Ch 28 Arthropods

Question 1

How diverse are arthropods

Answer 1

• Very numerous and diverse group of animals
• Over 1,000,000 species

Question 2

what are the 4 phyla of arthropods

Answer 2

• Trilobita: A very old and now extinct group containing trilobites
• Chelicerata: Spiders, ticks, mites, scorpions, horse-shoe crabs
• Crustacea: Crabs, shrimp, lobster, etc
• Uniramia: Centipedes, millipeds, insects, etc

Question 3

how do arthropods first arise

Answer 3

• appeared over 600 million years ago
• first terrestrial animals
• little known about how they began, probably the earliest were similar to trilobites: thick outer body with many segments and paired appendages with a feathery gill and walking leg
• modern arthropods have lost many segments and have become more specialized

Question 4

what is the basic form and function of arthropods

Answer 4

• varies a lot
• 3 shared characteristics
  
  • tough exoskeleton
  • series of jointed appendages
  • segmented body
• typically have a brain, ventral nerve cord, and open circulatory system with 1 heart

Question 5

what is the arthropod body plan

Answer 5

• exoskeleton made typically of chitin, can be leathery and flexible, or hard and rigid
• in terrestrial arthropods the exoskeleton is water proof
• restricts growth and movement (they can only move at joints)
• have multiple jointed appendages that are specialized, ex antennae, claws, legs, wings, flippers, etc
• multiple segments, can be many or few

Question 6

how do arthropods feed

Answer 6

• evolved in various ways to eat pretty much anything
• specialists or generalists
• structures for carnivory, herbivory, detritus feeding, filter feeding, internal parasitism or external parasitism

Question 7

how do arthropods breath

Answer 7

• gills
• book gills or book lungs
• tracheal tubes
• many aquatic arthropods like crabs have feathery gills formed from part of the mouth or legs
• book gills are found in horseshoe crabs
• book lungs found in spiders and their relatives
• book lungs and book gills are both layers of tissue like a book that are in a sac (for lungs) or under the body (for gills)
• Spiracles are tubes used in respiration connected to the outside
• movement causes tracheal tubes to contract, pumping O2

Question 8

how do arthropods do internal transport

Answer 8

• in arthropods a well developed heart pumps through an open circulatory system
• in spiders and some insects the heart is long and narrow and lies along the abdomen
• in lobsters and crayfish the heart is smaller

Question 9

how do arthropods excrete

Answer 9

• anus for digested materials
• in terrestrial species malpighian tubules remove waste from blood in sinuses, then add to undigested waste
• may have small glands
• diffusion for aquatic taxa
• through gills

Question 10

how do arthropods do response

Answer 10

• well developed
• brain formed from ganglia
• nerve cord
• ganglia lie in various segments
• statocysts and chem receptors
• compound eyes are common (they have 2000+ lenses)
• many see UV light, or have better vision than humans
• crustaceans and insects can taste
• special hairs are used for sensing
• ears often in odd places
• various defense mechanisms

Question 11

how do arthropods move

Answer 11

• muscles generate force to exoskeleton
• move at joints

Question 12

how do arthropods reproduce

Answer 12

• male and females produce eggs and sperm
• internal fertilization

Question 13

how do arthropods grow and develop

Answer 13

• exoskeleton inhibits growth
• they must molt, by shedding the exoskeleton, to grow
• in molting the epidermis ingests the inner layer of the exoskeleton and a new soft one is formed, the body pulls out of the shell and inflates before the new one solidifies
• arthropods often undergo metamorphosis to change form
• incomplete metamorphosis involves babies looking like adults as they grow
• complete metamorphosis involves larva that are very different, they grow and become a pupa, where they completely change form

Question 14

what is sub-phyla chelicerata

Answer 14

• sub-phyla chelicerata
• spiders, horseshoe crabs, ticks, scorpions, etc
• all have 2 part body and mouth parts called chelicerae
• also lack sensory feelers near head
• 2 body parts: cephalothorax and abdomen
• cephalothorax contains brain, eyes, mouth, mouth parts, esophagus, front of digestive system and some legs
• Abdomen contains most internal organs
• all chelicerates have 2 pairs of mouth parts near the mouth, the first is called chelicerae and the second is pedipalps, differ between groups

Question 15

what are horseshoe crabs

Answer 15

• not crabs
• appeared in ordovician (430+ million years ago)
• 5 pairs of legs and long spike like tail
• larva are called trilobite larva as they look like trilobites
• grow from 1cm at hatching up to 60 cm0

Question 16

what are arachnids

Answer 16

• spiders, scorpions, ticks, mites
• 4 pairs of legs on cephalothorax
• many are carnivores with pedipalps adapted to hold prey and chelicerae used to bite and suck prey

Question 17

what are spiders

Answer 17

• carnivores, small prey like insects or small vertebrates
• may use webs or dents to ambush prey
• chelicerae inject venom
• enzymes break down tissue, turning it into soup while it is sucked up
• produce a protein called silk with gland in the abdomen, six times stronger than steel
• use spinnerets to make webs and structures

Question 18

what are mites and ticks

Answer 18

• parasites , very small
• chelicerae are needle like and pierce host
• pedipalps may have claws to attach to host
• cause many diseases and problems

Question 19

what are scorpions

Answer 19

• warm weather carnivores, small invertebrates
• pedipalps are claws
• have stinging barbs on abdomen
• chews prey using chelicerae

Question 20

what is sub-phyla Crustacea

Answer 20

• subphyla crustacea
• 35000+ species
• mainly aquatic
• vary in size

Question 21

what is subphyla uniramia

Answer 21

• so many species, more than any other group
• subphyla uniramia
• centipedes, millipedes, insects
• have one pair of antennae and no branching appendages
• evolved on land 400+ million years ago

Question 22

what is the form of crustaceans

Answer 22

• have hard exoskeleton, 2 pairs of antennae and mouth parts called mandibles
• have head, thorax and abdomen, or cephalothorax + abdomen
• a tough shell called the carapace may cover the cephalothorax
• may have CaCO3 in exoskeleton to make hard shells
• antennae are used as sensory feelers or in some cases for filter feeding or as oars
• mandibles can be short heavy structures that bite and grind food
• mandibles can be bristles might be used for filter or detritus feeding
• needlelike mandibles are used to drink blood
• other appendages vary a lot but can include claws, legs, paddles, feathery feelers, powerful tails, etc

Question 23

what are centipedes and millipedes

Answer 23

• many legs
• long, worm like, many segments and legs
• around 3000 centipedes
• around 7500 millipedes
• live in moist areas

Question 24

what are centipedes

Answer 24

• carnivores, a pair of poisonous claes near the mouth are used to hunt
• eat arthropods. worms, frogs, small snakes, mice, etc
• biggest are around 26cm long
• 15-170 pairs of legs
• most segments have legs

Question 25

what are millipedes

Answer 25

• twice as many legs as centipedes
• 2 pairs of legs per segment
• eat dead plats
• hide and use chemicals for defense

Question 26

what are insects

Answer 26

• 900 000+ species
• vary greatly
• have a head, thorax, and abdomen, 3 pairs of legs
• typically have one pair of antennae, eyes, and 4 wings
• vary a lot in functioning

Question 27

how do insects feed

Answer 27

• 3 pairs of mouth parts including mandibles
• vary in use from cutting, chewing, to sucking
• some pairs have fused together
• saliva may have digestive enzymes or other chemical elements
• other structures like hairs on bees help collect food

Question 28

how do insects move

Answer 28

• 6 legs
• may have spines or hooks
• can be used to jump, hold prey, etc
• can fly, wings on thorax, big muscles along with mitochondria
• may have special blood supply to wings

Question 29

what are insect societies

Answer 29

• some form societies, ex ants, wasps, bees (social insects)
• can be between 6 individuals to 7 million or more
• division of labor is displayed with classes that have different forms
• the basic classes are: reproductive females, reproductive males, and workers
• the reproductive females are called queens and lay eggs, can be 10x larger than workers, have enlarged reproductive organs, usually only 1 but can have more
• the reproductive males fertilize eggs and usually die soon after
• the workers do all the other tasks, gathering food, defending the colony, building, etc
• in ants and termites they specialize to a task

Question 30

how do insects communicate

Answer 30

• sound, visual, chemical, others
• sound examples include chirps, cicada buzzes
• visual example include fire fly light
• chemical examples include pheromones that affect behavior or reproduction of the same species
• pheromones are crucial for insect societies they can be used to signal many things or change development of a queen or egg laying individual
• honey bees dance to signal:
  
  • the round dance indicates food has been found within 50m
  • the waggle dance indicates food has been found more than 50 m away
• many others

Question 31

how do arthropods fit into our world

Answer 31

• many roles in food chains
• pollination
• symbiosis with ants and acacia tree, cleaner shrimp, etc
• microscopic ticks cover our skin
• help or damage crops
• food
• provide chemicals
• damage life stock and crops
• mosquitoes and others are vectors for disease
• termites destroy structures