Exam 2 Flashcards
Physical Limitations to Life
Temperature (Heat, Cold) Water Gas exchange Light Body size Metabolism (Energy acquisition, Energy use) Nutrient acquisition Waste elimination
Physical Ecology of the Organism
The physical environment can affect abundance and distribution of species
Organisms adapt to their environment
Temperature
Enzymes work best in a narrow temperature range
Freezing destroys cells
Heating de-natures proteins
Temperature affects water balance
Water balance affects temperature
Light levels affect temperature
Temperature affects metabolism
Organisms regulate their body temperatures
Several different strategies are used (slides 10-17, 20-21 lec 9)
Temperature
Cold-blooded/warm-blooded:
- animals are cool/warm to the touch
Temperature
Poikilotherm:
- body temperature varies
slide 24 lec 9
Temperature
Homeotherm:
- body temperature stays constant
Temperature
Endotherms:
- generate heat internally via metabolism
Temperature
Ectotherms:
- require an external heat source
Organisms gain and lose heat many ways
Conduction
Radiation
Convection
Evaporation
(Slide 28 lec 9)
Conduction:
- Two objects in direct contact
E.g. a lizard basking on a hot rock
Radiation
- Energy gained as light —> heat
- Energy lost as heat
Convection
- Heat transfer between 2 bodies through a liquid or gas layer
Evaporation
- Water requires much energy to become gas
- Water can remove excess heat from the body
- But water loss can lead to dehydration —> over-heating
Counter-Current Heat Exchange: Staying Warm
Animals in cold climates could radiate significant heat through limbs (a)
Run warm arterial blood next to colder venous blood to warm it up (b)
(Slide 29 lec 9)
Counter-Current Heat Exchange: Staying Cool
Evaporation through nose/mouth rete cools venous blood before it returns to heart
Run warm arterial blood past cooled venous blood
Rete cools blood before it reaches the rest of the body
(Slide 30 lec 9)
There is a relationship between metabolic rate and rate of acceleration of chemical reactions
This is the temperature coefficient, a.k.a. Q10
The Q10 shows…
The Q10 shows the effect of temperature on the organism’s function
For ectotherms, metabolism (O2 use) increases with temperature
As the organism warms up, it becomes more active (uses more oxygen)
Q10 =
= the rate of biological processes generally increases 2-4 times per each 10°C increase (in normal physiological range)
Organisms have the ability to acclimate to new environmental conditions
Acclimation takes time; sudden change can lead to death
Acclimation can allow the organism to tolerate higher/lower temperatures than it normally would
Organisms can adapt to cold
Fish have developed antifreeze proteins
Plants have multiple adaptations including antifreeze proteins, supercooling, ice crystal nucleating agents OUTSIDE of cells.
Reptiles and invertebrates can supercool (no ice crystals form) due to glycoproteins
Size and Shape of Organisms
Size of organisms affects aspect of their lives
Larger animals have relatively less surface area (to volume) than smaller animals
The smaller “organism” has relatively more surface area
The larger “organism” has relatively less surface area
(Slide 38-42)
Surface area is important for:
Gas exchange
Heat absorption
Heat loss
Water loss
Surface Area
Leaf size and shape affect:
Heat exchange
Transpiration
Photosynthesis
Photosynthesis
6 CO2 + 12 H20 –> C6H12O6 + 6 O2 + 6 H2O
2-part process:
Light reaction: sun needed directly to produce ATP and NADPH
Dark reaction: CO2 made into simple sugars (G3P, glucose, starch); can occur without sunlight
Stomata
Stomata let CO2 in
Can close to minimize water loss
Photosynthesis in C3 plants
Rubisco enzyme catalyzes reaction to form 3-PGA
Rubisco enzyme can cause O2 and RuBP to react, producing CO2
A competing reaction; reduces plant efficiency
(Slide 49 lec 9)
Photosynthesis in C4 plants
2-step process involving different leaf anatomy:
- PEP converts CO2 to malate, aspartate, in mesophyll cells
- Compounds converted to CO2 in bundle sheath cells, then normal C3 process
- PEP does not interact with O2 as RuBP does in C3 plants
(Slide 50 lec 9)
Photosynthesis in C4 plants
Pro vs Con
Higher rate of photosynthesis in C4 plants (than in C3 plants)
More carbon fixed per unit of “open stomata time” than in C3 plants
Greater water efficiency in arid environments
But C4 plants use more energy than C3 plants (due to production costs of making PEP)
Photosynthesis in CAM Plants
Similar to C4 plants, but carbon fixation and Calvin cycle occur in the same cells
Timing of reactions is different: stomata open at night (CO2 in, stored), close during day. CO2 is converted to sugars during the day.
Cacti and succulents
(Slide 52 lec 9)
Photosynthesis in CAM Plants
Pro vs Con
CAM pathway for CO2 fixation is less efficient, slower than C3 or C4
CAM conserves water by only opening stomata (water loss) at night
Body Size Affects Organismal Structure and Function
Larger organisms need stronger support structures to support their weight
Larger animals need thicker bones
Larger trees need thicker trunks
Size may be limited by factors other than bone strength
Heat is harder to remove in larger (volume) organisms
Size may be limited by factors other than bone strength
(Slide 56,57 lec 9)
Birds Have Very Efficient Lungs
First inhalation: Air enters mesobronchus
Enters caudal air sacs
First exhalation: Air is exhaled from air sacs through parabronchi
Second inhalation: pulls air through cranial air sacs
Second exhalation forces air from body
Water Transport in Plants
~95% of water loss in plants occurs through leaves
But large surface area is desirable to capture light
Leaves may have coatings to minimize water loss
But how to let CO2 in for photosynthesis?
- Special openings = stomata
- Allow CO2 in, water vapor out
Water Transport in Plants
Plants need ways to carry water from roots to leaves I:
Roots collect ions
Concentration gradient draws water into cells
Creates positive pressure in xylem tissue
Water Transport in Plants
Plants need ways to carry water from roots to leaves II:
Water is lost through leaf stomata via transpiration
Creates vacuum in xylem tissue
Pulls water up
Terrestrial Life Needs to Control Water Loss
Gas exchange requires contact between air and moist membranes
Potential water loss
How to keep from drying out?
How to Control Water Loss
- Reduce rate of water loss
- or- - Maintain more water in body
- or- - Tolerate water loss from body
How to Control Water Loss
1. Reduce rate of water loss
Evolve a better skin
Evolve adaptive behavior
- Become inactive during hot, dry periods
- Be active at night
- Seek moist conditions
- Hang out in burrows
How to Control Water Loss
2. Maintain more water in body
Excrete highly concentrated urine (lose less H2O)
Produce dry feces
Use metabolism to produce water from food
Drink lots and store it
Condense breath to maintain moisture
How to Control Water Loss
3. Tolerate water loss from body
Evolve dehydration tolerance
Get big: warm up more slowly; radiate heat at night
Water Balance in Fishes Saltwater fishes (hypoosmotic):
- High salt concentration in surrounding water
- Tendency toward dehydration (water lost via osmosis)
- Actively drink saltwater to re-hydrate; tendency to gain salt
- Concentrated urine expels salt, retains water
- Active removal of salt through gills (uses energy)
(Slide 70, 73 lec 9)
Water Balance in Fishes Freshwater fishes (hyperosmotic):
- Low salt concentration in surrounding water
- Water enters fish via osmosis
- Salt is lost by diffusion across gills
- Water removal: large amounts of dilute urine
- Active uptake of salts through gills (requires energy)
(Slide 71,72 lec 9)
Eliminating Wastes
Proteins and amino acids are digested and break down into nitrogen-containing molecules:
- Ammonia
- Urea (urine)
- Uric acid (highly concentrated nitrogen waste)
These compounds can build up and become toxic
Organism needs to remove them
(Slide 4 lec 11)
Organisms may evolve tolerances to high levels of nitrogen compounds
May occur by converting NH3 to less harmful substance
Eliminating Wastes
Ammonia
- Ammonia is the form usually used in fish, aquatic invertebrates
- Ammonia dissolves quickly in water
- Released through gills
- Ammonia can be detected by other organisms
- Sharks maintain high levels of urea in their blood
- Prevents water loss (to surrounding saltwater)
- Prevents need to drink (salt) water to maintain water balance
- Prevents need to use energy to remove salt from the body
Energy: Food Storage
Fat is good
More fat = better chance of surviving hard times
Organisms exposed to regular starvation events evolve the ability to survive starvation better
(Slide 12, 13 lec 11)
Energy: Metabolism
There are several pathways to break down glucose
Fermentation
Krebs/Citric Acid Cycle
All organisms lose energy:
- Heat
- Excreted waste products
Organisms need a certain baseline amount of energy just to live They need additional (net) energy to: -Grow -Reproduce -Support additional activity
Energy: Metabolism
Organisms need energy to:
Maintain
Move
Grow
Reproduce
Fermentation
= is anaerobic, not very efficient
1 molecule of glucose produces 2 molecules of ATP
Krebs/Citric Acid Cycle
= is aerobic, oxygen is necessary for process to occur
1 molecule of glucose produces 36 molecules of ATP
18 times more energy!
Energy: Metabolism
Metabolic rate
= total amount of energy used in a given time
Often measured by O2 used or CO2 produced in a given time
Metabolic rate increases with activity
Energy: Metabolism Respiratory Quotient (RQ)
Carbohydrate and lipid breakdown produces a fixed amount of energy per liter of O2 used
Respiratory Quotient (RQ) measures energy produced by carbohydrates and lipids
Energy: Metabolism
Basal/Standard metabolic rate =
The amount of energy an organism uses when at rest and not stressed
Energy is the Basis for Evolutionary Tradeoffs
Energy intake is limited
Adaptations that require energy will have to get it from the organism’s energy budget
Energy use in one area may preclude it in another
(Slide 24 lec 11)
Energy is the Basis for Evolutionary Tradeoffs
Why do northern birds lay more eggs than tropical birds?
Food is more abundant in north
More biodiversity in tropics = more competition in the tropics
More energy needed to compete, find food, avoid predators
Less energy available to produce eggs
(Slide 27 lec 11)
Animals and their Resources
Autotrophs
= organisms that make their own food
Plants (photosynthesis)
Animals and their Resources
Heterotrophs
= organisms that must consume other organisms for food
Animals
Heterotroph classifications
Predators (carnivores) Herbivores (grazers) Omnivores (a little of everything) Parasites Decomposers
Specialists
- focus on one or very few food types
Generalists
- eat a wide variety of food types
Life History
= the lifetime pattern of growth, development, and reproduction of an organism
Organisms don’t live in a world of unlimited resources; they have to make tradeoffs
Life History
Fitness
Fitness = product of organism’s viability x fertility
Fitness = survival x reproduction over a long, complex life
Life History Tradeoffs
Modes of reproduction Age at reproduction Timing/frequency of reproduction Resources allocated to reproduction Number of eggs/offspring/seeds Size of eggs/offspring/seeds
Life History
Adaptations of an organism that affect life table values of:
age-specific survival
fecundity (reproductive rate, age at maturity, reproductive risk)
fecundity
- (reproductive rate, age at maturity, reproductive risk)
- (number of offspring per reproductive episode)
Some Life History Traits
Maturity (age at first reproduction)
Survival to breeding age
Annual adult survival/mortality (average of population)
Clutch size
Clutches per year
Egg weight
Relative clutch mass (weight of all eggs)
Parity (number of reproductive episodes)
Fecundity (number of offspring per reproductive episode)
Mortality (end of life)
Parity
- (number of reproductive episodes)
Senescence
- (aging; deterioration with age)
= gradual deterioration that comes with age
Life History
Many types:
Bacteria reproduce once (fission); no juveniles/adults
Some insects are univoltine: one reproductive event per year, then death
Life History: Semelparity
One reproductive event, then death
Lots of offspring/seeds all at once, then parent dies
A “boom or bust” strategy
Ex. Brown Antechinus, Chinook Salmon
Life History: Iteroparity
Multiple reproductive events
A few offspring each season
A “quality over quantity” strategy
Tradeoffs
Why do semelparous animals die after reproducing?
Reproduction is very stressful, leads to death
But there is a tradeoff: greater offspring output
Resources are limited
How does the body use them?
Balance between growth, survival, reproduction
(Slide 16, 18, 20-23, 26 lec 12)
Reproduction is Costly!
Increased reproduction –> decreased survival
Decreased reproduction –> increased survival
Fitness requires reproduction
Reproduction can be costly for the individual
Reproduction can shorten lifespan
Reproductive costs limit evolution
Lack’s Hypothesis
Selection will favor the clutch size that produces the most surviving offspring
The number of surviving offspring should be maximized at an intermediate clutch size
(Slide 27, 29-31, 33, 34 lec 12)
Problems with Lack’s Hypothesis # 1
- Lack’s hypothesis assumes no tradeoff between reproductive effort in one year vs. survival/reproduction in future years
- If reproduction is costly, reduce current investment and hold back some reserves for next time
Problems with Lack’s Hypothesis # 2
- Lack’s hypothesis assumes only the effect of clutch size in determining offspring survival
- But being from a large clutch may have delayed maternal effects into future generations
- Clutch size affects offspring survival and offspring reproduction
Problems with Lack’s Hypothesis # 3
- Discrepancy between Lack’s predictions and observations may be due to lack of adequate controls
- Clutch size is highly plastic, not strongly genetic
- Birds appear to optimize their own clutches by conditions in any given year
Optimization of the trade-off between growth and reproduction:
(Slide 38-42 lec 12)
Optimal Compromise Between Size vs. Number of Offspring
Assumption #1: tradeoff between size vs. number of offspring
Assumption 2: Above a minimum size, larger offspring will survive better than smaller ones
Parental fitness from a single clutch = (# offspring in clutch) x (probability that an individual offspring will survive)
(Slide 43-48 lec 12)
Alternative Life History Strategies
Different strategies depending on:
- How variable is the environment
- How long does the organism live
- How many times does the organism get to reproduce over the course of a lifetime
r-strategies vs. K-strategies
Alternative Life History Strategies
r-strategists:
Short lives
Rapid development and reproduction early in life
Many offspring
Low survival of offspring (many born but most die)
Small body size
Minimal/no parental care
Live in unpredictable environments
Environmental resources usually not limiting (population is controlled by factors such as weather)
Alternative Life History Strategies
K-strategists:
Long lives
Slow growth
Multiple opportunities to reproduce
Relatively fewer offspring per reproductive episode
Larger offspring
Better survival of offspring
Parental care typical (animals); large seed size (plants)
Mortality affected strongly by population density
Population regulated by resource limitation
Aging
If population is shielded from disease and predation, aging can occur
Senescence = gradual deterioration that comes with age
Mortality increases with age
Fecundity declines with age
Why do organisms age and die?
Aging/Senescence = late-life decline in individual fertility and chance of survival
(Slide 56 lec 12)
Rate-of-Living Theory of Aging
Aging = accumulated damage to cells/tissues
Organisms have evolved to repair/resist damage and have reached biological limit of repair abilities
Aging rate should be correlated with metabolic rate
Species should not be able to evolve longer lifespans under selection (already maximally adapted)
Evolutionary Theory of Aging
Aging = failure of organisms to repair accumulated cell/tissue damage
Repairs are incomplete and caused by deleterious mutations or tradeoffs between repair and reproduction
Natural selection is weak late in life; late-acting mutations accumulate with age
Antagonistic Pleiotropy Theory of Aging
Mutations conferring fitness benefits early in life and fitness costs later in life can balance out and be advantageous
Individuals with these alleles experience early benefit without paying the late cost
Such an allele can increase fitness of carrier despite apparent low benefit and high cost
Is there an Evolutionary Explanation for Menopause?
Women’s fertility declines earlier and faster in women than in men
Why stop reproduction at ~50 if life continues for many years after (~80)?
- Menopause is a non-adaptive artifact due to recently lengthened lifespans
- Menopause is a life-history adaptation associated with fitness gains of grandmothers providing care to grandchildren (grandmother hypothesis)
(Slide 60 lec 12)
Populations
Population = a group of individuals that regularly share genes
Also can be a group of members of the same species that live in the same area
How abundant are organisms?
Abundance
: number of individuals in the population
How abundant are organisms?
Population density
= number of organisms in a given area
How abundant are organisms?
Crude density
= number of organisms in a given area not accounting for distribution differences
Not all organisms in a population are distributed evenly
Spatial Distribution of Individuals in a Population
Random:
An individual has an equal probability of occurring anywhere in the area
Due to neutral interactions between individuals and environment
(Slide 5, 6 lec 14)
Spatial Distribution of Individuals in a Population
Uniform:
Individuals are uniformly distributed throughout the environment
Due to local depletion of resources (nutrient/water limitation in plants) or antagonistic interactions among individuals (territoriality)
(Slide 6, 7 lec 14)
Spatial Distribution of Individuals in a Population
Clumped:
Individuals occur in groups
Due to patchy habitat (animals congregate around a patch of good food) or social groupings (animals are attracted to each other)
(Slide 6, 8 lec 14)
How abundant are organisms?
Ecological density
Ecological density: takes uneven distribution into account
Number of individuals per available living space, not just number per hectare
Hard to estimate
(Slide 10-15 lec 14)
Lincoln (Peterson) Index
N = total population (what you want to find out)
M = known number of marked animals
n = total animals captured in the second trapping
R = marked animals re-captured in the second trapping
Lincoln (Peterson) Index formula
N n
M = R
Re-arrange to get:
N = nM R
Total population = (total # captured after marking)(# marked)/# marked recaptures
Population size changes as a function of several factors:
Birth rate Death rate Fertility rate Age structure Sex ratio Immigration/Emigration
Populations
Age structure affects population growth
Important age classes (stages):
Pre-reproductive
Reproductive
Post-reproductive
Each age group = a cohort
Populations with higher % of younger cohorts will expand more rapidly
Sex Ratio
Sex ratios affect population growth
Primary sex ratio = ratio at conception
Secondary sex ratio = ratio at birth
These may be different!
Number of females in the population controls how quickly or slowly the population will grow
Populations can grow in several ways:
Linear growth—
Exponential growth—
Logistical (sigmoidal) growth—
(Slide 25 lec 14)
Linear growth—
the population increases steadily over time
Exponential growth—
the population grows at an exponential rate
Logistical (sigmoidal) growth—
population experiences exponential growth, then levels off
Calculating how a population will grow:
Nt = size of original population
λ = net reproductive rate (average number of kids per generation)
Nt+1 = population in the next generation
N= number t = time (which generation)
Calculating how a population will grow in the future:
Nt+1 = λ (Nt)
Future population size = (Net repro. rate) (Original pop. size)
Populations
λ
If λ >1.0, population will increase
If λ < 1.0, population will decrease
If λ = 1, population remains stable
(Slide 29 lec 13)
λ = net reproductive rate
λ = (# kids produced) x (probability that kids survive to adulthood)
Total # of kids produced = fertility
Populations
Exponential growth leads to:
Crowding, less shelter
Starvation
Increased disease risk
Increased predation risk
Large Numbers Attract Predators
Populations: Exponential Growth
Fewer offspring, lower survival
Smaller offspring, reduced adult survival, fertility
(Slide 34-41 lec 14)
Describing Exponential Growth
The exponential growth equation: Nt = N0e^rt
N0 = initial population size Nt = number of individuals after “t” time e = ~2.72 (natural logarithm base) r = instantaneous per capita growth rate (intrinsic rate of population growth)
In an exponential growth situation, the rate at which individuals are added to the population is:
dN = rN
dt
This is the derivative of the exponential equation,
Nt = N0e^rt
r = instantaneous per capita growth rate (intrinsic rate of population growth)
N = population size
dN varies according to population size
dt
dN = rN
dt
(rate of change in population size) =
(contribution of each individual) x
(number of individuals in the population)
r =
r = the individual (per capita) contribution to population growth
r = the difference between births and deaths (averaged over population as a whole)
r = (b-d)
Geometric Growth
Most populations don’t grow continuously
They are seasonal: increases and decreases depending on the season
Geometric growth = population change over discrete time intervals
Rate of geometric growth
Rate of geometric growth = λ = (population in current year) / (population in previous year)
λ = Nt+1/Nt
where t = time
The size of a population through a single time interval can be calculated by re-arranging equation to
Nt λ = Nt+1
To project the growth of the population at specific time
Nt λ = wNt+1
To project the growth of the population at specific time intervals:
N1 = N0 λ
N2 = N0 λ2
N3 = N0 λ3
To project the growth of the population over many time intervals, re-arrange to get:
Nt = N0 λ^ t
Geometric vs exponential growth
The equation for geometric growth,
Nt = N0 λ^ t
is the same equation as the one for exponential growth….
Nt = N0e^rt
….except that λ replaces e^r
The difference between geometric and exponential growth is that:
Geometric growth: you want to know the population at discrete time intervals
Exponential growth: you want to look at the overall trend
(Slide 53 lec 14)
Intrinsic Rate of Increase
- rm = intrinsic rate of increase (Malthusian parameter)
- Maximum possible growth rate under ideal conditions
- the exponential rate of increase of a population with a stable age distribution
- Most populations don’t have a stable age distribution!
- rm is more useful for identifying environmental conditions affecting population growth than as an accurate predictor of population growth
-rm = intrinsic rate of increase
= exponential rate of increase of a population with a stable age distribution
-Most populations don’t have a stable age distribution!
-R0 = net reproductive rate (fecundity x survival of newborns)
Survival and Fertility Decline in Crowded Populations
Survival:
Survival is reduced by: Limited food Increased waste Increased vulnerability to predators Increased stress Disease
Survival and Fertility Decline in Crowded Populations
Fertility:
Fertility is reduced by:
Limited food for adults
Increased behavioral interactions (fights, stress)
Smaller adults due to competition during adolescence
Limiting factor
= any environmental factor that limits the abundance or distribution of an organism
Perfect Conditions Rarely Exist Forever!
Some limiting factors: Space Food Disease Predation
Population Limits
Limiting factors affected by population size = DENSITY-DEPENDENT
As population grows exponentially, effects of crowding slow growth, and population ultimately stabilizes
(Slide 63, 64 lec 14)
This self-limiting process can be described using the logistic model
Logistic model is based on linear relationship between density and net reproductive rate
Population Limits
Logistic model
Uses the variables:
r = the intrinsic rate of increase
K = the carrying capacity of the environment
dN = rN (K-N) =
dt K
dN = rN (1-N)
dt K
(Slide 68, 70, 71 lec 14)
Density Regulated Populations May Show Chaotic Patterns
Fluctuations can occur
S-shape is not always smooth
Some causes:
Weather
Small population fluctuations due to changing conditions
(Slide 75-77 lec 14)
Density-Independent Factors Affecting Population Growth
Factors that are independent of population density: Temperature Rainfall Snowfall Fires Floods Droughts
(Slide 79 lec 14)
Life Tables
Life tables provide a schedule of age-specific mortality and survival
Start with a cohort of organisms (all individuals born at the same time)
Track individuals throughout their lives until death
Observe trends in mortality
Life table exponents
X = Age (in years) Nx = Number of individuals from original cohort alive at age “x”
nx = Number of individuals from original cohort alive at age “x” lx = Probability of surviving to age “x”
dx = Number of individuals that died during any time interval
qx= Age-specific mortality rate
bx = Ave. # of females born to females in each age group
lx bx = # females born in each group adjusted for mothers’ survivorship (R0 = sum of lx bx; = net reproductive rate)
(Slide 82-89 lec 14)
How to get lx
no/no
n1/no
n2/no
Etc…
(Slide 83 lec 14)
How to get qx
do/no
d1/n1
d2/n2
Etc…
(Slide 85 lec 14)
Survivorship Curves
3 idealized types:
High survival throughout life until heavy mortality at end (Type I)
Survival rates do not vary with age (Type II)
Extremely high mortality early in life (Type III)
(Slide 91-97 lec 14)
Survivorship Curves—Type I
Mortality is concentrated toward the end of life (older organisms)
Risk of dying is higher for older organisms
lx = proportion of cohort surviving to age class “x”
(Slide 93 lec 14)
Survivorship Curves—Type II
Mortality is relatively constant throughout life
Risk of dying is about the same at any age
(Slide 94 lec 14)
Survivorship Curves—Type III
High mortality levels early in life, but high chance of survival if you make it though childhood
Many offspring produced, most die in infancy
Common in nature
(Slide 95 lec 14)
Populations
Distribution of a species
Distribution of a species = where it can be found
Populations are small, geographically separate groups of the species
(Slide 4, 5 lec 14)
Dispersal and Migration
Dispersal:
- how individuals spread away from each other
The way individuals spread away from each other
Individuals often disperse when they mature
They can enter vacant habitat
They can enter a different population
Dispersal and Migration
Migration:
- Mass movement of large numbers of species from one place (population) to another
- Usually involves a “round-trip”
Individuals can migrate between populations:
Allows individuals to find:
new food sources
unoccupied territory
mates
Permits gene flow between the populations
Reduces potential for inbreeding
Reduces chances that populations will evolve on separate paths
Migrations occur more often between patches that are close together; less often between patches that are far apart
The more patches in the network, the higher the occupancy rate in the patches
Home range
= where an individual animal spends at least part of its time
Home Range Size is Related to Energy Requirements
Territory
= the area that an animal actively defends
Factors affecting home range size:
Diet
Body size
Food distribution
Home Range Size is Related to Energy Requirements
Carnivores need larger ranges than herbivores
Larger animals use more energy than smaller animals
Animals with greater energy needs (carnivores, large animals) require larger ranges
(Slide 13-19 lec 14)
Populations and Meta-Populations
Meta-population
= all of the smaller populations considered together; small populations linked by migration
Metapopulation Characteristics
- Spatially separate breeding populations
- Each individual sub-population could go extinct at any time
- Re-colonization is possible
- Local dynamics are different in the sub-populations (e.g. population size, growth rate)
(Slide 23, 24 lec 14)
Meta-populations
Sub-populations can be:
A SOURCE of new individuals: sub-population experiences net growth
A SINK (net drain) of individuals: sub-population cannot maintain its size without immigration from other populations
(Slide 23, 26-30 lec 14)
A SOURCE of new individuals:
sub-population experiences net growth
A SINK (net drain) of individuals:
sub-population cannot maintain its size without immigration from other populations
Importance of Metapopulation Dynamics in Conservation Biology
Larger populations are less likely to go extinct
More populations mean less likelihood of extinction
Migration means suitable habitat can be (re-) colonized
Preserving as many sub-populations as possible means preserving genetic diversity of species as a whole
(Slide 33-38 lec 14)
Allee Effect
As population declines, mates are harder to find
As mates are harder to find, reproduction decreases
As reproduction decreases, population continues to decline
Allee Effect
Especially problematic for species:
With large territories (might not encounter mates at lower densities)
Lekking species (MIs, prairie chickens)
Cooperative breeders (African wild dogs)
The Biosphere and the Physical Environment
The physical environment shapes both the ecology and evolution of organisms
Determines who can live where
Climate = Long-term average weather at a given location
Climate
= Long-term average weather at a given location
Shaped by global forces
Shaped by geography
Shaped by local forces
Shaped by organisms present
Shaped at a very fine scale: micro-climate
Does climate change?
Yes. Many climate changes have occurred over time
Slide 5 lec 15
Factors that Affect Climate
Distance from the equator Temperature (air and water) Rainfall Seasonality Prevailing wind patterns Ocean currents
(Slide 7 lec 15)
Seasons
Earth’s axis is tilted
Northern hemisphere gets more light during summer
Southern hemisphere gets more light during our winter (their summer)
(Slide 9, 10 lec 15)
Ocean Currents affect Climate
Water can hold a lot of heat
Water temperatures fluctuate less than land (air) temperatures
Ocean currents can warm or cool the surrounding air
Coriolis effect (earth’s rotation) Wind Ocean upwellings Prevailing major currents: - Antarctic current (gyre) - Gulf Stream current - Japan current
(Slide 13-27 lec 15)
Global Wind Patterns
Coriolis Force:
Effect on Global Wind Patterns
Prevailing Winds
(Slide 19-26 lec 15)
Hadley cells
Air circulation in Hadley cells produces persistent global climate patterns
(Slides 22, 23, 25 lec 15)
Greenhouse Effect
Some of the sun’s energy is reflected from the atmosphere and the earth’s surface
Some is absorbed by gasses in the atmosphere
These gasses trap light and radiate it towards Earth in the form of heat
(Slide 30, 31 lec 15)
Greenhouse Effect
Some gasses trap heat better than others:
CO2 = carbon dioxide CFC’s = chlorfluorocarbons CH4 = methane O3 = ozone NOx = nitrogen oxides
Local Climates
Many factors shape local climates: Ocean proximity Prevailing wind patterns Local topography (e.g. mountain ranges) Plants
(Slides 33, 35 lec 15)
The Biological Community Can Affect the Micro-Climate
(Slides 36-38 lec 16)
Factors that Affect Climate
Distance from the equator Temperature (air and water) Rainfall Seasonality Prevailing wind patterns Ocean currents
Biomes
Biome = general category of community type
Characterized by plant type and animal community
Organisms in the same biome (different location) share similar characteristics
(Slide 42 lec 15)
Biomes—Deserts
Low precipitation
<150-400 mm/yr.
Organisms adapted to dry conditions
Most found between 30N and 30S of equator
(Slide 33, 35 lec 15)
Biomes—Deserts
Plants:
Small/no leaves Thick branches May drop leaves during drought Minimize surface-area-to-volume ratio Stomata close during day
Biomes—Deserts
Animals:
Nocturnal
Estivation (reduced activity)
Ability to tolerate water loss
Metabolic water production
Countercurrent exchange to re-condense moisture in breath
Concentrated urine
Biomes—Forests Northern coniferous (pine):
Low rainfall
Cool temperatures
High humidity
Evergreen
Biomes—Forests
Temperate deciduous:
Warm summer/cool winter
Moderate precipitation
Trees drop their leaves
Biomes—Forests
Tropical rainforests:
Wet/dry season
Low soil nutrients
High decomposition rates of organic matter
High rainfall > 200 cm/yr.
Tropical/equatorial
Stable temperature
(Slide 54 lec 15)
Biomes—Temperate Grassland
Biomes—Tropical Grassland (Savannah)
Biomes—Chaparral
Look up!!!
Biomes—Oceans
Salt water: 86% NaCl Low nitrogen Low phosphorus Nutrients fall to ocean floor Little mixing between top and bottom layers 70% of Earth’s surface
Biomes—Tropical Oceans
Temperature differences between top and bottom layers
Thermocline: stratified temperature layers
Layers rarely mix
Oceans have low primary productivity
Biomes—Temperate Oceans
More mixing
More productive than tropical
(Slide 63 lec 13)
Biomes—Ocean Regions
Pelagic =
Surface
Biomes—Ocean Regions
Neritic =
regions over continental shelf
Biomes—Ocean Regions
Oceanic =
open ocean
Biomes—Ocean Regions
Benthic =
bottom
Biomes—Ocean Regions
Photic zone =
where light penetrates and photosynthesis takes place (~30 M)
Biomes—Freshwater Lakes and Ponds
Water temp changes more slowly than air: daily air temps don’t affect daily lake temps
Water = highest density at 4°C
Ice = floats on water
(Slide 79 lec 15)
Biomes—Freshwater Lakes and Ponds
Lakes are stratified:
Epilimnion = warm top layer
Hypolimnion = cold bottom layer
Thermocline = steep temp gradient
(Slide 74 lec 15)
Biomes—Freshwater Lakes and Ponds
Summer:
Top layer warm, highly oxygenated
Nutrients on bottom of lake
Decomposition at bottom of lake depletes O2 at bottom
No mixing of layers = summer stagnation
Biomes—Freshwater Lakes and Ponds
Fall:
Top layer cools and sinks Bottom layer is pushed up Layers mix = overturn -Nutrients circulate -Temperatures mix and lake water becomes same temp everywhere
Biomes—Freshwater Lakes and Ponds
Winter:
Top of lake freezes at 0°C
Bottom of lake is more dense at 4°C
Only top freezes, not the entire lake
Winter stagnation (no circulation)
Biomes—Freshwater Lakes and Ponds
Spring:
Lake top thaws Winds circulate warming top layer Pull up cold bottom layer Nutrients cycle Lake is mixed Spring overturn
Biomes—Freshwater Lakes and Ponds
Eutrophic
Eutrophic (high-nutrient) lakes: Higher primary productivity Higher biomass Lower species diversity Lower 02 levels at bottom Typically shallower Typically temperate
(slide 81 lec 15)
Biomes—Freshwater Lakes and Ponds
Oligotrophic
Oligotrophic (low-nutrient) lakes: Lower primary productivity Lower biomass Higher species (animal) diversity Higher 02 levels at bottom Typically deeper Typically tropical
(Slide 83 lec 15)
River Systems
(Slide 84 lec 15)
Estuaries
Areas where freshwater (rivers) and saltwater (oceans) mix
High productivity
Biomes—Ocean Regions
Pelagic = surface
Neritic = regions over continental shelf
Oceanic = open ocean
Benthic = bottom
Photic zone = where light penetrates and photosynthesis takes place (~30 M)
Phytoplankton can exist
Zooplankton can survive on phytoplankton
(slide 66 lec 15)
Intra-specific Competition
Individuals are competing with other members of the same species for food, space, resources, mates
Inter-specific Competition
Members of different species are competing for the same resources (space, food, water)
One species suffers due to the presence of another species.
Species may be excluded by other species (competitive exclusion).
Inter-specific Competition: Six types of exploitative or interference interactions:
- Consumption
- Preemption
- Overgrowth
- Chemical interaction
- Territorial interaction
- Encounter
- Consumption
- (one species monopolizes a shared food resource)
- Preemption
- (occupation by one species prohibits another from taking root or colonizing)
- Chemical interaction
- (inhibits or kills other species)
- Territorial interaction
- (behavior of one species excludes another)
- Encounter
- (non-territorial; e.g. scavengers)
Competitive Exclusion Principle
G.F. Gause 1934: If two species, with the same niche, coexist in the same ecosystem, then one will be excluded from the community due to intense competition.
If 2 competing species coexist in a stable environment, it is because of small differences in niche use
(Slide 9 lec 16)
Ecological Niche
All of the resource and habitat requirements of a species
The role the species plays in the environment
Describes space and diet requirements of a species
(Slide 11 lec 16)
Fundamental Niche
George Hutchinson
Niche as a quantifiable characteristic of a species
Range of axis variables = the limits required for a species to survive, reproduce
(Slide 12, 14 lec 16)
Fundamental Ecological Niche
The total conditions, tolerances, and requirements of an organism (considered in isolation from other species)
Where the organism lives, what resources it needs, and what role it plays in the system
Needs of the organisms represented in n-dimensional hyperspace
Realized Niche
Most organisms have to share their space
Conditions are not ideal
They live in the realized niche: combination of conditions and resources need to exist in the presence of other (competing) species
The part of the fundamental niche volume that does not overlap the fundamental niche of any other species
Reflects the influence of other species
No two co-occurring species may have exactly the same realized niche.
(Slide 16 lec 16)
Niche overlap causes competition
(Slide 17 lec 16)
Competitive Exclusion
(Slide 18, 30-33 lec 16)
Ex. Niche warbler birds
(Slide 19, 20 lec 16)
How many different competing species can be packed into an area?
(Slide 21, 22 lec 16)
How do species deal with negative effects of competition?
Leave and find a new area
Go extinct
Co-exist in smaller populations
Evolve to exploit a different niche: character displacement
Character displacement
(Slide 24-27 lec 16)
In Two-Species Lakes
Benthic:
Invertebrates found on lake bottom
Limnetic:
Invertebrates found on water surface
In Single-Species Lakes
Benthic:
1/2 Invertebrates found on lake bottom
1/2 Invertebrates found on water surface
Limnetic:
1/2 Invertebrates found on lake bottom
1/2 Invertebrates found on water surface
