Bio 108 topic 24

What makes Arthropoda the most species-rich animal phylum?

It includes the highest number of described species due to its body plan and adaptability.

Key traits of arthropods?

Segmented body, jointed appendages, sclerotized exoskeleton, cephalization, reduced coelom (hemocoel), open circulatory system.

What evolutionary trends are seen in arthropods?

Fewer segments, increased appendage specialization.

What are tagmata?

Functional units formed by fused body segments with specialized functions.

What is a sclerotized cuticle?

A hardened chitinous exoskeleton; sometimes biomineralized.

Difference between biramous and uniramous limbs?

Biramous = 2 branches (common in crustaceans); Uniramous = single branch (typical of insects, myriapods).

What are trilobites?

Extinct marine arthropods with many biramous limbs and segmented bodies (Cambrian).

What are chelicerae?

Claw-like feeding appendages anterior to the mouth.

Tagmata of chelicerates?

Cephalothorax (with carapace, 6 pairs of appendages) and abdomen (no appendages).

What are pedipalps?

Second pair of appendages; sensory or for prey handling.

Key spider traits?

Venomous chelicerae, silk-producing spinnerets, fluid feeding.

Scorpion traits?

Grasping pedipalps, segmented abdomen, venomous sting.

Mite traits?

Tiny, fused tagmata; highly diverse diets and habitats.

Characteristics of myriapods?

Terrestrial, long trunk with many legs, less tagmatized, tracheal respiration, direct development.

Millipedes vs. Centipedes?

Millipedes: detritivores, 2 pairs of legs/segment.

Centipedes: carnivores, 1 pair/segment, poison claws.

Common crustaceans?

Crabs, shrimp, lobsters, isopods, etc.

Tagmata in crustaceans?

Head, thorax, abdomen (head + thorax often = cephalothorax with carapace).

Crustacean appendages?

Biramous limbs; head with 2 antennae pairs, mandibles, maxillae; thoracic & abdominal limbs for movement, feeding, gas exchange, etc.

Crustacean respiration?

Gills or cuticle (marine); tracheae (terrestrial).

Reproduction in crustaceans?

Separate sexes; copulation or spermatophore; direct or indirect development.

What defines Hexapoda?

6 uniramous legs, typically 3 body segments (head, thorax, abdomen).

Insect respiratory system?

Tracheal system.

Apterygote vs. Pterygote insects?

Apterygote = wingless (primitive); Pterygote = winged (derived).

How did wings affect insect success?

Enabled flight, aiding dispersal and diversification.

incomplete vs. Complete metamorphosis?

• Incomplete: nymphs resemble adults; no pupal stage.

• Complete: larva → pupa → adult; major transformation.

How is sperm transferred in hexapods?

A: Apterygotes: spermatophores (indirect). Pterygotes: copulation via intromission (direct).