3/28 Population Dynamics, Life Tables, and Life-History Trade Offs

Question 1

life tables purpose

Answer 1

to summarize the probability that an individual can reproduce based on age

Question 2

cohort

Answer 2

a group of individuals all starting something at the same time

Question 3

x (in life tables)

Answer 3

represents age class, first one begins at 0 (NOT 1)

Question 4

l sub x (life table)

Answer 4

• represents survivorship
• shows the ferquency of the original cohort surviving to age class x
• (n subx - n sub0)

Question 5

d sub x (life tables)

Answer 5

• mortality
• frequency of the original cohort dying during age class x
• (l subx - lsubx+1)

Question 6

Type 1 survivorship curve

Answer 6

• relatively high survivorship for almost entire lifetime of individuals
• lots of mortality at old age
• ex. people, elephants, blue whale, some plants

typified by having a large percentage of survivors throughout much of the individual’s life time, which is followed by a rapid decline in individuals within the cohort

Question 7

Type 2 survivorship curve

Answer 7

• steady decline over time
• ex. independent birds, perennial plants, trees

typified by a relatively constant decline in survivorship throughout the life of the species

Question 8

Type 3 Survivorship Curve

Answer 8

• extreme drop of survivorship very early in the lifetime of an average individual, but after, all that do survive have a high survivorship
• ex. annual plants, most invertebrates

typified by having a low survivorship (high mortality) early in the life of the organism, followed by a fairly high survivorship throughout the remainder of the lifespan

Question 9

What do survivorship curves do for population biologists and conservationists?

Answer 9

• pinpoint when in an organism’s life it is most susceptible to dying
• as a result, steps can be taken to ensure population survival if necessary
• also, in conjuction w life tables, the curve helps to pinpoint when during a species lifetime it is at its peak reproductive output

Question 10

fecundity vs. fitness

Answer 10

• both represent the number of offspring an individual can have in its lifetime
• fecundity represents an actual value, fitness is typically referred to in relative terms
• fecundity typically refers only to the # of female offpring a female can have in her lifetime

Question 11

Survivorship vs. fecundity

Answer 11

• equals the net/average reproductive rate of any one age-class
• if you add all these numbers together across all age classes, you get a net reproductive rate for the entire population (ignores immigration and emigration) aka the total average output on a per individual basis

Question 12

Sum of net reproductive rate of all age classes meaning (survivorship x fecundity column all rows added together)

Answer 12

• sum <1.0, the population is getting smaller
• sum =1.0, the population is staying the same
• sum >1, the population is growing

Question 13

life history

Answer 13

how an organism allocates energy and effort into processes such as growing, reproducing, and maintaining its body (not all of these things can typically be done at the same time)

Question 14

life history trade-off

Answer 14

the balancing act between living and growing and reproducing

Question 15

fecundity and survivorship relationship

Answer 15

• low survivorship typically has high fecundity (ex. mustard plant)
• high survivorship typically has low fecundity (ex. coconut palm)

the cost of reproduction is higher mortality

Question 16

phenotypic plasticity

Answer 16

• the ability of the organism to change how they live their life based on environmental conditions (fish example)