Conditions for natural selection
- Variation in characteristics of an individual
- Heredity of characteristics
- Reproduction of more offspring than the environment can support (allows competition)
- Variation in fitness (ability of an organism to survive and reproduce
What causes variation in species which sexually reproduce?
- random mutation (during dna replication or viral infection)
- sexual reproduction (random fertilization and meiosis)
Meiosis: - crossing over during prophase
- random assortment of chromosomes during metaphase
What causes variation in asexual reproduction?
- mutations
- this means that there is not enough mutations for populations to evolve quickly enough for survival when environmental change occurs
What are adaptations?
- Characteristics that make an individual better suited to its environment
- they take time to develop and are a result of natural selection: DO NOT develop during an individual’s lifetime
What are acquired characteristics?
- characteristics that DO develop during an individual’s lifetime
- cannot be inherited and do not contribute to evolution
Examples: scars, dyed hair, tanned skin
When there is an increase in offspring:
There will be an increase in competition as not every individual will obtain enough to allow them to survive and reproduce
Adaptation process
- those with traits that give the individual an advantage will survive and reproduce
- those with traits that give the individual a disadvantage will not survive and reproduce
- this results in an increase in the proportion of individuals in a population with characteristics that make them well adapted
- the characteristics of the population will gradually change: evolution by natural selection
Finches on Daphne Major (adaptive evolution) (Darwin)
- obs.
- hyp.
- findings
Observations: Darwin observed that the beaks of the finches and their diet varied
Hypothesis: the finches originated from one species that has evolved into many different species
Findings: each new island had different selective pressures and finches had adapted to better suit their own islands over millions of years (evolved into diff. Species)
Relationships between beak characteristics and diet (Peter and Rosemary Grant)
- findings
- the Grants documented that the beak lengths are a result of changing weather conditions
- weather conditions affect the type of seeds that grow (small during wet years, longer seeds during dry years)
- finches beaks increase during drought
Evolution of antibiotic resistance in bacteria
- use of antibiotics kill bacteria which are non-resistant
- those who are resistant reproduce and pass on genes
- antibiotic resistant bacteria population increases
- bacteria has evolved to be resistant to antibiotics
What are some reasons why antibiotic resistance in bacteria can evolve quickly?
- widespread use of antibiotics
- bacteria reproduce rapidly
- large pop. of bacteria, therefore there is a high chance of bacteria with antibiotic resistant gene occurring
- bacteria can pass genes onto other bacteria
