E-Lecture - Important Point
- Arthropoda are invertebrate animals having jointed appendages or legs. It is a phylum of triploblastic, haemocoelomic, segmented body having head, thorax and abdomen, a chitinous exoskeleton and jointed legs and appendages.
- Arthropods is basically subdivided into five subphyla:
- Trilobites had disappeared in the Permian–Triassic extinction event.
- Chelicerates consist of arthropods such as spiders, mites, scorpions, horseshoe crabs, and other related organisms.
- Myriapods consist of arthropods such as the centipedes, millipedes, and their other relatives.
- Crustaceans are considered to be primarily aquatic and are basically characterized by having biramous appendages. Examples that are included in the Crustaceans are crabs, lobsters, crayfish, shrimp, and many more.
- Hexapods mainly consist of insects and three small orders of insects such as the animals with six thoracic legs.
- Sexual reproduction is the most preferred option by the arthropods that live in the aquatic environment and it is done by means of external fertilization. All the terrestrial arthropods are known to reproduce by the means of internal fertilization.
- Aquatic arthropods (crustaceans and the chelicerate horseshoe crabs) possess gills for respiration.
- Terrestrial arthropods possess tracheae and book lungs as respiratory organs.
- Molting and metamorphosis are two types of events in the lifecycle of animals. Molting mainly refers to the shed of the exoskeleton in arthropods. Metamorphosis is the transformation process of the animals from an immature form to a mature form.
- Complete and incomplete metamorphos are stages of growth and development in insects. The two occur in stages where they start with the egg stage and end with the adult stage. Complete metamorphosis occurs in four stages; egg, larva, pupa, and adult. Incomplete metamorphosis occurs in three stages; egg, nymph, and adult.
- Vectors are living organisms that can transmit infectious pathogens between humans, or from animals to humans. Many of these vectors are bloodsucking insects, which ingest diseaseproducing microorganisms during a blood meal from an infected host (human or animal) and later transmit it into a new host, after the pathogen has replicated.
- Honey bees rely on an important social structure that is highly organized. The colony itself-taking up residence in the hive consists of three types of honey bee: queen bees (egg producers), worker bees (infertile females), and drones (males whose purpose is to find and mate with a queen bee).
- A termite colony includes two major castes-sterile castes and reproductive castes. The caste system and the size of the colony are controlled by a pheromone, called social hormone, which is secreted by the members of reproductive castes (e.g., king and queen).
- Honey bees are used commercially for large scale pollination and honey production.
- Termites are important in the ecosystem as they consume and recycle wood, litter, leaf, and dung and release the nutrients back to the ecosystem.
- Insect pests destroy crops in the field through their biting, chewing, boring, sucking and defoliation activities.
- Chemical control of pests in agriculture and horticulture is a method of controlling pests through chemicals poisonous for pests.
- Biological control is the use of living organisms to suppress pest populations.
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