Ch 28 Outline: Arthropods

What animals are in the phylum Arthropods?

a. Bumble beesb. Spidersc. Octopusd. Lobsterse. Millepedes

Answer all that apply by holding up more than one card.

Answer: A, B, D, E

There are 4 Subphyla of Arthropods List the three subphyla that are

still living. If you can’t remember the names of the subphyla, write down the representative species that are in each group.

Answer: chelicerates, crustaceans, uniraminans

Which subphyla representatives are are matched to the proper names?

A. uniramians – prawns B. chelicerates – spiders C. crustaceans – cockroaches D. triobites – millepedes

4 Subphyla: Trilobites (now extinct) Chelicerates – spiders, ticks, mites,

scorpions, horseshoe crabs Crustaceans – crabs, shrimp,

lobster Uniramians – centipedes, bees,

moths, grasshoppers, flies, bettles

Evolution: Which insects have common ancestors with modern annelids (segmented worms)

A. insects B. Centipedes C. millipedes D. crustaceans E. spiders (chelicerates) (hold up multiple letters if more

than one answer apply)Answer: A, B, C

Evolution

Insects, centipedes and millipedes seem to have common ancestors with modern annelids

Crustaceans and spiders evolved from different ancestors

What is special about the Velvet worm?

A. it is a living fossil B. it is extinct, but has the characteristics of

arthropods C. It seems to be a “transition” organism

between the annelids and the arthropods D. It has larvae that are the same as insect

larvae E. It makes a substance that resembles

velvet

Answer: C

The Velvet worm Placed in its own

phylum (along with others like it)

Has characteristics of both annelids and arthropods

The First Arthropods?

What Evolutionary trends are shown within the Arthropods?

A. early arthropods have a sac body plan; later arthropods have tube-within-a-tube

B. early arthropods have bilateral symmetry; later arthropods have radial symmetry

C. early arthropods have many smaller body segments; later arthropods have fewer but larger body segments

D. early arthropods do not fly; later arthropods do E. early arthropods have many unspecialized

appendages, later arthropods have fewer, more specialized appendages

Answer: C and E

Arthropod Evolutionary Trends

Far fewer body segments (segments in embryo fuse into larger ones)

Appendages become more and more specialized

What are the names of the three main body segments of an insect?

A. head, legs, wings B. appendages, thorax, exoskeleton C. head, thorax, abdomen D. anterior, posterior, ventral E. dorsal, ventral, posterior

Answer: c

Structure – head, thorax and abdomen

List at least two characteristics that unify the phylum Arthropoda.

(Answer on next slide)

Arthropods – Characteristics that Unify

Jointed appendages– antennae,claws, legs, wings,flippers, etc.

Exoskeleton Segmented body Open circulatorysystems

What is the main molecule in exoskeletons, and what type of molecule is it?

A. cellulose, a complex carbohydrate B. glucose, a simple carbohydrate C. chitin, a complex carbohydrate D. starch a complex carbohydrate E. glycogen, a complex carbohydrate

Answer: C

What is a major DISADVANTAGE to having an exoskeleton rather than an endoskeleton?

A. it is not as strong as an endoskeleton B. it cannot heal like an endoskeleton can

(if it breaks) C. it is more vulnerable to breaking since it

is on the outside of the body D. it does not grow larger like an

endoskeleton can E. it is not as flexible as an endoskeleton is.

Answer: D

Exoskeletons Made of chitin Some

leathery/flexible Some waterproof Must be molted

for the animal to grow

There are 4 different structures that insects use to breathe. List at least 2 of them

(Answer on next slide)

Respiration

Arthropods have 4 basic structures for respiration:

Gills, Book Gills, book lungs and Tracheal tubes

Respiration - Arthropods

Aquatic arthropods (crabs and shrimp):

GILLS

Book Gills

Unique to horseshoe crabs

Tissues are layered

Book Lungs – Layered Tissues

Unique to Chelicerates

Book lungs

How does the air come into the insect if it is “Breathing” using tracheal tubes?

A. the air moves through the tubes when the muscles move the abdominal cavity

B. there is an area inside the expands and contracts like our diaphragm – this draws the air in

C. they have an incurrent siphon that pulls the air through

D. they use their wings to “fan” the air in

Answer: A

What are “spiracles”? A. the sensory receptors on the ends of

antennae B. The structures that are used for hearing for

insects C. the structures that are used to spin webs in

spiders D. the holes that allow air into the tracheal

tubes E. the barbs on the sides of some insects legs

for extra traction.

Answer: D

Tracheal Tubes

Branching tubes throughout the tissues

Shrink and contract when insect’s muscles move

Causes air to pump in and out of tissues

Attached to spiracles (holes on outside of body)

Tracheal Tubes

Feeding

What can insects eat? A. plants B. animals C. rotting organic matter D. fungi (mushrooms) E. bacteria

Answer: ALL of the above!

Modified appendages enable different arthropods to eat almost anything

The Difference (s) between an open and closed circulatory system is (are):

a. Closed systems have a heart (pump); open systems do not.

b. Closed systems have blood vessels; open systems do not.

c. Closed systems do not have sinuses (pools of blood for nutrient exchange); open systems do.

d. Closed systems are more efficient at nutrient and gas exchange; open systems are less efficient.

e. Humans have closed circulatory systems; arthropods have open systemsAnswer: C, D , E

Internal Transport

OPEN circulatory system with a well-developed heart (limits their size!!)

Heart pumps blood through blood vessels to sinuses where gas and nutrient exchange occurs with the tissue

Blood re-collects in large cavity surrounding heart and then enters heart to be pumped again

Open vs. Closed Circulatory Systems

Open vs Closed Circulatory Systems

How do Arthropods get rid of their SOLID wastes?

A. the solid waste exits back through their mouths

B. The solid wastes exit through their anus C. The solid wastes exit through their

spiracles D. The solid wastes exit through their

Malpigian tubules E. The solid wastes exit through their

sinuses

Answer: B

How do Arthropods get rid of their nitrogenous wastes?

A. the N2 wastes are concentrated by their Malpigian tubules

B. the N2 wastes are excreted through their anus

C. the N2 wastes are excreted through their spiracles

D. The N2 wastes are concentrated by their tracheal tubes

E. The N2 wastes are excreted through their gills

Answer: A, B, E

Excretion Solid waste exits through anus

Insects and spiders remove nitrogenous wastes with Malpighian tubules that are in the blood sinuses

Nitrogenous wastes are concentrated by tubules and added to solid waste for excretion.

Where (in their bodies) do Arthropods have structures to get rid of nitrogenous waste

structures?

A. their head B. their abdomen C. the base of their legs D. their tracheal tubes E. the ends of their antennae

Answer: A, B, C

Some terrestrial arthropods may also have excretory glands on base of legs.

Some arthropod have these glands instead of Malpighian tubules

Aquatic Arthropod Excretion

Excrete metabolic wastes through gills.

Lobsters also have a pair of green glands on their head that eliminate nitrogenous wastes!

(green gland)

How are Arthropods’ nervous systems different than humans?

A. We have a brain, they only have ganglia B. Our brain controls all our body except for

reflexes; their brain controls some but not all of their functions

C. We have a nerve cord; they do not have a nerve cord

D. our nerve cord is on our dorsal surface; theirs is on their ventral surface

E. Our NS is higher functioning on all levels than their nervous systems

Answer: B, & D

Response –well developed NS

Have brains in head that act as main coordinator, and ganglia in each segment that coordinate movement in that segment.

Brain and ganglia are connected by a ventral nerve cord

How do compound eyes differ from Human eyes?

a. Compound eyes do not have the ability to focus an image as well as our eyes can

b. Compound eyes do not see colorc. Compound eyes can focus much better

than our eyes because they have SO many lenses to work with. Our eyes only have one lens.

d. Compound eyes see motion much better than our eyes can.

e. Compound eyes produce larger images than our eyes

Answer: A, D

Sense organs

Have simple organs – statocysts and chemoreceptors

Most also have more complicated organs

Compound eyes are common

> 2000 separate lenses – excellent at detecting colour and movement (better that we can!)

Most can detect UV light

Where do Arthropods have taste buds?

a. Tongueb. Mouth partsc. Legsd. Abdomene. antennae

Answer: B, C, E

Crustaceans and insects have a good sense of taste

“Taste-buds” located on mouthparts, legs and antenna

Also have hairs that detect motion very well

How are insect ears different than human ears?

a. Human ears can hear much higher frequencies than insect ears

b. Human ears hear much lower frequencies than insect ears

c. Human ears have “ear drums” that are inside the head and much more protected than the “ear drums” of insects.

d. Human ears are much better at detecting sound than insect ears

e. Human ears are not as good as insect ears at detecting sound at normal ranges.

Answer: C

Where are the “ear drums” (tympanic membranes) on a grasshopper?

a. On their headsb. On their thorax under their wingsc. On their abdomen behind their legsd. On their abdomen at the very ende. On their antennae

Answer: c

Many insects have ears that hear frequencies higher than we can

Eardrums are in different places – eg. Grasshopper have eardrums behind their legs

How do insects protect themselves from predators?

a. They sting or bite or pinchb. They are poisonousc. They can drop an appendage (sacrifice a

limb) and run awayd. They can camouflage themselvese. They mimic other animals that are

poisonous

Answer: All of the above!

Protection Exoskeleton and good NS help Some sting, some bite, some pinch,

some are poisonous Some crabs drop a claw that continues

to move while they escape Some have camouflage Some mimic other animals that are

poisonous

Bee Stinging

Camouflage

mandibles

Mimicry

Biting

Mimicry

How do insects move their bodies?

a. They use jet propulsion like octopi or squid. On land they use their spiracles and tracheal tubes to move air instead of water.

b. They have cilia that move them through the grass or the water

c. They swim in the water d. They use muscles to move their

exoskeletons similar to how humans use muscle to move their endoskeletons

e. They have special tissue that moves their exoskeleton from the outside.

Answer: D

Movement Move with

muscles coordinated by NS

Muscles use exoskeleton as we use endoskeleton to move

What is the most common form of reproduction for arthropods?

a. External fertilizationb. Internal fertilizationc. Spore formationd. Egg productione. Internal development

Answer: B, D

Reproduction Most is internal

fertilization via special male organ

Spiders and some crustaceans leave a package of sperm for the female to pick up

How does an arthropod remove its exoskeleton when it needs to molt?

a. The exoskeleton will crack when the arthropod’s body becomes too large

b. The arthropods have a special internal appendage that can break open the endoskeleton from the inside.

c. The epidermal layer digests the inner exoskeleton layer to re-cycle the chitin

d. The arthropod must find a sharp object to scratch against to weaken the endoskeleton until it break through

Answer: C

Growing Requires MOLTING

Coordinated by hormones

1. The epidermal layer digests the inner exoskeleton layer to re-cycle the chitin

2. Arthropod body excretes a new exoskeleton (inside the old one)

3. Animal cracks the old exoskeleton and crawls out

4. May eat the old exoskeleton

5. Animal stretches the new exoskeleton to larger size (is done by pumping extra water into the body in aquatic arthropods)

New, larger exoskeleton will then harden

Grasshopper eating exoskeleton

Metamorphosis – A Drastic Change!

Insects demonstrate 2 forms of metamorphosis – complete and incomplete

Incomplete metamorphosis:

a. Insects enter the pupae stage but emerge without making the complete change in

Incomplete Metamorphosis

grasshoppers, mites, and crustaceans

the egg hatches into an immature animal that looks like the adult but lacks sex organs and other structures such as wings

Complete Metamorphosis Bees, moths,

beetles 4 stages:

1. Eggs

1. Eggs

2. Larvae – hatch from eggs. Look different from adult Grow bigger and molt several times.

Hang upside downIn “j” the day beforeIt turns into a pupa

3. Pupa – the last molt of a larva

Often has a protective coating

Body completely changes and rearranges. Old parts are digested to recycling the materials

just about ready to emerge

4. Adult – emerges from the pupal coccoon.

Even the animals behaviour will be different than the larval stage

Hormones, Molting and Metamorphosis

Molting hormone interacts with other hormones such as “juvenile” hormone

When juvenile hormone is high, the animal continues to molt into the larval stage. Each molt causes the animal to produce less hormone

At a critical lower level of juvenile hormone, the animal will molt into the pupa

When juvenile hormone is completely gone from the system, the pupa molts into the adult

Some plants use chemicals that mimic insect juvenile or molting hormone as a defence mechanism

Insecticides will also do this