Ecology

Definitions Ecology: the study of all the interactions (btw living things and btw living & non-living

things) that occur within the BIOSPHERE. Ecosystem: all the interacting parts of a biological COMMUNITY and its environment; a

group of living organisms that, along with their ABIOTIC environment, form a self-regulating system through which energy and materials are transferred.

Abiotic factors: non-living parts of the environment (e.g. water, elements, temperature & climate, wind)

Biotic factors: living parts of the environment (e.g. plant and animal organisms) Biodiversity: variety of living organisms that inhabit Earth or in a given area Decomposers: (food chain role) various bacteria & fungi that break down dead material and

animal wastes and extract the remaining nutrients Population: all the individuals of one species that occupy a certain geographical area

during a certain time Community: groups of different species of organisms that interact together (e.g. a

community of soil or stream organisms); all the populations in an ecosystem Food chain: a hierarchy of organisms through which energy is transferred in the act of

eating, and involves TROPHIC LEVELS; directional Food web: a hierarchy of organisms in which each organism gains energy from eating;

thus, interconnected food chains Niche: the role an organism fills in an ecosystem Habitat: the place where an organism lives, including needs such as a water supply Autotroph: (energy term) an organism that produces complex organic compounds from

simple inorganic molecules using energy from light or inorganic chemical reactions; the producers in a food chain

Heterotroph: (energy term, equivalent to the food chain role CONSUMER) an organism that requires organic substances to get its carbon for growth and development

Saprotroph: (energy term, equivalent to the food chain role DECOMPOSER) an organism that gains its energy and chemical nutrients from dead plants and animals

Primary consumer: (food chain role) first consuming organism (herbivore/omnivore) Sec. consumer: (food chain role) second consuming organism (carnivore/omnivore) Trophic level: the feeding level based on energy in a food web (e.g. producers, primary

consumers, secondary consumers) Producer: (food chain role) green plants and some species of bacteria that use

photosynthesis Herbivore: an organism that only consumes plants Carnivore: an organism that only consumes meat Omnivore: an organism that consumes plants and meat

Biome: a group of ecosystems which are similar or related to each other in the dominant form of plants or climate… (e.g. Boreal forest biome, tundra)

Natural ecosys: developed naturally; typically constantly changing and biodiverse Artificial ecosys: controlled by humans; typically changes little and lacks biodiversity Ecotones: a transition area between bordering ecosystems with much biodiversity Bioamplification: the effect in which harmful chemicals accumulate as they go up in the food

chain; results in very high (harmful or lethal) concentration in top carnivores Symbiosis: (also, SYMBIOTIC RELATIONSHIP) a relationship between two or more species

o Mutualistic: a symbiosis in which both species benefit o Parasitic: a symbiosis in which one species benefits and the other is harmed o Commensal: a symbiosis in which one species benefits and the other is neutral

Scavengers: (food chain role) organisms that consume leftovers and scrap materials, but which do not produce nutrients in a form suitable to be reused by producers; their wastes must be further broken down

In order of largest to smallest: biome → ecosystem→ community→ population

At-Risk Extinct: species no longer found anywhere

e.g. blue walleye Endangered: species close to extinction in a large area

e.g. eastern cougar Extirpated: species does not exist in one area but can be found elsewhere

e.g. grizzly bear Threatened: species likely to become endangered if factors are not reversed

e.g. wood bison Vulnerable: species at risk because of low/declining numbers in outer/restricted area

e.g. grey fox Causes

o Disturbances in the food chain (e.g. loss of food source) o Human intervention o Environmental change

Pyramids Show hierarchy of food chain, trophic levels To draw one:

o Title should indicate type of pyramid, organisms and/or food chain o Scale (e.g. 50 organisms per square / 100 kg per square / 100 kJ/m2 per square) o Centre line (all bars should be centered) o Label each bar (with species and numerical data)

Pyramid of Numbers Based on number of organisms (population) at each level May be inverted if size differs greatly

o e.g. tree -> birds & insects

Pyramid of Biomass Based on dry mass of each trophic level

o Usually uses kg as unit May be inverted if life spans or reproduction rates differ significantly

o e.g. phytoplankton (small mass, consumed quickly but reproduce quickly) -> fish

Pyramid of Energy Based on energy transferred between the trophic levels

o Usually uses kJ/m2 as the unit Can never be inverted

Water Cycle A: precipitation over land B: precipitation over water C: transpiration

o Plants lose water from leaves D: seepage from ground

o Water goes from the surface down into the water table, seeps into lakes and oceans

E: runoff o Rivers o Melting snow, glaciers

F: evaporation

Carbon Cycle Carbon is a NUTRIENT: a chemical element used by organisms to build and operate.

All organic molecules require C Inorganic: does not contain a combination of C and H

o e.g. CO2 gas, carbonates (CO3) as part of H2CO3/CaCO3 Organic: contains a combination of C and H, but not in carbonate form, CO2 or cyanates

o Usually as carbohydrates (sugars), fats, proteins, DNA, cellulose

Photosynthesis

6H2O(l) + 6CO2(g)∆energy from sun�⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯� C6H12O6 + 6O2↑

o Water and carbon dioxide yield glucose and oxygen (released into atmosphere) o Sugars move through food chain; consumed, broken down, rebuilt into molecules

Cellular respiration o Reverse of photosynthesis

C6H12O6(s) + 6O2(g) ⟶ 6H2O(l) + 6CO2(g) + energy o All living organisms respirate

Carbon reservoirs o Inorganic

Atmosphere: CO2 gas Geologic: rocks in the crust contain carbonates Dissolved in oceans as H2CO3 and CaCO3 of shells

• Shells deposit as sediment on ocean floor and becomes sedimentary rock (i.e. limestone); may be trapped for millions of years

o Organic Bodies of living organisms

Aerobic/anaerobic decomposition o Aerobic: with O2 Anaerobic: without O2 o Bogs and swamps: anaerobic decomposition, slower

Locks C in dead organic matter (peat) Peat compresses into fossil fuels -> coal, oil, gas

Release from reservoirs o Geological processes (uplifting (mountains), erosion, weathering) o Limestone is used in industrial applications (i.e. making cement) o Volcanic activity o Acid rain (H2CO3 in rain water) o Combustion of fossil fuels

CO2 in atmosphere

plants 1° consumer 2° consumer

photosynthesis

respiration

death

decomposers

Nitrogen Cycle Nitrogen is an essential element for life: amino acid, nucleic acids, and ATP contain nitrogen.

NITROGEN FIXATION o Legumes and bacteria on their

root nodules o Lightning also fixates nitrogen

gas directly into nitrates o Nitrogen-fixating bacteria

convert atmospheric nitrogen to ammonia (NH3); AMMONIFICATION

o Other bacteria convert fixated nitrogen into nitrate in NITRIFICATION: Ammonia -> nitrite

(NO2) Nitrite -> nitrate (NO3)

o Nitrate is consumed by plants; some plants can use ammonia

o Soil rich in nitrate / ammonia are excellent for plant growth o Animals then consume, and their wastes undergo NITRIFICATION (if ammonia) or

DENITRIFICATION (if nitrates) To be clear: nitrogen fixation through bacteria is a two-step process (ammonification and nitrification). Denitrification

o Microscopic bacteria, fungi break down nitrates and release nitrogen gas

Phosphorus Cycle Does not involve atmosphere. Involves erosion, plant absorption from water, wastes returning phosphates to water, runoff, and sediment that is then returned through geologic upthrust.

Takes millions of years, but has a short cycle: wastes recycled by decomposers, phosphates dissolved in water, plants absorb from water.

Populations Factors affecting population size:

o Birth o Death o Immigration — only in open populations o Emigration — only in open populations

BIOTIC POTENTIAL: max # of offspring a species can produce w/ unlimited resources o BIRTH POTENTIAL: max # of offspring per birth

Humans are limited (1–6,7), but fish can lay hundreds of eggs at one time o CAPACITY FOR SURVIVAL: # of offspring that reach reproductive age

Turtle eggs and fish eggs, for instance, don’t have a high capacity o PROCREATION: # of times a species reproduces a year

Humans are limited by the 9-month pregnancy o LENGTH OF REPRODUCTIVE LIFE: age of sexual maturity & # of years the individual can

reproduce Carrying capacity: max # of individuals of a species that can be supported indefinitely by an

ecosystem; depends on availability of resources Density-dependent factors: water quality, disease, food availability... affected by population Density-independent factors: fire, flood... natural events or resources that affect population but

which do so regardless of its density Population grows when BIOTIC POTENTIAL > ENVIRONMENTAL RESISTANCE (abiotic & biotic factors

that limit or harm growth) Population decreases when ENVIRONMENTAL RESISTANCE > BIOTIC POTENTIAL Population curves

o J-curve: population explosion, usually followed by crash due to famine or resource deficiency

o Reverse-J-curve: population crash o S-curve: fluctuating growth, usually because of predator-prey balance

Inverse relationship: as one goes up, the other goes down