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Joint-Legged Animals 465/8 By: Amina Nur
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Joint-Legged Animals 465/8

Feb 24, 2016

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Joint-Legged Animals 465/8. By: Amina Nur. Animals With Exoskeletons (Phylum Arthropoda ). In terms of numbers, Arthropods dominate animal life 9 000 000 arthropods are estimated to be undiscovered All have segmented bodies, suggesting evolution from segmented Annelid Worms - PowerPoint PPT Presentation
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Page 1: Joint-Legged Animals 465/8

Joint-Legged Animals 465/8

By: Amina Nur

Page 2: Joint-Legged Animals 465/8

Animals With Exoskeletons(Phylum Arthropoda)

In terms of numbers, Arthropods dominate animal life

9 000 000 arthropods are estimated to be undiscovered

All have segmented bodies, suggesting evolution from segmented Annelid Worms

Segments become more specialized in higher Arthropods, nearly all segments differ in function

They developed exoskeletons, joint legs and a hemocoel (blood cavity)

Exoskeleton is a thick external covering composed of strong waterproof carbohydrate molecules called Chitin

Protects animal, resists desiccation (drying out) in non aquatic environments, allowing them on land

Rigidity prevents efficient locomotion

Evolved appendages and groups of muscles which evolved into joints increasing mobility

No longer needed coelom to provide body shape Reduced ability for gas exchanged. Aquatic

arthropods developed gills that took in O2 and expelled CO2

Many arthropods evolved Tracheae to carry O2 to body

Rigidity hindered growth, they shed exoskeleton when they grew and replaced them with a bigger one (adapted by moulting)

Circulatory system has a hemocoel Over time their bodies replaced body fluid with

blood which travelled through vessels and emitted into hemocoel

It bathed organs directly in an arrangement called Open Circulatory system

Developed sensory receptors: eyes and antennae

Page 3: Joint-Legged Animals 465/8

Segments of exoskeleton modified in different arthropod groups. Specialized regions, modified, joint appendages, and groups of muscles improved arthropod function and mobility.

Page 4: Joint-Legged Animals 465/8

Class Arachnida

Includes: Scorpions, spiders, mites and ticks

Body has 2 parts: head fusing to body segments forming cephalothorax

Posterior body segments (abdomen) contain most organs

Arachnids have 6 pairs of appendages – each for different functions:(1) To feed(2) Sense environment(3) The last 4 are used to walk

Reproduction: Male inserts sperm into small sac in the

female called the seminal receptacle where fertilization occurs

Life cycle: Miniature adults hatch from eggs and live

independently from the time they hatch Gas exchanges through book lungs

(highly folded membranes) in abdomen Silk glands in spiders’ abdomen produce

protein threads for spinning webs

Many spiders build webs with their silk, but some use their long threads to mate or protect young

Page 5: Joint-Legged Animals 465/8

Class Crustacea

40, 000 species 3 Regions make up body:

Head Thorax Abdomen

Exoskeleton forms thick carapace (covers head + other segments)

2 appendages, antennae, followed by the mandibles

Mandibles crush food and feed it to the mouth

Behind mandibles, a pair of millipedes – sense environment, search for food

Behind that, large claw like Chelipeds grab food and protect themselves from predators

Four legs follow the Chelipeds On the abdomen, 6 pairs of swimmerets

help crustacean swim

Pair of flat appendages (Uropod) lie on tail (Telson) behind posterior end of abdomen

These act as paddles, moving the animal backwards

They have many gills, connected to walking legs, which is protected by Carapace

Gils are feathered to increase gas exchange surface area

Gases in water diffuse into and out of the gills and travel through the circulatory system to body tissues

To increase diffusion through blood vessels of gills, swimmerets on telson beat and sweep water forward, under carapace and over the gills.

Males and females come together to copulate

Page 6: Joint-Legged Animals 465/8

Class Insecta

Numerous of all animals species + 1.5 million species Insect bodies are like those of a crustacean On their heads one antenna senses the

environment On the thorax, there are 3 pairs of legs Gas exchanged carried out through air sacs

and tubes (trachea) Adults of flying insects, usually have two pairs

of stiff membranous wings attached to the thorax

Flies have only one. In beetles, front wings form hardened wing covers

Separate sexes to produce egg and sperm Some insects undergo simple development,

hatching like miniature adults Winged insect undergo complex developments Body structure changes radically in process of

metamorphosis – change of shape and diet

Transform from worm-like larva maturing through each instar, or early stages into adults

Diet change minimizes the competition for food between larvae and adults

This increase species’ chances for survival

Page 7: Joint-Legged Animals 465/8

Class Diplopods and Chilopods

Diploids millipedes Millipede suggest the insect has thousands

of feet Members of this class only have about a

hundred pair of legs Number of segments in the body range

from 10 – 100 Each segment has 2 pairs of feet (Diplopod

means ‘double footed’) Chilopods are known as centipedes Like Diplopods, Chilopods only have about

10 – 100 pairs of legs Each segment contains only one pair

Chilopods:

Diplopods:

Page 8: Joint-Legged Animals 465/8

Joint-Legged AnimalsBy: Amina Nur

Biology sucks…we all know nobody was really listening…