Population Dynamics Chapter 15
Dec 22, 2015
Population DynamicsChapter 15
Learning Objectives
Factors that determine the size of a population
Carrying capacity
population rate of growth Mortality Biotic/abiotic
factorspredation & competition
• Abundance and Population• Age Structure• Rate of Growth• Distribution• Birth and Death Rate
Characterising Species
distribution
Population: Abundance and SamplingAbundance: The number of individuals of a species
per unit area (Density)
Sampling Techniques:1. Mark-recapture technique
1. Total number= (# marked x total caught)/ # marked ones caught
2. Sampling through quadrats.3. Transects (changes in environment)DynamicScience – Population sampling information
Distribution: Uniform, Random, Clumped
Sampling allows us to map distribution and density of organisms
Population distributionAbundance assists us with
determining distribution.What factors affect
Distribution?Food sourcePredation/ hunting/ habitat
destructionClimate, temp, environmentReproductive factors
What factors Abiotic/Biotic might be affecting the distribution of the elephant population (Questions from internet)
Population: Age StructureAge
StructurePre-
reproductive age
Reproductive age
Post-reproductive
age
Population Growth CurvesUsually there are 3
phases:1. Slow growth as
numbers are built up2. Rapid growth3. Population growth
decreases, population is approximately stable.
Slow growth
Rapid growth
Stable, no growth
Population Growth PatternsJ Shaped Curves: Exponential growth
Lag phaseAcceleration phasePopulation (next generation)= Rate of increase x Population (previous
gen.)
Population Growth PatternsS Shaped Curves: Logistic Growth
Deceleration phase: growth slows due to environmental resistance, competition, organism death
Growth rate is stopped by the Carrying Capacity of the environmentCarrying Capacity: maximum population that can be sustained by the
environment- Affected by Biotic and abiotic factors
Birth rate Vs. Death Rate
Population explosions• Reproduction (many new offspring) & lower death rate• Abiotic environment (lots of food)• Predator control (lack of predators)• Dispersal (spreading into new areas)
Factors affecting growth ratesDensity- dependent factors (Intraspecific): (food/ resources) Increased
influence in higher populationsDensity- Independent factors: floods, drought. Interspecific Factors: (Competition with other species)Predation & Habitat DestructionGrowth Rate (intrinsic)- K-selected/ R-selected strategy (pg 493)
Feature R-selected Strategy
K-selected strategy
Life span Shorter-lived Longer-lived
No. offspring Many few
Energy req. for reproduction
Small energy Large energy
Survival Rate Low High
Sexual maturity Earlier in life Later in life
Incubation period Short/ none Extensive (mths)
Parental care Little/none Extensive
Population InteractionsCompetition: Food, resources (nests, sunlight)Predator + Prey relationships
• Which population peaks first?
• In the absence of adequate predators what happens?
• Without predators, how is prey population regulated?
• How many ‘boom-bust’ cycles can we see?
• What other factors not visible on this graph could be influencing populations
Application QuestionsComplete questions online at
http://rasozbiologyresources.weebly.com
Population Evaluations & Changes in Ecosystems
Chapter 15 & 16
Population EvaluationsPopulation growth = (births + immigration) – (deaths +
emigration)
Percentage population growth rate in a given period = (pop. change during the period/ pop. At start of the period) x 100 Example
100 dolphins in 2012. 3 years later they found 143 dolpins. What is the population growth per year?
Pop. Change= 143-100 = 43. % Growth Rate = (43/100) x 100 (remember this is over 3 yr period)Per year = 43/3 (gives us the % per year) = 14.3% growth per year
Population Elements
Birth Rate
• Birth rate = (number of births per year/ tot. pop in the same year) x 1000
Death Rate
• Death rate= (no. of deaths per year/ total. Pop. In the same year) x 1000
Factors affecting Birth rate in Humans Factors affecting Death Rate In humans
Political policies & economic conditions War and natural disasters
Cultural & Religious background Food supply
Birth control Safe Drinking water & sanitation
Education level Life expectancy and Age profile (more oldies = higher death rate)
Social elements and pressures Disease and access to medical care
Population Analysis
Relate the changes to population:- Death rate- Birth rate- Overall growth
Changes in EcosystemsIs the change environmentalRegular (tides, seasons)Sporadically / Irregular (floods in tropical areas)One-off events (100 year flood or fire, volcanic eruption)Disease or a flow on from population change in another interacting organism.
Is the change the result of humans Oil spill De-forestation Habitat Destruction Global Warming Introduction of new species (deliberate, accidental or ‘classical biocontrol’)
Examples and effects. Management: Biocontrol (biopesticides- bacteria, fungi), Immunocontraception.
Human Impact on Ecosystems