IB Biology - Chapter 4: Ecology

biotic

living things

abiotic

non-living things

species

a group of organisms that can interbreed and produce fertile offspring

habitat

the environment in which a species normally lives

population

a group of organisms of the same species which are in the same area at the same time

community

a group of populations living and interacting with each other in the same area

ecosystem

a community and its abiotic factors

biomass

the total mass of organisms in a given area or volume

autotroph

an organism that is able to form nutritional organic compounds from simple inorganic compounds such as carbon dioxide (grass, flowers)

heterotroph

an organism that consumes organic compounds from other organisms as its source of energy/organic matter (fish, sheep)

detritivore

an organism that consumes non-living organic matter as it's energy source (earthworms, dung beetles)

saprotroph

an organism that lives in or on non-living organic matter, secreting digestive enzymes and absorbing the products of digestion. they play a large role in the decay of dead organic matter.

consumer

an organism that cannot make its own food from inorganic compounds, so they get their nourishment from ingesting other organisms (humans, lions)

reproductive isolation

separation of a species or population so that they no longer interbreed and evolve into two separate species

quadrat sampling

method used to predict the number of organisms in a large area based on sampling a smaller area

positive association

occurs when 2 species are often found in the same habitat (possibly predator and prey/symbiotic relationship)

negative association

occurs when 2 species tend to not be found in the same habitat

no association

occurs when 2 species do not interact; they are independent of each other

chi-squared test

a statistical tool used to determine whether there is a statistically significant association between 2 variables. it is used to determine if there is a relationship between the distribution of 2 different organisms living in the same area

null hypothesis (H0)

there is no significant difference between the distribution of the 2 species (random distribution, not associated)

alternative hypothesis

there is a significant difference between the distribution of the 2 species (not random distribution, they are associated)

photoautotrophs

organisms that perform photosynthesis

flow of energy

chemical energy in carbon compounds flows through the food chain by feeding

trophic level

the position an organism occupies within a feeding sequence

first trophic level

producers

second trophic level

primary consumers

third trophic level

further consumers (secondary, tertiary, etc)

how efficient is the energy process?

only about 10% of energy is passed between each trophic level

where does the other 90% of energy in between trophic levels go?

1) gets used up in metabolic processes

2) exothermic - released as heat energy when they are used in reactions

3) some energy gets stored in organic molecules (lipids, sugars) - this energy is later released via cell respiration to produce ATP

exothermic

when thermal/light energy is a byproduct of a reaction

why do ecosystems require a continuous reflux of energy from an external source (like the sun)?

bc energy is lost from the ecosystem!

1) heat energy is released from organisms

2) energy that is left undigested is excreted as a part of an organism's faeces

3) some energy is left unconsumed

4) some is lost through respiration

chemical energy can be converted into...

kinetic (muscular contractions), electrical (transmissions of nerve impluses), light (bioluminescence)

key parts of the carbon cycling diagram

atmosphere, biosphere, lithosphere, hydrosphere

autotroph conversion

they convert atmospheric carbon dioxide into organic compounds via photosynthesis

heterotroph conversion

obtain organic compounds via feeding and break them down via cell respiration (which produces carbon dioxide which they breathe out via diffusion)

methane production

methane is produced from organic matter by methanogenic archaeans which requires anaerobic conditions (eg. wetlands, marine sediments, digestive tract of ruminant animals)

oxidation of methane

methane ->oxidation-> carbon dioxide + water

what does anaerobic respiration produce?

organic acids which result in acidic oil conditions

peat

organic matter that is not fully decomposed in anoxic or acidic soils

coal

is created when peat is compressed under layers of sediment, heat and pressure (removes the moisture and transforms peat into coal)

hydrocarbon examples

oil and gas

what happens when hydrocarbons are in the presence of oxygen

they undergo a combustion reaction (exergonic - energy is released), CO2 and H2O is produced

source of hydrocarbons

fossilized organic matter (coal, oil, gas), biomass (bioethanol, biodiesel)

carbon fluxes

describe the rate of carbon exchange between sinks and reservoirs (ie. forests, soil, atmosphere, ocean)

reasons for flux change

climate, natural events, human activity

greenhouse gases (GHGs)

absorb and emit long-wave infrared radiation, trapping heat in the atmosphere in order to heat the Earth's surface and lower atmospheric levels. when humans produce excess GHGs, the balance is ruined and the GHGs emitted into the atmosphere traps excess heat causing global warming.

examples of GHGs

water vapour, carbon dioxide, methane, nitrous oxide

greenhouse effect

incoming radiation from the Sun includes short-wave, ultraviolet radiation. this is absorbed and reflected, however some gets absorbed by GHGs in the atmosphere and re-emit this long wave radiation as heat. therefore increasing avg. global temps.

enhanced greenhouse effect

human induced process, not natural.

1. industrial & agricultural process increase GHG emissions (CO2, methane, etc.).

2. deforestation reduces uptake of CO2 by plants

3. increase in GHG levels may be causing global warming

long-term evidence of climate change

CO2 levels throughout history can be measured from ice cores. Vostok ice core shows a strong correlation between global warming and CO2 levels.

recent evidence of climate change

- CO2 emissions have been rising since the industrial revolution

- Mauna Loa monitored atmospheric CO2 levels and found that there is a seasonal cycle of emissions. there has also been a steady increase in the CO2 emissions since 1958.

CO2 absorption by the ocean depends on what?

temperature dependent. higher ocean temps reduce CO2 absorption. colder waters have slower moving particles, so gases can be held in them better and do not escape from the water as easy compared to warmer waters which have faster moving particles.

when CO2 is absorbed in oceans...

some is dissolved as a gas but most is converted to carbonic acid, which dissociates to produce H+ ions. this makes the water more acidic, as the abundance of H+ lowers the pH.

relationship between atmospheric CO2 levels and the pH of oceans

as atmospheric CO2 levels increase, the ocean becomes more acidic.

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