BIOL 1040 Flashcards

What is the definition of ecology (2 parts)

1) study of the relationships between organisms themselves

2) and between organisms and their environment

define an individual:

a single living organism, fundamental unit of study in ecology

define a population:

a group of individuals of a single species, living together and interacting with each other

define a community:

a group of individuals of more than one species, living together and interacting with each other

define an ecosystem:

the complement of biotic (i.e, populations and communities) and abiotic (nutrients, water, substrates) factors that interact in a system

what is species richness?

the number of species in a community

what is biodiversity?

• more loosely defined concept, often employing a human-centric metric

What are the axis on a rarefaction curve?

• the x axis is the number of individuals collected (measurement of our effort)

• the y axis is the number of species collected

What does the rarefaction curve show?

distribution of species + their relative abundance

What is a useful trait of rarefaction curves having to do with sampling?

you can go back and “resample“ –– what if i only collected three fish, what would be the diversity? useful for comparing data sets

How do we know when do stop sampling (rarefaction curve)

when the curve plateaus

How can we use math to get a good estimate of richness in community?

• generate all possible rarefaction curves, use middle one, project where asymptote would be

• or if you can see the asymptote, good effort!

What are ways we can apply more effort?

• more time

• more efficiency

• more space

• greater diversity of methods

What is it important to do when comparing the diversity of different ecological communities?

control for effort!

How does diversity differ from species richness?

• species richness is not the only metric of diversiy

• consider: distribution of abundance / even-ness of a community (proportional makeup)

What is the Shannon-Wiener Diversity Index?

• H = the negative sum of, for each species, its proportion times the natural log of the proportion

• h = species richness rated by relative abundance

• penalizes numbers more the further they are from equal

What does a larger value on the Shannon-Wiener Diversity Index mean?

• more richness, more evenness

What is a rank abundance plot? How to read them?

• rank our species from most to least abundant

• plot rank vs log(abundance) (or log of relative abundance?)

• The length of the curve shows the richness

• the rate of decline of the curve depicts the even-ness

abundance vs relative abundance

• raw number vs proportion

why is scale a challenging problem in ecology?

• think of definition of comunity –> doesn’t give much insight of the scale

• things with natural boundaries is like ideal community to study

How does island size relate to species richness?

• larger islands –> more species

• power-law relationtionship:

  • S = cA^z

  • or Log S = Log C + Z * Log A

  • generally: doubling of the number of species for every 10-fold increase in island area

What is an assumption in the island bio-geography theory about how species richness can change?

• assume that species richness can only change via extinction or colonization (not, say, evolution)

In the island bio theory, what happens to the rate of colonization? to the rate of extinction? as a function of the number of species currently on the island? what does this lead to?

• immigration declines the more species are on the island

  • things arriving are repeats

• extinction increases the more species are on the island

  • more competition, but even just having more species, there is a higher likelihood for extinctions

• leads to equilibrium supported by feedbacks

why do larger islands have more species according to the island bio theory?

• larger islands should have a lower extinction rate

  • larger areas support larger populations–> lower chance of extinction

• should have larger arrival rates

  • they’re just bigger

how was the equilibrium theory of island biogeography studied experimentally?

• 1–> chopped up trees (reduced area)

• 2–> fumigated a tree (should go back to equilibrium)

What do we use the island bio theory for now?

null hypothesis

Where are species most found on the globe? what sort of complicates that?

• the tropics

• vastly greater sampling effort in europe/america vs the tropics

• not always the same: think seabirds

What are some hypotheses for the latitudinal species gradient

• 1 - species diversify faster in the tropics

  • relatively more stable slimate in the tropics supports a greater rate of speciation and lower rate of extinction (no dormant time)

  • relatively large lang area in the tropics supports a greater rate of speciation + lower rate of extinction

• 2 - species have diversified for longer in the tropics

  • relatively recent glaciation events near polls that reset species diversity

  • if rates are constant across the earth, this could result in more species in the tropics

• 3 - primary productivity is greater

  • tropical regions receive more solar energy per unit area than the temperate or polar regions, could lead to more resources

• 4 - mid-domain effect

  • if species range assigned at random, more of them will overlap in the center

estimations for total number of eukaryotes?

• 1 - extrapolate temperate species abundance to tropical species

  • estimate around 4-6 million

• 2 - extrapolate from detailed study of particular group (ex, beetles)

• 3 - using species characteristics

  • we’ve seen more of the big things, missing species are likely on the smaller end of the spectrum

• 4 - rarefaction

  • rarefaction with number of taxa

What are the four processes that regulate the abundance of a population

• birth, death, immigration, emigration

what is population ecology’s master equation:

delta N = B — D + I — E

N_t+1​=N_t​+B_t​−D_t​+I_t​−E_t​

Next population = Current population + births − deaths + immigrants − emigrants

per-capita version of master equation: N_t+1​=N_t​(1+b_t​−d_t​+i_t​−e_t​)

bt = Bt/Nt = per capita birth rate

explain the ring-necked pheasant example

• introduced to an island and studied for pop dynamics

• poor fliers, so remove immigration and emigration

what does the one in the per-capita formula represent?

• in a population where individuals carry over into next cycle, represents current population

pheasent model: N_t+1=lambda*N_t

• lambda = 1 + b + d

• lambda = per-generation factor of increase

• using two data points from a curve, can get estimate for lambda

how do species with non-overlapping generations change the lambda formula?

d = 1, so lambda = b

given a species with non-overlapping generations, what does b represent?

the number of new adult moths produced per parent in the last generation. not equal to the number of eggs

iterative vs general discrete geometric growth

• iterative: from one generation to the next

• from starting generation to many generations (plug in t)

• discrete: grows in leaps (seasonal synchronized birth times)

what is semelparity? when does death occur? why? what is produced

• one reproduction event per lifetime of an individual.

• death usually occurs very soon after reproduction

• because the parent invests all their resources into reproduction

• often have many, poorly provisioned progeny with low chance of survival

what is iteroparity?

• multiple reproductive events per lifetime of an individual. often coincident with some form of parental investment or extra provisioning that increase the survival of a smaller number of progeny

What is cole’s paradox:

mathmatically, semelparity seems like a better stratagy: only need to produce one more offspring to match the iteroparity

what environmental force is anti-semelparity?

• if an environment is unpredictable, it favors iteroparity

  • if condition for one big reproductive event not met, species dies

  • semelparity spreads risk

what is demographic stochasticity? where did we see an example? where are the effects most notable

• randomness in population change events

• example was green algae: see big discrete jumps (random) of growth

• effects most notable in small populations, becomes less notable as populations get larger

what is continuous-time exponential growth: N_t+1 = e^r * N_t

• population changes continuously through time

what is the intrinsic rate of increase?

• r = b - d

  • doesn’t have the one because it’s the rate of change of the population, not modeling the carryover

• diff from lambda because it’s used in an exponential

• diff threasholds than lambda

  • positive r = growth

  • negative r = decline

• little r is the log of lambda, the models overlap

where is synchronous reproduction common?

• seasonally driven systems: resources available when young emerge, + most resilient form during lowest resource time (like eggs)

where is asynchronous reproduction common?

• common in species with rapid generation times

  • need alternate strats for hard times

environmental sstochasticity

randomness from the weather

what was the goal of the song sparrow study?

• to figure out what keeps populations in check – exponential growth can’t happen forever, what stops it?

what did the song sparrow study find?

• the more breeding females, the less surviving young

• bc high abundance can lead to food shortages

what is density dependance?

• when demographic rates such as birth or death change with population density

what happens if birth rates decline as a function of density? what is carrying capacity?

get to an equilibrium point where birth and death are equal = carrying capacity

where do we get logistic growth?

• where the effect of density of lambda or r are linear

• where we draw straight lines for the class of denisty dependance

how do discrete growing populations act with logistic growth?

• they can approach smoothly if their growth is slow

• the can overshoot and cycle above and below their carrying capacity if their growth is fast, because density dependence is delayed by a generation

what is a reason we have negative density dependance?

• competition

• the effect of competition is manifest as negative density dependence

what is expolitative competition

individuals reduce the avaliability of resources like food water light or space

what is interference competition

individuals physically prevent access to resources or opportunities (territories, harems, nesting sites)

r vs k selection

• two different strategies species could pick from

• r: good at reproducing fast

• k: good at competing once we get to carrying capacity

how does r and k strats play out with competition colonization trade off

• moving into new wiped place (post-fumigation, say)

• r strats get there first, but get replaced by k strats

fast-slow continuum

• has replaced r - K strats

• species that do everything fast (but at cost of maybe not being as competative) → species that do everything slow (invest a lot etc, can last through lean times)

abiotic drivers

• the non-living environment, including climate, chemical nutrients, habitat, etc

• brings you the consept of niche

biotic drivers

• the impact that other species have on a pop

hutchinsonian niche

n-dimensional hypervolume: the set of all conditions where lambda is at the appropriate value for species growth. think graphically

what is a dispersal barrier?

a physical barrier that impedes species from moving

metapopulation or metacommunity

• a set of local populations (patches (islands of suitability)) coupled by the movement of individuals (immigration/emigration)

immigration emigration

movement through non-livable areas

what is the spacial insurance effect?

• if extinction rick is uncorrelated across the landscape

• one patch can get wiped out by volcano, but other patches are fine and can eventually re-colonize

what does having more patches provide? what is one caveat?

• more patches provide greater insurance

• BUT if more patches means smaller patches, any effect of insurance can be erased due to higher local extinction risk

what correlates to being endangered?

• both not a lot of habitat and very fragmented habitat

What is the backbone of food chains/food webs?

exploitative interactions, a pairwise interaction between two species where one benefits and one is hurt

How do we define exploiitation?

• by how the growth rate is effected

• ex: if more of a resource is added, then the growth rate of consumer goes up

• but if more of a consumer goes up, growth rate of resource goes down

what is a trophic level?

• number of average links between a species and the base of the food web (plus one so bottom is first level)

in a tri-trophic system, what does increasing the top consumer do for the bottom producer?

• top consumer munches on middle consumer, bottom producer allowed to grow more (rate increases)

the green world hypothesis

• three trophic levels: carnivores –> herbivores –> plants

• imagine a system that’s just herbivores –> plants

  • herbivore carrying capacity is regulated by the supply of food –> bottom-up regulation

  • plant carrying capacity is regulated by herbivory –> top-down regulation

• adding a top carnivore:

  • herbivores become top-down regulated

  • allows plants to be regulated by the availability of resources: bottom up regulation

explain the yellowstone wolf thing

• under green world hypothesis:

  • bc wolves are back plants are allowed to recover because there are less elk (are not bottom-up regulated )

• explotation (consumption) not the only think making it bottom up

• ex: grasshoppers moving to longer grasses for protection from predator, even if they like shorter ones better for food

  • just the risk of getting eaten releases that top down effect

describe the marine trophic chain

• four levels: predators (bottom up), forage fish (top down), zooplankton (bottom up), phytoplankton (top down)

• phytoplankton has top down pressure

what is the competitive exclusion principle

• two species competing for the same limited resource in the same habitat cannot coexist (indefinitely)

what happens if another resource is added

• then they can coexist, like market share

what is character displacement?

• differences among species characteristics are accentuated in regions where they overlap

what is niche partitioning?

• different species live in same area minimizing conflict

• allows for the coexisting of competing species even when there is some overlap

What are some different kinds of partitioning?

• character displacement

  • finches with beaks for small berries and others with beaks for big berries

• resource partitioning:

  • competing species partition their use of resources such that each species growth is limited by a different resource

  • ex: gut biome

• predator partitioning

  • competing species are impacted by different predators so that no one competitor can competitively exclude others

  • ex: sea stars and muscles

• temporal partitioning

  • competing species partition variation in the envionment through time. species need to have different sensitivities to the environment and be able to survive through unfavorable periods

    • ex: annual plants

  • spacial partitioning

    • cometing species partition fine scale variation in the spatial environment

    • ex: warblers in different parts of the tree

what is a keystone species:

• species essential for maintaining diversity of the community

the storage effect

• temporal partitioning

• ex of annual plants in a spot that all have different sensitivites for what a good year is –> when its a good year, they’ll bloom, else they will stay in their seed and wait

what is preemptive competition:

• a species utilizes a non-replenishing resource, like barnacles on rocks

Interference competition

• impeding a competitors access to a resource

• ex: california walnut putting toxins into the envionment to stop germination of competitors

what rule determines the outcome of competition:

for a pair of competing species to coexist, each must have a greater negative impact on the growth rate of its own population than on the growth rate of its competitor

why does higher species richness lead to more total biomass?

• niche complementarity:

  • with just one species, they are competing for the same resource

  • with multiple species, they can diversify and access different aspects of the resource pool

• selection effects:

  • more species means a greater chance of including those that are more productive

how does coral bleaching happen?

• usually, coral have algae living in or on them. this gives them their color. when temps increase, for whatever reason, they kick out the algae

what is mutualism?

a mutually beneficial interaction between a pair of species

what is symbiosis?

a pair or many species interact, at least one species experiences a benefit and none experience harm

what is resource-based mutualism

• an exchange of resources for the benefit of both species

what are lichens?

• a composite organism comprised of an algae living with one or many species of fungi

• the algae provide carbon to the organism while the fungi are generally involved in gathering water, nutrients, and providing structure and attachment

how do lichens reproduce?

the fungal and algal members of a lichen can reproduce independently, but lichens can ‘reproduce‘ asexually using sorefia - a complex of alga and fungal hypha that can disperse using wind to colonize new locations

nitrogen is the most abundant gas in our atmosphere. we also need a lot of it. how is it limiting?

• because there’s very few things that can get it into a usable form

• n2 is a triple bond, very intensive to break

what is nitrogen fixation?

• the process of converting atmospheric nitrogen into ammonia or other usable nitrogenous compounds

what are three ways that nitrogen can be fixed?

• lightning

  • lightning breaks the triple bond, so nitrogen makes other compounds

• the haber process

  • industrial nitrogen fixation for crops etc

• bacteria / archaea (+ some algae)

  • symbiotic and free-living bacteria fix nitrogen in soil and root nodules.

what is a nitrogen fixing plant

• legumes

• form root nodules that house rhizobia or other bacteria that fix nitrogen in exchange for nitrogen

what are ways that plants can fix nitrogen?

• root nodule symbiosis

• associative nitrogen fixers

  • promote bacteria around roots

• free-living nitrogen fixation

  • just like makes use of guys in the soil

what does plant-fungal mutualism support?

• promote water and nutrient absorption, disease resistance + more