Arthropods: Characteristics and Classes

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Questions and Answers

What percentage of all animal species are arthropods?

90%

75%

95%

85% (correct)

What is the main function of the exoskeleton in arthropods?

To protect inner organs (correct)

To provide movement

To aid in respiration

To regulate body temperature

Which class of arthropods includes spiders, ticks, and scorpions?

Crustacea

Arachnida (correct)

Insecta

Diplopoda

How do insects breathe?

By tracheae Signup and view all the answers

What is a characteristic of the body of arachnids?

Divided into 2 parts: prosoma and opisthosoma Signup and view all the answers

Why are insects considered successful animals?

Due to their short life cycle and adaptability Signup and view all the answers

Which of the following is an order of insects of medical importance?

Diptera Signup and view all the answers

What is the term for the tough, outer covering of an arthropod's body?

Cuticle Signup and view all the answers

What is the main function of the mid gut in insects?

Secretion of enzymes and absorption of nutrients Signup and view all the answers

What is the function of the peritrophic membrane in insects?

To prevent damage to delicate secretory cells Signup and view all the answers

What is the function of anticoagulins in the saliva of blood-sucking insects?

To prevent blood clotting Signup and view all the answers

What is the name of the structure that stores food during digestion in insects?

Crop Signup and view all the answers

What is the function of the Malpighian tubes in insects?

To excrete metabolic waste Signup and view all the answers

What is the main characteristic that distinguishes Exopterygota from Endopterygota?

Wings develop externally Signup and view all the answers

Which order of insects comprises mosquitoes, blackflies, houseflies, and tsetse flies?

Diptera Signup and view all the answers

What is the function of the rectal papillae in insects?

To absorb water from the gut Signup and view all the answers

What is the process called when an insect sheds its exoskeleton?

Ecdysis Signup and view all the answers

What is the term for the period of time between each ecdysis?

Stadia Signup and view all the answers

What is the name of the sensory organs found in an insect's head?

Palps Signup and view all the answers

What is the name of the upper lip in an insect's mouthparts?

Labrum Signup and view all the answers

What is the term for the transformation from egg to adult in insects?

Metamorphosis Signup and view all the answers

Which type of insect development is characterized by gradual metamorphosis?

Hemimetabolism Signup and view all the answers

What is the name of the compound eyes found in insects?

Ommatidia Signup and view all the answers

What is the name of the three parts that make up an insect's thorax?

Prothorax, Mesothorax, Metathorax Signup and view all the answers

What is the primary function of the veins in an insect's wing?

To contain trachea, nerves, and haemolymph Signup and view all the answers

What is the term for the area of wing membrane surrounded by veins?

Cell Signup and view all the answers

What is the main component of the insect cuticle?

Chitin Signup and view all the answers

What is the term for the dorsal, sclerotized region of a thoracic segment?

Tergum Signup and view all the answers

What is the purpose of the wax secreted by the wax filaments?

To make the cuticle impermeable to water Signup and view all the answers

What is the term for the system of veins on an insect's wing?

Venation Signup and view all the answers

What is the main function of tracheae in the respiratory system of insects?

To converge air to tissues Signup and view all the answers

What prevents the collapse of tracheal tubes?

Spiral thickenings Signup and view all the answers

Where are spiracles present in insects?

On the meso and meta thoraces and 1st to 8th abdominal segments Signup and view all the answers

What is the function of the supra-esophageal ganglion in the nervous system of insects?

To coordinate movement and stimuli Signup and view all the answers

What type of receptor senses touch, vibration, and hearing in insects?

Mechanoreceptors Signup and view all the answers

What is the basic sense organ in insects?

Neuron Signup and view all the answers

Study Notes

Arthropods

The largest group of invertebrates, comprising 85% of all animal species.
Characterized by a tough skin covering, known as a cuticle, which is periodically shed through a process called ecdysis.
Possess jointed appendages, such as legs and antennae, and an exoskeleton that provides protection and support.

Classes of Arthropods

Insecta: includes houseflies, characterized by three pairs of legs, two pairs of wings, and respiration through tracheae.
Crustacea: includes cyclops, crabs, and lobsters.
Arachnida: includes ticks, spiders, mites, and scorpions.
Diplopoda: includes millipedes.
Chilopoda: includes centipedes.

Insects

Body divided into three parts: head, thorax, and abdomen.
Respiration occurs through tracheae.
Largest group of arthropods, with over 1 million described species.
Characteristics contributing to their success:
- Short life cycle
- Adaptability and capacity for flight
- Small size, requiring minimal food and shelter
- Variation in lifestyle
- Light, strong, water-proof skeleton
- Large reproductive ability
- Adaptation of appendages
- Sensory sophistication

Subclasses of Insects

Apterygota: wingless, with no metamorphosis.
Pterygota: winged or secondary wingless, with metamorphosis.
Exopterygota: wings develop externally, with gradual metamorphosis.
Endopterygota: wings develop internally, with complete metamorphosis.

Medically Important Insects

Order Diptera: includes mosquitoes, blackflies, and houseflies.
Other orders of medical importance: Anoplura (lice), Odonata (dragonflies), Dictyoptera (cockroaches), Orthoptera (locusts), Coleoptera (beetles), Hymenoptera (bees, ants), and Lepidoptera (moths and butterflies).

Growth and Metamorphosis

Growth occurs in discrete stages, with the exoskeleton being shed and replaced through a process called ecdysis.
The process of transformation from egg to adult is called metamorphosis.
Incomplete metamorphosis (hemimetabolism): characterized by gradual changes from egg to adult, with a series of instars (stages) between egg and adult.
Complete metamorphosis (holometabolism): characterized by distinct stages of egg, larva, pupa, and adult, with significant changes between each stage.

Insect Head

Fused segments, with a series of hexagonal lens forming the compound eyes.
Simple eyes (ocelli) may be present, but are not capable of perceiving movement.
Presence of antennae and palps (sensory organs).
Mouthparts: upper lip (labrum), lower lip (labium), mandibles, maxillae, and hypopharynx.

Insect Thorax

Divided into prothorax, mesothorax, and metathorax.
Three pairs of legs, with segments including coxa, trochanter, femur, tibia, tarsus, and claws.
Wings are outgrowths of the terga, with distinct lines of thickening called veins.
Wing venation is important for classification.

Respiratory System

Direct diffusion through spiracles, which are connected to internal tubes called tracheae.
Tracheae branch repeatedly to form fine tubes called tracheoles, which end in the cells.
No oxygen-carrying chemicals are present in insects.

Nervous System

Three pairs of ganglia in the head are fused to form a brain, which coordinates movement and stimuli.
Ventral nerve cord arises from the brain and reaches body parts.
Basic sense organ is the neuron, which has a sense cell at its base and axons.
Modifications arise for mechanoreceptors, chemoreceptors, photoreceptors, and humidity and temperature reception.

Alimentary Canal

Great diversity due to types of food eaten.
Mouthparts vary according to type of food eaten.
Three main regions: foregut, midgut, and hindgut.
Foregut includes mouth, buccal cavity, pharynx, oesophagus, crop, and proventriculus.
Midgut is where most digestion occurs.
Hindgut includes ileum, rectum, and anus, with malpighian tubes and rectal papillae aiding in digestion and absorption.

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Description

Learn about the characteristics of arthropods, including their exoskeleton, jointed appendages, and cuticle. This quiz covers the different classes of arthropods, such as insects, crustaceans, arachnids, and more.