MBIO162 Arthropod Diversity

What are arthropods?

Animals with a segmented body design.

What unifying features do arthropods share with annelids?

Through gut, ventral nerve cord with segmental ganglia, dorsal circulatory system.

What is the composition of an arthropod's skeleton?

Composed of chitin, proteins, and mineral salts such as calcium carbonate.

What are the main defining features of arthropods?

Segmented body, ventral nerve cord, chitinous exoskeleton, paired jointed appendages.

How many described species are there in the Arthropoda phylum?

Over 1,100,000 described species.

What percentage of animal diversity do arthropods represent?

86% of animal diversity.

What is the estimated range of extant arthropod species?

3 to 50+ million species.

Where do the majority of arthropod species occur?

In tropical environments, especially among insects like beetles.

In which habitats do arthropods occur?

Deep ocean, high mountains, ground, forest canopies, glaciers, caves.

What are Chelodesmidae?

A family of relic species that includes external and internal animal parasites.

What is Sacculina?

A barnacle parasite of crabs that spreads through the host.

What ecological importance do arthropods have?

They are key players in almost all global ecosystems.

When did arthropods begin their world domination?

Since before the Cambrian explosion, around 540 million years ago.

What is the primary function of the cuticle in arthropods?

Provides skeletal support and is important for land colonization.

What is tagmosis?

Formation of functionally specialized regions in an arthropod's body.

Name the three tagmata in a locust.

Head, thorax, abdomen.

How many segments can a lobster's thorax have?

Eight segments.

What is the significance of allopatric speciation in arthropods?

It leads to the widespread distribution of arthropods across different environments.

How many subphyla of arthropods are recognized today?

Three extant subphyla: Pancrustacea, Cheliceriformes, Myriapoda.

What are the main groups of arthropods?

Crustacea, Hexapoda, Cheliceriformes, Myriapoda.

What is Crustacea?

A group that includes crabs, shrimps, lobsters, and barnacles.

What is unique about hexapods?

They are the most diverse organisms and ecologically dominant on land.

What defines Cheliceriformes?

Body composed of two tagmata; presence of chelicerae and pedipalps.

What is the average number of new insect species described annually?

Approximately 7,000 new species.

What are the three types of metamorphosis in insects?

Ametabolous, hemimetabolous, holometabolous.

How many living species of arachnids are there?

Approximately 80,000 living species.

What is the significance of silk produced by spiders?

It is a fibrous protein that is stronger than steel and highly elastic.

What defines Myriapoda?

Includes various many-legged arthropods such as centipedes and millipedes.

What defines centipedes in the Myriapoda?

Predatory nature with one pair of legs per segment.

What do millipedes primarily consume?

Detritivores, burrowing in soil and litter.

What are Polyxenida?

Sister to all millipedes, soft-bodied and bristly.

How do symphylans differ from true centipedes?

They are soil-dwelling, non-venomous with a small size.

What insect order contains beetles?

Coleoptera.

What is the evolutionary significance of wings in insects?

They allow for adaptation and success in terrestrial and freshwater systems.

What limitation affects the size of insects?

Respiratory system efficiency is limited by size; diffusion distances increase with larger body size.

What are tracheal systems in insects responsible for?

Directly supplying oxygen to tissues via diffusion.

What group do spiders and scorpions belong to?

Cheliceriformes.

What describes the Cambrian period's relationship to arthropods?

It is when many forms of arthropods, including trilobites, were dominant.

What is Myriapoda's origin timeline?

Their origin dates back to the Cambrian period, around 520 million years ago.

Why are aquatic insects vulnerable?

They are particularly sensitive to climate change effects.

How many insect species are estimated to exist?

Insects have around 950,000 described extant species.

What factors contribute to insect success?

Body size, cuticle, flexible bauplan, evolution of flight.

What role does the cuticle play in arthropods?

It provides protection and helps in maintaining moisture.

What is an example of a Cheliceriformes adaptation?

The evolution of silk for web-building in spiders.

How does tagmosis affect arthropod evolution?

It leads to the functional specialization of different body segments.

What decline did trilobite species face?

They became extinct around 245 million years ago during mass extinctions.

What unique respiratory feature do some Myriapoda possess?

Tracheal 'lungs' connected to their pericardium.

Which arthropod group includes true bugs?

Hemiptera.

What conditions favor arthropod speciation?

Allopatric speciation in diverse and varied ecological niches.

What is the function of pedipalps in scorpions?

They are modified for sperm transfer.

What do the biramous limbs in crustaceans mean?

They are two-branched limbs, characteristic of many crustaceans.

How does one define ecological success in arthropods?

Ability to occupy diverse ecological niches and adapt over time.

What is unique about Holometabolous development?

It allows different life stages to exploit different ecological niches.

What ecological roles do arthropods play?

They act as pollinators, decomposers, and are key components of food webs.

What two groups of Hexapoda are the most diverse?

Coleoptera (beetles) and Hymenoptera (ants, bees, wasps).

What is a defining feature of insects in Hexapoda?

Three pairs of walking limbs.

What initiates the evolution of wings in insects?

Wings originated from leg exites that fused into the body wall.

What do the terms 'Ametabolous', 'Hemimetabolous', and 'Holometabolous' refer to?

They refer to different types of metamorphosis in insects.

What defines the ecological range of arthropods?

They occur in almost all habitats on Earth, from oceans to high mountains.

What sedimentary environment did ancient trilobites inhabit?

Palaeozoic seas.

What adaptation do scorpions exhibit for reproduction?

They produce stalked spermatophores for fertilization.

What is a chelae in scorpions?

It is a modified pedipalp that functions like a claw.

How has research led to the discovery of new insect orders?

Rapid descriptions of species lead to recognition of groups like Mantophasmatodea.

What significance does the diversity of arthropods have in evolution?

It reflects a long history of adaptation and ecological success.

What is a notable feature of the Lobster’s body structure?

Three tagmata: head, thorax (partly fused with head), and abdomen.

How do aquatic environments affect arthropod species?

They are vulnerable to climate change due to their ecological dependencies.

What percentage of animal biomass do insects make up in tropical forests?

Approximately 40% of animal biomass.

What does the term 'Pancrustacea' represent?

A subgroup of arthropods that includes crustaceans and hexapods.

What adaptation is prominent in Myriapoda?

Possession of numerous legs, with one or two pairs per segment.

What does 'Symphyla' refer to?

Small, long, non-venomous soil-dwelling arthropods resembling centipedes.

What ecological role do certain mites play?

They inhabit environments such as cryoconite ecosystems.

What is the common feature of arthropods' skeletal system?

It is made of chitin, enhanced by proteins and mineral salts.

What is true about the evolutionary origins of insects?

They originated around 390 million years ago, during the Devonian period.