Lecture 8- K and r selected species Flashcards Preview

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WHat are two types of population growth models?

Exponetial growth model and logistic growth model


Exponential growth model

No limits to population growth, where r is at its maximum value (brief periods)


Logistic growth model

Limits to pop growth, pop size fluctuated aroung K (longer periods)


What are life history strategies?

A suite of traits a species uses to maintain (or increase) its pop size (includes longevity, parental care, size and number of offspring, age of maturity, # of reproductiove epidsodes in a lifetime)


What are characteristics of K selected species?

Stable environments
Strong competitors
Long lives, few offspring, large in size


What are characteristics of r selected species?

Unstable environments
Poor competitors
Shorter lifes, many off spring, small in size


What is a life history model for plants? who developed it?

Grime developed the CSR model, stress and disturbance affect growth and reproduction of vascular plants


What are some traits of competetive plants?

Rapid growth
High phenotypic plasticity
Low rates of seed production/long lives


What are some traits of stress-tolerant plants?

High nutrient retention
Slow growth
Long-lived leaves
Low rate of seed prod
Long life span


What are some traits of distubance-tolerant plants?

Small size
rapid growth
high rates of seed prod
Short life span


What is demography

Scientific study of population descriptive traits (size, age, growth rate, distribution, age) and factors that cause changes in the pop size (B,D,E,I)


What are different types of life tables?

1. cohort- age specific (actively follow a cohort throughout its life)
2. Static- time specific- (age distribution data are collected in one moment of time


What are the 5 assumptions of static life tables

1. Individuals have same prob of being sampled
2. Ages are assessed accurately
3. Survival and Fecundity rates may change with age, but not over time
4. Age distribution does not change over time
5. Population size does not change over time


What are some benifits and costs of cohort life tables

B: very accurate, ages are known, track changes in pop through time
C: Time and resource intensive


What are some benefits and costs of static life tables?

B: only requires data from one time period
C: assumptions are rarely met, relies on accurate aging


What two variables do you need data for to construct life tables?

1. Age specific Survivorship (lx)
2. Age specific fecundity (mx)


How do we obtain life table data?

-Generation Time


What is Generation time?

Mean time between birth of a female and a birth of her offspring


What is net reproductive rate? (Ro)

Mean number of female offspring produced by a female during her lifetime


What do semelparity and iterparity mean and how are they different?

Semel parity an individual reproduces once in its life, iteroparity an individual reproduces multiple times in its life. G has large effect on r ( r declines as G increases)


Why are life tables important to management and population ecologists?

help identify the ages at which survival/fecundity is particularly low or high. this can be used to focus harvest on particulcar age classes to achieve desired management outcome


What are the 3 types of survivorship curves?

Type 1. low mortality for most of life, high mortality in older individuals
Type 2. constant rate of mortality throughout life
Type 3. High mortality of younger individuals, then low most of life


What 3 factors mainly influence r?

1. # of offspring at each reproductive event ( more= higher r)
2.# of reproductive events (more = higher r)
3. Age at first reproduction (younger = higher r)


What is population regulation?

Factors that affect vital rates (reproduction, growth, survival) and therby regulates pop growth


What is Density independant factors?

How much these factors affect r is independant of pop density (weather, habitat disturbances, density independant disease (cancer)


What are Density-Dependant factors?

how much these factors affect r depends on pop density (food, space, parasites)


What is negative and positive density dependence?

(-) as pop increases some factors leat to lower vital rates, crowding leads to competition, and incresed disease transmission
(+) When pop is low, some factors lead to higher vital rates


What are the two types of mortality?

Compensatory mortality- Causes no reduction in total survival (harvest compensation for starvation)
Additive mortality- Cause an immediate reduction in total survival (harvest is additive to all other sources of mortality)


What is a Sink population?

population where r<0 (population relies on immigration from source populations)


What is a source population?

Pop where r>0 (dispersal of surplus individuals can provide a source for sink pop)