ArthropodsArthropods

ARTHROPODSARTHROPODS 1 million known species of 1 million known species of

arthropods. arthropods. May be up to 30 million May be up to 30 million

species in the world’s species in the world’s tropical rain forests. Two tropical rain forests. Two out of three animals living out of three animals living on earth are arthropods.on earth are arthropods.

Phylum ArthropodaPhylum Arthropoda Arthron- means joint Arthron- means joint pous- means footpous- means foot

Typical arthropod: an invertebrate Typical arthropod: an invertebrate with bilateral symmetry, a with bilateral symmetry, a coelom, an exoskeleton, jointed coelom, an exoskeleton, jointed appendages, an open circulatory appendages, an open circulatory system and complex social system and complex social behavior.behavior.

Arthropods include: Arthropods include: insects, centipeds, millipeds, insects, centipeds, millipeds, spiders, ticks, scorpions, mites, spiders, ticks, scorpions, mites, lobsters, shrimp, crabs, and lobsters, shrimp, crabs, and crayfish.crayfish.

Evolutionary success due Evolutionary success due to jointed appendages to jointed appendages and exoskeleton.and exoskeleton.

Jointed appendages: Jointed appendages: most recognizable most recognizable feature. Allow for more feature. Allow for more powerful movements powerful movements and allows appendages and allows appendages to be used for:to be used for:

1)walking,1)walking, 2)sensing2)sensing 3) feeding3) feeding 4) mating. 4) mating. ***Appendage may be a ***Appendage may be a

leg or an antenna.leg or an antenna.

ExoskeletonExoskeleton – – Hard, Hard, thick outer covering made of thick outer covering made of protein and chitin. It may be one protein and chitin. It may be one continuous covering or it is made continuous covering or it is made of separate plates held together of separate plates held together by hinges. by hinges.

Provides: protection and support Provides: protection and support for internal tissuesfor internal tissues protects against water lossprotects against water loss provides places for muscle provides places for muscle

attachmentattachment

Disadvantage:Disadvantage:Exoskeletons are Exoskeletons are heavy - some have heavy - some have adapted to their adapted to their habitats by developing habitats by developing thinner, lightweight thinner, lightweight exoskeleton. exoskeleton. However, this provides However, this provides less protection.less protection.

Molting – Molting – periodic periodic shedding of exoskeleton shedding of exoskeleton allows the animal to grow allows the animal to grow

larger; larger; 4 to 7 times in their life4 to 7 times in their life during molting animal is during molting animal is

vulnerable to predatorsvulnerable to predators

Process of Process of Molting: Molting: animal contracts muscles in animal contracts muscles in

the rear part of its body, the rear part of its body, forcing blood forward. forcing blood forward.

The forward part of the body The forward part of the body swells, causing the old swells, causing the old exoskeleton to split open. exoskeleton to split open.

The animal then wigglesThe animal then wiggles out.out.

SegmentationSegmentation Less segmented than worms; Less segmented than worms;

the body segments have the body segments have become fused into 1-3 body become fused into 1-3 body sections sections 1) HEAD1) HEAD 2) THORAX2) THORAX 3) ABDOMEN3) ABDOMEN

Some arthropods have Some arthropods have the head and thorax the head and thorax fused to form a fused to form a cephalothoraxcephalothorax

Efficient gas exchangeEfficient gas exchange Arthropods are generally Arthropods are generally

quick, active animals. They quick, active animals. They crawl, run, climb, dig, swim, crawl, run, climb, dig, swim, and fly. Some flies beat their and fly. Some flies beat their wings 1000 times per wings 1000 times per second. Oxygen delivery to second. Oxygen delivery to cells must be quick.cells must be quick.

3 Types of Respiratory Structures3 Types of Respiratory Structures

1. gills – aquatic (Ex. Crabs) 1. gills – aquatic (Ex. Crabs) large surface area enables a large large surface area enables a large

amount of blood-rich tissue to be amount of blood-rich tissue to be exposed to water containing exposed to water containing oxygen.oxygen.

2.2.tracheal tubes – land (most insects)tracheal tubes – land (most insects) most insectsmost insects branching network of hollow air branching network of hollow air

passages that carry air throughout passages that carry air throughout body; air enters and leaves through body; air enters and leaves through openings on the thorax and openings on the thorax and abdomen called abdomen called spiracles.spiracles.

3. book lungs – land3. book lungs – land SpidersSpiders are air filled, folded are air filled, folded membranes that membranes that

contain leaf-like plates contain leaf-like plates (looks like pages in a (looks like pages in a book) which increase the book) which increase the surface area of tissues surface area of tissues exposed to air.exposed to air.

                    

                                           

                                                               

Book Lungs

Arthropods have acute sensesArthropods have acute senses Movement, sound, or chemicals can Movement, sound, or chemicals can

be detected by antennae. Antenna be detected by antennae. Antenna are also used for communication, are also used for communication, detect pheromones. Example ants detect pheromones. Example ants use it for scent trails and for mating.use it for scent trails and for mating.

Acute vision – most have Acute vision – most have one pair of large compound one pair of large compound eyes and 3 to 8 simple eyes.eyes and 3 to 8 simple eyes. Simple eye – visual structure with Simple eye – visual structure with

only 1 lens, used for detecting only 1 lens, used for detecting light.light.

Side eyes: pick up movement

Middle front: sharp images, some color

Side front: judge distances

Compound eye – many lenses Compound eye – many lenses that register light from one area of that register light from one area of the total field of view; can detect the total field of view; can detect slight motion of prey, mates, or slight motion of prey, mates, or predators; can see colors, but predators; can see colors, but image is fuzzy.image is fuzzy.

SYSTEMSSYSTEMS Nervous system – well Nervous system – well

developed; consists of developed; consists of 1) ventral nerve cord1) ventral nerve cord 2) anterior brain2) anterior brain 3) several ganglia (nerve & 3) several ganglia (nerve &

tissue cells) tissue cells)

circulatory (yellow), digestive (green), nervous (blue) systems.

Open Circulatory system – one or more Open Circulatory system – one or more hearts; blood flows out of vessels, bathes hearts; blood flows out of vessels, bathes the tissue, returns to heart through open the tissue, returns to heart through open body spaces.body spaces.

Complex Digestive System Complex Digestive System 1) mouth – contain a variety of jaws called 1) mouth – contain a variety of jaws called

mandiblesmandibles; mouthparts are adapted for ; mouthparts are adapted for holding, chewing, sucking or biting, this holding, chewing, sucking or biting, this enables them to fit a variety of niches.enables them to fit a variety of niches.

     

                           

    

•Sand flies feed by drawing blood

•Butterflies and moths use a rolled-up sucking tube

Sponging tongue of housefly uses saliva to digest food

Most terrestrial arthropods Most terrestrial arthropods excrete wastes through excrete wastes through Malpighian tubulesMalpighian tubules. They are . They are located in the abdomen, attached located in the abdomen, attached to and empty into the intestineto and empty into the intestine

Muscular System – attached to Muscular System – attached to exoskeletonexoskeleton

How far can a flea jump?How far can a flea jump?

Reproductive System – most species Reproductive System – most species have male and females that have male and females that reproduce sexuallyreproduce sexually

Terrestrial arthropods – internal Terrestrial arthropods – internal

fertilizationfertilization

Aquatic arthropods - external Aquatic arthropods - external fertilizationfertilization

Some species are Some species are hermaphroditeshermaphrodites (animals w/both (animals w/both male and female organs).male and female organs).

Some species are asexual. Some species are asexual. Reproducing through a process Reproducing through a process called called parthenogenesisparthenogenesis (organism (organism develops from an unfertilized develops from an unfertilized egg).egg).

ECOLOGY OF ARTHROPODSECOLOGY OF ARTHROPODS

Found in a wide variety of habitats due to Found in a wide variety of habitats due to the variety of adaptations they have for the variety of adaptations they have for obtaining and digesting food. Some are obtaining and digesting food. Some are consumers and others are parasites consumers and others are parasites (some lay eggs on the larvae of other (some lay eggs on the larvae of other insects).insects).

Beneficial to humans Beneficial to humans

1) pollinate flowering trees and 1) pollinate flowering trees and crop plantscrop plants

2) wax2) wax

3) silk3) silk

4) provide alternatives (ladybird 4) provide alternatives (ladybird beetles) to chemical beetles) to chemical

5) control of other insects5) control of other insects

Research on arthropods has led to Research on arthropods has led to advances in the fields of genetics, advances in the fields of genetics, evolution, and biochemistry. From crab evolution, and biochemistry. From crab shells, scientists have made artificial skin, shells, scientists have made artificial skin, surgical sutures, and anti-fungal surgical sutures, and anti-fungal medication.medication.

But, they can also be detrimental to humans.But, they can also be detrimental to humans. 1) Spread diseases to plants and animals 1) Spread diseases to plants and animals

(West Nile, malaria, yellow fever, Lyme’s (West Nile, malaria, yellow fever, Lyme’s disease)disease)

2) Eat crops.2) Eat crops.