Section 4 Flashcards
Research 4.3: Environmental Effects on ZEBRAFISH Aggression
1) Christoper Marks examined how water conditions during development affect aggressive behaviour in adult zebrafish
2) In the Himalayas, they live in either rich fast-flowing streams or oxygen-poor pools
3) Oxygen depletion can impact development and behaviour
4) Researchers raised closely related zebrafish in water that had either low or high oxygen levels and examined aggressive behaviour in adults when placed in each environment
ZEBRAFISH: Research Question
How does environmental variation affect aggression in zebrafish?
ZEBRAFISH: Hypothesis
Both developmental environment (DE) and behavioural (test) environment (TE) affect aggression
ZEBRAFISH: Methods
a) collected eggs
b) divided eggs into two developmental environments, normoxic or hypoxic
c) tested fish in either normoxic or hypoxic test chambers (16 hour acclimation)
d) measured aggression as time spent biting or nipping a mirror image
ZEBRAFISH: Results
Hypoxia-raised fish had higher levels of aggression in the hypoxic test chamber, and normoxia-raised fish had higher levels of aggression in the normoxic test chamber.
ZEBRAFISH: Conclusion
Zebrafish display more aggressive behaviour in the environment in which they were raised, indicating an interaction between developmental and behavioural environments
Research 4.3: Social Environment and Gene Expression in Fruit Flies
a) Lisa Ellis and Ginger Carney
b) Consider that behavioural interactions between two conspecifics often depend on the sex: male-male is aggressive, male-female involves courtship
FRUIT FLIES & SOCIAL ENVIRONMENT: Research Question
Why might differences in the social environment affect behaviour?
FRUIT FLIES & SOCIAL ENVIRONMENT: Methods
a) Used microarray analysis to examine gene expression in male fruit flies exposed to different social environments
b) Raised male flies and exposed them to one of two treatment groups or controls
c) One treatment group could court a single female while the other interacted with a rival male, 20 minutes
d) Control males did not interact with any fly
FRUIT FLIES & SOCIAL ENVIRONMENT: Results
a) Identified hundreds of genes that were socially responsive
b) 505 responded to male-male interactions and 281 responded to male-female
c) Most were found in both treatments but 240 were responsive to males only, 16 to females only
Songbird Background Context
a) All birds produce calls, which are innate
b) Many produce more complex vocalizations (songs) which are used to defend a territory and attract mates
c) In many songbird species, only males sing (in tropical species, both sing)
d) Song learning occurs in several stages, and species are either closed or open-ended learners
BIRDSONG DEVELOPMENT & SOCIAL ENVIRONMENT: Explain the difference between closed-ended learners and open-ended learners
Closed-ended: must hear a tutor sing its conspecific song shortly after hatching, a fixed sensitive period exists
Open-ended: can acquire new song elements throughout life
EXAMPLE: Zebra Finches are closed-ended learners
Research 4.3: Social Environment and Gene Expression in Birds
a) Brains of songbirds have enlarged and interconnected areas involved in song memory and production
b) Song System - an area of the brain, consisting of a posterior nucleus, which controls sound production, and an anterior nucleus involved in sound learning (Area X)
c) Exposure to conspecific birdsong causes many genes to be expressed in different regions of the song system
d) FOXP2 and ZENK
BIRDSONG DEVELOPMENT & SOCIAL ENVIRONMENT: Research Question
What is the role of the FoxP2 gene in birdsong development?
BIRDSONG DEVELOPMENT & SOCIAL ENVIRONMENT: Methods
a) FoxP2 undergoes increased gene expression in Area X of a bird’s brain both when young birds learn to sing and when open-ended learning adults change their song, suggesting FoxP2 plays a role in song learning
b) Reduced FoxP2 levels in Area X before young zebra finches began to learn their song
c) Knockdown technique involved using a virus to insert short sections of RNA into the FoxP2 gene at two different locations to reduce expression
d) Subjects were kept in a sound-isolation chamber with an adult male tutor during the critical period of learning
e) Sonograms were used to reveal number of song elements and characteristic features
BIRDSONG DEVELOPMENT & SOCIAL ENVIRONMENT: Results
a) In knockdown birds, FoxP2 expression was reduced by approximately 70%, which affected song development
b) Knockdown birds tended to omit specific syllables and failed to copy accurately the duration of some song syllables
c) Concluded that FoxP2 is required for normal song development
Gene-Environment Interactions
a) When G x E is present, we observe variation among genotypes in their responses to environmental variation
b) Now, phenotypic variation (VP) is a result of three factors: genotype variation, environmental variation, and variation from their interactions
Research 4.3: Rover and Sitter Foraging Behaviour in Fruit Flies
a) Marla Sokolowski’s work on the foraging behaviour of larval fruit flies
b) Fruit fly eggs develop during a series of larval stages, the larvae crawl to food source, eat, and then molt as they increase in size
c) Larvae exhibit two behavioural polymorphisms: rover and sitter
d) Rovers have longer foraging trails than sitters in the presence of food and are more likely to leave a food patch
e) Difference is due to different alleles at the “for” gene
f) 70% have the dominant rover allele “forR” while 30% are homozygous for the sitter allele “forS”
g) Polymorphism is maintained by frequency-dependent selection: rover allele has higher fitness in crowded conditions where they can benefit by traveling farther to find food and vice versa
h) In the absence of food, rovers behave like sitters since there’s no benefit to moving
i) Suggests a G x E interaction since rover behaviour changes strongly with environmental variation but sitters do not
ROVER & SITTER FORAGING IN FRUIT FLIES: Research Question
Do different behavioural polymorphisms in fruit flies exhibit gene-environment interactions?
ROVER & SITTER FORAGING IN FRUIT FLIES: Methods
a) examined the behaviour of groups of 25 to 30 adult rovers and sitters exposed to varying levels of food availability
b) half placed in holding vials that contained food for 16 to 18 hours before behavioural testing
c) other half were placed in a food-deprived environment
d) they examined the flies’ movement behaviour with a horizontal plexiglas maze
e) they placed the flies in a vial with food and allowed them to feed, before allowing them to leave the patch and move through the maze, empty glass vials were placed at all maze exits
f) recorded the proportion of flies in the collecting vials after three minutes
