Introduction to Ecology What is Ecology? Answer: The study of inter-relationships among living things and the non-living environment: Soil Abiotic = Non-living factors: Animals Biotic = Living factors: Water Plants Weather

Ecology - Increasing Levels of Complexity: Introduction to Ecology Ecology - Increasing Levels of Complexity: Organism Population: All members of a particular species living within a defined area Community: All interacting populations of species within a defined area Ecosystem: All living organisms and the non-living environment within a defined area Biosphere = Earth (multiple ecosystems)

Population Growth & Regulation Chapter 38: Population Growth & Regulation

Influences Affecting Population Sizes: Chapter 38: Population Growth & Regulation Influences Affecting Population Sizes: 1) Births 2) Deaths 3) Migration Immigration = migration into a population Emigration = migration out of a population (minor factor) (major factor - natural populations) (major factor) (Births - Deaths) + (Immigrants - Emigrants)  Population Size =

+ - Ultimate size of population = balance between opposing forces Chapter 38: Population Growth & Regulation Ultimate size of population = balance between opposing forces Biotic Potential: Maximum rate at which a population can increase in size (ideal conditions) (1st Force) + Maximize Births Minimize Deaths Balance (Births - Deaths)  Population Size = Maximize Deaths Minimize Births - Environmental Resistance: Limits set by the environment (e.g. food availability, competition, predation) (2nd Force)

(10%) Biotic potential can produce Exponential Growth: Chapter 38: Population Growth & Regulation Biotic potential can produce Exponential Growth: Continuously accelerating increase in population size Growth Rate: Measure of  in population size / time Growth Rate (r) = Birth Rate (b) - Death Rate (d) 1500 / 10,000 - 500 / 10,000 (10%) 0.10 = increase / person / year 0.15 births / person / year - 0.05 deaths / person / year Population Growth: # of individuals added to population / time Population Growth = Growth Rate (r) x Population Size (N) 0.10 increase / person / year x 10,000 People 1000 = new individuals / year New Population Size = 11,000

Biotic potential can produce Exponential Growth: Chapter 38: Population Growth & Regulation Biotic potential can produce Exponential Growth: New Population Size = 11,000 2nd year: 0.10 x 11000 = 1100 3rd year: 0.10 x 12100 = 1210 4th year: 0.10 x 13310 = 1331 5th year: 0.10 x 14641 = 1464 Exponential Growth (ever-accelerating) (Figure 38.1) J curve

Factors Affecting Biotic Potential: Chapter 38: Population Growth & Regulation Factors Affecting Biotic Potential: 1) Age at which organism first reproduces ( age =  rate) 2) Frequency with which reproduction occurs ( freq. =  rate) 3) Average number of offspring / event ( # =  rate) 4) Length of organism’s life span ( lifespan =  rate) 5) Death rate of individuals (ideal condition -  rate =  rate) (Figure 38.1) (Figure 38.3)

Exponential growth cannot continue indefinitely: Chapter 38: Population Growth & Regulation Exponential growth cannot continue indefinitely: Boom-and-Bust Cycles: Rapid population growth followed by massive die-off (short-lived organisms) (Environmental Resistance Predominates) (Biotic Potential Predominates)

Exponential growth cannot continue indefinitely: Chapter 38: Population Growth & Regulation Exponential growth cannot continue indefinitely: Boom-and-Bust Cycles: Rapid population growth followed by massive die-off (short-lived organisms) Example: Lemmings

Environmental resistance stabilizes population growth for many Chapter 38: Population Growth & Regulation Environmental resistance stabilizes population growth for many long-lived organisms (no boom-bust cycles): S-curve (Figure 35.8) Growth Rate (= 0) Carrying Capacity: The maximum population size that an ecosystem can support indefinitely

Carrying Capacity Determined By: Chapter 38: Population Growth & Regulation Carrying Capacity Determined By: 1) Renewable Resources  Nutrients, water, light Replenished by natural processes (can be damaged) 2) Non-renewable Resource  Space Factors of Environmental Resistance Maintaining Populations At / Near Carrying Capacity: 1) Density-Independent Factors: Limit pop. size regardless of pop. density 2) Human Activities Pesticides / pollutants Habitat destruction 1) Weather

(Pg. 798 - Scientific Inquiry) Chapter 38: Population Growth & Regulation Factors of Environmental Resistance Maintaining Populations At / Near Carrying Capacity: 2) Density-dependent Factors: Factors more effective as population size increases ** Most Important ** a) Predation: One organism (predator) kills another organism (prey) to eat More abundant prey = more chance of meeting predator Predator - Prey Cycles (Pg. 798 - Scientific Inquiry)

Factors of Environmental Resistance Maintaining Populations Chapter 38: Population Growth & Regulation Factors of Environmental Resistance Maintaining Populations At / Near Carrying Capacity: 2) Density-dependent Factors: Factors more effective as population size increases b) Parasitism: One organism (parasite) feeds off another organism (host) without killing it More abundant hosts = easier for parasite to find Malaria Bark Beetle Lamprey

Factors of Environmental Resistance Maintaining Populations Chapter 38: Population Growth & Regulation Factors of Environmental Resistance Maintaining Populations At / Near Carrying Capacity: 2) Density-dependent Factors: Factors more effective as population size increases c) Competition: Organisms compete among each other for limited resources (e.g. food) Two types of competition: 1) Interspecific Competition: between species 2) Intraspecific Competition: within species *More Intense* Contest Competition Scramble Competition

Types of Spatial Distribution: Chapter 38: Population Growth & Regulation Populations Exhibit Differing Spatial Distributions: Distribution: Spatial pattern in which population members are arranged in given area. Types of Spatial Distribution: 1) Clumped: Population members live in defined groups Family Groups (e.g. wolves) Social Groups (e.g. Flamingos)

Types of Spatial Distribution: Chapter 38: Population Growth & Regulation Populations Exhibit Differing Spatial Distributions: Distribution: Spatial pattern in which population members are arranged in given area. Types of Spatial Distribution: 2) Uniform: Relative constant distance between population members Territorial Groups (e.g. penguins) (e.g. sage)

Types of Spatial Distribution: Chapter 38: Population Growth & Regulation Populations Exhibit Differing Spatial Distributions: Distribution: Spatial pattern in which population members are arranged in given area. Types of Spatial Distribution: 3) Random: Members scattered haphazardly across landscape Many plants (e.g. trees) Very rare in animals

Populations Show Characteristic Patterns of Survivorship: Chapter 38: Population Growth & Regulation Populations Show Characteristic Patterns of Survivorship: Survivorship Curve: Graph depicting # of individuals in an age class against their age Late-loss (e.g. human) 1) Late-loss Populations: Low infant death rates Produce few offspring Age of members # of members surviving 3) Early-loss Populations: Early-loss (e.g. plants) 2) Constant-loss Populations: Constant-loss (e.g. birds) Constant death rate Produce variable offspring High infant death rates Produce many offspring

So How Do Humans Fit Into This? Chapter 38: Population Growth & Regulation So How Do Humans Fit Into This? (Figure 38.11) More hospitable environment More efficient food gathering  death rates

Doubling Time: 70 / growth rate (%) 70 / 1.4 = 50 years Chapter 38: Population Growth & Regulation Doubling Time: 70 / growth rate (%) 70 / 1.4 = 50 years 70 / 0.6 = 117 years (Figure 38.13)

The human population will stop its exponential growth… either we will Chapter 38: Population Growth & Regulation The human population will stop its exponential growth… either we will voluntarily reduce our birth rate, or various forces of environmental resistance will dramatically increase our death rates… the choice is ours... - Earth Watch (pg. 809)