BIOL113 L29

What are arthropods?

Segmented coelomates with exoskeletons and jointed appendages.

How many individuals are estimated in the world arthropod population?

A billion billion (10^18) individuals.

What percentage of the entire animal kingdom does the phylum containing arthropods represent?

80%

How many arthropod species have been described?

nearly a million

What are the three features contributing to the diversity and success of arthropods?

Body segmentation, a hard exoskeleton, and jointed appendages.

What is the exoskeleton of arthropods constructed from?

Layers of protein and chitin.

What process must arthropods undergo in order to grow?

Molt (ecdysis) its old exoskeleton and secrete a larger one.

What are the sense organs of arthropods?

Eyes for vision, olfactory receptors for smell, and antennae for touch and smell.

What type of circulatory system do arthropods have?

Open circulatory system.

How do most aquatic arthropods perform gas exchange?

They have gills with thin feathery extensions that have an extensive surface area in contact with water.

What specialized gas exchange system do terrestrial arthropods have?

Insect tracheal systems, branched air ducts leading into the interior from pores in the cuticle.

Into how many main evolutionary lineages did arthropods diverge early in their history?

Four main evolutionary lineages: trilobites, chelicerates, uniramians, and crustaceans.

What fluid is circulated in the arthropod's circulatory system?

hemolymph.

How is hemolymph propelled through the arthropod's body?

by a heart through short arteries into sinuses (the hemocoel) surrounding tissues and organs.

Where does the hemolymph go after it is propelled through the arteries?

hemolymph flows into sinuses (the hemocoel) that surround the tissues and organs.

How does hemolymph return to the heart in arthropods?

through valve pores

What is the state of the true coelom in most arthropod species?

coelom is reduced

What distinguishes chelicerates, uniramians, and crustaceans in terms of feeding appendages?

Chelicerates have clawlike feeding appendages called chelicerae, while uniramians and crustaceans have jawlike mandibles.

What sensory features distinguish chelicerates from uniramians and crustaceans?

Chelicerates lack sensory antennae and mostly have simple eyes, while uniramians and crustaceans have antennae and usually a pair of compound eyes in addition to simple eyes.

How do uniramians and crustaceans differ in terms of antennae and appendages?

Uniramians have a pair of antennae and uniramous (unbranched) appendages, while crustaceans have two pairs of antennae and biramous (branched) appendages.

What made the move onto land possible for several groups of arthropods?

The exoskeleton, which initially evolved for protection and locomotion, also solved problems of water loss and provided support when arthropods left the relative buoyancy of water.

What distinguishes millipedes (class Diplopoda) from centipedes (class Chilopoda)?

Millipedes have two pairs of walking legs on each of their many segments and eat decaying leaves and plant matter, while centipedes are terrestrial carnivores with one pair of walking legs on each segment in the trunk region and poison claws on the anterior most trunk segment.

What is the study of insects called?

Entomology, which is a vast field with many subspecialties including physiology, ecology, and taxonomy.

What is the exoskeleton of arthropods made of?

The cuticle, constructed from layers of protein and chitin, with two main layers: procuticle and epicuticle.

What are the main components of the procuticle?

The procuticle consists of exocuticle, endocuticle, and mesocuticle, all of which have protein and chitin bound by glycoprotein.

What is the function of the exocuticle in the arthropod cuticle?

The exocuticle is tanned and provides support, but is missing around joints or along the line where the animal will rupture during molting.

What are the components embedded in the outermost layer of insects?

Wax and proteins.

What is the advantage of the hard components of the arthropod cuticle?

They reduce water loss in the air.

What is the disadvantage of the hard components of the arthropod cuticle?

They prevent growth and require moults (shedding of outer layer).

What does the arthropod cuticle provide protection against?

It prevents the passage of material both in and out of the body, requiring special respiratory and excretory organs.

What are the primary plates that the cuticle consists of?

1. Dorsal tergum, 2. Ventral sternum, 3. Lateral pleura.

What type of animals are arthropods in terms of body structure?

Segmented coelomates with exoskeletons and jointed appendages.

How do arthropods move during locomotion?

Their limbs move backwards and forwards, with an effective stroke and a recovery stroke.

What problem arises when arthropods need to move fast?

Problems with moving fast include the need for longer legs and more energy expenditure.

How can field overlaps and mechanical interference issues be reduced in arthropods?

By reducing the number of limbs, using legs of different sizes, displacing tips, and fusing segments.

What are the locomotory patterns in insects?

3 segments in thorax, 3 pairs of elongated legs, requiring 3 feet on the ground at once, and alternating leg movement.

How do spiders move slowly and quickly?

Slow movement involves separate limbs, while fast movement involves limb tips overlapping.

What are the characteristics of crustacean walking patterns?

They show a variety of walking patterns including forwards, backwards, and sideways movement.

What is one key to the great success of insects?

Flight, which allows them to escape predators, find food and mates, and disperse to new habitats faster than ground-crawling organisms.

What are wings in insects?

Extensions of the cuticle and not true appendages.

What are the hypotheses for the evolution of insect wings?

They evolved as extensions of the cuticle to absorb heat, allowed animals to glide from vegetation to the ground, served as gills in aquatic insects, and functioned for swimming before flight.

How do wings of different insects function?

They are diverse, with variations in structure and function such as similar pairs, hooked together pairs, overlapping anterior and posterior wings, and protective covers.

What is the beat frequency of butterflies, grasshoppers, bees, houseflies, and midges?

Ranges from 4 to 1000 beats per second.

What is the fastest insect and its speed?

The Hummingbird moth, which can reach 25 mph, and the Honey bee, which can reach 15 mph.