Life History Flashcards
Life cycles
(1) Gametic (2) Zygotic (3) Sporic
Gametic life cycle
Diploid individual, zygote Haploid gametes
Sporic life cycle
Diploid individual, zygote Haploid spores, gametophytes, gametes
Zygotic life cycle
Diploid zygote Haploid cells, individual
Which life cycle(s) have diploid individuals?
Gametic, sporic
Which life cycle(s) have haploid individuals?
Zygotic
Asexual reproduction
Clonal replication of individual
Sexual reproduction
Offspring reproduced from a combination of parents’ genetic material
To meet the goal of survival and reproduction, which life history makes more practical sense? Asexual or sexual reproduction?
Asexual. Requires less energy for sexual reproduction.
Life history
How an organism grows and produces offspring. A schedule of its life.
Principle of allocation
Organisms are limited in access to energy and resources and therefore must make trade-offs
What are measures of growth/ age structure?
(1) Demography (2) Life tables (3) Age distribution
Demography
Growth rate (r) = birth rate - death rate r = b - d
Life table
summarizes age-specific population demographic data (1) Dynamic/cohort (2) Static
Dynamic/cohort life table
Follows the lifetime of a cohort of individuals born at the same time
Static life table
Collect info for one point in time and use as representative data. The age of DEATH is recorded for a large number of individuals born at different times.
Age distribution
looks at the proportion of individuals in progressively older age classes to estimate survival, given that differences in the # of individuals from one age to the next is due only to mortality
If we started with 100 individuals, and at age 20 there were only 75 still alive, what is the survivorship (lx) for age class 20-30?
0.75
What is survivorship?
Survivorship (Ix) = #individuals alive at the start of an age class (Nx) / initial cohort size (N0)
What are the types of survivorship curves?
(1) Type I: die old (2) Type II: constant rate of survival/death (3) Type III: die young
Type I Survivorship
Type II Survivorship
Type III Survivorship
R Selection
- Species influenced greatly by per capita rate of increase (r)
- Rapid development, early reproduction, small body size, and many, small offspring.
- Type III Survivorship
- Unpredictable environments.
- Semelparity
K selection
- Controlling resources and competition with a population near its carrying capacity (K).
- Slow development, delayed reproduction, large body size, and few, large offspring.
- Type I & II Survivorship
- Stable environments.
- Iteroparity
Semelparity
has single reproductive episode before death
Iteroparity
has multiple reproductive cycles over the course of its lifetime.
What are the main environmental variables that dictate life histories in plants?
- Disturbance–mechanism that destroys plant biomass
- Stress–external constraints that limit productivity/growth
What kind of plants live under the following conditions:
- Disturbance = High, Stress = Low
- Disturbance = Low, Stress = High
- Disturbance = Low, Stress = Low
- Ruderals
- Stress Tolerant
- Competitive
Ruderal plants
- Grow quickly
- Reproduce rapidly
- Large numbers of seeds
Stress tolerant plants
- Grow slowly
- Conserve resources for periodic reproduction
- Low competition
Competitive plants
- Grow quickly
- Compete for resources
- Maximize competitive advantage
- later maturity
- large size
- larger offspring
