Phylum Arthropoda

• What is the world’s STRONGEST ANIMAL?

• The RHINOCEROS beetle: is able to carry up to 100 times its own weight. This animal can carry over 200 grams on its 2-gram frame.

CHARACTERISTICS of ARTHROPODS:

• 1. Arthropods have jointed appendages. –Appendages are extensions of the body and include legs, and antennae.

• 2. The arthropod body is segmented. –A pair of appendages is attached to each segment.

• 3. Arthropods have a hard exoskeleton that provides protection and support.

• 4. Arthropods have specialized organ systems. They consist of –ventral nervous system, –open circulatory system, –a digestive system, and –specialized receptors.

What character- istics of arthropods can you observe in this slide?

Jointed Legs:• The phylum of Arthropods is the

largest and most diverse animal phylum .

•About 84 percent of known animals species are arthropods.

• Arthropods inhabit every region of the Earth- ocean bottoms to mountain tops.

•This group includes : •Spiders, crabs, scorpions, and lobsters. –Unlike annelids, arthropods have jointed appendages.

Recognized by the eight legs attached to the cephalothorax, spiders are very useful and should not be killed. They eat only insects and other small pests.

Scorpions catch prey with their enlarged pedipalps and tear their prey apart. The stinger on the tail is used mostly in defense.

The word Arthropod means: JOINTED FEET”.

•These jointed appendages of arthropods are specialized for SENSING, EATING,

•REPRODUCTION, MOVING and PROTECTION.

An isopod Cyclops

Exoskeleton:• The outer covering is called an

EXOSKELETON which is a hard covering on the outside of the body that provides both support and protection.

The exoskeleton is made of CHITIN. Some exoskeletons are leathery like caterpillars, and some are tough and hard like ticks and crabs.

The water flea,

Daphnia

Centipedes are fast moving predators with one pair of legs per body segment. They have fangs to inject poison and will attack animals larger than themselves. (Class Chilopoda)

Millipedes are slow moving with two pairs of small legs per body segment. They eat plant material & do not have poison glands. Their bodies are more rounded than centipedes. When threatened, many of them will coil up to protect their softer underbelly (Class Diplopoda)

•The bodies of arthropods are divided into segments.

• Some arthropods have dozens of segments like centipedes and millipedes

•other arthropods have THREE segments. (ants for example)

•Muscles are attached to the exoskeleton that enable the arthropod to move.

•This hard outer covering provides greater protection than the endoskeleton of humans.

The downside:

•There is a drawback to this protection. –The arthropod must shed its covering to grow. When an arthropod sheds its outer exoskeleton it is called MOLTING. When the arthropod molts it grows a new layer of CHITIN .

FEEDING AND RESPIRATION:

• Arthropods include individuals with diverse feeding habits. –There are both herbivores and carnivores along with filter feeders, detritus feeders, blood-suckers, and a host of specialized parasites.

Respiration:

•Arthropods also demonstrate different means of respiration.

•Aquatic species of arthropods breathe through gills, which are feather like organs located in a chamber beneath the exoskeleton.

•Some arthropods breath through layers of respiratory tissue that resemble pages in a book.

Horseshoe crabs

breathe through

book gills,

and spiders

breathe through

book lungs.

–Most terrestrial arthropods breathe through a branching air-filled network of structures called TRACHEAL TUBES.

–These tubes connect the arthropod’s tissues with atmosphere and oxygen passes through the tracheal tubes by diffusion.

Circulation: •The arthropods have an OPEN CIRCULATORY system.

•Arthropods have well-developed heart that pumps blood through arteries into smaller vessels from which it flows into spaces called SINUSES.

•The muscles slosh the blood to bathe body tissues.

•The blood collects in a large sinus surrounding the heart.

EXCRETION:Arthropods excrete nitrogen wastes in several ways.

In most terrestrial species wastes are excreted by dead end sacs called MALPIGHIAN TUBULES. These malpighian tubules concentrate wastes and add them to feces moving through the gut.

Aquatic arthropods

• excrete nitrogenous wastes by allowing ammonia to diffuse through the gill surface.

•(add this)

Classification:

•Scientists classify arthropods based on developmental patterns. –There are four subphyla of arthropods.

–Trilobita (Trie-luh-BITE-uh) includes extinct organisms called trilobites

–Crustacea (Kruss-TAY-shuh) includes shrimp, lobsters, crabs,

–Chelicerata (kul-LISS-uh-RAHT-uh) includes spiders, scorpions, ticks, mites, and sea spiders

–Uniramia (YOO-nuh-RAY-mee-uh) The only group that seems to have evolved on land and includes centipedes, millipedes, and all insects.

Embyro differences:

•The four subphyla are distinguished primarily by differences in their embryological development and differences in the morphology of structures such as appendages and mouthparts.