(ESS) Topic 2: Ecosystems and Ecology

- Species and populations - Communities and ecosystems - Flows of energy and matter - Biomes, zonation and succession - Investigation ecosystems

species

a group of organisms that share common characteristics and that interbreed to produce fertile offspring

biosphere

the part of the planet where organisms live, including the ground and the air

ecology

study of living organisms in relationship to their environment

habitat

the environment in which a species normally lives

niche

the particular set of abiotic and biotic conditions and resources to which an organism or population responds

fundamental niche

 the full range of conditions and resources in which a species could survive and reproduce

realized niche

the actual conditions and resources in which a species exists due to biotic interactions

abiotic factors

the non-living, physical factors that influence the organisms and ecosystems

(temperature, sunlight, pH, salinity, and precipitation)

biotic factors

living components of an ecosystem

the interactions between organisms

predation, herbivory, parasitism, mutualism, disease, and competition

population

a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding

S and J curves

a generalized response of populations to a particular set of conditions (abiotic and biotic factors)

S curve

(ex.: mammals)

J curve

exponential growth (ex.: colonizing populations - roaches)

carrying capacity (K)

the maximum number of specific organisms a habitat can sustain

limiting factors

slow population growth as it approaches the carrying capacity of the system

(water availability)

community

a group of populations living and interacting with each other in a common habitat

ecosystem

a community and the physical environment with which it interacts

food web

a complex series of interactions showing the feeding relationships between organisms in an ecosystem

respiration

the conversion of organic matter into carbon dioxide and water in all living organisms, releasing energy

glucose + oxygen → carbon dioxide + water

aerobic respiration word equation

photosynthesis

produces the raw material for producing biomass

carbon dioxide + water → glucose + oxygen

photosynthesis word equation

primary producers

• produce their own food using photosynthesis

• form the first trophic level in a food chain

(autotrophs)

→ typically plants or algae

trophic level

the position that an organism occupies in a food chain, or the position of a group of organisms in a community that occupy the same position in food chains

feeding relationships

• producers

• consumers

• decomposers

• modelled using:

  • food chains

  • food webs

  • ecological pyramids

ecological pyramids

quantitative models (usually measured for a given area and time)

• pyramids of numbers

• pyramids of biomass

• pyramids of productivity

bioaccumulation

the build-up of persistent or non-biodegradable pollutants within an organism or trophic level because they cannot be broken down

biomagnification

the increase in concentration of persistent or nonbiodegradable pollutants along a food chain

toxins

accumulate along food chains due to the decrease of biomass and energy

→ DDT, mercury

pyramid of numbers

(can sometimes display different patterns when individuals at lower trophic levels are large)

pyramid of biomass

represents the standing stock or storage of each trophic level (g m^–2 or J m^-2)

(can show greater quantities at higher trophic levels because it’s measured at a fixed point in time)

pyramid of productivity

the flow of energy through a trophic level, indicating the rate at which biomass is being generated

productivity

the conversion of energy into biomass for a given period of time

solar energy unavailable for ecosystems

solar radiation (insolation) that is absorbed by inorganic matter or reflected back into the atmosphere

pathways of energy through an ecosystem

• conversion of light energy to chemical energy

• transfer of chemical energy from one trophic level to another with varying efficiencies

• overall conversion of ultraviolet and visible light to heat energy by an ecosystem

• re-radiation of heat energy to the atmosphere

net primary productivity (NPP)

total amount of energy stored as biomass in producers (energy available for consumers)

NPP

= GPP – R

= gross primary productivity - respiratory losses

gross secondary productivity (GSP)

total energy assimilated by consumers

GSP

= food eaten – fecal loss

net secondary productivity (NSP)

total amount of energy stored as biomass in consumers (energy available for next trophic level)

NSP

= GSP – R

= gross secondary productivity - respiratory losses

carbon cycle

• storages:

  • organic - organisms and forests

  • inorganic - the atmosphere, soil, fossil fuels and oceans

• flows:

  • consumption (feeding)

  • death and decomposition

  • photosynthesis

  • respiration

  • dissolving

  • fossilization

nitrogen cycle

• stores:

  • organic - organisms

  • inorganic - soil, fossil fuels, atmosphere and water bodies

• flows:

  • nitrogen fixation by bacteria and lightning

  • absorption

  • assimilation

  • consumption (feeding)

  • excretion

  • death and decomposition

  • denitrification by bacteria

biomes

collections of ecosystems sharing similar climatic conditions

1. aquatic

2. forest

3. grassland

4. desert

5. tundra

insolation, precipitation and temperature

3 main factors governing the distribution of biomes

tricellular model of atmospheric circulation

explains the distribution of precipitation and temperature and how they influence structure and relative productivity of different terrestrial biomes

zonation

changes in community along an environmental gradient

→ due to changes in altitude, latitude, tidal level or distance from shore (coverage by water)

succession

the process of change over time in an ecosystem involving pioneer, intermediate and climax communities

(patterns of energy flow, gross and net productivity, diversity, and mineral cycling change over time)

early stages of succession

• low biomass

• low gross productivity

• low proportion of energy lost through respiration

• high net productivity

later stages of succession (climax community)

• high biomass

• high gross productivity - balanced by respiration

• ~0 net productivity

r-strategists

• grow fast

• mature early

• produce many small offspring

• give little care to young

→ cockroaches, frogs

favored by natural selection - pioneer communities

K-stategists

• slow growing

• usually large

• have few large offspring

• mature slowly

→ hippopotamus, dolphin, elephant

favored by predictable environments - climax communities

tools for identifying organisms in an ecosystem

• keys

• comparison to herbarium or specimen collections

• technologies

• scientific expertise

Secchi disk

for measuring turbidity

observing effect and classing using Beufort scale or digital anemometer

for measuring wind

dynamometer

for measuring wave action

methods for estimating the biomass in a community

• measurement of dry mass

• controlled combustion

• extrapolation from samples

methods for estimating the abundance of non-motile organisms

• counting using a quadrat

• measuring population density

• measuring percentage cover

• measuring percentage frequency

indirect methods for estimating the abundance of motile organisms

capture–mark–recapture with the application of the Lincoln index

N = (n1 x n2) ÷ m

• n1 - # caught in first sample

• n2 - # caught in second sample

• nm - # recaptured

species richness

the number of species in a community

→ a useful comparative measure

species diversity

function of the number of species and their relative abundance

Simpson diversity index

D = (N(N-1)) ÷ (Σn(n-1))

• N - total # organisms of all species

• n - # individuals of a particular species

  → only useful when comparing two similar habitats, or the same habitat over time

  → the higher the result (D), the greater the species diversity

consumer

an organism that obtains its energy from other organisms

detritivore

an organism that feeds on decaying matter (detritus)

food chain

a sequence of steps that describes how an organism derives energy from the ones before it

interspecific

interactions occuring between members of the same species

intraspecific

interactions between different species

mutualism

interactions between species in which both participants benefit

parasitism

expolitation by an organism of its host

(the host is detrimentally effected by the relationship, but is not usually killed)

• ecto-

• endo-

klepto parasitism

when one animal deliberately takes food from another to feed itself

(manor warbirds attacking tropic birds)

sapotroph

an organism that obtains its energy from dead material by extracellular digestion

keystone species

a species which has a very large influence on the equilibrium stability

transect line (systematic sampling)

sampling used where there is an environmental gradient

rye grass → green common grasshopper → eggs of house sparrow → brown rats → red fox

food chain example

carbon sink

living organisms or non-living materials that store carbon

(ex.: forest, grasslands, kelp, oil, gas, coal, diamonds)

carbon fixing

when gasous carbon is transformed into solid form → photosynthesis

stages of succession

• lichens and moss are blown to an area with very little water and nutrients, but establish anyway → pioneer community

• they die and decompose - create soil

• grasses (dandelion)

• herbaceous plants (stinging nettle)

• shrubs (pines)

• climax community (deciduous trees)

plagioclimax

interrupted succetion - when the climax community isn’t reached

dichotomous key

used to identify an organism by asking yes or no questions

0 - tropical rainforest

• low pressure (rising air)

• high precipitation

• high temperature

• high productivity

30 - hot desert

• high pressure (descending air)

• low precipitation

• large temperature range

• low productivity

1. Hadley

2. Ferrel

3. Polar

cells in tricellular model of global atmospheric circulation (down from equator)