Classification Flashcards
What are the problems of basing a classification based on morphological similarities?
- Two species may have similar features due to adapting to the same environment but they still may be different species, so biochemical analysis and DNA analysis would be used.
What are the problems of basing a classification on interbreeding?
Two organisms that would not usually mate in the wild may produce offspring, but the offspring may not be fertile
What are the problems of basing a classification on ancestry?
Ancestry is hard to determine and can only be done with DNA and Protein sequence analysis which is not always accurate.
What is speciation?
The process of new species being created when one existing species is split into two reproductively isolated subspecies. (E.g. Due to geographical isolation)
Who made up the hierarchical structure?
Carolus Linnaeus
How does hierarchical structure work?
Organisms with similar characteristics are grouped together, which are grouped within larger composite groups etc. with each rank of groups having specific names
What is a pneumonic for remembering the order of ranks in the hierarchical structure?
King Peter Calms Overly Frustrated Gay Saxophonists
What are the names of the ranks in the hierarchical structure?
Kingdom Phyla Classes Orders Families Genera Species
What is Binomial nomenclature?
A system of naming species beginning with a generic name with a capital letter (e.g. Panthera) and a specific name (e.g. tigris)
What is a group of similar organisms at any level called and what is the name for the science of classification?
A taxon, taxonomy.
What are the characteristics used by taxonomists to determine phylogenies?
- Morphology; visible structures like number of legs
- Ultrastructure; microscopic cell features
- Embryology; Stages of embryo development from a zygote to an adult
- Palaeontology; structure and age of fossils
- Ethology; behaviour patterns (animals only)
- Biochemistry; metabolic pathways used by an organism
- Molecular Biology; DNA or protein sequence analysis
What are phylogenies?
Family trees which represent true evolutionary relationships rather than convenient groupings.
What type of DNA is used for classification and why?
Coding DNA because these gene sequences tend to be very similar within species and very different between a species.
What are the three aspects of a species?
- They share a common ancestor
- They can breed together to produce fertile offspring but not other species.
- They are similar in appearance, behaviour and biochemistry and have the same ecological niche
What is an simple and quick method of comparing DNA?
DNA Hybridisation
What is the method for DNA Hybridisation?
- Extract DNA from two species
- Heat DNA to break H bonds and separate strands
- mix DNA from both species in one tube, put DNA from just one in the other tube
- cool DNA to allow base pairs to form between strands. Complementary base pairs will match while mismatched sequences will not
- warm slowly and measure the amount of single stranded DNA every 2 degrees C
- determine the temperature at which 50% of DNA has separated into single strands
What is the significance of how many base pairs are formed in the mixed DNA of DNA hybridisation?
The more base pairs formed, the more similar the DNA
What is the significance of similarities between T(50)H values in DNA hybridisation?
The more similar the t50h value, the more similar the DNA. A difference of 1C equates to 1% of difference between the base sequences.
Apart from looking at DNA sequence what can we use to investigate phylogenies?
Protein sequencing (Typically using haemoglobin and cytochrome c as they are found in all animals) and courtship behaviours
How does protein sequencing work?
It is based on the specific binding of antibodies from one species to proteins of other species, causing agglutination. If similar amounts of precipitate is formed between the antibodies of one species with its own proteins and another species proteins, they are similar
What things do courtship behaviours allow animals to do?
- Recognise their own species
- Attract the opposite sex
- Identify a mate that is capable of breeding
- Synchronise egg and sperm production
- Form a pair bond to help raise offspring
Comparing the base sequence of genes provides more evolutionary information than
comparing the structure of proteins. Explain why
- The base sequence is longer than the amino acid sequence
- Introns/non-coding DNA can be compared as well
- Degenerate code means more than one codon can code for the same amino acid
