developmental adaptations

Question 1

what are some options insects can do to avoid unfavourable conditions

Answer 1

in environments which show seasonal fluctuations insects can either
1) move to more favourable sites
2) enter a dormant state during adverse periods e.g. diapause

= usually occurs before the unfavourable condtions occur- it is anticipated

Question 2

what often occurs in insects which migrate to avoid unfavourable conditions

Answer 2

usually enter a dormant period upon arrival

Question 3

what is meant by the terms diapause or quiescence

Answer 3

D = arrested development and adaptive physiological changes which come with development and continues with physiological stimuli rather than suitable conditions ,
= the cascade leading to this involves the signalling of several hormones . = varies in developmental stages, can be obligatory or facultative

Q = halted or slowed development as a direct response to unfavourable conditions

Question 4

what is meant by the term photoperiod and why is it significant for insects

Answer 4

the period of time each day during which an organism receives illumination; day length.

= predicts future seasonal conditions
= insects detect photoperiod with accuracy through the brain or photoreceptors in the eye
= hormones such as juvenile hormone and ecdysone also have a role

Question 5

outline what Dolekel 2015 found on photoperiodic time measurements in insects

Answer 5

As the earth orbits around the sun with its axis tilted the day-night ratio (photoperiod) changes
= many spp use this info for predicting adverse seasons
- varies at each development stage e.g. larval diapause, pupal and adult

= diapause complex adaptation to enviro stimuli, first photoperiodic info switches between diapause and reproductive programmes, once conditions favourable again return to usual development, input of favourable conditions relies on eyes and brain

Question 6

what is the aim of migration and why might it be a better developmental adaptation to diapause

Answer 6

diapause allows a break in development but migration provides an alternative by tracking resources in space
= it provides a continuous suitable enviro despite temporal fluctuations

Question 7

provide some examples of pre-migratory behaviours

Answer 7

redirecting metabolism to energy storage
cessation (end or bringing to an end) of reproduction
some cases production of wings

Question 8

what is meant by the term mass insect bioflows

Answer 8

around 3.5 trillion insects migrate above the region annually and recorded high flying (>150m) insects in southern UK
= higher biomass during the day time compared to night and least at dusk, since ~2006 recorded biomass decreased but is increasing again

• insects larger than 10mg tend to exploit seasonally beneficial tailwinds
  = may be the most important movement in terrestrial ecology

Question 9

compare the occurrence of diapause and quiescence in temperate and tropical areas

Answer 9

Temperate = periods of dormancy usually occur when enviro conditions become unsuitable

tropical = cues such as temp, moisture and changes in food quality dictate induction of diapausr

= can occur in summer (aestivation) or winter (hibernation) and may involve diapuase or quiescence

Question 10

what is meant by the term voltinism

Answer 10

the frequency or number of generations per year
= most take less than a year to develop
1 generation/year = univoltine
2 generations/year= bivoltine
>2= multi/polymultine

= rarley some take more than a year but this is known as semivoltine and is usually associated with colder temperatures or nutritonally poor conditions

Question 11

outline obligatory diapause

Answer 11

= insects which always enter diapuase, usually onse which complete only one generation a year enter at a fixed developmental stage regardless of conditions
- this is genetically programmed

= no mechanism to measure day length however enviro cues important for timing of end and the onset of development
= univoltine insects which elongate short life cycle to one year

Question 12

outline facultative diapause

Answer 12

= optional diapause e.g. to survive bad conditions such as food shortages
- found in most insects associated with bivoltine or multivoltine
= diapuase can last days, month or even years

Question 13

what is meant by reproductive diapause

Answer 13

occurs when metabolism is directed towards surviving environmental stress e.g. migration instead of reproduction

= photoperiod, temp, food quality, moisture, PH and chemicals can induce or terminate diapause

Question 14

outline the effects of climate change on diapause

Answer 14

altering the timing of diapuase on set and termination is critical for allowing insetcs to respond to climate change if not
1) may cause to enter to early or end e.g. over wintering diapause too early or late will be costly
2) in warming enviro photoperiod remains unchanged by temps elevate resulting in longer growing season and asynchrony between insetcs and host plants

Question 15

outline the effects of environmental extremes on development

Answer 15

• temp and humidity are main extreme enviro factors inducing insects
  = behavioural avoidance of extremes may be used e.g. migration, burrowing in soil, diapause, insitu tolerance

may cope using joint action of phenotypic plasticity and genetic adaptation but plastic responses limited and may not be enough to withstand warming trends

Question 16

outline how insects can withstand cold environmental extremes

Answer 16

= low temps produce phsyiological problems like desiccation due to freezing of body fluids which needs to be avoided

some insects possess a range of cryoprotection allowing survival in cold extremes e.g. Red flat bark beetle larvae can survive -80 degrees

Question 17

outline some methods of cryoprotection which can be used to withstand cold enviro extremes

Answer 17

1) POLYOLS AND SUGARDS = e.g. glycerol, trehalose and glucose are used to decreasing the insects supercooling point

2) HEAT SHOCK PROTEINS = bind to other proteins to protect them

3) ANTI-FREEZE PROTEINS = also decrease supercooling point

4) ICE-NUCLEATING AGENTS = act as sites for controlled freezing- dehydrates cell contents to avoid freezing

5) THERMAL HYSTEREIS PROTEINS = allow insect to build antifreezes and gain protection from freezing without disruptive increases in osmotic pressure which accompany the accumulation of polyols or sugars

Question 18

what is meant by supercooling and the supercooling point

Answer 18

polyols ,sugars and anti-freeze proteins allow supercooling without ice formation

1) supercooling = when liquid is cooled to temps below its freezing point and does not freeze

2) point= refers to the lowest temp to which an insect may be cooled before spontaneous ice nucleation occurs within body fluids

Question 19

outline what is meant by freeze intolerance/avoidance

Answer 19

=Freeze avoidance is a strategy where organisms prevent the formation of ice within their tissues by actively avoiding exposure to freezing conditions.
most common adaptation
e.g. lower supercooling point by production of antifreezes and heat shock proteins and the accumulation of cryoprotectants

= HIGH MORTALITY

Question 20

what is meant by freeze tolerance

Answer 20

Freeze tolerance is a strategy where organisms have physiological adaptations that allow them to survive the formation of ice within their tissues.
used more in areas of very cold temps and where freezing seasonal is extended
= produce ice nucleating and heat hsock proteins and accumulate cryoprotectants

=LOW MORTALITY

Question 21

What is meant by rapid cold hardnening

Answer 21

the almost instantaneous cold tolerance for brief exposures to non-lethal temps before the insect in a cold hardy state
= involves the build up of cryprotective compounds e.g. glycerol and polyols and improves tolerance to more sever temps as diapause needs a prolonged responce to cold temps this allows adaptation on short time scale

Question 22

outline how some insect spp survive heat enviornmental extremes

Answer 22

insects living in areas of high temps such as thermal springs (>50 ) risk denaturation and water loss

• BEHAVIOUR e.g. burrowing helps acclimation and gradual exposure to higher temps
• accumulate high level of heat shock/stress induced proteins prior to leaving the burrow

Question 23

outline how some insect spp survive arid enviornmental extremes

Answer 23

=greatest water loss via evaporation from the cuticle with some gas exchange from spiracles and excretetion

= some arid zone beetles reduce water loss by 100X by reduced cuticular loss, enclosure of spriacles and low Na+ levels indicating a lower metabolic rate
= uric acid precipitation allows all water to be reabsorbed

Question 24

outline the dangers of cold for aquatic insetcs

Answer 24

water is a great insulator and loses heat slower than land so temp stays relatively constant
- o2 levels high as cold water absorbs more oxygen
- thin layer of ice for short term cold isnt an issue as the bottom wont freeze so short term insects continoue to feed and have enough 02

• if long term ice then oxygen cant be absorved and depletes = death

Question 25

give some examples of species which undergo migration (insect)

Answer 25

1) painted lady = close to 150,000km round trip from tropical africa to the artic circle (six generations)

2) Red admiral = arrives in UK from S.Europe and N.africa

3) silver Y moth= North africa and sourthern europe each spring

Question 26

how do some insects prepare for winter

Answer 26

• build up energy reserves
• move to protective site e.g. soil, leaf litter, caccoons
• ## stag beetles spend most their life underground as larvae