Spiders

Question 1

Araneae is an order the class what..?

Answer 1

Class Arachnida

Subphylum chelicerate and phylum arthropoda

Question 2

What are araneae?

Answer 2

Spiders, scorpions, mites+ticks, horse shoe crabs, sea spider

Spiders constitute 40000 out of 85000 chelicerates

Question 3

Chelicerates have

Answer 3

Two body segments, chephalothorax and abdomen, chelicerae, compound eyes

Question 4

Arachnids have

Answer 4

Fused cephalothorax with carapace, pedipalps, book lungs, four pairs of legs, carnivorous with liquid diet

Question 5

Spiders have

Answer 5

Silk, pedicel, poison glands, sperm transfer via pedipalp

Question 6

What are chelicerae

Answer 6

Mouthparts for feeding

Spiders cannot digest solid food

Often associated with venom

Hardening of tips with zinc ions

Question 7

Feeding:venom

Answer 7

Many produce venom

Diversity in chemical composition and effect

30 species have venom known to kill humans

Venoms can contain e.g. lytic peptides, enzymes, neurotoxins

Question 8

About the book lung

Answer 8

A feature of arachnids

Basal spiders have two pairs of book lungs

More derived spiders replace 1 pair of book lungs with separate trachea

Question 9

Silk

Biopolymers - like rubber, keratin, etc

Answer 9

Fibrous proteins
Primary sequence forms polymer chains held together by amide bonds
H bonds form between chains

Question 10

Primary sequences generally contain high proportions of what amino acids

Answer 10

Glycine and alanine

Long proteins are folded during silk spending and protein structure controlled by primary sequence and folding during spinning

Question 11

What is silk spinning

Answer 11

Pulling of silk strand begins the spinning process, and loss of water during spinning causes protein to change shape and H-bond to itself = protein denaturation

Question 12

Silk is stored as what

Answer 12

Stored as a liquid in the gland and forms a dry fibre during spinning

Question 13

Silk and feeding

Answer 13

Radial threads are strong and tough, to absorb prey impact energy without breaking

Capture spiral is stretchy and sticky for prey retention

Orb webs function to catch and retain prey - sit and wait predatory strategy

Question 14

Silk and sensory system

Answer 14

Spiders are vibration specialists and can control vibration propagation in orb webs

Question 15

Spiders have

Answer 15

Air borne vibration sensors - trichobothria
Substrate-borne vibration sensors - slit sensilla

Both are abundantly present on 8 legs
Slit sensilla sensitive to substrate vibration

Question 16

Silk and reproduction

Answer 16

Used by females to wrap up eggs

Used by males to make a sperm web - sperm is deposited onto web then transferred to pedipalps with a sperm reservoir
Pedipalp inseminates female

Question 17

Silk and locomotion

Answer 17

Spiders lay down silk as safety dragline
Araneomorph dragline silk and take spider’s own weight
Jumping spiders use silk to stabilise jumps

Question 18

Silk and dispersal

Answer 18

Spiderlings can use silk to balloon, silk line acts as a sail to allow spiders to fly
Enables dispersal away from egg laying site

Question 19

Spider diversity

Answer 19

Widely distributed (except Antarctica) 
Numerous - one hectare of UK meadowland contains 5 million spiders

Question 20

Sexual dimorphism

Answer 20

Sexually dimorphic in appearance e.g. peacock spiders and golden orb weavers

Differences in silk production and behaviour

Question 21

Similarites

Answer 21

Body form does not vary much

Question 22

What are the spider suborders

Answer 22

Mesothelae, Mygalomorphae, Araneomorphae

Question 23

What is the difference between Mygalomorph and Araneomorph

Answer 23

Mygalomorph have parallel fangs and araneomorph have opposed fangs (and have piriform silk), possess a silk comb and undergo ballooning

Question 24

Araneopmorph evolution

Answer 24

RTA clade inc. jumping, crab, and wolf spider families

Orbiculariae incl. orb weavers, money and cobweb spider families