natural selection Flashcards
What is Darwin’s theory of evolution by natural selection?
Due to differences in genes, individuals within a population of a species show variation in characteristics
Those with characteristics suited to the environment have a higher chance of survival and therefore are more likely to reproduce more and have more offspring
Therefore, the characteristics which favour survival are passed onto more offspring than the characteristics which do not
Over many generations, these beneficial characteristics become more common in the phenotypes of the population of that species
The gradual change in phenotypes in a population of species is evolution.
What are antibiotics?
Antibiotics are chemical substances used medicinally to treat bacterial infections
They work by disrupting bacterial cell structure or functions, or by preventing them from reproducing.
How do antibiotics work?
They work by disrupting bacterial cell structure or functions, or by preventing them from reproducing
They are only effective against bacterial infections - not virus or fungi.
Give an example of an antibiotic and its mechanism.
Penicillin interferes with bacteria building their cell walls
As they are bacteria-cell specific, antibiotics generally do not affect animal or plant cells.
Do antibiotics affect viruses?
No, antibiotics do not affect viruses as they are not living and do not have cell processes
Viruses instead live inside a host cell.
How does antibiotic resistance develop?
Bacteria can undergo mutations, some of these mutations may give them resistance to antibiotics
The overuse of antibiotics can lead to bacteria with mutations giving them resistance surviving and reproducing more than other bacteria.
What are the effects of antibiotic resistance?
The bacterial population of those with resistance to antibiotics will increase
These bacteria will become even more prevalent as their infections cannot be treated with antibiotics
This makes infections difficult to control as many types of antibiotics will not work on certain bacterial infections.
mutation
Mutations are rare, random changes that occur in the sequence of DNA bases in a gene or a chromosome
Mutations can be inherited
As the DNA base sequence determines the sequence of amino acids that make up a protein, mutations in a gene can sometimes lead to a change in the protein that the gene codes for
Most mutations do not alter the protein or only alter it slightly so that its appearance or function is not changed
evolution
animal and plant species are not fixed in their form, but change overtime.
Darwin’s evolution MS (4)
Species change over time (not fixed) (1 mark)
Variation exists (due to mutations/random genetic differences) (1 mark)
Struggle for survival (competition for resources) (1 mark)
Survival of the fittest (advantageous traits lead to more reproduction) (1 mark)
Inheritance of traits (successful traits passed to offspring) (1 mark)
why is Darwin’s theory criticized
Lack of evidence (e.g., no knowledge of genetics/Mendel’s work yet) (1 mark)
Religious opposition (conflict with creationism) (1 mark)
Incomplete explanation (e.g., couldn’t explain inheritance or sudden extinctions) (1 mark)
Social resistance (challenged human uniqueness) (1 mark)
fossil formation
“When an organism dies, it is buried by sediment before decomposing. Soft tissues decay, but hard parts (bones, shells) remain. Over time, minerals replace these hard parts, forming a rock-like fossil.” (3/3 marks)
fossils as evidence
Show extinct species (proof of life forms that no longer exist) (1 mark)
Reveal gradual changes (e.g., limb development in transitional fossils) (1 mark)
Establish timelines (older fossils in deeper rock layers) (1 mark)
