Biology Unit 4.1

Species

  • A group of genetically similar organisms which can interbreed and produce fertile offspring
  • Members of the same species have a common gene pool

Species can become reproductively isolated because of

  • Geographical barriers
  • Behavioural differences
  • Niche partitioning

Population and communities

Autotrophs

  • Organisms who can form nutritional organic substances from inorganic molecules (photo and chemo synthesis)

Chemoautotrophs

  • Produce organic molecules from chemical energy

Photoautotrophs

  • Produce organic molecules from light energy

Cyanobacteria
grass
algae

Heterotrophs

  • Organisms who gain their organic compounds by consuming other organisms

Consumers

  • Organisms who are not capable of synthesising their own food and must gain it by consuming other organisms through ingestion or absorption
  • Take the energy rich carbon compounds such as sugar, proteins, lipids

Detritivores

  • Organisms that gain their nutrients via feeding off dead organic matter

Saprotrophs

  • Obtain energy from detritus through external digestion by excreting enzymes to break down the debris around them

Primary, secondary and tertiary consumers

Communities


Mutualism

  • Both organisms benefit
    Commensalism
  • One organism benefits and other unaffected
    Parasitism
  • One benefits and the other affected
    Predator-prey
  • One organism hunts and feeds on another

Nutrient Cycling

  • The continuous flow and reuse of nutrients and other chemicals in and out of stores in an ecosystem
    • The movement of organic molecules and minerals through the food chain and back into the soil so that it can be reabsorbed by plants and reenter the food chain

Decomposers convert the organic molecules in detritus in order for it to be used for themselves and other animals

Biology Unit 4.2

Food chains, webs and loss of energy between trophic levels

Food chain: A sequence showing the feeding relationships and energy flow between species


Food web: Shows the interconnecting relationships that exist amongst food chains

Energy transfer per trophic level is estimated to be around 10-20% due to

  • Loss of heat due to respiration
  • Loss of nutrients due to excretion
  • Loss of nutrients due to not eating the entire of an animal

Energy (like heat) cannot be recycled after it is lost due to respiration

Pyramids of energy

  • Show the number of energy available per trophic level
  • cannot have a larger second layer than first layer as there has to be sufficient energy to sustain larger animals
  • Kj m-2 y-1

Pyramids of numbers

  • Show the population numbers in each trophic level

click to edit

Biology Unit 4.3

Role of autotrophs in carbon cycle
Autotrophs take carbon out of the atmosphere and convert it to carbohydrates and oxygen

Carbon dioxide in water

When carbon dioxide diffuses into water, it creates bicarbonate ions and H+ ions
-H+ ions change the pH of water, making it more acidic

Methane

Methanogens
A group of archaebacteria that produce methane as a by product of their metabolism

Peat formation
Peat forms when organic matter is not fully decomposed because of anaerobic conditions in waterlogged soils

  • Very acidic = decomposers cannot live and more peat accumulates

Fossil fuels (oil, gas and coal)

Remains of dead plants and animals compiled in anoxic conditions exposed to heat and pressure within the earth's crust over hundreds of millions of years, eventually converted into oil, natural gas, or coal

Carbon cycle

Carbon can be taken out of the atmosphere by plants and stored or used to make oxygen and carbohydrates

Marine life can use carbon in water to make shells and coral reefs

Accumulation of shells goes through the process of lithification, creating a large carbon sink

Animals respire and release carbon back into atmosphere

Some animals eat other organisms and excrete, taking out and once again releasing carbon

Burning of fossil fuels from natural fossil fuel sinks

Biology Unit 4.4