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Natural Selection and GM I - Coggle Diagram
Natural Selection and GM I
Evolution
The slow continuous change of an organism's characteristic over many generations
The theory of evolution and observations Darwin made
Individuals in a populations show genetic variation caused by different alleles. New alleles arise through mutations
Things like predators, competition for resources and disease act as selection pressures, which affects an organism's change of surviving
Individuals with characteristics that make them better adapted to selections pressures have a better chance of survival, so are more likely to breed successfully
Alleles responsible for useful characteristics are more likely to be passed on to the next generation
Individuals less well adapted may be less able to compete, so are less likely to survive and reproduce, survival of the fittest
Beneficial characteristics become more common in the population over time
Importance
Helps understand the relationships between different species of organisms
Explains how new species evolve
Explains how different species adapt to changes in their environment
Natural selection
Individuals of a species show variation
Some individuals will be better able to survive in their environment than others
Natural selection - when the environment selects which individuals pass on their alleles to the next generation
Evidence for evolution
Antibiotics
Bacteria sometimes develop random mutations in their DNA, which can allow them to be less affected by a particular antibiotic
The ability to resist an antibiotic is a big advantage as the can better survive. So it can live longer and reproduce more times
Bacteria reproduce using binary fission, which produces clones the bacteria, and its DNA
Bacteria can also transmit useful alleles by conjugation, so the resistance can pass to different species
Antibiotic resistance makes the bacteria better adapted to a new environment in which a selection pressure 'antibiotics' is present. So resistance may become more common over time resulting in bacterial disease spreading rapidly
Human evolution
Human beings and their ancestors are known as hominids. Fossils of different hominid species have been found which share characteristcs with apes and humans
Ardi
From species ardipithecus ramidus
4.4 million years old
Foot sturcture suggests she climed trees
Her brain size was much small than humans today - 350 cm3
Believed to walk upright
lucy
From the species Australopithecus afarensis
3.2 million years old
feet adapted to walking rather than climbing
slightly larger brain than Ardi - 400cm3
walked upright, but more efficiently than Ardi
Homo habillis
2.4-1.4 million years ago
500-600 cm3 brain size
Used simple stone tools
Homo sapiens
Around since 200,000 years ago
Brain size of 1200 cm3
Uses more complex tools
Stone tools
The different Homo species continues to evolve and tools gradually became more complex, so brains must have been getting larger
Homo habilis, 2.5 -1.5 mya. made simple stone tools by hitting rocks together
Homo erectus, 2-0.3 mya, sculpted rocks into more complex shapes like hand axes
Homo neanderthalensis, 0.3-0.025 mya, made flint tools with sharp pointed edges, as well as spears
Homo sapiens, first appeared more than 200,000 years ago used even more complex tools. The later used arrowheads and fish hooks
Dating stone tools and fossils
Stratigraphy, the study of rock layers. For a tools or fossil to be found in a rock layer, it , must have been present at the time the layer was formed
Radiometric dating, using potassium- argon dating
Pentadactyl limb
A limb with 5 digits
Can be seen in all organisms with four limbs including mammals, birds, reptiles and amphibians
In each of these groups of animals, the bone structure is similar
Evidence for evolution
Provides evidence that all species with the limb have evolved from one common ancestor
If they all evolved from different ancestors, it's be highly unlikely that they'd share a similar bone structure
Limbs have developed in different ways because they've adapted to different uses
Classification
5 kingdoms: Animals, plants, fungi, prokaryotes, protists
livings things are divided into these 5 kings
3 domain classification
Using RNA sequencing Carl Woese found out that some members of the Prokaryote kingdom weren't as closely related as first thought
He proposed that the kingdom should be split into two groups called Archaea and Bacteria
Woese said that all organisms should firstly be divided into 3 large groups called domains, Archaea, Bacteria and Eukarya
Selective breeding
When humans artificially select the plants or animals that are going to breed so that genes for particular characteristics remain in the population
Process
1) From the existing stock, select the ones which have the characteristic you want
2) Breed them with eachother
3) Select the best offspring and breed them together
4) Continue this process over several generations, and the desirable trait will get stronger, and eventually all the offspring will have it
Reducing the gene pool
Reduces the number of genes in a populationtion
Can cause health problems because there is more chance or organisms inheriting harmful genetic defects
If a new disease appears, because there isn't much variation, then there is less chance of the resistance alleles being present
Reaosns
Disease resistance
Increasing yield
Better ability to cope with difficult conditions
Benefits
You can greatly increase the yield
Plants and animals can be red to be resistance to a particular disease
GM crops
Benefits
Amount of food produced can be increased
Crops can be engineered to contain additional nutrients, which could help combat certain deficiency diseases. Common in developing countries
Concerns
Countries may become dependant on companies that sell GM seeds
Poor soil in one of the reason why crops fail, so even GM crops won't survive
Long term effects on human are unknown
Bt crops
Bacillus thuringiensis
A type of bacteria which produces a toxin that kills many insect larvae that are harmful to crops
Gene can be inserted into crops, so that they can be resistant as the toxin will be produced in their stem and leaves
Harmless to humans
Gene for Bt toxin can be cut out of the bacterial DNA and inserted into the DNA of a plant cell
Pros
Crop damage reduced
Less insecticide needed, doesn't harm useful insects
Cons
More expensive
Insect pests may become resistance to Bt toxin