Topic 4
4.1 SPECIES, COMMUNITIES AND ECOSYTEMS
Species – is a group of organisms that can be interbred and produce fertile offspring,
viable offspring
Population – a group of organisms of the same species living in the same area at the
same time
Community - a group of populations living together and interacting with each other
in an area
Habitat – the environment in which species lives or the normal location of a living
organism
Ecosystem – a community and its abiotic environment
MODES OF NUTRITION
Living organisms obtain chemical energy by one of a methods of nutrition (or
both)
Ingestion – taking in a substance
1. Autotrophs – synthesize organic molecules from abiotic inorganic sources
using energy from:
- Light photosynthesis (Photoautotrophs)
- Oxidation Reaction (Chemoautotrophs)
^^^^Producers^^^^
2. Heterotrophs – obtains organic molecules from other organisms, can be
categorized as:
- Consumer (Ingests other living organisms)
- Herbivores, carnivores, omnivores
- Scavengers (Feeds on dead or decaying matter)
- Detritivore (ingests non-living detritus (dead)) ex. Earthworms, snails, dung
beetles
- Saprotrophs (Externally digest dead organisms) ex. Decomposers; bacteria,
mold
- - Organisms that live on non-living organic matter and release enzymes to
absorb nutrients (products of digestion)
Nutrient Cycling
Nutrients – the materials required by an organism for growth and survival
- The supply of inorganic nutrients is finite, hence must be constantly
recycled.
Autotrophs – convert inorganic nutrients into organic molecules
Heterotrophs – ingest organic molecules and many release inorganic byproducts
Saprotrophs – break down the nutrients in dead organisms
- Nutrients released by saprotrophs are returned to the soil for use by
autotrophs
Mesocosms – Ecosystems that have the potential to be sustainable over long periods
of time
Sustainability requires 3 conditions;
Energy availability (ex. Light Source)
Nutrient availability (Decomposers)
Waste recycling (ex. Detoxifying bacteria)
Are enclosed environments with controlled conditions (ex. Terrariums)
To study sustainability
Quadrat Sampling
- The presence of species in a given area can be determined via quadrat
sampling
A rectangular frame is placed in an area
Species numbers are counted/estimated
Sampling process repeated many times
= Is used to access the number of sessile (non-motile) species
Species Association
- The presence of species in a habitat will depend on interactions between
them
- If species are found in the same habitat they show positive association:
Predator-prey relationships
Symbiotic relationships
- If species do not share a common habitat they show negative association:
Competition (exclusive or partitioning)
Chi-squared
- Test can show if there is an association in the distribution of 2 species
Based on data collected by quadrat sampling
4.2 ENERGY FLOW
Energy source – light is the initial energy source for almost all communities (ex.
Photo autotrophs)
Some producers may instead derive energy from chemical processes
(Chemical autotrophs
*Light energy is released via process of photosynthesis*
ENERGY TRANSFER
- Heterotrophs obtain the chemical energy in organic molecules by means of
feeding
Chemical energy is released via process of respiration in heterotrophs and
autotrophs
Trophic Levels
An organisms trophic level refers to the position it occupies in a feeding
sequence
Producers always occupy the first trophic level
Consumers are labelled 1 degree, 2,3,4 etc.
Level 1 = Producer
Level 2 = Primary consumer
Level 3 = Secondary consumer
Level 4 = Tertiary consumer
Food Chains
They show linear feeding patterns between the species in a community
- Arrows indicate direction of energy flow
Examples:
Phytoplankton -> Green mushroom coral -> Yellow tail damsel -> Reef Shark
Buckwheat -> Gopher -> Gopher snake -> Red tailed kite
Food webs
The interconnections that exist among food chains
Each organism may have several sources of nutrition, or be a source of
nutrition
Energy Loss
- Energy stored in a carbon compounds flows through food chains by
means of feeding
Energy is released in forms of carbohydrates and other carbon compounds
energy by cell respiration (heat energy) in the form of ATP
Not all stored energy is transferred upon feeding – most of the energy is lost:
Energy is used to fuel cellular process
- Nucleic acid system
- Ion exchange across membranes
- Cell Division
Heat is by-product of these reactions (heat loss from ecosystems)
Ecosystems need a continuous influx of energy from an external source
Chemical energy is produced by an organism can be converted into a number of
forms:
Kinetic energy (ex. During muscular contractions)
Electrical energy (ex. During transmission of nerve impulses)
Light energy (ex. producing bioluminescence)
= Exothermic, releasing heat =
Energy efficiency
- Energy transformations in living organisms (between trophic levels) are
10% efficient (90% is lost) to account for energy lost through excretory
products, faeces, heat and body that is not consumed
Less energy is available to store biomass at higher trophic levels
Biomass – total mass of all living organisms in a given area/habitat
- As energy and biomass is progressively lost, food chain lengths are
restricted
Food chains have a maximum of 5 levels
= Energy stored in organic molecules (ex. Sugars and lipids) can by released by cell
respiration to produce ATP =
Pyramids of Energy
Representations of the amount of energy at each trophic level
- Energy units per area per time (KJm^2 year^-1)
Pyramids of energy will never be inverted and levels should differ by a factor
of 10
- Because transformations are 10%/effiencient
- Energy is lost as heat from respiration, incomplete digestion and egstion
pyramid of energy
4.3 CARBON CYCLING
Carbon
Forms chemical bases of all known living things
Found in autotrophs, which transform CO2 into more complex molecules, such
as glucose
Carbon dioxide
Gas heavier than air
Solubility increases as pressure increases, can combine with H2O to form
H2CO3 (Carbonic acid)
Unstable and dissociates easy in water in hydrogen ions (H+) and carbonate
ions (HCL)
Hydrogen ions released in this dissociation lowers the pH of the water
Calcium carbonate
Shells of mollusks and exoskeletons of hard corals contain carbon
When animals die, calcium carbonate becomes part of sedimentary rock
Dissolves in acid, but not alkaline solutions
Most oceans are slightly alkaline, creating right conditions for formation of
limestone rock
Carbon cycling
A reservoir is a very large pool or store of an element
When a carbon moves from one reservoir to another it is called a flux.
They tend to be very large reserves of carbon, which have a relatively low
exchange (ex. CO2 dissolved in oceans)
Exchange pools tend to hold smaller amounts of carbon, but more rapid in
exchange
Size of carbon pools and the flux of this element can be measures
- Unit is gigatones
Key features of carbon cycle:
- Carbon exchange involves 4 spheres;
Atmosphere (carbon/methane)
Biosphere (organic compounds)
Lithosphere (detritus and fossil fuels)
Hydrosphere (bicarbonate ions)
Carbon Conversions
ORGANIC:
Autotrophs - convert atmosphere CO2 into organic compounds
Heterotrophs – obtain organic compounds (ex. Carbohydrates) via feeding
The breakdown of carbon compounds via cell respiration (to produce ATP)
releases CO2 as a by-product
AQUATIC:
Carbon Dioxide – may remain dissolved in water or form hydrogen carbonate
Animals – Animals may combine carbonate ions with calcium to form
shells/exoskeletons (ex. Coral, Mollusca)
Carbonate Ions – may also interact with rocks and sediments to form limestone
Methane Production
(CH4) is produce from organic matter under anaerobic conditions (no
air/oxygen)
- Wetlands (swamps and marshed)
- Marine sediments (ex. Mud of lake bed)
- Digestive track of ruminant (cattle, sheep, deer) animals
Methane may diffuse into the atmosphere or accumulate in the ground (gas
deposit)
In the atmosphere, methane is oxidized to form CO2 and water
Methane
organic matter is changed to organic acids and alcohol by a group of bacteria
Other bacteria convert it into acetate, CO2 and hydrogen
Methanogenic archaea can produce methane through reaction of :
CO2 + 4H2 => CH4 + 2H2O or CH3COO- + H+ => CH4 +CO2
Fossils Fuels
- In aerobic condition, decomposers break down organic matter and return
it to soil
- In anaerobic conditions (without air/oxygen) decomposers can not function
and organic matter builds up
Waterlogged soils and sea beds are anaerobic
- Anaerobic respiration produces organic acids, resulting in acidic soil
conditions
Peat/coal
- Organic matter not fully decomposed in anoxic or acidic soils becomes
peat
- When peat is composed under layers of sediment, heat and pressure
remove moisture and transform peat into coal
Oil/Natural
- Marine organisms maybe buried under sediment on the ocean floor after
death
- This burial creates anaerobic conditions and the compaction also
generates heat
- This transforms the organic matter into hydrocarbons
The formation of fossil fuels (coal, oil, gas) takes place over millions of years
- Making them a non-renewable energy source
Combustion
Hydrocarbons undergo a combustion reaction in the presence of oxygen
- Reaction is exergonic (energy is released)
- CO2 and H2O are produced
Sources of hydrocarbons:
Fossilized organic matter (coal, oil, gas)
Biomass (e.g bioethanol and biodiesel)
The energy released via combustion is used to power industrial processes
Industrial combustion is increasing CO2 levels concentration
Also peat fires, car engines, forest fires
Carbon fluxes
- Describe the rate of carbon exchange between sinks and resevoirs
- Driven by number of key process including photosynthesis, respiration,
combustion and lithification (transform into stone)
Reasons for flux change include:
Climate (affects dissolution of CO2 in oceans)
Natural effects (volcanic eruptions)
Human activity (deforestation or combustion)
4.4 CLIMATE CHANGE
Greenhouse gases – absorb and emit long-wave (infared) radiation, thereby trapping
heat within the atmosphere
Greenhouse gas impact depends on:
Ability to absorb long wave radiation
Concentration within the atmosphere
Water Vapour
Carbon dioxide
Methane (CH4)
Nitrogen oxide
H2O and CO2 and CH4 are the most significant
CH4 and N2O have less impact
Greenhouse Effect
- Some gases, such as CO2 and CH4 can absorb longer wavelengths of light
and re-emit them as heat
Is a natural process
Incoming radiation from the sun includes short-wave ultraviolet radiation
Some of this radiation is emitted by Earth as long-wave infared radiation
Greenhouse gases absorb and re-emit this long-wave radiation as heat
which increases average temperatures
The enhanced greenhouse effect is a human induced process (not natural):
Industrial and agricultural processes are increasing emissions of greenhouse
gases
Deforestation is reducing the up-take of CO2 by plants
An increase in greenhouse levels maybe causing global climate change
Climate Change (atmospheric concentration
Higher global temperatures mean total amount of water that evapourates
from oceans and lakes increase as well
Increase H2) in the atmosphere leads to heavier rainfall
Substantial effects, stronger hurricanes, typhoons, changes in ocean currents
Greenhouse gases effect global temperatures and the latter in turn affects
climate change, then global temperatures and climate patterns must be
influenced by changing concentrations of greenhouse gases
More recent increases in atmosphere CO2 are largely due to the increase in
combustion of fossil fuels
- Vehicles for transport
- For central heating
- Production of electricity
- Factories powered by fossil fuels
Scientists predict that greenhouse gas emissions will change global
conditions
- Global Temperatures will increase
- Climate patterns will also be altered
Ocean acidification
The ocean is a major carbon sink that absorbs 30% of humans CO2 emissions
- Absorption by oceans is temperature dependent
- Higher temperatures result in less absorption
When CO2 is absorbed by the oceans:
- Some CO2 remains as a dissolved gas
- Most CO2 is converted into carbonic acid, which dissociates to release H+
ions
This conversion impacts marine organisms (i.e Coral):
- Increases ocean acidity, which can stress coral survival (Higher amounts
of H+ = lower pH levels
- Lowers carbonate ion concentrations, which is required for shells and
exoskeletons
Climate change debate – Is current climate change natural?
Historical Data shows temperature cycles 😊 Claim
Past changes were not as abrupt as current ☹ Counter
CO2 levels are the highest ever recorded ☹ Counter
Are greenhouse gases the cause?
Temperature could be caused by sunspots😊 Claim
Sea levels increased before CO2 emissions😊 Claim
Climate patterns do not match sun activity ☹ Counter
Current rate of sea level increase is higher☹ Counter
Are climate change models reliable?
Different models make varying predictions ☹ Counter
All models predict a temperature increase 😊 Claim
