Evolution 5.2 Natural Selection Flashcards
Why do living organisms face a struggle for survival?
- All species have great potential fertility 2. Population sizes show long term stability 3. Environmental resources are limited Living organisms have to compete with other members of their species in order to survive
Why do living organisms face a struggle for survival?
- All species have great potential fertility 2. Population sizes show long term stability 3. Environmental resources are limited Living organisms have to compete with other members of their species in order to survive
What do members of a species show?
Living organisms show an enormous range of variation. No two living organisms are ever truly identical, even if they are genetic clones
Only under what condition can natural selection occur?
Natural selection can only occur if there is variation among members of the same species. Adaptations are characteristics that make an individual more suited to survive in its environment and successfully reproduce.
What promotes genetic variation?
Independent assortment, Meiosis, Gene Mutation and sexual reproduction
How does natural selection lead to evolution?
- Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring 2. individuals that reproduce pass on characteristics to their offspring 3. natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species
Explain how the use of antibiotics has led to the evolution of resistant bacteria
- members of a population of the same species show variation - some organisms are more likely to survive due to selective advantage - these variations may be genetically controlled/heritable - these genes are most liekly to be passed on to offspring - this can change the characteristic of the population - bacteria can noramlly be killed by antibiotics - anti biotics impose a selection pressure - if few bacteria have natural resistance to the antibioticthey will survive - if the resistance is heritable they will pass it on their offspring - they will reproduce/evolve to form bacterial colonies resistant to antibiotics.
Explain how the use of antibiotics has led to the evolution of resistant bacteria
- members of a population of the same species show variation - some organisms are more likely to survive due to selective advantage - these variations may be genetically controlled/heritable - these genes are most liekly to be passed on to offspring - this can change the characteristic of the population - bacteria can noramlly be killed by antibiotics - anti biotics impose a selection pressure - if few bacteria have natural resistance to the antibioticthey will survive - if the resistance is heritable they will pass it on their offspring - they will reproduce/evolve to form bacterial colonies resistant to antibiotics.
Briefly explain Darwin`s theory of evolution.
• Species tend to produce more offspring than the environment can support • the consequence of the potential overproduction of offspring is a struggle for survival • Mutation, meiosis and sexual reproduction cause variation (different characteristics) between individuals in a species. • Adaptations are characteristics that make an individual suited to its environment. • Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring. • Individuals that reproduce will pass on characteristics to their offspring. • This selective “pass on characteristics” is called natural selection. • Natural selection leads to change in allele frequency. • Characteristics acquired during the lifetime of an individual (Eg. Learned skills) are not heritable. Therefore, it does not affect evolution.
What is an acquired characteristic?
An Acquired characteristic is a change that happens to an organism during its lifetime. These types of characteristics do not affect DNA and are not heritable.
Discuss evidence against the theory of evolution by inheritance of acquired characteristics.
? This is an incorrect theory stating that characteristics acquired during the lifetime of an individual can be passed on to next generation. ? Acquired characteristics example: giraffes reach for leaves on tall tree, therefore their neck becomes longer, over many generations, giraffes have long neck. ? This theory is incorrect because it relies on phenotypic inheritance, not genotypic inheritance /somatic changes cannot be passed on ? example: if tail cut off rat – offspring still have tails ? cannot be repeated experimentally since very many generations would be necessary ? also mutations would have to be eliminated in such an experiment – impossible
Explain with an example of natural selection causes progressive change.
Darwin collected finches which varied in sizes and shapes of their beaks.
Beaks characters and diet are closely related, when one changes the other does also. Medium ground finch can eat large and small seeds whereas small finch can only eat small seeds.
Daphne Major absence of small ground finch so… When eating small seeds the medium ground finch was smaller in body and beak size. When there was a shortage, the larger beaked individuals survived.
Variation in beak and body size is mostly due to genes but the environment has some effect. The proprtion of the variation due to genes is called heritability.
What is progressive change?
Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics.
What is adaption?
Adaption are characteristics that make an individual suited to its environment.
