Population Ecology

Question 1

What is a population?

Answer 1

a group of individuals of a single species living in the same general area

Question 2

How can populations be described by their boundaries and size?

Answer 2

the number of individuals living within those boundaries

Question 3

What is population density?

Answer 3

the number of individuals per unit area or volume

Question 4

What is population dispersion?

Answer 4

the pattern of spacing among individuals within the boundaries of the population

Question 5

What are the factors affection population density?

Answer 5

Birth; immigrations (new individuals in the area); death; emigration (individuals leave pop)

Question 6

How does clumped dispersion come about?

Answer 6

individuals are aggregated in patches. this happens because where resources are located and sometimes mating behavior

Question 7

How does uniform dispersion come about?

Answer 7

evenly spaced pattern of dispersion may result from direct interactions between individuals in the population. some plants release chemicals so that other plants can’t grow near them; animals can show this through territoriality–the defense of a bounded physical space

Question 8

How does random dispersion come about?

Answer 8

unpredictable; independent of other individuals. Occurs in absence of strong attractions; like plants with windblown seeds

Question 9

What is demography?

Answer 9

The study of the vital statistics of populations and how they change over time

Question 10

What is a life table? How is one constructed and what can you learn from it?

Answer 10

age-specific summaries of the survival pattern of a population; follow the fate of a cohort, a group of individuals of the same age, from birth until all of the individuals are dead; number alive are start of year, proportion alive at start of year, number of deaths during year, death rate, avg. additional life expectancy, for females and males

Question 11

What is a survivorship curve?

Answer 11

a plot of the proportion or numbers in a cohort still alive at each age

Question 12

Why do demographers who study sexually reproducing species to determine reproductive rates generally ignore males and concentrate on the females in a population?

Answer 12

because only females produce offspring; therefore demographers view populations in terms of females giving rise to new females

Question 13

What is a reproductive table? How is one constructed?

Answer 13

fertility schedule; an age-specific summary of the reproductive rates in a population;
constructed by measuring the reproductive output of a cohort from birth until death

Question 14

A change in population size during a fixed time interval can be defined as:

Answer 14

Change in population Size = Births + Immigrants Entering Population - Death - Emigrants Leaving Population

Question 15

When is a population growing?

Answer 15

when birth exceeds death rate

Question 16

When is a population declining?

Answer 16

When death exceeds birth rate

Question 17

When is there zero population growth?

Answer 17

When the per capita birth and death rates are equal

Question 18

What’s required for exponential growth?

Answer 18

members of pop. all have access to abundant food and are free to reproduce at their physiological capacity

Question 19

What is carrying capacity?

Answer 19

symbolized by k; the maximum population size that a particular environment can sustain

Question 20

What is logistic population growth?

Answer 20

the precept rate of increase approaches zero as the population size nears the carrying capacity

Question 21

What is life history?

Answer 21

The traits that affect an organism’s schedule of reproduction and survival make up its life history;

Question 22

What are the three main variables of life history?

Answer 22

When reproduction begins, how often the organism reproduces, and how many offspring are produced per reproductive episode

Question 23

What is semelparity?

Answer 23

One reproductive episode with lots and lots of offspring

Question 24

What factors favor the evolution of semelparity?

Answer 24

offspring survival is low and adults are also less likely to survive; unpredictable environment

Question 25

What is iteroparity?

Answer 25

repeated reproduction with small offspring

Question 26

What factors favor the evolution of iteroparity?

Answer 26

adults are more likely to survive to breed again and offspring have better chance at surviving; dependable environments

Question 27

What’s the deal with plants that colonize disturbed environments?

Answer 27

Produce many small seeds, only a few of which may reach a suitable habitat

Question 28

What’s the deal with animals that suffer high predation rates?

Answer 28

Produce many offspring

Question 29

What’s the deal with the Brazil nut tree?

Answer 29

Produce large seeds packed with nutrients that help the seedlings become established

Question 30

What’s the deal with most primates?

Answer 30

generally bear only one or two offspring at a time; parental care and an extended period of learning in the first several years of life are very important to offspring fitness

Question 31

What is K-selection (= density-dependent selection)? When does K-selection operate?

Answer 31

Selection for traits that are sensitive to population density and are favored at high densities

Question 32

What is r-selection (= density-independent selection)? When does r-selection operate?

Answer 32

selection for traits that maximize reproductive success in uncrowded environments

Question 33

Why does population growth rate decrease as population size approaches carrying capacity?

Answer 33

competition among individuals is stronger

Question 34

What environmental factors keep populations from growing indefinitely?

Answer 34

competition?

Question 35

Why are some populations fairly stable in size while others are not?

Answer 35

if they are density dependent vs independent

Question 36

Assuming that immigration and emigration offset one another, when does a population grow? When does a population decline?

Answer 36

grow when birth rate exceeds death rate and declines when death exceeds birth

Question 37

What’s the deal with birth and death rates that are density independent?

Answer 37

birth rate or death rate does not change with populations density

Question 38

What’s the deal with birth and death rates that are density dependent?

Answer 38

death rate increases with pop density and/or birth rate falls with rising pop density

Question 39

Without some type of negative feedback between population density and the rates of birth and death, a population would never stop growing. How does density-dependent regulation provide that negative feedback?

Answer 39

halts population growth through mechanisms that reduce birth rates or increase death rates; affects reproduction, growth, and survival

Question 40

How is population density being controlled in kelp perch?

Answer 40

As their pop density grew there were less places to hid in, the perch were more vulnerable to predation. As density increased, more perch were eaten

Question 41

Talk about Competition for Resources.

Answer 41

increasing pop density intensifies competition for nutrients and other resources, reducing reproductive rates

Question 42

Talk about Predation.

Answer 42

as prey population builds up, predators may also feed preferentially on that species

Question 43

Talk about Toxic Wastes.

Answer 43

yeasts produce ethanol, there is a certain ratio of ethanol that yeasts can live in so that effects the pop density

Question 44

Talk about Intrinsic Factors.

Answer 44

When pop density grows intrinsic physiological factors can regulate pop size by dropping reproduction rates

Question 45

Talk about Territoriality

Answer 45

limits pop density when space becomes the reserve for which individuals compete

Question 46

Talk about Disease

Answer 46

if transmission rate of disease increases as population density increases, the disease’s impact is density dependent and can effect more people and kill more people

Question 47

What do we mean by population dynamics?

Answer 47

population fluctuations from year to year or place to place

Question 48

What’s the deal with the moose population on Isle Royale in Lake Superior?

Answer 48

they have fluctuated substantially since around 1900; harsh weather, cold wet winters, weaken moose and reduce food availability

Question 49

What’s the deal with population cycles in the snowshoe hare and lynx?

Answer 49

have a roughly 10-year cycle of population fluctuating due to the amount of hare increases lynx eat and increase keep eating and make hare decrease which makes lynx decrease which make hare increase and so on

Question 50

What’s a metapopulation? Why are immigration and emigration important for maintaining a metapopulation?

Answer 50

when a number of local populations are linked;
if a species become distinct or emigrates, than new species immigrates into the metapopulation; the one that emigrated, immigrates to a different metapopulation

Question 51

What has happened to the growth rate of Humans since the 1960s?

Answer 51

it has began to slow

Question 52

What does the reduction in growth rate for humans indicate? Why has the growth rate slowed down?

Answer 52

fundamentale changes in population dynamics due to diseases and to voluntary population control (only one kid in china)

Question 53

What are the two extreme ways to have zero population growth?

Answer 53

to have either both high birth and death rates, or low birth and death rates

Question 54

What is demographic transition? What contributes to demographic transition?

Answer 54

the movement from high birth and death rates toward low birth and death rates, which tends to accompany industrialization and improved living conditions

Question 55

If populations are near equilibrium in industrialized nations and even below replacement in many, why is the human population still growing?

Answer 55

because not all human population are in industrialized areas

Question 56

What do these different age-structure pyramids indicate about the populations of these countries? How can they help us make predictions about the future with regard to both population growth and social conditions?

Answer 56

age structure- the relative number of individuals of each age in the populations; Afghanistan- rapid growth; US- slow growth; Italy- No growth; can predict by seeing how many people will be at working/reproductive age and have to support the older citizens.

Question 57

How is infant mortality figured? How is life expectancy figured?

Answer 57

the number of infant deaths per 1,000 live births;

the predicted avg. length of life at birth

Question 58

What do we mean by ecological footprint? How can it be estimated?

Answer 58

summarizes the aggregate land and water area required by each person, city, or nation to produce all the resources it consumes and to absorb all the wast it generates;
add up all the ecologically productive land on the planet and divide by the populations

Question 59

80% or more of energy used in developed nations comes from fossil fuels. Is this sustainable? What are the consequences?

Answer 59

this unsustainable reliance on fossil fuels is changing Earth’s climate and increasing the amount of waste that each of us produces

Question 60

So, we can only speculate about Earth’s carrying capacity for the human population and about what factors will eventually limit our growth. What are some of those limiting factors?

Answer 60

Food; fresh water; capacity of the environment to absorb its wastes;