CB4- Natural Selection And Genetic Modification Flashcards
What is variation within species?
- variation is when organisms have different phenotypes (observable characteristics) due to their differing genotypes and environmental factors that they have lived with
How does genetic variation occur?
- your genome is all the genes that make up your body. Genes code for specific amino acids which in turn codes for particular proteins that will have specific functions
- genetic variation occurs due to mutations, the change in the DNA code can change the amino acids, therefore changing the protein it codes for
- everyone in the world will have a different, unique genome (apart from identical twins) meaning they will have a different combination of proteins, making them look physically different, environment can also affect the phenotype.
What effects do mutations have on organisms?
- most mutations within genes do not have a large effect on phenotype, but sometimes it can alter a characteristic
- while some mutations have undesirable effects like diseases and illnesses, some can actually be beneficial and give an organism desirable traits that can help them survive selection pressures (things like predation, change in climate, lack of food etc.)
What are selection pressures?
- factors that affect an organisms chance of surviving and reproductive
- these are things like predation, competition for resources and diseases
Describe natural selection/ survival of the fittest
- due to mutations arising within a population, there will be genetic variation amongst its members, some will have specific characteristics that make them better adapted to selection pressures. For example if there was a lack of food, taller giraffes would be able to reach higher trees while the shorter ones would starve.
- when these changes in environment/ environmental pressures are introduced, the better adapted organisms whose genetic variation that gives them desirable characteristics will survive while the disadvantaged ones will die and not be able to pass on the disadvantageous trait.
- the surviving organisms would then survive and be able to reproduce successfully, the alleles that are responsible for the beneficial characteristics will then most likely be passed on to offspring and this trait would become more common overtime
Who theorised natural selection and evolution
Charles Darwin
Why is genetic variation so important?
- genetic variation is extremely important in a population
- this is because if all member of the same population had the exact same genome, selection processes like a disease would immediately wipe them all out leaving no surviving organisms
- because of genetic variation, if a selection pressure were to be brought to a population those with the beneficial traits that allow them to survive this pressure will live and be able to reproduce, allowing the species to continue existing.
- this will also allow offspring to carry the desirable allele making sure that if the environmental change were to occur again, the whole population would be able to survive
What is evolution?
- when natural selection occurs over and over again, causing a slow and continuous change in the organism’s characteristics over time, giving them phenotypes that are best suited for the environment
- eventually a new species will evolve with the individuals having better adapepyed characteristics
Explain the GENIE acronym for evolution.
- G- genetic variation - the characteristics of organisms within a population are different due to mutations and overall differences in genomes
- E- environmental pressure - conditions will change and selection pressures will be introduced, increasing competition between organisms
- N- natural selection - natural selection will run its course and the better adapted species with the beneficial characteristics will survive the environmental pressure while the disadvantageous ones will die
- I- inheritance - the better adapted survivors will pass on their beneficial alleles to their offspring who will gain the adaptations and also survive the selection pressure
- E- evolution - if the environmental conditions remain, natural selection will continue to occur over and over again and a new species will eventually evolve with all its members having beneficial characteristics
Describe the evolution of woolly mammoths and elephants.
- woolly mammoths and elephants evolved from the same animal (they share a common ancestor)
- an area where this ancestor lived began to get colder
- due to genetic variation, some animals had hairier skin and were more likely to withstand the cold temperatures and survive especially when food was scarce
- the organism with less hair would ultimately freeze to death, especially with a lack of food because there would be no way to generate body heat
- the surviving hairy animals would then survive and breed, giving them beneficial characteristic to offspring
- over time the organism would become more hairy forming a new specie
- this is an example of evolution that takes place over a long course of time.
Describe the evolution of rats and warfarin rat poison.
- in the 1940s and 50s a substance called warfarin was used to poison rats
- upon its introduction many rats died but in 10 years most of the rats became immune to the warfarin
- this was due to genetic variation, there were some rats that had alleles that made them resistant to the poison
- these rats then underwent survival of the fittest where the warfarin resistant rats survived and were left to reproduce offspring that also carried these alleles for poison resistance, eventually creating a resistant rat population
- this is an example of faster evolution.
Describe the evolution of antibiotic resistant bacteria.
- bacteria are able to develop random mutations in their DNA creating new alleles which can affect the bacteria’s characteristics eg. An allele for antibiotic resistance
- in a population of bacteria, some may be more resistant to antibiotics and take longer to kill
- upon taking antibiotics, most bacteria will die, however those with the resistant genes will continue to survive, living for longer and then reproducing, creating a population of antibiotic resistant bacteria which becomes more common over time.
- this is known as an antibiotic resistant strain
- this is an example of longer evolution
What are antibiotics?
- antibiotics are drugs designed to kill bacteria or stop it from reproducing
What was the first ever antibiotic?
- penicillin
Why is it so important to take antibiotics for their full course?
- often, people stop taking antibiotics once they feel better, however this leaves the resistant bacteria that takes longer to kill alive, and able to reproduce new resistant bacteria that cannot be treated with the same antibiotic
- this is dangerous because if someone were to still carry this infection caused by antibiotic resistant bacteria, they could spread this into others, who also would now have antibiotic resistant bacteria that could not be treated with antibiotics
Why is anti biotic resistance becoming more common?
- Doctors often prescribe antibiotics in cases where they aren’t necessary. For example, mild or viral infections
- Many people don’t take the full course of antibiotics, so not all the bacteria are killed
- Huge amounts of antibiotics are given to farm animals in order to make them grow faster
What are fossils?
- the preserved remains of organisms that died millions of years ago
- can be found as skeletons in rock, hardbody parts like bones and shells which do not decay easily or are replaces by minerals as they decay
- imprints/impressions in the ground
- entire organisms that have not yet decayed
How do fossils provide evidence of how organisms have changed overtime?
- fossils found in rocks can show this change because the deeper the rock, the older it is
- by arranging fossils in chronological order, gradual changes in organisms can be observed, this shows evidence for evolution because it shows how species have changed and developed
- rocks that are deeper in soil are often older whereas those that are in a higher level are more recent
What are some drawbacks to using fossils as evidence for human evolution?
- fossils don’t always show smooth changes in organisms over time because some fossils have still not been discovered.
- some soft bodied life forms may have also decayed faster creating a gap that remains undiscovered
What are hominids?
- this is the name given to human beings and their ancestors
- hominid species that have been found often have a mix of characteristics between human and ape like
Describe ardi.
- alive 4.4 million years ago
- ardipithecus ramidus
- feet structure suggests she climbs trees as she had big ape like toes
- long arms and short legs (more ape like)
- her brain was the size of a chimpanzee but her leg structure suggest she was able to walk upright
- structure of her hand bones shows that she did not use them to assist with walking
Describe Lucy.
- 3.2 million years ago
- Australopithecus afarensis
- more human like than ardi
- had arched feet more adapted to walking then climbing, no ape like toes, more human like, the structure of her leg bones also suggests she walked upright
- brain was slightly larger than ardi