Population Flashcards
Teen population
A group of organisms of the same species
Population numbers increase because of
Birth and immigration
Population numbers decrease because of
Death and emigration
In stable population
Birth + immigration = deaths + emigration
Density dependent
Abiotic - living
Affect greater proportion of population
Density independent
Biotic - non living
Term carrying capacity
Maximum number of individuals of species that the environment can support indefinitely
Phases of population growth
LAG
LOG
STATIONARY
DEATH
Lag (yeast)
Enzymes are synthesised
Dna is replicated
Log ( yeast)
Population doubles every unit of time
Nutrients abundant
Stationary ( yeast)
Competition of nutrients means death and cell reproduction happen at the same time
Death ( yeast)
Nutrient depletion and toxin accumulation mean death rate is higher than cell reproduction
Ecosystem
An area that has a particular community of plants and animals interacting with their environment
Term community
All of the organisms of all species in an ecosystem
Term habitat
Place in the ecosystem where organisms live
Term niche
An organisms role in ecosystem
Applies particularly to their feeding role
Photoautrophs
Mainly green plants
Use light energy from the sun to fix carbon dioxide into organic molecules by photosynthesis
GPP - R= NPP
Gross and net primary productivity
Why is some energy never taken in at each trophic level
Some parts of food aren’t consumed
Some parts of food indigestible
Plants can’t use all light energy as some is the wrong wavelength
Why is some energy lost at each trophic level
Respiration
Lost as heat
Pyramid of biomass
A table of dry mass of living material at each trophic level of a food chain
Gross primary productivity
The rate of chemical energy fixture during photosynthesis by all producers in an ecosystem
Net primary productivity
The amount of chemical energy that is available to the heterotrophs in an ecosystem
How to calculate net primary productivity
Gross primary - respiratory losses
Term succession
Is the change in structure and species of a community overtime
Term secondary succession
Starts from cleared land where communities have lived before
It is faster as there are seed roots and soil to support the plants
Happens after forest fires or tree felling
Term Sere
Each stage of succession
How is succession depleted
- Mowing
- Burning
- Grazing
Term primary succession
Starts from bare rock where no organisms lives
What are pioneer species
Species that can survive in hostile environments and colonise bare rock
Eg
Lichens
Process of primary succession
- Pioneer species colonise the area
- They die decompose and add nutrients to the ground
- Over time this allows more complex organisms to survive
Climax community
Final stage of succession where ecosystem is balanced and stable
What does succession increase
- Species diversity
- Stability of community
Risk assessment of investigation
- Biting insects
- Stinging plants
- Cover skin
- Use insect repellent
Weather conditions - - Sunburn
- Hypothermia
Representative sampling
Use the correct size grid/quadrant for area
Carry out enough repeats
Carbon cycle
- Plants take in CO2 and use it in photosynthesis to make organic molecules passed through food chains
- Plants and animals respite and excrete CO2
- Combustion releases CO2
- Decomposes respire excreting CO2
- Formation of fossil fuels
Autotrophs
Use energy from sunlight or chemicals to convert inorganic compounds into organic ones
Organic compounds are passed along food chains
Decomposers
Use organic molecules and convert them to inorganic compounds
Human impact on carbon cycle
- Deforestation
- Combustion
- CO2 greenhouse gas
- Global warming
- Agricultural practises
What does deforestation do
It removed trees so less photosynthesis takes place so less CO2 is absorbed from the atmosphere
What does combustion do
Combustion of fossil fuels and wood releases locked in CO2 to the atmosphere
Greenhouse gas on carbon cycle
Traps heat and raises global temperatures therefore causing global warming
Global warming on carbon cycle
Affects species distribution as regions further up north and south of the equator are warmer
Decomposition rate is affected by
Temperature - slower when cold
pH - slower when acidic
O2 availability - slower when less oxygen available
Carbon footprint
Is the total amount of CO2 released attributable to an individual, product or service over the course of a year
Water logged soils
Lack o2 this favours denitrification and slows nitrification
This leads to nitrate poor soil
- ploughing introduces air into soil
- drainage ditches reduce water logging and denitrification
Nitrifying bacteria
Nitrosomonas
Nitrobacter
Nitrosomonas
Convert ammonium to nitrite
Nitrobacter
Convert nitrite to nitrate
Nitrogen fixing bacteria
Convert nitrogen gas to ammonium
Azotobacter
Rhizobium
Azotobacter
Free living in soil
Rhizobium
In root nodules of legumes symbiotic
Denitrifying bacteria
Convert nitrate to nitrogen gas
Pseudomonas - thrive in water logged soils
