Population Dynamics Chapter 15

Learning Objectives Characterising Species distribution Abundance and Population Age Structure Rate of Growth Distribution Birth and Death Rate Characterising Species distribution Factors that determine the size of a population Carrying capacity population rate of growth Mortality Biotic/abiotic factors predation & competition

Population: Abundance and Sampling Abundance: The number of individuals of a species per unit area (Density) Sampling Techniques: Mark-recapture technique Total number= (# marked x total caught)/ # marked ones caught Sampling through quadrats. Transects (changes in environment) DynamicScience – Population sampling information Distribution: Uniform, Random, Clumped Sampling allows us to map distribution and density of organisms

Population distribution Abundance assists us with determining distribution. What factors affect Distribution? Food source Predation/ hunting/ habitat destruction Climate, temp, environment Reproductive factors What factors Abiotic/Biotic might be affecting the distribution of the elephant population  (Questions from internet)

Population: Age Structure Pre-reproductive age Reproductive age Post-reproductive age

Population Growth Curves Usually there are 3 phases: Slow growth as numbers are built up Rapid growth Population growth decreases, population is approximately stable. Stable, no growth Rapid growth Slow growth

Population Growth Patterns J Shaped Curves: Exponential growth Lag phase Acceleration phase Population (next generation)= Rate of increase x Population (previous gen.)

Population Growth Patterns S 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 environment Carrying 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 rates Density- dependent factors (Intraspecific): (food/ resources) Increased influence in higher populations Density- Independent factors: floods, drought. Interspecific Factors: (Competition with other species) Predation & Habitat Destruction Growth 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 Interactions Competition: 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 Questions Complete questions online at http://rasozbiologyresources.weebly.com

Population Evaluations & Changes in Ecosystems Chapter 15 & 16

Population Evaluations Population 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 Ecosystems Is the change environmental Regular (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