Lecture 7- Intro to population ecology Flashcards Preview

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What is a population?

-group of individuals OF THE SAME SPECIES! occupying a particular location
-attributes are: abundance, genotypes, sizes


What is a major aspect of predator prey relationship?



Explain the cycle of predator-prey population.

-have lot of prey= predator population will expand
-that will have a negative effect on prey= decline
-that in turn will decrease the population of predators
-and that will lead to prey increasing in numbers
= cycling like this
-Lotka-Volterra model says the same thing


Are the cycles of predator/prey often observed in real life?

-no only rarely
-there more interactions than just the predator prey relationship that change it


Give an example of a prey-predator relationship which follows the oscillations?

-hare and lynx in North America
-10 year cycle


What are the three practical reasons why knowing population dynamics is important?

-fisheries management (whale conservation)-how many can we catch sustainably
-conservation of endangered species (what do we need to do to increase their numbers?)
-pest/weed management(how to control their numbers, prevent outbreaks)


What is population dynamics?

-understanding and predicting changes in the abundance and distribution of organisms


What does B stand for?



What does D stand for?



What does I stand for?



What does E stand for?



What does Nt stand for?

-abundance at time t


What is the equation for abundance at t+1?

Nt+1= Nt+B-D+I-E
minus D and E as those are the ones leaving


What does f stand for?

f=fecundity (offspring per parent)


What does d stand for?

d= proportion of adults dying


How can we change the Nt+1 equation with f and d?

Nt+1= Nt + fNt - dNt + I -E
replaces B-D by fNt-dNt
can be rearranged:

Nt+1= (1-d)Nt + fNt + I- E


How can the already changed Nt+1 equation be changed by s?

Nt+1= sNt + fNt + I -E
replaced (1-d)Nt by sNt


What does s stand for?

-proportion of adults surviving


What do we have to measure to know Nt+1?

Nt, f, d(or s), I , E


How can you study abundance and distribution (3 ways)?

-snap-shots:describe what you see and where;try to infer explanations
-time-sequence: describe what changes you see over time, and infer explanations
-do experimental manipulations: observe responses (=changes over time)


How do we measure the population number Nt?

-census: count every individual in the population
-problems: hard to do, only get ones you can find


How do you count the Nt if there are too many to count (census)?

-sample the population
-count no. in each square and estimate from that
-get density=abundance in the area


What are the issues with population sampling?

-can't find all in the quadrat, if small, young etc.
-cryptic species= in soil, fish, hiding in soil


How do you measure population abundance in a lake?

-mark and recapture
-capture some= mark
-later again capture= and see how many are marked and unmarked= proportion= estimate abundance


How do you sample plant population where you can't see the single individuals?

-percentage cover of a quadrat
-also when unsure what is an individual= ramet= functional individual= what we can see