Unit 3.5 - Population and Ecosystems Flashcards
Habitat
A place where an organism lives
Community
All the different species in a habitat
Environment
The abiotic factors in a habitat
Population
The number of individuals of a particular species in a particular time and place, able to interbreed
Species
Organisms that can interbreed to produce fertile offspring
Ecosystem
All the biotic and abiotic factors in a region and how they interact
Niche
The exact role an organism plays in a habitat. Can be thought of as an “n-dimensional hyper volume”
Why is a niche known as an n-dimensional hyper volume?
With all factors acting as a dimension, it creates a niche that only one species can fill
Fundamental niche
The species could occupy this niche
Realised niche
Given up what is already within another species niche
Competitive exclusion principle
Two species occupying the same niche can’t coexist at the same time in the same habitat
What does the competitive exclusion principle lead to?
No two niches are the same
Complete competitors can’t exist, since the niche would be taken over
Why can’t complete competitors exist?
The niche would be taken over, and no two niches are the same
Are P.Aurelia and P.candatum predator and pray?
No, they compete for the same food source
Graphs of P.Aurelia and P.candatum individually
One-step grown curves (S-shaped)
Another word for S-shaped graphs
One-step growth curves
What happens when P.Aurelia and P.candatum are grown together and why?
P.Aurelia is outcompeting, so P.candatum is pushed to of the niche, and the population density of P.Aurelia increases whilst the population density of P.candatum decreases
What are P.Aurelia and P.caudatum examples of?
Paramecium
Factors affecting population size
Birth rare
Death rate
Immigration
Emigration
Birth rate
The number of new individuals produced by sexual or asexual reproduction per unit time
Death rate
The number of individuals dying per unit time
Immigration
New individuals joining a population
Emigration
Individuals leaving a population
What phase do we need to include in the definitions for birth rate and death rate and why?
“Per unit time” since they’re rates
An increase in what causes an increase in the population size?
Birth rate and immigration
An increase in what causes a decrease in population size?
Death rate and emigration
How can we differentiate between species in this unit?
Depending on the way they colonise an area
Describe fugitive species
Cannot tolerate competition
To increase in numbers —> reproduce rapidly and have effective dispersal (spreading) mechanisms
Are able to invade new environments rapidly
E.g - algae and weeds
Examples of fugitive species
Algae and weeds
Species that cannot tolerate competition
Fugitive species
Equilibrium species
Control their population by competition within a stable habitat
Usual pattern of growth of equilibrium species
Sigmoid (s-shaped) curve called a one step growth curve
What type of species follow a one-step growth curve pattern of growth?
Equilibrium species
One-step growth curve
Sigmoid (s-shaped) curve
Examples of equilibrium species
Bacteria and rabbits
What do we need to do when describing, for example, rabbit and bacteria populations?
Use the correct terms for the specific scenario
Bacteria —> “cell division”, “cell death”
Rabbits —> “rate of birth”, “rate of death”
What happens during the exponential (log) phase?
The number of cells double per unit time
What fact do we use for any calculations on the number of cells produced during the exponential phase?
The fact that the number of cells double per unit time during the exponential (log) phase
How do we achieve the full amount of cells during the exponential (log) phase?
Would need…
Ideal conditions
To assume that none die
A huge amount of nutrients
Biotic factors
Factors that are living parts of the environment of an organism
Examples of biotic factors
Predation, parasitism, disease, intra-specific and inter-specific competition
What are intra-specific and inter-specific competition examples of?
Biotic factors
Intra-specific competition
During the stationary phase of the population growth:
Competition between individuals of the same species for the same food
(e.g - just rabbits for grass)
Inter-specific competition
Other species competing for the same food course (e.g - rabbits and sheep for grass)
Abiotic factors
Are some part of the organisms environment that is non-living
Examples of abiotic factors
Air temperature, oxygen availability, rainfall, light availability
What do density dependent factors tend to be?
Biotic factors
What do density independent factors tend to be?
Abiotic factors
Density dependent factors
Has an increasing effect on the rate of population growth with increasing population density
Explain why bacteria is a entity dependent factor
Disease has a greater effect on a larger population
Examples of density dependent factors
Predators, parasites, pathogens
Competition: food, mates, nesting sites
Density independent factors
Have the same effect on the rate of population growth regardless of population density
Examples of density independent factors
Wild fires, floods, climate change, sunlight (energy), temperature, rainfall
Carrying capacity
The maximum population size of a species that an environment can sustain
What’s important to notice about the carrying capacity definition?
Not have, but sustain over an extended period of time
What can carrying capacity be compared to?
The “stationary phase” for bacteria is the carrying capacity of a habitat in nature
What happens around the carrying capacity?
There’s fluctuation in the number of the population over time.
Numbers fluctuate about the carrying capacity.
Where do population numbers fluctuate about?
The carrying capacity
When would the carrying capacity of an environment decrease and why?
When a predator or parasite or disease is present
The environment can’t sustain the same numbers of the organism
What does introducing a predator, parasite or disease to an environment do to the carrying capacity and why?
Carrying capacity decreases
The environment can’t sustain the same numbers of the organism
Environmental resistance
Refers to environmental factors that slow down population growth
What may environmental resistance be?
Biotic or abiotic
Example of environmental resistance + why
A predator
Increases the environmental resistance = population lowers
Describe the graph comparing prey and predators populations and explain when this happens
If a predator is depending on this prey as its food source, the predator curve “lags” behind the prey curve
Explain why the predator curve lags behind the prey curve on the graph comparing the two
-predator number are low = less pressure on prey = numbers increase
-more prey for predators = numbers increase
-puts pressure on prey population in turn = more prey eaten by predators
-less food for the predator = numbers decrease
And repeat
Famous example of a predator/prey relationship
Lynx and snowshoe hare
Describe the snowshoe hare over the seasons
Brown in summer
White in winter
How much data needs to be collected to make a graph to compare prey and predators populations?
Decades of data
Describe the predator/prey relationship between the lung and the snowshoe hare
-when the prey population is large, intraspecific competition in the predator population is low =population grows
-this places more pressure on the prey population, which declines as a consequence
- this leads to greater intraspecific competition for the predators and their population declines, allowing the prey population to recover
-the cycle continues
What are the lynx and snowshoe hare essentially achieving with each other and how?
Sustaining each other over time
Maintaining an equilibrium between them
When is intraspecific competition in a predator low?
When the prey population is large
When is the intraspecific competition of predators large?
When the prey population is low
What happens to the competition of predators when the prey population is large?
Intraspecific competition is low
What happens to the competition of predators when the prey population is low?
Intraspecific competition is high
Name an animal population counting method
Capture, mark, re-capture
What is the capture, mark, re-capture method used for?
To estimate the size of populations of motile animals (moving animals)
Capture, mark, re-capture method
- An initial sample of the population in question is captured
- These individuals are then marked and released back into the wild, and the number caught is recorded
(The mark must be all weather resistant) - These marked individuals are released and are left for a period of time to allow them to randomly disperse throughout the habitat
- Then, a second sample is captured
- The total number captured in the second sample, and the number recaptured with the marking is recorded
- The size of the population is then estimated on the principle that the proportion marked in the second sample equals the portion of marked individuals in the population as a whole
How do we make the capture, mark, re-capture method more reliable?
Repeat
What does repeating an experiment do?
Makes it more reliable
Lincoln index equation and meanings
N = n1 x n2/m
N = total population size of animal of interest in sthe study ite
n1 = number of animals captured on the first day
n2 = number of animals captured on the second day
m = number of marked animals in the sample recaptured on the second day
Which principle does the capture, mark, re-capture method rely on?
That the proportion marked in the second sample equals the proportion of marked individuals in the population as a whole
Assumptions made using the capture, mark, re-capture method
- The organisms that have been marked mix randomly within the population
- Enough time is given for the marked individuals to mix randomly with the rest of the population
- The movement of the population as a whole is limited geographically
- Organisms are spread evenly within its geographical range
- Changes in population size due to birth, death, immigration and emigration are minimal
- Marking dos not make them more susceptible to predators or harm them in any way or make them more likely to be recaptured
How do we do the capture, mark, re-capture method with particularly big species?
Generally use features they already have to identify them instead of marking them
Study of the energy flow through ecosystems
Energetics
Energetics
Study of the energy flow through ecosystems
Ecosystem
A characteristic community of interdependent species and their habitat
What can an ecosystem be described as?
Dynamic (changes over time)
What is an ecosystem compromised of?
Living (biotic) and non-living (abiotic) elements
What does an arrow in a food web represent?
“Is eaten by”, or more instantly, the transfer of energy
What do food webs prove?
That ecological communities are dependent on each other for food
Energy source of most ecosystems
The sun
What do some ecosystems use as their energy source instead of the sun?
Chemicals
Name an ecosystem that uses chemicals instead of the sun as its energy source and why
Thermal vents, no sunlight
What type of organisms use chemicals as their energy source and for which process is this?
Used by chemosynthetic organisms for chemosynthesis
What does each food web start with?
Autotrophs (the producers)
What do autotrophs do?
Covert light energy into chemical energy to produce complex organic compounds using carbon from simple substances such as CO2
What does each food chain rely upon?
Autotrophs (photosynthetic organisms)
What is the energy produced by autotrophs then available for?
Heterotrophs
What do heterotrophs do?
Cannot procure their own complex organic molecules
Feed on autotrophs and each other
What is the final stage of a food chain?
The apex predator
What is the maximum number of steps from autotrophs to heterotrophs in a food chain??
About 6 steps
Why is the maximum number of steps from autotrophs to heterotrophs in a food chain never more than about 6 steps?
Energy losses when going from one stage to the next
The chain is unable to maintain another level beyond the apex predator
What are the names of the different stages in a food chain?
Tropic levels
Names for the organisms in a food chain in order
Producer
Primary consumer
Secondary consumer
Tertiary consumer
(e.t.c)
Producers trophic level
1
Producers
Autotrophic organisms (plants and algae) which absorb light energy to covert simple inorganic compounds into more complex organic compounds such as carbohydrates
Consumers
Heterotrophic organisms which cannot fix carbon from inorganic compounds like the producers do —> they must ingest it or absorb organic carbon from other organisms
Herbivores trophic level
2
Herbivores
Primary consumers, animals which feed on organic matter produced by the producers
Carnivores
Feed on other animals at lower trophic levels
Trophic level
An organism’s position within a food chain (steps in the food chain)
Detritivores examples
Earthworms, woodlice, maggots
Decomposers examples
Bacteria, fungi
Detritivores
Feed on dead organic matter (e.g - plants and fungi)
Decomposers
Break down organic compounds into simpler inorganic compounds which are soluble and can be absorbed by plant roots
Explain which elements can become part of the Decomposer system in a simple foo chain
Some grass dies, is available for detritivores and decomposers
Animal waste becomes part of the decomposers system
Trophic efficiency
The percentage of energy available at one trophic level which is transferred to the next trophic level to form new biomass
Describe the energy that’s passed from one trophic level to the next in a food chain
Only a small % of energy
Why is it only a mall % of energy that’s available to be passed on from one trophic level to the next?
Most of it is lost due to heat, waste products and uneaten parts
Ways energy is lost at each trophic level
Heat
Waste products
Uneaten parts
Name the different ways or representing the energy flow in food chains
Graphs
Pyramids
Energy flow diagrams
Why is the trophic efficiency so low between trophic levels 1 and 2 compared to between trophic levels 2 and 3?
Plants contain a lot of indigestible material
Name some indigestible materials in plants
Lignin in wood
Cellulose in cell walls
What do animals do with the parts of a plant that they can’t get the nutrients from?
Pass them through their systems, unabsorbed
Compare the % indigestible material in an animal vs a plant
The % of indigestible material in an animal is much lower than in a plant
Name some indigestible parts of an animal
Fur, nails
Which type of Pyramid to represent energy flow is worst?
Pyramid of numbers
Why are pyramids of numbers misleading?
Although 1 oak tree (for example) is shown, the amount of energy in it is massive, but it isn’t used much here. So, these pyramids don’t represent energy flow very well.
Biomass
The mass of biological/living material at each trophic level
What does biomass exclude and why?
Water since it can vary a lot in different organisms
How do we remove water to measure biomass and what does this do?
Dry them
Gives us more accurate results
What the most accurate pyramids to represent energy flow in a food chain?
Pyramid of energy
What does a pyramid of energy show?
The energy transferred from one trophic level to the next, per unit area or volume per unit time
What do energy flow diagrams show?
The energy harvested by the plant and used in photosynthesis to produce other molecules
Photosynthetic efficiency (PE)
A measure of the ability of a plant to trap light energy
What does photosynthetic efficiency depend on?
Light intensity and temperature
Photosynthetic efficiency equation
Quantity of light energy incorporated into product/quantity of light energy falling on the plant
X100
Products of photosynthesis
Glucose, carbohydrates
Gross primary productivity (GPP)
The rate at which products such as glucose are formed.
Or
The rate of production of chemical energy in organic molecules by photosynthesis in a given area, in a given time, measured in kJm^-2y-1
What is a large proportion of GPP used up in?
Respiration by the plant
A large proportion of what is used up in respiration by the plant?
Gross primary productivity (GPP)
Net primary productivity (NPP)
The quantity of GPP that is left over after respiration by the plant is accounted for. This represents the potential food available for the primary consumers.
= the energy in the plants biomass
Examples of potential food for primary consumers represented by the net primary productivity (NPP)
Fats
Glucose
proteins
Net primary productivity (NPP) equation
NPP = GPP - respiration
What does GPP equal?
NPP + respiration
Describe the value of gross primary production
Very small
Why is gross primary production such a small value?
- Only some wavelengths of light are absorbed by the leaf - some light will be of the wrong wavelength
- Lots of it is reflected off the leaf surface
- Lots will be transmitted through the leaf without hitting any photosynthetic parts
How are plants most easily sampled?
Using a quadrat
Quadrat
Square frames that are placed on the ground to provide a small, standard area for investigation
How do quadrats come?
In a variety of sizes (10cm, 50cm, 100cm)
What would 10cm quadrats be useful for?
Lichens on a tree trunk
What would a 50cm quadrat be useful for?
Small plants and grassland
What would 100cm quadrats be useful for?
In the wood
How may quadrats be subdivided?
Into 25 or 100 smaller squares
What is the smallest quadrat possible? Describe this
Point quadrat (pin quadrat)
A needle with the point of the needle being the actual tiny quadrat
Describe how we would find the best size of frame quadrat for a particular habitat
Need to do a preliminary experiment
“Nesting” different sized quadrats in the area to be studied and counting the number of species found
From the species-area graph, we can choose a quadrat size that is likely to catch all the species but without wasting unnecessary effort
2 main methods of sampling
Random
Systematic
What type of sampling do we do in an area where abiotic variables are uniform?
Random sampling
Example of an area where abiotic variables are uniform
An open field
What is used when random sampling in an open field is done?
A representative of the whole area, which is an “open frame quadrat”, a square frame with sides of e.g 0.5m, giving an area of 25m^2
Different ways in which a measurement for each species in a quadrat can be recorded after identifying the plants in the frame
A direct count
Percentage cover
A value using the ACFOR system
Explain the stages of setting up coordinates for sampling
- In a uniform grassland, set up a pair of 10m long axes at right angles to each other
- Use random numbers (e.g - from a random number generator) to find coordinates for the quadrat
- If it is difficult to count individual plants, estimate the percentage area cover
- Take readings at 10 pairs of random coordinates and calculate a mean for each species
- Compare with an area with different abiotic factors
How do we decide on exact coordinates of a quadrat?
Say our random numbers are 63 and 81 on a 10x10m axes, the coordinates are where the lines from 6.3m and 8.1m along the axes intersect
How can we ensure consistency with our quadrats for random sampling?
Always place the bottom left hand corner of the quadrat at the coordinate
Purpose of using a quadrat
Make sure that the sample size taken is constant
Purpose of sampling at random
To eliminate bias from our results for more reliable results
How can we get more reliable results whilst sampling?
Sample at Random
Take more samples
What does taking more samples do to our results?
Increases reliability
What do we want to ensure when doing random sampling?
Ensure that most factors are consistent between the 2 areas, With maybe 1 different abiotic factor to compare (e.g - same light intensities, different temperatures)
What do we also need to take into account when doing random samples?
The seasons
Ensure that the sampling for both areas is done at the same time of year
What are we assuming when doing sampling at random?
That the plants are evenly distributed in the habitat
What must be true for plants to be evenly distributed in a habitat?
The environmental conditions are constant, with the same environmental gradient
Word for environmental conditions being constant
Same environmental gradient
What causes an environmental gradient?
A change in abiotic factor
Why does a change in abiotic factor cause in an environment?
An environmental gradient
When can’t we use random sampling?
When there’s a change in abiotic factor - an environmental gradient
What type of sampling do we do in an area where there’s a change in an environmental factor?
Systematic sampling
What is an environmental gradient? Give an example
A distinct change in an abiotic factor such as light intensity
Give an example of light intensity changing in an environment
Under the shade of a tree of the edge of a woodland
What is a transect?
A line along the environmental gradient
What is used during systematic sampling on an environmental gradient?
A transect
When is a transect used?
during systematic sampling on an environmental gradient
How do you use a line transect?
Run a 20m tape measure into the wood and identify the plants touching the tape every 2m
Why is using a transect systematic sampling?
We take a sample every 2m, which is in regular intervals
How do we use a belt transect?
Place a 0.5m square quadrat every metre along the tape measure and estimate the density, percentage frequency or percentage area cover
Two types of transect to use
Line
Belt
What do we need to make sure we do when doing systematic sampling?
Make sure that the sampling area takes in all of the environmental conditions
Example of a belt transect
Slope into water
Why can’t we take a mean with systematic sampling?
This would assume that everything is the same all the transect
What do we do instead of calculating a mean with systematic sampling?
Use a kite diagram
Kite diagram
A visual representation of distribution
What do kite diagrams show?
The effect of an environmental gradient
How do we draw kite diagrams?
Each species have their own axes
X-axis = distance along transect
Y-axis = number of plants every 2m
How would we show 10 plants on a kite diagram?
5 above, 5 below
Succession
The change in structure and species composition of a community over time
What does each stage of succession do?
Paves the way for the next stage
Seral stages
The different stages in a succession when particular communities dominate
Name for the different stages in a succession when particular communities dominate
Seral stages
What happens to communities over time and why?
Change in response to changes in the environment
When is a change in a community referred to as succession?
When changes are brought about by the species in the environment
What does primary succession start from?
A new rock and no soil
How could a new rock have formed for primary succession?
-after a volcanic eruption (lava solidifying and cooling)
-after the ice age (thick coating of ice retreated to give bear rock)
Pioneer species
The first species to colonise a new environment (e.g - bare rock)
The first species to colonise a new environment
Pioneer species
What are pioneer species capable of doing? Why?
Growing where there’s no soil
No need for them to anchor roots in soil to absorb minerals
What are lichens?
A group of symbiotic organisms (mutualistic symbiotic relationship between a fungus and an algae)
What does a mutualistic symbiotic relationship between an algae and a fungus form?
Lichens
What can lichens do?
Colonise bare rock
Describe fungus
Heterotrophic
Describe algae
Autotrophic and photosynthetic
How can lichens colonise bare rock?
The fungus is able to absorb minerals from the rock
The alga can photosynthesise to produce sugars
How does fungi provide an ideal environment for algae to live in?
Anchor themselves to the rock
Form a sense network of hyphae which can trap moisture
How do fungus and algae have a mutualistic relationship in lichens?
Fungus is able to absorb minerals from the rock
The algae can photosynthesise to produce sugars
Fungi provides an ideal environment for the algae to live in
How do mosses form?
Over time, bits of lichen die off and form a thin soil for mosses to grow
What forms when bits of lichen die off? How?
Mosses
Form a thin soil
Describe mosses
Small plants
Photosynthetic
Spread laterally over the surface of the ground
Grow best when there’s no taller plants to compete for sunlight
How does a thin soil for grasses to grow come about?
Over time, more dead material from the lichens and mosses accumulate to form the thin soil
How does a thin soil form for grasses and ferns to become established in?
Dead organic material from lichens and mosses collect in fissures in the rock surface
Together with minerals form the weathered rock, forms a thin soil
How can larger plants grow in the soil formed during succession?
After several years, the soil becomes deeper and larger plants can grow in it
Examples of larger plants that can grow in deeper soil formed during succession
Gorse, broom or heather
What does what grows in the soil formed during succession depend on?
The climate
What will eventually become established in the thickening soil formed during succession? Give an example
Small trees
Hawthorn
Climax community
Where the process of succession stops and there’s no further stages
When is a climax community established?
After years of the soil thickening
Trees that lose their leaves in winter
Deciduous trees
Deciduous trees
Trees that lose their leaves in winter
Climax community in the UK
Deciduous trees (lose their leaves in winter)
Climax community of the arctic circle
Fir trees
Climax community of the tropics
Tropical rainforest
What does secondary succession begin from?
Bare soil
How could the bare soil for secondary succession be exposed?
after a wildfire
When is the climax community achieved fastest - during primary or secondary succession?
Secondary
What is there no need for in secondary succession?
The pioneer species
Why is the climax community achieved faster during secondary succession compared to primary succession?
The soil is already present and it may contain viable bulbs, seeds and spores
No need for pioneer species
What does a wildfire cause?
Loss of climax community down to bare soil
How are seeds introduced to an area for secondary succession?
Blow in
Carried by animals
What can human activity do about a climax community?
Prevent it from being achieved
Examples of human activity preventing a climax community from being achieved
Grazing sheep
Heather moorland management by controlled burning (breed grouse for shooting)
Farming of land
Deforestation and soil erosion (roots will decompose)
What does a greater species diversity lead to?
Greater stability
Give some examples of what greater biodiversity offers
More food resources
More habitats
More resilience in face of environmental change
Describe the relationship between biodiversity and productivity
Productivity increases with biodiversity until just before the climax community, where it drops
Describe productivity in the climax community and explain this
Low
Trees don’t need to grow anymore once they’re mature
What is happening when both productivity and biodiversity are increasing?
New material is formed all of the time
What do plants need to grow?
CO2
Sunlight
Water
What can plants make with CO2, sunlight and water?
Carbohydrates
What do plants need to make important compounds for growth?
Minerals
One of the minerals plants need for growth
Nitrogen
5 different processes in the nitrogen cycle
Nitrogen fixation
Assimilation
Ammonification
Nitrification
Denitrification
Why do plants require nitrogen?
For the synthesis of amino acids and nucleic acids (DNA, DNA, ATP AND NADP)
Name all of the forms in which nitrogen is found in nature
Ammonia
Ammonium ions
Nitrite
Nitrate
Amino acids
Nucleic axisa
Urea and uric acid
ATP and ADP
free (gaseous) nitrogen
When is nitrogen found as ammonia or ammonium ions?
Decomposition/decay
In what form is nitrogen in soil?
Nitrate ions
What is able to happen to the nitrate ions in soil?
Can be assimilated into its different compounds
(Amino acids, nucleic acids (DNA, RNA, ATP, NADP))
What happens during nitrogen fixation?
70% of air is nitrogen, but plants can’t absorb this directly
Some bacteria can, which are free in the soil and in plant roots
These fix nitrogen in the atmosphere
What does nitrogen fixation replace?
Nitrates lost in denitrification
Describe the process of ammonification
Plants use nitrates
When they die, this goes back into the soil
Nitrogen is broken down by decomposers
Nitrogen released into the soil in the form of ammonium ions
Ammonium ions are also formed from animal wastes
Why is nitrogen sometimes in the form of ammonium ions?
Nitrogen released into the soil in the form of ammonium ions (nitrogen from dead plants broken down by decomposers)
Ammonium ions are also formed from animal wastes
Name 2 nitrogen fixing bacteria
Rhizobium
Azotobacter
Rhizobium
Mutualistic bacteria which are found in the root nodules of leguminous plants
Azotobacter
Free-living soil bacteria
Where is rhizobium found?
In the root nodules of leguminous plants
Where does Azotobacter live?
Free-living soil bacteria
Leguminous plants + examples
Large family of plants
Beans, peas, clover
What do leguminous plants have?
Nodules in roots that contain nitrogen fixing bacteria
What’s in the nodules in the roots of leguminous plants?
Nitrogen fixing bacteria
What do leguminous plants have a mutualistic relationship with?
Nitrogen fixing bacteria
Describe the relationship between nitrogen fixing bacteria and leguminous plants
Mutualistic
Equation for nitrogen fixation
N2 + 12ATP + hydrogen from water—> 2NH3 + 12ADP + 12PI
Nitrogenase
Enzyme involved in nitrogen fixation
Nitrogenase
Describe the process of nitrogen fixation
Very effective process
What’s the issue with the process of nitrogen fixation?
It uses a lot of energy
What’s proof that nitrogen fixation uses a lot of energy?
It takes 12ATP to provide sufficient energy
Why does nitrogen fixation require so much energy (12ATP’s)?
To provide sufficient energy to break the strong triple covalent bond between the two nitrogen atoms of N2 gas
Type o f bond between the two nitrogen atoms in N2 gas
Triple covalent bond
What colour are the roots of clover root nodules and why?
Pink
Leghaemoglobin
Describe leghaemoglobin
Protein similar to haemoglobin, found in the roots of clover root nodules
What is inhibited by oxygen in the nitrogen cycle?
The process of fixing nitrogen in plant roots
What is the process of fixing nitrogen in plant roots inhibited by?
Oxygen
What does leghaemoglobin do in the roots of root nodules?
Buries the O2 in the root nodules, preventing it from interfering
What is done about the fact that the process of fixing nitrogen in plant roots is inhibited by oxygen?
Leghaemoglobin buries the O2 in the root nodules, preventing it form interfering
What type of relationship is there between the nitrogen fixing bacteria and the plant?
Mutualistic
Why is there a mutualistic relationship between the nitrogen fixing bacteria and the plant?
Bacteria —> get an ideal environment and sugar from the plant
Plant —> get nitrogen produced by the bacteria
How is ammonia produced on an industrial scale?
Using the haber process
What does the haber process produce?
Ammonia
Haber process equation
N2 + 3H2 ⇌ 2NH3
What is ammonia produced for on an industrial scale?
For fertilisers
Conditions of haber process (temperature, pressure, catalyst)
450 degrees Celsius
200 atm
Iron catalyst
How does liquid ammonia come from the haber process?
Gases are cooled and ammonia turns to liquid
Cons of the haber process
Expensive
Inefficient
Releases CO2
Describe the conditions of the haber process
Extreme
How are the conditions for producing ammonia using the haber process extreme?
Bacteria can do it 1atm, but the haber process is at 200atm
Enzyme in nitrogen fixation
Nitrogenase
2 types of bacteria in nitrificaion
Nitrosomonas
Nitrobacter
Number of stages of nitrificaiton
2
What can bacteria use ammonium to make?
Nitrates, which can be absorbed and used by the plant for growth
What can use ammonium to make nitrates?
Bacteria
What can happen to nitrates?
Can be absorbed and used by the plant for growth
What release nitrogenous compounds during decomposition (decay)?
Bacteria and fungi
Products f decomposition
Ammonium ions
Another word for decomposition
Putrefaction
When do bacteria and fungi release nitrogenous compounds during decomposition (decay)?
When an organism dies
Stages of nitrification
Bacteria…
Convert ammonium into nitrite
Convert this into nitrate
Nitrosomonas
Convert ammonium into nitrite during nitrification
Nitrobacter
Convert nitrite into nitrate during nitrification
What happens to nitrate once it’s been formed?
Absorbed into plan root hair cells by active transport
Where is nitrate absorbed to and how?
Into plant root hair cells
Active transport
What type of bacteria are both Nitrosomonas and Nitrobacter?
Free living
Obligate aerobe
Denitrification
The loss of soluble nitrate compounds from the soil
What can occur under anaerobic conditions (denitrification)?
Nitrate (produced by nitrifying bacteria) can be converted back into atmospheric nitrogen and lost from the soil
Under what conditions can nitrate be converted back into atmospheric nitrogen and lost from soil?
Anaerobic
What happens when nitrate is converted back into atmospheric nitrogen and lost from the soil?
Nitrate supplies will eventually run out
Decreases soil fertility
How do farmers avoid denitrification and what does this do?
Plough the soil
Ploughing mixes the soil with air
Why does ploughing soil work to stop denitrification?
The oxygen from the air inhibits the denitrifying bacteria Pseudomonas (grows best under anaerobic conditions) and encourages the growth of Nitrosomonas and Nitrobacter (aerobic nitrifying bacteria) and Azotobacter (aerobic nitrogen fixing bacteria)
Denitrifying bacteria
Pseudomonas
Describe Nitrosomonas and Nitrobacter
Aerobic nitrifying bacteria
Describe Azotobacter
Aerobic nitrogen fixing bacteria
Describe land that isn’t ploughed
Water logged soil
Lots of denitrification
Little oxygen in soil
Poor conditions for nitrification
=soil with little nitrogen
Why can’t trees survive in water logged soil?
Limits O2 supply to the roots
Prevents CO2 from diffusing away
How have plants evolved to live in soil with little nitrogen?
Make use of the free available source of nitrogen in insects
2 examples of plants that have evolved to live in soil with little nitrogen
Sundew
Butterwort
Describe how sundew work to obtain nitrogen form insects
Leaves with hairs
Secrete a sticky fluid onto the hairs = catch insects
Fluid contains enzymes to break the insects down
Absorb nitrogen from the compounds in the insect’s bodies
Describe how butterwort work to obtain nitrogen form insects
Spectres a sticky fluid that catches insects
Absorbs nitrogen form the compounds in the insect’s bodies
What’s the name for plant that absorb nitrogen from the compounds in an insect’s body?
Insectivorous
What do farmers do when growing crops on land and why?
Add nitrates to the soil to make it more fertile
What happens when we overuse nitric fertilisers?
The excess is washing away from the land and leaks into water courses
Leaching
Soluble compounds and ions, like nitrate are washed out of the soil by rain water and can be carried into rivers and lakes
Summary of eutrophication
Nutrient load up
Plants flourish
Algae blooms, oxygen is depleted
Decomposition further depleted oxygen
Death of the ecosystem
What are these stages describing?
Nutrient load up
Plants flourish
Algae blooms, oxygen is depleted
Decomposition further depleted oxygen
Death of the ecosystem
Eutrophication
Nutrient load up stage of eutrophication
Excessive nutrients from fertilisers are flushed form the land into rivers or lakes by rainwater
Plants flourishing stage of eutrophication
These pollutants cause aquatic plant growth of algae, duckweed and other plants
Algae blooms
Rapid increase in the growth of algae in the soil, stimulated by the high levels of nitrates
Algae blooms, oxygen is depleted stage of eutrophication
Algae blooms, preventing sunlight reaching other plants
The plants die and oxygen in the water is depleted
Decomposition further depleted oxygen stage of eutrophication
Dead plants are broke down by bacteria (decomposers) using up even more oxygen in the water
Death of the ecosystem stage of eutrophication
Oxygen levels reach a point where no life is possible
Effects the whole ecosystem
Fish, insects and other organisms die
During which stage of eutrophication do oxygen levels rapidly decrease?
Decomposition further depleting oxygen
2 examples of pollution indicator species
Bloodworms
Rat-tailed maggots
How are bloodworms and rat-tailed maggots (pollution indicator species) able to survive in low oxygen levels?
Adapted for surviving in low O2 concentrations and polluted conditions
Pollution indicator species that are only present in clean waters
Mayfly larvae
Stonefly larvae
Daphnia
When are mayfly larvae, stonefly larvae and daphnia (pollution indicator species) present and why?
Only in clean water
Very sensitive to O2 levels
Humus
Dead organic matter in soil
Describe an area that undergoes secondary succession
Has been colonised before
What happens to the animal population when there’s more plants and why
Increases
More niches for the animals
What type of conditions does leghaemoglobin provide and why?
Anaerobic
Nitrogen fixation only occurs under anaerobic conditions
Another way of describing a climax community
Community has reaches equilibrium
What cannot happen in waterlogged soil?
Roots unable to respire aerobically
No active transport of minerals
Benefits to insectivorous plants catching prey instead of fixing nitrogen
It takes a lot of ATP to fix nitrogen
It’s more energy efficient to digest insects than to fix nitrates
Why do fish die when introduced to a new fish tank?
Due to a lack of nitrogen cycle
Explain why fish die when introduced to a new fish tank
Fish produce nitrogenous waste in the form of ammonium
Ammonium is toxic at high levels
Toxic water kills the fish
Why do fish not die in their natural environment even though they produce nitrogenous waste in the form of ammonium which is toxic?
Due to the nitrogen cycle - bacteria carry out nitrification
Describe ammonium
Toxic at high levels
What do we need to do in a fish tank in order to form a nitrogen cycle?
Make a natural environment for the fish
How do we make a natural environment for a fish in a fish tank and why?
Set up a few weeks before getting a fish
Put in plants
Natural bacteria will process nitrogen
Will make a nitrogen cycle
Compare the carbon cycle to the nitrogen cycle
The carbon cycle is simpler than the nitrogen cycle, but is very influential on the environment
Photosynthesis stage of the carbon cycle
Carbon dioxide in the atmosphere is fixed into carbohydrates and sugars and starches by the light independent stage of photosynthesis
Respiration stage of the carbon cycle
In plants and animals, respiration releases CO2 into the atmosphere due to the action of decarboxylase in the link reaction and Krebs cycle
How does respiration release CO2 into the atmosphere?
Due to the action of decarboxylase in the link reaction and Krebs cycle
Microorganisms responsible for decay
Fungi and bacteria
Describe the decomposition stage of the carbon cycle
Microorganisms responsible for decay (e.g - fungi and bacteria) are decomposers, which release CO2 into the atmosphere due to respiration
They decompose dead plants and waste from animals
Describe the feeding stage of the carbon cycle
Carbon fixed in organic molecules by producers pass from trophic level to trophic level, along food chains, during feeding
How are fossil fuels formed?
When conditions aren’t right for decomposition, so dead plants and animal waste end up not decomposing
Describe conditions that aren’t right for decomposition
Too cold
Not enough oxygen
Water logged
What are fossil fuels formed from?
The remains of dead plants and animals
How long does it take for fossil fuels to be formed?
Millions of years
Under which conditions are fossil fuels formed and why?
Anaerobic
Anaerobic conditions inhibit decay, so fossil fuels are formed instead of decomposition occurring
What form fossil fuels from the remains of dead plants and animals?
Carbon rich biological molecules
Examples of fossil fuels
Oil
Coal
Gas
What happens during the combustion of fossil fuels?
Releases carbon in the form of CO2 into the atmosphere
What’s the biggest problem with the carbon cycle?
There’s a net increase in CO2 in the atmosphere
What happens to fossil fuels if not used for fuel?
Remain untouched for millions of years like a carbon store
What does digging fossil fuels and burning it do?
Releases it in a short space of time
How long have we been burning fossil fuels for?
About 200 years
What does increasing CO2 levels cause?
Climate change and global warming
What’s the issue with burning fossil fuels?
Releases more CO2 into the air than would be there originally
What is these in the carbon cycle?
An imbalance
Why is peat referred to as a fossil fuel?
It’s a carbon store that’s built up over millions of years
Why has it taken so long for peat to build up as a fossil fuel?
Could have been…
Low O2 levels
Cold
Water-logged soil
Draw the carbon cycle
(See notes)
What is peat? Describe it
Thick layers of organic material
Spongey, dark, water-logged
What can be done to peat to use it as a fuel?
When it’s dried out, it can form bricks of fuel
How is positive feedback occurring with peat, a type of fossil fuel?
In the areas where peat is formed, due to the temperatures of the earth increasing, the peat is starting to decompose faster
= CO2 is released faster
This causes positive feedback as more CO2 leads to it being hotter still
What is it referred to when, in the places where peat is formed, due to the temperatures rising, it’s decomposing faster to release CO2 faster?
Positive feedback
What does increased atmospheric CO2 lead to?
An enhanced greenhouse effect, commonly referred to as global warming
What drives what in terms of global warming and climate change?
Glad warming drives climate change
What will climate change ultimately do?
Affect the distribution of species and increase extinction rate
List 5 effects of climate change
Melting polar ice cap and rising sea levels
Increased frequency of extreme weather
Increased desertification and soil erosion
Increased extinction rates
Changes in the distribution of disease vectors such as mosquitos - found in areas where they weren’t before
What do all of the effects of climate change have a global impact on?
Biodiversity and agriculture
What does an increased extinction rate lead to?
Less biodiversity
What does increased desertification and soil erosion lead to?
Agricultural problems
Explain the greenhouse effect
- Radiation from the sun
- Some solar radiation is reflected by the earth and the atmosphere, but most is absorbed by the earth’s surface and warms it
- Some of the infrared radiation passes through the atmosphere. Some is absorbed and re-emitted in all directions by greenhouse gas molecules (e.g - CO2). The effect of this is to warm the earth’s surface and the lower atmosphere.
Why is the greenhouse effect good?
There would be no life without it
Name a planet where there’s no greenhouse effect and explain why this is true
Mars
Only a thin atmosphere
What happens on mars due to there being no greenhouse effect?
Huge temperature swings
What’s the problem with CO2 with the greenhouse effect?
Increasing CO2 levels enhances the greenhouse effect
Why does increasing CO2 levels enhance the greenhouse effect?
CO2 absorbs heat radiating the earth’s surface and re-releases it in all direction, including back towards the earth’s surface
Carbon footprint
The amount of carbon dioxide released into the atmosphere as a result of the activities of a particular individual, organisation or community over a period of one year
What in our day-to-day lives increases our carbon footprint?
Driving cars
Heating Homs
Food eaten (the amount of carbon used in production)
Over what time period is a carbon footprint a measure of?
A year
How can we reduce our carbon emissions?
By lowering our carbon footprint
Give reasons why agriculture has such a high carbon footprint
The production of farm tools
The production of insecticides, fungicides and fertilisers
Farm machinery, powered by fossil fuels
Transport of produce
In which industry to big changes need to be made and why?
Farming
To reduce the carbon footprint
Possible changes to farming practices to reduce the carbon footprint
Produce less meat
Crops should be grown for human consumption, not as animal feed
Alternatives to rice paddy fields
Packaging should be reduced to a minimum
Transport distances (food miles) should be reduced and more food produced locally for local people
Why should we produce less meat?
Meat production requires more resources (land, chemicals and feed) than crop production and therefore has a larger carbon footprint
What’s the issue with rice paddy fields?
Produce methane
What’s the problem with methane?
It’s a greenhouse gas 25 times more potent than CO2
Explain how deforestation could increase the concentration of CO2 in the atmosphere
Trees take in CO2 during photosynthesis
More CO2 used in combustion
More decomposition of dead roots = more CO2
Describe how deforestation could decrease the concentration of atmospheric CO2
Trees respire, releasing CO2
How does a soil actually form during succession?
Enzymes break down rock
What does there have to be in a climax community?
Trees
What happens to plants when they’re cold?
Not resistant to cold = die
Lower germination of certain species = less increase in number of species
Why is there a net increase in CO2 in the atmosphere currently?
Increased combustion of fossil fuels (releases CO2)
Deforestation (less photosynthesis to absorb CO2)
Measures that would reduce the effect of human activity on the carbon cycle
Reduce use of fossil fuels
Alternative energy sources
Carbon tax
When does water logging of soil occur?
When there’s too much water
What’s the issue with waterlogged soil?
No oxygen for roots to respire
No active uptake of minerals
What conditions is water logged soil under and what does this lead to?
Anaerobic
Denitrification
What are the risks with having lots of individuals of the same species in one area?
Predators
Intraspecific competition
Disease
What are ammonium ions used for?
To make amino acids, proteins and DNA
What does Leghaemoglobin do to O2?
binds it
How do we create axes at right angles to each other for sampling?
With tapes
What does secondary succession do to the environment and what does this lead to?
Changes in the environment
Allows other species to grow
What is the carrying capacity of an environment determined by?
-biotic and abiotic factors (environmental resistance)
-predator/prey relationships
-inter/intraspecific competition
What are decomposers?
Bacteria/fungi that respire
First species to return during secondary succession
Pioneer species
Causes of species extinction
Hunting
Invasive species/alien species introduced
Habitat loss
Fishing
Pollution
Competition from domestic animals
Global warming
Natural selection
Why is it good to genetically modify plants for nitrogen fixation?
Higher yield = less land needed for crops = more land for increasing biodiversity
Less chemical fertilisers = less eutrophication
Things to consider when reintroducing a species into the wild
Need a disease-free donor population
Receiving habitat needs to be suitable
Resources and expertise need to be available for their protection
When introducing, use ones that come from the same region (e.g - European) so that they have the correct genetics of the population and take up the correct niche
What does ploughing soil encourage?
Nitrification (not nitrogen fixation)
Why do warm blooded organisms need to eat more often than cold blooded organisms?
Since warm blooded organisms need to maintain body temperature and so use more food in respiration to produce heat
