BIOB50H3 Chapter Notes - Chapter L #6: Green Algae, Semelparity And Iteroparity, Agave Americana
CHAPTER 7: LIFE HISTORY (Lecture # 6), pages 160-170
INTRODUCTION
- An org. life history consists of major events related to its growth, development,
reproduction, and survival
LIFE HISTORY DIVERSITY (7.1)
- Life history studies are concerned w/ categorizing variation in life history traits and
analyzing the causes of that variation
Individual w/I species differ in their life histories
-Life history strategy: the overall pattern in the timing and nature of life history events
averaged across all the individuals in a species
Shaped by how org. divides its energy and resources between growth, reproduction,
and survival
a) Genetic Differences
- Some variation comes from genetics (eg. Genetically influenced traits can be recognized
w/I families)
Eg. Bluegrass traits such as age/reproduction/growth rate are similar among sibling
plants
-Heritable variation in life history traits is the raw material on which natural selection
acts upon
NS favours those whose LHT result in them having a better chance of survival
- Ecologists describe LH are optimal they are adapted to maximize fitness however:
no LH results in unlimited production of descendants (have constraints from trade-offs
and env)
b) Environmental Differences
-Phenotypic plasticity: single genotype may produce diff. phenotypes under diff.
environmental conditions
Eg. Animals and plants grow at diff. rates dep. On temp
-Changes in LHT often result in changes in adult morphology (eg. Lower temp = slower
growth = diff. in adult size/shape)
Eg. Tropical Ponderosa pine allocate more biomass to leaf growth relative to
sapwoods in deserts ponderosa pine desert pine are smaller w/ fewer leaves
-Allocation: describes the relative amounts of energy or resources that an organism
devotes to different functions
- Phenotypic plasticity respond to temp. variation and can produce dig. Sizes of an org.
other types of phenotypic plasticity can have a single genotype produce discrete types
(morphs) w/ few or no intermediate forms
Eg. Tadpoles in Arizona some are omnivores, larger ones are carnivores lead to
different relative sizes of body parts
oStudies show that they can turn into either types, depending on the food
they’re fed
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Document Summary
Chapter 7: life history (lecture # 6), pages 160-170. An org. life history consists of major events related to its growth, development, reproduction, and survival. Life history studies are concerned w/ categorizing variation in life history traits and analyzing the causes of that variation. Individual w/i species differ in their life histories. Life history strategy: the overall pattern in the timing and nature of life history events averaged across all the individuals in a species. Shaped by how org. divides its energy and resources between growth, reproduction, and survival: genetic differences. Some variation comes from genetics (eg. genetically influenced traits can be recognized w/i families) Bluegrass traits such as age/reproduction/growth rate are similar among sibling plants. Heritable variation in life history traits is the raw material on which natural selection acts upon. Ns favours those whose lht result in them having a better chance of survival.
