Lecture 7- Intro to population ecology

Question 1

What is a population?

Answer 1

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

Question 2

What is a major aspect of predator prey relationship?

Answer 2

-oscillation

Question 3

Explain the cycle of predator-prey population.

Answer 3

-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

Question 4

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

Answer 4

• no only rarely

- there more interactions than just the predator prey relationship that change it

Question 5

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

Answer 5

• hare and lynx in North America

- 10 year cycle

Question 6

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

Answer 6

• 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)

Question 7

What is population dynamics?

Answer 7

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

Question 8

What does B stand for?

Answer 8

-births

Question 9

What does D stand for?

Answer 9

-deaths

Question 10

What does I stand for?

Answer 10

-immigration

Question 11

What does E stand for?

Answer 11

-emmigration

Question 12

What does Nt stand for?

Answer 12

-abundance at time t

Question 13

What is the equation for abundance at t+1?

Answer 13

Nt+1= Nt+B-D+I-E

minus D and E as those are the ones leaving

Question 14

What does f stand for?

Answer 14

f=fecundity (offspring per parent)

Question 15

What does d stand for?

Answer 15

d= proportion of adults dying

Question 16

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

Answer 16

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

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

Question 17

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

Answer 17

Nt+1= sNt + fNt + I -E

replaced (1-d)Nt by sNt

Question 18

What does s stand for?

Answer 18

-proportion of adults surviving

Question 19

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

Answer 19

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

Question 20

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

Answer 20

• 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)

Question 21

How do we measure the population number Nt?

-ideally

Answer 21

• census: count every individual in the population

- problems: hard to do, only get ones you can find

Question 22

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

Answer 22

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

Question 23

What are the issues with population sampling?

Answer 23

• can’t find all in the quadrat, if small, young etc.

- cryptic species= in soil, fish, hiding in soil

Question 24

How do you measure population abundance in a lake?

Answer 24

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

Question 25

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

Answer 25

• percentage cover of a quadrat

- also when unsure what is an individual= ramet= functional individual= what we can see