Population Ecology

Question 1

Population

Answer 1

• a group of individuals of the same species that live in the same area at the same time
• and potentially interact with each other
• defining borders of a population can be difficult

Question 2

Metapopulation

Answer 2

a population of populations connected by migration (gene flow)

Question 3

Range of species

Answer 3

• different scales
• populations are displayed in a patchy way depending on the suitability of the environment
• as you zoom in there are more and more populations

Question 4

Population Density

Answer 4

the number of individuals per unit area

Question 5

Population Dispersion

Answer 5

• how individuals are distributed relative to one another

- 3 main types: Random, Clumped, and Uniform

Question 6

Random Dispersion

Answer 6

• an individual has an equal probability of occurring anywhere in an area
• e.g. a field of dandelions have wind dispersion

Question 7

Clumped Dispersion

Answer 7

• individuals are closer than expected by chance
• if natural selection has favored being close to another individual
  e. g. schools of fish reduce the chance of predators eating an individual

Question 8

Uniform Dispersion

Answer 8

• relatively equal spacing among individuals
• maximize space
• if natural selection has favored being farthest away from each other
• e.g. plants in the desert are uniformly spaced because their roots are competing for water in the soil

Question 9

3 Main Ways to Calculate the Size of A Population

Answer 9

• Count all individuals in the population
• Sub-sample and extrapolate
• Mark-recapture

Question 10

Counting all individuals int he population

Answer 10

-usually not possible, unless there is a small population such as the Northern Spotted Owl

Question 11

Sub-sample and extrapolate

Answer 11

• estimate of population size
• e.g. quadrant and transect sampling

potential difficulties:

• over what area do you extrapolate
• heterogeneous habitat (not every sample is the same and leads to inaccurate estimate)
• movement of individuals

Question 12

Mark-Recapture

Answer 12

mark: catch some individuals and mark them
recapture: return later and catch some individuals and tally number marked and unmarked

M/N = m/n
M- number marked
m- number marked in recapture
N- estimated population size
n- total in recapture

assumptions:

• individuals not moving in/out of study area
• individuals size between captures
• no catch bias
• no fitness difference between marked and unmarked

Question 13

Demography

Answer 13

• study of vital statistic of populations
• birth and immigration rates (+)
• death and immigration rates (-)
• the values of vital statistics depend on the traits of the focal organisms
• these factors are part of what determines the population size

Question 14

Life table

Answer 14

• summarizes age-specific demographic stats

- data gathered for a cohort

Question 15

Cohort

Answer 15

• group of the same age that can be followed through time

- e.g. group of lizards born the same summer

Question 16

Survivorship

Answer 16

-the average proportion of a cohort that survives to a particular age class

Question 17

Fecundity

Answer 17

• the number of females produced by each female

- average births/year/original female

Question 18

Net-reproductive Rate

Answer 18

• growth rate of a population per generation

- average number of female offspring that each female produces over her lifetime

Question 19

Fertility

Answer 19

-average number of offspring (male + female) that a female produces during lifetime

Question 20

r-selection

Answer 20

• Type III survivorship
• high fecundity and low survivorship

includes:

• many offspring
• small offspring
• early maturity
• small body size
• low disease resistance
• low predator resistance
• short life span

Question 21

K-selection

Answer 21

• Type I survivorship
• low fecundity and high survivorship

includes:

• few offspring
• large offspring
• late maturity
• large body size
• high disease resistance
• high predator resistance
• long life span

Question 22

Per capita rate of increase (r)

Answer 22

-birth rate minus death rate per individual

r = (births - deaths) / N

Question 23

Intrinsic rate of increase (r-max)

Answer 23

• maximum value of r
• optimal conditions for growth
• species specific

Question 24

Exponential growth

Answer 24

• when r is positive and constant
• density independent does not depend on the number of individuals
• adds an increasing number of individuals as the population grows
• happens in nature when there is little intraspecific competition
• including: new population, after a bottleneck, increase in resources, decrease in predation

-dN / dt = rN

Question 25

Exponential growth formula

Answer 25

dN / dt = rN

Question 26

Christmas Bird Count

Answer 26

- National Audubon Society - began in 1900 - bird censuses by volunteers - helped to provide long-term demographic data for hundreds of species

Question 27

Logistic growth formula

Answer 27

dN / dt = r N [ (K -N) / K]

Question 28

Carrying Capacity (K)

Answer 28

-maximum number of individuals that can be supported and sustained in a particular habitat

Question 29

Limits to population growth

Answer 29

-r and K can fluctuate over time density independent: - changes in environment (abiotic and biotic) - e.g. natural disasters, drought density dependent: - function of population size - increased competition

Question 30

Density dependent growth

Answer 30

- survival declines at high population density - fecundity declines at high population density due to: - function of population size - increased competition

Question 31

Population Dynamics

Answer 31

- changes in populations through time and space | - K, r, births, deaths, immigration, emigration

Question 32

Metapopulation Dynamics

Answer 32

- metapopulations connected by immigration and emigration | - extinction and re-colonization

Question 33

Ilkka Hansi

Answer 33

- studied Glanville fritillary (endangered species of butterfly) - ranged across fragmented landscape - although some populations go extinct over time, migration can restore or establish populations - overall balance between population extinctions and re-colonizations

Question 34

Significant predictors of patch extinction

Answer 34

- small population size - small size of neighboring population - low flower abundance - low heterozygosity - given enough time, each population within a metapopulation is expected to go extinct

Question 35

Heterozygosity importance to populations

Answer 35

- a proxy for genetic diversity - often small population sizes (loss of diversity from drift) possibly with inbreeding - low genetic diversity is a bad thing for the long term health of population

Question 36

Population cycles

Answer 36

somewhat regular rise and fall in population size

Question 37

Factors that cause population cycles

Answer 37

- competition for resources - predator-prey - host-parasite - competition with other species

Question 38

Lemmings

Answer 38

- order Rodentia - 4-5 species - example of population cycles - Arctic tundra - herbivores - jumping off cliffs - resources (mosses and grasses or prey? - exclosure experiments supports prey - but scope and scale was limited - some models support resources - but include parameters that are difficult to estimate - the debate continues

Question 39

Most populous countries

Answer 39

China, India, US

Question 40

Population thinking

Answer 40

- holds that variation among individuals in a population is not irrelevant - rather, understanding this variation is key to understanding how populations change through time in their abiotic and biotic environments

Question 41

Population Ecology

Answer 41

-the study of how and why the number of individuals in a population changes over time and space

Question 42

Generation

Answer 42

-the average time between a mother's first offspring and her daughter's first offspring

Question 43

Age class

Answer 43

-a group of individuals of specific age

Question 44

Age-specific fecundity

Answer 44

-the average number of female offspring produced by a female in each age class

Question 45

Life history

Answer 45

- traits related to how individuals allocate resources to growth, reproduction, or survival - including survivorship, age-specific fecundity, age at first reproduction, and growth rate - often include fitness trade offs

Question 46

Replacement rate

Answer 46

-the average fertility required for each woman to produce exactly enough offspring to replace herself and her offspring's father (slightly above 2.0 to account for the mortality of some women before they bear children)

Question 47

Zero population growth

Answer 47

when replacement rate is sustained for a generation and r = 0

Question 48

Long term data on wild populations is...

Answer 48

hard to collect