Population Ecology Flashcards
Definition of a population
Organisms of the same species that live in the same geographic area at the same time, with the capability of interbreeding
Definition of a community
An interacting group of various species at a common location
Definition of an ecosystem
Community of organisms + physical environment (biotic + abiotic)
Definition of population ecology
The study of changes in the sizes of populations of species over time
The alternations between measles and whooping cough is likely caused by ____ ____, where…
Ecological interference; Diseases directly compete for pool of non-immune human hosts
- As susceptible individuals die or become immune from one pathogen, competitor can establish
Herd Immunity refers to…
The protection offered to unimmunized individuals in a population/herd by a high percentage of immunized individuals
Disease elimination generally requires population vaccination rates of…
75% to 95%
Who are the most protected by herd immunity?
Infants too young for vaccination, individuals for whom vaccines are ineffective, and who are immune-compromised
4 Types of Traditional Vaccines
- Live-atenuated
- Inactivated
- Toxoid
- Recombinant protein
2 Types of Newer Vaccines
- mRNA
- Adenovirus
Live-attenuated vaccine
Uses a weakened virus (MMR vaccine)
Inactivated vaccine
Uses a dead virus (Annual flu vaccines)
Toxoid vaccine
Uses inert toxin (tetanus shot)
Recombinant protein vaccine
Uses a small part of the virus (HPV vaccine)
mRNA vaccine
Uses mRNAto get cells to produce the viral antigens (Pfizer and Moderna COVID-19 vaccines)
Adenovirus vaccines
Uses a carrier virus to deliver DNA (AstraZeneca and Johnson&Johnson COVID-19 vaccines)
Why are mRNA vaccines so fast to make?
- We can easily synthesize bits of mRNA
- We can easily sequence pathogen DNA or RNA
- We just need to change the mRNAbit to create the next vaccine.
What are some troubles with mRNA vaccines and how do we address them?
- mRNA is fragile and easily destroyed
- Disguise it and make it more like mRNA in the body - mRNA is a large molecule
- Package it in layered lipids and get the cells to “eat” it
Exponential growth model
delta N / delta t = rN, where r = per capita rate of increase, and N = population size
Logistic growth
delta N / delta t = rN[(K-N)/N], where K = carrying capacity
In a logistic growth model, as K increases, (____) will approach zero, and ____ ____ will also be approaching zero.
[(K-N)/N); population growth
Lotka-Volterra equations
*V = #prey, P = #predators
*b = prey birth rate
*a = predator attack rate
*r = predator birth rate
*m = predator death rate
- delta V / delta t = bV -aPV
- delta P / delta t = rVP - mP
SI model
Population of hosts assumed to be:
1. Susceptible to infection, or
2. Infected
and there is no immunity against the disease
Population: N = S+I
In a SI model, the rate of change for susceptible individuals depends on
- loss of susceptibles to infected population
- return of infecteds to susceptible population
In a SI model, the rate of change for infected individuals depends on
- Gain and loss of infecteds to susceptible population
SIR Model
Population of hosts assumed to be:
1. Susceptible to infection
2. Infected currently, or
3. Recovered from infection (and immune for lifetime)
And eventually there will be an immune decay that returns the R group to the S group
What is R0?
The mean number of secondary infections that a single infection will cause
When R0 > 1, the infection will ____;
When R0 < 1, the infection will ____ ____
spread; die out
