Hugo de Vries proposed the mutation theory of evolution, which stated that new species arise through sudden mutations rather than gradual changes. Gene mutations, which are changes in DNA sequences, can cause genetic variation and drive evolution. Point mutations change single nucleotide base pairs, while insertions/deletions add or remove base pairs. Mutations can arise due to environmental factors or errors in cell division. Over time, genetic changes through mutations and natural selection can lead populations to diverge into new species through reproductive isolation or converge as unrelated species evolve similar traits.

1. BIOLOGICAL
SCIENCE
• Mutation Theory of Evolution
• Gene Mutation as Cause of Change
• Species and Speciation
• Divergence and Convergence

2. Mutation
Theory:
Mutation
Theory of
Evolution by
Hugo De vries’

3. • Hugo de Vries (1848—1935),a
Dutch botanist, one of the
independent rediscoveries of
Mendelism, put forward his
views regarding the formation
of new species in 1901. He also
met some of the objections
found in Darwin’s theory.
• According to him, new species
are not formed by continuous
variations but by sudden
appearance of variations,
which he named as mutations.
Hugo de Vries stated that
mutations are heritable and
persist in successive
generations.
Mutation Theory: Mutation Theory of
Evolution by Hugo De vries’

4. Gene
Mutation as
cause of
Change

5. Gene Mutation as cause of Change
• Gene Mutation
Genes are segments of DNA located on chromosomes . A
gene mutation is defined as an alteration in the sequence of
nucleotides in DNA . This change can affect a single
nucleotide pair or larger gene segments of a chromosome.
DNA consists of a polymer of nucleotides joined together.
During protein synthesis, DNA is transcribed into RNA and
then translated to produce proteins. Altering nucleotide
sequences most often results in nonfunctioning proteins.
Mutations cause changes in the genetic code that lead
to genetic variation and the potential to develop disease.
Gene mutations can be generally categorized into two types:
point mutations and base-pair insertions or deletions

6. Point Mutations
• Point mutations are the most common type of gene
mutation. Also called a base-pair substitution, this
type of mutation changes a single nucleotide base
pair. Point mutations can be categorized into three
types:

7. Three types of Point Mutations:
• Silent Mutation
Although a change in the DNA sequence occurs, this type of mutation does not change the protein that
is to be produced. This is because multiple genetic codons can encode for the same amino acid. Amino
acids are coded for by three nucleotide sets called codons. For example, the amino acid arginine is
coded for by several DNA codons including CGT, CGC, CGA, and CGG (A = adenine, T = thymine, G =
guanine and C = cytosine). If the DNA sequence CGC is changed to CGA, the amino acid arginine will still
be produced.
• Missense Mutation
This type of mutation alters the nucleotide sequence so that a different amino acid is produced. This
change alters the resulting protein. The change may not have much effect on the protein, may be
beneficial to protein function, or may be dangerous. Using our previous example, if the codon for
arginine CGC is changed toGGC, the amino acid glycine will be produced instead of arginine.
• Nonsense Mutation
This type of mutation alters the nucleotide sequence so that a stop codon is coded for in place
of an amino acid. A stop codon signals the end of thetranslation process and stops protein
production. If this process is ended too soon, the amino acid sequence is cut short and the
resulting protein is most always nonfunctional.

9. Base-pair Insertions/Deletions
• Mutations can also occur in which nucleotide
base pairs are inserted into or deleted from
the original gene sequence. This type of gene
mutation is dangerous because it alters the
template from which amino acids are read.
Insertions and deletions can cause frame shift
mutations when base pairs that are not a
multiple of three are added to or deleted from
the sequence. Since the nucleotide sequences
are read in groupings of three, this will cause a
shift in the reading frame. For example, if the
original transcribed DNA sequence is CGA CCA
ACG GCG ..., and two base pairs (GA) are
inserted between the second and third
groupings, the reading frame will be shifted.

10. Types of Insertion/Deletions:
• Original Sequence:
CGA-CCA-ACG-GCG
• Amino Acids Produced:
Arginine - Proline - Threonine - Alanine
• Inserted Base Pairs (GA):
CGA-CCA-GAA-CGG-CG
• Amino Acids Produced:
Arginine - Proline - Glutamic Acid – Arginine
The insertion shifts the reading frame by two and changes the amino
acids that are produced after the insertion. The insertion can code for a
stop codon too soon or too late in the translation process. The resulting
proteins will be either too short or too long. These proteins are for the
most part defunct.

11. Gene Mutation Causes
• Gene mutations are most commonly caused as a result of
two types of occurrences. Environmental factors such as
chemicals, radiation, and ultraviolet light from the sun can
cause mutations. These mutagens alter DNA by changing
nucleotide bases and can even change the shape of DNA.
These changes result in errors in DNA replication and
transcription.
Other mutations are caused by errors made
during mitosis and meiosis . Common errors that occur
during cell division can result in point mutations and frame
shift mutations. Mutations during cell division can lead to
replication errors which can result in the deletion of
genes, translocation of portions of chromosomes, missing
chromosomes, and extra copies of chromosomes.

12. Genetic Disorders
• According to the National Human Genome
Institute, most all disease have some sort of
genetic factor. These disorders can be caused
by a mutation in a single gene, multiple gene
mutations, combined gene mutation and
environmental factors, or by chromosome
mutation or damage. Gene mutations have been
identified as the cause of several disorders
including sickle cell anemia, cystic fibrosis, Tay-
Sachs disease, Huntington disease, hemophilia,
and some cancers.

13. Species
and
Speciation

14. Species and Speciation
Species are distinctly different
kinds of organisms. Birds of one
species are, under most
circumstances, incapable of
interbreeding with individuals of
other species. Indeed, the
"biological species concept"
centers on this inability to
successfully hybridize, and is what
most biologists mean by "distinctly
different." That concept works
very well when two different kinds
of birds live in the same area. For
example, Townsend's and Yellow-
rumped Warblers are clearly
distinct kinds because their
breeding ranges overlap, but they
do not mate with one another. If
they did, they might produce
hybrid young, which in turn could
"backcross" to the parental types,
and (eventually) this process could
cause the two kinds of warblers to
lose their distinctness.

15. SPECIES
• There are millions of species that inhabit this planet,
and each of those species plays a unique role. Some
species are important disease vectors, some are
keystone members of ecosystems, some are
agricultural pests, some are university students...the
list goes on and on.
• It's important to think about species, because they
are the basic unit of study in most areas of biology,
including: evolutionary biology, ecology, virology,
paleontology, genetics, and conservation biology. As an
example, studying the transmission of malaria would be
virtually impossible without knowing which mosquito
species were vectors, which species they prefer to
feed on, and which species of Plasmodium they carry.

16. What is Speciation?
If species aren’t special
creations, where do new
species come from? Darwin
found the answer by
concluding that lineages
change over time and also
multiply – they split in two.
For Darwin, and all who
followed, speciation is this
process of multiplication,
occurring when one
population splits into two
reproductively isolated
populations

17. Convergence
and
Divergence

18. Convergence
Convergent evolution describes the independent evolution of similar
features in species of different lineages. Convergent evolution
creates analogous structures that have similar form or function, but
that were not present in the last common ancestor of those
groups.[1] The cladistic term for the same phenomenon is homoplasy,
from Greek for same form.[2] The recurrent evolution of flight is a
classic example of convergent evolution. Flying insects, birds,
and bats have all evolved the capacity of flight independently. They
have "converged" on this useful trait.

19. Divergence Divergent evolution, as
described in conventional
evolutionary theory, is a relative
phenomenon in which initially
similar populations accumulate
differences over evolutionary
time, and so become increasingly
distinct (i.e., they "diverge").
This process also known simply
as "divergence," was described
in the Origin of Species (1859)
and was the subject of the
single illustration (see figure
right) contained in that book.
Even before Darwin, Alfred
Russel Wallace (1858) wrote of
the "many lines of divergence
from a central type."