Unit 5: On the Wild side Flashcards
1
Q
What is an ecosystem?
A
All organisms living in a particular area, known as a community, as well as all non-living elements of the particular environment.
2
Q
What is a community?
A
All of the populations of all the organisms living in a particular habitat at a particular time.
3
Q
Define population
A
All of the organisms of a particular species living in a particular habitat and a particular time.
4
Q
Define habitat
A
A place where an organism lives
5
Q
How can the distribution and abundance of a habitat be controlled?
A
- Biotic factors (living factors) like predators, food availability, parasites or disease.
- Abiotic factor (non-living factors) like light, oxygen, moisture levels or temperature.
6
Q
What is ecological niche?
A
A species particular role in its habitat. It consists of its abiotic and biotic interactions with the environment. Species distribution and abundance will depend on the number and type of ecological niches available within a habitat.
7
Q
What is the niche concept?
A
It states that only one organism can occupy each niche at one given time in a given habitat. If two or more species have a niche that overlaps, the best adapted will outcompete the others in surviving to reproduce.
8
Q
What is succession?
A
It is the changes in species inhabiting over time. It is brought about by changes to the environment made by the organisms colonising it themselves.
9
Q
What is primary succession?
A
Occurs when an area was completely deprived of life is first colonised by community of organisms, for example, after the eruption of a volcano- soil must first be established before more complex organisms can grow
10
Q
What is secondary succession?
A
Occurs with existing soil that is clear of vegetation. This may occur after an event such as forest fires.
11
Q
What are the abiotic factors that can make the population size vary?
A
Population size (abundance) can change due to the amount of light, water or space available, temperature of the surroundings or the chemical composition. When ideal for species, organisms can grow fast and reproduce successfully.
12
Q
What is interspecific competition?
A
When different species compete for the same resources. For example, red and grey squirrels compete for the same food and habitat. Resources for both species is reduced (limited) Less energy for reproduction and growth.
13
Q
What is intraspecific competition?
A
When the same species compete for the same resources. Population of a species increases when resources are plentiful. As soon as the population increases, there will be more organisms competing for the same amount of space and food. Then becomes limiting and population declines. Smaller population means less competition- population grows. Maximum stable population size of a species that an ecosystem can support (carrying capacity)
14
Q
How are predator and prey population size linked?
A
Prey population size increases, more food for predators so population size grows. More prey is eaten so population begins to fall, less food for predators so population decreases.
15
Q
How does distribution vary because of abiotic factors?
A
Some plants only grow in the northern hemisphere due to solar input (light intensity) is greatest. Some plants don’t grow near the shoreline due to it being to saline (salty). Large trees can’t grow in polar regions because the temp is too low.
16
Q
How does distribution vary because of biotic factors?
A
Interspecific competition can affect the distribution as one of two species is better adapted to the environment and the less-well adapted will be out-competed.
17
Q
How does every species occupy a different niche?
A
A niche is the role of a species within a habitat. Biotic interactions e.g. organisms eat/eaten by. Abiotic interactions e.g. the oxygen the organism breathes in. Niche is unique and only occupied by one species, it may look like two are filling the same niche but could be slightly different. Organisms can only exist in habitats where all the conditions that make up their role exist.
18
Q
What is abundance?
A
The number of individuals of one species in a particular area and percentage cover can be used.
19
Q
What is distribution?
A
Where a particular species is within the area you’re investigating.
20
Q
What is random and non-random sampling?
A
Random is to avoid bias- divide the field into grids and use a random coordinate generator. Non-random - a lot of variety in the abiotic factors and/or distribution (systemic sampling- fixed intervals)
21
Q
What are point quadrats and how could they be used to investigate plant population?
A
Horizontal bar with two legs and placed into the ground at random points. Pins are dropped into the holes in the frame and every plant the pin touches is recorded.
22
Q
What are the different types of transects?
A
Line transect- tape measure placed along the transect and the species that touch the tape are recorded.
Belt transect- data is collected along the transect using frame quadrats placed next to each other.
Interrupted transects- take measurements are intervals
23
Q
How can abundance and distribution be shown on a kite diagram?
A
Abundance of each organism is shown by the thickness of the kite shape. The abundance is plotted above and below a central line to make the shape symmetrical. The x-axis shows the distance along the transect line.
24
Q
How can we measure different abiotic factors within a habitat?
A
Climate- temperature, rainfall, humidity, oxygen availability, solar input, Edaphic (soil) factors- pH and moisture content, topography- relief, slope angel, aspect (compass)
25
What are the two different types of succession?
Primary succession- newly formed/exposed e.g. where a volcano has erupted to form a new rock surface. No soil or organic material to start off with.
Secondary succession- Land that has been cleared of all the plants, but where the soil remains.
26
What is the first stage of succession?
Primary succession- species colonise new land surface- seeds and spores are blown by the wind and begin to grow (pioneer species). Abiotic conditions- harsh (no soil to retain water), species only grow due to begin specially adapted. Species change the abiotic conditions- as they die and decompose organic material (humus) is added, basic soil. Less hostile, basic soil helps retain water, new organisms with different adaptations can move in and grow. Die and decompose, adding more organic material, making soil deeper and richer in minerals. Larger plants like shrubs can grow.
27
What is the second stage of succession?
Secondary succession- same way, but soil larger is already there. Different plants and animals that are better adapted for the improved conditions move in and out compete the species that were already there, becoming the dominant species in the ecosystem. More complex, new species move in alongside existing species, which means that biodiversity increases.
28
What is the final stage of succession?
Climax community- the ecosystem is supporting the largest and most complex community of plants and animals it can and won't change much more-steady state.
29
What is an example of primary succession?
1) Pioneer species colonise- lichens grow on and break down rocks, releasing minerals
2) Lichens die- decomposed- helping to form thin soil- thickens as more organic soil is added- new species like moss can grow
3) Larger plants need more water and can move in as the soil deepens, e.g. grasses and small flowering plants- soil continues to deepen as the larger plants die ad continue to decompose.
4) Shrubs, ferns and small trees begin to grow, out-competing the grasses and smaller plants to become the dominant species- diversity increases
5) Finally, the soil is deep and rich enough in nutrients to support larger trees- become dominant species, and the climax community is formed.
30
What is a climax community like in a temperate climate?
Plenty of water available, mild temperatures and not much change between the seasons. The climatic climax will contain large trees because they can grow there due to the deep soil.
31
What is the climax community like in a polar climate?
Not much water is available, temperatures are low, massive changes between seasons. Large trees can't grow here due to the conditions, so the climatic climax contains only herbs and shrubs, nut it's still the climax community.
32
How can succession be prevented?
Human activities- stopped artificially like this the climax community is called a plagioclimax.
33
What is an example of human activities stopping succession?
Regularly mown grassy fields won't develop subs or trees, even if the ecosystem could support them. Growing pints of the woody plants are cut off by the lawnmower, so large plants can't establish themselves. The longer the interval between mowing, the further succession can progress and the more diversity increases. But with more frequent mowing, succession can't progress and diversity will be lower- only grass will survive.
34
Define phosphorylation
adding phosphate to a molecule, e.g. ADP is phosphorylated to ATP
35
Define photophosphorylation
adding phosphate to a molecule using light
36
Define photolysis
splitting of a molecule using light energy
37
Define hydrolysis
splitting of a molecule using water e.g. ATP is hydrolysed to ADP
38
Define redox reaction
reactions that involves oxidation and reduction
39
What is a reduction reaction?
gains an electron or gained a hydrogen or lost an oxygen
40
What is an oxidation reaction?
lost an electron or lost hydrogen or gained oxygen. Oxidation of one molecule always involves the reduction in another molecule
41
What biological processes need energy?
Plants- photosynthesis, active transport, DNA replication, cell division and protein synthesis.
Animals- muscle contraction, maintain body temperature, active transport, DNA replication, cell division, protein synthesis
42
What is photosynthesis?
A process where energy from light is used to break apart the strong bonds of H2O molecules. Hydrogen from the breakdown of H2O is stored in glucose, which is formed when it is combined with CO2. O2 is formed and released into the atmosphere during this process. Energy is stored in glucose until plants release it by respiration. Animals obtain glucose by eating plants or other animals, then respire the glucose to release energy.
43
What is the balanced equation for photosynthesis?
6CO2 + 6H2O + energy ---> C6H12O6 (Glucose) + 6O2
44
How does energy get to a cell?
ATP is an immediate source of energy in a cell. A cell can't get its energy directly. During respiration, glucose is broken down, releasing energy, used to make ATP. ATP carries energy around the cell to where it is needed. It is synthesised by the phosphorylation of ADP using energy from an energy-releasing reaction, e.g. the breakdown of glucose in respiration.
45
How does photosynthesis use enzymes and coenzymes?
Photosynthesis uses a lot of enzymes. This means that the rate at which photosynthesis can occur is affected by the same things that affect the rate of enzyme-controlled reactions. Relies on the action of coenzymes, which aids the function of an enzyme. They transfer chemical groups from one molecule to another. NADP (coenzyme in photosynthesis) transfers hydrogen from one molecule to another (reduce or oxidise)
46
Where does photosynthesis take place?
Chloroplasts- flattened organelles. They have a double membrane called chloroplast envelope- which keeps the reactants for photosynthesis close to their reaction sites. Thylakoids (fluid-filled sacs) have a large surface area- allowing much light energy to be absorbed. They are stacked up in the chloroplast into structures called grana (singular is granum). Linked by lamellae. Lots of ATP synthase molecules are present in the thylakoid membranes to produce ATP in the light-dependent reaction.
47
What pigments are contained in the chloroplast?
Photosynthetic pigments (chlorophyll a, chlorophyll b, and carotene). Coloured substances absorb light energy needed for photosynthesis and are found in the thylakoid membrane- attached to proteins. Protein and pigment are called photosystem
48
What are photosystems?
There are two photosystems used by plants to capture light energy. Photosystem I (or PSI) absorbs light best at a wavelength of 700m and photosystem II (PSII) absorbs light best at 680mm.
49
What is the stroma?
Contained within the inner membrane of the chloroplast and surrounding the thylakoids is a gel-like substance. It contains all enzymes, sugars and organic acids required for the light-dependent reactions as well as oil droplets (which store non-carbohydrate organic material)
50
What is the overview of the light-dependent reaction?
Needs light energy. Takes place in the thylakoid membranes. Light energy is absorbed by photosynthetic pigments in the photosystems and converted to chemical energy. Light energy is used to add a phosphate group to ADP to make ATP, and to reduce NADP to form reduced NADP. ATP transfers energy and reduced NADP transfers hydrogen to the light-independent reaction. During this H2O is oxidised to O2.
51
What is the overview of the light-independent reaction?
Also called the Calvin cycle and doesn't use light energy directly. But it does rely on the products of the light-independent reaction). It takes place in the stroma of the chloroplast. Here, ATP and the reduced NADP from the light-dependent reaction supply the energy and hydrogen to make glucose from CO2.
52
What is it called when ATP is made from ADP and Pi (inorganic phosphate)?
Photophosphorylation
53
What are the products of the light dependent reaction?
- ATP from ADP and Pi (photophosphorylation)
- reduced NADP from NADP
- splitting water into protons (H+ ions), electrons and oxygen (photolysis)
54
What is the first stage of the light-dependent reaction?
- Light energy absorbed by PSII.
- Light energy excites electrons in the chlorophyll
- Electrons move to a higher energy level
- These move along the electron transport chain to PSI
55
What is the second stage of the light-dependent reaction?
- Excited electrons from the chlorophyll leave PSII to move along the electron transport chain, which must be replaced
- Light energy splits water (into electrons, protons and oxygen)- photolysis
- Reaction is H2O --> 2H+ + 1/2O2
56
What is the third stage of the light-dependent reaction?
- Excited electron loses energy as they move along the electron transport chain
- Energy is used to transport protons into thylakoids so that thylakoids have a higher concentration of protons than the stoma. This forms a proton gradient across the membrane
- Protons move down their concentration gradient, into the stroma, via the enzyme ATP synthase. The energy from this movement combines ADP and inorganic phosphate (Pi) to form ATP.
57
What is the fourth stage of the light-dependent reaction?
- Light energy is absorbed by PSI, which excites the electrons again to an even higher energy level.
- Finally, the electrons are transferred to NADP, along with proton (H+ ion) from the stoma, to form reduced NADP.
58
Why does cyclic phosphorylation only produce ATP?
Only uses PSI. Electrons from the chlorophyll molecule aren't passed onto NADP but are passed back to PSI via electron carriers. This means the electrons are recycled and can repeatedly flow through PSI. This process doesn't produce any reduced NADP or O2- it only produces small amounts of ATP.
59
What is the light-independent reaction?
Also known as the Calvin cycle, it is the final stage of photosynthesis. It uses ATP and reduced NADP to make glucose. It is also known as carbon dioxide fixation because carbon from CO2 is 'foxed' into an organic molecule.
60
What are the stages of the light-independent reaction of photosynthesis?
- CO2 enters the leaf through the stomata and diffuses into the stroma (chloroplast)
- Combined with ribulose bisphosphate (RuBP), the reaction is catalysed by the enzyme RUBISCO.
- Unstable 6- carbon compound, breaks down into 2 molecules of 3-carbon compound glycerate 3-phosphate (GP)
- Hydrolysis of ATP (from the light-dependent reaction) provides energy to turn a 3-carbon compound (GP) into a different 3-carbon compound glyceraldehyde 3-phosphate (GALP)
- Requires H+ ions (from reduced NADP- from the light-dependent reaction). Reduced NADP recycled to NADP.
- Some GALP is then converted into useful organic compounds (glucose) and some continue in the Calvin cycle to regenerate RuBP.
- 2 molecules of GALP can make hexose sugar (glucose)
- 5 of every 6 molecules of GALP produced in the cycle are used to regenerate RuBP
- Regenerating RuBP uses the rest of the ATP produced by the light-dependent reaction.
61
What is the product of the Calvin cycle?
Essential biological molecules:
- Carbohydrates- glucose used in respiration- provides the energy needed
- Lipids- glycerol (synthesis of GALP) and fatty acids (synthesis of GP)
- Amino acids (from GP)
- Nucleic acids (RNA- ribose- made using GALP)
62
What is the experiment for investigating photosynthesis using extracts of chloroplast (Hill reaction)?
1. Remove stalks from leaf samples. Cut into small sections. Grind the sample using a pestle and mortar and place it into a chilled isolation solution.
2. Place several layers of muslin cloth into a funnel and wet it with an isolation medium to filter the sample into a beaker.
3. Suspend the beaker in an ice water bath to keep the sample chilled.
4. Transfer to centrifuge tubes and centrifuge at high speed for 10 minutes. This will separate chloroplasts into the pellet.
5. Remove supernatant and add pellet to fresh isolation medium.
6. Store the isolation solution on ice.
7. Set the colourimeter to the red filter. Zero using a cuvette containing chloroplast extract and distilled water.
8. Place the test tube in a rack 30cm from the light source and add DCPIP. Immediately take a sample and add it to the cuvette.
9. Measure the absorbance of the sample using the colourimeter
10. Take a sample and measure its absorbance every 2 minutes for 10 minutes.
11. Repeat for different distances from the lamp up to 100 cm. This will vary the light intensity.
63
How is energy transferred through the ecosystem?
- energy enters the ecosystem through photosynthesis
- photosynthesis--> convert sunlight energy into a form that can be used by other organisms- plants are called producers (produce organic molecules)
-producers store sunlight energy as biomass-- energy transfers through ecosystems as biomass transfers
- energy transferred through living organisms --> producers eaten by primary consumers--> secondary consumers--> tertiary consumers
- each stage is called a trophic level
64
Why is it that not all the energy is transferred to the next trophic level?
- 90% of total energy is lost through various ways
- 60% is never taken in by organisms- plants can't use all the light energy that reaches their leaves e.g. some is the wrong wavelength and some passes straight through the leaves. Some sunlight hits part of the plant that can't photosynthesise. Some parts of food can't be broken down like bones and passed to decomposers (break down dead or undigested material) or waste.
- Rest of the available energy (40%) is taken in (absorbed)- gross productivity. 30% is lost to the environment (respiratory loss). 10% becomes biomass (stored or used for growth)- net productivity.
65
What is net productivity?
(or biomass) is the amount of energy that's available for the next trophic level
Calculated:
net productivity= gross productivity - respiratory loss
66
How do you calculate how efficient the energy transfer is?
(net productivity/energy received) x 100 = efficient energy transfer
67
What is net primary productivity (NPP)?
Just talking about producers, net productivity
68
What is gross primary productivity (GPP)?
Gross productivity just of producers
69
How do you calculate the net primary productivity?
Net primary productivity= gross primary productivity-plant respiration
70
How can the energy transfer between trophic levels be measured?
- calculate the difference between the amount of energy in each level
- calculate the amount of energy in the trophic levels by measuring the dry mass of the organism (biomass) - how much energy an organism contains
- sample of the organism- drying the organism in an oven set to a low temperature--> mass becomes constant (all the water will be removed)
- then multiply the results from the sample by the size of the total population to give the total amount of energy in the organism at that trophic level
- the difference in energy between the trophic levels is the amount of energy transferred.
- however, energy may have been taken in from other sources other than the producer measured. This wouldn't create an accurate estimate of energy transfer between two organisms--> for accuracy you will need to include all the individual organisms at each trophic level
71
How does climate change cause changes in weather patterns?
- rapid increase in global temperatures seen over the last century
- changes in rainfall patterns and seasonal cycles
72
How do temperature records show climate change?
- since the 1850s temperature has been measured around the world using thermometers
- a reliable but short-term record of global temperature change
-the general trend shows that the temperature of the Earth is increasing --> evidence for climate change
73
How does dendrology show climate change?
- how old a tree is using tree rings
- most trees produce one tree ring within their trunks per year
- the thickness of the ring depends on the climate when the ring was formed- when it's warmer the rings are thicker (because the conditions for growth are better)
- scientists can take cores through tree trunks and then date each ring by counting them back from when the core was taken--> shows the climate of each year
- most recent rings are the thickest --> it had become warmer
74
How does pollen in peat bogs show climate change?
- pollen is often preserved in peat bogs
- peat bogs accumulate in layers so the age of the preserved pollen increases with depth
- cores from the peat bogs and extract pollen grains from different aged layers. They then identify the plant species the pollen came from
- only fully grown plants produce pollen, so samples only show the species that were successful at the time.
- scientists know the climate that different plant species live in now. When they find preserved pollen from similar plants, it indicates that the climate was similar when that pollen was produced
- because plant species vary with climate the preserved pollen will vary as climate changes over time.
- so a gradual increase in pollen from a plant species that's more successful in a warmer climate would show a rise in temperature
75
How does human activity (anthropogenic) cause climate change?
- human activity causes the enhanced greenhouse effect- absorbing more energy than there is reflected and lost in space
- greenhouse effect is essential in keeping the planet warm, but too much greenhouse gases cause the planet to warm up.
- CO2 concentration is increasing with more fossil fuels like coal, oil and natural gas (also trees being burnt) being burnt (releases CO2). Also increases due to the destruction of natural sinks (store carbon organic compounds, decomposers break down the organic compounds and respire them (releasing CO2)
- methane increases as more fossil fuels are extracted, more decaying waste, and more cattle (give off methane as a waste gas). Also released from natural stores (frozen grounds--> temps increase--> stores will thaw--> release large amounts of methane into the atmosphere.
76
What is the relationship between CO2 concentrations and temperature?
Correlational and casual relationship
77
How do models of future climate change based on extrapolated greenhouse house gas concentration data have limitations?
- don't know how greenhouse gas emissions will change
- don't know exactly how each emission scenario will cause global temperature to rise
- change in atmospheric greenhouse gas concentrations due to natural causes isn't known
- don't know what attempts there will be to manage the atmospheric concentration of greenhouse gases, or how successful
- don't know what effect increasing greenhouse gas concentrations will actually have on the climate because of the complex feedback systems involved.
78
How does temperature affect plants and animals - Does increasing temps affect the rate of enzyme activity?
- the rate of enzyme-controlled reactions increases when temp increases as there is more kinetic energy, so molecules can move faster and are then more likely to collide but if it gets too high, the reaction stops. As the temp rises --> enzyme's molecules vibrate more but if the temp goes above a certain point, it will break the bond that holds the enzyme in shape and the active site changes and the enzyme and substrate can no longer fit. Enzyme denatures
79
How can temp increase cause changes in an organism's life cycle, development and distribution?
- organism's metabolism is all the chemical reactions to keep it alive. Metabolic reactions are controlled by enzymes. An increase in temperature will mean the metabolic reactions speed up, so their rate of growth will increase. Develop faster and progress through their life cycle faster
- temp is too high--> metabolic reactions slow down--> rate of growth will decrease--> progress through life cycle slower
- affect the distribution of some species--> live in ideal conditions but if they change, they'll have to move to a new area where the conditions are better, if they do not move they will die out. Range of some species may expand if the conditions in previously uninhabitable areas change
80
How will changing rainfall patterns affect plants and animals?
- global warming will alter global rainfall patterns (some areas will get more or less rain). This will affect the development and life cycle of organisms (for example: reduced rainfall will cause ocotillo plants to remain dormant for long periods)
- affect the distribution- species aren't adapted to live in deserts and would have to move or they will die out
81
How does global warming affect seasonal cycles?
- changing the timing of seasons
- organisms have adapted to the timing of the seasons and the changes that happen like in temperature
- it will affect the development and life cycles of some organisms
- it will affect distribution Swallows live in South Africa in the winter and fly to Europe to breed in early spring. Early British spring --> produces flowers and insects at earlier times--> isn't much food available --> reduces the number of Swallows born in Britain --> could die out and the distribution has changed.
82
How does seed growth change based on temperature (practical investigation)?
1) plant some seedlings in soil trays and measure the height of each seedling
2) put the trays in incubators at different temperatures
3) make sure all other variables stay the same
4) after a period of incubation record the change in height and the average growth rate: average change in seedling height each day/ incubation period
83
How to investigate the effects of temperature on brine shrimp hatch rate (practical investigation)?
1) put an equal number of brine shrimp eggs in water baths set at different temperatures
2) make sure all the variables stay the same
3) the number of hatched brine shrimp in each water bath is recorded every five hours and the hatch rate can be calculated by: number of hatched brine shrimp in each water bath/ number of hours
84
What is the practical investigation to look at the effects on the initial rate of enzyme-catalysed reactions?
1) set up boiling tubes containing the same volume and concentration of hydrogen peroxide. To keep the pH constant, add equal volumes of a suitable buffer solution to each tube.
2) set up the boiling tube with a bung and delivery tube going to an upside-down delivery tube in a trough of water
3) put each boiling tube in the water of water with a different temp (20, 40, 60) along with another tube containing catalase
4) use a pipette to add the same volume and concentration of catalase to each boiling tube. Then quickly attach the bung to the delivery tube
5) record how much oxygen is produced every 10 seconds in the first minute of the reaction and use a stopwatch to measure the time.
85
How do you calculate the initial rate of reaction on a graph?
1) draw a tangent on a graph using a ruler
2) gradient (of the tangent)(rate of reaction)= change in y-axis/change in x-axis
86
What is the equation for Q10?
Q10= rate at higher temp/rate at lower temp
87
How does Q10 show how the rate changes with temperature?
1) temperature coefficient or Q10 value for a reaction shows how much the rate of a reaction changes when the temperature is raised by 10 degrees C
2) At temperatures before the optimum, a Q10 value means that the rate doubles when the temperature is raised by 10 degrees C. A Q10 value of 3 would mean that the rate has tripled
3) most enzyme-controlled reactions have a Q10 value of around 2
88
Why is it hard to agree on the causes of climate change?
- agreed that global warming is happening- rapid increase in global temps
- human activity is increasing atmospheric CO2 concentrations. The scientific consensus is that the increase in atmospheric CO2 concentrations causes increased global temps
- but a handful of scientists disagree with this and believe that the increase in CO2 concentrations doesn't cause an increase in global temps this could be due to biased and subjective conclusions and could be biased based on funding and who they work for
89
What is the carbon cycle?
- carbon is absorbed by plants for photosynthesis (carbon compounds in plant tissue)
- carbon is passed on to animals when they eat the plants and to decomposers when they eat dead organic matter
- carbon is returned to the atmosphere as all living organisms respire
- if the dead organic matter ends up in a place where there aren't any decomposers, the carbon compounds can be turned into fossil fuels over millions of years
- carbon in fossil fuels is released as CO2 when they're burnt (combustion)
90
How do biofuels decrease atmospheric CO2 concentrations?
- biofuels are fuels produced by biomass - material that is or was recently living. They're often made from crops, which can be replanted after harvesting- making biofuels sustainable
- biofuels are burnt to release energy, which produces CO2
- there is no net increase in atmospheric CO2 concentrations when biofuels are burnt - the amount of CO2 produced is the same as the amount of CO2 taken in when the material was growing
- biofuels are an alternative to fossil fuels and stop the increase in atmospheric CO2 concentrations caused by burning fossil fuels
91
How does reforestation decrease atmospheric CO2 concentrations?
- reforestation is the planting of new trees in existing forests that have been depleted
- more trees means more CO2 is removed from the atmosphere by photosynthesis
- CO2 is converted into carbon compounds and stored as plant tissues in the trees. This means more carbon is kept out of the atmosphere, so there's less CO2 contributing to global warming
92
Why might some people support and oppose the use of biofuels?
- some farmers may support this- government funding in farms of crops for biofuels
- drivers may support this- the price of biofuels is usually lower than oil-based fuels
- consumers may oppose this- as farmland to grow crops could cause food shortages
- conservationists may oppose- forests have been cleared to grow crops for biofuels
93
Why might some people support and oppose the increased use of wind turbines?
- companies that make wind turbines would support- sales increase
- environmentalists might support this- wind turbines produce electricity without increasing atmospheric CO2 concentrations
- local communities may oppose- some people think wind turbines ruin landscapes
- bird conservationists might oppose this- many birds are killed by flying into wind turbines
94
How does evolution change the allele frequency?
- individuals within a population vary because they have different alleles- this is due to gene mutation
- some individuals are better adapted to their environment than others
- individuals that have an allele that increases their chance of survival are more likely to survive, reproduce and pass on their genes, than individuals with different alleles
- This means that there is a greater proportion of the next generation inherits the beneficial allele.
- They are more likely to survive, reproduce and pass on their genes. So the frequency of the beneficial allele increases from generation to generation
95
Why does isolation reduce gene flow leading to speciation?
- species is a group of similar organisms that can reproduce to give fertile offspring, and that speciation is the development of a new species
- speciation is when populations of the same species become reproductively isolated, reducing gene flow (transfer of genes) between two populations. This means that natural selection acts on each population separately- so new species can develop.
- reproductive isolation may occur because of geographical isolation (allopatric specification) or because random mutations produce changes in phenotype that prevent populations from mating (sympatric specification)
96
What does allopatric specification require?
- populations that are geographically separated will experience slightly different conditions and will therefore experience different selection pressures and so different changes in allele frequency
- different alleles will be advantageous in different populations. Natural selection will act on the alleles and increase the frequency of the allele. Allele frequency will also change as mutations occur independently in each population.
- the changes in the allele frequency will lead to differences accumulating in the gene pools to the separated populations, causing changes in phenotypes frequencies
- eventually, the populations will become genetically distinct- their DNA will have become significantly different. Individuals from the different populations will have changed so much that they won't be able to breed with each other to produce fertile offspring- reproductively isolated (separate species)
97
How do seasonal changes cause reproductive isolation?
individuals from the same population develop different flowering or mating seasons or become sexually active at different times of the year
98
How do mechanical changes cause reproductive isolation?
changes in the genitalia prevent successful mating
99
How do behavioural changes cause reproductive isolation?
a group of individuals develop courtship rituals that aren't attractive to the main population
100
What is an example of sympatric speciation that doesn't require geographical isolation?
1) most eukaryotic organisms are diploid- they have two sets of homologous chromosomes in their cells. Sometimes, mutations can occur that increase the number of chromosomes. This is known as polyploidy.
2) individuals with different numbers of chromosomes can't reproduce sexually to give fertile offspring- so if a polypoid organism emerges in a diploid population, the polyploid organism will be reproductively isolated from the diploid organisms
3) if the polyploid organism then reproduces asexually, a new species could develop
4) polyploidy can only lead to speciation if it doesn't prove fatal to the organism and more polyploid can be produced. It's more common in plants than animals
101
What is the evidence to support evolution?
-genomics (is a branch of science that uses DNA technology to determine the base sequence of an organism's genome and the functions of its genes. This allows scientists to make comparisons between organisms' DNA.
-the theory of evolution suggests that all organisms have evolved from shared common ancestors
-closely related species diverged more recently
- evolution is caused by gradual changes in the base sequence of organisms' DNA
- organisms that diverge away from each other more recently should have more similar DNA, as less time has passed for changes in the DNA sequence to occur
For example, humans and chimps have recently diverged and share 94% of the same DNA sequence
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What is proteomics?
- it is the study of proteins (shape, size and sequence of amino acids)
- the sequence of amino acids in a protein is coded for by the DNA sequence in a gene
- related organisms have similar DNA sequences and so similar amino acid sequences in their proteins
- so organisms that diverge away from each other more recently should have more similar proteins, as less time has passed for changes to occur
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How does the scientific community validate evidence for evolution?
- uses data to test theories
- they discuss and share work by:
1) scientific journals- academic magazines, that share new ideas, theories, experiments, evidence and conclusions, allowing to see if they got the same results using the same method. If it is replicable then it is reliable.
2) peer review- before it is published other scientistic review their work to check that the work is valid and that it supports the conclusions and it is valid and experiments are carried out to the highest possible standard
3) conference- meetings so they can discuss work in the form of a lecture or poster presentation. Other scientists can ask questions and discuss their work face to face. It is the easiest way for new research to be shared and discussed.
