AP Biology Population Ecology population ecosystem community biosphere organism

AP Biology Energy flows through ecosystems sun producers (plants) loss of energy secondary consumers (carnivores) secondary consumers (carnivores) primary consumers (herbivores) primary consumers (herbivores)

AP Biology  Trophic levels  feeding relationships  start with energy from the sun  captured by plants  1 st level of all food chains  food chains usually go up only 4 or 5 levels  inefficiency of energy transfer  all levels connect to decomposers Food chains Fungi Level 4 Level 3 Level 2 Level 1 Decomposers Producer Primary consumer Secondary consumer Tertiary consumer top carnivore carnivore herbivore Bacteria autotrophs heterotrophs sun

AP Biology Inefficiency of energy transfer  Loss of energy between levels of food chain  To where is the energy lost? The cost of living! only this energy moves on to the next level in the food chain 17% growth 50% waste (feces) 33% cellular respiration energy lost to daily living sun

AP Biology Ecological pyramid  Loss of energy between levels of food chain  can feed fewer animals in each level 1,000,000, , sun

AP Biology Humans in food chains  Dynamics of energy through ecosystems have important implications for human populations  how much energy does it take to feed a human?  if we are meat eaters?  if we are vegetarian?

AP Biology Food webs  Food chains are linked together into food webs  Who eats whom?  a species may weave into web at more than one level  bears  humans  eating meat?  eating plants?

AP Biology  Abiotic factors  sunlight & temperature  precipitation / water  soil / nutrients  Biotic factors  other living organisms  prey (food)  competitors  predators, parasites, disease  Intrinsic factors  adaptations Factors that affect Population Size

AP Biology Population Size  Changes to population size  adding & removing individuals from a population  birth  death  immigration  emigration

AP Biology Population growth rates  Factors affecting population growth rate  sex ratio  how many females vs. males?  generation time  at what age do females reproduce?  age structure  how females at reproductive age in cohort?

AP Biology Life table Demography  Factors that affect growth & decline of populations  vital statistics & how they change over time Why do teenage boys pay high car insurance rates? females males

AP Biology Survivorship curves  Graphic representation of life table Belding ground squirrel The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females.

AP Biology Age structure  Relative number of individuals of each age What do these data imply about population growth in these countries?

AP Biology Survivorship curves  Generalized strategies What do these graphs tell about survival & strategy of a species? Human (type I) Hydra (type II) Oyster (type III) Percent of maximum life span Survival per thousand I.High death rate in post-reproductive years II.Constant mortality rate throughout life span III.Very high early mortality but the few survivors then live long (stay reproductive)

AP Biology Trade-offs: survival vs. reproduction  The cost of reproduction  increase reproduction may decrease survival  age at first reproduction  investment per offspring  number of reproductive cycles per lifetime Natural selection favors a life history that maximizes lifetime reproductive success

AP Biology Reproductive strategies  K-selected  late reproduction  few offspring  invest a lot in raising offspring  primates  coconut  r-selected  early reproduction  many offspring  little parental care  insects  many plants K-selected r-selected

AP Biology Trade offs Number & size of offspring vs. Survival of offspring or parent Number & size of offspring vs. Survival of offspring or parent r-selected K-selected “Of course, long before you mature, most of you will be eaten.”

AP Biology Life strategies & survivorship curves Human (type I) Hydra (type II) Oyster (type III) Percent of maximum life span Survival per thousand K-selection r-selection

AP Biology Population growth change in population = births – deaths Exponential model (ideal conditions) dN = r i N dt N= # of individuals r= rate of growth r i = intrinsic rate t= time d= rate of change growth increasing at constant rate intrinsic rate = maximum rate of growth every pair has 4 offspring every pair has 3 offspring

AP Biology African elephant protected from hunting Whooping crane coming back from near extinction Exponential growth rate  Characteristic of populations without limiting factors  introduced to a new environment or rebounding from a catastrophe

AP Biology Regulation of population size  Limiting factors  density dependent  competition: food, mates, nesting sites  predators, parasites, pathogens  density independent  abiotic factors  sunlight (energy)  temperature  rainfall swarming locusts marking territory = competition competition for nesting sites

AP Biology K = carrying capacity Logistic rate of growth  Can populations continue to grow exponentially? Of course not! effect of natural controls no natural controls

AP Biology Time (days) Number of cladocerans (per 200 ml)  Maximum population size that environment can support with no degradation of habitat  varies with changes in resources  Every species has a diff. CC Time (years) Number of breeding male fur seals (thousands) Carrying capacity

AP Biology Your fridge is like all of the resources (food, water, free space) in an ecosystem. What if we want to throw a party? Imagine Your Fridge

AP Biology Imagine Your Fridge The fridge won’t replenish magically, and I don’t have the money to keep putting food in the fridge forever. So too many guests means that… So too many animals means that… Someone goes hungry… Not enough food/water/free space… And leaves the party.  And organisms die. 

AP Biology Carrying Capacity Time Population size Graph line = Population size at a specific time Dotted line = Carrying Capacity  Key Point #2: We can read a carrying capacity graph to predict changes in population size

AP Biology Carrying Capacity  When a population is BELOW its carrying capacity, it will INCREASE in size  Birth rate exceeds death rates Time Population size

AP Biology Carrying Capacity  But if it increases too much and rises ABOVE its carrying capacity, it will DECREASE in size  Death rate exceeds birth rate Time Population size

AP Biology Carrying Capacity  When a population is BELOW its carrying capacity, it will INCREASE in size  Birth rate exceeds death rates Time Population size

AP Biology Carrying Capacity  This happens over and over… but the increases and decreases get smaller and smaller… Time Population size

AP Biology Carrying Capacity  Until eventually, the population size BECOMES STABLE AT THE CARRYING CAPACITY  Birth rate = death rate Time Population size

AP Biology Changes in Carrying Capacity  Population cycles  predator – prey interactions K K K K

AP Biology Human population growth What factors have contributed to this exponential growth pattern? 1650  500 million 2005  6 billion Industrial Revolution Significant advances in medicine through science and technology Bubonic plague "Black Death" Population of… China: 1.3 billion India: 1.1 billion adding 82 million/year ~ 200,000 per day! adding 82 million/year ~ 200,000 per day! Doubling times 250m  500m = y () 500m  1b = y () 1b  2b = 80y (1850–1930) 2b  4b = 75y (1930–1975) Doubling times 250m  500m = y () 500m  1b = y () 1b  2b = 80y (1850–1930) 2b  4b = 75y (1930–1975)

AP Biology Distribution of population growth Time Developing countries Developed countries low fertility World population in billions World total medium fertility high fertility uneven distribution of population: 90% of births are in developing countries uneven distribution of population: 90% of births are in developing countries uneven distribution of resources: wealthiest 20% consumes ~90% of resources increasing gap between rich & poor uneven distribution of resources: wealthiest 20% consumes ~90% of resources increasing gap between rich & poor There are choices as to which future path the world takes… the effect of income & education

AP Biology Ecological Footprint USA Germany Brazil Indonesia Nigeria India Amount of land required to support an individual at standard of living of population Acres uneven distribution: wealthiest 20% of world: 86% consumption of resources 53% of CO 2 emissions uneven distribution: wealthiest 20% of world: 86% consumption of resources 53% of CO 2 emissions over-population or over-consumption?

AP Biology Ecological Footprint Based on land & water area used to produce all resources each country consumes & to absorb all wastes it generates deficit surplus