ch 54: population ecology

what is ecology

the study of how organisms interact with one another and with their environment

what is a population

a group of individuals of the same species living in one place and time

what aspects of populations do we study

range, distribution, and dynamics

range

geographic area where population occurs

distribution

spacing pattern of individuals

dynamics

how population changes over time

what process govern these? what terms do we use to describe these factors

births, deaths, immigration, and emigration govern population dynamics

what are metapopulation dynamics

interactions between separate populations connected by migration/dispersal

define metapopulation

a group of separated populations of the same species connected through movement of individuals

source-link dynamics

source populations produce excess individuals that disperse into sink populations that cannot survive alone

how do connections between population influence factors such as range, distribution, and dynamics of a population

movement between populations can expand range, change distribution, and stabilize population size

how do the agents of genetic change integrate with the dynamics of ecological populations

mutation, natural selection, genetic drift, gene flow, and nonrandom mating affect adaptation, survival, and population change over time

what aspects of the environment influence organisms’ ecology

temperature, water, sunlight, soil, predators, competition, and resource availability

what types of responses to environmental factors do we observe in organisms

physiological, morphological, and behavioral responses

allen’s rule

animals in colder climates tend to have shorter appendages

bermann’s rule

animals in colder climates tend to have larger body sizes

what is demography

the quantitative study of population characteristics

what aspects of a population’s structure are influenced by its demography

age structure, sex ration, birth rates, death rates, and generation time

how do demographic factors influence the ecology and evolution of an organism

they affect reproduction, survival, population growth, and natural selection

define survivorship

the percent of an original population surviving to a certain age

interpret a survivorship curve/ graph

type I - high survival until old age

type II - constant mortality

type III - high juvenile mortality

what are life-history traits

they affect survival and reproduction

what is a trade-off

when limited resources force organisms to balance survival, growth, and reproduction

describe data/case-studies given to you regarding trade-offs, life-history, cost of reproduction, etc.

organisms investing more energy into current reproduction often reduce future reproduction or survival, larger clutch sizes may produce smaller offspring

population growth

change in the number of individuals in a population over time

describe population growth models

exponential growth = unlimited resources, rapid growth

logistic growth = growth slows near carrying capacity

interpret graphs of population growth or models of growth

exponential growth forms a J-shaped curve

logistic growth forms an S-shaped curve that levels off at K

what is a model

a simiplified representation used to explain or predict biological patterns

what is an intrinsic growth rate

the maximum possible rate of population increase under ideal conditions

what is exponential growth

rapid growth with unlimited resources

what is logistic growth

growth slows as resources become limited

what ecological/environmental factors might lead us to see exponential growth

abundant resources, low competition

what ecological/environmental factors might lead us to see logistic growth

limited food, space, disease, predation

what is the meaning of N used in the logistic growth equation

population size

what is the meaning of r used in the logistic growth equation

intrinsic growth rate

what is the meaning of K used in the logistic growth equation

carrying capacity

what factors would change the values and govern the dynamics we see from the models

changes in resources, predation, disease, and competition

what happens to the growth rate as a population approaches K

growth slows down because resources become limited and competition, disease, and predation increase

density-dependent

effects increase with population size (competition, disease predation)

density-indepedent

affect populations regardless of size (storms, droughts, fires)

interpret if a factor is density-dependent

stronger in crowded population

interpret if a factor is density-independent

unrelated to population size

explain the predator-prey dynamics illustrustrated by the horseshoe and lynx example

when hare populations increase, lynx populations increase. increased predation then reduces hare numbers, followed by lynx decline

how do the horseshoe and lynx relate to the density-dependent growth factors

predation is a density-dependent factor

K-selected model

species reproduce slowly with fewer offspring and more care

r-selected model

species reproduce quickly with many offspring

why is the K-selected and r-selected model an oversimplication

most species show a mix of both strategies

disease transmission dynamics

disease spread depends on transmission rate

recognize Ri to predict and interpret disease transmission: R0 > 1

disease spreads

recognize Ri to predict and interpret disease transmission: R0 < 1

disease declines

what is herd immunity

occurs when enough individuals are immune to stop disease spread

how does herd immunity relate to vaccine use

vaccines help create herd immunity

how can a pathogen change to increase its own survival

they evolve through natural selection to spread more effectiveley

what are examples of the different strategies pathogens use

becoming more contagious, evading immunity, or becoming less lethal