Ecology

• Ecosystem: interaction of a community of living organisms and non-living parts of their environment

  Population: all the organism of one species living in a habitat

  Interdependence: how organisms in a community depend on other organisms for vital services
• Abiotic factors

  • light intensity and temperature

  o both affect the rate of photosynthesis (limiting factors) which affects the rate of plant growth

  o plants are good food sources and shelter for many organisms

  • soil pH and mineral content

  o soil pH affects the rate of decay and therefore how fast mineral ions return to the soil to be taken up by other plants

  o different species of plants thrive in different nutrient concentration levels

  o low mineral concentrations could cause nutrient deficiencies reducing plant growth and reducing pop.
• Abiotic factors:

  • wind intensity and direction

  o wind affects the rate of transpiration in plants

  o increased transpiration increases the rate of photosynthesis

  • carbon dioxide levels (for plants)

  o CO2 affects the rate of photosynthesis (see light intensity and temp.)

  o it also affects the distribution of organism as some thrive in high CO2 environments
• Abiotic factors:

  • oxygen levels (for aquatic animals)

  o levels in water vary massively (unlike in the air)

  o most fish need high concentrations of oxygen to survive

  • moisture levels – plants and animals require water to survive
• Biotic factors

  • food availability – more food allows for more successful breeding so population size increases

  • new predator arriving – decreases the population of prey

  • new pathogen – the population has no resistance to it so they can be quickly wiped out

  • competition with a new species – if one species is better adapted to the environment, it will breed more successfully until the lesser adapted species has too small a population to breed successfully
• o Structural – shape or colour of an organism

  ▪ sharp teeth of carnivores to tear meat apart

  ▪ camouflage e.g. white fur in artic regions to avoid being spotted by predators/prey

  ▪ thick layer of fat in cold environments for insulation

  ▪ low surface area to volume ratio to retain heat in cold environments
• o Behavioural – the way an organism behaves

  ▪ playing dead to avoid predators

  ▪ basking in the sun to avoid heat

  ▪ migrating to warmer climates during winter to avoid cold environments
• o Functional – the processes that occur in an organism e.g. reproduction and metabolism

  ▪ conservation of water through producing little sweat and small amounts of concentrated urine

  ▪ hibernation in winter (lowering metabolic rate to conserve energy)
• Extremophiles: Organisms that live in extreme environments e.g. extremely high temperatures, pressures or salt concentrations e.g. example, bacteria which live deep in sea vents where pressure is extremely high
• o all food chains begin with a producer which synthesises molecules

  ▪ glucose produced is used to synthesis other biological molecules in the plant – the biomass

  o producers are eaten by primary consumers

  ▪ energy is transferred through organisms in an ecosystem when one is eaten by another

  o primary consumers are eaten by secondary consumers

  ▪ the animals eaten are called prey and the consumers that kill them are called predators

  o secondary consumers are eaten by tertiary consumers
• • Distribution: where an organism is found

  • Abundance: the population size of an organism

  • Quadrat: 1m x 1m square frame enclosing an area of 1m2
• • Water cycle

  o solar radiation causes evaporation in bodies of water, transpiration in plants also forms water vapour

  o water vapour rises and condenses forming clouds

  o water is returned to the land as precipitation which runs into bodies of water or infiltrates into the group

  o the cycle repeats providing fresh water for plants and animals on land before draining into the seas
• • Carbon cycle

  o CO2 is REMOVED from the atmosphere in photosynthesis by green plants and algae – they use carbon to create carbohydrates, proteins and fats (carbon compounds). Plants are eaten moving carbon up the food chain

  o CO2 is RETURNED to the air when plants, algae and animals respire, decomposers (microorganisms that break down dead

  organisms and waste) respire while returning mineral ions to the soil

  o CO2 is RETURNED to the air when wood and fossil fuels are burnt (combustion) as they contain carbon
• Decomposition

  o Temperature – increasing temperatures increases the rate of decomposition as they increase the rate at which enzymes involved in decomposition work. If too hot/cold the enzymes denature stopping decay

  o Water – decay takes place faster in moist environments because decomposers need water for respiration (producing energy for movement, decomposition and growth)

  o Availability of oxygen – decomposers need oxygen to respire (produce energy)

  o Number of decomposers – the more decomposers and detritus feeders there are the faster the decay

  occurs
• • Anaerobic decay by decomposers (to decompose organic matter) produces methane gas

  o biogas (made of mainly methane) is made in a simple fermenter called a biogas generator

  o biogas generators need to be kept at 30°C to keep the decomposers respiring

  o the biogas produced can’t be stored as a liquid (needs too high of a pressure) so it has to be used straight away e.g. burnt for heating, cooking or to power a turbine to generate electricity
• o there are 2 forms of biogas generator

  ▪ batch generators – manually loaded with waste which is left to digest, and the by-products are cleared away at the end of each session (produces biogas in small batches)

  ▪ continuous generators – make biogas all the time as waste is continuously fed in and the biogas is produced at a steady rate (more suited to large scale biogas production)
• • environmental changes affect distribution of species in ecosystem

  o Temperature – increasing temperatures leads to migration of species

  o Availability of water – during wet and dry seasons the amount of rainfall will change, populations migrate to find water

  o Composition of atmospheric gases – air pollution can affect which species can be present
• • a high biodiversity ensures the stability of an ecosystem by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment
• Peat bogs

  • peat forms when plant material has not fully decayed due to lack of oxygen, this accumulates in bogs which are acidic and waterlogged

  • the destruction of peat bogs (and other areas of peat to produce garden compost)

  o reduces the size of this habitat reducing the biodiversity

  o the decay and burning of peat releases carbon dioxide into the atmosphere

  • they are being destroyed faster than it is being formed (as formation is slow)
• • effects of deforestation

  o release of CO2 – trees contain carbon which is oxidised during combustion to release CO2 (contributes to global warming) also microorganisms decompose dead vegetation producing CO2 as they respire

  o reduction in absorption of CO2 – less trees means less photosynthesis

  o decreased biodiversity – trees act as habitats for a huge range of species
• o breading programmes for endangered species – avoids extinction

  o protection and regeneration of rare habitats – e.g. mangroves and coral reefs (protects the species that live there preserving the ecosystem)

  o reintroduction of hedgerows and field margins – especially if only 1 crop grown on the field it increases biodiversity by providing a habitat for many species
• Trophic levels:

  o Level 1 – producers (plants and algae that produce their own food by photosynthesis - autotrophs)

  o Level 2 – primary consumers (herbivores that eat plants/algae)

  o Level 3 – secondary consumers (carnivores that eat herbivores)

  o Level 4 – tertiary consumers (carnivores that eat other carnivores)
• • biomass is lost due because...

  o not all ingested material is absorbed (some is egested as faeces)

  ▪ animals do not have all the enzymes to digest all the material they eat

  o some absorbed material is lost as waste e.g. carbon dioxide and water in respiration and urea in urine

  o large amounts of glucose are used during respiration

  o not all biomass can be eaten e.g. carnivores don’t generally eat bone or teeth
• efficiency of biomass transfer = biomass transferred to the next level ÷ biomass available at previous level
• Biological factors threatening food security

  o increasing birth rate

  o changing diets in developed countries means scarce food resources are transported around the world

  o new pests and pathogens that affect farming

  o environmental changes affecting food production e.g. lack of rain causing draughts

  o cost of farming e.g. seeds and machinery

  o conflict affects the availability of food and water
• • the efficiency of food production can be improved by restricting energy transfers from food animals to the environment by...

  o limiting their movement (small pens or cages)

  o controlling the temperature of the surroundings (less energy to control own body temperature)

  o feeding animals high protein foods to increase growth
• • mycoprotein – protein-rich food source suitable for vegetarians made from the fungus Fusarium

  o the fungus is grown in glucose syrup

  o air and ammonia are added so the conditions are aerobic, and the protein can be made using the nitrates

  o the fungal biomass is harvested and purified

  o ADVANTAGES OVER ANIMAL PROTEIN - reduces land use as animals take up a lot of land and reduces methane production (as livestock’s digestive systems produce lots of the greenhouse gas)
• • genetically modified bacteria

  o a plasmid is removed from a bacteria using lysozyme

  o the insulin producing gene is removed from a human chromosome using restriction enzyme

  o the plasmid is cut open using the same restriction enzyme – leaving the same sticky end

  o the plasmid and human gene are joined using ligase enzyme which joins the sticky ends producing recombinant DNA

  o the recombinant DNA is inserted into a bacterium

  o the transgenic bacterium is grown in a vat, millions of identical bacterium are collected which all produce human insulin – the insulin is

  harvested and purified
• o Advantages

  ▪ GM crops can be resistant to pests and extreme weather (e.g. draughts) improving yields

  ▪ some crops are modified to have more nutritional value e.g. Golden Rice contains beta-carotene which is high in vitamin A (helps to prevent blindless)
• o Disadvantages

  ▪ there are fears that some countries may become dependent on countries producing GM seeds

  ▪ sometimes poor soil is the reason crops fail so even GM crops wouldn’t survive

  ▪ GM crops are aften more expensive so won’t help combat food insecurity

  ▪ there are concerns over their impacts on health e.g. they may cause allergies

  ▪ concerns that if the genes reach weeds “super weeds” could be produced which are herbicide resistant