Populations & Populations & CommunitiesCommunities

Unit 1

Ecology is…Ecology is…• The scientific study of the interactions

between organisms and the environment

Biotic vs. Abiotic Biotic vs. Abiotic FactorsFactors

• Biotic: living componentso Ex: live or dead organisms, waste, by-product…

• Abiotic: non-living componentso Ex: light, soil, water…

Abiotic Shapes BioticAbiotic Shapes Biotic• These abiotic factors create different

environmental conditions on the planet • Biotic life has evolved to live in these

areas

Organisms to Organisms to BiosphereBiosphere

• Organism: one individual life form• Species: one type of organism or a group • Population: group of the same species• Community: collection of populations• Ecosystem: community and the environment• Biosphere: global ecosystem (Earth)

Population StudiesPopulation Studies

PopulationPopulation• A group of individuals,• Of the same species,• In one area,• At one time.• Ex: Number of dogs in

Oswego in 2005

Estimation of Estimation of Numbers-QuadratNumbers-Quadrat

Random Sampling/Quadrat Sum of organisms in grids/# grids used.Multiply by total number of grids.EX: Count the sea urchins in the highlighted grids. 1+1+2+1=5÷4 grids used = 1.25 urchins per grid Multiply by the total number of grids 1.25x11x11= 151 urchins

Capture-Recapture-Capture-Recapture-Lincoln-PetersonLincoln-Peterson

• You will compare numbers marked to what you recaptured with and with out marks.

Capture Recapture-Capture Recapture-Schnabel IndexSchnabel Index

• Reduces over estimations unlike Peterson and completely dependent on number of samples taken.

Population DensityPopulation Density• # of individuals per unit area• Ex: A farmer has 2 cows per square acre of land.

Population GrowthPopulation Growth• How a population changes over time• May stay the same, increase (+), or decrease (-)

Factors That Affect Factors That Affect Pop. SizePop. Size

+•Natality (births)•Immigration

o Individuals move into an area

-•Mortality (deaths)•Emigration

o Individuals leave an area

Carrying CapacityCarrying Capacity• Largest number of individuals of a given species

an environment can support with its available resources

Limits to Population Limits to Population GrowthGrowth

• Limiting Factorso Causes population growth to slowo Can be biotic or abiotic

Density-Dependent Density-Dependent FactorsFactors

• Limiting factors that depend on population size (density matters)

• Competition• Stress• Predation• Parasitism• Disease

Density-Independent Density-Independent FactorsFactors

• Limiting factors that do not depend on population size (density doesn’t matter)

• Weather• Natural disasters• Human activities• Behaviors

Chinese forests being cleared for timber and farmland, so pandas are running out of food and places to live.

Draught has caused this river bed to dry up.

Distribution PatternsDistribution Patterns

DensityDensity• Amount of organisms in a measured area• Formula:• Population Density = # organisms/area

Density ProblemsDensity Problems• EX: There are 7 squirrels counted in a 3 acre plot

during the Spring of 2014. After a severely cold and snowy winter, there are only 3 in the spring of 2015.

Density of 20147 squirrels/3 acres = 2.3 squirrels per acre

Desnity of 20153 squirrles/3 acres = 1.0 squirrels per acre

Community Community RelationshipsRelationships

Competition & NicheCompetition & Niche• Niche: the location and resources an organism

consumes

• Competitive Exclusion Principle: two types of organisms cannot exist in the same niche with the same population health

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publishing as Pearson Benjamin Cummings.

Figure 54.4 shows that when two species of finch coexist, their Figure 54.4 shows that when two species of finch coexist, their beak sizes diverge, which is character displacement. If the two beak sizes diverge, which is character displacement. If the two species colonized an island on which there were seeds of only species colonized an island on which there were seeds of only

one size, what would Gauseone size, what would Gause’’s principle of competitive exclusion s principle of competitive exclusion (page 1199 in the textbook) predict?(page 1199 in the textbook) predict?

A. The finches would hybridize and become one species.

B. G. fuliginosa would evolve small beaks, and G. fortis would evolve large beaks.

C. One of the finch species would probably disappear from the island.

D. The plants would evolve seeds of different sizes.

E. It is impossible to predict the outcome

Biodiversity & Biodiversity & Simpson’s IndexSimpson’s Index

• Richness is amount of different species• Evenness is relative number compared to other

species.Compare the two communities based on richness

and evenness.

SuccessionSuccession• Succession: when a ecosystem is disturbed and

recoverso Primary- first, no soil, very long time, lichens (pioneer)o Secondary-after soil is established, climax community (keystone)

• Quick Clip: https://www.youtube.com/watch?v=E0qdWoLdk1c