BI107 quiz 5

What is a community

different species together at the same time and place

What characterizes community structure?

Species composition and diversity (which species, how many species, abundance) - organized by trophic levels

food chain

links trophic levels from from primary producers to top carnivores and decomposers

What are the four types of consumers in a trophic level?

Primary, secondary, tertiary, and quaternary

Turnover in community composition?

spatial and temporal change in species composition within a community

Temporal change

change in community composition, ex: krakatan eruption → new plants adapt (complete turnover) → new community

Spatial changes

change in species or abiotic components based on geographic range - horizontal or vertical environmental gradients (ex: in ocean)

How communities change over time? (3)

1. colonization (new occupation by biological community) and dispersal (influx) and local extinction

2. after natural disturbance: succession

3. global change (natural or anthropogenic)

succession

A predictable sequence of change in community structure (ex: wildfire - new plants adapt and create new environment)

What is GPP

total amount of carbon fixed by primary producers

What is NPP?

energy (carbon-carbon bonds) contained in tissues of primary producers and available to other trophic levels

What is ecological efficiency?

The overall transfer of energy from one trophic level to the next

What generally happens to biomass as you move up trophic levels?

decreases in most terrestrial communities (10%)

What two factors contribute to low ecological efficiency?

Energy loss as heat during metabolism and not all biomass being ingested or digestible (excretion or death only for decomposers)

What is ecological niche?

physical and biological environment a species occupies, including its ecological role

understand community structure by species diversity which includes

richness (number of different species) and relative abundance (evenness)

Shannon diversity index

higher H value higher species diversity

What is a trophic cascade? (happen when trophic structure changes)

A series of direct and indirect effects on other trophic levels caused by actions of a top consumer

example of trophic cascade

wolves reintroduction in 1995 → decrease in elk → increase in willow and aspen → increase in beaver which affects stream hydrology

patterns of diversity (global and regional)

1. global: latitudinal gradients (tropics: stable climate, few extinctions, more speciation, more solar energy, high productivity, complex habitat)

2. regional: species-area relationship (area and distance between areas) and island biogeography)

What is island biogeography?

number of species (species richness) on an island as a equilibrium between colonization rates and local extinction rates (applicable to any ecological island)

colonization/ extinction is influenced by

distance from mainland/ island size

groups of individuals of the same species that interact with one another within a given area at a particular time

population

What four factors affect population size?

Births, immigration, deaths, and emigration

The number of births per individual per unit of time

per capita birth rate (b)

The number of deaths per individual per unit of time

per capita death rate (d)

How is the intrinsic rate of increase (r) calculated?

r = b - d (maximum rate of increase of a population per individual)

birth-death model (for___ system)

Nt = N + B - D (closed)

How can change in population size over time be expressed?

per capita births minus deaths multiplied by population size at time t

What is the impact of habitat complexity on species diversity and community function?

greater niche specialization and support more species (ex: birds at different height) → higher and more stable NPP

ants cut leaves for

cultivating fungus to feed offspring

Many communities will return to pre disturbed state, but not always! (retype)

Many communities will return to pre disturbed state, but not always

example of succession without natural disturbance

dung beetle (feed at different time)

Packrat nest

where we find fossil and know different environments at same place before

how we measured community function

amount of energy or matter that moves into and out of the community per unit of time

decrease in ecological efficiency leads to

limit the number of trophic levels

what is ecological island

isolated area

consider population

size and density (different scales for different animals)

population ecology

how populations interact with their environment and how population changes

a quantitative hypothesis about the components of a system and their interactions that can be used to predict the properties of the system (predict the changes)

computational model

growth rate represents

time interval

change in population size can be measured directly for

small populations (easy to track)

B

number of births in the time interval = bN

D

number of deaths in the time interval = dN

BIDE model (for ___ system)

N = N + B + I - D - E (open)

delta N/ delta T = rN (applicable to _____)

both

how to calculate growth

(delta N/ delta T = B - D = rN)

Life table

keep track of demographic events (include cohort, survivorship, abiotic factors, first breeding, fecundity)

group of individuals (N) born at the same time

cohort

proportion of individuals that survive from birth to age x

survivorship (total at age x/ initial)

proportion of birds that reproduced for the first time in a giving year

first breeding

average number of daughters that each female produces at a given age

fecundity

we can calculate from life table

life expectancy, generation time, average reproductive success, r

life table - quantitative life histories allow us to

1. analyze history patterns and predict future

2. understand how survival and reproductive rates vary with age

3. influence of abiotic factors

4. strategies for managing populations

life history patterns are diverse (retype)

life history patterns are diverse

what are needed for all functions within life

Materials and energy

resources can’t be used for two functions simultaneously

Principle of allocation

more resources → increase

fecundity, survivorship → r

Functions in normal resources

Maintenance (MUST BE FIRST), defense, growth, reproduction

increase with resource availability →

resources acquisition increase up to a point

functions in stressful resources

invest more resources to maintenance

density of seed increases →

seed harvested per second increases up to a point

tradeoff examples

1. size off offspring or number of offspring

2. Number of offspring or parental care (ex: frog, whale, elephant)

3. Reproduction or survival

4. Reproduction or growth

elephant offspring has low survival when

far from grandma with mom lower than 20 years old

A population cannot persist in an environment where

r < 0 (size will shrink to zero)

Populations are not isolated (retype)

Populations are not isolated

we can predict where populations are likely to be found

if we know how resource availability and physical conditions influence survivorship and fecundity

localized example (using humidity and temperature)

lesser grain borer and rice weevil (r = 0)

Know growth rates are negative or positive in particular environments tells us/ not tell us

why species may be absent or present/ why different population densities across environment where population growth rates aer all positive

Population growth is

multiplicative (exponential growth for species have great fertility)

why logistic instead of exponential growth (what limit r)

density dependent (effects increase in proportion to population density)

number of individuals of any particular species that can be support in an environment indefinitely 

carrying capacity (K) - where r = 0

when we have maximum value of r/ growth rate

population is small/ middle part

when density below K

r > 0

population density and r are

inversely related

carrying capacity varies globally/ fluctuate over time (retype)

carrying capacity varies globally/ fluctuate over time

agriculture and technology ______________ by increasing food production and improving health

increase K - agriculture/industrial revolution

what cause population growth rate decrease from 2.2% to 0.9%

demographic transition (b decrease faster than d)

human still have K (retype)

human still have K