arthropods chapter 28. what is an arthropod? characteristics: invertebrate animals with bilateral...
TRANSCRIPT
Arthropods
Chapter 28
What is an Arthropod? Characteristics: Invertebrate animals
with bilateral symmetry
A coelom Exoskeleton Joint appendages
Appendages Are anything like
legs, antenna that grows out of the body
Are adapted for sensing, walking, feeding & mating
Arthropods were 1st to evolve jointed appendages
Appendages Allows for more
powerful movements Different uses ex: spiders use
their 2nd pair of appendages for sensing & mating
Ex: scorpions seize their prey
Purpose of exoskeleton Gives protection Supports internal
tissue-gives muscles place to attach
Some covers entire body-some animals held together by hinges
Made of Chitin
Disadvantages of Exoskeleton Relatively heavy
structure (Jump & Fly)
Cannot grow so they shed periodically- molting
Most molt 4-7 times during their life
Most vulnerable to predators
Steps Associated with Molting1. A new one develops beneath the old one
2. The muscles contract in the rear part of the body, forcing blood forward causing this part of the body to swell & split
3. The animal wiggles out
Spider Molting
http://www.youtube.com/watch?v=zXhdr0TpOwY
Body segments of Arthropods Segments have fused
into 1 – 3 body sections
1. Head
2. Thorax
3. Abdomen
Body segments of Arthropods Other groups have 2
body segments
1. Fused head & thorax called a cephalothorax
2. abdomen
Movement Generally quick, &
active Can crawl, run,
climb, dig, swim & fly
Flies beat their wings 1000 times/sec
3 types of Gas Exchange (Air)1. Gills
aquatic arthropods (lobster, crayfish, crab…) exchange gas through gills
3 types of Gas Exchange (Air)2. Tracheal Tubes
Most insects have tracheal tubes-branching network of hollow air passages
3 types of Gas Exchange (Air)3. Book lungs
Most spiders have book lungs – air filled chambers that contain leaf-like plates that look like pages of a book
Acute Senses Movement, sound &
chemicals are detected with an antennae
Antennae also aid in communication
Antenna Ants work together
because they communicate with a pheromone-which is a chemical odor signal given off by the animal and detected with the antenna
A Bugs Life…Wonderful Example
http://www.youtube.com/watch?v=jrW_TTxP1ow
Vision is important Most arthropods have 1
pair of large compound eyes (visual structures with many lens)
Or 3-8 simple eyes (visual structure with 1 lens)
Total images make up thousands of parts (dots like a t.v. screen)
Nervous System Well-developed that
can process information coming in from the sense organ
Most excrete waste through Malpighian Tubes
Other complex body systems
Mouth parts include a variety of jaws called mandibles adapted for holding, chewing, sucking or biting different foods
Other information1. Have separate male &
female species
2. Reproduce sexually -fertilization
occurs internally in land species
-externally in aquatic species
3. Blood is pumped by 1 or more hearts to an open circulatory system
4. Have complete circulatory system, & digestive system
Beneficial to Humans1. Pollinate many
flowering plants & crop plants
2. Provide food, honey, shellac, wax & silk
3. Provide alternative chemical control of insects
4. Research has advanced in the fields of genetics, evolution, and biochemistry
-Crab shells make artificial skin, surgical sutures & antifungal medicines
Problems for Humans1. Insects eat important
crops (bole weevil)
2. Spread plant and animal disease (malaria & yellow fever)
3. Costly for us…
Crustaceans
Crustaceans: Mostly are aquatic Have mandibles for
crushing food 2 pairs of compound 2 pairs of compound
eyeseyes which are on moveable stalks
5 pairs of walking legs used to seize prey & clean appendages
Characteristics:
The first pair of walking legs are often modified into strong claws for defense.
Shrimp
Members of Crustaceans Barnacles
Crab
A Few Land Crustacean Pill Bug & Sow Bug,
two of the few land crustaceans, must live where there is moisture, which aids in gas exchange
Pill Bug
Sow Bug
Horseshoe Crab Horseshoe crabs are
considered to be living fossils & have remained relatively unchanged since the Triassic Period
They forage on sandy or muddy ocean bottoms for algae, annelids, and mollusks
Insects: class Insecta Insects have three body
segments and six legs There are more species of
insects than all other classes of animals combined.
Only group of animal that has never lost an individual to extinction
Centipedes Centipedes are
carnivorous and eat soil arthropods, snails, slugs, and worms
The bites of some centipedes are painful to humans.
Millipedes A millipede eats mostly
plants and dead material on damp forest floors.
Millipedes do not bite, but they can spray foul-smelling fluids from their defensive stink glands.
Leaf Cutter Ants
http://www.youtube.com/watch?v=RH3KYBMpxOU
Other Members… Lice, Grasshoppers,
flies, butterflies, bees & beetles….
Insect Reproduction Most insects lay a
large number of eggs, which increase the chances that some offspring will survive long enough to reproduce.
The insect embryo develops and the eggs hatch
Metamorphosis: change in body shape and form• This series of changes, controlled by
chemical-substances in the animal
• 2 types of metamorphosis
1. Complete Metamorphosis
2. Incomplete Metamorphosis
Complete Metamorphosis Complete metamorphosis consist of four stages
on their way to adulthood:
Egg Larva Pupa Adult.
Incomplete Metamorphosis Incomplete metamorphosis consist of three
stages on their way to adulthood
Egg Nymph Adult
Arachnids
Spiders, Scorpions, Mites & Ticks
Arachnids 30,000 species of
spiders – only 12 native to North America
Cannot chew food-use digestive enzyme to liquefy food
Crab Spider
Ticks & Mites Differ from spiders
because they only have one body segment
scorpions Scorpions are easily
recognized by their body segments & enlarged pinchers
They have a long tail with a venomous stinger at the tip.
Arachnids known for webs Silk is made from silk
glands & is spun into thread by spinnerets located at the rear of the spider
Link for spider webshttp://www.i-is.com/users/robin/spiderweb.html
Spider spinning an insect
http://www.youtube.com/watch?v=_-A8Oe43tjg&NR=1
Venomous Spiders… Black Widow
web used in WWI for cross-hairs in riffles
Brown Recluse
Spiders 1st pair of appendages
called chelicera (located near mouth, modified pinchers/fangs) used to hold food
2nd pair called pedipalas handle food & sensing
Banana Spider