Chapter 8 Chapter 8 pg 210 pg 210

Understanding Understanding PopulationsPopulations

What is a population?What is a population?

““all the members all the members of a species living of a species living in the same in the same placeplace at the same at the same time”time”

Properties of PopulationsProperties of Populations

1.1. DensityDensity - -““the number of the number of individuals per individuals per unit area or unit area or volume”volume”

Ex - # bass fish per Ex - # bass fish per cubic meter of cubic meter of waterwater

2.2. DispersionDispersion – – “ “ the relative the relative

distribution or distribution or arrangement of arrangement of it’s individuals in it’s individuals in a given amount of a given amount of space”space”

EvenEven ClumpedClumped RandomRandom

Growth RateGrowth Rate

Change in pop. size = Change in pop. size =

Births – DeathsBirths – Deaths

If adults in a population are not If adults in a population are not replace by new births, the growth rte replace by new births, the growth rte will be negative and the population will be negative and the population

will shrinkwill shrink

How How FastFast can the Population can the Population Grow?Grow?

Biotic PotentialBiotic Potential = =

Fastest rate at which Fastest rate at which its population can its population can

grow.grow.Limited by: Limited by:

The organism’s: The organism’s:

Repro. PotentialRepro. Potential

Reproductive PotentialReproductive Potential

1. Number of 1. Number of offspring produced offspring produced at at one timeone time

2. How often does 2. How often does the organism the organism

reproduce reproduce

3. how soon can the 3. how soon can the organism organism reproduce (age!?)reproduce (age!?)

Exponential GrowthExponential Growth

Population growth Population growth that grows faster that grows faster and faster!and faster!

Produces a J-Produces a J-Shaped curveShaped curve

Limits to population GrowthLimits to population Growth

1. Carrying Capacity1. Carrying Capacity 2. Resource Limits2. Resource Limits 3. Competition within a population3. Competition within a population

1. 1. Carrying CapacityCarrying Capacity

Defined as the Defined as the maximum maximum population population (number) that the (number) that the ecosystem can ecosystem can support.support.

Will crash when it Will crash when it reaches capacity reaches capacity due to disease, etc.due to disease, etc.

2. 2. Resource LimitsResource Limits

A particular resource that is A particular resource that is consumed by a particular species consumed by a particular species (food, water, etc) is called a (food, water, etc) is called a ““LIMITING FACTORLIMITING FACTOR””

CC is reached when the species is CC is reached when the species is consuming it at the same rate it is consuming it at the same rate it is being produced.being produced.

3. 3. Competition Within a PopulationCompetition Within a Population

= Members of a population use the = Members of a population use the same resources in the same way so same resources in the same way so they will eventually compete with they will eventually compete with one another as the population one another as the population approaches it carrying capacity.approaches it carrying capacity.

Ex = Christmas timeEx = Christmas time

and Limited toys and Limited toys

2 types of Competition2 types of Competition::

DirectDirect

= direct fighting for = direct fighting for resourcesresources

Ex – foodEx – food

Ex – Limited # of Elmo Ex – Limited # of Elmo dolls at target at an dolls at target at an

8 am sale and 8 am sale and

400 mommies400 mommies

waiting outside!waiting outside!

IndirectIndirect

= indirect fighting for = indirect fighting for resourcesresources

Ex- nocturnal vs. diurnalEx- nocturnal vs. diurnal

Ex – mommy arrives at a Ex – mommy arrives at a 24 hour Target and 24 hour Target and buys the last doll buys the last doll before another before another

mommy arrives at 8 mommy arrives at 8 am!am!

Two types of population Two types of population Regulation:Regulation:

=The cause of death to regulate the =The cause of death to regulate the population size can be:population size can be:

1.1. Density DependantDensity Dependant

2.2. Density IndependentDensity Independent

S – Curve GrowthS – Curve Growth Mimics a “S”Mimics a “S” Population starts slow, then Population starts slow, then

increases quickly, then begins to increases quickly, then begins to level off to support the current level off to support the current population at it’s maximum capacity.population at it’s maximum capacity.

Density DependantDensity Dependant = Death occurs more quickly in a = Death occurs more quickly in a

crowded population than a sparse crowded population than a sparse one.one.

Density IndependentDensity Independent= = death that is death that is

caused caused regardless of regardless of the pop.’s the pop.’s density. density.

It affects all It affects all members of a members of a population in a population in a general/similar general/similar way.way.

8.2 How species interact with each 8.2 How species interact with each other (pg. 217)other (pg. 217)

NicheNiche= role in the = role in the

ecosystem.ecosystem.Ex – physical Ex – physical

home, env home, env factors for its factors for its survival, and its survival, and its interactions with interactions with others.others.

HabitatHabitat= location.= location.

Ex -Where an Ex -Where an organism livesorganism lives

Species InteractionsSpecies Interactionspage 218page 218

= based on whether each species = based on whether each species causes benefit or harm to the other causes benefit or harm to the other species in a given relationship.species in a given relationship.

1.1. CompetitionCompetition

2.2. PredationPredation

3.3. ParasitismParasitism

4.4. MutualismMutualism

5.5. CommensalismCommensalism

CompetitionCompetitionDefined as both Defined as both

species being species being harmed.harmed.

May be in May be in competition for competition for mates, territory, mates, territory, food, etc.food, etc.

PredationPredation

= = defined as: defined as: benefits one benefits one and and harming harming

the otherthe other

MutualismMutualism

= defined = defined as:as:

Benefits Benefits both!both!

ParasitismParasitism

= = defined as: defined as: benefits benefits one, harms one, harms the otherthe other

CommensalismCommensalism= defined as = defined as

one benefits one benefits and the and the

other is other is unaffectedunaffected..

Symbiosis and Symbiosis and CoevolutionCoevolution

SymbiosisSymbiosis is the is the relationship in relationship in which 2 species which 2 species interact.interact.

Typically in which Typically in which one benefits.one benefits.

CoevolutionCoevolution may may occur b/w species occur b/w species in close in close relationship. relationship.

- Without one, the - Without one, the other will die!other will die!