Adaption, Life History And Behaviour Flashcards
What is clutch size?
Number of eggs laid
What methodology do we follow in science?
Observation —> theory —> test
X
Observation = great tit clutch size is 8 or 9 eggs.
Testing adaption summary
- Assume optimisation
- Strategy set (options open to natural selection)
- Fitness consequences of different options (costs and benefits - what trade offs drive this adaption)
- What strategy yields the greatest fitness
What does assume optimisation/maximisation mean?
What is a good measure of fitness?
In the grate tir example this might be how many offspring in the clutch size do they manage to pledge successfully
Why does strategy set mean?
What are the different options of strategies that natural selection had to choose between?
(Eg. In great tits the different strategies natural selection could have taken are like it could have produced less eggs or more eggs in a clutch size etc) - 1-x eggs
Flaws with idea of fitness
Fitness doesn’t take into account reproductive value (could have high reproductive success with lots of offspring but these offspring are very weak)
How could you measure reproductive value in birds?
Look at how many offspring the mother managed to successfully fledge rather than how many offspring she produced at first
What does fitness consequences refer to in the great tit example?
And what is this called
More eggs you lay = more offspring you have to feed = more chicks of lower quality
(This is a trade off between the number and quality of offspring)
What is an evolutionary trade off?
When evolution cannot optimise one part of a biological system without compromising another part of it
What is meant by
X
Graph explanation
- survival doesn’t decrease much so great tit keeps producing more offspring
- eventually survival decreases so much that continuing to produce more offspring makes you do worse (I’m assuming because you just get lost of weak offspring so can’t pass on ur genes as well?)
Peak = maximum (3 is spring is maximum clutch size)
What is the lack’s theory of clutch size?
That the clutch size has been adapted by natural selection to be the largest number of offspring which the parents can on average provide enough food
More graphs
(a) as clutch size increases the average weights of chicks decreases
(b) = as chick weight decreases their survival decreases.
X
Observed is similar to predicted
Natural selection
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What is a hypothesis for why might birds lay less eggs than the lack clutch size? + example
Laying more eggs in one year might cost how many eggs you lay in future years
(Eg. Birds raise metabolism to feed their chicks so if they lay loads of chicks one year it may reduce their chance of surviving in future years because they are more physically exhausted Eg. Might become more prone to disease)
What is the trade off involved in why birds might lay less eggs than the lack clutch size ?
Trade off between current reproductive effort and how much you will be able to reproduce in future years
What kind of things can you experiment with, with great tits?
- how well a female survives if you add more eggs to her nest/ take away eggs
- ## add eggs earlier (adds cost of having to spend more energy incubating more eggs earlier)
What length of fitness matters
Fitness over a LIFETIME
What is a Darwinian demon?
Something amazing at everything:
- reproduced very young
- large
- reproduced lots of good quality offspring
Why does a Darwinian demon not exist?
Because of trade offs
What do you need to work out when you ask why something is how it is?
What the trade off is
Fitness
Maybe eating a male provides better nutrition?
Maybe eating a male means the female can produce more eggs?
Turns out neither of these affect the number of offspring the female can produce
Statistics of cannibalised male spiders and how it affects the female
When female spiders eat the male spider they are more likely to reject a second suitor
(Cannibalise male = 67% likelihood to reject suitor)
(Don’t cannabisme make = 4% likelihood to reject suitor)
Disadvantage if two males mate a female
Sperm competition to fertilise their eggs
Explain the statistics of offspring produced by female when the male is cannibalised vs not cannibalised
If the male allows himself to be cannibalised it means the female then doesn’t go on to mate a second suitor. This means that only that makes sperm fertilised the females egg so that 92% of her offspring are gathered by the male (have his sperm)
If the male isn’t cannibalised the female mates a second suitor meaning her offspring are a mix of both males’ sperm. The males not eaten only father 45% of the eggs (only 45% of the eggs were made with their sperm)
What is the real benefit of not being cannibalised?
None - If you aren’t eaten by the female the likelihood you will reach another web is low anyway (16%).
So you might as well be cannibalised because when you’re cannibalised there’s a higher percentage of the females offspring that you father
What is the winning strategy for spider mating?
Not Cannibalised = low (16%) likelihood you will reach another web and mate with a female
So you might as well just be cannibalised to maximise the number of offspring you produce (if cannibalised the female doesn’t mate with a second male so more of her offspring are made with your sperm)
What’s being maximised
What’s the strategy set
What’s the cost and benefit (trade offs)
Blue head wrasse
- Number of offspring produced will be maximised
- Strategy set - should you be a male or a female and when should you change sex
- What is the benefit of being a male or female at different ages?
When do blue head wrasse’s change sex usually
When females are older and larger
Female fecundity in the blue headed wrasse
Female fecundity (ability to produce abundance of fertile healthy offspring) increases with length
bigger is better when you are a female wrasse
Males
Mating success depends on size and age more strongly than females.
Because bigger males can defend reef and get lots of females.
Fitness consequences in the bluehead wrasse
Size and age have a huge fitness consequence
Sneaky fucker
Male bluehead wrasse behaves like a female so they can chick their speed onto the eggs of females i
Larger males have a ___ reproductive success compared to a small male
Larger (x40)
Switching sex
Females switch sex and become a male when it’s optimal (get the best of both worlds)
