phylum arthropoda (SPIDERS, CRUSTACEANS, INSECTS)
• Artho for "joint" and poda for "foot". • Constitute 90% of the animal kingdom.
• Most numerous of all living organisms. • One million species (at least).
TYPES
INSECTS - ants, beetles, butterfles, dragonflies, flies, grasshoppers, praying mantis
ARACHNIDS - ticks, spiders, scorpions
CRUSTACEANS - barnacles, shrimp, crabs, crayfish, krill, lobsters
ONYCHOPHORANS - velvet worms
DIPLOPODS - millipedes
CHILOPODS - centipedes
SYMMETRY
Bilateral.
REPRODUCTION
Internal sexual reproduction (for the most part). Some reproduce by external fertilization. Some (barnacles are hermaphroditic). Most lay eggs. Others, like scorpions, are viviparous (producing live young after the eggs have hatched inside the female).
BODY PLAN
Arthropods are segmented, invertebrates with coelomate body cavities and exoskeletons with jointed appendages that enable them to move in many complex ways; Antennae, head, thorax, and abdomen in insects; cephalothorax (merged head and thorax) and abdomen in arachnids. The exoskeleton, jointed appendages, and segmentation are important keys to these arthropods' success. Simple brain. Great set of sense organs.
EXOSKELETON COMPOSITION & FUNCTION
The arthropod exoskeleton is made of chitlin (nitrogen containing polysaccharide). The exoskeleton protects and supports the internal organs and appendages of the arthropod but still provides muscle attachment. Some parts of the exoskeleton may be hard while others may be thin and flexible in order to provide for more movable joints between body segments and within appendages. Yet, exoskeletons have their limits with regard to how strong they can be. IF they got to be too big, then they would ironically crush and kill the very organisms that they were supposed to protect. Many arthropods shed their exoskeleton in a process called molting as they grow.
CIRCULATORY SYSTEM
Open circulatory system. Blood (or hemolymph) flows freely around the body cavity. Dorsal vessel (heart) is the main structure in arthropod's circulatory system. And, even though most arthropods do not rely on their circulatory systems to deliver oxygen, they do rely on their circulatory systems to transport nutrients and remove wastes.
GAS EXCHANGE
Arthropods have a special structure for gas exchange. Spiracles at the body surface open into tiny air tubes or tracheae. The tracheoles carry gas to all cells. Furthermore, arthropods obtain oxygen by using one of three structures––gills, book lungs, or tracheal tubes. Most aquatic arthropods (crayfish) have gills. Most terrestrial arthropods (beetles) have a system of branching tubes called tracheal tubes, which branch into smaller and smaller tubules, which carry oxygen throughout the body. Finally, some arthropods, including spiders, have book lungs, or saclike pockets with highly folded walls for respiration.This increased surface area of the lungs allows for an efficient exchange of gases. Both trachea and book lungs open to the outside of the body of some arthropods in opening called spiracles.
METAMORPHOSIS
Metamorphosis is a process where the body shape changes as the insect grows.
Complete Metamorphosis has four stages: egg, larva, pupa, adult (Caterpillars into butterflies; maggots into flies). The entire body shape is changed.
Incomplete Metamorphosis has three stages: egg, nymph, adult (grasshoppers and praying mantis). The nymph is wingless but closely resembles the mature adult. So,
the entire body shaped hasn't changed that much since the egg hatched.
WHY ARE ARTHROPODS THE MOST HEAVILY REPRESENTED ANIMAL GROUP ON THE PLANET?
This phylum is probably, in my opinion, the most important because arthropods take care of the planet in so many ways, and without their presence, multicellular life would vanish, as many arthropods are in the lower or bottom sections of many food chains. They also: help in nutrient recycling, supply food for other phylums, and are pollinators of flowering plants, which is imperative for their reproduction. Others acts as forms of bio-augmentation (spiders and ladybugs consuming deleterious aphids, for example). Their contributions are endless and they have a great impact on the economy. All life on Earth needs these arthropods: all one million species of them (at least).
• Most numerous of all living organisms. • One million species (at least).
TYPES
INSECTS - ants, beetles, butterfles, dragonflies, flies, grasshoppers, praying mantis
ARACHNIDS - ticks, spiders, scorpions
CRUSTACEANS - barnacles, shrimp, crabs, crayfish, krill, lobsters
ONYCHOPHORANS - velvet worms
DIPLOPODS - millipedes
CHILOPODS - centipedes
SYMMETRY
Bilateral.
REPRODUCTION
Internal sexual reproduction (for the most part). Some reproduce by external fertilization. Some (barnacles are hermaphroditic). Most lay eggs. Others, like scorpions, are viviparous (producing live young after the eggs have hatched inside the female).
BODY PLAN
Arthropods are segmented, invertebrates with coelomate body cavities and exoskeletons with jointed appendages that enable them to move in many complex ways; Antennae, head, thorax, and abdomen in insects; cephalothorax (merged head and thorax) and abdomen in arachnids. The exoskeleton, jointed appendages, and segmentation are important keys to these arthropods' success. Simple brain. Great set of sense organs.
EXOSKELETON COMPOSITION & FUNCTION
The arthropod exoskeleton is made of chitlin (nitrogen containing polysaccharide). The exoskeleton protects and supports the internal organs and appendages of the arthropod but still provides muscle attachment. Some parts of the exoskeleton may be hard while others may be thin and flexible in order to provide for more movable joints between body segments and within appendages. Yet, exoskeletons have their limits with regard to how strong they can be. IF they got to be too big, then they would ironically crush and kill the very organisms that they were supposed to protect. Many arthropods shed their exoskeleton in a process called molting as they grow.
CIRCULATORY SYSTEM
Open circulatory system. Blood (or hemolymph) flows freely around the body cavity. Dorsal vessel (heart) is the main structure in arthropod's circulatory system. And, even though most arthropods do not rely on their circulatory systems to deliver oxygen, they do rely on their circulatory systems to transport nutrients and remove wastes.
GAS EXCHANGE
Arthropods have a special structure for gas exchange. Spiracles at the body surface open into tiny air tubes or tracheae. The tracheoles carry gas to all cells. Furthermore, arthropods obtain oxygen by using one of three structures––gills, book lungs, or tracheal tubes. Most aquatic arthropods (crayfish) have gills. Most terrestrial arthropods (beetles) have a system of branching tubes called tracheal tubes, which branch into smaller and smaller tubules, which carry oxygen throughout the body. Finally, some arthropods, including spiders, have book lungs, or saclike pockets with highly folded walls for respiration.This increased surface area of the lungs allows for an efficient exchange of gases. Both trachea and book lungs open to the outside of the body of some arthropods in opening called spiracles.
METAMORPHOSIS
Metamorphosis is a process where the body shape changes as the insect grows.
Complete Metamorphosis has four stages: egg, larva, pupa, adult (Caterpillars into butterflies; maggots into flies). The entire body shape is changed.
Incomplete Metamorphosis has three stages: egg, nymph, adult (grasshoppers and praying mantis). The nymph is wingless but closely resembles the mature adult. So,
the entire body shaped hasn't changed that much since the egg hatched.
WHY ARE ARTHROPODS THE MOST HEAVILY REPRESENTED ANIMAL GROUP ON THE PLANET?
This phylum is probably, in my opinion, the most important because arthropods take care of the planet in so many ways, and without their presence, multicellular life would vanish, as many arthropods are in the lower or bottom sections of many food chains. They also: help in nutrient recycling, supply food for other phylums, and are pollinators of flowering plants, which is imperative for their reproduction. Others acts as forms of bio-augmentation (spiders and ladybugs consuming deleterious aphids, for example). Their contributions are endless and they have a great impact on the economy. All life on Earth needs these arthropods: all one million species of them (at least).