Quiz 2 (Lecture 8) Flashcards
life history
can be defined as the timing of, and investment in, growth reproduction, and survivorship
every patient has one
patients have life histories that
have evolved and that continue to evolve
human life history evolution now has both
medical causes and consequences
life history has successfully explained
why organisms are small or large
why they mature early or late
why they have few or many offspring
why they must grow old and die
Anything that influences ____ strongly influences ____
mortality and age of reproduction
life histories result from
the interaction of extrinsic and intrinsic factors
extrinsic factors influence
age- or stage-specific rates of mortality and reproduction (e.g. environmental factors like nutrition, disease, violence, medicine, public health…)
intrinsic factors include
tradeoffs among traits (phylogeny, genetics, development, and physiology all involved)
What does natural selection shape to maximize the positive difference between the benefits and costs of reproduction at different times?
age and size at maturity
4 assumptions about costs and benefits for age & size at maturity
- delaying maturity improves offspring survival
- delaying maturity improves offspring number
- earlier maturity shortens generation time
- earlier maturity shortens the period of risk (risk of dying) before reproduction begins
*organisms rarely live in unchanging environments
_____ is often better than a fixed rule
A flexible compromise
The reaction norm is
pattern of phenotypic expression of a single genotype across a range of environments
this idea that different phenotypes are produced by 1 genotype based on the environment
predicted age & size at maturity optimums
in good environments: mature young and large
in bad environments: mature old and small
historical study about age and size at maturity
when juvenile mortality decreases models predict the evolution of the reaction norm, favoring smaller size and earlier age at maturity
Pygmy example
- being short is the product of the adaptation
- stop growing early in life and can have babies really early, high adult mortality
when modern hygiene and medicine lower infant mortality rates,…
they reduce the evolutionary costs of earlier maturation, but the benefits of earlier maturation stay the same
With the costs of earlier maturation reduced and the benefits unchanged, maturation shifts to
earlier ages
- the entire reaction norm moves down and to the left
Framingham Heart study results in women
women are getting shorts and earlier reproduction age
-describes the biology of natural selection but culture is pushing women in other direction (have babies later)
Age of maturation is determined by tradeoffs between
infant mortality and age of mother
ex. of infant mortality and age of mother tradeoff
offspring of younger first-time mothers suffer higher mortality rates (that’s the tradeoff with juvenile mortality)
what evolves is not a fixed value of a trait but the _______, the reaction norm
entire plastic repsonse
patients are bundles of ___ that have been assembled by a process of tinkering with whatever was available that worked at the moment
tradeoffs
- not machines designed by an engineer
- not all of their parts can be replaced without consequences
tradeoffs require two connections:
- connections between 2 or more traits
- connections between those traits and fitness
A tradeoff only exists when
a change in one trait that increases fitness is associate with a change in another trait that decreases fitness
