Population Size And Ecosystems Flashcards
What is succession
The change and structure and composition of species of a community over time
Pioneer organism
First organisms to colonise bare rock e.g. Lichen
Primary succession and secondary succession
Primary - introduction of organisms to a habitat which had not been previously colonised
Secondary -
Reintroduction of organisms to an area that has previously been occupied.
Stages of succession
Pioneer species
Weathering of rock by lichens and accumulation. If dead decomposing organic material leads to a primitive soil to form animals e.g. Ants can survive
Wind blown spores allow mosses to grow as soil develops herbaceous plants outcompete mosses and establish there
Tall grasses allow shade tolerant species to come about community becomes more complex
As these animals and plants decay soil becomes thicker improving soil structure can hold more water and nutrients
As the soil thickens large trees such as oak outcompete shrubs climax community has been reached has a greater species diversity
Complex food web dominated by long living plants
Human influence of succession
May prevent climax community
Grazing by animals maintains grassland and prevents shrubs and tress normal succession taking place
Farming land removes all except deliberate species and great effort in expanding and excluding all others
Deforestation removes community of large trees although small trees may be replanted
Factors affecting succession
Migration- arrival of spores, and animals vital for succession to progress immigrating non native species may spread themselves widely altering community and soil
Competition - intraspecific - between individuals of same species density dependant as population increases more competition . When population proportion fails to survive importance when produce to many offspring regulates everything
Inter specific - of different species , e.g all fish compete for dissolved i2 in water All have different needs (own niche) e.g occupies a particular place
Competition operates at all sevral stages two species cannot have same niche in specific habitat whichever has competitive advantage will survive
Mutualism - interaction between species that is beneficial to both
Commensalism - loose interaction between organisms of two species which one benefits other is not affected
Impact of deforestation
The rate at which co2 up is removed from atmosphere by process of photosynthesis is reduced by cutting down forest and contributes to global warming
When trees are cut down they may be burned or left where they are cut to decay both these processes release co 2 in atmosphere
Climate change
Burning fossil fuels particularly industrialised and global transport contributes to steep increase in green house emissions
Greenhouse effect -
Carbon dioxide , methane nitrous oxide act like a window of a greenhouse allowing short wavelength solar radiation to pass through the earths surface which warms up the earth and re radiates lower energy longer wavelength radiation so planetary surface of earth warms up with human influence contributes to further warming
Consequences of global warming
Melting polar ice caps resulting in flooding in coastal areas
Increased frequency of extreme weathers e.g.droughts and cyclones increased forest fires
Evolutionary adaption is slow compared to climate change if animals cannot adapt quick enough will become extinct
Fishing areas and crop growing belts move as climate change occurs e.g 50 years ago couldn’t grow pumpkins like you can now
Increased crop yields as warmer temperature allows more photosynthesis
World food production may decrease : e.g reduction of grain production in North America can have serious economic and political consequences
Increasing co2 in oceans decreases ph - coral reef exoskeleton made out of calcium carbonate which dissolves in acid
Co2 contributions
Production of farming tools
Production if insecticides herbicides etc
Farm machinery powered by fossil fuels
Transport of produce
Problems of green hous gasses how can be reduced
Co2 - decomposition of organic matter - improve soil quality by conservation tillage adding organic matter on topsoil, cover cropping e.g. Clover to cover soil to protect and improve it between crops
Crop rotation reduces pest numbers and mineral depletion
Methane- digestive activities of farm animals used in meat and dairy industry - reduce dietary intake of meat and dairy, high sugar grasses e,g rapeseed reduce the methan they release
Decomposition in wet soils e.g. Rice paddies - use rice varieties that grow in direr conditions , select varieties with higher yield , ammonium addition can favour non methane producing micro organisms in paddy fields in some condition
Nitric oxide and nitrous oxide - waterlogged and anaerobic soils - improve drainage and aerate soil
Low fluctuating water supply- low rainfall and high temperature - use drought resistant crops e.g in Kenya use millet
Raised sea levels - cultivated land in dungaree by salt water- salt resistant crops e.g salt tolerant potato
How human activities can improve circulation of nitrogen cycle
Ploughing fields:
Aerobic organisms - e.f free livi nitrogen fixating microorganism enhance formation of ammonium ions in soil
Nitrifying bacteria therefore enhances the conversion of ammonium into nitrates
Plant roots respire aerobic ally and genre rate atp which fuels active take up of minerals
Draining land allows air to enter soil reducing anaerobic conditions which favour detrifying bacteria loss of nitrate reduced
Artificial nitrogen fixation - habor process converts nitrogen to fertilisers essential to produce high volume of good quality food contai. Compounds e.g ammonium and nitrate
Large amounts of animal waste - brown manure improves soil structure so solid holds more water and nutrients encouraging microbial activity supple ting soils with minerals releases these compounds gradually
Slurry- liquid from water and manure- concrete slates are used instead of hay - injected into soil , alternative feed for pigs is being developed
Treated sewage sludge - bio solids, alternative to inorganic fertilisers
Planting fields - of legumes e.g less enhances nitrogen fixation when crop dies it is ploughed back into soil as green manure its blame is that it has high nitrogen content
Eutrophication
Why is it a problem
Is process of increasing mineral content as a result of nitrogen contesting fertilisers especially nitrates leaching from agricultural land
Excess nitrate in soil- reduced species diversity on grassland fertilisers increase the growth of grasses such as nettles which shade out smaller plants
In lakes and rivers the mineral ions normally accumulate until equilibrium is reached and addition to water is counterbalanced by rate at which they are removed this distrubs this and kills off organism
Eutrophication process
Algae blooms and water becomes green and light is unable to penetrate through to any depth
The plant in the deeper regions cannot photosynthesise and die there is a general decrease in animal diversity as they rely on plants for food and shelter
Short lived algae soon die and decompose using a lot of oxygen
The water in upper layers which are exposed to air become deoxygenated so oxygen requiring organism die
Anaorbic bacteria in water reduce nitrate to nitrite releasing gas
How to restrict nitrate concentration in water
Restrict amount of fertiliser applied to soil
Only apply fertiliser at time when crops are actively growing so readily used and not remained in soil to be leached away
Leave a strip of 10 m wide next too watercourse so doesn’t enter water if does over a prolonged period
Dig drainage ditches - eutrophication will take place here and protects natural watercourses
