Lecture 20 Flashcards
what is the eq for pop growth?
delta N / delta t = births - deaths + immigrants - emigrants
What is the eq for the rate of change in pop size
delta N / delta t = rN
r = b-d
r = rate of increase per individual
b= birth rate
d= death rate
When does exponential growth happen in pops
- only occurs in pops with unlimited resources that are able to reproduce at a max rate, after:
a) introduction to a new environment
b) recovery from a disaster (few competitors)
What is the eq for exponential growth
dN/dt = rN
differential rate eq in calc, where growth rate is independent of density
explain what happened during the mouse plague in australia 2021
- wet year with high grain harvest
- lots of stored wheat that was invaded by mice that can produce new offspring every 3-4 weeks
- invading houses in search of more food as competition for food increases
What does the carrying capacity (k) mean?
- max number of individuals that a particular environment can support
- k is affected by the availability of resources (ex. light, nutrients, water, territory, nesting sites, etc) and provides a limit to continued pop growth
ex. damaged coral reef = very low k for fish
productive reef = high k for fish
explain logistic growth
- as a pop approaches k, density dependent factors will affect b and/or d, and N and other parameters.
Either:
- intraspecific (within species)
- interspecific (between species)
ex.
- competition for resources
- behavioural changes like conflicts, reproduction declines, infanticide, cannibalism
- disease or predation
- creates logistic curves!
- gwhat is the eq of a logistic growth curve?
dN/delta t = rmaxN * (k-N)/k
when N is small, expression is close to 1 bc (1000-10)/1000 = 0.99 and exponential growth continues
when N is large, (1000-900)/1000 = 0.1, the expression gets smaller and slows the rate of growth (by 90%)
when N is at carrying capacity (k=N), the expression is 0, and growth stops
What affects the carry capacity of humans? how can we increase k?
- food production capability (increase k!)
- increase agricultural areas? fish farms? greenhouse areas in non-arable land? etc.
BUT
all solutions have consequences, especially for non-humans
What is the current global average fertility rate?
- 2.5 children per woman
- above the replacement rate of 2.1 children per woman, which replaces her and one male
explain Anthropocene!!!
- an Earth whose future is controlled by activities of the human pop
- maximizing k for humans will have negative effects on most other species