Campbell Chap 40 Population Ecology Lecture Notes PDF

Chapter 40: Population Ecology and the Distribution of Organisms Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Discovering Ecology Ecology =study of interactions between organisms and environment Study interactions ranging in scale from individual orga...

Chapter 40: Population Ecology and the Distribution of Organisms Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Discovering Ecology Ecology =study of interactions between organisms and environment Study interactions ranging in scale from individual organisms to entire globe Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Exploring the Scope of Ecological Research Global Ecology Organismal ecology considers how organism’s structure, physiology, and behavior meet environmental challenges Landscape Ecology Population ecology considers factors affecting population Ecosystem Ecology size over time – Population = group of individuals of same species living Community Ecology in same area Population Ecology Community ecology considers how interactions between species affect community structure and organization – Community = group of populations of different species in same area Organismal Ecology Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Exploring the Scope of Ecological Research Ecosystem ecology emphasizes energy flow and Global Ecology chemical cycling between organisms and environment – Ecosystem =community of organisms in area and Landscape Ecology physical factors with which they interact Landscape ecology focuses on factors controlling Ecosystem Ecology exchanges of energy, materials, and organisms across Community Ecology multiple ecosystems – Landscape (or seascape) = mosaic of connected Population Ecology ecosystems Global ecology is concerned with biosphere, or global ecosystem, which is sum of all planet’s ecosystems and landscapes Organismal Ecology– Examines influence of energy and materials on organisms across biosphere Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Learning Outcomes Earth’s Climate Influences the Distribution of Terrestrial Biomes Aquatic Biomes Are Diverse and Dynamic Systems That Cover Most of Earth Interactions Between Organisms and the Environment Limit the Distribution of Species Biotic and Abiotic Factors Affect Population Density, Dispersion, and Demographics The Exponential and Logistic Models Describe the Growth of Populations Population Dynamics Are Influenced Strongly by Life History Traits and Population Density Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  What is Climate? Long-term prevailing weather conditions in area constitute its climate – 4 major physical components are: 1. Temperature 2. Precipitation 3. Sunlight 4. Wind – Abiotic factors are nonliving chemical and physical attributes of environment – Biotic factors are other organisms that make up living component of environment Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Global Climate Patterns Determined largely by solar energy and planet’s movement in space Warming effect of sun causes temperature variations, which drive evaporation and circulation of air and water – Causes latitudinal variations in climate Latitudinal Variation in Sunlight Intensity Latitudinal Variation in Sunlight Intensity: Atmosphere 90N (North Pole) Caused by curved shape of Earth Low angle of incoming sunlight Sunlight strikes tropics, regions between 23.5° 23.5N (Tropic of Cancer) north and 23.5° south latitude, most directly Sun overhead at equinoxes 0 (Equator) At higher latitudes, where sunlight strikes Earth at oblique angle, light is more diffuse 23.5S (Tropic of Capricorn) Low angle of incoming sunlight 90S (South Pole) Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Global Air Circulation and Precipitation Patterns: Warm, wet air rising near equator creates precipitation in tropics Dry air descending at 30° N and S latitudes absorbs moisture from land, creating desert conditions – This pattern is repeated at 60° N and S latitudes and poles Global Air Circulation and Precipitation Patterns 66.5N (Arctic Circle) Variation in speed of Earth’s ZO NE 60N I D Descending rotation at different latitudes 30N AR dry air Westerlies absorbs results in major wind 30N moisture. patterns Northeast trades Ascending moist air Trade winds blow E to W in 0° releases moisture. tropics Southeast trades Westerlies blow W to E in 30S 0° temperate zones Westerlies 60S Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved 66.5S (Antarctic Circle)  Seasonal Variation in Sunlight Intensity Climate is affected by: 1. Seasonality 2. Large bodies of water March equinox: Equator faces sun directly; neither pole tilts toward sun; all regions on Earth experience 12 hours of daylight December solstice: Northern Hemisphere tilts and 12 hours of darkness. 3. Mountain ranges away from sun and has shortest day and longest night; Southern Hemisphere tilts toward sun and has longest day and shortest night. Sun Seasonal variations of light and temp increase with increasing latitude Seasonality is caused by: Constant tilt 60°N of 23.5° – Tilt of Earth’s axis of rotation June solstice: Northern Hemisphere 23.5°N – Its annual passage around sun tilts toward sun and has longest day and shortest night; Southern 0° (Equator) Hemisphere tilts away from sun and 23.5°S September equinox: Equator faces sun has shortest day and longest night. directly; neither pole tilts toward sun; all regions on Earth experience 12 hours of daylight and 12 hours of darkness. Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Circulation of Surface Water in the Oceans Around North America Changing wind patterns alter ocean currents, causing upwelling, movement of cold, nutrient rich water from ocean floor to surface Ocean currents influence coastal climates by heating or cooling overlying air masses that pass across land Labrador Current California Gulf Stream Current PACIFIC ATLANTIC OCEAN OCEAN Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved How Large Bodies of Water and Mountains Affect Climate Large bodies of water moderate climate of nearby terrestrial environments – Day: air rises over warm land and draws a cool breeze from water across land – Night: air rises over warmer water and draws cooler air from land back over water, which is replaced by warmer air from offshore Rising air releases moisture on windward side of mountains and creates “rain shadow” as it absorbs moisture on the leeward side – Many deserts are found in “rain shadow” of mountains Air that encounters mountains flows upward, cools at higher altitudes, and releases water as rain and snow. Cool air flows inland from the water, moderating temperatures near the shore. Less moisture is left in the air reaching the leeward side, Windward side Leeward side which therefore has little of mountains of mountains precipitation. This rain shadow can create a desert on the back side of the mountain range. Mountain range Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Ocean  Distribution of Major Terrestrial Biomes Biomes= major life zones characterized by: – Vegetation type (terrestrial biomes) or – Physical environment (aquatic biomes) Climate determines vegetation type and limits distribution of terrestrial biomes 30°N Tropic of Cancer Latitudinal patterns in terrestrial biomes Equator reflect latitudinal patterns of climate Tropic of Capricorn 30°S Key Tropical forest Temperate broadleaf forest Savanna Northern coniferous forest Desert Tundra Chaparral High mountains Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Temperate grassland Polar ice  Learning Outcomes Earth’s Climate Influences the Distribution of Terrestrial Biomes Aquatic Biomes Are Diverse and Dynamic Systems That Cover Most of Earth Interactions Between Organisms and the Environment Limit the Distribution of Species Biotic and Abiotic Factors Affect Population Density, Dispersion, and Demographics The Exponential and Logistic Models Describe the Growth of Populations Population Dynamics Are Influenced Strongly by Life History Traits and Population Density Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Interactions Between Organisms and Environment Limit Distribution of Species Species distributions are consequence of both ecological factors and evolutionary history Geographic isolation can result in evolution of unique lineages restricted to specific areas Ecological factors, including food availability, predators, and temperature, can influence movement of species outside of their native range Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Dispersal and Distribution Dispersal =movement of individuals or gametes away from their area of origin or centers of high population density – Dispersal contributes to =global distribution of organisms Transplants are organisms that are intentionally or accidentally moved to areas where they were previously absent – Species transplants can disrupt communities or ecosystems Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Biotic Factors limiting species distributions Interactions with other species can limit species distributions Biotic factors can include: – Predation – Herbivory – Mutualism – Parasitism – Competition Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Effects of Feeding by Sea Urchins on Seaweed Distribution 100 Sea urchins are important herbivores in marine ecosystems 80 Feeding by sea urchins can limit Urchins removed Seaweed cover (%) distribution of seaweed 60 40 20 Control (urchins present) 0 August February August February 1982 1983 1983 1984 Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Abiotic Factors limiting species distributions Physical conditions limit dispersal Abiotic factors include: – Temperature – Water- terrestrial organisms reflects their ability to obtain and store water to avoid desiccation – Oxygen- can be limiting in some aquatic systems and soils because it diffuses slowly in water – Salinity- salt concentration, affects water balance of organisms through osmosis – Sunlight- energy source for photosynthetic organisms – Rocks and soil- limit distribution of organisms through effects on pH, mineral composition, and physical structure of substrate Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Learning Outcomes Earth’s Climate Influences the Distribution of Terrestrial Biomes Aquatic Biomes Are Diverse and Dynamic Systems That Cover Most of Earth Interactions Between Organisms and the Environment Limit the Distribution of Species Biotic and Abiotic Factors Affect Population Density, Dispersion, and Demographics The Exponential and Logistic Models Describe the Growth of Populations Population Dynamics Are Influenced Strongly by Life History Traits and Population Density Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Population Density, Dispersion, and Demographics Populations are described by their boundaries and size Population ecology explores how biotic and abiotic factors influence density, distribution, and population size Density =number of individuals per unit area or volume Dispersion =pattern of spacing among individuals within population boundaries Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Population Density: Dynamic Perspective Density = dynamic characteristic resulting from processes that add and remove individuals from population Births Deaths Additions – Birth – Immigration: influx of new individuals from other areas Removal Births and Deaths and immigration emigration – Death add individuals to remove individuals a population. from a population. – Emigration: movement of individuals out of a population Immigration Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Emigration  Patterns of Dispersion: Clumped Environmental and social factors influence spacing of individuals in population Most common pattern of dispersion is clumped, in which individuals aggregate in patches – Influenced by: ▪resource availability ▪mating behavior ▪group predation and defense strategies (a) Clumped. Sea stars group together where food is abundant. Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Patterns of Dispersion: Uniform Uniform dispersion is one in which individuals are evenly spaced In plants, secretion of chemicals that inhibit growth or germination can cause uniform dispersion In animals, social interactions such as territoriality, defense of bounded space against other individuals, can cause uniform dispersion (b) Uniform. King penguins and other birds that nest on small islands often Copyright exhibit © 2020, uniform 2016, spacing, 2014 Pearson maintained Education, by Reserved Inc. All Rights aggressive interactions between neighbors.  Patterns of Dispersion: Random Position of each individual is independent of other individuals – Absence of strong attractions or repulsions among individuals can cause random dispersion – Key physical or chemical factors are relatively constant across area (c) Random. CopyrightDandelions grow © 2020, 2016, 2014 from windblown Pearson seeds Education, Inc. that Reserved All Rights land at random and later germinate.  How can we estimate the population size? Population size and density can be estimated by extrapolation from small samples or indicator of population size (like number of nests) With estimate of population size and range, ecologists can then determine population density. Understanding population size variation is key to ecological research – Apply to conservation biology ▪ Declining population size might signal declining health Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Estimating Population Size For sessile or sedentary organisms: count within defined area and total population can be extrapolated from that measurement. For mobile organisms: mark-and-recapture is useful Quadrats 1. Capture individual 2. Mark them 3. Capture more individuals-some original individuals will be recaptured Mark and recapture Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Demographics Demography =study of births, deaths, and migration rates of population over time – Summarized in life table Reproduction output Life table Age-specific summary of survival and reproductive rates within population Organized by cohort, group of individuals of same age, from birth to death Constructed for sexually reproducing species often ignore males because only females produce offspring Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Survivorship Curves Graphic way of representing survival rate data in life table Plot proportion or numbers of a cohort still alive at each age 3 general types 1,000 I Number of survivors (log scale) Type I: most mortality is late in life. – Large animals: humans, elephants, and whales 1,00 II Type II: consistent levels of mortality throughout life – Birds and many small mammals (squirrel) 10 Type III: high mortality at earliest stages of life cycle III – Small herbaceous plants 1 – small animals (mice, insects) 1 50 100 Percentage of maximum life span – other organisms that grow fast and reproduce early Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Animation: Investigating the Survivorship Curve of Oysters Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Learning Outcomes Earth’s Climate Influences the Distribution of Terrestrial Biomes Aquatic Biomes Are Diverse and Dynamic Systems That Cover Most of Earth Interactions Between Organisms and the Environment Limit the Distribution of Species Biotic and Abiotic Factors Affect Population Density, Dispersion, and Demographics The Exponential and Logistic Models Describe the Growth of Populations Population Dynamics Are Influenced Strongly by Life History Traits and Population Density Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Growth of Populations Unlimited growth occurs under ideal conditions In nature, growth is limited by various factors Change in population size can be defined by equation: Change in Immigrants Emigrants population  Births  entering  Deaths  leaving size population population If immigration and emigration are ignored, change in population size equals births minus deaths Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Exponential Growth Occurs under idealized conditions – Food is abundant 2,000 dN – All individuals reproduce at dt = 1.0N physiological capacity 1,500 dN Population size (N) = 0.5N Population increases in size by constant dt proportion at each instant in time 1,000 J-shaped curve of exponential growth characterizes populations: 500 – In new environments – Populations rebounding from 0 catastrophic events 0 5 10 15 Number Copyright © 2020, 2016, 2014 Pearson of generations Education, Inc. All Rights Reserved Exponential Growth in the African Elephant Population of Kruger National Park, South Africa 8,000 Elephant population size 6,000 4,000 2,000 0 1900 1910 1920 1930 1940 1950 1960 1970 Year Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved BioFlix Animation: Exponential Growth Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Carrying Capacity Exponential growth assumes unlimited resources In nature, resources are usually limited More realistic model limits growth by incorporating carrying capacity Carrying capacity (K) =maximum population size particular environment can support given its abundance of limiting resources As population approaches carrying capacity: – per capita birth rate (growth rate per individual) will decrease or – per capita death rate will increase Logistic population growth model, per capita rate of increase approaches zero as population density approaches carrying capacity – Logistic model of population growth produces sigmoid (S-shaped) curve Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Population Growth Predicted by the Logistic Model Exponential growth Population growth is highest when population 2,000 dN = 1.0N size is at half carrying capacity dt At half carrying capacity, per capita rate of 1,500 increase remains relatively high and there Population size (N) K = 1,500 Logistic growth dN = 1.0N 1,500 – N are more reproducing individuals than at low dt 1,000 1,500 population size Population growth rate 500 begins slowing here. 0 0 5 10 15 Number of generations Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Learning Outcomes Earth’s Climate Influences the Distribution of Terrestrial Biomes Aquatic Biomes Are Diverse and Dynamic Systems That Cover Most of Earth Interactions Between Organisms and the Environment Limit the Distribution of Species Biotic and Abiotic Factors Affect Population Density, Dispersion, and Demographics The Exponential and Logistic Models Describe the Growth of Populations Population Dynamics Are Influenced Strongly by Life History Traits and Population Density Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Population Dynamics Are Influenced Strongly by Life History Traits and Population Density Study of population dynamics focuses on complex interactions between biotic and abiotic factors that cause variation in population size Organism’s life history comprises traits that affect its schedule of reproduction and survival – Age at which reproduction begins – How often organism reproduces – How many offspring are produced per reproductive episode Organism uses resources for: X Growth Body maintenance Reproduction Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  “Trade-offs” and Life Histories Organisms have finite resources – lead to trade-offs between survival and reproduction – kestrels that invest energy in caring for larger broods of chicks have reduced survival Selective pressures influence trade-off between number and size of offspring 100 Male Parents surviving the following winter (%) Female Plants and animals whose young are likely 80 to die often produce large numbers of 60 small offspring Extra investment by parent greatly 40 increases offspring’s chance of survival 20 0 Reduced Normal Enlarged broodPearson Copyright © 2020, 2016, 2014 size brood Inc. Education, size All Rights brood size Reserved  “Trade-offs” and Life Histories Selection for traits that are advantageous at high densities =K-selection Selection for traits that maximize reproductive success in low densities =r-selection External fertilization Internal fertilization Reproduce quickly Reproduce slowly Many offspring Fewer offspring Less parental investment More parental investment Unstable Environments Stable Environments Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Density dependent factors affect population growth Birth rate/death rate that is density independent does not change with population density Birth rate that decreases with population density or death rate that increases with density =density dependent Competition for resources Territoriality Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Disease Predation Intrinsic factors (physiologi Bioflix Animation: Density Dependence Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Density-Independent Effects Factors influence population size without regard for the population’s density. Cause widespread mortality independent of population density. Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved We have been focusing on a single population How they are characterized How they change in size over time Next, let’s discuss multiple populations of a single species Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Metapopulations Occupied patch Unoccupied patch Metapopulation is large population made up of smaller populations Most populations show uneven distribution across landscape. Patches of individuals are connected by occasional movements between them. Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved  Habitat Fragmentation Species survival depends on: Population health Ability to colonize new habitat Corridors Dispersal ability Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved Bioflix Animation: Predator-Prey Copyright © 2020, 2016, 2014 Pearson Education, Inc. All Rights Reserved