Topic 3.1 Classification Flashcards
Principles of classification
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What do scientists use to classify?
-Anatomical/physical features eg. pentadactyl limb
-Fossil evidence
-Biochemical analysis of proteins
-Biochemical analysis of DNA/RNA
Phylogenetic
The study of evolutionary history and the relationships among or within groups of organisms.
Binomial names
Two parts:
-Genus; uppercase letter (generic name)
-Species; lowercase letter (specific name)
Written in italics (or underlined)
Why classify?
We need an internationally recognised way of referring to any particular living organism.
We solve these problems by classifying the living world, putting organisms in groups based on their similarities and differences.
(A good classification system will also make ancestral relationships clear).
What is taxonomy?
-The science of describing, classifying and naming living organisms
-People often use analogous features to classify organisms (features that look similar and have the same features, but aren’t of the same biological origin
The main taxonomic groups:
The archaea domain;
Archaebacteria
Ancient bacteria thought to be early relatives of the eukaryotes.
They were thought to be found in extreme environments, but scientists are increasingly finding them everywhere- particularly in soil.
Normally reproduce asexually.
The main taxonomic groups:
The bacteria domain;
Eubacteria
The true bacteria are what we normally think of when we are describing the bacteria that cause disease, and which are so useful in the digestive systems of many organisms and in recycling nutrients.
They normally reproduce asexually.
The main taxonomic groups:
The eukaryotic kingdoms;
Protoctist
Very diverse group of microscopic organisms.
Some are heterotrophs (eat other organisms) and some are autotrophs (make their own food by photosynthesis).
Some are animal-like, some are plant-like and some are like fungi.
They normally reproduce asexually.
The main taxonomic groups:
The eukaryotic kingdoms;
Fungi
Contains multicellular and unicellular organisms.
All heterotrophs.
Most are saprophytic and some are parasitic.
They have chitin, not cellulose in their cell walls.
The main taxonomic groups:
The eukaryotic kingdoms;
Animalia
All heterotrophs that move their whole bodies around during at least one stage of their life cycle.
These include the invertebrates; eg. insects, molluscs, worms etc and the vertebrates; eg. fish, amphibians, reptiles, birds, mammals.
The main taxonomic groups:
The eukaryotic kingdoms;
Plantae
All multicellular.
Almost all autotrophs (makes own food by photosynthesis).
Both sexual and asexual reproduction occurs.
The binomial system
Originally used by Linnaeus, is now used universally among biologists.
The fist name is the genus and the seconds name is the species or specific name which identifies the organism precisely.
A genus
A genus is a group of species that all share common characteristics, but enough differences for you to see why they are a separate species.
It is not always easy to tell species within a genus apart.
Biochemical relationships
-Biochemical relationships are increasingly being used to support or clarify the relationships based on morphology (eg. counting hairs on the foreleg of a fly)
-Scientists need to analyse the structures of many chemicals as well as the DNA to identify the inter relationships between groups of organisms
-This is known as phylogeny
-Proteins are key molecules in these analyses
Gel electrophoresis- method
-A variation of chromatography which can be used to separate DNA and RNA fragments, proteins or amino acids according to their size and charge
-The chemical to be compared are placed in wells in a gel medium in a buffering solution, with known DNA or RNA, proteins or amino acids to aid identification.
Gel electrophoresis- results
For identifying DNA:
-Add DNA fragments to a gel dye (which will fluoresce when placed under UV light)
-An electric current is passed through the DNA moves towards the. positive anode (because of the negative charge on the phosphate groups)
-Once electrophoresis is complete, the plate is placed under UV light; the DNA fluoresces so the pattern of the different bands can be identified.
Breed
A group of animals of the same species that have different characteristics that make them different to other members of that species.
Variety
A group of plant of the same species that have different characteristics that make them a different to other members of that species.
The Biological Species concept
A group of organisms that freely interbreed to produce fertile offspring.
Speciation
Speciation occurs when a group within a species separates from other members of its species and develops its own unique characteristics.
Modified species definition
-A group of organisms with Simi;ar characteristics that are all potentially capable of breeding to produce fertile offspring
-A group of organisms in which genes can flow between individuals
Genetic species model
-Based on shared evolutionary relationships between species.
-In this model, members of a species have a shared evolution and are evolving together.
-It is not easy to apply as there is not always a clear evolutionary pathway for a particular organism.
Mate-recognition model
A concept based on unique fertilisation systems, including mating behaviour. The difficulty with this is that many species will mate or cross-pollinate other species and may even produce fertile offspring, but nevertheless different species.
Ecological species model
Based on the ecological niche occupied by an organism. This is not a very robust way of identifying species, as niche definitions vary and many species occupy more than one niche.
The reasons why species must be identified
-Identifying a species in which an organism belongs to is a very useful biological tool
-They allow people throughout the world to communicate with each other about certain species
-It also help with newly identified species which has not yet been classified
-Information Technology (IT) plays a vital role in this classification using identification apps or instruments that could identify DNA
The importance of DNA
-In DNA sequencing the base sequences of the genome of an organism is worked out
-DNA sequencing can reveal lots of genetic information, helping to identify genes as well as mutation that can cause disease
-DNA sequencing leads to DNA profiling which looks at non-coding areas of DNA to identify patterns
-These patterns are unique to individual but the similarities of patterns can be used to identify relationships between individuals and sometimes even between species.
DNA profiling
-Looks at non-coding areas of DNA to identify patterns
-Similarity of patterns used to identify relationships between individuals and species
-May be used in crime scenes by taking a sample of DNA from the crime scene and comparing it to DNA of suspects
Bioinformatics
-Is the development of software and computing tools needed to organise and analyse raw biological data
-It makes sense of and uses information generated in DNA sequencing and profiling
-Can compare entire genomes and look for where mutations have resulted in divergence in the phylogenic tree
Food crime
-Caviar is a luxury food customers would most likely pay a lot of many for
-Beluga caviar is the most expensive and best kind
-Scientists discovered through DNA profiling that a quarter of tins claiming to contain beluga caviar and charging a premium price for them actually contains a different, lower quality caviar belonging to a different species.
DNA barcodes
A method of species identification using a short section of DNA to form a specific gene or genes.
(It looks at short genetic sequences from a common genome of a particular group of organisms)
What is evolution?
The process by which different kinds of living organisms are believed to have developed from earlier forms during the history of the earth.
Fossil DNA and human evolution
Scientists can extract DNA for fossils under 100,000 years old and analyse it using the polymerase chain reaction (which amplifies minute traces of DNA) and profiling.
—> Comparing DNA from Neanderthal fossils and DNA of modern humans has shown that neanderthals aren’t our direct ancestors (interbreeding between the two did take place)
DNA, lice and human evolution
-Modern humans have 3 types of parasitic lice: head lice, pubic lice and body lice
-Head lice and body lice are related to chimpanzee lice
-Pubic lice is related to gorilla lice
-DNA evidence suggests human had head lice with chimpanzee louse ancestors (they evolved from chimpanzee louse), and pubic lice have gorilla louse ancestors, long before they began wearing woven clothes and body lice evolved
-So the ability to weave clothes was developed long after most of our body hair was lost
New models support old theories
Scientists use evidence from the DNA analysis of many species to help build diagrams that model the evolution of species from a common ancestor.
The role of the scientific community
-When an article is submitted to a scientific journal it goes through a process of peer review, where it is read by a number of experts to see if its reliable and can be published.
(A paper should provide enough information for other scientists to carry out similar investigations so conclusions can be validated)
-At scientific conferences scientists working on the same field get together to discuss ideas
How can we analyse evolutionary relationships genetically?
1) Gel electrophoresis
2) DNA sequencing
3) Bioinformatics
How does DNA sequencing work?
DNA is broken into small fragments, terminated at different lengths by fluorescently marked nucleotides, then duplicated using PCR. The fragments undergo gel electrophoresis, with the smallest fragments travelling furthest, meaning we can read the base sequence of the fragment according to distance travelled.
