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77 Cards in this Set
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Ecosystem - All of the organisms in a particular area, including biotic and abiotic factors Population - All the organisms of one species in a habitat Community - All the organisms of different species that live in the same habitat and interact with each other |
Abiotic factors - The non living features of the ecosystem (temperature, soil pH etc) Biotic factors - The living features of the ecosystem (predators, food) Abundance/population size - The number of individuals of one species in a particular area Distribution - Where a species is within a particular area |
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Why does population size (abundance) vary? |
Abiotic factors - amount of light, water or space available, temperature, chemical composition of surroundings. When abiotic conditions are ideal for a species, organisms will reproduce successfully. If not, they won't as fast or as successfully Biotic factors such as: Interspecific competition - (competition between species) for resources. E.g. red and grey squirrels Intraspecific competition - competition within a species for resources. Population fluctuates as the amount of competition does. More food = big population Less food to share = population shrinks again Maximum stable population size is called the carrying capacity Predation - population sizes of predators and prey are interlinked |
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Why does distribution vary? |
Abiotic factors - organisms only exist where abiotic factors they can survive in exist Biotic factors - interspecific competition can affect the distribution of series. If two species compete and one is better adapted the other, the other species will be driven away |
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What is a niche, fundamental niche and realised niche? |
Niche: The role of a species within its habitat, including its abiotic and biotic interactions. A niche can only be filled by one species Fundamental niche: the niche an organism would fill without limiting factors being present Realised niche: the actual niche an organism fills due to interspecial competition, predation, limited resources etc |
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How do you investigate populations of organisms? |
By looking at abundance and distribution of species in a particular area Abundance can be estimated by counting the number of individuals in samples taken. Percentage cover can also be used to measure the abundance of plants and other immobile organisms Distribution- where a particular species is within the area you're investigating |
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What are quadrats used to investigate? How do you use them? |
Immobile populations. Place on the ground within the area you're investigating. Record the number of individuals of each species in each quadrat. Can also be used to measure percentage cover as they're normally divided into 100 small squares by string. Only count if more than half a square is covered. Most quadrats are 1m by 1m |
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What are point quadrats and how do you use them? |
Horizontal bar on 2 legs with holes set at intervals along its length. They are placed on the ground at random points within the investigated area, and pins are dropped through the holes. Every plant a pin touches is recorded. Used to record the number of individuals of each species, and can be used to calculate percentage cover (number of pins that touch a given species divided by total number of pins) Useful where there is dense vegetation close to the ground |
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What are transects, what are they used for? How are they used? |
Help find out how plants are distributed across an area. There are 3 kinds: Line transects - a tale measure is placed along the transact and the species that touch the tape are recorded Belt transects - data is collected along the transect using frame quadrats placed next to each other Interrupted transects - instead of investigating the whole transect, take measurements at intervals |
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How do you measure abiotic factors? |
Temperature - thermometer Rainfall - rain gauge Humidity - electronic hygrometer Oxygen availability - only in aquatic habitats. Volume of O2 dissolved in water is measured with an oxygen sensor Light intensity - light sensor Soil pH - sample of soil is mixed with water and indicator liquid that changes colour depending on pH. Chart is used to determine pH of soil, or pH monitors Moisture content - mass of soil sample is measured before and after drying. Difference in mass as a percentage of original mass is water content. |
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What are pioneer organisms? |
The first organisms to appear in a bare environment. When they die and decay, they provide soil and nutrients for other organisms to grow in Moss and lichen are examples. Don't need a lot of nutrients to grow. |
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What is primary succession? |
The establishment and development of an ecosystem in an area that was previously uninhabited (newly formed or exposed). No soil or organic matter, just rock |
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Describe the process of primary succession |
Lichens that don't need soil grow on rocks. Weather erosion and lichens break down the rock into smaller pieces Mosses grow in the thin soil layer left when they decompose, trapping moisture and preventing soil erosion more nutrients are added to the soil Soil layer thickens, allowing for grasses, wildflowers and other plants to take over More mosses and ferns grow when that dies. In turn when they die more nutrients are added to the soil Cycle repeats, shrubs and trees (first conifers then deciduous) growInsects birds and mammals move into the area |
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What is succession? What is deflected succession? |
The process by which an ecosystem changes over time A community that only remains stable because human activity prevents succession from running its course. No climax community. E.g. farming |
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What is secondary succession? How is it different to primary succession? |
Succession that occurs in an environment where soil is already present, for example after forest fires. Occurs faster and has larger pioneer organisms (shrubs) as soil is already present Primary creates a new ecosystem, secondary restores the previous ecosystem |
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Describe the process of secondary succession |
Disturbance - e.g. forest fire Pioneer plants grow, for example shrubs. Process is the same as primary succession; when organisms die, nutrients are added to soil, larger plants can grow and larger animals appear. At each stage different plants and animals that are better adapted to conditions move in, out-competing the previous organisms. As succession continues biodiversity increases. Ends in a climax community Can be restarted by another disturbance |
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What is a climax community? |
A mature and stable community reached at the end of ecological succession. Conditions are suited to all organisms in the community |
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What is a plagioclimax? |
The climax community present when succession is stopped artificially by human activities like mowing the lawn |
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Important photosynthesis terms |
Phosphorylation - adding phosphate to a molecule (e.g. ADP is phosphorylated to ATP) Photophosphorylation - adding phosphate to a molecule using light Photolysis - splitting of a molecule using light energy Hydrolysis - splitting of a molecule using water (e.g. ATP is hydrolysed to ADP) Reduction - gaining electrons, may also have gained hydrogen or lost oxygen Oxidation - losing electrons, may also have lost hydrogen or gained oxygen The oxidation of one molecule always involves reduction of another |
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What is photosynthesis? |
The process by which energy from light is used to break apart H2O molecules. Hydrogen is then stored in glucose, which is formed when hydrogen is combined with CO2. Oxygen is formed and released during this process Captured sunlight energy and converts it into chemical energy in the form of carbohydrates which are then used by plants in metabolic processes |
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What is the overall equation of photosynthesis? |
6CO2 + 6H2O + ENERGY ===> C6H12O6 + 6O2 Carbon dioxide, water and energy produces glucose and oxygen |
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How is glucose used in plants? |
Either used up in respiration for energy, stored as starch, or used to make cellulose for the cell wall of the plant |
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Leaf adaptations |
Arrangement of leaves - minimises overlapping for maximum light exposure Numerous stomata - for efficient gas exchange Network of xylem vessels - brings water to the leaves for photosynthesis Air spaces in lower mesophyll - allows diffusion of gases into the photosynthetic mesophyll cells Transparent cuticle - collects as much sunlight as possible Thin - most light is absorbed in the first few mm of the leaf to keep the diffusion pathway short Long narrow upper mesophyll cells with many chloroplasts - maximises amount of sunlight trapped for photosynthesis Large surface area - collects as much sunlight as possible |
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Describe the structure of a chloroplast |
Double membrane - outer is permeable to O2 and CO2. Inner contains transporter molecules that regulates movement of substances into and out of the cell Thylakoids - disc shaped structures in stacks (grana). Chlorophyll is embedded in the thylakoid membrane. Large SA for maximum absorption of light energy Thylakoid lumen - space enclosed by thylakoid membrane. Contains enzymes for photolysis Stroma - the liquid filled space in the chloroplast. Contains enzymes needed for light dependent reaction Thylakoid membranes - system of flattened interconnected fluid filled sacs. Embedded with proteins used in LDR |
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What effect does wavelength have on the energy carried? |
Longer = less energy Shorter = more energy |
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What is used up in the light dependent reaction? What are the products? |
Light and water are used. NADPH and ATP are the products Oxygen is a waste product |
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What is used in the light independent reaction? |
NADPH, ATP and CO2 are used Glucose is produced |
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What is the summary of the LDR? |
Converts solar energy into chemical energy in the form of NADPH and ATP, which are used in the LIR to fuel the assembly of glucose molecules |
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How is ATP produced? |
When glucose is broken down energy is released and used to make ATP. ATP is synthesised by the phosphorylation of ADP using energy from an energy releasing reaction. The energy is stored in the phosphate bond. When energy is needed the phosphate bond is broken via hydrolysis, leaving ADP and inorganic phosphate again. |
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What is a coenzyme? |
A molecule that aids the function of another enzyme. They work by transferring a chemical group from one molecule to another E.g. NADP transfers hydrogen from one molecule to another |
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What is a photosystem? |
The combination of a photosynthetic pigment (coloured substances in chlorophyll that absorb light energy for photosynthesis) and a protein. They are attached together in thylakoid membranes |
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Which two photosystems are used by plants? Which wavelengths of light do they absorb? |
Photosystem I - absorb light best at 700 nm wavelength Photosystem II - absorbs light best at 680 nm wavelength |
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Where do the light dependent and light independent reactions occur? |
Light dependent reaction happens on the thylakoid membranes. Light independent reaction happens in the stroma |
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What is the electron transport chain? |
A chain of proteins through which excited electrons flow, composed of electron carriers and the photosystems |
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Describe the process of the LDR |
1) Photosystem 2 absorbs light energy, causing electrons in chlorophyll to become excited. They gain energy and move along the electron transport chain to photosystem 1 2) When the electrons leave PS2 they are replaced by electrons from water. A water molecule is split via photolysis into protons (H+ ions), electrons and oxygen 3) The excited electrons lose energy as they go along the electron transport chain. The energy is used to transport protons into the thylakoids so that the thylakoid has a higher concentration of protons than the stroma. When they move down the concentration gradient into the stroma again using the enzyme ATP synthase, energy is produced. This energy combines ADP and inorganic phosphate to make ATP 4) Light energy is absorbed by PS1, exciting the electrons even more. They are transferred to NADP along with a proton from the stroma to form NADPH
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What process are ATP, NADPH and O2 produced by? What is cyclic photophosphorylation? What does it produce? |
Non-cyclic photophosphorylation Cyclic photophosphorylation only uses PS1. Cyclic because the electrons aren't passed on to NADP but "cycled" back to PS1 by electron carriers. Only produces small amounts of ATP |
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Describe the process of the light independent reaction |
1) Fixation - CO2 and ribulose bisphosphate are combined, catalysed by the enzyme rubisco. 6C2P, an unstable intermediate, is formed, which splits into 2 GP molecules (3C1P) 2) Reduction - ATP is hydrolysed to provide energy to reduce GP into GALP. H+ ions are also taken from NADPH in the reduction, turning it back to NADP. GALP is then either converted into useful compounds like glucose or stay in the cycle. 3) Regeneration - The GALP that stays is used to regenerate ribulose bisphosphate. 5 out of every 6 GALP molecules are used for this. The inorganic phosphate from any remaining ATP molecules is given to ribulose phosphate to make ribulose bisphosphate in a phosphorylation reaction |
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What else can the Calvin cycle be used to make? |
Carbohydrates Lipids Amino acids Nucleic acids |
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Steps of the investigation to test the rate of the Hill reaction |
1) grind leaves into pieces with a pestle and mortar, removing any stalks. Add chilled isolation solution and continue to grind 2) filter the liquid into a beaker through a funnel lined with muslin cloth. Centrifuge the liquid at high speed for 10 minutes to separate the chloroplasts from the rest of the liquid 3) drain away the rest of the liquid and re-suspend the chloroplasts in fresh chilled isolation medium. Store in ice for the rest of the experiment. 4) set up a colorimeter to measure the absorbance of each solution, making sure to zero it with a cuvette filled with water first 5) set up a test tube rack a set distance away from a bench lamp. Put a test tube containing a set volume of chloroplast extract and DCPIP into the rack and expose the solution to the light source for 10 minutes 6) take a sample of the solution and record its absorbance every 2 minutes. Repeat the experiment two more times |
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What results should be observed from the Hill reaction? |
The absorbance will decrease as the DCPIP gets reduced and loses its blue colour. The faster the absorbance decreases the faster the rate of the Hill reaction. |
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Why is about 60 percent of energy never taken in by organisms? |
Plants cant use all of the light energy that reaches their leaves: wrong wavelength gets reflected passes straight through the leaves Some light hits parts of the plant that can't photosynthesise Some parts of food aren't eaten by organisms so the energy isn't taken in Some parts of food are indigestible and come out as faeces |
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What is the gross productivity? |
The amount of available energy taken in by an organism |
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What is net productivity? |
The amount of the gross productivity that becomes biomass. Also the amount of energy available to the next trophic level |
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How do you calculate net productivity? |
Gross productivity - respiratory loss |
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How do you calculate the percentage efficiency of energy transfer? |
(Net productivity ÷ energy received) × 100 |
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What are NPP and GPP? |
Net primary productivity and gross primary productivity. Net productivity and gross productivity, just for producers |
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How is net primary productivity calculated? |
NPP= GPP - plant respiration |
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How do you measure the energy transfer between trophic levels? |
Calculate the difference between the amount of energy in each level (the net productivity in each level) |
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What is climate change? |
The term used to describe a significant change in the weather of a region over a period of several decades. It includes natural variations in climate but is commonly used to refer to changes caused by humans |
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What are the different sources of evidence for climate change? |
Temperature records Dendochronology Pollen in peat bogs Antarctic ice cores |
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How can pollen in peat bogs be used to show how temperature has changed? + other pollen facts |
Pollen is preserved in peat bogs. Only anaerobic bacteria can survive in them so organic material is only partially decayed Peat bogs accumulate in layers so the age of pollen increases with depth Scientists can take cores from peat bogs and extract pollen to identify what plants they came from The plants indicate what sort of climate there was when they were around Goes back up to 15000 years Bog beetles give a more precise measure of climate change as insects respond faster to changes in climate than plants |
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What is dendochronology? How can it be used to prove climate change? |
Dendrochronology is a method for figuring out how old a tree is using tree rings. One ring (new layer of xylem vessels) is produced a year - the warmer the environment, the thicker the ring. Cores can be taken and then dated to see what the climate was like each year Cores from trees of the same species from the same area can be lined up to see what the temperature was like further back (if one tree is older than the other) Hundreds to thousands of years in the past |
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How can Antarctic ice cores be used as evidence for climate change? |
They contain air, water, remnants of living things and sediment. The oxygen and CO2 composition gives a picture of what the atmosphere at the time The amount of CO2 dissolved in it also gives away the temperature. Warmer temperature = more CO2 dissolved
The ratio of different oxygen isotopes in trapped air is measured to give an estimate of the average air temperature when the ice was formed CO2 concentration of air can also be determined from the bubbles |
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Why has CO2 increased in the atmosphere? |
More fossil fuels are being burned which releases CO2 Natural sinks like forests are being destroyed |
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Why is methane increasing in the atmosphere? |
More fossil fuels are being extracted There's more decaying waste More cattle farming Methane can also be released from natural stores like frozen ground. When temperature increases these will thaw and methane will be released |
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Why are models of the future climate based on extrapolated data limited? |
We dont know how greenhouse gas emissions will change We dont know how much each emissions scenario will make they global temperature rise by The change in the atmosphere due to natural causes is unknown We dont know what attempts to manage greenhouse gases there will be or how effective they will be |
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How will increasing global temperatures affect organisms' life cycles? |
Your metabolism is all the chemical reactions that take place in cells to keep you alive. They are controlled by enzymes so an increase in temperature will mean that reactions in some organisms speed up, increasing rate of growth. They will develop and progress through their life cycle faster The temperature may be too high for other organisms - their metabolic processes will slow down, so their rate of growth will decrease and their lifecycle will be slower |
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How will global warming affect distribution? |
All species exist where their ideal conditions are. When these change they will have to move, and if they can't they will die out in that area |
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What effect will changing rainfall patterns have? |
Some areas will get more/less rain than others. This will affect the development and lifecycles of some organisms, as well as their distribution |
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How will changing seasonal cycles affect organisms? |
The timing of the seasons may be changing due to global warming. Organisms are adapted to the timing of the seasons and the changes that occur. Changing seasonal cycles will affect the lifecycles, development and distribution of organisms |
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Describe the carbon cycle |
1) Carbon in the form of CO2 is absorbed by plants when they carry out photosynthesis and becomes carbon compounds in plant tissues 2) Carbon is passed on to animals that eat plants and to decomposers when they eat dead organic matter 3) The carbon is returned to the atmosphere via respiration 4) If any dead organic matter isn't decomposed (if it ends up in the sea or in bogs) the carbon compounds can be turned into fossil fuels over millions of years 5) carbon fuels are burnt - combustion |
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Biofuels are fuels produced from biomass. Often made from crops which can be replanted after harvesting, so it is sustainable Burned to release energy which produces CO2 No net increase in atmospheric CO2 - the amount of CO2 produced from burning is the same as is taken in when it grows |
Reforestation - planting of new trees in existing depleted forests More trees means more CO2 is removed from the atmosphere CO2 is converted into carbon compounds and stored as plant tissues in the trees |
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What is evolution? |
A change in the frequency of an allele in the gene pool of a population over time. It occurs due to natural selection |
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Describe natural selection |
Individuals vary within a population because they have different alleles due to gene mutations Therefore some are better adapted to their environment than others More likely to survive, reproduce and pass on advantageous alleles than others without it Greater proportion of the next generation inherit the allele They are also more likely to survive, reproduce and pass on the allele Frequency increases from generation to generation |
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What is a species? What is speciation? |
A group of similar organisms that can reproduce to give fertile offspring Speciation is the development of a new species |
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How does isolation lead to speciation? |
When populations of the same species become reproductively isolated gene flow (transfer of genes) is reduced between them. Natural selection then acts on the populations separately, so new species can develop |
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Why might reproductive isolation occur? |
Geographical isolation (allopatric speciation) or because random mutations produce changes in phenotype that prevent populations from mating (sympatric speciation) |
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Describe the process of allopatric speciation |
Populations of the same species become geographically separated and experience slightly different conditions As a result of different selection pressures the populations will have different changes in allele frequencies Differences accumulate in the gene pool of the two populations, resulting in changes in phenotype frequencies Eventually the populations become genetically distinct, and be unable to reproduce with each other to produce fertile offspring |
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What is allopatric speciation? What is sympatric speciation? |
Speciation due to geographical isolation
Speciation without geographical isolation, occurs due to mutations |
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What changes in alleles and phenotypes prevent populations from breeding successfully? |
Seasonal changes - individuals from the same pop become sexually active at different times of year Mechanical changes - changes in genitalia prevent mating Behavioural changes - a group of individuals develop courtship rituals that aren't attractive to the main population |
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What is polyploidy? How can it lead to speciation? |
When mutations occur that increase the number of chromosomes found in cells. More common in plants Individuals with different numbers of chromosomes can't reproduce. Polyploid organisms often reproduce asexually. Only leads to speciation if it doesn't prove fatal to the organism and more can be produced |
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What is genomics? How is it useful? |
A branch of science that uses DNA technology to determine the base sequence of an organism's genome and the functions of its genes. Allows us to compare the DNA of organisms |
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When comparing the DNA of organisms, how can you tell if they are closely or distantly related? |
Closely related species diverged more recently, so there should be more similarities in DNA as less time has passed for changes in the DNA sequence to occur |
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What is proteomics and how does it show which organisms are closely related? |
The study of proteins. Related organisms have similar DNA sequences and so similar amino acid sequences in their proteins. Organisms that have diverged from each other more recently have more similar proteins and less time has passed for changes to occur |
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What are the three main ways that scientists share their research? |
Scientific journals Peer review Conferences |
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How do scientific journals ensure validity of experiments? |
Scientists publish articles in them to describe their work. Other scientists can repeat the experiment to see if they get the same results using the same methods. If the results can be replicated over and over again the evidence is very likely to be reliable |
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How does peer review validate evidence? |
Write ups have to go through the peer review process before they can be published Other scientists who work in the same field read and review the work to make sure that the conclusions made from the evidence are valid and that experiments are carried out to the highest standard possible |
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How do conferences allow scientists to share info? |
They can present their findings and have a Q and A afterwards Fast and easy way to share theories and discuss evidence |
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