In this super guide, you are going to learn about the phylum Arthropoda step by step with Diagrams.
- what are arthropods?
- Classification of arthropods.
- general characteristics
- reproduction of Arthropoda
- Lots more
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Let’s Dive right in…
What are Arthropods?
Arthropods are animals whose bodies covered or consist of an exoskeleton rather than a skeleton. they have an external skeleton, segmented bodies, and jointed legs. this exoskeleton is called a cuticle and formed a linear series of ostensible segments, with appendages of articulated pieces.
these are known as an evolutionary group (or phylum ) of invertebrates (the most diverse phylum of the animal kingdom) having a complex organization.
it is said that two of every three known species of animals are arthropods. they belong to the phylum Arthropoda and nearly found in every habitat of the biosphere. bilateral symmetry, triploblastic and jointed limbs are common Arthropoda Characteristics. spiders, insects, centipedes, millipedes are general common examples.
Common examples of arthropods
as arthropods are categorized into four different groups such as Arachnids, Insects, Crustaceans, and Myriapods. let’s have a look at examples of each in details:
- Black widow
- Wasp spider
- Praying mantis
- Devil’s horse
- water bug
- Moth caterpillar
Examples of Crustaceans
- Spider crab
- Sea spider
- Sea acorn
- American lobster
- Marine royal cricket
- Sand witch
- Anchor worm
- Giant isopod
- Pea crab
Examples of Myriapods
Phylum Arthropoda Characteristics
The phylum Arthropoda contains more species than any other phylum. they have their bodies successively segmented in a way similar to that of annelids and also have differentiated sections with the presence of the following order: head, thorax, and abdomen. an articulated skeleton formed by chitin (a carbohydrate) protect their bodies against rivals and predators.
the exoskeleton is found outside of the body by covering it. throughout the life of arthropods, they face problems to grow because the skeleton should have changed in several successive stages. in this way, the animals are allowed the development of a new skeleton which is adapted to the larger dimensions.
the development can either be direct or indirect highly depends on the nature of the species.
Insects like cockroaches, grasshopper, butterflies, and mosquitoes are the most common Arthropoda Characteristics. They show the following characters. here is the list of some common characteristics:
- Jointed foot: They are commonly called Arthropods, Word “arthro” means “joined” and “pod” means “feet”. So they have jointed legs.
- Segmentation: Their body is segmented. Segments are attached to each other by a modified part of the cuticle. This cuticle is thin and flexible. So they possess jointed appendages. These appendages are modified to perform special functions.
- Relationship with Annelida: The annelids and arthropods have many common characteristics like the segmented body, appendages, and cuticle. So it is believed that both annelids and arthropods have a common origin.
- Body Form: Arthropods have different body structures. Some are worm-like centipedes. Some are flying insects. Their body is divided into head, thorax, and abdomen. Their body is covered with a waterproof chitinous cuticle. It is secreted by the epidermis.
- Coelom: The coelom does not form the main body cavity. They have developed hemocoel. It is a reduced coelom. It is communicated with the blood vascular system.
- Digestive system: Their digestive system is in the form of an alimentary canal. It has two openings, a mouth, and an anus. The alimentary canal is divided into different parts. Each part performs a specific function. Their food is small plants and animals.
- Excretory system: A well-developed excretory system is present in Arthropoda. It is composed of Malpighian tubules. The nitrogenous waste of arthropods is solid uric acid.
- Nervous system: They have a highly developed nervous system. It consists of paired ganglia (simple brain). These ganglia are connected to a central double nerve cord. A ganglion is present in each segment (segmental ganglion). Nerves arise from these ganglia. The sensory organs are a pair of eyes and a pair of antennae.
- Respiratory system: Most arthropods possess an extensive tracheal system for the exchange of gases. This tracheal system is composed of air tubes called tracheae. The main tracheae open outside through openings called spiracles. Respiration in aquatic arthropods takes place through gills.
- Blood vascular system: They have a unique blood vascular system. They have an open circulatory system. The blood openly flows through the body cavity and bathe the tissue of the body. However, they have a primitive heart and a blood vessel. Their blood does not have hemoglobin. So it is colorless.
- Exoskeleton: The skeleton is external i.e. exoskeleton. In this case, the cuticle forms the outer covering. The cuticle is light in weight and it is chiefly composed of chitin. It provides a surface for the attachment of muscles. These muscles are used for locomotion.
- Locomotion: They show active and swift (fast) movements. Their mode of locomotion depends on their habitat. So they can swim, crawl or fly. The organs of locomotion are paired appendages, Insects also have paired wings.
Due to the infinite evolutionary capacity, arthropods have a variety of feeding mechanisms which are as follows:
- Decomposers: decomposers can only feed on the decomposing of organic matter by taking the advantage of dead animals, remaining foods, wastes, and fallen leaves. flies and cockroaches are common examples of decomposers.
- Herbivores: Herbivores often feed on fruits, stems, algae, multiple plants, etc. caterpillars are known as herbivores.
- Parasites: Parasites mostly feed on larger animal substances. for example,
blood drawing directly from their bodies. fleas, lice, and ticks are common parasites.
- Predators: predators as from the name, feen on by predating other animals by constituting active and fearsome predators. spiders or scorpions are common examples of predators.
Breathing of Arthropods
because of the adaptation into various environments their respiration or breathing occurs through lungs or tracheae (air) or gills (water). marine crustaceans, such as lobsters have this type of characteristic.
Reproduction and life History of Phylum Arthropoda
The changes which take place during the conversion of a larva into an adult are called metamorphosis. “Meta” means “change” and “morphe” means “from”. It is the characteristic feature of the life histories of the insects. There are three morphologically distinct stages in the life cycle of the Arthropods
- Egg: It develops into a larva.
- Larva: It changes into a motionless pupa.
- Pupa: It finally develops into an adult.
Metamorphosis is incomplete in some primitive insects. The larva resembles the adult is called nymph or instar. It lives in the same habitat as an adult.
Classification of Phylum Arthropoda
The phylum Arthropoda is a large group. It consists of a variety of animals that have been divided into four major groups that are:
Class Arachnida (Arachnids)
they have four pairs of legs and a lack of wings and antennae. Class Arachnids bodies are divided into cephalothorax and abdomen. they are also Endowed with chelicerae.
- The anterior segments of the body are fused to form a combined cephalothorax.
- The cephalothorax has the following appendages
- A pair of chelicerae with claws.
- Two pairs of pedipalps.
- . Four pairs of legs.
- . There are no antennae and no true jaws.
- The abdomen may be segmented. It may or may not have appendages.
- Respiration takes place by gills, lungs, or special structures called book lungs.
- Excretion takes place by Malpighian tubules.
- Eyes are simple.
- Sexes are separate.
- They are oviparous.
- No true metamorphosis.
Examples: Scorpions, spiders, mites, and ticks
Class Insecta (Insects)
This is the largest group of all the animal kingdom and the most varied and numerous of all arthropods. this is the reason that Insects are found everywhere. They may show social behavior like aunts. An arthropod having a pair of antennae two pairs of wings (either functional or not), and three pairs of legs are called an insect. they can adopt any physical environment and are found in different varieties such as predators, parasites, herbivores, and detritophages, etc.
- The body of insects is divided into three distinct regions:
- Head: There is a pair of antennae and compound eyes on the head. The head is usually vertical in position to the body and jaws are centrally placed.
- Thorax: The thorax has three segments. These three segments have three pairs of jointed legs and two pairs of wings.
- Abdomen: It has different numbers of segments.
- The brain is composed of fused ganglia. There is a double nerve cord on the ventral side.
- Sexes are separate and animals are oviparous
- Metamorphosis takes place during development.
Examples: Dragonfly, Mosquitoes, butterflies, moths, wasps, and beetles, etc.
Class Crustacea (Crustaceans)
they are Mostly aquatic and living in seas such as lobster or crab but they can also adopt humid terrestrial environments to the land. they are always present in a nauplius larval stage which is considered as characteristic of their evolution as a class.
- They are aquatic. They have gills for respiration.
- The dorsal side of the cephalothorax (head + thorax) has an exoskeleton called the carapace.
- There is a deposition of salts in the exoskeleton along with chitin. It makes the exoskeleton more firm (strong).
- The appendages are modified for capturing food, walking, swimming, respiration, and reproduction.
- The coelom is reduced and it is in the form of the hemocoel.
- The Head has two pairs of antennae, one pair of the mandible (jaws), and two pairs of maxillae.
- Sexes are mostly separate.
Examples: Daphnia, Cyclops, Crabs, lobsters, prawn, woodlouse.
Myriapods are Equipped with long bodies and multiple legs such as jaws (chelicerae) and are mostly similar to insects in many things. they are considered terrestrial and often so poisonous. the common examples of Class Myriapoda are centipedes and millipedes.
- Their body ¡s divided into a large number of segments.
- Each segment has a pair of legs.
- A pair of antennae and a pair of eyes are present on the head.
Examples: Centipedes and Millipedes.
General Organization of Arthropods
Arthropods show all the characteristics of the higher organisms. They have bilateral symmetry. Arthropods are triploblastic and coelomate. They have a well-developed organ system. So they have reached the peak (last stage) of the invertebrate evolution. There are two main achievements of the Arthropods. These are the chitinous exoskeleton and locomotory mechanisms.
1. Chitinous Exoskeleton
Chitin is a non-living and non-cellular compound, composed of protein and carbohydrates. It is secreted by the outer epidermis.
There is a waxy layer on the outer side of the chitin. Chitin is soft and flexible in some arthropods. It is soft and flexible in certain parts of some other Arthropods. It is hard for remaining Arthropods.
Functions of chitin: It performs the following functions:
- Generally, it is used for protection.
- It also acts as a lever for the movement of muscles of the jointed limbs.
- The chitin in the jaws is used for biting (breaking) and crushing food.
- It forms the lens of the compound eyes.
- Chitin forms the copulatory (sex) organs.
- It forms the organs of offense and defense.
Molting or Ecdysis: Chitinous exoskeleton is shed from time to time in the young larva. It allows the larva to grow. This process of shedding of the exoskeleton is called MouIting or ecdysis.
In short exoskeleton of chitin is one of the primary factors in the success of the Arthropoda. It has helped them to adapt to different habitats.
2. Jointed appendages
The bodies of the Arthropoda, like Annelida, are divided into similar segments. However, the segmentation in the Arthropods is not metameric.
Their organs are not repeated in different segments. Each segment has a pair of jointed appendages. But in most cases, this arrangement is modified. Their segments and appendages become specialized for performing different functions in different habitats. Joint appendages perform the following functions:
- Joint appendages provide an efficient means of locomotion in all kinds of habitats. These animals can walk, swim, or fly.
- They are used as organs of o fence and defense.
- They also help in reproduction.
Economic importance of Phylum Arthropoda
There is a war between man and insects for food and space (place of living). Insects attackman, his domestic animals, and his crops. They cause a large number of diseases in them. They destroy the properties and crops and cause economic losses to man. Some insects are also useful for men like a honey bee or silkworm. So insects have great importance for mankind.
1. Harmful Insects
Harms in animals: Many types of mosquitoes, flies, fleas, lice, and bugs transmit diseases causing organisms to man and domestic animals. Some of these are:
- Mosquito: Female Anopheles mosquito transmits Plasmodium. Plasmodium causes malaria in man.
- Tse-tse fly: It transmits Trypansoma in African countries. Trypanosoma causes sleeping sickness and skin disease in man. Some species of Trypanosoma also cause diseases in cattle.
- Common house fly: It transmits disease-causing organisms to food. This contaminated food causes cholera, hepatitis, etc.
Harms in Plants:
- A large number of insects laid eggs on fruits and other commercial crops like sugar-cane, maize (corn), cotton, and vegetables. The larvae of these animals damage fruits and crops. It causes economic losses to the farmers.
- The locust moves a large number from country to country. They damage the standing crops and other plants.
2. Beneficial Insects
There are the following beneficial insects:
- The honey bee provides man honey and wax.
- Silkworm gives us silk.
- Some insects eat harmful insects.
- Some insects are scavengers. They eat dead animals and decayed vegetables.
- The larvae of insects are sources of food for fish.
Other Related Phyla:
- Phylum Porifera Characteristics & Examples
- Phylum Chordata Characteristics & Classification
- Characteristics of Phylum Echinodermata
- Phylum Nematoda Characteristics, Examples
- Phylum Mollusca Characteristics and Examples
- Phylum Annelida Characteristics and Examples
- Phylum Platyhelminthes Characteristics and Examples
- Phylum Coelenterata/Cnidaria Characteristics and Examples
- Phylum Arthropoda With Examples & Characteristics
- Phylum Protozoa: Characteristics & Groups/Classes
Question: Which group of animals belongs to the phylum Arthropoda, based on the characteristic features like jointed appendages, exoskeleton, and bi or tri segmented body? * 1 point sponges, corals and comb jellies hydra, sea anemone and jellyfish flatworm, roundworm and snail lobster, crab, and spider