Graeme O'Neill Prof. Robert Page, founding director of the'School ofL.ife Sciences at Arizona State University, has spent 20 years investigating bee behaviour and its genetic underpinnings. He was intrigued that honeybee 'sisters', yvho shar�, live an.d.work together, exhibit such contrasting but
complementary behaviours late info their lives.
Page, a plenary speaker at the 2006 Lorne Genome Conference, says the division of labour is a hallmark of complex social systems, along with altrui$m - worker bees, which are all female, cede their repioductive privileges to their mother, the queen, and will lay down their lives to protect their sisters. He has been interested in how the division of labour during foraging evolved - and what light it can throw on the evolution ... of the honeybee social system.
Page says bees exhibit temporal polyethism - they change behaviours and specialisations as they age. The final transition involves a move from performing specialised tasks within the hive to foraging outside the hive. 'It's a very dramatic transition, involving lots of physiological changes, and 'requiring many genes to be upregulated or dowhregulated,' he says. Once they
\ \i \£US Preparation and Practice Reading & Writing - Academic
initiate foraging, they then tend to specialise either in collecting nectar or pollen. So first, they had to establish a division of labour between foraging and non-foraging bees, followed by a division of labour in the type of foraging.
'To a lesser extent, I'm interested in the evolution of the worker caste itself, because the females stay home to work for mother,' Page says. 'It's a black-box feature of complex insect societies - instead of going through a normal pattern of adult development, where they leave the nest, fly around and disperse, they stay home and engage in maternal behaviour.'
What has emerged from his research, says Page, is that bees that begin foraging slightly earlier in life specialise in pollen, while late starters tend to forage for nectar. Pollen foragers
are more responsive to low sugar concentrations than nectar-foragers, and are also more responsive to light. 'If certain QTLS are common to different sets of traits, something very fundamental must be going on,' Page says. 'If the same genes are affecting whole sets of traits, why are they linked?'
Page says he remembered his first course in insect physiology, where he learned about the gonotrophic cycle in the female mosquito, involving major changes in foraging behaviour. 'She goes from foraging for nectar to foraging for blood meals high in protein. Her behaviour is related to the state of her ovaries. As the ovaries change, and begin to produce eggs, her behaviour changes too. When she has a blood meal, she tunes into a different set of stimuli - she seeks body heat, avoids light, avoids contact with the ground and seeks out low, dark places where she just sits while her eggs mature. Now her behaviour changes again - she seeks out water vapour, and lays her eggs on the Water.'
Page says he wondered if bees had co-opted the ancient gonotrophic cycle into a system featuring specialised behaviours and division of labour. 'We looked at genes associated with the reproductive state, and knocked some out using RNA-induced silencing, and we were able to predict the resulting behavioural changes,' he says. 'For example, we found we could predict behavioural changes due to the gene knockouts, and we showed that the preference for pollen or nectar is related to the ancient gonotrophic cycle. So is the age of onset of foraging - bees performing different tasks get locked into them.'
By the time of the Lorne Genome Conference, Page and his colleagues will have published their latest findings in Nature.
'Going back to the solitary insect mode, we think what is happening is that the insect emerges from the cell without its ovaries activated, flies around and then disperses and mates,' he says.
'The ovaries are then activated by a hormonal signal involving ecdysone and juvenile hormone, and the ovaries become vitellogenic - they are ready to receive proteins produced from specialised fat-body cells and convert them into eggs.'
Page says this normally occurs after winter diapause, or a period of reproductive latency. The mosquito and bee have contrasting life histories - honeybees have pre-reproductive ovary activation, mosquitoes exhibit post-reproductive activation. 'In the honeybee, the hormonal signal to activate the ovaries occurs in the pupal stage, not in adulthood,' Page says. 'So when the honeybee emerges from its cell into the nest, it's not tuned for dispersing and mating. It has already undergone the equivalent of winter diapause or reproductive latency, and it's already in a maternal behaviour pattern.'
Part 1 Academic Reading: Unit 14 Academic Reading Practice Tests 119
'In the maternal. nest it's already responding to stimuli that would cause it to exhibit
maternal behaviours - it has cells to clean, food to process, larvae to feed,' Page says. 'It's all fundamental reproductive behaviour, but with the timing of the activation signal changed. 'In honeybees, it denies the worker the opportunity to have all those pre-maternal behaviours we see in the mosquito and other insects that lead solitary lives.'
The genes that set the· switches for these reproductive behavio.urs have not yet been cloned and studied in bees. Page says some likely candidate genes produce insulin-like signalling molecules similar to those found in humans. 'Now we have the complete genome sequenced from the honeybee, we can begin to identify candidate genes,' he says. He says natural selection has co-opted ancient patterns of behaviour in solitary insects and shaped them into unique patterns of social behaviour in bees.
QUESTIONS 27-30
Answer the following questions using NO MORE THAN THREE WORDS from the text. Write your answers in boxes 27-30 of your answer sheet.
27. As well as the division of labour, what is a key characteristic of complex social
systems? __________________ _
28. Who do female worker bees sacrifice their reproductive privileges for?
29. What term describes the way in which bees alter the way they behave as they get
older? ___________________ _
30. What two substances do bees harvest?---
QUESTIONS 31-35
Complete the following flow chart using NO MORE THAN TWO WORDS from the text. Write your answers in boxes 31-35 of your answer sheet.
Gonotrophic Cycle of Female Mosquito
Production of 32 ________ = requires 33 ______ -rich meals
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[continued from previous page]
QUESTIONS 36-40
Do the following statements match the information given in the text? In boxes
36-40
of your answer sheet, write:TRUE
if they match the information given in the text FALSE if they contradict the information given in the textNOT GIVEN
if there is no information about this in the text. 36. Page is primarily interested in why bees exhibit altruism.37. Nectar-foraging bees respond more to lights than pollen-foragers. 38. At the time of writing, Page's research had not yet been published.
39. Honeybees and mosquitoes have similar reproductive timing.
Task 1 gives some data, for example, a graph or a diagram. You must find the patterns and important points, and write a report. For example:
The charts below show the number of visitors arriving in a particular country for a short trip, and the number of residents leaving that country for a short trip, from 2009 to 2011.
Summarise the information by selecting and reporting the main features, and make comparisons where relevant.
Write at least 7 50 words.
660 640 620 --- 600 580 0 560 .:!::, 540 0 520 0.. 500 480
Oct-09 Feb-10 Jun-10 Oct-10 Feb-11 Jun-11 -Visitor arrivals Resident departures
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