Life Histories

why aren’t animals perfect?
1. natural selection does not require it
2. there are trade offs to everything
ie. giraffes height vs drinking, cheetahs speed vs rest, offspring # vs parental care
life history goal
to produce the largest number of SUCCESSFUL offspring
-must divide energy between growth, reproduction, # of offspring, and parental care
1. age at first reproduction – waiting and growing first means increased fecundity
2. how often to breed – semelparous vs iteroparous
3. how many offspring per episode
-devote more energy to growth
-more offspring
-less parental care
ie. salmon
-devote less energy to growth
-less offspring
-more parental care
ie. deer
probability of adult survival/prob. of juvenile survival
low = semelparous
high = iteroparous
r vs k selection
r = J curve, weedy or colonists organisms
small, short lives, type III, early breeding, semelparous, large clutch size, little parental care

k = S curve, better competitors
large, long life, late breeding, type I, iteroparous, small clutch size, lots of parental care