Midterm 1 Flashcards
Ecology
Scientific study of the abundance and distribution of organisms in relation to other organisms and environmental conditions
When did the interest in ecology peak?
After the rapid industrialization and the resulting environmental degradation of the earth
Ecological Systems
Biological entities that have both their own internal processes and yet interact with their external surroundings
What are the hierarchical set of ecological systems?
- Individual
- Population
- Community
- Ecosystem
- Biosphere
Individual
A living being; the most fundamental unity of ecology (unit of natural selection)
Population
Consists of individuals of the same species living in a particular area with both natural and political boundaries
What are the properties of a population?
- geographic range
- abundance
- density
- change in size and composition
Community
Composed of all populations of a species living together in a particular area
Ecosystem
Composed of one or more communities of living organisms interacting with their non living physical and chemical environment
Biosphere
All of the ecosystems on earth
How are distant ecosystems linked together?
By exchanges of wind and water and by the movement of organisms
What are the three approaches to ecology?
- Descriptive: observe/describe patterns
- Functional: understand dynamic relationships, mechanisms
- Evolutionary: understand historic reasons for adaptations
Motivation
Foundation for understanding broad scale differences among ecosystem
What are the 4 astronomical features that are important for ecological systems?
- Earth rotates on it’s axis once every 24 hours creating day and nights (temp fluctuations, nocturnal and diurnal creatures)
- The moon revolves around the earth once every ~28 days producing tidal variations (lunar cycles) (causes intertidal zones, drives fish activity and spawning)
- The earth is tilted on it’s axis at ~24 degrees (causes seasonal patterns)
- The earth revolves around the sun once every 365 days (combined with eh tilt produces seasonal variation in solar intensity)
What is the fuel for the vast majority of “all” living organisms?
Light!
What are the major components of climate?
- sunlight
- precipitation
- winds
- ocean currents
What purposes does the electromagnetic radiation from the sun serve?
- infrared radiation provides main source of heat
- photosynthetically active radiation provides nearly all energy for biological systems
- ultraviolet radiation, while damaging to many biological tissues, also serves an important role in the vision of many organisms
Greenhouse Effect
The process of solar radiation striking earth, being converted into infrared radiation, and then being absorbed and re-emitted by atmospheric gases
Latitudinal Pattern
Solar heating decreases away from the equator as sunlight is spread across larger areas
(Un-even heating due to the distribution of land masses)
What causes air to rise?
Solar Heating
What causes precipitation?
Rising air cools and moisture condenses causing precipitation
Hadley Cells
A large scale atmospheric convection cell in which air rises at the equator and sinks at medium latitudes (~30 degrees N and S)
Where do desserts occur?
At latitudes of 30 degrees N or S
Where do tropical rainforests occur?
At the equator
Mountain Rainshadow Effect
Air rises across mountain ranges, casing a dry rainshadow on the leeward side
Westerlies
Winds in high latitudes occur from the west toward the poles
Trade Windes
Wins in the Mid latitude come from the east towards the equator
Doldrums
Occur at the equator where there is not much wind
Coriolus Effect
The deflection in the pattern of air flow due to differences in rotation speed
How to water currents occur?
Water currents mimic wind patterns
What is upwelling?
Water moving offshore causes upwelling which can bring nutrient rich water to the photic zone which stimulates primary productivity by phytoplankton
El Niño Southern Oscillation (ENSO)
Abnormal sea surface warming in the eastern equatorial Pacific, also associated with East > West pressure difference
What are the components of El Niño?
- warmer water moves east, strong subtropical winds blow east to west
- low productivity, warm water in Galapagos due to reduced upwelling
- occurs every 2-7 years
What is La Niña?
Abnormally cool sea surface temps
Less dramatic, exaggeration of what we would consider a normal phenomenon
Pacific Decadal Oscillation (PDO)
Slow cyclic changes in dominant climate feature of the North Pacific
(Affects ocean productivity and temperatures)
(“Warm” and “cool” periods, regime shift every 20-30 years)
Biome Concept
Classifies biological systems according to similarity in climate
(Similar climates tend to have organisms with similar adaptations to the climate)
(Based on composition of terrestrial plant communities)
What are the 9 major biomes?
- tropical rainforest
- tropical seasonal forest/savannah
- subtropical desert
- woodland/scrubland
- temperate seasonal forest
- temperate grassland/cold desert
- temperate rainforest
- boreal forest
- tundra
- polar ice cap
Whitaker’s Biome Classification
Graph of average temperature vs. Average Precipitation
What are the limitations of whittaker’s biome classification?
- soils, consumers, disturbances and topography also affect plant life
- doesn’t directly relate to aquatic ecosystems
Mean
Average of all numbers (used when data is bell shaped)
Median
Middle number (used when data is skewed)
Hypotheses
Proposed explanation for an observed phenomenon (usually based on previous theory or work)
Proximate Hypotheses
Cause of immediate changes in individual phenotypes or interactions
Ultimate Hypotheses
Address the fitness costs and benefits of a response
What is the most important component of an ecological study?
Defining the question and tailoring your methods to appropriately answer it
What are the core principles of any quantitative study?
Randomization and Replication
What are the 5 types of study designs?
- Experimental: strongest inference
- Comparative: weak inference
- Retrospective: weak to medium inference
- Adaptive Management: weak inference
- Modeling: weak inference
What are the main components of an experimental study?
- involves treatments and controls
- must have multiple replicates of each treatment/control
- requires randomization of subjects to treatments and controls
- trade-offs between scale of experiment and number of replicates
- whole ecosystem experiments are rarely replicated but results are important
Factorial Design
Very common
- no control the experiment is the control
- 2x2 design
Components of Comparative Studies?
- involves measuring an ecological characteristic among many individuals/systems that differ in some interesting way
- used to identify patterns and correlations but do not confirm mechanisms
- excellent source of a hypothesis
- random sample is essential
What are the components of retrospective studies?
- analysis of historical time series
- used to understand temporal dynamics
- gives weak inference about mechanism
- sometimes crossed with spatial information
- ecological systems are highly variable, our observation of them are scale-dependent
What are the components of adaptive management?
- studies that treat management decisions as experiment treatments
- difficult to replicate
- the most relevant scale to applied issues
- the human response to a management policy is often the most interesting and important factor in these experiments
What are the components of modeling?
- formal descriptions of ecological systems
- set of equations that correspond to hypothesized relationships among the systems components
- conceptual, mathematical, simulation
- cheap and easy to run
- useful for answering “what if…” scenarios
- essentially impossible to validate for anything but the simplest models
Maturity
Age at 1st reproduction
Parity
Number of episodes of reproduction
Fecundity
Number of offspring per episode
Aging/senescence
Life span
What is the mark recapture equation?
N=M/r
(N= estimated population)
(M= number marked in sample 1)
(r=proportion of marked individuals in sample 2)
What is a negative aspect of investing in offspring?
Reduces the survival of the parents
What are the pros and cons of having a large clutch size?
-current reproduction may be improved by a larger clutch, but the future fecundity (or survival) may suffer
When does delayed reproduction occur?
-in organisms that become better batter et, have higher fecundity or attain larger size with age
Phenotypic Plasticity
Life history traits affected by the environment
How do you test for plasticity between populations of the same species?
Can test for plasticity between populations of the same species with reciprocal transplant experiments
Genotype x Environment Interaction
Each genotype responds differently to environmental condition
How do populations vary?
In space (distribution and dispersion) And in time (abundance and dynamics)
Distribution
Spatial extent of a species
-history, physical/environmental imitations and biological interactions shape species/populations boundaries
Dispersion
Can classify spatial arrangement along a gradient
What are the three forms of dispersion?
- Clumped (due to predator avoidance, patchy resources)
- Uniform (due to territoriality, strict competition for resources)
- Random (most common form. Stochasticity, disturbance, predators, patchy resources)
What is the general model of population growth?
Nt+1=Nt+Bt-Dt+It-Et
Exponential Growth
-grows by a proportion of current population
What are some examples of rapid population growth?
- humans
- previously exploited species that are now protected
- newly introduced species
What are some examples of rapid population decline?
- currently exploited species
- endangered species
Cohort Life Table
Follow one group from birth until the last one dies
Static Life Table
Census population for abundance in each age/stage combined with estimates of survival and reproductive output by age/stage
What are the limitations of a cohort life table?
Takes a longe time for long-lived organisms
Difficult to follow highly mobile organisms
Must be able to age/stage each organism (not always easy)
What are the terms used in a cohort life table?
- x= age
- lx= survivorship to age x
- sx= survival rate
- bx= fecundity at age x
What is the formula for the net reproductive rate?
Ro= sum lxbx
What is the equation for the generation time? (Average age at which an individual gives birth to offspring)
T= sum xlxbx/sumlxbx
What is the equation for rate of population increase and what do values equal to, above and below 0 represent?
Ra=ln(ro)/T
R>0 population is growing
R=0 population is stable
R<0 population is declining
Geometric Growth
populations reproduce only at limited time
Nt+1= Ntlambda
Exponential Growth
Populations reproduce continuously, results in smooth changes in population size with time
DN/dt =rN
Or Nt=N0e^rt
What are the limits on population growth?
- density dependent limits: food/prey, water, shelter, nest sites, disease, mates
- density independent limits: weather, climate
Logistic Population Growth
Exponential population growth with a limit
- carrying capacity K
- growth rate diminishes as limit is approached
- dN/dt=roN(1-N/K)
How to recognize density dependence?
- manipulate density of an organism
- observe the success of individuals as a function of the number of adults
Time Series
Number of individuals N at each time t
Population rate of change
Number of new added versus population size N
-dN/dt=Nt+1-Nt
Per Capital Rate of Change
Does population growth rate change with N?
-dN/dt/N=(Nt+1-Nt)/Nt
Depensation
Individual performance declines at low population size
Allee effect
Demographic Stochasticity
Random variation in sex ratio at birth, number of deaths, number reproducing
Environmental Stochasticity
Decline in population numbers due to environmental disasters or more minor events
Genetic Stochasticity
Loss of genetic variation due to small numbers in reproducing population
What are the three reasons why populations may fail to increase from low density?
- R<0, deterministic decline at all densities
- Depensation
- Below “minimum viable population” size
Depensation
Individual performance declines at low population size
Allee effect
Demographic Stochasticity
Random variation in sex ratio at birth, number of deaths, number reproducing
Environmental Stochasticity
Decline in population numbers due to environmental disasters or more minor events
Genetic Stochasticity
Loss of genetic variation due to small numbers in reproducing population
What are the three reasons why populations may fail to increase from low density?
- R<0, deterministic decline at all densities
- Depensation
- Below “minimum viable population” size
