Variation Flashcards
We differ or vary from one another in the characteristics that we have. What are the two types of variation that exist?
Continuous and discontinuous
What do we mean by a characteristic showing CONTINUOUS VARIATION
A characteristic displays continuous variation if there is a gradual change in it across a population eg height and length
What do we mean by a characteristic showing DISCONTINOUS VARIATION?
A characteristic displays discontinuous variation if the population can be divided into discrete groups or categories eg. ability to roll your tongue and hand dominance
How do we display data for a characteristic which is continuous?
As a HISTOGRAM
Typically data for a continuous characteristic will show “normal distribution”. What does that mean?
In normal distribution, most individuals lie around the average or mean, with fewer at the extremes
How do we display data for a characteristic, which is discontinuous?
As a BAR CHART (has spaces between the bars!)
What two factors affect variation?
Genetic make-up and the environment
In what ways do genes cause genetic variation?
Though meiosis producing genetically different eggs and sperm
Random fertilization of any egg by any sperm
Mutations which cause random changes in genes
How, specifically, does environment contribute to variation?
The environment affects phenotype eg a plant grown in soil low in magnesium would have pale yellow leaves instead of green
What is “natural selection?”
Natural selection is the process by which individuals compete for resources and the better adapted individuals survive (i.e. survival of the fittest), passing on their genes to their offspring.
Explain natural selection in terms of how antibiotic resistance in bacteria developed
A small number of bacteria have a gene (through mutation) for antibiotic resistance
When treated with the antibiotic the resistant bacteria survive, those that do not, die
The survivors reproduce and pass on their resistance gene to their offspring which leads to a population of resistant bacteria
What is evolution?
Evolution is the change in species over time, as a consequence of natural selection favouring different phenotypes
What are fossils?
Fossils are the remains of plants and animals, preserved over millions of years
What leads to extinction?
Species become extinct when they fail to adapt to environmental change
What does endangered mean?
Endangered means that a species is at risk of extinction
