APES Unit 3

Specialists: smaller range of tolerance, or narrower ecological niche makes them more prone to extinction

  • Specific food requirements

  • Less ability to adapt to new conditions

  • Narrow niche

  • More likely to become extinct

  • Use specific set of resources



Generalist : larger range of tolerance, broader niche makes them less prone to extinction and more likely to be invasive.

  • Broad food req.

  • High adaptability

  • broad niche

  • Less likely to become extinct

  • Use a variety of resources



K-selected and r-selected


K- selected - “quality”


Specialists


  • fewer offspring, heavy parental care to protect them 

  • Generally fewer reproductive events than r-strategists 

  • EX. Most mammals, birds

  • Long lifespan, long time to sexual maturity = low biotic potential = slow population growth rate 

  • More likely to be disrupted by environmental changes 



R-selected “quantity”


Generalist


  • Many offspring, little to no care

  • May reproduce only once, but generally reproduce many time throughout lifespan

  • Ex- insects, fish, plants

  • Shorter lifespan, quick to sexual maturity = high biotic potential = high population growth rate

  • More likely to be invasive 

  • Better suited for rapidly changing environment conditions



Deers 

  • About 1-3 offspring 

  • Mating season in the fall

  • Lifespan 10-15 years 

  • Reach sexual maturity around 1-2 years old 

  • Mother deer parent for around 6 months.


Survivorship curve: line that shows survival rate of a cohort (group of same aged individuals) in a population from birth to death

  • faster drop in line = quicker die off of individuals 

  • Slower drop in line = longer average lifespan


Type 1: specialists

Type 2: in the middle- every one species that dies one survives

Type 3: generalists 


Nature has different layers of complexity

  • Population: the individuals that belong to the same species and live in a given area at a particular time

  • Community: All of the populations of organisms within a given area

  • Population ecology: the study of factors that cause populations to increase or decrease


LEVELS OF COMPLEXITY: Environmental scientists study nature at several different levels of complexity, ranging from the individual organism to the biosphere. At each level, scientists focus on different processes

  • Individual

  • Survival and reproduction

  • The unit of natural selection


  • Population

  • Population dynamics 

  • The unit of evolution


  • Community

  • Interactions among species


  • Ecosystem

  • Flow of energy and matter


  • Biosphere

  • Global processes 


Populations have distinctive characteristics

  • Population size: the total number of individuals within a defined area at a given time 

  • Population density: the number of individuals per unit area at a given time

  • Population distribution: A description of how individuals are distributed with respect to one another

  • Sex ratio: the ratio of males to females in a population

  • Age structure: A description of how many individuals fit into particular age categories in a population


*Population size is affected by density-dependent and density-independent factors


  • Density-dependent factor: A factor that influences an individual’s probability of survival and reproduction in a manner that depends on the size of a population

  • Density-independent factor: A factor that has the same effect on an individual's probability of survival and the amount of reproduction at any population size

  • Population growth rate: the number of offspring an individual can produce in a given time period (minus the deaths of individuals or offspring)

  • Intrinsic growth rate (r) : The maximum potential for growth of a population under ideal conditions with unlimited resources

  • Exponential growth model (Nt= N0ert ) : a growth model that estimates a population's future size (Nt) after a period of time (t), based on the number of reproducing individuals currently in the population

  • J-shaped curve: the curve of the exponential growth model when graphed


The exponential growth model: When resources do not limit populations, their rapid growth can occur. More births occur with each step in time, creating a J-shaped curve


Population predictions: 

  • Goal: total count


Mark and Recapture


  1. Capturing individuals

  2. Mark them- then release 

  3. Capture…



Malthusian theory: 

  • Earth has a carrying capacity, based on food production

  • Human population growth is happening faster than growth of food production

  • Humans will reach a carrying capacity limited by food

Technological advancement:

  • Hummanhs can alter Earth’s carrying capacity with tech

  • Synthetic fixation leads to synthetic fertilizers, increasing the food supply


Growth rate: % increase in a population 

  • a growth rate of 5% of a population of 100 means they grow to 105

Crude birth rate and crude death rate

  • CBR and CDR

  • Births and deaths per 1000 people in a population

Calculating growth rate 

  • (CBR-CDR)/10

  • (20-18)/10

  • 1.2 percent

Rule of 70: the time it takes (years) for a population to double is equal to 70 divided by the growth rate

  • doubling time: 70/growth rate 


EX: a country has a CDR of 9 and a CBR of 18

 (18-9)/10 =0.9 - growth rate

70/0.9=77.778 


Total fertility rate: average number of children a woman in a population will bear throughout her lifetime

  • higher TFR= higher birth rate, higher population growt rate

Replacement level fertility: the TFR required to offset deaths in a population and keep population size 

  • about 2.1 in developed countries 

  • Higher in less developed countries

Infant mortality rate: number of deaths of children under 1 year per 1000 people 

  • higher in less developed countries 

Higher IMR = higher TFR


Factors in IMR decline

  • access to clean water

  • Access to healthcare ( hospitals, vaccines, vitamins, & supplements for moms and babies

  • More reliable food supplies