Inquiry into Life Twelfth Edition Lecture PowerPoint to accompany Inquiry into Life Twelfth Edition Sylvia S. Mader Chapter 33 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

33.1 The Scope of Ecology Modern ecology focuses on developing testable hypotheses. One goal of ecology is to develop models that explain and predict the abundance of populations.

Levels of Ecological Organization

33.2 Patterns of Population Growth Growth Rate = Per capita rate of increase Example: A population has 1000 members Birth rate = 30 / year Death rate = 10 /year The growth rate per year will be: 30 - 10 / 1000 = 0.02 = 2.0% per year

33.2 Patterns of Population Growth Biotic potential is the highest per capita rate of increase for a population Factors that influence biotic potential: Average number of offspring per reproduction Chances of survival until age of reproduction Age at first reproduction How often each individual reproduces

Patterns of Population Growth

33.2 Patterns of Population Growth J-shaped Curve Lag phase: Growth is small because the population is small Exponential growth phase: Growth is accelerating, and the population is exhibiting its biotic potential S-shaped Curve Deceleration phase: The rate of population growth slows down Stable equilibrium phase: Little if any growth takes place because births and deaths are about equal.

33.2 Patterns of Population Growth Carrying Capacity: The number of individuals of a species that a particular environment can support

33.2 Patterns of Population Growth Survivorship Growth curves assume all individuals are identical In real life, individuals are in different life stages Cohort-group of individuals born at the same time Plotting the number surviving over time gives us a survivorship curve Type I survivorship curve- most individuals survive until old age Ex: humans Type II- survivorship curve- decreases consistently over time Ex: songbirds Type III survivorship curve- most individuals die early Ex: oysters

Survivorship Curves

33.2 Patterns of Population Growth Human Population Growth Approximately 225,000 people are added to the world’s population every day. Approximately 82 million people are added to the world’s population every year. Current doubling time is 56 years (length of time it takes for population size to double)

World Population Growth

33.2 Patterns of Population Growth Human Population Growth More Developed Countries (MDC’s) versus Less Developed Countries (LDC’s) MDC’s Population growth is low and standard of living high Increased rapidly between 1850 and 1950 due to decreased death rate Then came a decrease in birth rate(demographic transition) Population growth in MDC’s has stabilized at 0.1% Germany, Hungary, Italy, Greece, Sweden are actually decreasing in size The United States has a low yearly growth rate (0.6%), however many people immigrate to the United States each year.

33.2 Patterns of Population Growth Human Population Growth More Developed Countries (MDC’s) versus Less Developed Countries (LDC’s) LDC’s Population growth is expanding rapidly and standard of living is low Population of LDC’s could reach 11 billion by 2100 Most of this increase in Latin America, Africa, and Asia Ways to decrease this expected growth are Establish/strengthen family planning programs Use social progress to reduce desire for large families Delay onset of childbearing

Age Structure Diagram

33.3 Regulation of Population Growth Two Types of Life History Patterns Opportunistic Pattern Many offspring are produced Short life spans Weeds and insects are examples Equilibrium Pattern Few offspring are produced Longer life spans Birds and mammals are examples

Life History Patterns

33.3 Regulation of Population Growth Abiotic and Biotic Factors Abiotic factors are called density-independent factors Weather, natural disasters Effects are the same for all sizes of populations Biotic factors are called density-dependent factors Competition, predation, parasitism Effects depend on the size of the population

33.3 Regulation of Population Growth Competition Occurs when members of two different species try to utilize the same resource Competitive Exclusion Principle: no two species can occupy the same ecological niche at the same time Ecological Niche: role organism plays in the community; includes habitat, resources used, and interactions Resource Partitioning Slight differences in the way a resource is utilized Decreases competition

Competition Between Two Laboratory Populations of Paramecium

Competition Between Two Species of Barnacles

33.3 Regulation of Population Growth Predation Predator-Prey Population Dynamics Cycling of predator and prey populations Occurs when either predators overkill prey, or when prey overuse resources and their numbers crash In either case, predator numbers also decrease from a decrease in food source

Predatory-Prey Cycling of a Lynx and a Snowshoe Hare

33.3 Regulation of Population Growth Predation Antipredator Defenses Coevolution is present when each of two species adapts in response to selective pressures imposed by the others.

Antipredator Defenses

33.3 Regulation of Population Growth Predation Antipredator Defenses Mimicry: One species resembles another species Can help capture food or avoid being preyed upon Batesian Mimicry: A prey that is not harmful mimics another species that has a successful antipredator defense. Warning colorations. Mullerian mimicry: Species that resemble each other all have successful defenses.

Mimicry Among Insects

33.3 Regulation of Population Growth Symbiosis: Close interactions between members of two species.

33.3 Regulation of Population Growth Parasitism Parasite derives nourishment from host Parasite benefits and the host is harmed Examples: Disease-causing Bacteria Ticks Leeches

33.3 Regulation of Population Growth Symbiosis Commensalism One species benefits, the other is not effected Examples: Clownfish and sea anemones Cattle egrets and cows

33.3 Regulation of Population Growth Symbiosis Mutualism Both members of the association benefit. Plants and pollinators Small fish and large organism

33.3 Regulation of Population Growth Ecological Succession A change in a community’s composition that is directional and follows a continuous pattern of extinction and colonization by new species. Primary Succession (land): Establishment of a plant community in a newly formed area where there is no soil formation Secondary Succession: The return of a community to its natural vegetation following a disturbance Pioneer Species: Plants that begin the process of secondary succession

Secondary Succession in a Forest

33.3 Regulation of Population Growth Ecological Succession Models of Succession Climax-pattern model: particular areas will always lead to a specific climax community Based on the fact that climate determines what plants survive Exact composition of climax community need be the same For example, the climax community in an area may be deciduous forest, but the tree species may differ Facilitation model: each successive community prepares the environment for the next Grasses are necessary before shrubs, and then shrubs before trees

33.3 Regulation of Population Growth Ecological Succession Models of Succession Inhibition model: colonizing species hold on to space until they die or are damaged Tolerance model: different species can colonize at the same time Random chance determines which arrives first