Week 2 Flashcards
What must be the cause of behaviour?
Behaviour must stem from a genetic basis for it to evolve and be adaptive
What is the inherent nature of behaviour?
Evolution of behaviour are driven by individual based evolution, and are not for the good of the group or species
How can behaviour evolve?
Behaviour is genetically controlled, dynamic and heritable
Timespans of selection are sufficient for adaptation to occur
The it of selection is the individual and its genes (not the roup or the species)
What is an example of behaviour being selfish?
In 80s and 90s wildlife documentaries might say, a salmon swims up rive to produce thousands of eggs to help the species – however this is not how evolution works – selection acts on the individual salmon who will behave in this way for their own fitness not for the species.
How is phenotypic variation attributed to genotype variance?
Proportion of phenotypic variance in a population that can be attributed to genotypic variance
0 heritability = completely environmentally determined
1 heritability = completely genetically determined
0 – 1 = mix of environmental and genetic determination
What are examples of things that are different ends of the heritability spectrum?
Varies from 0 to 1. Religion conceivably 0, phenylketonuria (PKU) conceivably close to 1
Does heritability determine what proportion of a trait is determined by genes?
Heritability does not indicate what proportion of a trait is determined by genes and what proportion is determined by environment. So, a heritability of 0.7 does not mean that a trait is 70% caused by genetic factors; it means that 70% of the variability in the trait in a population is due to genetic differences among people.
How can we measure heritability?
Breed from female cow that produces lots of milk compared to a beef cow that was selected for meat
Go into the wild and determine if there is variation
We can screen for mutants and measure what causes the mutation
How can you find gene function through forward genetics in Drosophilia melanogaster?
Random mutagenesis in many fruit flies
Select phenotype of interest
Indentify responsibel gene
Stidy gene and properties and function
Identify and study related genes in mice
How did they determine whether mating speed in Drosophila melanogaster?
First example – drosophila are complex creatures, when they mate there is a lot of behavioral phenotypes. The males transfer as many as 200 seminal fluid proteins, some are used for cooperation, some are manipulative signals that benefit the male – the point here is that mating behaviour and copulation time is a complex behaviour.
Selected how long fruit flies mate for, x axis is number of generations of selection, y axis is mating time
What were the results of the selecting for long mating speeds in Drosophila melanogaster?
First example – drosophila are complex creatures, when they mate there is a lot of behavioral phenotypes. The males transfer as many as 200 seminal fluid proteins, some are used for cooperation, some are manipulative signals that benefit the male – the point here is that mating behaviour and copulation time is a complex behaviour.
Selected how long fruit flies mate for, x axis is number of generations of selection, y axis is mating time
What is an example of selective behaviour in rats?
Rats get much better at solving a maze – genetic component to something artificial yet simple
Is behaviour heritable?
Repeated selection experiments consistently show high heritability in animal behaviour
What is an example of heritable behvaiour in wild population?
Blackcap (Sylvia atricapilla) - A partial migrant warbler (some migrate some don’t) – main breeding population in Germany, and they either fly south east to Greece, or they go south west to spain for the winter (in both cases it’s warmer)
One population flies north west to the UK to overwinter – possibly to take advantage of food being put on tables
How can you measure migration behaviour in Sylvia atricapilla?
You can measure this migratory behaviour using emblem funnels – the bird can see the sky, and there is an ink pad at the bottom of the funnel, its restlessness and direction can be measured in this way – 80% show an increase in migration – so you can select for individuals to be more interested in migrating
Increasing migratory restlessness – can make it 100% or 0% using selection experiments
How did Sylvia atricapilla behaviour vary amogst groups in different populations?
Collect individuals from UK, these individuals want to migrate to UK towards the end of the summer, whereas if you take individuals from Germany they want to migrate to spain so individuals want to migrate their preferred direction
What happens if you bred Sylvia atricapilla together with different migratory patterns?
We can breed individuals from Spanish migrants with east European migrants –
Hybrids show migration that’s intermediate
You can see there is probably lots of genes as there is a huge amount of variation in the offspring ie its polygenic – which happens when you have complex and variable traits
What is the hertitability of behaviour?
Most behaviour is polygenic, and therefore some is genetic, but some of it is learned
What is the score of most behavioural heritability?
Rare for behaviour to be highly heritable, I mentioned height can be as much as 0.9, but behaviour is rarely more than 0.5, possible due to ease of measuring physical traits, but also due to strong environmental influences on the expression of behaviour
Can you find single gene examples for behaviours?
Very rare to find single gene examples (possible one in the honey bee)
What is an example of gene mutation impacting behaviour?
Dunce – it prevents fruit flies from learning
How did they experiment on flies and the behavioural response to smell?
Experiment encouraged flies to move into a chamber – and there are different smells in each chamber
A is a smell that is associated with a mild electric shock that the flies don’t like (coming from a circuit board in the tube)
B is a smell that does not cause a shock
Learn with 3 trial runs for each smell
So do they prefer to go to the shock odorant, or do they prefer to stay at the bottom – you can see that flies only like to fly to the smell that is associated with no shock
How did the dunce mutation impact the results of flies responding to smell that gave electric shock?
Dunce mutant flies forget that the odorant A is associated with a shock
How does the dunce gene work?
Dunce flies differ at one locus coding for phosphodiesterase enzyme
Phosphodiesterase metabolises cyclic AMP – important in nerve transmission
Nice example of a single locus that controls for learning
Natural selection would probably select out this gene in the wild as it is maladaptive
What is the cellular breakdown of Trichoplax adhaerens (placozoa)?
They haveonly six different types of cells, 98 million base pairs in their genome and digest their food outside of their body. This last is necessary because they have no internal organs, no brain or nervous system, no mouth, anus of digestive tract and no circulatory or excretory systems.
What is timeline of life?
Earliest known evidence of life: bacterial fossil impressions in rock in Western Australia ~3.6 billion years old
First eukaryotes ~2 billion years ago
First eukaryotic ‘animals’ ~1.5 billion years ago
First multicellular organisms evolved ~800 million years ago - probably Placozoa!!
First ‘backboned’ organisms evolved ~570 million years ago at the latest
