1
Q
Darwinism
A
- Darwinism is the theory proposed by Charles Darwin regarding the evolution of a species
by natural selection. Darwin is known as the father of evolution. - Charles Darwin was an English naturalist. He explained his ideas about evolution in a book
called On the Origin of Species, which was published in 1859. - Darwin’s ideas caused a lot of controversy. This continues to this day, because his ideas may
be seen as conflicting with religious views about the creation of the world and creatures in
it. - Darwin’s theory of natural selection states that nature selects organisms that have features
favorable for their survival, while eliminating inferior species. - Darwin’s theory includes three principles namely variation, heredity and struggles for
exist.
2
Q
Observations of his theory
A
- More individuals are produced each generation than can survive
- Physical variation exists among individuals and the variation is
heritable. - Those individuals with heritable traits better suited to the
environment will survive.
3
Q
Adaptive radiation
A
- The process in which one species gives rise to multiple species that exploit
different niches is called Adaptive Radiation. - The ecological niches exert the selection pressures that push the populations in
various directions.
4
Q
Darwin’s Finches
A
- Darwin did not initially realize the significance of the finches he collected.
- Darwin thought that the finches found across the different islands were all
different species. - It was not until Darwin’s Finches were properly identified and studied by the
famous ornithologist, John Gould, that Darwin began to realize that a more
complex process was going on. - Gould realized that they the finches all belonged to a related group of birds,
comprising 12 sub-species.
5
Q
Adaptation
A
The Process by which a species becomes fitted to its environment; it is
the result of natural selection acting upon heritable variation over several
generations.
6
Q
Reproductive fitness
A
The Process by which a species becomes fitted to its environment; it is
the result of natural selection acting upon heritable variation over several
generations.
7
Q
Deleterious gene
A
An allele of a gene whose effects on the phenotype are likely to
result in a reduced fitness.
8
Q
Inconsistencies
A
- The fossil record often lacks transitional forms and that there are “explosions”
of new life forms. - Many scientists have challenged the ability of random mutation and natural
selection to produce complex biological features. - It is highly unlikely that complex structures like the ear and eye would have
been formed by chance mutations. - Many lines of evidence for Darwinian evolution and common descent are
weak:
o Vertebrate embryos start out developing very differently, in contrast with
the drawings of embryos often found in textbooks which mostly appear
similar.
oDNA evidence paints conflicting pictures of the “tree of
life”. There is no such single “tree.”
oEvidence of small-scale changes, such as the modest
changes in the size of finch-beaks or slight changes in the
color frequencies in the wings of “peppered moths”,
shows microevolution, NOT macroevolution.
9
Q
Darwinism vs Neo Darwinism Similarities
A
- Both Darwinism and Neo Darwinism talk about the evolution of a
species. - Both account natural selection as a factor.
- Darwinism and Neo Darwinism theories include Charles Darwin’s
findings.
10
Q
Darwinims vs Neo Darwinism Difference
A
Darwinism does not include Mendelian genetics while Neo Darwinism
incorporates recent discoveries of inheritance and genes
11
Q
Comparative summary of DW vs NDW
A
- Darwinism and Neo Darwinism are two evolutionary theories. Darwinism is the original
theory proposed by Charles Darwin while Neo Darwinism is the modification of the
original theory of Darwin. Neo Darwinism has eliminated the shortcomings and
drawbacks of Darwinism. It accounts for different factors such as variation, mutation,
isolation, heredity and natural selection, etc. This is the difference between Darwinism
and Neo Darwinism.
12
Q
Basics of Neo Darwinian
A
- Gene Mutations*
- Changes in chromosomes structure and number*
- Genetic recombination*
- Natural selection
- Reproductive isolation
13
Q
Gene Mutation
A
- The heritable characters of an individual depend on the genes that control them.
- A gene is a small section of DNA that contains the instructions for a specific molecule,
usually a protein. Each gene contains the information required to build specific
proteins needed in an organism. - A mutation is a spontaneous change in the DNA.
- Changes in the genes alter the phenotypic characters of the individuals.
- A mutation may also give an organism an adaptive advantage or may put it at a
disadvantage (a deleterious mutation) - Scientists assert that mutations are the ultimate source of variation in a population,
thus, they are responsible for adaptive radiation
14
Q
Recombination
A
- Recombination of genes due to crossing over during meiosis is also
responsible for bringing about genetic variability among the individuals
of the same species, thus, contributing to the heritable variation.
15
Q
Natural Selection
A
- Natural selection is a guiding or driving force, which utilizes (mutations)
and gives a direction to the evolutions. - Harmful mutations are eliminated or suppressed while mutants with
better survival value are preferred and encouraged. Hence, natural
selection is the dynamic force for speciation.
16
Q
Reproductive Isolation
A
- Isolation plays a great role in speciation and particularly in preserving
the identity of a particular species. - Various isolating mechanisms operate in nature to isolate small groups
of a population reproductively so they can not breed freely. - Related species are also isolated from each other which prevents hybrid
formation. - Isolations may be geographical, ecological, or reproductive. But the last
one is the most important from evolutionary viewpoint.
17
Q
Genetic Drift
A
- Genetic drift is a mechanism of evolution in which allele frequencies of a
population change over generations due to chance (sampling error). - Genetic drift occurs in all populations of non-infinite size, but its effects are
strongest in small populations. - Genetic drift may result in the loss of some alleles (including beneficial
ones) or rise to %100 frequency of other alleles. - Genetic drift can have major effects when a population is sharply reduced
in size by a natural disaster (bottleneck effect) or when a small group splits
off from the main population to found a colony (founder effect)
18
Q
Hardy- Weinberg principle/Equilibrium
A
- A set of 5 assumptions which when satisfied can enable the determination of allele and
genotype frequencies of a population. - These frequencies will also remain constant for future generations.
- The principle was discovered by Godrey Hardy and Wilhelm Weinberg in 1908, based on
Gregor Mendel’s Law of Segregation.
19
Q
Five assumptions of H-W p/e are?
A
- No natural selection:
There are no evolutionary pressures which may favour a particular allele. - Random mating:
Each individual in a population mates randomly so that mating with an individual
carrying a particular allele is not favoured. - No mutations:
There are no DNA mutations occurring for the alleles which may affect their function. - A closed population:
Individuals within the population do not leave and new individuals are not introduced
to the population. - Large population size:
The population is considered large enough so that major changes in allele frequencies
do not cause a genetic drift.
- If any of these five assumptions are not satisfied, then the principle cannot be
applied. - All of these assumptions do not occur at the same time in nature therefore the
situations for which these calculations are undertaken are hypothetical.
