Ch 53

Question 1

population

Answer 1

organisms of the same species that exist in a given geographic area at a given time; it’s a population if the organisms in questions could reproduce and make offspring that is capable of reproducing (obviously meaning that they also have to be in the same place at the same time), populations are shaped by the interactions between individuals and their environment, populations have size and geographical boundaries

Question 2

population ecology

Answer 2

focuses on statistical data and why numbers of organisms in a population change (or don’t change) over a period of time

Question 3

characteristics of populations

Answer 3

density and dispersion

Question 4

density (of a population)

Answer 4

measured as the number of individuals per unit area, so: how many in an area?

Question 5

dispersion (of a population)

Answer 5

is the pattern of spacing among individuals within the geographic boundaries, so: how are they spaced?

Question 6

how is population measured?

Answer 6

measuring population (size and) density is a difficult task, we can count individuals–not always easy, or we can estimate population numbers by sampling

Question 7

sampling

Answer 7

counting the number of animals in one region and then multiplying by the number of regions

Question 8

clumped dispersion

Answer 8

when individuals aggregate in patches

Question 9

what is dispersion based on?

Answer 9

dispersion is based on resources, such as safety and food

Question 10

uniform dispersion

Answer 10

when individuals are evenly spaced, the resource being space to rest

Question 11

random dispersion

Answer 11

the position of each individual is independent of the others

Question 12

why might plants appear to have a uniform dispersion?

Answer 12

because when you look at plants as a whole they seem to be uniformly dispersed due to the fact that they each need a certain amount of room to grow and sunlight, but you have to look at the plants of only one species, not all plants

Question 13

What is the equation for growth of a population?

Answer 13

∆N/∆t=B-D, where N=population size, B=the number of births, D=the number of deaths, and t=time; we are most interested in birth and death rates since population sizes can differ; births can be symbolized as bN and deaths as dN, therefore, ∆N/∆t=bN-dN, which can be simplified down to ∆N/∆t=(b-d)N

Question 14

What is r? What if r is positive? Negative? Zero?

Answer 14

r is the growth rate, r=b-d, if r is positive, the population is growing, if r is negative, the population is declining, and if r is zero, the population is stable, when we use r in the context of the growth equation, it looks like this: ∆N/∆t=rN because as previously stated, r=b-d

Question 15

What equation would be used if the time interval was very, very short?

Answer 15

dN/dt=rN, this differential equation is really no different from the one above except the time interval is very, very short, instantaneous change

Question 16

Immigration

Answer 16

immigration occurs when individuals enter a local population from another population

Question 17

emigration

Answer 17

emigration occurs when individuals leave an area, emigration=exit

Question 18

How can the growth equation be modified to include immigration and emigration numbers?

Answer 18

r=(b-d)+(i-e)

Question 19

What are four factors that produce changes in population size?

Answer 19

natality (birth), mortality (death), immigration, and emigration

Question 20

What is the intrinsic rate of increase (rmax)?

Answer 20

this is the maximum rate at which species or populations can increase under ideal conditions, this means minimizing death and emigration and maximizing birth and immigration; so, it is the maximal growth rate for a population

Question 21

In regards to the intrinsic rate of increase, what is K?

Answer 21

K is the carrying capacity which is the largest population that can be maintained, K is not a rate, it’s a number

Question 22

What is exponential population growth? What kind of curve does it have? What about a logistic population curve?

Answer 22

exponential population growth is quick growth, it is shown with a J-shaped curve, a logistic population curve is when there’s a cap that can’t be broken and it is shown with an S-shaped curve

Question 23

Environmental resistance

Answer 23

there isn’t infinite space or food for a population, so, as the population increases, the environmental resistance increases as well

Question 24

the logistic equation

Answer 24

a population growth pattern that begins with exponential growth and then slows as the population reaches carrying capacity (K)

Question 25

What is N?

Answer 25

the number of individuals in a population

Question 26

exponential growth

Answer 26

a population growth pattern in which the population grows at a constant rate (r), so, for every time interval, a growing population increases by a fixed percentage and because a fixed percentage of a large population is necessarily larger than a small population, the larger the population size, the faster it grows, a population typically grows exponentially when it has ideal conditions with no restrictions on its growth

Question 27

What do density-dependent factors do? What are some examples of a density-dependent factor?

Answer 27

density-dependent factors are environmental factors whose effects on a population change as population density changes; they tend to retard population growth as population density increases and enhance population growth as population density decreases; so they increase their affect on a population as population density increases; this is a type of negative feedback; resource limitation in crowded populations can stop population growth by reducing reproduction or increasing mortality; some of these factors include: predation, disease, and competition (including interspecific and intraspecific)

Question 28

Density independent factors: what are they? Examples?

Answer 28

density independent factors are environmental factors that affect the size of a population but is not influenced by changes in the population density; so, they limit population growth but are not influenced by changes in population density; examples include: climate (temperature, humidity), weather, and regular catastrophic events such as fires, hurricanes, and floods

Question 29

interspecific competition

Answer 29

the interaction between members of different species that vie for the same resource in an ecosystem (ex: food or living space); DIFFERENT SPECIES

Question 30

intraspecific competition

Answer 30

the interaction between members of the same species that vie for the same resource within an ecosystem (ex: food or living space), SAME SPECIES

Question 31

semelparous reproduction

Answer 31

creatures who do this expend their energy in a single, immense reproductive effort

Question 32

iteroparous reproduction

Answer 32

creatures who do this exhibit repeated reproductive cycles throughout their lifetimes

Question 33

K strategy (aka K selection)

Answer 33

a reproductive strategy in which a species typically has a large body size, slow development, and long lifespan and does not devote a large proportion of its metabolic energy to the production of offspring; so, it maintains a population near the carrying capacity of the environment, and these species often have a large body size, low reproductive rates, long life spans, and they inhabit stable environments

Question 34

R strategy (aka R selection)

Answer 34

a reproductive strategy in which a species typically has a small body size, rapid development, and short lifespan and devotes a large proportion of its metabolic energy to the production of offspring; so, it emphasizes a high growth rate, and these organisms typically have a small body size, high reproductive rates, short life spans, and they inhabit variable environments

Question 35

Type 1 survivorship curve

Answer 35

mortality is greatest in old age; the probability of survivorship decreases with age; K-strategists

Question 36

Type 2 survivorship curve

Answer 36

mortality is spread evenly across all ages

Question 37

Type 3 survivorship curve

Answer 37

mortality is greatest among the young; the probability of survivorship increases with age; r-strategists

Question 38

metapopulation

Answer 38

a population that is divided into several local populations among which individuals occasionally disperse (immigrate and emigrate); metapopulations are becoming more common as humans alter the landscape by fragmenting existing habitats to accommodate homes and factories, agricultural fields, and logging, as a result, the concept of metapopulations, particularly as it relates to endangered and threatened species, has become an important area of study in conservation biology

Question 39

source habitat

Answer 39

a good habitat in which local reproductive success is greater than local mortality, surplus individuals in a source habitat may disperse to other habitats; these are the preferred habitats, they increase the likelihood of survival and reproductive success for the individuals living there, local individuals disperse from source habitats

Question 40

source population

Answer 40

populations that live in source habitats, they generally have greater population densities than populations at less suitable sites, and surplus individuals in the source habitat disperse and find another habitat in which to settle and reproduce

Question 41

sink habitats

Answer 41

a lower quality habitat in which local reproductive success is less than local mortality; lower quality habitats, the individuals living there may suffer death, or, if they survive they will have poor reproductive success

Question 42

sink population

Answer 42

the population living in sink habitats, without immigration from other areas, a sink population declines until extinction occurs, if a local population becomes extinct, individuals from a source habitat may recolonize the vacant habitat at a later time

Question 43

what was the world’s population in 2003?

Answer 43

6.3 billion

Question 44

How has the per capita growth rate declined from its peak in 1965?

Answer 44

Per capita growth rate has declined from its peak in 1965 of about 2% per year to 1.3%

Question 45

What do scientists predict about population growth by the end of the 21st century?

Answer 45

Scientists predict zero population growth by the end of the 21st century

Question 46

population characteristics in highly developed countries

Answer 46

low birth rate, low infant mortality, low fertility rate, long life expectancies, and high average income

Question 47

population characteristics of developing countries

Answer 47

high birth rate, high infant mortality, high fertility rate, short life expectancies, and low average income

Question 48

people overpopulation

Answer 48

a situation in which there are too many people in a given geographic area; results in pollution, environmental degradation, and resource depletion

Question 49

consumption overpopulation

Answer 49

a situation in which each individual in a human population consumes too large a share of resources; results in pollution, environmental degradation, and resource depletion

Question 50

Is it possible for a country to have replacement-level fertility (the number of children a couple must produce to ‘replace’ themselves) and still experience population growth?

Answer 50

Yes

Question 51

What does young age structure cause?

Answer 51

young age structure causes a positive population growth momentum as large pre-reproductive age group matures