The study of interactions between organisms and their biotic and abiotic environment
Studies population sizes and how and why they change over time
Investigates species interactions and how they affect species assemblages and organization
Studies energy flow and ecosystem structure as a result of the interaction between organisms and their biotic and abiotic environment
- Examines how local/regional interactions affect global changes in energy flow and species dynamics
- -climate change ecology
A group of individuals of the same species living in the same area
What information would you need to develop and demonstrate a successful restoration program for the California Condor?
- Info on what caused the decline
- Changes in population size over time
- Population requirements -> habitat, food, nesting resources
- *Population ecology focuses on these data
What caused the decline of the California Condors
- Lead poisoning from ingested bullets
- DDT (pesticide) caused a reduced shell thickness, so the mom's were destroying the eggs when they sat on them
How do you measure population size?
Mark-recapture method: capture and mark an initial set of individuals, release into the population, use the proportion of re-caught individuals in second capture to estimate total population
Mark-recapture method (Capture 1 vs Capture 2)
- In capture 2, catch a subset of the population
- There is an equal chance of catching marked and unmarked individuals: proportion of marked in capture 2 = proportion of marked in capture 1 to whole population
- Example: if you marked 6 deer and in capture 2 50% of them are marked then 6 deer = 50% of the total population
- Thus, total population = 12 deer
What allows assessment of changes in population size over time?
What variables control the population size?
- Individuals added to the population (birth/immigration)
- Individuals removed from the population (death/emigration)
Simplest model for patterns of population growth
- Change in population= births-deaths
- Use per capita birth rate and death rate: number of offspring produced by average member of the population per unit time & expected rate of death per unit time
- B= 50*(150/500)= 15 births
- D= 50*(50/500)= 5 deaths
Final Model Simplification using per capita population growth rate, r
- r= rate of addition of individuals per individual in population
You are studying a population of 2500 marmots. In a year, 315 marmot babies are born and 22 marmots die. Calculate r for this population.
C) r= 0.117
Marmot population 2: N= 9082
How many marmots will be added to this population at the end of year 1? At the end of years 2 and 3?
1062.6, 1186.9, 1325.8
Marmots added each year increased even though rate increased because N got larger each year
Exponential Growth Model
- Number of individuals added each time an interval increases as N increases in absence of factors limiting population growth
- Reflects the maximum possible population growth rate of a population based on their birth and death rates
Does the exponential growth model often occur in nature?
No because are limited resources for an unlimited population
Carrying Capacity (K)
The maximum population size that a given environment can sustain
Logistic Growth Model
- Population growth slows as it approaches carrying capacity
In logistic growth, what terms in the mode change as population approaches carrying capacity? Why?
- Population growth slows as population nears carrying capacity
- Fewer births bc inadequate resources to support pregnancy
- Increase in death
Density Dependent Population Effects
- Birth and death rates vary as a function of population sizes (environmental factors)
- Examples: food (less available as population increases), disease (more likely to spread as population increases), predation (easier to hunt as population increases)
Density Independent Population Effects
- Birth and death rates do NOT change as a function of population size
- Examples: extreme storms (kill everything in path irrespective of density), drought (all plants die irrespective of density)
What model is the human growth model
Exponential Growth Model
- % of the population that survives to a given age
- Equals # of individuals surviving to a given age/total individuals
- Plots the proportion of individuals still alive in each age
What is informative about species ecology?
Survivorship curves shows lifetime patterns of survival
Type 1 Survivorship Curve
- High survival rates until later ages
- Examples: Elephants/Humans
- -small amounts of offspring
- -high effort raising them
Type 2 Survivorship Curve
- Relatively steady chance of death throughout life
- Mortality does not depend on age
- Example: squirrels
Type 3 Survivorship Curve
- Very high mortality in early life but low mortality for older age groups
- Examples have large numbers of offspring without parental care
Have patterns of human survivorship changed over time?
How might these changes related to recent population growth?
- Yes, mortality rates have lowered
- Pre-1920s: much higher infant and child mortality because of lack of access to health care
How has the global fertility rate changed over time?
- The rate has started declining
- Some countries are opting to not have as many kids
How is the fertility rate associated with poverty and education?
- Fertility rate is higher in areas with more poverty and less education.
- This is because of large family farms (need more kids working) and high mortality rate
- Also, women who are educated have more economic power=less children
How does fertility rate vary from country to country?
- Poor, less developed countries have higher rates
- Women in Niger said average wanted childern = 7.2 or 9.2
What is the concern with the human growth rate?
- When and what is the human carrying capacity?
- This will cause deaths to increase and births to decrease.