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Chapter 15 Learning Objectives Characterising Species distribution • Abundance and Population • Age Structure • Rate of Growth • Distribution • Birth and Death Rate 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: 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 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 Age Structure Prereproductive age Reproductive age Postreproductive age Population Growth Curves Usually there are 3 phases: 1. Slow growth as numbers are built up 2. Rapid growth 3. 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 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 Death Rate • Birth rate = (number of births per year/ tot. pop in the same year) x 1000 • 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