Population Ecology Chapter 9

Ch 9: Population Ecology How do populations change in structure in response to environmental stress? How do populations change in structure in response to environmental stress? What reproductive patterns do species use to enhance survival? What reproductive patterns do species use to enhance survival? What is conservation biology? What is conservation biology? How do humans impact populations, communities, and ecosystems? How do humans impact populations, communities, and ecosystems?

Population Dynamics  Population dynamics  Biotic potential (intrinsic rate of increase [r])  Biotic potential (intrinsic rate of increase [r])  Environmental resistance  Carrying Capacity  Exponential and Logistic Growth  Population Density Study of how populations change in size, density, and age distribution Rate at which a population would grow if it had unlimited resources Consists of all factors that would limit population growth Maximum number of individuals of a given specie that can be sustained indefinitely in given space A population that grows at every increasing increments Population growth that is steady and eventually levels off Number of individuals in a population in a particular space

Population Dispersion 1. Clumped-groups of individuals living in a tight knit cluster-fish, birds 2. Uniform-constant distance between individuals- better access to scarce resources a. Resources aren’t evenly spread out b. Better protection from predators c. Better able to find food-packs d. Temporary groups for mating 3. Random-Just that

Factors Affecting Population Size 1.Births 2.Deaths 3.Immigration 4.Emigration POPULATION SIZE= Biotic Factors – Env. Resistence

Exponential and Logistic Growth

Population Density Effects  Density-independent controls  Density-dependent controls Controls the size of the population regardless of the density of the population-natural disasters: fire, floods, habitat destruction Affects the population depending on its density-predation, parasitism

Types of Population Change Curves in Nature Population sizes follow one of these patterns. Population sizes follow one of these patterns. –Stable: fluctuates slightly  and  carrying capacity.

Types of Population Change Curves in Nature Population sizes follow one of these patterns. Population sizes follow one of these patterns. –Irruptive: explosion followed by crash to stable level.

Types of Population Change Curves in Nature Population sizes follow one of these patterns. Population sizes follow one of these patterns. –Cyclic: fluctuate w/reg pattern or boom-and-bust cycles.

Types of Population Change Curves in Nature Population sizes follow one of these patterns. Population sizes follow one of these patterns. –Irregular: erratic due to chaos or drastic change.

Role of Predation on Pop Size  Predator-prey cycles  Top-down control  Bottom-up control predator controls the population size of the prey prey controls the population size of the predator

Reproductive Patterns and Survival  Asexual reproduction  Sexual reproduction Offspring are exact genetic copies of a single parent Offspring are produced by combining sex cells from two parents Disadvantages: 1. males do not give birth-females have to produce twice as many offspring to continue specie 2. increased chance of defects when recombining chromosomes 3. courtship and mating consumes time and energy, results in disease and injury(males) Advantages: 1. greater genetic diversity 2. male can protect young

Reproductive Patterns and Survival r-selected species r-selected species –High rate of pop , small in size K-selected species K-selected species –Low rate of pop , large in size Many small offspring, small adults Little/ no parental care or protection of offspring Early reproductive age Most offspring die before reaching reproductive age Adapted to unstable climate and environmental conditions High population growth rate (r) Population size fluctuates wildly above and below carrying capacity (K) Generalist niche Low ability to compete Early successional species

Reproductive Patterns and Survival r-selected species r-selected species –High rate of pop , small in size K-selected species K-selected species –Low rate of pop , large in size Fewer, larger offspring, large adults High parental care and protection of offspring Later reproductive age Most offspring survive to reproductive age Adapted to stable climate and environmental conditions Lower population growth rate (r) Population size fairly stable and usually close to carrying capacity (K) Specialist niche High ability to compete Late successional species K-Selected Species Saguaro Elephant

Survivorship Curves Shows % of species in a population surviving at different ages. Three types: late loss, early loss, and constant loss. Life tables- show the numbers of individuals at each age on a survivorship curve.

Tonight’s Homework Read p Answer the following: 1. How does conservation biology differ from environmental science and wildlife management? 2. Describe 3 principles held by conservation biologists, and 3 questions they seek to answer. 3. Describe at least 7 general human habits that have modified natural ecosystems. 4. State and describe 5 principles for living more sustainably.

Human Impacts on Ecosystems  Habitat degradation and fragmentation  Ecosystem simplification  Genetic resistance Building sub-divisions, filling in wetlands, and building new roads through wilderness areas Loss of biodiversity, cropland, clear forests, and housing projects Overuse of pesticides breeds strains that are resistant to these chemicals

 Predator elimination  Introduction of non-native species  Overharvesting renewable resources  Interference with ecological systems Human Impacts on Ecosystems Killing off of predators; wolves, eagles, that compete with humans Food crops and livestock are beneficial; lamprey eels, zebra mussels, goby Overgrazing, excessive farming, illegal hunting, overharvesting of fish Increased emissions of carbon dioxide, CFCs, greenhouse gases disrupt normal processes: nutrient cycles, energy flow

Learning from Nature