Population and Relationships

Population and growthLimiting factors

Population growth curvesExponentialLogistics

Symbiotic relationships

Population and Growth• Population- consists of all individuals

of the same species that live together in one place at one time.

Population and Growth• Biodiversity- the number and variety of

organisms in a given area during a specific period of time

Population and GrowthIn order to predict population growth the

following must be considered:• Population Size • Population Growth Rate • Carrying Capacity• Limiting Factors

Population and Growth• Population size- the number of

individuals in a population

• Population growth rate- the rate at which the birthrate is greater than the death rate.

(Growth occurs when more individuals are being born than dying in a population)

Population and Growth• Carrying Capacity- the population size

that an environment can sustain• Limiting Factors- Factors That Control

Population Growth» Competition» Predation» Parasitism» Crowding» Stress » Disease

Population and GrowthLimiting Factors

Competition- Situation in which two or more organisms attempt to use the same scarce resource

Primary sources of Competition:

• Food• Water• Space• Mates

Population and GrowthLimiting Factors

Predation- A relationship between two organisms in which one organism kills (predator) and devours another organism (prey).

- Affects population size of both predator (increases) and the prey (decreases).

- Often cyclical.

Population and GrowthLimiting Factors

• Parasitism- The relationship between two organisms where one organism benefits (parasite) and the other is harmed (host).

Example: Tapeworm• You are harmed because it

lives off your intestinal fluids• Segments break off to form a

new worm!

Population and GrowthLimiting Factors

• Crowding- exceeding the carrying capacity of a habitat which can result in stress and disease.

• Stress and disease can lead to poor reproductive success and can cause damage to the habitat.

Population Growth CurvesExponential

Exponential growth:

• Population increases by a constant proportion per unit of time

• At this growth rate the population exhibits a J-shaped curve

Population Growth CurvesLogisticLogistic growth:

• Population increases rapidly for a period of time, its growth begins to slow, and ultimately, growth stops (the birthrate and death rate become equal).

• At this growth rate the population exhibits an S-shaped curve.

• K (carrying capacity) = maximum population size that an environment can support

K

Symbiotic Relationships• Symbiosis- a close long term

relationship between two or more species that can be beneficial or harmful

Beneficial:• Mutualism= Both benefit• Commensalism= Only one

benefits & other is not harmed or helped

Harmful:• Parasitism= One benefits &

Host slowly harmed

Symbiotic RelationshipsMutualism- Both BenefitExample- Lichen (fungus and algae

together)Fungi provides-

• carbon dioxide• moisture

Algae provides-• food• oxygen

Symbiotic Relationships• Commensalism- one benefits, the other is

neither harmed or helped• Example- whale and a barnacle

Whale – unharmed

Barnacles– Protection from

predators– Transportation to new

food sources

Symbiotic Relationships• Parasitism- one benefits (parasite),

other harmed (host)• Example- flea and a dogFlea

– Food – Shelter

Dog– Itches– Can become infected

with diseases

Symbiosis Type

Organism 1

Organism 2

Example

Mutualism

Commensalism

Parasitism

+ = benefits, - = harmed, 0 = neutral (neither harmed nor helped)

Fill out the chart:

+ +

+

-+

0