Phylum Arthropoda | Characteristics

 

Phylum Arthropoda 

Characteristics 

Phylum Arthropoda is a diverse group of invertebrates that includes insects, crustaceans, arachnids, and many other organisms. Some of the key characteristics of this phylum are:

Segmented body: 

The body of arthropods is divided into segments, with each segment typically bearing a pair of joint appendages.

Exoskeleton: 

Arthropods have a tough, protective outer covering called an exoskeleton that is made of chitin and protein. This exoskeleton provides support and protection for the organism.

Jointed appendages: 

Arthropods have jointed appendages that allow for a wide range of movement and manipulation of their environment.

Bilateral symmetry: 

Like most animals, arthropods exhibit bilateral symmetry, meaning that their left and right sides are mirror images of each other.

Open circulatory system: 

Arthropods have an open circulatory system, meaning that their blood is not contained in vessels and is instead pumped directly into their body cavity.

Respiratory system: 

Most arthropods have a specialized respiratory system that consists of small tubes called tracheae or book lungs.

Molting: 

As arthropods grow, they must periodically shed their exoskeleton and grow a new one in a process called molting.

Nervous system: 

Arthropods have a well-developed nervous system, including a brain and a ventral nerve cord.

Overall, arthropods are incredibly diverse and successful organisms, with over a million known species and many more yet to be discovered.

Exoskeleton in arthropods

Arthropods, such as insects, spiders, and crustaceans, have an exoskeleton, which is a hard, protective outer covering that supports and protects their bodies. The exoskeleton is composed of a tough polysaccharide called chitin, along with proteins and minerals.

The exoskeleton provides several benefits to arthropods. It protects them from physical damage, dehydration, and predators. It also serves as a site for muscle attachment, allowing for greater leverage and strength during movement.

To accommodate growth, arthropods periodically molt their exoskeletons and form new ones. During the molting process, the old exoskeleton is shed, and a new, larger one is formed underneath. This process is energetically costly, and arthropods must consume a lot of food to support the growth of their new exoskeleton.

Overall, the exoskeleton is a vital adaptation that allows arthropods to thrive in a variety of environments and to perform a wide range of activities, from crawling and burrowing to flying and swimming.

Metamerism and tagmetization 

Metamerism and tagmetization are two important features of the body plan of arthropods.

Metamerism, also known as segmentation, refers to the repetition of similar body segments along the length of the body. In arthropods, each segment typically bears a pair of joint appendages and associated muscles, nerves, and sensory organs. The segments are separated by flexible, membranous regions called intersegmental membranes, which allow for flexibility and movement.

Tagmatization is the specialization of body segments into distinct regions or tagmata, each with a specific function. In arthropods, the body is typically divided into three tagmata: the head, thorax, and abdomen. Each tagma is composed of several segments that are fused together and may be modified for specialized functions. For example, the head tagma contains the sensory organs, mouthparts, and brain, while the thorax tagma contains the legs and wings used for locomotion.

Tagmatization is thought to have evolved as a way for arthropods to perform more complex movements and behaviors, as well as to specialize in specific ecological roles. The specialization of body segments into tagmata also allows for greater efficiency in locomotion, feeding, and reproduction.

Metamorphosis 

Metamorphosis is a process of transformation that arthropods undergo as they develop from juveniles into adults. The metamorphosis process varies among different groups of arthropods, but generally, it involves a series of changes in body form, behavior, and physiology.

Arthropods can undergo either incomplete or complete metamorphosis. In incomplete metamorphosis, the juvenile (nymph or nymphal stage) closely resembles the adult, but lacks wings and is sexually immature. The nymphs molt several times, each time becoming more similar in appearance to the adult until they reach maturity. Examples of arthropods that undergo incomplete metamorphosis include grasshoppers, crickets, and cockroaches.
In complete metamorphosis, the juvenile (larval) stage looks nothing like the adult and has a different lifestyle and feeding habits. The larva usually undergoes a dramatic transformation during pupation, forming a chrysalis or cocoon, before emerging as an adult. The adult stage typically has wings and is sexually mature. Examples of arthropods that undergo complete metamorphosis include butterflies, moths, beetles, and flies.
The benefits of metamorphosis include allowing arthropods to exploit different ecological niches and avoid competition with adults for resources. Juveniles and adults may have different food preferences and occupy different habitats, which reduces competition for resources. Metamorphosis also allows for the evolution of more complex life cycles, with juveniles specialized for dispersal and adults specialized for reproduction.