Variation and selection Flashcards
Describe variation
the differences between
individuals of the same species
What continuous variation results in?
in a range of phenotypes between two extremes
state examples of continuous variation;
body length and body mass
What discontinuous variation results
in
results in a limited number of phenotypes with no
intermediates
state examples of discontinuous variation
examples include;
ABO blood groups
seed shape in peas
seed colour in peas
what is discontinous variation caused by?
usually caused by genes only
what is continuous variation caused by?
caused by both genes and the environment
Define a mutation
a genetic change
Describe gene mutation
a random change in the base sequence of DNA
How are new alleles formed?
by mutations
states the sources of genetic variations in populations
mutation
meiosis
random mating
random fertilisation
What increase the rate of mutation
ionising radiation and some chemicals
Define an adaptive feature
an inherited feature that helps an organism to survive and
reproduce in its environment
state examples of natural selection
- genetic variation within populations
- production of many offspring
- struggle for survival, including competition
for resources - a greater chance of reproduction by
individuals that are better adapted to the
environment than others - these individuals pass on their alleles to the
next generation
Define an adaptation
the process, resulting from natural selection, by which populations become more suited to their environment over
many generations
State an example of natural
selection
the development of strains of antibiotic
resistant bacteria
Outline the differences between natural and
artificial selection
Explain the development of strains of antibiotic resistant bacteria
This process is an example of natural selection because it involves the survival and reproduction of individuals with traits that confer a survival advantage.
In this case, the antibiotic resistance gene is the advantageous trait that allows bacteria to survive and reproduce in the presence of antibiotics. As a result, antibiotic-resistant strains of bacteria become more common in populations over time, demonstrating the process of natural selection in action.
Outline how selective breeding by artificial
selection is carried out over many generations to
improve crop plants and domesticated animals
(a) selection by humans of individuals with
desirable features
(b) crossing these individuals to produce the
next generation
(c) selection of offspring showing the desirable
features
