current problems of pakistan
Characteristics of the Phylum
Arthropoda
The segmented bodies are arranged into regions, called tagmata (e.g., head, thorax, abdomen). The paired appendages (e.g., legs, antennae) are jointed.
They posses a chitinous exoskeletion that must be shed during growth.
They have bilateral symmetry.
The nervous system is dorsal (belly) and the circulatory system is open and ventral (back).
Arthropod Groups (taxa)
The arthropods are divided into two large groups that exist today:
The Chelicerates and The Mandibulates
Exoskeletons
• Strength and impermeability • Solves difficulties of life on land:
– desiccation
– need for structural support • BUT: must molt to grow (ecdysis)
Grasshopper molting
Phylum Arthropoda “arthropods”
• > 1 million spp., most of them insects (most of those, beetles) • Most diverse, widely distributed & abundant of all animal phyla
Arthropod innovations
• Exoskeleton of chitin
* Hard & strong
* Impermeable to water
* Molting
• Segmentation
• Jointed appendages
Millipede
* “jointed feet”
• efficient walking & swimming * wings in most
• one of 2 phyla to fly
Monarch butterfly metamorphosis
Arthropod limbs
• Two types, relating to feeding mode
* Uniramous, single branch
* Biramous, two branches, sometimes gnathobasic
(like in Limulus and the trilobites)
* Some doubt cast recently on this simple scheme!
Trilobite gnathobasic limbs
Further arthropod anatomy
• Extensive cephalization (sense organs & mouth parts)
• Well developed
•
sense organs:
* “Taste”
* Sight many with complex, compound eyes
Segment fusion
Abdomen
Antennae
(sensory reception) Head Thorax
Swimming appendages Walking legs
Pincer (defense) Mouthparts (feeding)
Some Arthropod groups
Trilobite (extinct group)
Limulus
Millipedes and centipedes
Class Arachnida
“Spiders, mites, ticks, scorpions”
50 µm
• 6 pairs of appendages
• including 4 pairs of
Arthropoda
The segmented bodies are arranged into regions, called tagmata (e.g., head, thorax, abdomen). The paired appendages (e.g., legs, antennae) are jointed.
They posses a chitinous exoskeletion that must be shed during growth.
They have bilateral symmetry.
The nervous system is dorsal (belly) and the circulatory system is open and ventral (back).
Arthropod Groups (taxa)
The arthropods are divided into two large groups that exist today:
The Chelicerates and The Mandibulates
Exoskeletons
• Strength and impermeability • Solves difficulties of life on land:
– desiccation
– need for structural support • BUT: must molt to grow (ecdysis)
Grasshopper molting
Phylum Arthropoda “arthropods”
• > 1 million spp., most of them insects (most of those, beetles) • Most diverse, widely distributed & abundant of all animal phyla
Arthropod innovations
• Exoskeleton of chitin
* Hard & strong
* Impermeable to water
* Molting
• Segmentation
• Jointed appendages
Millipede
* “jointed feet”
• efficient walking & swimming * wings in most
• one of 2 phyla to fly
Monarch butterfly metamorphosis
Arthropod limbs
• Two types, relating to feeding mode
* Uniramous, single branch
* Biramous, two branches, sometimes gnathobasic
(like in Limulus and the trilobites)
* Some doubt cast recently on this simple scheme!
Trilobite gnathobasic limbs
Further arthropod anatomy
• Extensive cephalization (sense organs & mouth parts)
• Well developed
•
sense organs:
* “Taste”
* Sight many with complex, compound eyes
Segment fusion
Abdomen
Antennae
(sensory reception) Head Thorax
Swimming appendages Walking legs
Pincer (defense) Mouthparts (feeding)
Some Arthropod groups
Trilobite (extinct group)
Limulus
Millipedes and centipedes
Class Arachnida
“Spiders, mites, ticks, scorpions”
50 µm
• 6 pairs of appendages
• including 4 pairs of