ArthropodsArthropods

Tang Hiu Man(22) 6STang Hiu Man(22) 6S

ArthropodsTang Hiu Man (22) 6S

Kingdom Animalia

Arthropods節肢動物 Annelids Vertebrates

Crustaceans甲殼動物

Molluscs

Arachnids蜘蛛類動物

Myriapods多足動物 Insects

Introduction

An arthropod is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and jointed appendages （附屬肢體）

Largest group of invertebrate( ＞ 1 million species) Occupy ＞ 80% of all the animal species Largest number of species Has individuals occupying the greatest variety of h

abitats consists of repeated segments, each with a pair of

 appendages

Features

All consists of chitinous( 角質素的 ) exoskeleton (cuticle) and jointed legs, some may have wings (eg. Butterflies, dragonflies)

Consists of repeated segments, each with a pair of appendages

Internal organs are also built of repeated segments Highly versatile (enabled them to become the most

species-rich animals in most environment ) vision relies on various combinations of compound e

yes

1.Crustaceans( 甲殼 )Have biramous( 二肢 ) appendages

Shrimp crab

Barnacle 藤壺 water flea

2.Myriapods( 多足 )have many body segments, each bearing

one or two pairs of legs. 

centipede 蜈蚣 millipede

3.Arachnids( 蜘蛛類 )presence of chelicerae( 螫肢 ), appendage

s just above / in front of the mouth.

spider mite scorpion

4.Insects

with six thoracic legs

Butterfly bee beetle

dragonfly

Cuticle (chitinous exoskeleton)

Reduce water lost by evaporation Act as a protective layer against bacterial invasion & mec

hanical injury Provide a rigid framework to support the body on land The presence of joints between segments of legs allow

rapid locomotion to take place Provide large surface area for muscle attachment that

produces force for locomotion The thoracic( 胸的 ) cuticle with wings to make flight pos

sible With colour for camouflage( 保護色 )

Wings

They enable insects to fly so that:

a. Insects can get their food & escape from their enemies quickly, thus flight facilitates survival.

b. Insects can disperse themselves & thus reduce the problem of overcrowding.

Jointed Legs

Allow walking A pair of strong & muscular hind legs( 後腿 )

allow rapid hopping( 跳 ) for long distance during escaping from enemies or

catching preys

Small size

Reduce the competition for food & space

Reduce body weight to facilitate flight Insects can easily hide themselves in c

revices( 縫隙 )

Recent NewsRecent News

吃蟲救地球吃蟲救地球

http://www.babynet.com.hk/content/%E5%90%83%E8%9F%B2%E6%95%91%E5%9C%B0%E7http://www.babynet.com.hk/content/%E5%90%83%E8%9F%B2%E6%95%91%E5%9C%B0%E7%90%83-%E5%A4%A7%E5%AE%B6%E9%83%BD%E4%BE%86%E5%90%83%E8%9F%B2%%90%83-%E5%A4%A7%E5%AE%B6%E9%83%BD%E4%BE%86%E5%90%83%E8%9F%B2%E6%95%91%E5%9C%B0%E7%90%83%E5%9C%96%E7%89%87E6%95%91%E5%9C%B0%E7%90%83%E5%9C%96%E7%89%87

Modification of Jointed Modification of Jointed AppendagesAppendages

Jointed appendages Jointed appendages can be modifiedcan be modified Can Can become many different structuresbecome many different structures for for dd

ifferent functionsifferent functions eg. appendages on eg. appendages on headhead→→ antennae(antennae( 觸角觸角 ), palps(), palps( 觸鬚觸鬚 ) for sensory fu) for sensory fu

nctionsnctions Appendages on Appendages on thorax & abdomen(thorax & abdomen( 腹腹 ))→→ walking, swimming, transferring spermswalking, swimming, transferring sperms

Breathing

Aquatic(crustaceans)

terrestrial

gillTracheal system

(insects & myriapods)

Book lungs 書肺(arachnids)

Gill

Book lung

Tracheal system

ReproductionReproduction

terrestrial : internal fertilizationterrestrial : internal fertilization Aquatic : external fertilization except scoAquatic : external fertilization except sco

rpion (lay eggs)rpion (lay eggs)

A few:A few: have organs of both sexes (eg. barnacles)have organs of both sexes (eg. barnacles) Parthenogenesis(Parthenogenesis( 單性生殖單性生殖 )(reversible))(reversible)

ReferenceReference

• http://en.wikipedia.org/wiki/Arthropod#http://en.wikipedia.org/wiki/Arthropod#Reproduction_and_developmentReproduction_and_development

• http://http://www.google.com.hkwww.google.com.hk/images/images • Advanced-level Biology for Hong KongAdvanced-level Biology for Hong Kong• AL Biology Book 3 Ecology AL Biology Book 3 Ecology

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