Notes : 5.17 + 5.19 - Natural selection, Evolution and speciation Flashcards
Define the term evolution
The frequency of an allele in a population changes over time due to natural selction
Explain the process of evolution by natural selection
- M : Random mutation causes alternative version of a gene whihc leads to differnt allels.
- V : This creates genetic variation between individuals of the same species (intraspecific variation)
- A : A selection pressure occurs which means that organisms on the most adapted to their environment survive and reproduce. ( Bacteria don’t reproduce the multiply or instead say that they reproduce asexually in an exam)
- A : Passing on the advantageous allele.
- T : Over time the frequency of the beneficial allele increases from generation to generation
Name all the evidence you know for evolution
- Genomics (required to know)
- Proteomics (required to know)
- DNA hybridisation
- DNA profiling/fingerprinting
- Protein sequencing
- Fossils
How does genomics provide evidence for evolution ?
- DNA technology is used to determine the base sequence of an organism genome.
- This allows scientist to make comparisons between organisms DNA.
- If the bases sequences are similar of two species they are closely related and share a common ancestor,
- If the base sequences are less similar for two species they are not closely related.
What is proteomics
The study of proteins
How does proteomics provide evidence for evolution
- The sequence of amino acids in a protein is coded for by the DNA sequence in a gene
- Related organisms have a similar DNA sequences and so similar amino sequences in their protein
- The amino acid sequences of some proteins are very similar across many different species;this indicates common ancestry.
The level of similarity between amino acid sequences of equivalent proteins can give a
measure how long ago two species diverged from each other Knowing how long ago a species diverged from a common ancestor enables scientists to establish the relationships between organisms
How does DNA hybridisation provide evidence for evolution
- If we mix a 2 single strand of DNA from two different species together their DNA stands will nybrisies together forming hydrogen bonds with complementary bases creating a double helix
- Species that are similar will form more hydrogen bonds as they have similar base sequencing.
- A Lot of energy will be required to break these bonds
- We know that if the temperature required to break these bonds are higher then the species are closely related as there bases sequeung is similar causing them to have more hydrogen bonds.
- Conversely, if it separates easily at lower temperatures, it suggests that the species are more distantly related.
How does fossils provide evidence for evolution ?
Fossils provide a record of how creatures evolved and how this process can be represented by a ‘tree of life’, showing that all species are related to each other.
The role of the scientific community in validating new evidence
- Scientific journals
- Peer review process
- Scientific conferences
Blurt everything you know about Scientific journals
- Scientist publish their new discoveries
Blurt everything you know about Peer Review
- Scientist check that studies are carried out in
such a way that results will be valid, and that results have been analysed
appropriately e.g.by the use of the correct statistical tests. - Check that it supports conclusions
Blurt everything you know about conferences
- A scientific conference is a gathering of scientists in a particular field of study from all over the world
- Scientists can present their findings for questions and discussion
Conference Members have the opportunity to speak with each other about their work and to share ideas and concerns
What is speciation
The development of a new species
How does speciation occur ?
- When populations of the same species become reproductively isolated, reducing gene flows (transfers between genes) between two populations.
What causes variation
- Mutations
- Independent assortment
- Crossing over