Studied by 16 people
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Ecology
How organisms interact with their environment and with each other.
The distribution and abundance of species.
The structure and function of biodiversity.
Setting of evolution.
Adaptation through natural selection.
Lynn Margulius
Created the endosymbiotic theory for the origin of the mitochondria.
Population
All the individuals of a species in one place at one time. (Zebras in savannah)
Community
All the species living together in one place at one time. (Zebras, giraffes, and rhinos in savannah).
Ecosystem
All the species and non-living environment (entire savannah)
Factors that limit range of a species
Dispersal
Abiotic Conditions
Climate like temperature, salinity, pH
Availability of nutrients and resources.
Species Interactions
Competition
Predation
Mutualism (organisms working together)
These conditions create a gradient where different species perform best at certain portions of it.
Sixth Extinction
Mass extinction created by human activities.
32% of species are decreasing in range and population size.
Four steps of Invasion
Transport
Establishment
Spread
Impact
Why can invasion fail?
Could occur at any of the steps.
Environment does not allow for survival
Physical-chemical environment prevents reproduction and/or survival.
Predators
Function
Ability to increase survival rate. Ex. Ability to hear
Adaptation
Feature that is produced to do the function. Ex. ears
Maladaptive
Reduce fitness
Non-Adaptive
Serve no purpose. Also called neutral.
Natural Selection
Allows organisms to become better adapted t serve their purpose by eliminating less effective variants.
Does not remove negative traits as change takes time.
Most prominent in changing environments where new ecological challenges change the fitness of features.
Tradeoffs
When a feature has both advantages and disadvantages.
Reproduction-survival: Resources invested into offspring → cannot be used to maintain own body.
Size-number: Can produce more offspring but in smaller sizes → lower chance of survival
Evolutionary constraint
Tradeoffs that reduce adaptation range.
Principle of Allocation
Resources invested into one function cannot be invested into other functions.
Ecological Niche
The resources that are required for a species to survive and its physiological tolerances.
What climate, food, etc a species prefers.
Species have ranges of tolerance where their ability to survive varies (Can only survive in certain environments, can only grow in some, and can only reproduce in some).
Evelyn Hutchinson
Stated that a niche is an “n dimensional hypervolume” with the x and y axis being ecological factors that influence the survivability of a species.
Example: For the Macaw, one axis would be annual temperature and the other axis would be precipitation.
Why temperature and seasonality vary with latitude
Temperature varies with latitude.
Near the equator (lower latitudes), the sun is hitting the earth’s surface at a 90 degree angle → solar energy is spread over a small surface area → high photon concentration → warmer temperature.
Further from the equator (higher latitudes), the sun is hitting the earth’s surface at a lower angle → solar energy is spread over a higher surface area → lower photon concentration → colder temperature.
During winter, earth is tilted away from the sun → solar energy is being spread over a high surface area → lower photon concentration → cold.
During summer, earth is tilted towards the sun → solar energy spread over low surface area → high photon concentration → warm.
How does solar light heat up the earth?
Light hits dark solid surfaces or water → photons are absorbed → reradiated as infrared wavelengths → radiation is absorbed by atmosphere.
Means that solar energy heats the air near earth’s surface (bottom of atmosphere) and not the air closest to the sun.
Strongest near equator as there are more photons.
Hadley Cell
High concentration of photons heats up the surface of the earth at the equator the most → absorbed photons are reradiated as infrared radiation which heats up the near-surface atmosphere → air becomes less dense → begins to rise above solar equator → bumps against top of atmosphere → pushed 30 degrees north and south towards poles.
As this hot air rises, it begins to expand as there is less atmosphere compressing it from above → cools by 5-10 celcius/km (Adiabatic Lapse Rate) → begins to sink and water vapour is released as rain → loses all moisture → becomes dry and warm as it falls at 30 degrees north and south.
As air rises from the equator, a partial vacuum is created underneath it → pulls hot air at 30 degrees north and south back towards the equator → a cycle is created.
Intertropical Convergence Zone (ITCZ)
Zone of rising, heated air.
Shifts with seasons, creating rainy and dry seasons in the tropics.
Ferrell Cells
The dry and warmed air that is sinking at 30 N and 30 S is either sucked back towards the equator by partial vacuum or continues towards the poles.
Dry air moves across earth’s surface towards poles → picks up moisture → begins to rise → snowy and rainy low pressure zones are created around 60 N and 60 S.
Rising air reaches upper atmosphere → shoved towards north and south by flow underneath → closes ferrell loop.
Ferrell cells move air away from the equator, creating westerlies (winds that move away from the equator from the west to the east).
Polar cells are the weakest cells and move air towards the equator → create easterlies (wind moving towards the equator from the east to the west).
Prevailing Winds
Created through the combination of cells and coriolis effect.
Ferrel cells move air away from the equator, creating winds that travel from the west to the east called Westerlies.
Polar cells move air towards the equator, creating winds that move from the east to the west, called Easterlies.
Areas with more land mass have less intense winds (north) and areas with less land mass have more intense winds (south/roaring 40s).
At the equator, there is very little wind as air moves straight up or down rather than north or south. It is called the doldrums.
Coriolis Effect
Earth rotates on its axis. The further you are from the equator, the slower the earth rotates because diameter shrinks.
Wind moves east away from equator (westerlies, roaring forties)
Wind moves west towards the equator (easterlies, trade winds)
Trends of Terrestrial Vegetation
Vegetation growth increases with moisture and temperature.
Biomes are created when regions have certain combinations of moisture and temperature, leading to the growth of specific vegetation.
Maritime vs Continental Climates
Maritime climates are more moderate as land changes temperature much more easily than bodies of water, making continental climates more extreme.
Orographic Precipitation
Air that is moist with condensation is pushed up mountainsides by westerlies → as it rises, it begins to lose moisture through precipitation as it expands due to cooling → creates a vegetated mountainside.
On the other side of the mountain, the now dry air is pushed down → begins to warm up as it is no longer filled with moisture → creates dry side of mountain, or a rain shadow.
Physiological Ecology
Organisms are complex chemical reactions.
Some chemical reactions direct development of zygotes
Some chemical reactions carry out metabolic processes.
Reactions occur best at optimal temperature and osmotic conditions.
Organisms can be viewed as a library of information.
Contain genetic instructions in DNA.
Similarities and differences between organisms is visible in DNA.
Temperature Tolerance
Seasonal temperature variation is low near the equator and increases with latitude → temperate animals can withstand colder temperatures than tropical animals.
All types of organisms are limited by extreme heat and cold.
Cold temperature → molecules move slowly → low reaction rate
Hot temperature → enzymes denature → low reaction rate.
Homeostasis
Poikilotherms regulate their temperature behaviourally as they lack the means to do so physically.
Snakes go in the sun for heat.
Homeotherms regulate their temperature through physiological traits.
Heat can be lost through
radiation
conduction
convection
evaporation
redistribution
Surface Area to Volume Ratio
With a smaller ratio, there is a high amount of surface area that can shed heat to the environment, making small animals better suited for warm climates.
With a higher ratio, there is less surface area that is able to readily lose heat to the environment, making larger animals more suited for cold climates.
Bergmann’s Rule (Size)
Homeotherms tend to be larger at higher latitudes.
Colder environment → larger body → lower SA/V → less heat loss.
Hot environment → small body → high SA/V → quick heat loss.
Allen’s Rule (Shape)
Homeotherms have smaller appendages at higher and colder latitudes.
Warm climate → thinner and but larger/longer body parts → high SA/V → more heat loss
Cold climate → rounded and small body parts → low SA/V → less heat loss.
Insulation
Achieved with layers of body fat or fur/feathers
Fur and feathers have dead-air spaces where convective flow cannot occur → temperature gradient → cold near outside of fur but warm next to skin.
Big investment for animals cuz resources and energy need to be spent.
Countercurrent Circulation
Arteries send warm blood to body parts that are a liability to heat loss.
Veins bring cold blood from liabilities to the body.
Heat exchange occurs between the arteries and veins → cold blood in veins gains heat while hot blood in arteries loses heat → temperature gradient is created.
Evaporative Cooling
Wet surfaces are exposed to air flow → water evaporates due to high heat of evaporation → cooled off
Behavioural Thermoregulation
Spending hot parts of the day in shade to stay cool, etc.
Behaviour that can help either cool or warm body temperature.
Environmental Factors on Distribution
Abiotic Factors: non-living and physiochemical components.
Conditions: Physical states that will not be used up (temperature)
Resources: Physical necessities that are used up (water)
Biotic Factors: Actions of other organisms
High predator population
Limiting Factors: Affects whether a species can or cannot survive.
Temperature and water (the big two)
Photosynthesis
Plants use light energy (photons) to take in carbon dioxide (through stomata) and water to create oxygen and glucose.
To grow, more carbon must be taken in than is lost in cellular respiration → carbon balance is key (net primary productivity = C gained - C lost).
Even though carbon dioxide is taken in through stomata, water is also lost through stomata.
Photons for photosynthesis are gained when plants put a large surface area into the sun → overheat and lots of water is lost → enzymes denature → plant loses function.
To prevent overheating, plants use:
C4 Pathways: Carboxylase (enzyme) first accepts carbon dioxide, reducing photorespiration.
CAM Pathways: Plants close stomata during the day and open at night to accept carbon dioxide → store carbon dioxide as malate until day → prevent water loss
Leaf Size
Dry environments have tiny leaves while wet environments have large leaves.
Leaf size is driven by precipitation.
Small leaves = preservation of water.
Large Leaves = use evaporative cooling.
Laminar vs Turbulent Flow
On a leaf with no obstacles (smooth surface), dead air builds up (unmoving air) in a pattern called laminar flow.
Laminae are layers of air that move at different speeds
Wind moving at 5 km/h 1 cm from the surface of the leaf but a you get closer, the speed slows down because of friction.
If there are obstacles on the leaf’s surface, laminar flow turns into turbulent flow
More turbulence = more cooling
λ
population Growth rate
Finite Rate of Increase
λ = (Nt+1)/Nt
Nt+1= λNt
Geometric Population Growth
Nt=N0λᵗ
Used when resources are unlimited
Intrinsic Growth Rate
r = lnλ
Used in particular environment with unlimited resources
Exponential Population Growth
Nt=N0eʳᵗ
When resources are abundant and conditions do not restrict population growth
Change in Population
dN/dt=rN
Doubling time
td=0.693/r
Density-Dependent factors
Factors that affect the environment but change based on initial population.
Greater effect on bigger population.
Disease
Density-Independent factors
Effect population, regardless of size.
Weather
Intraspecific competition
Individuals in a population competing with eachother for resources.
Logistic Growth
dN/dt = rN(1-(N/k)
used when there are limited resources and intraspecific competition.
k
carrying capacity
Environmental Stochasticity
randomness in environmental change
Demographic Stochasticity
chance sequence of births or deaths
Allee Effect
Negative effects of low density.
Arise from social factors like mating
Life History
Start life at a small size
Have a growth period before they can start to reproduce
Spend resources on reproduction
Life Tables
Summarizes life events that are expected at a certain age.
Age of death
Age of reproduction
Usually consider only females as they are the ones who limit population.
Survivorship Schedule
Risks of mortality that are specific to age
lx = probability that individual is still alive at age x
l0 = 1 because babies are born
Can range from 0 to 1 because it is a probability.
Type 1 = convex curve (low early death) humans
Type 2 = straight line (constant mortality)
Type 3 = concave curve (high early death)
Fecundity Schedules
Expected amount of reproductions
bx or mx = average number of daughters produced in x year of life.
b0 = 0 as newborns go through resource collection period before reproduction.
Net reproductive rate = daughters a female has in her life time = R0
Reproduction tradeoffs
Size-number: can have many small or few big
Early vs late reproduction: early dominates pop with less offspring
Cost of reproduction: survival of parents reduced as more resources go into offspring
Semelparity
Reproduces only once in life
called monocarpic in plants.
Annual
live one season
Biennial
Grow vegetation for one year then flower and die
Iteoparity
Numerous offspring before death
Perennials in plants
Big Bang Reproduction
When plants wait a long time to reproduce then have many offspring but die soon after
R Strategists
Fast growth
Short generations
Small body
high fecundity
poor competitors
good dispersal
produce more offspring
K strategists
oppostie of r strategist
Synchrony
Seed production synchronized → years of high seed production and years of no seed production → predators are satiated → all seeds will not be killed → balance.
Interspecific Competition
Competition among members of different species.
Interference competition
Direct interactions
Example: Fighting over territory
Exploitative Competition
Depletion of a resource
Note
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