Ch. 9 Lecture Flashcards
Life History
life time pattern of GROWTH, DEVELOPMENT, and REPRODUCTION
Questions we ask about life history
- What age do individuals mature and reproduce?
- How many offspring are produced over a lifetime?
- How long do individuals live?
Life History Traits= ?
fitness components
What do we measure?
life history traits = fitness components
(SMORRGL)
- Size at birth
- Maturity (Age and Size)
- Offspring (Number, Size, and Sex)
- Reproductive Effort (Age-, Stage-, or Size-Specific)
- Rates of Survival (Age-, Stage-, or Size-Specific)
- Growth pattern
- Lifespan
Reproductive success influences populations!!!
Reproductive success influences populations!!!
The evolution of life histories involves…
trade-offs
What causes trade-offs in life history traits?
compensating for environmental variation is metabolically costly
Reproductive Effort
total energetic cost of reproduction per unit time
Herbaceous perennials reproductive effort
15-20% net production
Corn reproductive effort
35-40% net production
Common lizard reproductive effort
7-9% annual energy
Allegheny Mountain Salamander reproductive effort
48% annual energy
How does an organism distribute its limited resources?
- reproduce early v. later in life
- produce many smaller v. fewer larger offspring
What imposes trade-offs?
- Physiology
- Energetics
- Physical environment
- Biotic environment
Parental Care
Altricial v. Precocial
Altricial
require LONGER parental care because young are born somewhat HELPLESS
Precocial
require no or VERY LITTLE parental care because young are born relatively MATURE
Reproduction involves benefits and costs: Hypothesis
Behavioral, physiological, and energetic activities involved in REPRODUCTION REDUCES future reproductive success in the form of reduced SURVIVAL, FECUNDITY, and/or GROWTH.
fecundity
actual reproductive rate measured by number of gametes produced
age v. fecundity
age of reproductive maternity is a key aspect of life history. as age increases, cumulative number of offspring increases.
Cost of delaying reproduction
predation
extrinsic factors that can influence age of reproductive maturity and annual reproduction
- winterkill
- predation
- reabsorb fetus if conditions unfavorable/dominant male present
Phenotypic Plasticity
ability of an individual to change form under different environmental conditions
trade-offs between number and size of offspring
each offspring takes resources, which are limited.
-size at birth v. survivorship
timing v. number of reproduction
semelparous v. iteroparus
semelparous
reproduces once in life and then dies (insect)
iteroparus
reproduces multiple times over a life time (shark)
organizing life history traits
k-selected v. r-selected species
r-selected species
- small size
- fast development
- reproduces early in life
- many small offspring
- fast pop. growth rate
- no parental care
- weak competitive ability
- variable pop. size, below carrying capacity
- variable and unpredictable mortality
k-selected species
- large size
- slow development
- long lived
- reproduces later in life
- few large offspring
- slow pop. growth rate
- parental care
- strong competitive ability
- constant pop. size, close to carrying capacity
- constant and predictable mortality
r-selected->k-selected spectrum
bacteria > mollusks > insects > fish > amphibians > reptiles > mammals > humans
