developmental adaptations Flashcards
what are some options insects can do to avoid unfavourable conditions
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
what often occurs in insects which migrate to avoid unfavourable conditions
usually enter a dormant period upon arrival
what is meant by the terms diapause or quiescence
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
what is meant by the term photoperiod and why is it significant for insects
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
outline what Dolekel 2015 found on photoperiodic time measurements in insects
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
what is the aim of migration and why might it be a better developmental adaptation to diapause
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
provide some examples of pre-migratory behaviours
redirecting metabolism to energy storage
cessation (end or bringing to an end) of reproduction
some cases production of wings
what is meant by the term mass insect bioflows
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
compare the occurrence of diapause and quiescence in temperate and tropical areas
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
what is meant by the term voltinism
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
outline obligatory diapause
= 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
outline facultative diapause
= 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
what is meant by reproductive diapause
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
outline the effects of climate change on diapause
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
outline the effects of environmental extremes on development
- 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
outline how insects can withstand cold environmental extremes
= 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
outline some methods of cryoprotection which can be used to withstand cold enviro extremes
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
what is meant by supercooling and the supercooling point
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
outline what is meant by freeze intolerance/avoidance
=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
what is meant by freeze tolerance
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
What is meant by rapid cold hardnening
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
outline how some insect spp survive heat enviornmental extremes
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
outline how some insect spp survive arid enviornmental extremes
=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
outline the dangers of cold for aquatic insetcs
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
give some examples of species which undergo migration (insect)
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
how do some insects prepare for winter
- build up energy reserves
- move to protective site e.g. soil, leaf litter, caccoons
- ## stag beetles spend most their life underground as larvae
