5.7 Adapt or die Flashcards
Struggle for existence
Competition for survival
and reproduction between members of a species;
a component of natural selection.
Survival of the fittest
Only those individuals (the
fittest) best adapted to their physical and
biological environment are likely to survive and
reproduce.
Mutation, Mutant, Mutate
A change in the
genetic material in a cell. Some mutations are
concerned with very small changes to an
organism’s DNA. These are known as gene
mutations. Mutations happen by chance, but
certain environmental factors called mutagens
can increase the rate of mutation. Mutations play
an important part in breeding plants with
desirable characteristics. Mutations to the genes
that control cell division are a cause of cancer.
Allele, Allele frequency
One of the different
forms of a particular gene. In humans, a gene
codes for the protein that transports chloride ions
across the cell surface membrane. We all have
this gene, the CF gene. The CF gene has two
alternative forms or alleles. The normal allele, F,
produces a functioning protein. The other allele,
f, produces a protein which is very slightly
different and does not function. If a person has
two copies of the f allele, he or she will have
cystic fibrosis. The relative frequency of alleles
in a population of organisms changes over time
with evolution. Alleles that are for advantageous
characteristics will become more frequent, with
those that do not provide an advantage becoming
less frequent.
Valid
A measurement is valid if it measures what
it is meant to be measuring. An experimental
procedure is valid if it produces results that will
answer the question being asked/test the
hypothesis being investigated. A conclusion is
valid if it is supported with valid data and sound
scientific reasoning.
Molecular clock
The molecular clock hypothesis
assumes that DNA mutations occur at a steady
rate over time and among different organisms.
This constancy means that genetic differences
between two species will be proportional to the
time since they shared a common ancestor. This
allows the time since species last shared a
common ancestor to be measured. The
molecular clock is calibrated using the known
timing of particular evolutionary events
estimated from, for example, the fossil record.
Genetic fingerprint, DNA fingerprint, DNA
fingerprinting, DNA profiling
A technique
that distinguishes individuals on the basis of
slight differences in their DNA. Not all the DNA
present in the nucleus of a cell codes for
proteins. Some of the non-coding DNA consists
of short sequences of nucleotide bases which
may be repeated. The actual number of times
these sequences are repeated varies from
individual to individual. Genetic fingerprinting
compares these sequences.
Speciation
The formation of a new species. It is
generally accepted that for a new species to
arise, a group of individuals has to be isolated
from the rest of the population. There will be
different selection pressures acting on the two
groups, which will become less and less like
each other. Eventually there will come a time
when they are reproductively isolated and can
be considered as distinct species.
Reproductive isolation
Two populations are
described as being reproductively isolated when
they are unable to breed with each other, or they
produce offspring which fail to survive
Allopatric speciation
The formation of a new
species due to reduced gene flow between two
populations as a result of geographical isolation.
The two groups are unable to mate so are
reproductively isolated. Random mutations in
each population and different selection pressures
lead to changes in allele frequencies. If members
of the two groups change in ways that prevent
individuals from the two populations from
interbreeding and producing fertile offspring
then they are considered to belong to different
species.
Sympatric speciation
This occurs where two populations become reproductively isolated in the same environment without any geographical barrier, due to other isolating mechanisms
Genetic drift
The chance increase or decrease in
allele frequency over time. These differences
result from random mutation adding new alleles
to the population. They can also result from
organisms carrying particular alleles failing to
breed.
