open circulatory system: heart pumps blood to tissues, sinuses, and cavities but does not return to the heart directly
Excretion
• Malpighian tubules: saclike organs that extract wastes from blood and then add them to feces to move through the gut
Chrysina quetzalcoatli is freed in Cusuco
National Park, leaving a fecal trail
National Geographic
Response
• Sensitive sensory organs (sight, smell, touch)
• Well-developed nervous system – Brain– Ventral nerve cord– Ganglia: groups of nerve cells
Movement
• Flexor muscles
• Extensor muscles
• Muscle pulling against exoskeleton enables movement
Reproduction
• Terrestrial arthropods: internal fertilization– Male places sperm in female– Sperm sac that female picks up
• Aquatic arthropods: internal or external fertilization
Growth and development
• Molting: period of shedding exoskeleton when outgrown– Glands secrete
digestive enzymes to break down exoskeleton.
– Glands secrete new exoskeleton.
– Vulnerable stage
Insect molting case left on tree bark
Arthropod subphylums
• Crustaceans• Spiders and their relatives• Insects and their relatives
Crustacean characteristics
• Two pairs of antennae• Two or three body sections• Mandibles: chewing mouthparts• Body plan: celphalothorax, abdomen, carapace• Barnacles have “lost” appendages.• Decapods have chelipeds and swimmerets.
– Ex: shrimp, lobster, crayfish
Section 28-2
AbdomenCephalothorax
Walking legs
Tail
Swimmerets
Carapace
Cheliped
MandibleSecond antenna
First antenna
The Anatomy of a Crayfish
Subphylum Crustacea – hermit crab
Subphylum Crustacea –crab
Subphylum Crustacea – fire shrimp
Chelicerate characteristics
• Four pairs of walking legs• Chelicerae mouthparts: fangs that sting
and pedipalps that grab prey• Two body sections: cephalothorax and
abdomen• Classes: Merostomata (horseshoe crabs)
and Arachnida (spiders, scorpions)• Spiders have spinnerets, silk glands.
Section 28-2
AbdomenCephalothorax
Book Lung
Eyes
Brain
Pumpingstomach
Heart
Intestine
Ovary
Malpighiantubules
Anus
SpinneretsSilk glands
Spiracle
Bases ofwalking legs
Fanglikechelicera
Pedipalp
Poisongland
Airflow
The Anatomy of a Spider
Figure 28–9
Subphylum Arachnida – black widow spider
Scorpion
Gum shoe spider web Theridae family
National Geographic
Photo by Darlyne A. Murawski
Uniramia characteristics
• Jaws
• One pair of antennae
• Unbranched appendages
• Groups: centipedes, millipedes, insects
Millipede
Centipede
Why insects are evolutionarily successful
• Flight
• Variety of stimuli responses
• Differential feeding methods between young and adult
• Different morphology between young and adult
Insect characteristics
• Compound eyes
• Some with wings
• Three part body plan
• Three pairs of legs
• Sensitive taste and smell receptors• Three appendages for mouth,
including pair of mandibles
Section 28-1
Ventral View
Antennae
Compound eyeBrain Digestive
tract Malpighian tubules
Heart
Reproductive organs
Anus
SpiraclesTrachealtubes
Nervecord
Ganglia
Salivaryglands
Mouth
Tracheal tubes
Spiracles
Legs
The Anatomy of a Grasshopper
Figure 28–4
Insect life cycle
• Metamorphosis: process of changing shape and form from juvenile to adult stage– Incomplete: juvenile stage (nymphs) appear
like adults, just smaller– Complete: juvenile stage (larvae) becomes
pupa, final stage before becoming an adult
Section 28-3
IncompleteMetamorphosis
CompleteMetamorphosis
Eggs
Larva
Pupa
Adult
Nymph
Nymph
Nymph
Adult
Eggs
Larva
Adult
Adult
Immature
Metamorphosis
Figure 28–18
• Although they can be a nuisance or pest, insects are significant to agriculture.
• They facilitate flower pollination.
Insects and humans
Insect communication and societies
• Chemical cues: pheromones
• Visual cues: light, flight patterns
• Some insects form societies where castes, groups of individuals, perform specific tasks.
Polyphemus moth Pheromone chemical: (E,Z)-6,11-Hexadecadienyl acetate
National Geographic
Image by Joseph Scheer
Subphylum Insecta – lady bug
Subphylum Insecta – bee moth