Arthropods Flashcards
Lectures 15-18 (45 cards)
Name the 5 main reasons why Arthropods are so successful.
- Jointed appendages
- Exoskeleton (they are Ecdysozoa)
- Excretory system (Nephridia, similar to kidneys)
- Segmentation (Tagmosis, grouping together of some segments into larger units)
- Compound eyes
Name the layers of functions of layers of exoskeleton.
Epicuticle: Water resistant (made of proteins, lipids, wax etc)
Exocuticle: Sclerotised in some areas flexible in other. Made of proteins such as chitin.
Endocuticle: Mostly chitin with calcium
What are the benefits and costs of exoskeletons?
Benefits: Prevents water loss, strong but can flex and allow muscle contraction.
Costs: Limit on maximum body size and must moult and be flexible to grow larger.
Give a summary of Trilobites.
- Appeared in Cambrian (530 mya), disappeared in Permian (260 mya)
- Calcium carbonate exoskeleton (not cuticle)
- Biramous appendages (still present in Crustacea) made of outer region (exopod) and inner region (endopod)
What are chelicerates? When did some of the major groups appear?
Sea spiders, horseshoe crabs (445mya) sea scorpions (Extinct) and Arachnids (420 mya).
What are the feeding habits of the three extant groups?
Sea spiders: Eat micro organisms growing on submerged surfaces
Horseshoe crabs: Feed on worms and molluscs
Arachnids: Predatory, liquify prey before consumption. But there is a large variety in predation methods in Spiders.
Describe the segmentation of Chelicerata.
- Fused head and thorax (Cephalothorax)
- Two tagmata: Anterior prosoma, posterior opisthoma
Describe Pedipalps.
- One segment fewer than the legs, not used for locomotion.
- In males they are used for sperm transfer
- In scorpions they are pincers but in everything else they are sensory
How does gas exchange work in Chelicerata?
Book lung/gills. Looks like pages of a book.
- Large sa:v ratio
- Layers called lamellae
- Part of the exoskeleton
Name the 4 groups in Myriapoda.
Diplopoda (Millipedes)
Chilopoda (Centipedes)
Symphyla
Pauropoda
Give a summary of Diplopoda.
- Two legs per segments
- Detritivores
- Non poisonous
- Stink glands called ozopores
Give a summary of Chilopoda.
- One pair per segment
- Carnivorous
- Poisonous
- Venom claws called forcipules
Give a summary of Symphyla.
- 6 segment head, 14 trunk segments
- Legs on 12th-13th segments with silk swimming cerci
- Live in top of soil and are blind.
Give a summary of Pauropoda.
- Blind
- 11-12 segments with 9-11 leg pairs
- Forked antennae
- Feed on fungi, live in soil
Describe the basic Crustacean body plan.
Three tagmata
- Head
- Thorax
- Abdomen
(Sometimes only two as some have cephalothorax)
Give a summary of Xenocarida.
- Well developed brains and senses
- Live in aquafers and caves
What is the other small Crustacea group? Who are they more closely related to?
Oligostraca.
- Most related to Vericrustacea and Myriapods.
What are the three classes within Vericrustacea?
Branchiopoda (water fleas and fairy shrimp)
Maxillopoda (Copepods such as barnacles)
Malacostraca (Crabs, lobsters etc including Amphipoda, isopoda and Decapoda)
What are the two classes within Hexapoda?
Insecta and Entognatha.
Summarise Entognatha.
- Retracted mouth parts
- Many blind or simple compound eyes
- Wingless
How does gas exchange work in insects?
- Through trachea and branches airways of spiracles
- Limits body size but allowed for the colonisation of land
What are the three segment to insect digestive systems?
Fore, mid and hind gut.
What are the two types of hexapod digestive system?
- Phloem feeders: Consume too much water and sugar so Malpighian tubules remove these and produce honeydew.
- Desert insects: Don’t consume enough water so the Malpighian tubules are tightly bound to the rectum and extract much water as they can.
What muscles do insects use to fly?
Dragonflies and cockroaches: Direct flight muscles, attached to wing.
Most others: Indirect flight muscles, attached to thorax. Wings are pivoted.
