Bio 1B Ecology

Traditional ecological knowledge

Knowledge, practice, and belief concerning relationships of living beings to one another and to the physical environment

Climate

Long term prevailing weather conditions in given area, combination of both temperature and precipitation

Biome

Major life zones characterized by vegetation type, depends on climate

Seasonality

Determined by earth's tilt, in mid/high latitude tilted axis of rotation causes strong seasonal cycles

Temperature

Increase at low latitude because area receives more solar radiation

Microclimate

Smaller scale, fine/localized patterns in climatic conditions

Precipitation

The amount of rainfall received in an area, increases at high elevation and on windward side of mountains

Elevation

Distance from the sea level, as it increases precipitation increases and temperature decreases, from bottom to top vegetation and organisms change

Latitude

Distance north/south of equator, at mid latitude precipitation decreases

Maritime climate

Areas closer to the ocean are wetter than inland areas due to the heating/cooling air masses that pass over the land, and large bodies of water moderate the climate of the nearby land

Continental climate

higher amplitude of seasonal temperature fluctuations

Hadley cell

Decrease of precipitation at mid latitude, descending dry air absorbs moisture whereas ascending moist air releases moisture

Species distribution

Patchy at multiple scales, cause of distribution limits may be different at different scales and in different parts of range

Dispersal

Movement of individuals/gametes away from parent locations, done via several mechanisms such as animal vector, mobile, wind, water

Dispersal limitation

Area is inaccessible or there is insufficient time to disperse

Environment

Surroundings/conditions of an organism

Biotic limit

Ability to survive/reproduce limited by interactions with other species, predator and herbivory, presence/absence of pollinators, food resources, etc

Abiotic limits

Ability to survive limited by chemical and physical factors including temperature, performance curves

Environmental gradient

Blending of environment, elevation gradient, gradient of soil nutrients

Indicator species

Species used to indicate environmental conditions, bioindicators

Demography

study of vital statistics of a population and how they change over time

Birth

number of births in next time period (add)

Immigrants

number of immigrants in next time period (add)

Death

number of deaths in next time period (remove)

Emigrants

number of emigrants in next time period (remove)

BIDE Model

Nt+1 = Nt+ B + I - D - E

B-D Model

Nt+1 = Nt + B - D

the size of a population in a given year is the size in the previous year plus the number of new individuals born and minus the number of individuals that died

Geometric growth

Assume B-D is constant fraction of Nt

Nt+1 - Nt = ∆N/∆t = r∆ Nt

looks linear when logscaled (log on y axis)

Nt = (1+ r∆)t×N0 (log both to get mx+b)

Exponential growth

Time interval is infinitely small, change of population over time is fraction of population size, demography continuous

dN/dt = rN

N(t)=N0e^(rt)

no immigration/emigration, constant b/d and r, no various among individuals

r > 0 = growth

r = 0 = static

r < 0 = decrease

Geometric vs Exponential growth

Geometric is set of points, exponential is a curve

Reproduction: continuous (exp), discrete times (geo)

Time modeled as: continuous (exp), discrete (geo)

Predictions for N(t): N0 ert (exp), Nt = (1 + rdelta)t N0 (geo)

Example organisms: population of bacteria that reproduces any time (exp), population of annual plants that reproduces once every winter (geo)

Density dependence: none for both

N0

initial population

r

Change in population by percentage of original

Density independent population growth

Rate of growth of population limited by something unrelated to population size, ex cold winters, droughts, etc

population displays erratic growth patterns

Density dependent population growth

Changes in birth/death rates with density/size of population

In exponential growth birth/death rates constant regardless of population density

Life more challenging in denser populations

- less resources/individual

- more competition

- fewer available mates

- more disease/parasites

- more predation risk

Equilibirum populatin density

Density dependent birth rates and death rates are equal

Negative density dependence decreases population growth rates

Population growth rate decreases at larger population sizes/density

Logistic growth

Equation for negative density dependence

dN/dt = rN*(K-N)/K

r = intrinsic rate of increase, how quickly population will increase at starting density

K = carrying capacity

small N = like exponential growth

N = K, equilbrium/carrying capacity reached

N > K = negative growth

Carrying capacity

Max population size at which N stabilizes, variable due to environmental stress, resource availability, competition

r, K as model parameters

r = intrinsic rate of increase, how quickly population will increase at starting density (time -1)

K = carrying capacity (#)

Population collapse

Can occur when carrying capacity is exceeded

Life history

Suite of traits related to speices lifespan and timing/pattern of production

- survivorship curve and lfiespan

- age at first reproduction

- number/timing of reproductive episodes

- size and number of offspring each episode

- duration and time investment of reproductive care

Principle of allocation

Individuals have limited amount of resources to invest in different activities, allocated to growth, survival, and reproduction

r, K as life history types

r-selection selects for life history traits that maximize reproduction and ability for production to increase rapidly at low density

K-selection selects for life history traits that enhance individual fitness when population is fairly stable (long life span, late reproduction, few reproduction events, large body size, low mortality)

Community

Multiple species co-occurring at the same place at the same time (doesn't include abiotic, single type of organism usually, spatial intent clear)

Scarcity

No resource occurs in unlimited quantities, organisms have to divide them, competition arises leading to negative density dependence

Competition

Two individuals share a resource and consumption by one reduces availability for others, causing reduced growth, survival, or fecundity (-/-)

Exploitation competition

Consumption of shared resources, individuals/species don't actually physically encounter each other

Interference competition

Competition involving direct, physical interaction

Intraspecific competition

Competition between individuals within same species

Interspecific competition

Competition between individuals of different species

Coexistience

When species co-occur for extended period of time, species using different resources can coexist

Competitive exclusion

Species compete and one/more become exist, failure to coexist due to completion for same resources

Assume resource doesn't vary in time/space, and only one resource

If two species competing for same resource species that uses resource more efficiently will eliminate other locally, slight advantages build up over time

Niche

Where a species fits in

fundamental - full range of environmental conditions/resources, based on physiological tolerance limits and resource needs

realized - actual set, not full range

Realized can potentially be bigger than fundamental but not usually

Nice overlap

When species' niches overlap, and a lower niche overlap means more likely to coexist

Niche partitioning

Coexistence by reducing competition, but doesn't mean no competition

Character displacement

Realized niche shifting in order to reduce competition

Predation

One species eats the other and benefits, other gets eaten and dies (+/-)

Gause's experiments show that there is a cycle of predator/prey dynamics and prey population peaks before predator

Herbivory

Same as predation but - species can regrow (+/-)

Parasitism

One species lives on the other, and gets resources from other species and benefits, where as the other loses resources and suffers but does not necessarily die (+/-)

Mutualism

For partners, both help each other by dispersing seeds, pollinating flowers, defending against predators, etc (+/+)

Not always positive depending on environment

Facilitation

Benefit for the target, originator may benefit, be harmed, or nothing will happen (+,-,0/+)

Commensalism

Benefit for one species, nothing happens to the other (+/0)

Cycle

When the population goes back up and down depending on the density

Lag

Population cycling takes time and the change in the other is not always immediate

Batesian mimicry

Dishonest mimicry, harmless looks like harmful

Mullerian mimicry

Two/more harmful/unpalatable species resemble each other

Physical and chemical defense

Physical: fighting back, mimicry

Chemical: use toxins

Parasite

Organism that feeds on cell contents/tissues/fluids of host while in/on host, but usually does not kill host and usually much smaller than host

Pathogen

Organism/virus that causes disease, doesn't have to live in/on host

Hyperparasite

A parasite of a parasite

Metapopulation

A group of spatially distinct populations linked by immigration/emigration, diseases spread as metapopulations

Reserviors

Environmental - where pathogenic species live when not parasitizing a host

Biotic reservoir - where pathogenic species live when parasitizing

Zoonotic disease

One that has a non-human biotic reservoir but can jump to a human host

Dispersal mechanisms

Contact transmission

Direct movement from one host to another (sex, birth)

Indirect contact possible (doorknobs)

Vehicle transmission

Indirect movement from one host to another via aerosols, water, dust, etc

Also possibly via life stage in environmental reservoir

Vector transmission

Indirect movement from one host to another via another biological host species

SIR Model

Susceptible, Infectious, Recovered/dead

dI/dt = β SI - m*I

S*β/m = R0

R0 > 1

beta = transmission rate

m = recovery rate (time)

after long period of time in this model, everyone will have recovered

R0

Ratio of disease spreading or not spreading

Disturbance

Event that causes ecological system to change, can be natural/human and removes organisms, sudden change in environmental condition and resource availability

Succession

Slow orderly progression of changes in community composition, through time following disturbances and in absence of major environmental change

Primary - following creation/appearance of bare substrate devoid of life, no seedbank/dominant organisms

Secondary - following disturbance, some organisms survive

Climax community

Stable community composition that is long term outcome of succession, not favorable due to disturbances being needed

Gap phase regeneration

Secondary succession, community shifts after a change in environment and allows for different species to colonize

Early/late successional species

Early are adapted to high disturbance, small seeds, extended dormancy, rapid growth, early reproduction

Later are adapted to low disturbance, smaller seeds, no dormancy, slow growth and long lifespan, later reproduction

Early successional species excluded because of

Facilitation - Early species modify environment in ways that favor later arriving species

Tolerance - Early species have little influence on later arriving species (later arrivers are better competitors)

Inhibition - Early species inhibit establishment of later species but early species are short lived

Competition/colonization tradeoff

Good colonizers not always good competitors

Fire

Globally common disturbance, good as it allows for managing succession and resetting land for better agriculture

Oxygen / heat / fuel

Oxygen: high winds intensify fire, fires make own wind

Heat: natural ignitions from lighting, human fire ignitions, animals spreading like with dry wood

Fuel: plants are material consumed by fire

Swidden agriculture

Slash and burn, plant crops for 1-2 years, sit fallow for several years, burn to remove ground cover and recover nutrients, very sustainable if low planting rate

Species richness/evenness/composition

Richness: total number of speices

Evenness: relative similarity in abundance of species

Composition: which species are present

Spatial scale

Scalar grain: characteristic scale at which measurements are reported

Spatial extent: overall region in which measurements made at selected spatial grain

Species area relationship

The larger the area, the more species there are and more richness

Island biogeography theory

Mainland has pool of available species, and no evolution of species in model

Immigration events and extinction events

Larger islands get more immigration, farther islands receive less immigration, islands with more species present have lower immigration

Equilibrium richness

When immigration is equal to extinction, individual species may go extinct or immigrate but overall richness stays in balance

Luxury effect

positive relationship in organism diversity/activity in urban landscapes ????

Latitudinal diversity gradient

Environments less stressful in tropics, more energy available, higher temperature drives higher mutation and speciation, more competition drives more net speciation, more time to evolve new species in tropics, more land area supports more species

Photosynthesis

Solar energy captured by formation of carbon bonds, then stored in organism

Respiration

stored energy in carbon compounds released for use in metabolism, released carbon into environment

GPP/NPP

GPP - gross primary production, glucose produced during photosynthesis, never measured directly, estimated via NPP + R

NPP - net primary production, energy converted into biomass, GPP - R (respiration)

NPP ecosystems

low NPP in areas where cold, dry, low nutrients

hgih NPP in ares where warm, wet, high nutrients

Energy flow

flow of NPP from plant to herbivore to carnivore to secondary carnivore, all goes to detrivores too

Ecological efficeincy

fraction of energy available to later organisms as growth, e.g growth/total energy produced (average is 10%)

Assimilation fraction

fraction of energy used by organism for growth and respiration, e.g. (growth+respiration)/total energy

Energy pyramid

Energy flowing up and down, how much available at each level