18. Variation And Selection Flashcards
what is variation
the difference between organisms of the same species
what causes variation
mutations in the genetic code
what is phenotypic variation
the variation in physical traits and characteristics of organisms of the same species
what is phenotypic variation caused by
both genes and the environment
what is genetic variation
the difference between the genetic makeup of different organisms of the same species
what is discontinuous variation
variation that produces distinct categories
what is continuous variation
variation that cannot be placed into distinct categories and instead produces a spectrum
what is mutation
a random change in the base sequence of the DNA of an organism
state 2 things which may increase the rate of mutation
ionizing radiation
certain chemicals
state 3 symptoms of sickle cell anaemia
headaches
fatigue
fainting
how does sickle cell anaemia arise
- the base sequence in the DNA that codes for the hemoglobin protein changes
- this produces abnormal hemoglobin which leads to sickle shaped red blood cells
what disease do people who are heterozygous for sickle cell anaemia have resistance to
malaria
use a genetic diagram to sho the 4 offspring produced when two heterozygous sickle cell anaemia carriers reproduce
describe the distribution of sickle cell anaemia with reference to the distribution of malaria
sickle cell anaemia tends to be found more in places where malaria is common
explain the distribution of sickle cell anaemia with reference to the distribution of malaria
people who have sickle cell anaemia are resistant to malaria
those without sickle cell anaemia are not immune and are more likely to die from malaria
over time a majority of the population will carry the sickle cell anaemia gene
what is an adaptive feature
any inherited feature which helps an organism to survive in its environment and pass on its genes
what is an adaptive feature
the inherited functional features of an organism that increases the fitness of the organism
define fitness
the ability of an organism to survive and pass on its genes in its environment
what are hydrophytes
plants which are adapted to live in aquatic condition
state 3 advantages of hydrophytes
wide and flat leaves
large air spaces
thin waxy cuticle
what are xerophytes
plants which are adapted to live in very arid and dry conditions
state 3 adaptations of xerophytes
rolled leaves
thick way cuticle
small needle shaped leaves
describe the process of natural selection
- population are naturally varied due to random genetic mutations
- some of these mutations provide a selective advantage
- these organisms survive and reproduce, passing on the successful genes
define evolution
a change in the features of organisms over time due to natural selection
what is the process of adaptation
populations become suited to their environment over time due to natural selection
what is the development of antibiotic resistance an example of
evolution by nature selection
describe how antibiotic resistance arises
- a random genetic mutation causes a bacterium to become resistant to the antibiotic
- when the antibiotic is used, al the bacteria that do not have the mutation are killed
- the population containing just the resistance bacteria then begins to grow
describe how selective breeding is carried out
- organisms with the desired traits are selected
- these organisms are bred together
- this process is repeated until the offspring have the desired characteristics
what is the difference between natural selection and artificial selection
natural selection occurs when the selection pressures are created by the environment whereas artificial selection is when humans deliberately create selection pressures
