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Lecture Outlines Chapter 3 Environment: The Science behind the Stories 4th Edition Withgott/Brennan Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings This lecture will help you understand: • Population characteristics • Population ecology • Conservation biology Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Ecology is studied at several levels • Ecology and evolution are tightly intertwined • Biosphere = the total living things on Earth and the areas they inhabit • Ecosystem = communities and the nonliving material and forces they interact with • Community = interacting species that live in the same area Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Levels of ecological organization • Population ecology = investigates the quantitative dynamics of how individuals within a species interact • Community ecology = focuses on interactions among species • Ecosystem ecology = studies living and nonliving components of systems to reveal patterns - Nutrient and energy flows Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Organismal ecology: habitat • Habitat = the environment in which an organism lives - Includes living and nonliving elements - Scale-dependent: from square meters to miles • Habitat use = each organism thrives in certain habitats, but not in others • Habitat selection = the process by which organisms actively select habitats in which to live - Availability and quality of habitat are crucial to an organism’s well-being - Human developments conflict with this process Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Organismal ecology: niche • Niche = an organism’s use of resources and its functional role in a community - Habitat use, food selection, role in energy and nutrient flow - Interactions with other individuals • Specialists = species with narrow niches and very specific requirements - Extremely good at what they do, but vulnerable to change • Generalists = species with broad niches that can use a wide array of habitats and resources - Able to live in many different places Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Population characteristics • All populations show characteristics that help scientists predict their future dynamics • Population size = the number of individual organisms present at a given time - Numbers can increase, decrease, cycle or remain the same Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Population characteristics • Population density = the number of individuals within a population per unit area - High densities make it easier to find mates, but increase competition, and vulnerability to predation - Low densities make it harder to find mates, but individuals enjoy plentiful resources and space Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Population characteristics • Population distribution (dispersion) = spatial arrangement of organisms within an area - Random – haphazardly located individuals, with no pattern - Uniform – individuals are evenly spaced due to territoriality - Clumped – arranged according to availability of resources - Most common in nature Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Population characteristics • Sex ratio = proportion of males to females - In monogamous species, a 50/50 sex ratio maximizes population growth • Age Structure = the relative numbers of organisms of each age within a population - Age structure diagrams (pyramids) = show the age structure of populations Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Birth and death rates • Crude birth/death rates = rates per 1000 individuals • Survivorship curves = the likelihood of death varies with age - Type I: More deaths at older ages - Type II: Equal number of deaths at all ages - Type III: More deaths at young ages Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Four factors of population change • Natality = births within the population • Mortality = deaths within the population • Immigration = arrival of individuals from outside the population • Emigration = departure of individuals from the population • Growth rate formula = - (Crude birth rate + immigration rate) - (Crude death rate + emigration rate) = Growth rate Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Exponential population growth • Steady growth rates cause exponential population growth - Something increases by a fixed percent - Graphed as a J-shaped curve • Exponential growth cannot be sustained indefinitely - It occurs in nature with a small population and ideal conditions Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Typical Population Growth Curve Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings 14 Limiting factors restrain growth • Limiting factors = physical, chemical and biological characteristics that restrain population growth - Water, space, food, predators, and disease • Environmental resistance = All limiting factors taken together Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Carrying capacity • Carrying capacity = the maximum population size of a species that its environment can sustain - An S-shaped logistic growth curve - Limiting factors slow and stop exponential growth • Carrying capacity changes Humans have raised their carrying capacity by decreasing the carrying capacity for other species Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Population density affects limiting factors • Density-dependent factors = limiting factors whose influence is affected by population density - Increased risk of predation and competition for mates occurs with increased density • Density-independent factors = limiting factors whose influence is not affected by population density - Events such as floods, fires, and landslides Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Biotic potential and reproductive strategies vary • Biotic potential = the ability of an organism to produce offspring • K-selected species = animals with long gestation periods and few offspring - Have a low biotic potential - Stabilize at or near carrying capacity - Good competitors • r-selected species = animals which reproduce quickly - Have a high biotic potential - Little parental care Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings K-selected vs. r-selected species Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Population changes affect communities • As population in one species declines, other species may appear • Human development now displaces other species and threatens biodiversity - As Monteverde dried out, species from lower, drier habitats appeared - But, species from the cloud-forest habitats disappeared Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Challenges to protecting biodiversity • Social and economic factors affect species and communities - Nature is viewed as an obstacle to development - Nature is viewed as only a source of resources - Human population growth pressures biodiversity Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Costa Rica and its environment • Past economic and social forces still threaten Costa Rica’s species and ecological communities - Lush forests are seen as obstacles to agriculture and for timber - The country’s population grew to 3.34 million - Pasture land increased from 12% to 33% - Forests decreased from 80% to 25% - Species were declining and becoming endangered Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Costa Rica’s species were in danger • Few people saw the need to conserve biological resources - Until it became clear they were being rapidly lost Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Costa Rica is protecting its environment • The privately managed 10,500 ha (26,000 acre) Monteverde Cloud Forest Reserve was founded in 1972 - To protect the forest, its plants and animals • Costa Rica created the country’s first national parks and protected areas in 1970 - Centered on areas of spectacular scenery - Protecting valuable tropical dry forests, turtle nesting beaches, coral reef systems • Government support remains strong - Over 25% of its land is under some type of protection Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Costa Rico’s protection is paying off • Ecotourism: tourists visit protected areas - Providing thousands of jobs and billions of dollars to local economies • But parks are still under-protected and underfunded - Restoration is a step beyond preservation Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The carrying capacity is: • A. average # of offspring carried to term by a species • B. greatest # of different niches possible in a given area • C. potential growth in the number of species in an area • D. maximum population size that a given environment can sustain Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings True or False? • Ants are K-strategists Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Unregulated populations tend to increase by? • A. emigration • B. linear growth • C. exponential growth • D. pyramidal growth • E. immigration Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Interpreting Graphs and Data Which of the following graphs shows a population that will have fewer individuals in the future? (a) (b) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings (c) (d) QUESTION: Interpreting Graphs and Data Which type of distribution is a result of individuals guarding their territory? a) Random b) Uniform c) Clumped d) None of these Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Interpreting Graphs and Data What does this graph show? a) The effects of carrying capacity on population growth b) A population that keeps growing c) The effects of exponential growth d) The effects of increasing carrying capacity Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings