6.5 - Ecosystems Flashcards
Ecosystem def
Any group of living organisms and non-living things occurring together and the interrelationships between them
Habitat def
The place where an organism lives
Population def
All of the organisms of one species who live in the same place, at the same time and breed together
Community def
All of the populations of different species who live in the same place at the same time and can interact with each other
Niche def
The role of an organism in the ecosystem
Abiotic factors def
Non-living factors in an ecosystem which can affect the distribution of organisms
Biotic factors def
The living organisms in an ecosystem
Biotic factors affecting ecosystems
- Producers
- Consumers
- Decomposers
What are cyclic changes?
- give some examples
These changes repeat themselves in a rhythm.
E.g. movement of tides and changes in a day length are cyclic
E.g. the way in which predator and prey species fluctuate is cyclic
What are directional changes?
Give examples
-These changes are not cyclic
- they go in one direction
- they tend to last longer than the lifetime of organisms within the ecosystem
- within such change, particular variables continue to increase or decrease
E.g. the deposition of silt in an estuary, or the erosion of coastline
What are unpredicatble/erratic changes?
- give examples
- disease/epidemic
- eutrophication
- natural disaster - hurricanes, drought/flood, tornado, storm, etc.
- may be human impact, e.g. climate change/global warming etc.
List abiotic factors
- weather in habitat
- light intensity in habitat
- temperature of habitat
- CO2 conc in habitat
- pH of habitat (CO2 decreases pH of water - more acidic, e.g. kills/bleaches coral)
- water/nutrient availability
- humididty levels in habitat
List biotic factors
- competition for food/nutrients
- competition for habitat
- ## disease
Biomass def
The dry mass of the organic material in an organism
What is a trophic level?
Each different level of the food chain
Why are plants difficult to digest?
- how does this effect energy transfer in the food chain?
- The cellulose cell wall in plants
- consumers lack cellulase
- biggest loss of energy is between producers and primary consumers
Why is there a loss of biomass (and energy) from food chains at each tropic level?
- some of the food not eaten, e.g. the bones
- respiration releases energy form organic molecules - e.g. glucose and materials, such as CO2 is lost
(Energy is also released as heat during respiration) - waste products and dead organisms contain biomass which will only be available to decomposers
How much energy is passed down the next trophic level in food chains
Only a small proportion of biomass (and energy) from the previous trophic level will be available at the next level
Why is it rare for food chains to go past around 4/5 trophic levels?
- energy is lost from food chain every trophic level
- limits length of food chains
- as top consumers are unable to eat enough of the animals at the level below to provide sufficient energy to live
Pyramids of numbers in a food chain info
- what does area of bar at each tropic level represent?
- reflects numbers in a food chain
- Area of bar is proportional to numbers of individuals in that tropic level
Why are pyramids of biomass more useful than pyramid of numbers (population sizes)
- pyramids of biomass are more useful to scientists
- take into account size of organisms and mass of biomass at each level
- give an indication of the energy contained at each trophic level
Problems with constructing pyramids of biomass
- very destructive - to habitats and ecosystem
- have to dehydrate dead organisms - difficult to do
Productivity def
The rate of production of new biomass
- the rate of energy flow through each trophic level
What does productivity reflect.
Reflects how much biomass/energy is available to organisms or a trophic level, per m2 per year (usually)
Primary productivity def
Total amount of energy fixed by photosysnthesis
Gross primary productivity def
Rate at which plants convert light energy into chemical energy through photosynthesis
NPP (Net Primary Productivity) def
Rate of production of new biomass available for heterotrophic consumption
- therefore the amount of energy available to them
Net Primary Productivity equation
Gross primary productivity - respiration (R)
Why is about 90% of sunlight not converted into biomass (net primary productivity)?
- reflected off plant/only certain wavelengths of light can be absorbed
- abosrbed by non-photosynthetic pigments, e.g. bark
- misses chlorophyll/chloroplasts
- some energy lost as heat that is used in respiration
What can be done to improve NPP (rate of new production of biomass)?
- make energy conversion more efficient
- reduce energy losses
Why farmers want to improve NPP (production of new biomass)
Increases crop yield
How would farmers improve NPP (rate of production of new biomass)
- ensure maximum rate of photosynthesis
- by ensuring limiting factors are controlled:
- light levels - grow with with light banks to give longer growing season
- temperature - greenhouse used to grow plants
- CO2 conc. - levels increased in greenhouse
- water levels - irrigation techniques and drought resistant plants
- nutrients - fertilisers, crop rotation with legumes (for nitrogen fixation)
- reduced yield of pests - use of pesticides, pest-resistant plants containing Bt gene
- competition from weeds - use herbicides to kill weeds
What happens when improving secondary productivity?
Improve rate of generation of biomass in heterotrophs
Why improve secondary productivity
Rate of energy transfer from producers to consumers very inefficient
- energy lost down trophic levels due to heat loss by repsiration, not eating all of plant (cellulose difficult to digest - no cellulase enzyme)
How to improve secondary productivity
- growth steroid treatment - illegal
- selective breeding
- antibiotics - less energy lost fighting pathogens
- battery farming - reduce movement so less energy used in respiration for energy; warm stable temperatures so less energy used in maintaining body temp.
Succession def
A natural directional change in species composition in an area over a period of time
How does succession occur?
- happens in a series of recognisable stages - called seral stages:
- where one community changes the conditions for the next, e.g. depth of soil
- primary succession begins with bare ground/rock
- which a pioneer species e.g. algae/moss, colonises first
- results in a climax community
How do pioneer species stabilise the environment?
- develops the soil, e.g. make it deeper
- cause an increase in availablity of water
- cause more minerals to be available (in soil), (some carry out nitrogen fixation)
- create habitats and provide shelter
- change soil pH
What happens as succession continues?
- development of deeper soil
- soil accumulates more minerals and is more fertile
- dominant species change
- plant species get larger
What is a climax community?
- final stage in succession
- community in equilibrium with environment
Describe two effects of the pioneer community on the habitat.
(2 Marks)
- idea of soil development - increase depth of soil
- increase in water availability
- increase in minerals or nutrients available
- increase organic material in habitat
- some pioneer species carry out nitrogen fixation
- photosynthesis (carbon fixation)
- create habitats/provide shelter
- AVP
(Using the infomation in the figure)
Explain what is meant by the term succession.
(4 Marks)
natural change in species composition (in an area) ;
ref to directional change ;
ref to named examples in the diagram (either species or category) ; over a period of time ;
a number of recognisable stages / seres / seral stages ;
one sere changes the conditions for the next ;
e.g. depth of soil increases / soil stabilisation ;
leads to a climax community ;
creation of niches ;
ref to nitrogen fixation ;
AVP ; e.g. pioneer species
outline two changes which occur between mid and late succession;.
(2 Marks)
- development of deeper soil
- soil becomes rich in nutrients and mineral/is more fertile
- dominant species change
- plant species get larger/increase in biomass
Decomposition def
The conversion of organic matter to inorganic matter
Draw and outline the carbon cycle, and the different processes occurring in it (actually draw it!)
Decomposer def
An organism that decomposes organic material - converts organic material into inorganic material
Nitrogen cycle def
Converting nitrogen into compounds used for plants (nitrates/ammonium ions)
What does the haber process produce that is useful for plants
Ammonia
What does NPK stand for?
Nitrates
Phosphate
Potassium
How is eutrophication caused?
Human fertiliser leaks into water
Causes algae bloom
Term when there is no oxygen in water
Anoxic
What is the effect of eutrophication in lakes
Layer of algae grows on top of water Prevents sunlight reaching plants underwater Plants underwater die No oxygen released into water Water becomes anoxic Fish cannot survive as no oxygen in lake Fish can't feed on plants, etc Death of fish causes H2S to be released into water Can cause formation of sulfuric acid in water Cause acidic conditions Causes more death of fish, etc. Positive feedback loop
Why is nitrogen needed for plants
Used in synthesis of:
Amino acids - Proteins
Nucleic acids
Sources of nitrogen for plants
Ammonium ions
Ammonia - haber process
Nitrate ions
Nitrogen gas in atmosphere
4 bacteria that are used for nitrogen fixation
What do each of them do
Aztobacter - ammonification
Ammonification
Rhizobium, associated with legumes
Mutuality with plants
Nitrosomonas - nitrifying bacteria
Oxidise ammonium ions to nitrites in soil
Oxidises nitrites to nitrates
Pseudomonas - dentrifying bacteria
Anaerobically reduces nitrates and releases nitrogen gas
What do bacteria do in nitrogen fixation
Convert nitrogen into nitrates or ammonia, a form that plants can use
How does eutrophication occur?
Occurs when nitrates leech into rivers etc.
What does eutrophication cause
Cause algal bloom (nitrates allow rapid protein production and growth)
Blocks light for photosynthetic plants below algae
Plants die and are decomposed
Decomposed use up O2 in water
Aquatic life dies as no O2 for respiration- anoxic
What is crop rotation?
Different crops grown in the field each year depending on conditions and weather
Some years nothing planted
Crop rotation info
- Differentcropshavedifferentnitraterequirements
- Eachyearnitratesnotbeingremovedatthesamerate
- Inyearofnocropsnonutrientsremovedandso buildbackup
- Uselegumesinrotationtoputammoniumions
Suggest three ways that farmers can maximise the efficiency of the transfer of energy up food chains from primary consumers to humans.
(3 Marks)
Battery farms:
- keep animals indoors
- reduce animal movement
- feed animals high protein food
- vaccination/routine antibiotics for animals - to prevent energy used to fight against pathogens/bacteria
- selective breeding - e.g, higher yield of meat in animals/higher milk yield in cows
- slaughter just before mature/full size
Producer def
Convert light energy to chemical energy via photosynthesis
Consumer def
Feeds on and derives energy from other organisms - e.g. plants or animals
Tropic level def
Level/position in the food chain
Nitrogen cycle process
List the processes which contribute to the formation of humus (top layer of soil) in a meadow.
(2 Marks)
Decomposition
Death of plant/leaf loss
Excretion/urination, etc.
Defaecation/egestion (?)
Bacteria used in nitrification
Nitrosomonas -
Nitrobacter -
