physiology of foraging

Question 1

what are the two states of food acquisition

Answer 1

finding food and securing food

Question 2

how can food be located

Answer 2

by chance encounter or active hunting

Question 3

how does the star nosed mole find food

Answer 3

an exaggerated touch sense using Eimer’s organs which cover appendages and sense touch through exposed nerve endings, merkel cells and lamellated corpuscles

Question 4

how do bats use echolocation

Answer 4

changes in amplitude/timing between ears is directional. doppler shift detecting change in frequency tells it if the object is moving closer or away

Question 5

how do bats generate calls

Answer 5

contraction of the larynx muscle. it becomes more rapid during buzz phase as it approaches its target

Question 6

how are bats adapted to hear calls

Answer 6

funneled auricles and motor protein prestin which is on the basilar membrane and detects high frequency sound

Question 7

who uses electrolocation and what does it sense

Answer 7

used by sharks and rays. they detect electrical fields generated by muscle contraction of prey

Question 8

how is electrolocation detected

Answer 8

impulses travel through conducting gel- filled canals to stimulate ampulla of Lorenzini (sense organ). impulses are sent straight to the brain

Question 9

what is IR

Answer 9

infrared ratiation with wavelength 700nm-1mm. most thermal radiation is IR

Question 10

how do pit snakes detect IR

Answer 10

innervation of the pit membrane by trigerminal ganglia neurones which are rich in temperature- sensitive TRPA1 ion channels

Question 11

how do pit snakes visualise IR

Answer 11

impulses from TG neurones converge with optic nerve impulses in the optic tectum so they ‘see’ IR

Question 12

how do vampire bats detect IR

Answer 12

similarly to pit snakes with pit organs, however they use a short isoform of TRPA1 (TRPA1S) which is more temperature sensitive

Question 13

how do vampire bats prevent self detection and why is this necessary

Answer 13

their nose (where the 3 pit organs are) is 9 degrees colder than the rest of the face. this is necessary as bats are warm blooded mammals

Question 14

what are the three mechanisms of securing a meal

Answer 14

physical, electrical and chemical

Question 15

how is spider silk formed

Answer 15

it forms micelle- like structures in the sac. a reduced pH in the spinning duct elongates proteins and forms fibres

Question 16

which form of silk is most valuable in predation

Answer 16

swathing silk- around 300 aciniform glands simultaneously form a silk ‘sheet’ to wrap prey

Question 17

what is the structure of electric organs

Answer 17

they are filled with stacks of around 5000-6000 electrocyte disks which have two distinct faces

Question 18

how is a potential difference generated in electric organs

Answer 18

one face of the disk is depolarised and the other is polarised. the summative potential difference of the organ is around 860V

Question 19

what is the composition of venom

Answer 19

it is made up of neurotoxins, enzymes and pore forming toxins

Question 20

what do neurotoxins target

Answer 20

fast- acting proteins ie ion channels. these include Na, Ca, K, nAChR and iGluR

Question 21

what are peptide neurotoxins

Answer 21

small peptides which have lots of disulfide bridges due to high quantities of Cys residues. they target all types of ion channels

Question 22

which ion channels cause which paralysis in peptide neurotoxins

Answer 22

K and Ca cause rigid paralysis, Na, nAChR and iGluR cause flaccid paralysis

Question 23

which ion channels cause which paralysis in non- peptide toxins

Answer 23

Na, Ca, nAChR and iGluR all cause flaccid paralysis

Question 24

how is venom stored

Answer 24

as pro- venom to prevent self toxicity. it is enzymatically modified at release to become active

Question 25

how is venom usually delivered

Answer 25

by fang, sting or modified leg. they have modified elongated holes/ deep grooves to prevent blockage or venom ducts

Question 26

how do cnidarians deliver venom

Answer 26

toxic harpoons. they are stored inside out in nematocysts and are triggered by cnidocil touching prey

Question 27

how do cone snails paralyse prey

Answer 27

in a two step paralysis- rigid then flaccid. they use toxic harpoon called radula