Evolution and Classification

Evolution and Classification

1. extinction;this is when no living individuals of a particular species remain/exist.the species is then said to be extinct

   • why do species become extinct?
     • 1) the environment changes
       • 2)A new predator kills them all
         • 3)A new disease kills them all
           • 4)they cant compete with new species for food
             • 5)a catastrophic event kills them all

2. Speciation: over a long period of time, the phenotype of a particular organism can change so much because of natural selection, that a totally different species is created

   • isolation happens when a population of the same species becomes separated.physical barriers geographically isolate some individuals from the main population e.g.earthquakes and floods could potentially create a barrier

3. Evolution:the theory of evolution states that All of today's species have evolved from a single life form that first started to develop over 3 BILLION YEARS AGO!!

   • CHARLES DARWIN:he came up with an IMPORTANT theory on evolution..He used new knowledge on fossils and geology to suggest the theory of evolution by natural selection .it works like this:
     • NEW DISCOVERIES: darwins theory wasnt perfect .as there wasnt any relavant scietific knowledge available at the time, he couldn't give a good explanation of why new characteristics appeared or even exactly how individual organisms passed on beneficial adaptations to their offsprings
       • we now know that phenotypes are controlled by genes.new genetic variants arise because of changes/mutations in the gene and these genetic variants can give rise to phenotypes that are suited in the environment .Beneficial genetic variant are passed onto future generations in the DNA that the parents will contribute to their offsprings
       • these new discoveries have helped scientists to develop Darwins original idea of evolution by natural selection which is accepted today
         • evolution by natural selection
           • 1)individuals within a species show a phenotypic variation(variation in characteristic) due to a mix of genetic variants present in the population e.g.some rabbits have big ears and some have small ears. this variation is due to a wide range of alleles
           • 2)some genetic variants give rise to the characteristics that are best suited in that environment so will have abetter chance of survival and breed successfully e.g. big-eared rabbits are likely to hear the approaching fox and are likely to survive and have lots of offspring.the small eared rabbit are most likely going to get eaten.
           • 3)these genetic variants are responsible for the useful characteristics and are more likley to be passed down to the next generation
           • over time the genetic variants for a useful characteristic will become more accumulate/common in the population,further leading to a change in species.the changing of inherited characteristics of a population overtime is EVOLUTION.
     • there is so much evidence for darwins theory NOW.along with the discovery of genetics other evidence was found in FOSSILS of different ages, allowing you to see how changes in organisms develop slowly over time.
   • 1)all the individuals of a particular species show a wide range of variation for a particular characteristic
   • 2)due to the range of variation in characteristics, some species may be suited to the environment than others.
   • 3)the individual that are most suited to the environment are likely to survive therefore breed more successfully
   • 4)the useful characteristic will be passed onto the offspring

4. variation: DIFFERENCS BETWEEN MEMBERS OF THE SAME/DIFFERENT SPECIES

   • GENETIC VARIATION: characteristics determined by genes
   • ENVIRONMENTAL VARIATION: how the environment has an impact on growth etc.
   • GENETIC AND ENVIRONMENTAL VARIATION:some characteristics are determined by genetic and environmental factos
     • HEIGHT:mas height that an organism can grow to is determined by the genes.but whether is actually grows that tall is determined by the environment e.g. food intake
       • intelligence:IQ can be determined by genes but depending on whether you get there is environmental e.g. school life /upbringng
         • HEALTH:you are likely to get a disease because of your genes but your lifestyle affects the risk of getting that disease which is environmental e.g. smoking/junk food intake etc
   • MUTATION: a change in an organisms DNA.they occur continuously.a gene as a matter of fact CAN mutate
     • this is when a gene is altered .which produces a genetic variant/different form of the gene.as the gene codes for the sequence of amino acids that make up a protein,gene mutation sometimes leads to changes in the protein that it codes for.
     • some mutation has little to no affect on the protein the gene codes for, therefore, most mutations have no affect on the organisms phenotype/characteristic

5. SELECTIVE BREEDING: when humans artificially select the plants or animals that they are going to breed so that the genes for the particular characteristics remain in the population.

   • organisms are selectively bred to develop features that are useful/attractive e.g. animals that produce more milk/meat,crops with disease resistance,dogs with a good gentle temperament and decorative plants with big/unusual flowers
   • 1)from your existing stock,select the ones that have the characteristics that you are after
     • 2)breed them with each other
       • 3)select the best of the offspring and breed THEM together
         • 4)continue this process over several generations and the desirable trait will get stronger.in the end all the offspring will have the characteristics that you are after
   • in agriculture, selective breeding an improve yield.
     • fat cows will breed and over the next generations, the cows will have a high meat yield as they are fat
   • disadvantages of selective breeding
     • reduces the gene pool/the number of different alleles in a population . this is because the farmer keeps breeding from the best animals or plants ,which are closely related .this is known as INBREEDING
       • inbreeding causes health problems because there's a higher chance for the organism to inherit harmful genetic defects when the gene pool is limited e.g some dog breeds are particularly susceptible to certain defects due to inbreeding e.g. pugs often have breathing problems
     • if a new disease came by an killed one of them, then because the stock are closely related, the others will most likely succumb to it

6. GENETIC ENGINEERING

   • TO TRANSFER A GENE RESPONSIBLE FOR A DESIRABLE CHARACTERISTIC FROM ONE ORGANISMS GENOME INTO ANOTHER ORGANISM SO THAT IT HAS THE DESIRABLE CHARACTERSITIC
     • THIS IS DONE BY 'CUTTING OUT' THE DESIRABLE GENE AND TRANSFERRING IT INTO THE CELLS OF ANTHER ORGANISM
       • 1)a useful gene is isolated/cut from one organisms genome using ENZYMES and is inserted into a vector
         • 2)a vector is usually a virus or a bacterial plasmid -small rings of DNA depending on the type of organism that the gene is being transferred to.
           • 3)when the vector is introduced to the target organism, the useful gene is inserted into its cells
   • uses
     • 1)bacteria has been genetically modified to make human insulin that can be used to treat diabetes
       • 2)genetically modified (GM) crops have had their genes modified e.g to improve size/quality of fruit/make them resistant to disease, insects or herbicides(chemicals used to kill weeds)
         • researching genetic modification treatment for inherited disorders caused by faulty genes e.g gene therapy:inserting working genes into people with the disorder
           • sheep have been genetically engineered to produce substances like drugs in their milk that can be used to treat human diseases
   • issues
     • some people worry about long term effects of genetic engineering -that changing someones genes may cause unplanned problems that may be passed onto future generations
       • issues surrounding genetically modified crops:
         • benefits
           • characteristics increase yields=more food
             • living in developed nations may lack nutrients in their diet.GM crops may be engineered to contain the nutrients that missing e.g. golden rice contains beta-carotene.lack of this substance causes blindness
         • concerns
           • said by some peopl:affect the number of wild flowers=reducing farmland biodiversity
             • not everyone is convinced that they are safe and some people are concerned that we might not fully understand the effect it may have on the human health-some are concerned that they may get allergies
               • the transplanted genes may get into the natural environment e.g the herbicide resistant gene may be picked up by the weeds creating a new 'superweed' variety.

7. FOSSILS

   • fossils re the remains of organisms many years ago.they provide evidence of organisms that lived ages ago..it also shows how organisms have changed overtime.you can see how simpler they are now compared to how they were by looking at their fossils
   • from gradual replacement by minerals :teeth shells and bones do not decay easily and so last much longer.eventually they are replaced by minerals as they decay, forming a rock like substance shaped like the original hard part
   • from casts and impressions: sometimes fossils are formed when an organism is buried in soft rock=clay.the clay hardens around the organisms decay leaving a cast of itself.e.g. footprints can be pressed into soft materials leaving an impression of itself when the material hardens
   • preservation in places where no decay happens: microbes in decay need the right conditions to break down material-plenty of Oxygen,enough moisture,right temp and pH for enzymes to work properly.if conditions aren't right,decay wont take place and the organism will remain preserved
   • why is there a lack of evidence...
     • scientists believe many early organisms wrere soft bodied-soft tissue tend to decay away easily without forming fossils
       • fossils that formed may have destroyed by geological activity e.g. the movement of tectonic plates may have crushed fossils already formed in the rock
         • so...fossil record is incomplete and we havent got the fossils of every type of organism that lived

8. Antibiotic resistance

   • when there is a mutation in the bacteria;s characteristics, it leads to a antibiotic-resistant strain forming as the gene for the antibiotic resistance becomes more common in the population
   • a bacterium can resist antibiotics and so it can live longer and reproduce many more times=increasing population size of the antibiotic-resistant strain
   • these strains are a problem to people who become infected by this bacteria as their body doesn't recognise it and there is no effective treatment so the infection spreads easy
   • sometimes drug companies can create a drug to treat these resistant strains but they are becoming more and more common
   • the use of antibiotic resistance is getting worse, due to overuse or inappropriate use e.g. doctors prescribing for non-serious problems
   • its important to take antibiotics even after you think you are feeling better as it reduces the risk of antibiotic resistant bacteria emerging
   • in farming, antibiotics are given to animals to make them better or grow faster.this leads to antibiotic resistant bacteria in the animal which could spread to humans during meat preparation/consumption..increasing concern on the overuse of antibiotics in agriculture as it has lead to some countries restricting their use.
   • the increase in antibiotic resistance has resulted in drug companies developing new antibiotics that are effective against the resistance strains..its a costly process and the development is real slow so we need to be able to keep up with the demand for new drugs as more antibiotic resistant strains develop and spread

9. classification: the linnaean system: was invented by Carl LInnaeus 1970's ,which grouped living things according to their characteristics and the structure that makes them up

   • three-domain system: in 1990 was invented by Carl Woese ,using evidence gathered from chemical analysis techniques=RNA sequence analysis,he found that in some cases, species thought to be closely related in tradition classification systems are in fact not as closely related as first thought n
     • 1)Archea :organisms in this domain are primitive bacteria.they are found in extreme places such as hot springs /salt lakes
     • Bacteria:: this domain contains true bacteria e.g. E.coli and staphylococcus.Although they often look similar to Archaea ,they are lots of biochemical differences between them
     • Eukaryota:This domain contain a broad range of organisms such as fungi,plants animals and protists .these are then subdivided into smaller groups kingdom,phylum,class,order,family,genus,species.
   • the binomial system:where every organism is given its own two part Latin name.
     • used worldwide and means that scientists in different countries or speak different languages all refer to a particular species by the same name-avoiding confuson
   • Evolutionary trees show how scientists think different species are related to each other
     • they show common ancestors and relations between species.the more recent the common ancestor, the more closely related the two species are-and the more charactristics they are likely to share
       • scientists analyse different types of data to work out evolutionary relationships. For livng organisms,theyuse the current classification data e.g. DNA analysis and structural similarities. for extinct species, they use information from the fossil record