5.2 NATURAL SELECTION Flashcards
OCCURRENCE OF NATURAL SELECTION
within a species, different individuals of that species show genetic variation
individuals that are best suited for their environment will survive and reproduce
IF THERE WAS NO VARIATION WITHIN A SPECIES
then all individuals would be the same and no individual would be favoured over the other and natural selection would not take place
SEXUAL REPRODUCTION CAN PRODUCE
variation in a species through fertilization and meiosis
SEXUAL REPRODUCTION OCCURS WHEN
2 different members of a species create offsprings that have a combination of genetic material contributed from both parents
ESSENTIAL IDEA
the diversity of life has evolved and continues to evolve by natural selection
VARIATION BETWEEN MEMBERS SPECIES IS DUE TO (3)
random mutation
- -> DNA replication
- -> viral infection
sexual reproduction
- ->meiosis
- —-> crossing over P1
- —-> random assortment of chromosome M1
random fertilization
NATURAL SELECTION AND MUTATIONS
Mutations that give an advantage are selected for.
Mutations that give a disadvantage are selected against
FINCHES
Beak shape changes according to the food
environmental change causes change in available food
STRUGGLE FOR SURVIVAL
If there are too many organisms, the demand for resources increases.
However, there is a limited supply of resources in an ecosystem.
Overpopulation and a limited amount of resources creates competition within a population.
They have to compete for mates, food, space, predation, and disease.
OFFSPRING PRODUCTION AND STRUGGLE FOR SURVIVAL
Populations tend to produce more offspring than the environment can support or that could survive in a particular community or ecosystem.
When parents don’t spend a lot or even any time caring for their young, they produce many offspring. This is a reproductive method used to make sure
some offspring make it to the next generation.
Parents that put a lot of time and energy protecting and raising their young tend to have far smaller litters, i.e. most mammals.
WITHIN A POPULATION
Within a population, there is genetic variation between the individuals in the population.
ORGANISMS WITH BENEFICIAL CHARACTERISTICS
The organisms with the beneficial characteristics will be able to out-compete the other individuals with the less beneficial or harmful genetic traits for
limited resources and mates.
CONSEQUENCE OF ORGANISMS WITH BENEFICIAL CHRACTERISTICS
Therefore, these individuals will survive and reproduce and pass these genetic traits onto the next generation of offspring.
ORGANISMS WITH LESS DESIRABLE TRAITS
Organisms with less desirable traits will die or produce less offspring
ACCUMULATION OF BENEFICIAL TRAITS
Over many generations the accumulation of these beneficial genetic traits may result in a change in the population known as evolution.
FOR ANOTHER SPECIES TO DEVELOP
For another species to develop, these genetically different individuals eventually have to become reproductively isolated (separated from the general
population) where they will only reproduce with individuals with similar genetic traits.
ACQUIRED CHARACTERISTICS
Acquired characteristics of an individual such as large muscles are not passed on to an organism’s offspring
OVER PRODUCTION OF OFFSPRING EXAMPLES
Fish produce thousands of eggs but only few make it to adulthood.
Plants also can produce hundreds or thousands of seeds to be released into the environment.
ANTIBIOTICS
Antibiotics kill bacteria directly or weaken the bacteria so your immune system can fight and destroy the invading pathogen.
BACTERIAL INFECTION
If a patient has a bacterial infection, when antibiotics are given to fight the infection the majority of the original population of bacteria will be destroyed.
ANTIBIOTIC RESISTANCE
However, some of these bacteria might not die because of changes within their DNA. These changes could be caused by mutations within their genome
or the transfer of an antibiotic resistant gene from another bacterium.
LIKELINESS OF ANTIBIOTIC RESISTANCE
Resistance is more likely to occur if the proper amounts of antibiotics aren’t taken or if a patient doesn’t finish the prescription.
CONSEQUENCE OF ANTIBIOTIC RESISTANCE
These resistant bacteria will survive and reproduce, creating more identical resistant bacteria.
These resistant bacteria will make the person sick again in the future.
However if given the same antibiotic, these bacteria will no longer be destroyed.
Resistance can be passed onto other pathogenic bacteria, creating more species of resistant bacteria.
ANTIBIOTIC RESISTANCE SOLUTION
Another antibiotic can be prescribed to kill these new resistant bacteria.
