Oct. 21
Natural Selection:

Remember overall: Ecological theater and evolutionary play
SO WHAT?? All living diversity (including US) stems from evolution, modern applications like pest or pathogen resistance
What is evolution? Many definitions like:
Change in genetic composition over time (generations) (micro)
The connection between living forms and ancestral form - gradual change in form over time (macro)
Other thoughts/thinkers influencing Darwin
Lyell and Uniformitarianism: present processes inform past changes - processes that are observed today are those that occurred in the past
Linnaeus and taxonomy (looking at similarities and differences)
**Fossil collections popular at this time
Hutton and gradual geological change
Malthus and geometric increase in population vs linear increase in food/resources - populations are ultimately limited by scarcity
Lamarck and “transmutation” ie physical changes in organisms over time
Cuvier saw extinctions in fossil record
**Wallace independently came up with evolution
**SO WHAT? Darwin’s not in vacuum and doesn’t get all the credit. What did he contribute? THE MECHANISM of NATURAL SELECTION and exhaustive research and evidence
What is Natural Selection?
There is variation within populations (just look at people!)
Some organisms with certain traits are more likely to survive than others and will go on to reproduce
These advantageous traits will be passed on to offspring (traits must be “heritable”)
It is the mechanism of evolutionary change! Problems? Humans included in this! And no overall goal or ideal form to such change
Types of Natural Selection:
Stabilizing— “goldilocks” idea, variation streamlines toward some intermediate preferred trait
EX birth weight of human babies (intermediate weight babies survive better), giraffes (fight with their necks, but have to reach down to drink water)
Disruptive—pressures force phenotypes in 2 directions away from each other, more academic (potential speciation)
EX finches in Galapagos; one species specializes in hard seeds while another specializes in softer seeds
Directional—change of overall population and preferred trait away from middle
EX horses: hoof from 3rd digit, molars **environment also became more savannas so eat more grass than leaves
EX peppered moth (light previously common, but darker common since industrialization because of darker background)
Where does genetic variation come from?
Mutation—ultimate source but REALLY slow, small changes; usually deleterious (harmful); not enough to drive evolution by itself
Migration—indivs from one population move to another, bringing their genes (considered to have small effect)
Sex—mix up genes; every offspring (gamete) unique!
Environmental variation
When characteristics favored given sp envt conditions
Total energy/resources limited—have to prioritize! Growth v reproduction
EX Douglas fir (rings and cones)
EX guppies in Trinidad (smaller when reproduce faster)
Hardy-Weinberg Equilibrium
Frequencies stay constant assuming random mating, big population, no migration, no selection and mutations happen both ways
Genetic drift
Small population, can have random event that affects overall genetic variation of population EX bottleneck EX cheetah
Artificial selection—humans select traits (agriculture, fishing etc)
What is it? How much organism can reproduce, how well it survives
Perfection doesn’t happen because no “perfect” set of traits (tradeoffs, envt, etc)
Helping related individuals to survive (so your genes go on) at some cost to self
rb-c>0 (where r is relatedness, b benefit and c cost); would have to be satisfied for organism to display altruism
EX ground squirrel and alarm call

POSSIBLE exam questions:
Why are insect populations like bees so cooperative and colonial? Why do they not compete with each other? Altruism!
Give an example of altruism.
How might genetic drift be detrimental to a population? Decreases genetic variation - population is more vulnerable to disease, environmental changes

2 Nov 2009
Competition and Mutualism
WHO CARES? Explains balance of nature; applicable to cases of invasive species
Community: set of (potentially) interacting species living in same space, bound together by influences on each other
Mutualism: Two-way interactions between species that are beneficial to both (+/+)
Facultative (take it or leave it, not necessary) and obligate (necessary to survival)
EX pollination (gamete transfer for plant, nectar for birds and bees) OBLIGATE, and concern to conservation (Europe fewer pollinators)**and hugely important to agriculture (with pollination and nitrogen fixation)
EX Boran and Honeyguide bird (foragers get to honey faster, bird eats wax) FAC
EX Ant and Acacia OBLIGATE (ant protects acacia by eating competitors and leaf litter (fire!), and acacia gives nectar and protein blobs to ants)
Commensalism: one species benefits and no effect on other (+/o)
EX cattle egrets (eat insects scared up by cows, no effect on cows)
EX anemone and clownfish
Competition: both species want same resource, but only one obtains it, reducing the capacity of the other species; both species negatively affected (-/-)
Intraspecific (within species) and Interspecific (with other species)
Niche: hypervolume of factors (habitat, food, etc) where species can live
Hutchinson said realized niche (where species actually found) < fundamental niche (where COULD be found)
Some are empty! Niches in a community not necessarily saturated
Competitive exclusion: one species per niche
EX bottle experiments with paramecium - one species always wins with given conditions
EX warblers in Maine (coexist by living in different parts of ecosystems)
Classic example of overlap from barnacles, could see which species arrived when (one species COULD survive in zone of other…but other couldn’t reciprocate!)
Rate of change of species:
dN1/dt=r1n1*(1- (N1+α12*N2)/K1)

IE rate of change of species 1 depends on competition coefficient
**possible exam question: when is the system at equilibrium? What happens if α=0, 1?
What happens when N2 -> 0? When N1 -> 0? GRAPHS! Which we’ll do at review session!
What happens when dN1/dt at equilibrium (=0):

**Take home points: to have Coexistence, inter<intra (effect on itself greater than effect on other species)

POSSIBLE exam questions:
With what other organisms do/might humans have mutualism? Pets, corn, cows (agriculture)

Nov 4, 2009
continued from Nov 1: Coexistence of Species: example of more sophisticated experiments where silicate and phosphate each limited a different species of diatom
Competition as driver of specialization EX beak size (want same resource, need way to ensure availability)

Consumer-Resource Interactions
WHO CARES??? These interactions everywhere! Think us, think predation, herbivory, parasitism! Also care about big rare predators and what’s up
Predator-Prey dynamics
Predators can numerically grow with pop’n of prey
EX famous lynx and hare (but don’t forget they can eat other species!) (also coupled periodicity-lag time between populations' recoveries)
AND can have functional growth where each individual eats more (but there’s a limit to how fast they can kill and may reach satiation)
3 categories of functional responses
Prey defenses
PLANTS: waxy cuticle, chemicals like nicotine, spines, pitcher plan!
ANIMALS: poison arrow frog (and others with warning colors) poisonous, mimicry (yellow jackets and mimicking beetles; monarch butterfly)
Batesian where model toxic so predator LEARNS, Mullerian where converge on same coloration, BOTH taste bad
“arms race” EX crabs (pincers) and snails/mollusks (robust shells)
Lotka-Volterra equation PREY
(or depends on population of predators)
(or depends on capture and conversion efficiency of predators)
When does population not change? When death=birth
Graph examples from class (we’ll draw them in review)
**Remember not an attractor in that equilibrium model (FLAW)
Maybe environmental variation keeps equilibrium: EX of mites on oranges; at first predator eats all prey and dies; then when became spatially complex both survived for a year!
Newfoundland example: caribou, lynx, and arctic and snowshoe hares (snowshoe introduced) More lynx eat snowshoe hare, but caribou and arctic knocked down (caribou calves eaten by lynx): prey couldn’t be controlled
“keystone” predator: critical species in controlling whole community and (controls species composition of the community)
EX starfish experiments (where starfish removed from tidal area, became monoculture of mussels; clams echinoderms algae all gone!) *keystone because consumed mussels, the better competitor

Nov 9, 2009
What controls populations? Have to experiment to find out!
Can have closed and open communities (closed, species drop out when specific conditions pull them out of population {conditions called ecotones-abrupt change in environmental conditions} open when population distributed independently of other factors)
EX species and soil types and gradient of composition
Trophic levels: different feeding “levels” (predator, prey, primary producer)
Food webs: complicated set of community interactions (mostly based on feeding)
EX complicated and comprehensive web from England
Can be focused on energy flow (interaction strength - connection quantified by flux of energy), and functional (shows influence on growth rates between populations)
Usually only see 4 trophic levels (remember 10% rule?) - Large predators are low in number for trophic inefficiency
Trophic Cascade: effects on other trophic levels from top-down and bottom-up
EX world is green; herbivores could eat everything but don’t because controlled by predators (top down)
**possible exam questions: what happens to primary consumers when predator population increased? - increase!
Energy in system can come from outside system (ie leaves, example of St. John’s wort and fish; salmon runs)
Disturbance: major event affecting community (EX fire, storm, flooding etc)
See succession after for recovery
Can see where are after recovery based on species present
EX periodic flooding; without floods caddis fly takes over not washed out, fish dies!
EX sand dunes on Lake Michigan in spring (sand->dune grass-> herby->small forest-> developed forest)
**time scales for forests SO LONG! “old growth” forests in MI only 100s years old
Some ecologists say there’s a “climax community” like the pinnacle of succession; others say more about early and late succession (many states goes between, ecosystems are dynamic)
EX Krakatoa

Nov.11, 2009
Lake Ecosystems
Lake origins
Glacial (Great Lakes, Lake District in England); ice left from glacial period, most common kind
Tectonic (Victoria and Baikal); usually super deep, rare
Profile graphs of photosynthesis, temperature
So special that ice floats! Otherwise nothing would live through winter! (water less dense between 1-4 degrees C)
Layers because of wind and mixing; inertia when temperature keeps layers from mixing (@ 4degrees most resistance)
Lakes stratify vertically (Potential question: which seasons? Most stratified summer, mixing in spring and fall); different places have different numbers of mixing periods (MI has 2, NC has 1, tropics 0)
Where’s the thermocline? Determined by depth of lake, latitude, wind
**with oceans salinity has effects as well
What limits productivity in lakes?
Light penetration (secchi disc)
Nutrients (N, P high in tissue compared to availability), some which are stores and some supplies (flux)
Leibig’s Law of Minimum: one factor matter most (is the limiting factor) in controlling population
Eutrophication—literally when water body increasing existing nutrients (but can come from people too, and go to the extreme! Called “cultural”)
Range of nutrient content from oligotrophic (nutrient-poor) to eutrophic (high nutrients)
Redfield Ratio 106:16:1 (C:N:P) within tissues
Human health, aesthetics, dead zones and blooms all affect US!
Remember anoxia and less O2 (remember cold water holds more dissolved 02)

Major Lecture Themes as mentioned in Review Session for Midterm 2:

Lecture 10/21-Evolution
What Darwin’s theory is, what natural selection means and full theory (how organisms change over time)
Types of selection
Direction stabilizing, disrupting
Mechanisms for maintaining genetic variation
Inclusive fitness and altruism

Lecture 10/26-Population growth
Simple equations of growth in an unlimited environment
Understanding r vs. lambda
Under what circumstances would a population grow?
When is it equilibrium?
Fact that populations have limits
Carrying capacity
How one documents population limits (% of juveniles increases when population decreases) – how would you know population is regulated? Any vital rates are inversely proportional to ___
[lambda graph downward slope]

Lecture 10/28-Population dynamics
Age structures (newborns, adults, etc all different)
Useful vital, age-specific rates → survivorship term (Lx), survival rate (Sx), birthrate Mx)
R0 = net reproductive rate of individual in her lifetime
Correct reproduction term by probability of being alive
Lambda = reproductive rate per year…so need to figure it out for a lifetime
Slide 12 – straightforward calculations we should know
No PVA but a simple Leslie Matrix (appropriate to leave something like “log27” in answer if asked)
Equally good patches, some occupied, some not – patch model
Source-sink model – patches not equal
Populations are spatially complex

Lecture 11/02-Species interactions
Mutualism, competition, predation
Mutualism – examples: facultative, obligate
Competitions-be familiar with equations and graphs
Resource utilization spectrum (hump-shaped curve of seed size or soil moisture)
Resource overlap alone may mean no competition or lot of competition
Example scenarios with birds where species co-occur and don’t

Lecture 11/04-Consumer resource interactions
Functional numerical responses
Prey defenses
Cycle – not desirable property of being neutral
How do predator/prey coexist in real world - habitat

Lecture 11/09-Community structures
How real are communities? Tightly connected? Unresolved argument…though too tightly connected notion is probably exaggerated
Food webs
Complexity of food webs
Energy flow, functional…??
Bottom up effects
Trophic cascade
Disturbance – fire, flood, hurricanes

Lecture 11/11-Lakes
Types of lakes
Lake productivity
Lakes drive eutrophication
How they form
How their stratification develops
Their productivity
Mixes in spring, stratifies in summer (no O in lower levels), mixes in fall, …
More trophic level
Predator avoidance

Lecture 11/16-River ecosystem
Stream order
Hierarchical nature
Channel equilibrium
Power of system to move water and sediments that determines water equilibrium
Changing slope by straightening or meandering…be able to make predictions
Flow pathways for water and water budget
Food web
DOM – not all food webs are driven by algae-like organisms
River continuum (putting everything together) – energy supply, different organisms, make predictions…what if you had forest become meadow?

Lecture 11/18-Global water
Water cycle and human use of water
Reading (Poff) – how much water people use
How much water nature needs

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