3. Evolution

1. Theory of evolution of the species

2. Theory of a common descent

3. Theory of the multiplication of species

4. Theory of gradualism

5. Theory of natural selection

6. Theory of sexual selection

The world is constantly changing, it isn’t recently created nor has a repetitive cycle. Therefore organisms must transform in time.

All species including animals, plants, and microorganisms, ultimately go back to a single origin of life, every group of organisms descended from a common ancestor.

New species arise by the splitting of existing species into two or more new ones.

• separation of species

• Divergence over time

Evolutionary change takes place through the gradual change of populations and not by the sudden production of new individuals that represent a new type.

Species change over time because individuals with advantageous traits are more likely to survive and reproduce, passing those beneficial characteristics to their offspring.

Intrasexual competition and intersexual competition results in phenotypic difference in gender dimorphism.

• Natural selection: Individuals with advantageous traits survive and reproduce more, causing those traits to become more common.

• Genetic Drift: Random changes in allele frequencies, especially in small populations (e.g., by chance events or bottlenecks).

• Migration (Gene Flow): Movement of genes between populations through migration, which introduces new alleles and reduces differences between populations.

• Mutation: random changes in DNA that create new gentic variants. Mutation is the original source of all new genetic information.

• Mutations: DNA changes, creates new alleles

• Gene Flow: adds variation by introducing alleles from other populations

• Recombination during sexual reproduction: shuffles genes

Macroevolution describes large-scale evolutionary changes above the species level (formation of new species).

• It is defined as the change between species, not within species (microevolution).

• All life is connected and can be traced back to one common ancestor.

Evidence comes from

• fossil records

• comparative anatomy

• molecular similarities

  all of which show patterns of common ancestry and long-term evolutionary changes.

Microevolution refers to small-scale genetic changes within a population over short time periods, such as changes in allele frequencies.

Driving molecular mechanisms are:

• Mutation (creates new genetic variants)

• Migration (brings new alleles into a population)

• Genetic drift (random changes, especially in small populations)

• Natural selection (different survival and reproduction of variants)

Any change in the DNA.

• Insertion mutation

• Deletion mutation

• Nonsense mutation

• Missense mutation

• Frameshift mutation

• Repeat expansion mutation

A single nucleotide is inserted into the original DNA code, which results in an incorrect amino acid sequence. This can produce a malfunctioning protein and disrupt the gene’s function.

A single nucleotide is deleted from the original DNA code, which may shorten or completely alter the gene.

A normal codon is changed into a stop codon, causing the protein to be cut off too early.

A single nucleotide is replaced, which results in a different amino acid in the protein.

An insertion or deletion shifts the reading frame, changing all downstream amino acids.

A short DNA sequence is repeated too many times, disrupting gene function.

For example a repeated trinucleotide (CAG) adds a string of glutamines (Gin) to the protein.

Duplication of a short stretch of DNA, creating an extra copy of the sequence.

Mechanisms:

• unequal crossing-over, where chromosomes incorrectly swap DNA during reproduction, leaving one chromosome with an extra gene.

• retrotransposition, where a gene’s messenger RNA (mRNA) is copied back into DNA and reinserted somewhere else, making a special copy called a retrogene.

Significance:

Redundant new genes may acquire new functions by mutation.

Mechanism:

An entire set of chromosomes is duplicated, often due to errors in meiosis or mitosis.

Significance:

Provide a huge amount of new genetic material (massive gene duplication), may create new species.

Flipping of a chromosome segment resulting in a change of gene order along chromosomes.

Mechanism: breaks in DNA caused by radiation or other insults.

Significance: Alleles inside the inversions are likely to be transmitted together, as a unit

All organisms were created by God during six days of creation:

• species do not change in time

• were created independently of one another

• were created recently

• creation by a designer

Base pair substitutions in DNA sequences.

Mechanism: Chance errors during DNA synthesis or during repair of damaged DNA

Significance: creates new alleles

Haploid cells contain one complete set of chromosomes

Diploid cells contain two complete sets of chromosomes:

• 2 copies of each gene, 1 of each parent

• Small differences in DNA bases

• Unique features

• Alleles