What are some examples of ecosystems of different sizes?
-rock pool
-a playing field
-a large tree
What are biotic factors and what are some examples of them?
Biotic factor- environmental factors associated with living organisms in an ecosystem that affect each other
E.g.
-predation
-disease
-Competition (inter-specific) for space, food, water, light etc.
Cooperation between organisms (can be between the same species or different species)
What are abiotic factors and what are some examples of them?
-non-living components of an ecosystem that affect other living organisms
E.g.
-availability of water
-temperature
-humidity
-pH
-salinity
What is a trophic level?
The level at which an organism feeds in a food chain
What is the biomass of an organism?
The mass of living material of the organism or tissue
The chemical energy that is stored within the organism or tissue
What is dry mass?
The dry mass is the mass of the organism or tissue after all the water has been removed
The dry mass of a sample can be used to calculate the biomass of a total population of organisms or of a particular area
Why do photosynthetic plants not absorb a large proportion of the Sun’s energy?
Light passes through leaves or is reflected away
Light is a mixture of wavelengths, and only certain wavelengths stimulate photosynthesis
Why is biomass lost between trophic levels?
-respiration is carried out this releases energy
-primary consumers do not eat every part of the plant and they do not digest every part (e.g. cellulose)
-biomass is lost from a food chain in dead organisms and waste material, which is then only available to decomposers
How can you calculate the efficiency of biomass transfers between trophic levels?
Efficiency of transfer = (biomass transferred /by biomass intake)x 100
How can farmers maximise the biomass of plants?
Providing artificial light in greenhouses on overcast days
Optimising planting distances between crops
Irrigation to maximise growth in dry weather
Use of fertilisers
Selective breeding for fast growth
Use of fungicides/pesticides
Fencing to exclude grazers
Ploughing and herbicides to kill weeds
Plant crops that store energy in edible form e.g. seeds, fruit, tubers
How can livestock farmers manipulate energy transfer of livestock?
Use of good quality feeds / food supplements
Use antibiotics and vaccines to reduce disease
Control predation with fencing or with indoor animal husbandry
Reduce competition for grazing e.g. rabbits, deer
Indoor husbandry to reduce energy loss from movement or from getting cold outside
Describe the nitrogen cycle
NITROGEN FIXATION
-nitrogen is very unreactive plants need a supply of fixed nitrogen such as ammonium ions (NH4+) or nitrate ions (NO3-) nitrogen fixation can occur when lighting strikes or through the Haber process. Nitrogen fixing bacteria supply most of the fixed nitrogen. Nitrogen-fixing bacteria (Azotobacter-found in soil, free living and Rhizobium-live inside root nodules of leguminous plants, this is a mutualistic relationship) are able to convert gaseous nitrogen into ammonium ions (NH4+)
AMMONIFICATION AND NITRIFICATION
-Nitrosomonas bacteria oxidise AMMONIUM IONS to nitrites and Nitrobacter oxidise nitrites to nitrates
->these reactions only happen in well aerated soil
->nitrates can be absorbed from the soil by plants and used to make nucleotide bases and amino acids
->proteins, urea and DNA in dead matter are decomposed by saprobionts, bacteria and fungi that can digest waste extra cellularly which return ammonium ions to the soil
Denitrification- other bacteria convert nitrates back to nitrogen gas happens only in anaerobic conditions
How can biomass be measured?
-mass of carbon or dry mass of tissue per given area
Describe the carbon cycle
DECAY AND DECOMPOSITION
Dead plants and animals are fed upon by detritivores and decayed by saprophytes
Releasing carbon into the surroundings
Supplying carbon to the detritivores
Supplying carbon to the saprophytes
Waste matter such as faeces and urine is used by decaying saprobionts
Such processes can release CO2 back into the air
RESPIRATION
-CO2 is released in the link reaction and the Krebs cycle of aerobic respiration
-anaerobic respiration also releases CO2
PHOTOSYNTHESIS
-removes carbon from the atmosphere
The Calvin cycle is where CO2 is fixed, by the enzyme Rubisco, which carboxylates RuBP
Terrestrial plants use gaseous CO2 directly from the air
Aquatic organisms use CO2 dissolved in water
SEDIMENTATION
Plants that die are not fully decomposed by saprobionts; their bodies form layers of sediment that can accumulate over millions of years, locking carbon into the ground
This sediment is a store of energy and can form fossil fuels like peat and coal
Aquatic organisms that die also form sediments on the sea bed; these can go on to form other fossil fuels like oil and gas
BURNING FOSSIL FUELS
-releases CO2
What is a climax community?
The final stable community that exists after the process of succession has occurred
What is deflected succession?
Happens when succession is stopped or interfered with
Such as by grazing, when a lawn is mowed
During succession, the _________ _______ (i.e. the living factors) and the ________ ______ (i.e. the non-living factors) change over time
Biotic conditions
Abiotic conditions
How can new inhabited land be created?
The magma from erupting volcanoes cools and often leads to the formation of new rock surfaces or even new rocky islands in the sea
Another way new land can be exposed is by sea-level dropping or the drying up of a lake, leaving areas of bare rock
What are the stages of primary succession?
Firstly, seeds and spores that are carried by the wind land on the exposed rock and begin to grow
These first species to colonise the new land (often moss and lichens) are known as pioneer species
As these pioneer species die and decompose, the dead organic matter (humus) forms a basic soil
Seeds of small plants and grasses, sometimes also carried in the wind or sometimes transported other ways (e.g. in bird faeces) land on this basic soil and begin to grow (these smaller plants are adapted to survive in shallow, relatively nutrient-poor soils)
As these small plants and shrubs die and decompose, the new soil becomes deeper and more nutrient-rich
The roots of these small plants and shrubs also form a network that helps to hold the soil in place and prevent it from being washed away
Larger plants and shrubs, as well as small trees, that require deeper, more nutrient-rich soil, can now begin to grow
These larger plants and small trees also require more water, which can be stored in deeper soils
Finally, the soil is sufficiently deep, contains enough nutrients and can hold enough water to support the growth of large trees
These final species to colonise the new land become the dominant species of the now relatively complex ecosystem
The final community formed, containing all the different plant and animal species that have now colonised the new land, is known as the climax community
What are some examples of pioneer species?
-marram grass- deep roots can tolerate salty environment e.g. sand dunes
-moss
-lichens
How does the environment change during succession?
At each stage in succession, there are certain species that gradually change the local environment so that it becomes more suitable for other species (with different adaptations) that have not yet colonised the new land
For example, pioneer species change the abiotic conditions so that they are less hostile to new colonising species
Often, these new colonising species then change the environment in such a way that it becomes less suitable for the previous species
E.g. lichens (pioneer species) grow on bare rock help to break apart top surface of the rock, the fragmented rock and humus are broken down and form a basic soil. Mosses can grow and result in a formation of a thin soil layer that cover newly formed rock. Lichens cannot grow on soil, so they now disappear from the ecosystem, the new species that arrived after the lichens have changed the environment in such a way that it becomes less suitable for the lichens
as the soil deepens further and trees are able to grow, they may then out-compete certain shrubs and other smaller plant species, which may no longer be able to grow beneath the trees due to a lack of light
How can succcession be prevented?
-grazing animals
-managed burning, to allow the shrubs and trees to burn away
What is the distribution of a species?
describes how it is spread throughout the ecosystem
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Cell Structure 2.168
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Biological Molecules 2.272
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Biological Membranes 2.553
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Cell Division,cell Diversity And Cellular Organisation 2.681
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Nucleotides And Nucleic Acids 2.341
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Enzymes 2.427
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Communicable Diseases 4.192
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Exchange Surfaces And Breathing- 3.144
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Biodiversity-4.256
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Cellular Control-6.152
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Patterns Of Inheritance-6.277
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Transport In Animals 3.281
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Transport In Plants 3.345
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Classification And Evolution 4.346
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Manipulating Genomes 6.336
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Excretion As An Example Of Homeostatic Control 5.260
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Cloning And Biotechnology 6.440
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5.6-photosynthesis50
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Respiration-5.731
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Communication And Homeostasis 5.116
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Plant And Animal Responses 5.185
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Math Skills16
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Hormonal Communication 5.435
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Neuronal Communication 5.349
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Ecosystems 6.531
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Populations And Sustainability18
