Population Dynamics

Question 1

survivorship curves

Answer 1

• describe the life history of a species
• has a characteristic shape for each species depending on typical life expectancy at each age

Question 2

type III survivorship

Answer 2

most individuals do not survive very long past birth
R-selected: their life history prioritizes reproduction which produces many small offspring to maximize the chance that some will survive
better adapted to unstable environments

Question 2

type II survivorship

Answer 2

mortality doesn’t change with age

Question 3

type I survivorship

Answer 3

• reflects a higher mortality rate in old age vs. young
• K-selected: larger bodied and take longer to grow to maturity and a reproductive age so there are fewer, larger offspring
• parental care and parental investment
• populations tend to be influenced by carrying capacity and do better in stable environments

Question 4

type I conservation

Answer 4

• avoid killing adult individuals
• species that take a long time to reach sexual maturity are slow to bounce back from the loss of a breeding population
  ex: sharks, whales, tortoises, elephants, mountain goats
  ex: atlantic bluefin tuna spawn once a year and do not reach reproductive maturity until 8-12

Question 5

type III conservation

Answer 5

• avoid killing young individuals
• species that reproduce in their first year need to survive infancy
  ex: marine invertebrates with planktonic larvae, amphibian eggs and tadpoles, insects
• conservation can be more difficult as their survival depends on climate

Question 6

life table

Answer 6

summarizes demographic date
cohort: group of individuals born at the same time period or year
cohort life table: tracks what happens to a cohort over time given constant conditions

Question 7

survivorship

Answer 7

fraction of individuals that survive to a given age
Lx
Nx/N0

Question 8

fecundity

Answer 8

average number of offspring the average individual produces at each age
mx

Question 9

net reproductive rate of a population

Answer 9

• sum[lx * mx]
• R0
• in its whole life, how many offspring on average an individual will add to the population
• brings together likelihood of surviving to a certain age and the average number of offspring at that age

Question 10

reproductive rate

Answer 10

in any year of life, this is how many offspring each individual that was originally born will add to the population

Question 11

generation time

Answer 11

• average age of parents in the population
• G
• [sum(lx * mx * x)]/R0

Question 12

intrinsic rate of increase

Answer 12

• how many individuals are being added to the whole population at any given moment
• how fast the population is growing
• r>0 = growing r<0 = shrinking
• r = [ln(R0)]/G

Question 13

exponential growth using instantaneous growth rate

Answer 13

Nx = N0 * e^rt
- instantaneous, continuous, or per captita growth rate is the amount by which the population is increasing at any given moment per individual
- only occurs when the number of organisms is well below K

Question 14

carrying capacity

Answer 14

number of individuals that can be supported by a particular environment
K
depends on density dependent factors

Question 15

logistic model

Answer 15

forms at N -> K

Question 16

density dependent factors

Answer 16

most decrease r as N grows
- intraspecific competition: more individuals competing for limited resources
- predation: large groups attract more predators
- disease and parasites: large group increases likelihood of transmission
- always why r increases when N is low, so why exponential growth occurs

Question 17

predation

Answer 17

density dependent
- predators may target a more densely populated area of prey
- when prey population is high, predator population is also high, so prey population will become lower, which leads predator population to become low, which leads prey population to be high

Question 18

allee effect

Answer 18

describes how r may decrease when N is low
- larger groups increase your chance of finding a mate
- large group social behavior increases your chance of obtaining food or being eaten
- therefore, some density dependent factors increase r as N grows

Question 19

density independent factors

Answer 19

effect does not change with N
have a consistent effect on populations at any N
do not contribute to carrying capacity

Question 20

population density

Answer 20

affects how rapidly a population can grow