Ecology Flashcards
What is ecology?
It is the interactions between organism, biotic and abiotic environment and humans
Biotic factors: Living
Abiotic factors: Nonliving
What is traditional ecological knowledge?
- its a western term used to summarize the understandings of nature and human relationships with nature, of different indigenous peoples
- These systems of knowledge have been excluded from western dialogs about ecology or have been lost, but that is now changing
What are Biomes?
- They are major terristrial ecosystems at a global scale
- they have different combinations of climates and species within a similar range
- Biomes are affected by climate (good predictor of biomes)
- temperature and precipitation
- Effects of elevation and latitude on biomes are similar
-The linkage between biomes and species isn’t perfect → Rough matches between biomes and species ranges
-Species distributions often overlap within biomes
-Geographical distributions (ranges) vary across species
How are biomes affected by climate?
Temperature: latitude dependent with some unique patches
Precipitation: Dry Vs. wet
What are some patterns of climate?
- Temperature increases at lower latitudes because they receive more solar radiation
- At the equator sunlight comes in from the sun making it warmer
- As we get closer to the poles the angle that the sunlight comes in is lower meaning the light hitting is spread over a larger area (Lower intensity= less heat)
What are some patterns of precipitation? (increase and decrease)
-Increases at high elevations on windward side of mountains
* Cool air flows from the ocean on the windward side of a mountain range
* As the air cools, water vapor condenses → precipitation
* Descending air and reduced moisture left in the atmosphere → Rain Shadow on the leeward side of a mountain
- DECREASES at mid latitude because of Hadley cell air circulation patterns
What is a rain shadow?
-Increases at high elevations on windward side of mountains
* Cool air flows from the ocean on the windward side of a mountain range
* As the air cools, water vapor condenses → precipitation
* Descending air and reduced moisture left in the atmosphere → Rain Shadow on the leeward side of a mountain
What are Hadley cells?
- Hadley Cells: High precipitation in the tropics
- Tropical air heats up → moisture rises and air cools
- Cooler air precipitates moisture as rain in tropics
- Rising air is displaced North or South → Creating winds and air transport
- Transported air begins to cool down and sink
- Dry air fall in mid latitudes
What are some characteristics/ pattern of temperate?
-Decreases at high elevations
* Every ~1000 m elevation increase causes a 5-10C temp. decrease (Lapse Time)
-Rising air expands (low density, lower pressure) and cools
-Falling air compresses (high density, high pressure) and warms
Why does the tilt of the earth cause seasons?
- The earth is not perfectly aligned at the equator with the sun
- During certain months different part of the earth have direct sunlight while others are further from the sun
How does the ocean affect the climate?
Oceans buffer climate, so climate extremes are stronger in the interior of continents
- Water warms and cools slowly
- Near the coast winters are milder and summers are cooler
Maritime climate
Lower amplitude of seasonal temperature fluctuations
Continetial climate
High amplitude of seasonal temperature fluctuations
Mediterranean climate
Characterized by hot, dry summers and cool, wet winters
What are indicator species?
-They are species that are tolerant to very specific/ healthy conditions
-They are used to make inferences on the conditions of the environment
* Presence of one or many bioindicators species at a site can tell us about environmental conditions
What are the types of abiotic and biotic gradients?How distribution limits be partially set by geographic distributions?
-Types of gradiants
* Temperature gradient
* Elevation gradient
* Storm risk gradient
* Predation risk gradient
- Some gradients are physically continuous, other gradients are patchy and span a range of environmental conditions
- Species occur where performance is highest along an environmental gradient
-Species distribution are often limited at one end of the range of abiotic environmental factors and at the other end by biotic factors
How can biotic factors influence abiotic limits?
EX: the food obtained through biotic interactions (predation) influences the temperature (abiotic) of the fish
Limited food= less growth Excess food= higher growth
When two species have similar distributions, can we be sure that the same factors limit both of their ranges?
No, because one species may not always be limited by another
EX: While the white bark tree is limited to a specific range due to the Clark’s Nutcracker, the bird’s range isn’t limited by the trees but by another factor
When two species have similar distributions, can we be sure that the same factors limit both of their ranges?
No, because one species may not always be limited by another
EX: While the white bark tree is limited to a specific range due to the Clark’s Nutcracker, the bird’s range isn’t limited by the trees but by another factor
What is a performance curve?
- A metric of organism performance
- They measure how fitness varies with the abiotic factors
What sets limits to a species’ distribution?
-Multiple factors combine to determine where species can be present or absent
- dispersion
- abiotic environment
- Biotic environment
- Humans can influence or shift the limits
- organism behavior
- They all occur simultaneously NOT in sequential
Key limits that influence species distribution - Is the biotic environment suitable for survival, growth and reproduction of the species?
- Biotic factors: Living components of the environment
- Species interactions
- pollination
- food
- predators
- successfully compete
-Biotic Limits - Herbivory → cattle herbivores eat plant species and reduce the plants’ geographical distribution
- Competition → Competition for similar resources, both species can NOT persist in areas that overlap as a result each species reduces its range to an area in which it can successfully persist
Key limits that influence species distribution - Is the abiotic environment suitable for survival, growth, and reproduction of the species?
- Abiotic factors: Non living components
* precipitation
* sunlight
* snowfall - Abiotic Limits
* Temperature: species have a physiological tolerance to specific temperature→EX: Ocean Temperature
* Climate: EX: Limits on land → drought tolerance
Key limits that influence species distribution - Can the species disperse to a locations?
-Dispersal: The movement of individuals or gametes away from (and potentially back to) their original location
-Dispersal occurs via several mechanisms
* Animal vector → ingestion/ excretion, exterior
* Mobility
* Wind
* Water
What is spacial scale?
- The area
- Spatial grain: The characteristic scale at which measurements are reported
- Spatial extent: The overall region in which measurements are made at the selected spacial grain
What are the different diversity metrics?
- abundance: Number of individuals (total or per species)
- richness: The total number of species (#)
- Evenness: Relative similarity in abundance of species
* are the number of each species even/ close in #s - Composition: Identites of which species of present (describes)
What is the difference between richness and evenness?
- richness: The total number of species (#)
- Evenness: Relative similarity in abundance of species
*are the number of each species / close in #s
What is the difference between richness and evenness?
- richness: The total number of species (#)
- Evenness: Relative similarity in abundance of species
*are the number of each species / close in #s
Abundance
Number of individuals (total or per species)
richness
The total number of species (#)
Evenness
Relative similarity in abundance of species
Composition
Identites of which species of present (describes)
What is the species area relationship?
- As the area increases the species richness also increases
- The rate a which the area increase vs. species increase is 3/4 → as you look more specific this pattern may not continue
What is the latitudinal diversity gradient?
- it’s a pattern of changes in species richness with latitude
- higher species richness near the equator, lower richness toward the north and south pole
Why do some places have more diversity in the same area than others?
High biodiversity in the tropics
Why does the LDG (latitude diversity gradient) occur?
- Environment are less stressful in the tropics → more species can survive (Warmer/Wetter)
- More energy available in the tropics → more ways to differentiate niches/support more species
- High temp. in tropics biochemically drive higher mutation rate → thus speciation rates
- More competition in the tropics drives more net speciation to get away from competition
- More time to evolve new species in the tropics → conditions are consistently stable (no ice sheets)
- Long time since disturbance = higher richness
- More land area supports more species in tropics → Species area relationship
Why does the LDG (latitude diversity gradient) occur?
- Environment are less stressful in the tropics → more species can survive (Warmer/Wetter)
- More energy available in the tropics → more ways to differentiate niches/support more species
- High temp. in tropics biochemically drive higher mutation rate → thus speciation rates
- More competition in the tropics drives more net speciation to get away from competition
- More time to evolve new species in the tropics → conditions are consistently stable (no ice sheets)
- Long time since disturbance = higher richness
- More land area supports more species in tropics → Species area relationship
What are some species patterns that are sub-global?
Species area relationship
* The rate is 3/4 as you increase the area
Island Biogeography theory
- Island- places that are isolated (oceanic islands, mountaintops surrounded by desert, forest patched surrounded by fields, etc.)
- As the area of the Island increase the richness also increase
* Larger islands have lower extinction rates → there’s more ways for species to survive - As the distance between the Island and mainland increase the richness decreases
* Islands closer to the mainland get more immigration of species than further islands - Equilibrium richness is determined by the balance between immigration and extinction → Island size and distance from mainland
What is a population?
- A group of individuals of a single species in a certain
- Individuals may interact with each other
What is a population?
- A group of individuals of a single species in a certain
- Individuals may interact with each other
If dispersal isn’t limiting where is the range limit set?
- It’s set where zero or negative population growth rates occur
Why does the demography of a population change over time?
- Births
- deaths
- Immigration
- Emigration
Why does the demography of a population change over time?
- Births
- deaths
- Immigration
- Emigration
What is the BIDE model and what does each variable mean?
N(t+1)= N(t)+ B - D- E
- N(t) is the number of individuals at time t
- B is the number of births in the next time interval
- I is the number immigrants in the next time interval
- D is the number of deaths in the next time interval
- E is the number of emigrants in the next time interval
→ The time intervals are usually one year for large plants and animals but it depends on the population being studied
What is the BIDE model and what does each variable mean?
N(t+1)= N(t)+ B - D- E
- N(t) is the number of individuals at time t
- B is the number of births in the next time interval
- I is the number immigrants in the next time interval
- D is the number of deaths in the next time interval
- E is the number of emigrants in the next time interval
→ The time intervals are usually one year for large plants and animals but it depends on the population being studied
What is the simplified B-D model and what assumptions need to be made?
N(t+1)= N(t) + B-D
- assume that no immigration/emigration → a closed population
- N(t) the size of a population in a given year
What is the exponential growth model?
- N(t)= N(0) (e^rt)
-N(t)-population size- N(0)- initial # of individuals @ t=0
- r- rate of population growth per unit time (# time^-1) (inverse time)
What is the difference between Geometric VS Exponential growth?
Geometric growth
* Discrete time (results in points on a curve graph graph)
* linear when the y-axis is log-scaled
* EX: A population of annual plants that reproduce once every winter
Exponential Growth
* Continuous time (results in a curved time)
* Can also be exponential decline
r >0 : Population growth
r =0 : Constant population
r <0 : Population decline
* linear when the y-axis is log-scaled
* EX: A population of bacteria that reproduce at any time
Why do both exponential and geometric growth NOT continue forever?
- The assumption that “each individual on average, has a rate of reproduction in the population equal to r regardless of the population size” breaks down
- growth slows down as the population size becomes bigger
- We need a more complex model to describe reality
Why can populations not increase forever at exponential rate?
Carrying capacity is exceeded
What is per capita population growth rate?
- Rate of population divided by population size
- A metric of the average rate of population change for an average individual in a population
What is density dependence? How does per capita population growth rate change with population size?
The change in the per capita growth rate may be influenced by population size
- NO density dependence: Slope is constant
- Exponential model
- per capita rate doesn’t change with population
- An individual has the same chance of reproducing or dying regardless of the population size
- Negative density dependence: Negative slope
- The per capita growth rate decreases as the population is bigger
- Positive density dependence
- The per capita growth rate increases as the population size increase
What are examples of density-independent vs. density-dependent factors influencing a population?
When does a population reach equilibrium?
- A population comes to equilibrium when the per capita growth rate equals 0
- If the population is neither growing or shrinking it is stabilized
- Birth rate has negative density dependence → as the population increase birth rates decrease
- Death rate as the population size increases also increase because of limited resources
- Birth rate=death rate → Per capita = 0
Why is negative density dependence more common?
Usually life becomes more challenging in denser population, reducing birth rates and increasing death rates
- Fewer resources per individual
- More competition among individuals
- fewer mates available
- more disease or parasites
- More predation risks (easier hunted when common)
In the logistic model, what does the plot of per-capita population growth rate vs. N look like, and how does it compare to the plot of population growth rate vs. N? Biologically, how do you interpret these graphs?
What is the logistic growth model?
- Adds negative density to the exponential model
- Exponential model multiplied by (1-N/K) which is a correction to make the model have a line that has a negative slope
What are the properties of the logistic model?
- when N=0 ,(is r) in small population, collapses to the exponential model
- when N=K , The per capital growth rate =0 so the population is at equilibrium
1) Per capita growth rate is higher when the population is small and is identical to the exponential model
2) Population comes to equilibrium when N=K (the carrying capacity)
What do r and k represent?
r is the intrinsic growth rate
- A constant number/ parameter, NOT a variable
- Describes how quickly a population size will increase starting at very low density
- “intrinsic” in relation to the species biology and the environmental context
K is the carrying capacity
- A constant number/ parameter NOT a variable
- The population size at which N comes to equilibrium
According to the logistic growth equation…
- the pre capita change in number of individuals per unit time is greater when N is close to zero (1/N* dN/dt= is bigger when N is close to zero)
- The population growth rate (dN/dt) is zero when N=K
- K is a fixed parameter
- r is a constant
According to the logistic growth equation…
- the pre capita change in number of individuals per unit time is greater when N is close to zero (1/N* dN/dt= is bigger when N is close to zero)
- The population growth rate (dN/dt) is zero when N=K
- K is a fixed parameter
- r is a constant
What is a density independent factor?
→ dN/dt at any instant is limited by something unrelated to the size of the population
- external environment aspects (cold winters, drought, storms, volcanic eruptions)
- Population display erratic growth patterns because density independent factors change over time
- Density independent factors can increase of decrease parameters like r and K over time (we often can NOT measure these effects directly)
What are some density independent factor that may affect K and r?
Affecting K
- Change in temperature
- Change in moisture availability
- Change in land area
Affecting r
- Change in temperature
- Change in moisture availability
- Change in allele frequencies
Are population fluctuations common? Why?
population fluctuations are common
- density independent factors that vary over time
- Variation in immigration and emigration
What is a population collapse and why does it occur?
- exponential growth (abundance of food in summer, growing population) → followed by very cold winter, deep snowpack (no lichen grazing possible) → high winter mortality, temporary collapse
- Common misconception- collapse always occurs of a population temporarily exceeds carrying capacity
- smaller fluctuations are more likely in this scenario
Does the logistic model accurately model a population collapse?
What is life history and how can it be linked to population growth?
life history: suite of traits related to species’ life cycle and the timing of major events
- Survival rates as juveniles
- avg lifespan
- age of first reproduction
- number and timing of reproductive episodes
- size and number of offspring in each episode
- duration and investment of parental care
→ Variable across species
Why can organisms usually not simultaneously maximize performance of different functions?
principle of allocation
- individual organisms have limited amount of resources to invest in different activities and functions.
- Resources invested in one function are not available for another → trade off
- In life cycles resources must be allocated among growth, survival and reproduction
→ Reproduction size-number tradeoffs
- species can have smaller or fewer bigger offspring
- Negative relationship → as the size of the offspring increase there is a decrease in the number of organisms produced
→ Cost of reproduction trade off
- More reproduction in one year means less reproduction the next year
What are examples of ‘slow’ life history traits, or organisms?
- Slow species
- Late reproductive age
- Long life spans
- Long maturation time
→ Only represents about 35% of the variation of life
What are examples of ‘fast’ life history traits, or organisms?
- Fast species
- early reproductive age
- Short life spans
- Short maturation time
What is a species interaction?
1) An individual of species A influences the behavior or life events of an individual of species B
2) An individual of species A influences the growth, survival or reproduction of an individual of species B
3) A population of species A influences the growth rate (dN/dt) of a population of species B
What are some pairwise interactions?
- Competition (asymmetric)
* A and B both try to acquire the same limited resources - Predation (asymmetric)
* A kills B - Herbivory (asymmetric)
* A eats B, may or may not kill B - Parasitism (asymmetric)
* A lives on/in B, may or may not kill B - Mutualism
* A and B help each other - Commensalism
* B helps A, no impact on B - Facilitation
* General term for mutualism or commensalism
