Unit 2- Section 6 Classification Flashcards
What is a hierachy?
It is a system where smaller groups are contained within larger groups. Organisms can only belong to one group at each level in the taxonomic hierachy. There is no over lap
List the Severn categories in order for a species to belong in
Kingdom Phylum Class Order Family Genus Species
What is a species?
It is a group if similar organisms able to reproduce to give fertile offspring
Why do scientists keep updating the classification system?
Discoveries about new species and new evidence about already known organisms
What is phylogenetics?
It is the study of the evolutionary history of groups of organisms. It tells us who is related to who and how closely related they are. All organisms have evolved from shared common ancestors. Closely related species diverged away from each other most recently
Why is phylogenetics closely related to classification?
The grouping of organisms reflects their evolutionary relationships
What are the problems with classification?
Scientists can have problems when using the definition of a species to decide which species am organism belongs to or if it is a new distinct species. This is because you can’t always see their reproductive behaviour, why?
- they’re extinct
- they reproduce asexually
- there are practical and ethical issues involved. You can’t see species reproduce in the wild and you can’t study them in a lab because it is unethical
How do scientists now prove classification?
Scientists can now compare the DNA of organisms to see how related they are. The more DNA they have in common the more closely related they are. But there is no strict cut of point to say how much shared DNA can be used to define a species.
How are species named?
Species are given a scientific name to distinguish them from similar organisms. This is always a two word name in Latin
The first is the genus name and the second is the species name
This then helps scientists communicate across the world and there is no barrier for confusion
How are species classified using DNA or proteins?
Species can be classified into different groups in the taxonomic hierachy based on similarities and differences in their genes. This can be done by comparing their DNA sequence or by looking at their proteins. Organisms that are more closely related will have a much more similar dan and proteins than distantly related organisms.
Describe comparing DNA by DNA sequencing
The DNA of organisms can be directly compared by looking at the order of the bases in each. Closely related species will have a higher percentage of similarity of their DNA base order
What has DNA sequencing led to?
New classification systems for plants
Describe DNA hybridisation
It is used to see how similar DNA is without sequencing it
- DNA from two different species is collected, separated into single strands and mixed together
- where the base sequences of the DNA are the same on both strands hydrogen bongs form between the base pairs by specific base pairing. The more DNA bases that bond together, the more alike the DNA is
- the DNA is then heated to separate the strands again. Similar DNA will have more hydrogen bonds holding the two strands together so a higher melting temperature will be needed to separate the stands
How can you compare proteins by comparing Amino acid sequences?
Proteins are made up of amino acids. The sequence of amino acids in a protein is coded for by the base sequence in DNA. Related organisms will have similar DNA sequences and so similar amino acid sequences in their proteins
How can you compare proteins by comparing immunological comparisons?
Immunological comparison involves using antibodies to determine how similar two proteins are. Antibodies bind to proteins in a specific manner so similar proteins will bind with the same antibodies
