Topic 4 - Natural Selection and Genetic Modification Flashcards
What is Charles Darwin’s theory of evolution by natural selection?
-Genetic variation exists within a population (This might be because of sexual reproduction or mutations)
-A selection pressure is introduced
-Some organism with advantageous traits are more likely to survive and reproduce
-These organisms are more likely to pass on their genes to the next generation - including the advantageous characteristic
-This repeats over many generations and the frequency of the characteristic increases
Explain how the emergence of resistant organisms supports Charles Darwin’s theory of evolution including antibiotic resistance in bacteria
Bacteria are resistant when they are not able to be killed by antibiotics which were previously used as cures against them.
-Bacteria reproduce at a rapid rate
-Mutations can cause variation in a population of bacteria, with some being more resistant to antibiotics
-Antibiotics are a selection pressure as the less resistant bacteria die
-Those with antibiotic resistance may survive, can reproduce and pass on the advantageous gene
-The population of antibiotic resistant bacteria increases
-Therefore, the presence of resistant bacteria supports Darwin’s theory of natural selection as the new bacteria have been selected by the environment to have a feature advantageous to survival
Describe the evidence for human evolution based on the first humanoid species
The oldest known human ancestor is Ardi (Ardipithecus ramidus) who lived 4.4 million years ago and had both ape and humanoid features; this intermediacy suggests gradual evolution between the two. Hip structure and hand structure suggests stood upright not on all-4s, 350cm3 skull volume. Had different foot structure from chimpanzee but still opposable big toe for climbing.
Describe the evidence for human evolution based on the second humanoid species
The fossilised Skelton Lucy (from the species Australopithecus afarensis) dates from 3.2 million years ago. Had 400cm3 skull volume (small like chimp) but non-opposable toe arranged same as modern but more curved. Intermediacy suggests evolution and more than Ardi as greater skull volume.
Describe the evidence for human evolution based on the latest non-homo-sapien humanoid species
Homo Erectus fossils discovered by Richard Leakey, species alive between 1.8-0.5 million years ago. Strongly built 850cm3 skull volume (greater than previous species but less than 1450cm3 skull volume of Homo sapiens)
How did stone tools develop? How is this evidence for human evolution?
Stone tools became more complex, indicating our brains evolved in complexity.
-Homo Habilis used basic pebble tools 1.5 million years ago made by smashing rocks together.
-In the late Stone Age homo sapiens and neanderthals used pointed arrowheads, spears and hooks.
How can stone tools be dated?
-By radiometric carbon dating. If a nice-living material is found with a tool we can date the natural radioactive decay of an isotope of carbon on it to estimate how long ago the organism the material was from lived.
-By stratifying rock layers. We can date once-living fossils from the same rock layer as the tool (as each layer of sediment must have been formed at the same time) to estimate when the tool was formed.
What kind of structure is the pentadactyl limb?
A homologous structure as, while the structures of different organisms may appear superficially different, they have the same underlying structure.
The pentadactyl limb is shared between many different species.
Explain how the study of the pentadactyl limb provides evidence for evolution.
As a wide variety of vertebrates share the pentadactyl limb as they all evolved from a common ancestor which had it. However, divergent evolution then took place in which each of these species evolved to fill a specific niche. (Different mutations –> different environments –> different features which are beneficial there and therefore survive + reproduce)
Describe how genetic analysis has led to the suggestion of the three domains rather than the five kingdoms classification method
Before domains were made kingdoms were the largest group. Bacteria and archaea were in the prokaryote kingdom.
Then, after we developed methods to make molecular observations (analyse genes)) we realised that bacteria and archaea aren’t as similar as we thought: so the 3 domains were made of bacteria, archaea and eukarya (everything with a nuclei)
List the order of classification from most closely related to least diversity between individuals
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
Define selective breeding
When humans choose certain organisms to breed together because they have useful characteristics
Explain how you might go about selective breeding.
-Genetic variation exists.
-Select 2 of the same species that have the desirable characteristic and have them breed together.
-Then breed together the offspring with the greatest of this characteristic.
-Eventually the majority of the population should have this characteristic.
Explain the problem that can arise from selective breeding.
This can result in inbreeding as breeding those with similar desirable characteristics mean it is likely that they are closely related. This results in reduction of the gene pool as the number of different alleles reduce. This means if there is a selection pressure the chance of a few organisms have a survival advantage and not dying is reduced so the species may become extinct.
The small gene pool can also lead to a greater chance of genetic defects as recessive characteristics are more likely to present.
How is tissue culture performed?
- Using tweezers remove a piece of tissue from a fast-growing region of the plant you would like to clone
-Using aseptic technique, place the tissue on a growth medium containing necessary hormones and nutrients
-Once the tissue has developed enough (e.g. produced shoots and roots) it can be transferred to compost for further growth.
