Arthropods belonging to the phylum Arthropoda, constitute the largest phylum within the animal kingdom. This diverse group encompasses a wide array of creatures, including well-recognized organisms like crabs, lobsters, spiders, mites, insects, centipedes, and millipedes.
Remarkably, approximately 84 percent of all documented animal species fall within the boundaries of this phylum
What Are Arthropods?
Arthropods are a vast and highly diverse group of invertebrate animals that belong to the phylum Arthropoda. They make up the largest phylum in the animal kingdom, with over one million described species and many more yet to be discovered.
They are found in nearly every habitat on Earth from the deep sea to mountaintops, and they play critical roles in ecosystems.
General Features
Exoskeleton
Arthropods have a tough, external skeleton made of chitin, a complex carbohydrate. This exoskeleton provides support, protection, and a framework for muscle attachment. It is periodically shed and replaced as the animal grows.
Segmented Bodies
They typically have segmented bodies, with each segment bearing a pair of jointed appendages. This segmentation allows for flexibility and specialization of body parts for various functions.
Jointed Appendages
They are characterized by jointed limbs, which are adapted for a wide range of functions, including walking, swimming, grasping, and feeding. These appendages are highly flexible and versatile.
Molt (Ecdysis)
They grow by periodically shedding their exoskeleton in a process called molting or ecdysis. They produce a new, larger exoskeleton underneath the old one, which hardens after molting.
Specialized Sensory Organs
Many arthropods have well-developed sensory organs, including compound eyes, antennae, and specialized sense organs for detecting chemicals, vibrations, and temperature changes.
Diverse Respiratory Systems
They have evolved various respiratory systems to meet their oxygen needs. These include gills (for aquatic species), tracheae (air tubes), book lungs (found in some arachnids), and cutaneous respiration (breathing through their exoskeleton).
Mouthparts and Feeding Strategies
Arthropods exhibit a wide variety of mouthparts and feeding strategies, depending on their species. They can be herbivores, carnivores, scavengers, filter feeders, or parasitic.
Life Cycle Diversity
They exhibit diverse life cycles, including direct development (no larval stage), incomplete metamorphosis (gradual development through nymph stages), and complete metamorphosis (distinct larval and pupal stages).
Habitat Adaptations
Arthropods are found in nearly every habitat on Earth, from the deep sea to mountaintops. They have adapted to a wide range of environments, including terrestrial, freshwater, and marine ecosystems.
Characteristics of Arthropods
Exoskeleton
They have a tough external skeleton made of a material called chitin. This exoskeleton provides support and protection for the animal's body.
Segmented Bodies
They typically have segmented bodies, with each segment bearing a pair of jointed appendages.
Jointed Appendages
Arthropods are characterized by jointed limbs, which are adapted for various functions such as walking, swimming, grasping, or feeding.
Molt (Ecdysis)
Arthropods grow by shedding their exoskeleton in a process called molting or ecdysis. They produce a new, larger exoskeleton underneath the old one, which hardens after molting.
Diverse Respiratory Systems
Arthropods have various respiratory systems, including gills (for aquatic species), tracheae (air tubes), and book lungs (a type of respiratory organ).
Diverse Lifestyles
Arthropods exhibit a wide range of lifestyles, including herbivores, carnivores, scavengers, parasites, and filter feeders. They occupy diverse ecological niches.
Well-Developed Sensory Organs
Many arthropods have well-developed sensory organs, including compound eyes, antennae, and specialized sense organs for detecting chemicals, vibrations, and temperature.
Types of Arthropods
Crustaceans (Subphylum Crustacea)
Crustaceans are primarily aquatic arthropods with two pairs of antennae and typically two pairs of appendages on most body segments.
Myriapods (Subphylum Myriapoda)
Myriapods include centipedes and millipedes. They have elongated bodies with many segments, and each segment typically bears one or two pairs of legs.
Chelicerates (Subphylum Chelicerata)
Apart from spiders and scorpions, this group also includes horseshoe crabs and sea spiders. Chelicerates are characterized by having chelicerae (pincer-like mouthparts) and typically six pairs of appendages.
Trilobites (Class Trilobita)
Trilobites are now extinct arthropods that lived millions of years ago. They had a distinctive three-lobed body shape and a hard exoskeleton. Fossils of trilobites provide valuable insights into ancient ecosystems.
Hexapods (Class Entognatha)
Hexapods are a group of six-legged arthropods that include springtails and proturans. They are often considered a separate class but are closely related to insects.
Other Minor Groups
Some minor arthropod groups include remipeds, branchiopods, pycnogonids (sea spiders), and tardigrades (water bears).
Examples of Arthropods
Insects
The largest class of arthropods, insects comprise creatures such as ants, bees, butterflies, beetles, and grasshoppers.
Arachnids
This class includes spiders, scorpions, ticks, and mites.
Crustaceans
Crustaceans are aquatic arthropods and include crabs, lobsters, shrimp, and barnacles.
Myriapods
This group includes centipedes and millipedes.
Chelicerates
Apart from spiders and scorpions, chelicerates also encompass horseshoe crabs and sea spiders.
Trilobites
Extinct arthropods that lived millions of years ago.
List of Arthropods
- Ants
- Bees
- Butterflies
- Beetles
- Mosquitoes
- Flies
- Grasshoppers
- Dragonflies
- Moths
- Spiders
- Scorpions
- Ticks
- Mites
- Harvestmen (daddy longlegs)
- Crabs
- Lobsters
- Shrimp
- Barnacles
- Crayfish
- Isopods (e.g., pill bugs)
- Centipedes
- Millipedes
- Horseshoe crabs
- Sea spiders
- Trilobites (extinct)
- Springtails
- Proturans
- Remipeds
- Branchiopods
- Pycnogonids (sea spiders)
- Tardigrades (water bears)
FAQs
Q: What are arthropods?
Ans: Arthropods are a diverse and highly numerous group of invertebrate animals belonging to the phylum Arthropoda.
Q: How many species of arthropods are there?
Ans: They make up the largest phylum in the animal kingdom, with over a million described species. Scientists estimate that millions more remain undiscovered.
Q: How do arthropods grow?
Ans: They grow by periodically shedding their exoskeleton in a process called molting or ecdysis. They produce a new, larger exoskeleton underneath the old one.
Q: What are some common examples of arthropods?
Ans: Common examples include ants, bees, butterflies, spiders, scorpions, crabs, lobsters, and mosquitoes.
Q: Do all arthropods have jointed legs?
Ans: Yes, one of the defining characteristics is their jointed appendages. These limbs are adapted for various functions, such as walking, swimming, and grasping.
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