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53 Cards in this Set
- Front
- Back
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Classification systems |
Process by which living organisms are sorted into groups
The organisms within each group share similar features 7 taxonomic groups ordered in a hierarchy The 7 groups are kingdom, phylum, class, order, family, genus and species Kingdoms are the largest and broadest group with species being the smallest most specific classification Similar groups are combined into more inclusive groups at a higher level Based on recent studies of genetic material can add a further level of classification 3 domains placed at the top of the hierarchy |
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Classification order picture |
picture |
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Why classify organisms? |
To identify species - by using a clearly defined system of classification the species an organism belongs to can be easily identified
To predict characteristics - if members of the same group have the same characteristics then another species with the same characteristic likely to be in the same group To find evolutionary links - share characteristics as evolved from a common ancestor Can be used worldwide |
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How are organisms classified? |
Separate into domains
Fewer in each group as move down and organisms become more similar Smallest group is species and defined as a group of organisms that are able to reproduce to produce a fertile offspring |
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Naming organisms |
Have a common name but not international
Use binomial nomenclature to name organisms across all languages A scientific name consisting of 2 parts First word is genus called the generic name Second word is species called the specific name No two species have the same generic and specific name Normally write in italics or underlined in handwriting First letter of genus uppercase but rest lowercase Such as Homo sapiens |
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Five kingdoms |
Prokaryotae
The eukaryotes Protista ( unicellular eukaryotes) Fungi (e.g. yeast, mushrooms, mould) Plantea Animalia |
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Prokaryotae |
Such as E. Coli
Unicellular No nucleus or other membrane-bound organelles - naked DNA and small ribosomes No visible feeding mechanism - nutrients absorbed through the cell wall or produced internally by photosynthesis |
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Protoctista |
Such as Amoeba
Mainly unicellular A nucleus and other membrane-bound organelles Have some chloroplasts Some are sessile, but others move by cilia, flagella or amoeboid mechanisms Some by photosynthesis (autotrophic), some ingest other organisms (heterotrophic) or both - some are parasitic |
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Fungi |
Such as mushrooms, moulds and yeast
Unicellular or multicellular A nucleus and other membrane-bound organelles and a cell wall made of chitin No chloroplasts or chlorophyll No mechanisms for locomotion Most have a body or mycelium made of threads or hyphae Nutrients acquired by absorption - mainly from decaying material so saprophytic and some are parasitic Most store their food as glycogen |
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Plantae |
Such as flowering plants, trees and grasses
Multicellular A nucleus and other membrane-bound organelles including chloroplasts and a cell wall made of cellulose All contain chlorophyll Most do not move Nutrients acquired by photosynthesis so autotrophic Store food as starch |
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Animalia |
Such as mammals, reptiles, birds, insects, molluscs, worms, sponges and anemones
Largest kingdom with most species Multicellular A nucleus and other membrane-bound organelles and no cell walls or chloroplasts Move with the aid of cilia, flagella or contractile proteins as muscular organs Acquire nutrients by ingestion, heterotrophs Food stored as glycogen |
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Changes to the classification system |
Changes classification as find out more about organisms
Originally based on observable features but now use of microscopes and study of genetics DNA determines the internal and external features from the proteins that are made Compare similarities between DNA and proteins of different species to see evolutionary relationships Such as different amino acids haemoglobin in humans and chimpanzees and a larger difference to gibbons so shows common ancestry |
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Three domain system |
Domains are a further level of classification at the top of the hierarchy
Use differences in the sequences of nucleotides in the cells’ ribosomal RNA and membranes lipid structure Woese’s three domain system has 3 domains and 6 kingdoms Eukarya - have 80s ribosomes and RNA polymerase has 12 proteins Archaea - have 70s ribosomes and RNA polymerase has between 8-10 proteins Bacteria - 70s ribosomes and RNA polymerase has 5 proteins Prokaryotae kingdom divided into two kingdoms - archaebacteria and eubacteria Both single-celled prokaryotes they have different chemical makeup Such as peptidoglycan in eubacteria cell walls but archaebacteria do not Some use the traditional 5 kingdoms but others use the new 3 domains Archaebacteria - live in extreme environments such as thermal vents, anaerobic conditions and highly acidic environment Eubacteria - found in all environments as bacteria most familiar with |
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Three domain diagram |
picture |
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Phylogeny |
Phylogeny is the evolutionary relationships between organisms
It revels which group of a particular organism is related to, and how close they are Want to develop a classification system that takes into account phylogeny |
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Phylogenetic trees |
A phylogenetic (evolutionary) tree is a diagram to represent the evolutionary relationships between organisms
Branched diagrams to show that different species have evolved from a common ancestor Earliest species found at the base of the tree and most recent species at the tips of the branches Produced by looking at similarities and differences in species physical characteristic and genetics mainly from fossils |
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Phylogenetic trees diagram |
picture |
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Advantages of phylogenetic classification |
Can be done without classification knowledge and can confirm classification Doesn’t have discrete groups where don’t have to put organisms that don’t quite fit into the group Can’t compare different groups in classification but can in phylogenetic |
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Evolution |
Evolution is the theory that describes the way in which organisms evolve or change over many years as a result of natural selection Organisms best suited to their environment are more likely to survive and reproduce, passing on their characteristic to their offspring through their genes Gradually, a species changes over time to have more advantageous phenotypes for the environment in which is lives |
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Darwin |
Carried out observations of finches on the Galapagos Islands Different islands have different finches - they were similar but had different shapes and sizes of beaks and claws The design of the finches beaks were linked to the food available on each island A bird was born with a beak more suited to the food A bird with a suited beak would survive longer than a bird less suited so it would have more offspring to pass on the beak characteristic Wallace working on idea of evolution at the same time and combined papers Darwin published ‘On the Origin of Species’ and named it evolution by natural selection |
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Evidence for evolution |
Paleontology - the study of fossils and the fossil record Comparative anatomy - the study of similarities and differences between organisms’ anatomy Comparative biochemistry - similarities and differences between the chemical makeup of organisms |
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Palaeontology |
Fossils are formed when animals and plants remains are preserved in rocks Over time sediment is deposited ti from layers of rock Different layers correspond to different geological eras to form a sequence from youngest to oldest However, fossil record not complete as many decompose quickly before they have a chance to fossilise and conditions needed not present, many have been destroyed by earth movements or not discovered yet |
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Evidence from the fossil record |
Simplest organisms furthest back in rock layers then leading to more complex so supports that evolved from simple organisms The sequence matches their ecological links to each other such as plant fossils before animals Study similarities in the anatomy of fossils to see how closely related the organisms are such as horse ancestors with one toe per foot Allow relationship between extinct and living organisms But some fossils not found, destroyed or not formed so incomplete |
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Comparative anatomy - homologous structure |
A homologous structure appears superficially different and may perform different functions in different organisms but has the same underlying structure Such as pentadactyl limb of vertebrates Pentadactyl limb used in flying, walking, jumping and swimming but very similar structure with 5 digits Show that all vertebrates evolved from the same structure Provides evidence for divergent evolution when closely related species diversify to adapt to new habitats as a result of migration or loss of habitat |
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Comparative biochemistry |
Study of similarities and differences in the proteins and other molecules that control life processes Some change but others are highly conserved among species Slight changes can help identify evolutionary links Most studied are cytochrome c, a protein for respiration, and ribosomal RNA Neutral evolution where the variability occurs outside of the molecule’s functional region so don’t affect function and are neutral So they have no effect on natural selection To see how closely related look at the molecular sequence of a particular molecule in both organisms and the order of bases in DNA or order of amino acids in proteins The number of differences is plotted against the rate the molecule undergoes neutral base pair substitution to estimate the point where they shared a common ancestor Closely related have more similar DNA Ribosomal RNA has a very slow rate of substitution so commonly used with fossil information between ancient species |
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Types of variation |
Variation is the differences in characteristic between organisms Wildest type of variation is between members of different species - interspecific variation Every organism in the world is different Differences between organisms within a species are called intraspecific variation such as height, hair colour, intelligence |
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Causes of variation |
An organism’s genetic material - differences in the genetic material an organism inherits from its parents leads to genetic variation The environment in which the organism lives - this causes environmental variation |
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Genetic causes of variation |
Alleles - different versions of the same gene that produce different characteristics such as alleles for different blood groups. Different individuals inherit different combinations of alleles Mutations - changes to DNA sequence so changes in the proteins that they code for. The protein changes may affect physical and metabolic characteristics. If mutation occurs in gametes then the offspring also has variation Meiosis - gametes are genetically different from each other from independent assortment and crossing over so offspring shows variation Sexual reproduction - inherits genes from both of its parents so offspring differs from the parents. Less variation in asexual reproduction Chance - chance as to which two gametes combine as random fertilisation so differ from siblings |
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Environmental causes of variation |
All organisms affected by their environment although plants more as they lack mobility Such as a plant that grows in the sun will grow larger than a plant in the shade Presence of scars as not inherited |
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Environmental and genetic causes |
Most variation from a mixture of environmental and genetic factors Such as height as genetic but also controlled by diet and also skin colour and sun exposure Difficult to conclude what is affecting what |
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Discontinuous variation |
A characteristic that is only in certain values is discontinuous (discrete) variation No in-between values and qualitative Purely determined by genetic factors, usually a single gene Such as eye colour and shape of bacteria Normally shown as a bar chart |
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Continuous variation |
A characteristic that can take any value within a range is continuous variation Graduation from one extreme to the other - a continuum and quantitative Such as height and mass Controlled by a number of genes (polygenes) so not just one and also influenced by environmental factors Collected on a frequency table and then plotted on a histogram and a curve normally shows the trend |
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Normal distribution cures |
Continuous data on a graph usually result in a bell-shaped curve The data is said to be normally distributed The mean, median and mode are the same Bell shaped and symmetrical around the mean 50% of values above the mean and 50% less than the mean Most values near the mean with few extremes |
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Normal distribution curve picture |
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Standard deviation |
The measure of how far spread out the data is The greater the standard deviation, the greater the spread of the data Normal distribution standard deviation usually have: 68% of values are within 1 standard deviation of the mean 95% of values are within 2 standard deviations of the mean 99.7% of values are within 3 standard deviations of the mean |
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Student's t test |
Used to compare the mean values of two sets of data Must be normally distributed and have enough data for a reliable mean Produce a null hypothesis before |
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Student's t test calculation |
Used to compare the mean values of two sets of data Must be normally distributed and have enough data for a reliable mean Produce a null hypothesis before |
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Standard deviation calculation |
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Correlation coefficient |
Between 2 sets of data No correlation - no relationship between the data Positive correlation - as one set of data increases in value, the other set of data also increases in value Negative correlation - as one set of data increases in value, the other set of data decreases in value |
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Correlation picture |
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Spearman's rank |
To calculate correlation coefficient Data for the two variables should be rank ordered from lowest to highest and to in table If two the same such as 1 and 2 use both as 1.5 If +1 then perfect positive correlation, -1 then perfect negative correlation and 0 no correlation and look up on critical values table using n as number of data pairs |
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Spearman's rank calculation |
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Adaptations |
Adaptations are characteristics that increase an organism’s chance of survival and reproduction in its environment Anatomical adaptations - physical features (internal and external) Behavioural adaptations - the way an organism acts (inherited or leant from parents) Physiological adaptations - processes that take place inside an organism |
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Anatomical adaptations |
Body coverings - scales, spines, feathers and shells such as to help fly, keep warm or protection Camouflage - colour blends into the environment so hard for predators to spot it such as snowshoe hare which is white in winter and brown in summer Teeth - shape and type of teeth depend in the animal’s diet. Herbivores molars for tough grass and carnivores sharp to tear meat Mimicry - so a harmless organism fools predators into thinking that it is poisonous or dangerous |
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Marram grass |
On sand dunes and is a xerophyte so adapted to live in an environment with little water Adaptations to reduce the rate of transpiration Curled leaves to minimise surface area exposed to air and wind Hairs on the inside of the leaves to trap moist air to reduce diffusion gradient Stomata sunk into pits so less likely to open A thick waxy cuticle on leaves and stem to reduce water loss by evaporation |
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Behavioural adaptations |
Survival behaviours - playing dead or rabbits freeze when they think they have been seen Courtship - to attract a mate to increase chance of reproducing Seasonal behaviours - migration for climate or food and hibernation to conserve energy when limited food Behavioural adaptations can be innate, ability inherited through genes, or leant from observing other animals Many behavioural adaptations are a mixture of innate and learned |
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Physiological adaptations |
Poison production - kill prey and protect themselves Antibiotic production - bacteria produce to kill other bacteria around them Water holding - cacti and water-holding frog so a year in the desert without water |
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Convergent evolution |
Analogous structures - adapted to perform the same function but have a different genetic origin such as fish and whale tail fins Convergent evolution when two unrelated species begin to share similar traits The similarities evolve because they organisms adapt to similar environments Organisms from different taxonomic groups show similar anatomical features Such as marsupial and placental mammals - marsupials start in uterus then leave and enter marsupium (pouch) to complete development. They both have similar shape, type of locomotion and feeding techniques such as marsupial and placental mice Flying phalangers and flying squirrels both gliders that eat insects and plants Marsupial and placental moles - both burrow through soil to ding worms and grubs, have a streamlined body shape and modified forelimbs for digging, velvety fur for smooth movement through soil. Marsupial is white to orange and placental grey |
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Natural selection |
Organisms within a species show variation in their characteristics caused by genes and mutation Organisms whose characteristics are best adapted to a selection pressure in the environment, have an increased chance of surviving and successfully reproducing. Less well-adapted organisms die or fail to reproduce so survival of the fittest Successful organisms pass the allele for the advantageous characteristic onto their offspring and non-advantageous alleles not passed on Repeated for many generations so proportion of the advantageous adaptation increases Can lead to the evolution of a new species |
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Evolution of antibiotic resistant bacteria |
MRSA has developed resistance to many antibiotics Bacteria reproduce very rapidly so evolution happens fast A mutation in some provided resistance so these individuals became resistant and survived to pass on the allele where non-resistant died |
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Peppered moths evolution |
Before industrial revolution, most where pale coloured so camouflage against light-coloured tree bark so increased chance of survival and dark ones killed During the industrial revolution the trees became darker as soot and killed the lichen so dark moths now better adapted to the environment and were more likely to survive and white moths more visible so more killed Clean Air Act so now light coloured so suit pale moths |
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Sheep blowflied |
Sheep blowflies lay their eggs in faecal matter around a sheep’s tail and larvae hatch and cause sores and fatal if untreated Pesticide sued to prevent the condition but quickly gained resistance in 6 years Was fast as pre-adaptation where an existing trait is advantageous to a new situation |
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Flavobacterium |
Most evolution as a negative result of selection pressures but flavobacterium evolved due to opportunities in their environment New flavobacterium living in wastewater from factories that produce nylon 6 so evolved to digest nylon 6 Help clear up factory waste and bacteria have another source of nutrients Use new enzymes nylonases |
