Biology Ecology

Species

a group of organisms that can potentially interbreed to produce viable and fertile offspring

Community

a group of populations living together and interacting with each other within a given area

Habitat

the environment in which a species normally lives or the location of a living organism.

Ecosystem

A community and its abiotic environment

Autotrophs

synthesises its own organic molecules from simple inorganic substances

• energy for this process is derived from sunlight (photosynthesis) or via the oxidation of inorganic molecules (chemosynthesis)

• as autotrophs synthesize their own organic molecules --> producers

Heterotrophs

obtains organic molecules from other organisms (Either living/recently dead or their non living remains and detritus)

because heterotrophs cannot produce own organic molecules and obtain it from other sources, called consumers

Mixotrohphs

Certain unicellular organisms may on occasion use both forms of nutrition, depending on resource availability
Euglena gracilis possess chlorophyll for photosynthesis (autotrophic) but may also feed on detritus (heterotrophic)

define scavengers

principally feed on dead and decaying carcasses rather than hunting live prey

Why do chemical elements need. to be constantly recycled

The supply of inorganic nutrients on Earth is finite

• new elements cannot simply be created and so are in limited supply

• Hence chemical elements are constantly recycled afterward

Describe the nutrient cycle

• Autotrophs obtain inorganic nutrients from the air, water and soil and convert them into organic compounds

• Heterotrophs ingest these organic compounds and use them for growth and respiration, releasing inorganic byproducts

• When organisms die, saprotrophs decompose the remains and free inorganic materials into the soil

• The return of inorganic nutrients to the soil ensures the continual supply of raw materials for the autotrophs

What are the three main components required for sustainability in an ecosystem?

Energy availability - light from the sun provides the initial energy source for almost all communities
Nutrient availability - saprotrophic decomposers ensure the constant recycling of inorganic nutrients within an environment
Recycling of wastes - certain bacteria can detoxify harmful waste byproducts (e.g. denitrifying bacteria such as Nitrosomonas)

What is a mesocosm?

enclosed environment that allows a small part of the natural environment to be observed under controlled conditions

• aquariums

Trophic Level

The position an organism occupies on the feeding sequence

Food Chain

A food chain shows the linear feeding relationships between species within a community

Population

a group of organisms of same species that are living in the same place at the same time

Ecology

study of the relationship between living organisms and their environment

How can autotrophs be classified according to their mode of nutrition?

Autotrophs produce their own organic molecules using either light energy or energy derived from the oxidation of chemicals

How can heterotrophs be classified according to their mode of nutrition?

Heterotrophs obtain organic molecules from other organisms via one of three methods:
-Consumers ingest organic molecules from living or recently killed organisms
-Detritivores ingest organic molecules found in the non-living remnants of organisms (e.g. detritus, humus)
-Saprotrophs release digestive enzymes and then absorb the external products of digestion (decomposers)

Where do autotrophs obtain the inorganic molecules?

air, water, soil

What type of organisms are quadrat tests used for?

counting plants and sessile (immobile) animals

What do the arrows in a food chain represent?

the transfer of energy and matter as one organism is eaten by another

arrows indicate the flow of energy

first organism is always the producer

is all energy transferred during the heterotrophic feeding?

not all energy stored in organic molecules is transferred via heterotrophic feeding

• some energy is lost by excretion and unconsumed portions of food

What forms can chemical energy produced by an organism become?

chemical energy produced by an organism can be converted into:

• kinetic energy - muscle contractions

• electrical energy - nerve impulse

• light energy - bioluminescence

what type of reactions are all of these?

exothermic: release thermal energy as a byproduct

can living organisms turn the heat released from the exothermic reactions into other forms of energy? explain

no they cannot.

• heat energy is released from organism and LOST from the ecosystem (unlike nutrients that are recycled)

• Hence, ecosystems require continuous flux of energy from an external source —>SUN

How efficient are energy transformations?

typically energy transformations are around 10% efficient and 90% of available energy is lost between trophic levels

Biomass

total mass of a group of living organisms - consisting of the same carbon compounds contained in the cells and tissues

why are potential trophic levels limited?

biomass and energy is lost between each level

• higher tophic levels recieve less energy/ biomass from feeding so need to eat larger quantities to obtain sufficient amounts

• because higher trophic levels need to eat more, they expend more energy and biomass hunting for food

• if energy required to hunt exceeds the energy available from the food eaten, the trophic level becomes unviable

Carbon cycle

biogeochemical cycle whereby carbon is exchanged between different spheres of earth

what are the 4 spheres of the earth

atmosphere

lithosphere

hydrosphere

biosphere

carbon is exchanged in a variety of forms, name some of them

atmospheric gases (CO2 and some CH4)

oceanic carbonates (bicarbonates, calcium carbonates from shells)

organic materials (lipids, carbohydrates, proteins)

non-living remains (detritus, fossil fuels)

are the levels of CO2 in autotrophs always high or low

the level should always be low as autotrophs convert inorganic CO2 into organic compounds via photosynthesis

what 2 processes is the amount of CO2 in the environment determined by?

determined by the level of photosynthesis and cell respiration

• if there is more net photosynthesis than cell respiration occurring in the biosphere, atmospheric CO2 levels should drop

• if there is more net respiration than overall photosynthesis occurring, atmospheric CO2 levels should increase

Describe the process in which fossil fuels form

waterlogged regions may lack oxygenated air spaces within the soli, possessing anaerobic conditions.

• Saprotrophic bacteria require oxygen to effectively function, thus decomposition is prevented

Coal

• since organic matter is not fully decompose, carbon rich molecules remain in the soil and form peats

• when deposits of peat are compressed under sediments, heat and pressure force out impurities and remove moisture

• the remaining material has high carbon concentration and undergoes a chemical transformation to produce coal

Oil/ Natural gas formation

• form as a result of the decay of marine organisms on the ocean floor

• sediments deposited on top of the organic matter form anoxic conditions that prevent decomposition

• as a result of burial an compaction, organic material becomes heated and hydrocarbons are formed

• hydrocarbons form oil and gas, which are forced out of source rock and accumulate in porous rocks eg sandstone

name 3 combustion sources

fossil fuels

biomass

what are the four main carbon sinks?

lithosphere

hydrosphere

biosphere

atmosphere

what organisms produce methane

methanogens

archaen microorganisms that produce methane as a metabolic byproduct in anaerobic conditions

where can methanogens be found

wetlands, marine sediments, digestive track of ruminant animans like cows, sheep, goats

is it possible to directly measure the size of carbon sinks or the fluxes between them?

no. estimates are made instead

global carbon fluxes are very large and therefore measured in gigatons

because carbon fluxes are large and based on measurements from many diff sources estimates have large uncertainty

what is a carbon flux

describes the rate of exchange of carbon between various sinks

what are the main causes of flux change

Climate conditions

• rate of photosynthesis

• oceanic temperatures

• climate evens el nino and la nina

• melting polar ice caps

Natural events

• forest fires

• volcanic eruptions

Human activity

• clearing of forests for agricultural purposes

• increase number of ruminant livestock

• burning fossil fuels

describe the carbon data of the Keeling Curve (CO2 levels)

all stations show that a clear upward trend in atmospheric CO2 concentrations year on year, with annual fluctuations

diff monitoring systems may have slightly diff trends due to seasonal variations and distribution of local vegetation

CO2 levels are steadily increasing each year since the industrial revolution due to the increase burning of fossil fuels

Atmospheric CO2 levels are currently at the highest ever recorded since instruments began

which GHGs have the largest warming effect on the atmosphere

CO2 and water

what is the GHG effect?

• natural process in which earth acts like a greenhouse, trapping ehat

• this ensures that earth can maintain a moderate temperature for organisms to maintain life processes (homeostasis)

• incoming radiation

• earth absorbs short-wave radiation. and reemits long-wave infrared. Long wave is absorbed by GHG and reradiated back to the earth’s surface, retaining heat within the atmosphere for longer

what are the 2 factors that determine how much of an impact GHGs will leave

1. ability to absorb long wave radiation

2. concentration in the atmosphere

what is the enhanced greenhouse gas effect?

impact on the climate from the additional heat retained due to the increased amounts of CO2 and other GHGs that humans have released into the atmosphere since the industrial revolution

• more freq extreme weather conditions

• some areas become more drought affected

• changes to circulating ocean events

What did data collected from the ice cores from Antartica provide?

strong correlation between CO2 conc. and temp

there were fluctuating cycles of CO2 conc. which appear within global warming ages and ice ages

current concentrations of CO2 is higher than any time in the last 400,000 years

How does increasing levels of CO2 result in acidified oceans

when oceans absorb CO2, some is dissolved but most is chemically modified

CO2 will combine with water and form carbonic acid, which dissociates to form H+ ion and hydrogen carbonate ions

• H+ ions lowers the ocean pH and combine with free carbonate, leaving less free carbonate in water, lowering alkalinity and increasing acidity

What are the consequences of ocean acidification?

due to the lowered amount of free carbonates in the water, marine organisms are less able to produce calcium carbonate (via calcification)

• calcium carbonate is used to form the hard exoskeleton of coral and shells of molluscs

• thus it threatens the viability of coral reefs and certain molluscs

  • disappearance of coral reefs, resulting in loss of shoreline protection and habitat, altering coastal ecosystems

  • loss of revenue from tourism and food industries: predicted to cost economies 1 trillion by 2100

  • inc concentrations of CO2 in ocean causes invasive species of algae to flourish (more photosynthesis)