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Ecology (Population Ecology (Density-Dependent Factors (Population Change…

- - - - Logistic Growth Model: Per capita rate of population growth approaches 0 as population size nears max capacity
      - dN/dt = rN((K-N)/K)
        
        K: Carrying capacity
        
        Logistical Model
        
        K-N: # of additional individuals environment can support
        
        (K-N)/K: Fraction of K that is available for growth
    - - Populations grown in lab lack predators and conditions found in nature (competition)
      - Logistic model assumes populations adjust to growth
      - Usually a delay before effects are realized
      - No food = populations decline over time not instantly
      - Logistic model gives a starting point for population growth
      - Predicts how rapidly population might increase after being reduced
      - Estimate critical size when populations become extinct
  - - - 3 Key Components
        
        How often
        
        How many offspring
        
        When reproduction begins
      - Age when reproduction begins varies by species
      - Loggerhead turtles wait 30 years, coho salmon waits 3-4 years
      - Semelparity: Reproduces once
      - Occurs on coho salmon and some plants (agave)
      - Iteroparity: Repeated reproduction
      - Loggerhead turtles produces 4 clutches, horses, fish, humans
      - Organisms vary in how many
    - - Trade-off between offspring number and resources parents can devote
      - The less offspring the more the parent invests in child
      - More offspring usually results in an absent parent
      - Plants/animals having children with a low chance of survival produce many small offspring (turtles)
      - Extra investment in parents increases offerings chances of survival
      - Primates only have one at a time
      - K-Selection: Selection for traits that are advantageous at high densities
      - Competition among individuals is stronger
  - - - Delta N/Delta t = R
        
        R: Difference between # births and deaths
        
        Population size
      - r Delta t
        
        Convert model to represent per individual
        
        Contribution an avg member of pop. makes to # individuals added or subtracted from pop during time interval
        
        R = r Delta t N
      - Delta N/Delta t = B - D
        
        Express simplified relationships
        
        Delta N: Change in population size
        
        Delta t: Time interval
        
        B: # births in pop. during time interval
        
        D: # deaths
      - Change in population size = Births + Immigrants
    - - Exponential Population Growth: Pattern of growth when pop. experiences ideal conditions
      - dN/dt: Rate population increases at each moment
      - Intrinsic Rate of Increase: Per individual rate at which pop. increases
      - Size of pop. growing exponentially inc. at rate per individual
      - New individuals constantly being added
      - Curves get steeper over time
  - - - Population needs negative feedback or it will never stop growing
      - Negative feedback provided by density-dependent regulation
      - Ex: fish death inc as density increased b/c not enough places to hide
      - Increased densities cause population growth to decrease
    - - Population Cycles
        
        Some animal populations fluctuate more than others
        
        Some birds have 3-4 a year, other birds have 9-11
        
        Can use radio collars o track individuals to determine cause of death
        
        Ecologists also set up electrical fences to prevent certain predators from coming in
      - Immigration, Emigration, Metapopulations
        
        Metaopulation: Local populations are linked
        
        Local pop in metapop occupy patches of suitable habitat
        
        Patches vary in size, quality, and isolation
        
        Factors influencing population size move among populations
      - Stability and Fluctuation
        
        Weather, food availability, predators can cause population to fluctuate
        
        In cold weather, moose population decreases
        
        When moose population increases, so do parasites and predators that then shrink population
    - - Study birth rates, death, immigration, and emigration to look at why population stops growing
      - Immigration and emigration offset = population grows when birth rate exceeds death rate
      - Density Independednt: Birth/death rate doesn't change with population density
      - Density Dependent: Death rate increases population density/ Birth rate falls with rising density
      - Variation in density-independent caused by change in temperature and precipitation - leads to change in pop. size
      - Density-Independent factor can't cause pop. decrease when large or increase when small
      - Pop. regulated when 1+ density-dependent factors cause size to dec when large
  - - - Density
        
        Determine by counting individuals in boundary
        
        Animals can be counted from planes
        
        Impossible to count everyone, so ecologists estimate density and population
        
        The more sample plots the more accurate
        
        Mark-recapture method: Estimate size of animal populations
        
        Changes all the time
        
        Emigration: Movement of individuals out of population and into others
      - Dispersion
        
        Local densities differ in area
        
        Clumped: Individuals aggregate in patches
        
        Plants and fungi aggregate
        
        Clumping can be caused by mating behaviors, weather, or food source
        
        Increase chances for predatation b/c very populated
        
        Uniform: Evenly Spaced
        
        Result from direct interactions between individuals
        
        Result of antagonistic social interactions
        
        Territoriality: Defense of bounded physical space
        
        Random: Unpredictable spacing
        
        Position of each individual is independent of others
        
        Occurs in absence of strong attraction/repulsion
        
        Plants established by wind are random
    - - Survivorship Curves: Plot of proportion in cohort alive at each age
        
        Curve needs large cohort
        
        Multiply proportion alive by cohort size = how many alive at start of year
        
        3 Types
        
        Type II: Constant death rate (ground squirrel, lizards)
        
        Type III: Curve drops at start, high death rates for young, flattens (organisms with lots of offspring)(fish, oyster,)
        
        Type I: Flat at start, low death rates vary and mid life, drops as death rates increase in older age-groups (large mammals, humans)
      - Reproductive Rates
        
        Identify reproductive output varies with # breeding females and age
        
        Can use direct sounds and mark and recapture
        
        Can determine how many females are breeding and how many offspring
        
        Reproductive output for birds/mammals is avg # female offspring
        
        Reproductive rates vary by species
      - Life Tables: Summarizes survival/reproductive rates in specific age-groups
        
        Cohort: Group of individuals of same age
        
        Important to keep track of number offspring in each age-group
        
        Usually focus on females only
        
        Population looked at as females giving birth to females
  - - - Age Structure
        
        Age Structure: # of individuals of each age in population
        
        Graphed as pyramid
        
        In U.S. age structure is even, expected to grow with immigrants
        
        Predict population growth trend and illuminate social conditions
        
        Less employment and education opportunities
      - Infant Mortality and Life Expectancy
        
        Infant Mortality: # of infant deaths per 1,000 live births
        
        Life expectancy at birth: Predicted avg length of life at birth
        
        Life expectancy varies depending on location
        
        Reflects quality of life
        
        Infant mortality is high, parents have more children
      - Patterns of Population Change
        
        Population dynamics vary from region
        
        In stable region, birth rate = death rate
        
        Demographic Transition: Movement from high birth rate and death toward low birth and death rate
        
        Associated with increase in quality of life
        
        When reproduction rate is higher than death rate, population will decline if no immigration
        
        Humans can control family sizes
        
        Leading to delayed reproduction means decrease in population growth rate
    - - Estimates of Capacity
        
        Hard to estimate
        
        Use logistic equation or generalize from existing maximum population density and multiply by area or limiting factors
      - Limits
        
        Ecological Footprint: Summarize aggregate land/water area required by person, city, nation
        
        Human Constraints: Need for food, water, fuel, building materials, clothing, transportation
        
        Estimate footprint by adding land and divide by size of population
        
        Global Hectare: Land/water with productivity equal to avg biologically productive areas on Earth
        
        Assessed by energy use
        
        Resource use per person and population density determines global ecological footprint
- - - - Pelagic Zone
        
        Aphotic Zone: Little light penetrates
        
        Abyssal Zone: Part of ocean 2,000-6,000m below
        
        Benethic Zone: Made of communities of organisms
        
        Detritus: Source of food for ethnic species
        
        Photic zone: Sufficient light for photosynthesis
      - Sun warms whatever it can touch
      - Thermocline: Layer of abrupt temperature change
      - Turnover: Semiannual mixing of water resulting in changing temp profiles
      - Oxygenated water to botton, nutrient rich water to surface
      - Communities distributed according to water depth, light, distance from shore, open water/bottm
  - - - Ability of species to survive is limited by predators
      - Presence/Absense of pollinators, food, parasites, pathogens, and competition can limit
    - - Salinity
        
        Limit animals ability to osmoregulate
        
        Hypertonic to Hypotonic
        
        Some animals can switch between salt and freshwater, others can't
      - Sunlight
        
        Energy that drives ecosystems
        
        Too little = Not enough photosynthesis
        
        Too much = Too hot, animals unable to cool themselves
        
        At low elevations, shade causes for competition for light
        
        At high elevations, sun damages DNA and protein
      - Water and Oxygen
        
        Variation in water availability
        
        Threat of desiccation
        
        Frogs depend on moist skin for gas exchange
        
        Deep waters don't have rapid exchange of gases so less O2
      - Rocks and Soil
        
        pH, mineral composition, physical structure of rocks/soil lit distribution of plants + animals
        
        Soil to acidic or basic, affects solubility of toxins and nutrients
        
        Structure of substrate determines organisms above and below
      - Temperature
        
        Environmental temp affects biological processes
        
        Freeze below 0C, proteins denature above 45C
        
        Animals use energy to regulate internal temp
        
        Thermophiles can live outside temp range
        
        Shift in one species affects others
    - - Expansion and Radiation
        
        Range Expansion: Organisms reach where they didn't exist before
        
        Bubulcus ibis migrated from Africa/Europe to South America
        
        Over time it can lead to evolution of new species
      - Species Transplants
        
        For a dispersement to be successful the new species has to reproduce
        
        If successful, species potential range is larger than actual range
        
        New species disrupts ecosystems
        
        Therefore scientists don't introduce new species to study the idea. They study the past
  - - - Named after physical/climate features and vegetation
      - Characterized by microorganisms, fungi, animals
      - Ecotone: Area of intergradation
      - Canopy: Upper layer of vegetation
      - Layers: Canopy, low-tree, shrub, ground, herbaceous plants, floor, root
      - Species vary in each biome
    - - Fires kill woody plants
      - Hurricanes give new species a change in tropical forests
      - Biomes are patchy and contain multiple communities
      - Humans alter most biomes
    - - Climate influences location of terrestrial biome
      - Temperature and precipitation also affect location
      - Climograph: Annual mean temperature and precipitation
      - Climograph based on annual averages
  - - - Bodies of Water
        
        Oceans cool the air above b/c of high specific heat
        
        Cool misty climate helps ecosystems along coast
        
        Keeps temperatures moderate
        
        Cools hot land, warms cold land
        
        Can also create hot arid climate
      - Mountains
        
        Influence the air over land
        
        Release moisture on windward side
        
        Absorbs moisture on leeward side
        
        Affect sunlight, local temp, and rain
      - Seasonality
        
        Earth's tilt causes seasonal cycles, day length, and temp
        
        Sun angle causes seasonal changes which alter ocean currents
        
        More nutrient rich water = more phytoplankton = more fish
    - - Shade, evaporation, wind can change local climate
      - Open areas in forests get more climate change b/c they experience sun and wind
      - In forest, ground is wet
      - Abiotic: Nonliving
      - Biotic: Living
    - - Determined by input of solar energy and Earth's movement
      - Sun warming Earth causes different temp, air/water movement
    - - Caused by increase in greenhouse gases
      - Wind/Rain patterns changing, extreme weather
      - Animals able live in new climates will survive, animals unable to live will move somewhere they are or die
- - - - Optimal Foraging Model: Natural selection should favor foraging behavior minimizing cost and maximizing benefit
        
        Foraging behavior is a compromise between benefits of nutrition and cost of obtaining food
      - Risk and Reward
        
        Forager risks predation
        
        Influences foraging behavior
        
        Mule deer feed in open areas to avoid predators even though there isn't variation in food
    - - Parental Care
        
        Young animals can't care for themselves and require 1+ parents to find food
        
        Could be why birds are monogamous
        
        When baby birds can care for themselves, males don't benefit and don't stay
        
        Males maximize reproductive success by mating with multiple
        
        Certainty of paternity is low when egg laying and mating are far apart but high when they occur together
      - Selection and Mate Choice
        
        Mate Choice by Female
        
        Intersexual Selection
        
        Males with desirable traits mate and pass on those traits
        
        Stalk-eye flies prefer males with long eyestalks since it correlates with health and vitality
        
        Healthy mate produces offspring that survive to reproduce
        
        Mate choice can be influenced by imprinting
        
        Mate-Choice Copying: Individuals in population copy mate choice of others
        
        Female guppies copied model female in mate choice
        
        Male Competition
        
        Intersexual
        
        Reduce variation among males
        
        Agonistic behavior: Contest to see who gains access to resource
        
        Behavioral and morphological variation in males is high in some vertebrate species
      - Sexual Dimorphism
        
        Monogamous: One male and one female
        
        Polygamous: Indiviudal mating with several others
        
        In some species, mating has no strong pair-bonds
        
        Others mate for life
        
        Sexual dimorphism results from sexual selection
      - Game Theory: Evaluates alternate strategies in situations where the outcome depends on all individuals
        
        Fitness can be influenced by behavioral phenotypes
        
        In side-blotched lizards, natural selection favors all three colors because each has an advantage over another
  - - - Ground squirrel gives warning to others when there is a predator but lets predator know where they are
      - Bees sting intruders to protect others in hive but kills themselves
      - Rats sacrifice themselves to protect queen and king rats
    - - Hamilton's Rule
        
        Inclusive Fitness: Total effect of individual on genes by producing offpsring and aiding others to produce
        
        Coefficient of Relatedness: Fraction of genes that are shared
        
        (r)fraction of genes that are shared x (B)average number of extra offspring > (C)fewer offspring
        
        Kin Selection: Natural selection favors altruism by enhancing reproductive success of relatives
        
        Weakens with hereditary distance
      - Reciprocal Altruism: Altruistic behavior between unrelated ppl, individual benefits in future
        
        Help between species
        
        Help when might meet again and would receive consequences for not helping
        
        Tit for tat
        
        Help if altruism is returned
    - - Variation in Prey Selection
        
        What garter snakes eat depends on where they are located
        
        Coastal snakes feed on slugs, inland snakes feed on frogs and leeches
        
        If offered other food, they won't eat it
        
        Vary in their ability to recognize and respond to certain smells
      - Variation in Migratory Patterns
        
        Some blackcaps spent winters in Britain and some migrated
        
        Different migration patterns reflect genetic differences
    - - Humans "playing" prepare us for unexpected events
      - Sociobiology: The study of social behavior based on evolutionary theory
      - Certain behaviors are expressions of genes
    - - A gene in fruit flies called "fur" controls courtship ritual that is produced in males attracting them to females
      - Difference in behavior can be b/c of variation of gene
      - Antidiuretic hormone (vasopressin): Peptide released during mating to pair-bond
      - ADH also regulates postdating behaviors
  - - - Cross-Fostering Study: Young of one species are placed in care of adult from another species
      - Offspring's behavior changes in the situation
      - Twin Study: Comparing behavior of identical twins raised separately
    - - Associative Learning
        
        Associative Learning: Ability to associate one environment feature with another
        
        Classical Conditioning: Stimulus is associated with a particular outcome
        
        Ring a bell before giving a dog food, dog eventually salivates at the sound of the bell
        
        Operant Conditioning: Trial and error learning
        
        Rats learn to get food using a lever through trial and error
        
        Some animals can't learn to make certain associations
        
        The associations animals can make occur in nature
      - Cognition and Problem Solving
        
        Cognition: Process of knowing that involves awareness, reasoning, recollection, and judgement
        
        Group of bees learned to choose am with same or different color to receive food reward
        
        Problem Solving: Ability to come up with a plan to overcome an obstacle
        
        Chimpanzees given boxes can stack the boxes to reach food high up
      - Learning and Maps
        
        Spatial Learning: Establishment of memory that reflects environment's spacial structure
        
        Wasps know where there home is even though it is hidden using landmarks
      - Learned Behaviors
        
        Some learned behaviors happen in a short time some take longer
        
        If sparrow doesn't hear song in first 50 days, never develops adult song
        
        Sensitive period is when sparrow learns song, second learning phase is when it starts singing
      - Imprinting: Establishment of long-lasting behavioral response to individual/object
        
        Sensitive Period: When imprinting takes place
        
        Can be made between species
      - Social Learning: Learning through observations
        
        Young chimpanzees learn to crack nuts by watching experienced chimpanzees
        
        Monkeys give certain calls for certain animals and the other monkeys react depending on call
        
        If an infant gives the call, the adults will confirm before giving the call again
        
        Culture: System of info transfer through social learning or teachings
  - - - Animals adjust to environment changes using their Circadian clock
      - Navigate using the sun, the North Star, magnetic fields
    - - Circadian clock regulate sleep and activity in animals
        
        Synchronized with light and dark cycles
        
        Circannual Rhythms: Clocks based on yearly cycle of seasons
        
        Can be based on other factors like the moon
    - - Fixed Action Pattern: Reacting to a certain stimulus (reaction wasn't learned)
      - Sign Stimulus: Trigger for fixed action pattern
    - - Forms of Communication
        
        4 Modes of Communication: Visual, Chemical, Tactile, Auditory
        
        Stimulus-Response Chain: Response to stimulus is the stimulus for next behavior
        
        Form of communication between animal depends on lifestyle and environment
        
        Terrestrial animals use olfactory and auditory
        
        Humans and birds use visual and auditory
      - Pheromones: Acts like hormone influencing physiology and behavior
        
        Common in mammals and insects for reproductive behavior
        
        Can also serve as alarm signals
        
        Basis of chemical communication for fruit fly courtship