EEB 3408W Lecture Notes - Lecture 6: Commensalism, Natural Selection, Photosynthesis

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Natural selection favors one end of the spectrum or the other depending on the environment
Choice 1: make lots of babies and leave those to reproduce
Choice 2: make few babies
Life histories and lxmx
- 3 factors affect r
- Reduced age of first reproduction (sooner the higher the r)
- Increased litter size (number of seeds)
- Increase in the number of litters (number of years of seed production)
- Plants have a limited amount of resources to spend on growth, survival or reproduction
- There is a cost for females to produce offspring
- Is energy expended on mother or baby?
- Non reproductive females have lower mortality rates
- Lactating female do not have large fat reserves causing higher over the winter mortality
- Beech trees will have ‘mast’ years where they produce lots of seed and therefore grow
less
How should allocation trade offs be made in different environments?
When N is near 0; if 2 different morphs in the population had different r’s which morph will win?
- dN/dt = rN [1-(N/K)]
- When N is very high, there is a competitive environment
- Small differences in K really matter
- Can fit more individuals if they are very efficient
C-S-R theory = competition, ruderal and stress
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