topic 11 - population growth

Question 1

how does population growth occur

Answer 1

from reproduction

Question 2

what is a population

Answer 2

all of the individuals of a given species that live and reproduce in a particular place

Question 3

what is population size

Answer 3

number of individuals alive at a particular time in a particular time

influenced by births, deaths, immigration, and emigration

Question 4

what is the change in total number of individuals in a population

Answer 4

delta N/delta t = dN/dt = B-D

N = total
B = births
D = deaths

Question 5

how to track per capita births and deaths

Answer 5

b = B/N
d = D/N

Question 6

what is the per capita growth rate

Answer 6

r = b-d = (B-D)/N

positive r = growing population
negative r = shrinking population

Question 7

how to calculate the change in pop growth

Answer 7

dN/dt = rN0

N0 = pop size at time 0

Question 8

how to determine size of population growing exponentially

Answer 8

Nt = N0 (1+r max)^t
just input numbers

Question 9

what is the exponential model of pop growth

Answer 9

under ideal conditions (organism given everything it needs)

per capita growth rate = max
intrinsic rate of increase = r max
r max = always constant and positive
(negative growth rate under these conditions = extinct pop)

Question 10

how does r max vary

Answer 10

high in bacteria
low in animals

decreases as generation time (in days) increases
depends on life history
- r-selected = higher r max
- k-selected = lower r max

Question 11

why does exponential behaviour occur in pops

Answer 11

new generation from t=1 can reproduce
(same as compound interest)

assumes that the same conditions are applicable to all generations and growth rate is the same over generations

Question 12

what is the effect of organisms not living in ideal conditions

Answer 12

limits pop growth (temp, precip, disease, food availability)

Question 13

what is the carrying capacity of an environment (K)

Answer 13

population size an environment can support

as population tends to approach carrying capacity, more and more comp, more individuals present than the environment can sustain = negative growth rate

as N tends towards K, r decreases

Question 14

what is the relationship between N and K

Answer 14

N>K - population size too big = r<0
N=K - r=0
N<K - r>0

as N increases, r decreases
small N = close to r max

Question 15

what type of equilibrium is a pop

Answer 15

stable equilbrium
- pop perturbed off equilibrium - tends back to K

Question 16

what is the logistic model of pop growth

Answer 16

as pops grow, death rates increase and birth rates decrease

bigger the pop = closer to carrying capacity, the more the growth rate slows down

r influenced by the fraction of carrying capacity available

Question 17

how to calculate the size of a population growing logistically

Answer 17

N t+1 = Nt(1+rt)

Question 18

how to calculate rt

Answer 18

rt = r max((K-Nt)/K)

Question 19

how is population growth influenced by density dependent factors

Answer 19

have an increasing effect as N becomes large (more individuals competing for the same things)

biotic factors:
- food
- shelter
- mates
- predation
- disease

Question 20

how does crowding (density dependent) influence reproduction

Answer 20

directly matches logistic model

tradeoff between the resources available and number of offspring

Question 21

how does crowding (density dependent) influence growth rate, adult size, and survival

Answer 21

growth rate (faster in lower density)
adult size (larger in lower density)
survival (longer in lower density)

Question 22

how is population growth influenced by density independent factors

Answer 22

effect all individuals regardless of density

abiotic factors:
- temp
- population
- disturbances

Question 23

how do r selected life history traits influence population growth

Answer 23

stay at the bottom of the curve
disturbance is common (more effected by abiotic factors)

Question 24

how to k selected life history traits influence population growth

Answer 24

strong competition
less disturbances
better survival through extremes