Arthropods

What are the 4 main classes of arthropods?

chelicerata, crsutacea, hexapoda, myriapoda

What animals belong to chelicerata?

spiders, mites, ticks, scorpions, daddy long-legs, and horseshoe crabs

What are the characteristics of chelicerata?

mouthparts are chelicerae (pincers or fangs)

What animals belong to crustacea?

lobsters, crabs, shrimps, isopods, barnacles

What are the characteristics of crustacea?

• mouthparts are mandibles

• appendages are biramous

• the head has two pairs of antennae

What does biramous mean?

dividing to form two branches

What are some animals that belong to hexapoda?

insects (beetles, bees, flies, fleas, true bugs, grasshoppers, butterflies, and termites), springtails

What are characteristics of hexapods?

• mouthparts are mandibles

• the body consists of 3 regions

  • a head with a pair of antennae

  • a thorax

  • an abdomen

• appendages are uniramous

What are some animals that belong to myriapoda?

centipedes, millipedes

What are the characteristics of myriapods?

• mouthparts are mandibles

• body consists of a head with one pair of antennae and numerous segments

• each segment is pair with uniramous appendages

What are the largest class of arthropods?

Hexapods (insects)

What is the largest group of insects?

Beetles 

What happens to the morphology of the segments as development proceeds?

segments sometimes fuse together

tagmatization

process of fusing in arthropods

Grasshoppers and most other insects are _____

ectysozoa (they molt)

Arthropod bodies are ____

segmented

What are the two different ways arthropods can be segemented?

in some, the segments are myriapods in others, they are grouped into tagmata

myriapods

segments that look alike

tagmata

segments that are specialized into functional groups (like head, thorax, and abdomen in insects)

All arthropods have distinct _____

heads

cephalothorax/prosoma

fused head and thorax

prosoma is used in chelicerates and crustaceans

What makes up an arthropod exoskeleton?

chitin and proteins

What are the functions and advantages of the exoskeleton?

• muscle attachment and antagonism

• body support

• protection

• prevents water loss

What are the disadvantages to the exoskeleton?

• limits body size

• restricts movement

• ecdysis increases predation risk

Why are aquatic arthropods generally larger in size compared to the terrestrial ones?

because they water more easily supports the weight of the body

All arthropods have _____ appendages which can be modified into _____, _____, and ______

jointed, antennae, mouthparts, legs

Arthropod appendages can be extended and retracted which allows for what?

better movement

joints provide ____ for leverage of _____

fulcrum, movement

Joints use a ___ force to generate a ___ movement

small, large

nervous system

double chain of segmented ganglia on the ventral surface and anterior brain

What carries out most bodily functions in absence of the brain?

Ganglia

What animals have compound eyes?

insects, crustaceans, and some centipedes

Compound eyes are composed of _____

ommatidia

Ommatidia

independent visual units that compose the compound eye which each have their own lens

What animal has simple eyes?

spiders

What is another name for simple eyes?

ocelli

How do ocelli work?

detect light and dark which helps stabilize insects during flight

What animals have both simple and compound eyes?

dragonflies, locust

What type of circulatory system do arthropods have and what is special about it?

open circulatory system, it does not oxygenate the body

Heart

• muscular vessel in dorsal thorax and abdomen

• pumps blood anteriorly and into the coelom

Marine arthropods have ____ used for _____ also

gills, excretion

What makes up the respiratory system in terrestrial insects?

the tracheal system and spiracles

What does the gastric ceca do?

increases surface area for digestion

What are spiracles?

they can be closed and works to prevent water loss which is a key land adaptation

What happens from the tracheae to the tracheoles?

gas exchange across plasma membrane (pulsing brings O2 in and out)

What causes a severe restriction on body size?

all tissues must be near a respiratory passage in order for oxygen to diffuse 

Describe digestion

complete gut with extracellular digestion

What is a theory for why insect fossils were much larger?

there was more available O2 to diffuse, allowing insects to be larger

What does the excretory system consist of in terrestrial arthropods?

Malpighian tubules

What are some examples of terrestrial arthropods who have malpighian tubules?

terrestrial insects, myriapods, and arachnids

What doe the malpighian tubules do?

eliminate nitrogenous wastes as concentrated uric acid or guanine, emptied into hindgut and eliminated

What two things are reabsorbed in the hindgut?

water and salts

Describe reproduction in arthropods

• gonochoric

• internal fertilization

• lay eggs

external fertilization occurs in some of what type of arthropods?

some marine arthropods

What are some animals under subphylum chelicerata?

spiders, ticks, mites, scorpions, and daddy long-legs

Chelicerates are largely ____ and ______

terrestrial and cernivorous

Chelicerae

• come in pairs

• anterior appendages that act as fangs or pincers

what do all spiders have in common in terms of venom glands?

they all have venom glands with channels through their chelicerae

tagmata

functional unit of an arthropod's body, such as the head, thorax, and abdomen of an insect

How many tagmata do chelicerates have?

2

Prosoma

fusion of head and thorax, located on the anterior end and bears all appendages

What appendages are attached to the prosoma?

• 1 pair of chelicerae

• 1 pair of pedipalps

• 4 pairs of walking legs

Posterior opisthosoma

contains the reproductive organs and other organs

pedipalps are _____ to chelicerae

posterior

pedipalps

resemble legs but have one less segment; used as copular organs, pincers/claws, or sensors

Book lungs

type of respiration organ used for atmospheric gas exchange present in some arachnids such as scorpions

True or False: Chelicerates cannot consume solid food

True

How does digestion work in chelicerates?

inject/expel digestive enzymes into/onto prey and suck out juices

What are some organisms that belong to class crustacea?

crabs, shrimps, lobsters, barnacles

Characteristics of Crustacea

• primarily marine

• important food source for humans and marine ecosystems