Bio 1B Midterm 2

Ecology Midterm

Life history

suite of traits related to species’ life cycle and the timing of major events

Ecology

study of the relationship between organisms and their environment

principle of allocation

Individual organisms have a limited amount of resources to invest in different activities and

functions. Resources invested in one function are not available for another (a trade off)

type 1 survivorship curve

most individuals reach old age (e.g., humans)

type 2 survivorship curve

some individuals reach old age (e.g., squirrels)

type 3 survivorship curve

very few individuals reach old age (e.g., plants)

population

a group of organisms of the same species that live in the same geographic area at the same time and are capable of interbreeding

community

an interacting group of various species (plants, animals, bacteria, fungi) coexisting in a common location and time

ecosystem

a dynamic community of living organisms (biotic) interacting with each other and their non-living physical environment (abiotic) within a specific geographic area

biosphere

the global ecosystem encompassing all living organisms and their relationships; the “space of life”

demography

the study of how a population changes overtime

Nt+∆t = Nt + B + I – D – E

The BDIE model

closed population

a population experiencing NO immigration or emigration

𝑁𝑡 = 𝑁0 × 𝑒𝑟t

exponential growth model; N0 is initial number of individuals when time equals 0, and r is intrinsic growth rate of population (constant number)

what does population growth look like when r<0

exponential DECREASE

what does population growth model look like when r=0 (lines, graphically)

flat line

what does population growth model look like when r>0

exponential INCREASE

1/N dN/dt

Per capita (‘per individual’) population growth rate; rate of population growth rate divided by population size; a metric for the average rate of population change for an average individual in the population

density dependence

changes in per-capita population growth rate with population size

what does slope look like when density dependence is positive?

it goes up

what does density dependence look like when density dependence is negative?

it goes down

what does slope look like when there is no density dependence?

slope is zero; flat line

what is negative density dependence?

per-capita population growth rate decreases when the population is larger – a

necessary condition for a population to stop growing!

1/N dN/dt= r(1-N/K)

logistic growth model; factors in density dependence

K

carrying capacity; a constant number/parameter, NOT a variable; population size at which N reaches equilibrium

density independent factors

things like natural disasters that influence population size but have nothing to do with how large or small population is

3 definitions of a species interaction

1. an individual of species A influences the behavior or life events of species B

2. A population of species A influences the growth rate (dN/dt) of a population of species B

3. an individual of species A influences the growth, survival, or reproduction of an individual of species B

competition

occurs when two or more individuals share a resource, and consumption by one reduces its availability for others, causing reduced growth, survival or fecundity.

intraspecific competition

competition between individuals of the same species; mechanism behind density-dependent population growth

interspecific competition

competition between individuals of different species

prey strategies

defend physically (thorns), chemically, escape (learn when or how to hide), avoid by mimicry, and fight back

dishonest mimicry

appears like an unpalatable species, even though it is palatable

honest mimicry

appears like an unpalatable species and is unpalatable

true or false: herbivory always kills plants like how predation kills prey

false

true or false: plants can benefit from herbivory

true

facilitation

a broader term that can be used to describe mutualism AND commensalism; one species benefits another, and USUALLY both species benefit, but species can also experience neither a positive or negative effect

exploitation competition

two predators (A and B) eat the same prey species C; if A consumes C, better, then A indirectly harms B, because B gets less food

indirect mutualism

if three species (A,B,C) are herbivorized by the same species D, and both A and B are less palatable to D, so that C is a more attractive target for D, then A and B indirectly help each other (just an example, other ways this can manifest)

co-existence

when several species co-occur together over time

what causes a lack of coexistence?

is due to competition for same resource in the same location

fundamental niche

The full range of conditions or resources used in which a species could maintain a stable population in the absence of other species; niche limits are based on physiological tolerance limits and resource needs

Realized niche

The actual set of conditions or resources used in which the species could maintain a stable population in the presence of other co-occurring species; limits usually set by competition/predation or other negative interactions

niche partitioning

each species has the same fundamental niche, but a different realized niche (birds could hunt in the same parts of the tree, but limit themselves to certain sections of the tree); reduces competition

character displacement

reduces niche overlap; evolutionary response to drive reduction in competition

Lotka-Volterra predator-prey model

• When prey populations are low, predator populations become low (low food)

• When predator populations are low, prey populations become high (low predation)

• When prey populations are high, predator populations become high (high food)

• When predator populations are high, prey populations become low (high predation)

• Process repeats

what kind of density is required for populations to coexist?

negative density dependence

spatial refuge

enable coexistence by allowing prey to “bounce back” from rarity and increase their population size; a physical, structural, or geographical location that protects organisms from environmental stress or predators, allowing them to survive and maintain population stability (burrows, alcoves, etc.)

true or false: immigration can promote coexistence?

true

disturbance

a change in the biotic or abiotic conditions in a community; happening all the time, everywhere

primary succession

following a disturbance, the community becomes empty, or approximately empty; any species that enters the community must first immigrate from another community

secondary succession

following disturbance to an existing community, populations decline or only individuals of some life stages survive

early-successional species

initially arriving species during primary succession

late-successional species

more specialized organisms/species that arrive AFTER primary successional species “prepare” and colonize environment; primary successional species also prepare soil with nutrients

cycle (populations)

periodic increases and decreases in population size

abundance

number of individuals (either total, or per species)

richness

total number of species

evenness

relative similarity in abundance of species

composition

identities of which species are present

alpha diversity

number of species in a local site

beta diversity

difference between alpha and gamma diversity

gamma diversity

number of species across all sites

spatial grain

the character scale at which measurements are reported (a 1×1 meter rectangle)

spatial extent

the entire region which measurements are made (an entire state)

Latitudinal diversity gradient

pattern of changes in species richness (gamma diversity) with latitude; generally highest species richness near the equator, lower richness towards poles; observed to exist across taxonomic groups

The larger the area, the _____ the gamma diversity

greater

Island biogeography theory

“islands” closer to a mainland get more immigration of species than farther islands; larger “islands” have lower extinction rates

what determines equilibrium richness?

determined by the balance between immigration and extinction; therefore larger in larger islands, and when distance from the mainland is smaller

agroforestry

practices involving maintaining natural landscape fragments, intermixing species being cultivated, etc.

luxury effect

rich people have more access to biodiversity

dispersal

the movement of individuals or gametes away from (and potentially back to) their original location

methods of dispersal

water, mobile, wind, biotic vector (not ingested), biotic vector (ingested)

dispersal often _____ species distribution

limits

biotic factors

living components of the environment

abiotic factors

non-living components of the environment

_______ _______ set the extremes of a species niche

Abiotic limits

environment

EVERYTHING in an organism’s surroundings

which factor/limit controls realized niche?

biotic

biome

a region experiencing similar environmental conditions and therefore containing a similar “core” set of species; defined at different geographic scales by humans

what are the factors (facets of the environment) that control environmental gradients?

temperature, elevation, storm (hurricane risk), and predation risk

types of environmental gradients

continuous (linear, like temperature decreasing as you go up a mountain) and patchy (span across different environmental conditions)

what controls biome classification?

climate (temperature and precipitation specifically)

what happens to temperature at lower latitudes and why?

it increases because of more solar radiation

what happens to precipitation at mid-latitudes and why?

it decreases because of ‘Hadley cell’ air circulation patterns

what happens to temperature at higher elevation and why?

it decreases; rising air expands (lower density, lower pressure) and cools, while falling air compresses (higher density, higher pressure) and warms (Hadley Cell effect)

what happens to precipitation at high elevation and why?

it increases because we’re on the windward side of a mountain; as air cools, water vapor condenses and eventually falls as rainfall; descending air, and reduced moisture left in the atmosphere, result in “rain shadow” on leeward (dry) side of mountain

maritime climate

experienced in oceans because it acts as a buffer for climate; lower amplitude of seasonal temperature fluctuations

continental climate

higher amplitude of seasonal temperature fluctuations

Hadley cell effect

tropical air from the equator rises; moist air from tropics cools down as it rises; climates are the hottest at 30 degrees latitude because they receive dry air from Hadley cell effect, sucking out moisture that used to be present in air at these latitudes

Rain shadow effect

air flowing off the ocean or the windward side of a mountain is cool; as ocean air goes up mountain range, water vapor condenses and drops moisture in the form of rainfall or snow; less moisture enters leeward side, making it hotter

photosynthesis

solar energy from the sun is turned into carbon bonds that can be used by organisms

respiration process

metabolic reactions release chemical energy, and in doing so return carbon to the environment, and re-radiate thermal (heat) energy

what happens to all the energy that’s received from the sun?

it is eventually re-transferred away from the planet and towards outer space; organisms can use some of this energy before it’s returned to space

gross primary production (GPP)

all the energy obtained from sunlight by autotrophic (photosynthetic) organisms

net primary production (NPP)

all the energy available to other organisms (as biomass, for example) through autotrophs

respiration (R)

the energy used directly for metabolism

how can we solve for NPP?

GPP-R

what are plant’s main limits on productivity?

water availability, plants lose water (transpire) in exchange for gaining carbon in photosynthesis; extreme temperatures, photosynthetic enzymes are temperature sensitive

which ecosystems contribute the most carbon per NPP?

tropical rainforest and oceans (rainforest high individually, oceans collectively)

ecological efficiency

fraction of energy later available to other organisms as growth (efficiency= growth/ energy available, or amount consumer sees/total energy)

assimilation fraction

fraction of energy used by an organism for growth and respiration