Features of organism - Taxonomy Part.2
The Hierarchy of Classification:
Animals are organized into large groups called phyla. Within these phyla, organisms are further divided into classes.
• Arthropods: Includes classes such as Crustacea, Insects, Arachnids, and Myriapods.
• Vertebrates: Includes classes such as Fish, Amphibia, Reptiles, Birds, and Mammals.
• Note: Mammals are further divided into subgroups like Primates, Rodents, Carnivores, and Insectivores.
The term invertebrate is commonly used to describe any animal lacking a vertebral column (backbone), though it is a label of convenience rather than a formal biological group.
General Features of Arthropods:
The name "arthropod" translates to "jointed limbs." All members of this phylum share three primary characteristics:
1. Exoskeleton: A hard, firm external skeleton called a cuticle that encloses and protects the body.
2. Segmentation: Bodies are made of several sections.
3. Flexible Joints: Located between segments to allow for movement despite the rigid exterior.
In most species, segments are grouped into three distinct regions: the head, the thorax (middle), and the abdomen (rear).
Class: Crustacea
This class includes marine animals (crabs, lobsters), freshwater species (water fleas), and land-dwellers (woodlice).
Key Physical Features:
• Antennae: They possess two pairs of long, thin feelers used for sensing chemicals and touch.
• Compound Eyes: These are made of numerous separate lenses. While they provide a simple image, they are exceptionally sensitive to motion.
• Body Structure: They typically have a cephalothorax (a fused head and thorax) and a segmented abdomen.
• Limbs: Most segments have a pair of jointed limbs. Those on the head are often specialized into mouthparts or antennae.
Class: Insects
Insects represent a massive and diverse group within the arthropods, including familiar organisms like butterflies, beetles, and bees.
Key Physical Features:
• Body Regions: Insects have three very distinct regions: head, thorax, and abdomen.
• Legs: They consistently possess three pairs of jointed legs, all of which are attached to the thorax.
• Wings: Most insects have two pairs of wings.
• Sensory Organs: Like crustaceans, they have compound eyes and a firm exoskeleton.