Transcript Arthropods - walker2014

Arthropods
Chapter 28
Animal Classification
Invertebrates
Sponges
Cnidarians
Worms
Mollusks
Arthropods
Echinoderms
-Class Arachnida
-Class Crustacea
-Class Insecta
Animals
(cold-blooded)
Fishes
Amphibians
Reptiles
Endotherms
Birds
Mammals
Ectotherms
Vertebrates
(warm-blooded)
28-1: Characteristics of
Arthropods
Characteristics

Arthropod comes from the Greek words



“arthron” – joint
“pod” – foot
Typical arthropods:




Segmented
Coelomate
Bilateral symmetry
Exoskeleton
Characteristics

Appendages – any structure (a leg or an
antenna) that grows out of the body of an
animal
Why Arthropods Must Molt



Exoskeletons cannot
grow, so they must be
shed periodically
Molting – shedding the
old exoskeleton
Before an arthropod
molts, a new, soft
exoskeleton formed
beneath the old one
Cicada
Segmentation in Arthropods


Arthropods do not have as many segments
as segmented worms
In most groups, arthropods are consisted of
three segments



Head
Thorax
Abdomen
Segmentation in Arthropods

Some arthropods have two sections


Cephalothorax – A fused head and thorax
Abdomen
Arthropods Have Acute Senses


Movement, sound, and chemicals can be
detected with great sensitivity by antennae
Antennae are also used for sound and odor
communication; can detect pheromones
Atlas moth
Arthropods Have Acute Senses



Pheromones – chemical odor signals given
off by animals
Some pheromones are used as scent trails
(example: the group-feeding behavior of ants)
Many pheromones are important in the
mating behavior of arthropods
Arthropods Have Acute Senses

Most arthropods have one pair of large
compound eyes and three to eight simple
eyes

A simple eye is a visual structure with only one
lens that is used for detecting light
Arthropods Have Acute Senses


A compound eye is a visual structure with many
lenses
Compound eyes can detect the movements of
prey, mates, or predators, and can also detect
colors
Arthropods Have Other Complex Body
Systems

Arthropods have open circulatory systems
and complete digestive systems

Mouth, stomach, intestine, and anus
Arthropods Have Other Complex Body
Systems


Mandibles – the mouthparts of most
arthropod groups include one pair of jaws
The mandibles are adapted for holding,
chewing, sucking, or biting
Arthropods Reproduce Sexually


Some species (bees,
ants, and wasps)
exhibit parthenogenesis
– a form of asexual
reproduction in which a
new individual develops
from an unfertilized egg
In bees, drones are
developed from
unfertilized eggs
28-2: Diversity of Arthropods
Diversity of All Animals
About 85% of all known
animals are arthropods
Additional information
http://evolution.berkeley.edu/evolibrary/article/_0_0/arthropods_intro_05
Arachnids



Spiders, scorpions, mites, and ticks belong to
the class Arachnida
Spiders are the largest group of arachnids
An arachnid has a cephalothorax and an
abdomen with six pairs of jointed
appendages
Arachnids

Chelicerae [kuh-lis-er-uh] – the first pair of
appendages located near the mouth
(modified pinchers or fangs)

Pincers are used to hold food, and fangs inject
prey with poison
Arachnids



Pedipalps – the second pair of appendages
that is adapted for handling food and for
sensing
In male spiders, pedipalps are used to carry
sperm during reproduction
The four remaining appendages are adapted
as legs
Arachnids – Black Widow
Crustaceans


Class Crustacea include crabs, lobsters,
shrimps, crayfishes, pill bugs, and barnacles
Most crustaceans are aquatic and exchange
gases over gills
Crustaceans – Red Crab Mating
Crustaceans – Red Crab Offspring
Centipedes and Millipedes



Centipedes and millipedes have tracheal
tubes for gas exchange
Centipedes are carnivorous and eat soil
arthropods, snails, slugs, and worms
A millipede eats mostly plants and dead
material on damp forest floors
Insects


Class Insecta is the largest group of
arthropods
Insects have three body segments and six
legs
Insects – Giant Asian Hornets (Invasive
Species) vs. European Honey Bees
Insects – Giant Asian Hornets (Invasive
Species) vs. Japanese Honey Bees
Insects – Botfly
Metamorphosis


Metamorphosis – the series of changes, controlled
by chemical-substances in the animal
Two types of metamorphosis:

1. Complete metamorphosis consists of four stages:




Egg
Larva – the free-living, wormlike stage of an insect
Pupa – a period of reorganization in which the tissues and
organs of the larva are broken down and replaced by adult
tissues
Adult
Metamorphosis

Examples: ants, beetles, flies, and wasps
Metamorphosis

2. Incomplete metamorphosis – insects go
through only three stages of development





Egg
Nymph – hatches from an egg, has the same general
appearances the adult but is smaller
Adult
With each molt, it begins to resemble the
adult more
Grasshoppers and cockroaches undergo
incomplete metamorphosis

Picture of incomplete metamorphosis
Collecting Arthropods


1. Pitfall Traps
2. Flying Traps
Pitfall Trap






Cup
Water
Soap
Paper plate
Sticks
Labels
Flying Trap




Water bottles
Scissors
Twine or yarn
Labels