Chapter 40 - Population Ecology

Question 1

climate

Answer 1

long-term prevailing weather conditions in a given area

Question 2

abiotic factors

Answer 2

nonliving factors that are the chemical and physical attributes of the environment that influence distribution and abundance of organisms

Question 3

biotic factors

Answer 3

living factors or other organisms that are part of an individual’s environment and influence distribution and abundance of life

Question 4

what are the regional and local effects on climate?

Answer 4

seasonality, bodies of water, and mountains

Question 5

biome

Answer 5

major life zones characterized by vegetation type in terrestrial biomes or by physical environment in aquatic biomes

Question 6

climograph

Answer 6

a plot of the annual mean temperature and precipitation in a particular region

Question 7

disturbance

Answer 7

an event such as a storm, fire, or human activity that changes a community, removes organisms from it, and alters resource availability

Question 8

dispersal

Answer 8

the movement of individuals or gametes away from their area of origin or from centers of high population density

Question 9

why is understanding dispersal important?

Answer 9

because it allows us to understand the role of geographic isolation in evolution and the broad patterns of species distribution that we see around the world today

Question 10

what factors affect the distribution of a species and how?

Answer 10

biotic factors abiotic factors (water and oxygen, salinity, sunlight, rocks and soil) affect population density, dispersion, and demographics

Question 11

population density

Answer 11

the number of individuals per unit area or volume

Question 12

dispersion

Answer 12

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

Question 13

immigration

Answer 13

the influx of new individuals from other areas

Question 14

emigration

Answer 14

the movement of individuals out of a population and into other locations

Question 15

what are the different patterns of dispersion?

Answer 15

clumped, uniform, and random

Question 16

clumped dispersion

Answer 16

-individuals aggregated in patches
-due to uneven distribution of resources
-social groups / predators packing together to catch prey

Question 17

uniform dispersion

Answer 17

-individuals are evenly spaced
-interactions of competition and territoriality between individuals
-can be intentional

Question 18

random dispersion

Answer 18

-individuals are randomly distributed
-organisms whose dispersal are random

Question 19

demography

Answer 19

the study of key characteristics of populations and how they change over time

Question 20

life table

Answer 20

summarizes the survival and reproductive rates of individuals in specific age-groups within a population

Question 21

cohort

Answer 21

a group of individuals of the same age that researchers usually follow from birth until death

Question 22

survivorship curve

Answer 22

graphic representation of the number of individuals in a population that can be expected to survive at any specific age

Question 23

type I survivorship curve

Answer 23

-low death rate in early/middle life
-high death rate in older age groups
-high investment, few offspring
-e.g. humans

Question 24

type II survivorship curve

Answer 24

-consistent death rate over lifespan
-common in rodents, lizards, etc.

Question 25

type III survivorship curve

Answer 25

-high death rate in early/middle life
-low death rate in older age groups
-lots of offspring, low investment
-e.g. plant species, turtles

Question 26

why is there no type IV survivorship curve?

Answer 26

-trade offs shape life histories
-as resources goes up, offspring # goes down and vice versa

Question 27

carrying capacity

Answer 27

the maximum population size that a particular environment can sustain

Question 28

logistic population growth model

Answer 28

per capita rate of population growth approaches 0 as the population size nears the carrying capacity
-the exponential growth model and the expression that reduces the per capita rate as N increases
-dN/dt = rN(K-N/K)

Question 29

what does (K-N)/K represent?

Answer 29

the fraction of K that is still available for population growth

Question 30

why does a constant per capita rate of growth (r) for a population produce a curve that is J-shaped?

Answer 30

because a J shape represents exponential growth; the population begins growing slowly, and as it accumulates more individuals per unit of time, the curve gets steeper and the rate of growth becomes more rapid

Question 31

summarize the effects of r and k on logistic population growth dynamics

Answer 31

-r (intrinsic growth rate) represents maximum per capita growth rate of a population under ideal conditions, typically in an unlimited resource environment. a higher r value indicates a population with higher reproductive rate and ability to grow rapidly when resources are abundant
-k (carrying capacity) will affect how quickly the growth of a population occurs. as a population gets closer to the carrying capacity, the growth occurs more slowly
- r primarily influences initial growth rate of population while k sets the upper limit on the population size that can be sustained in a given environment
-the parameters, r and k, work together to establish the s-shaped growth curve

Question 32

life history

Answer 32

the traits that affect an organism’s schedule of reproduction and survival makeup
-examples include when reproduction begins, how often the organisms reproduces, and the number/size of offspring produced per reproductive episode

Question 33

k-selection

Answer 33

selection for traits that are advantageous at high densities
-strong intraspecific competition

Question 34

r-selection

Answer 34

selection for traits that are advantageous at low densities/uncrowded environments
-weak intraspecific competition

Question 35

density independent

Answer 35

birth or death rates do not change with population density

Question 36

density dependent

Answer 36

birth or death rates that do change with population density

Question 37

equilibrium population density

Answer 37

can occur when there’s a combination of density-dependent and density-independent factors and the value at which the number of individuals in a population does not change

Question 38

population dynamics

Answer 38

fluctuation in population size from year to year and place to place, which is influenced by many factors and can influence other species

Question 39

metapopulation

Answer 39

a number of local populations that are linked
-can help ecologists understand significance of immigration and emigration, as well as population dynamics and gene flow in patchy habitats

Question 40

(40.1) what are the key points of how Earth’s climate influences the distribution of terrestrial biomes?

Answer 40

-global climate patterns are largely determined by the input of solar energy and Earth’s revolution around the sun
-the changing angle of the sun, bodies of water, and mountains exert seasonal, regional, and local effects on climate
-climographs show that temperature and precipitation are correlated wtih biomes

Question 41

(40.2) wat are the key points of how aquatic biomes are diverse and dynamic systems that cover most of Earth?

Answer 41

-aquatic biomes are characterized primarily by their physical environment rather than climate
-they are often layered with regard to light penetration, temperature, and community structure
-

Question 42

(40.3) what are the key points of how interactions between organisms and the environment limit the distribution of species?

Answer 42

-ecologists want to know not only where species occur by why species occur where they do
-the distribution of species may be limited by dispersal, biotic factors, and abiotic factors

Question 43

(40.4) what are the key points of how biotic and abiotic factors affect population density, dispersion, and demographics?

Answer 43

-population density reflects the interplay of births, deaths, immigration, and emigration
-environmental and social factors influence the dispersion of individuals
-populations increase from births and immigration and decrease from deaths and emigration
-life tables and survivorship curves summarize specific trends in demography

Question 44

(40.5) what are the key points of how the exponential and logistic models describe the growth of populations?

Answer 44

-if immigration and emigration are ignored, a population’s per capita growth rate equals its birth rate minus its death rate
-the exponential population growth equation represents a population’s growth when resources are relatively abundant, where r is the intrinsic rate of increase and N is the number of individuals in a population
-exponential growth cannot be sustained in any population, and a more realistic population model limits growth by including carrying capacity
-according to logistic population growth model, growth levels off as a population size approaches the carrying capacity

Question 45

(40.6) what are the key points of how population dynamics are influenced strongly by life history traits and population density?

Answer 45

-life history traits are evolutionary outcomes reflected in the development, physiology, and behavior of the organism
-in density-dependent population regulation, death rates rise or birth rates fall with increasing density
-a birth or death rate that does not vary with density is density-independent
-density-dependent changes in birth and death rates curb population increase through negative feedback and can eventually stabilize a population near its carrying capacity
-density-dependent limiting factors include intraspecific competition for limited food or space, disease, or physiological factors
-all populations exhibit size fluctuations
-a metapopulation is a group of populations linked by immigration and emigration