Classification and evolution Flashcards
phylogenetic classification
Phylogenetic classification arranges species into groups according to their evolutionary origins and relationships
It tells us how closely related species are and how recent their shared common ancestors are.
phylogenetic tree
Lineus classification hierarchy
classification systems are an example of a hierarchy
-smaller groups arranged within larger groups
-no overlap between groups
-each group called a taxa
species, genus, family, order, class, phylum, kingdom, domain
binomial system
each species is universally identified using the binomial (two name).
First name is genus, second name is species eg homo sapiens
the five kingdoms
-kingdom after domain
-prokaryotae
-protoctista
-fungi
-plantae
-animalia
prokaryotae
Unicellular, no membrane-bound organelles, small ribosomes, a ring of DNA with no associated proteins. It has no feeding system, instead it absorbs nutrients across its surface or some photosynthesise.
protoctista
Unicellular, does have a nucleus and membrane-bound organelles, sometimes have
chloroplasts and some have cilia or flagella for movement. Nutrients are absorbed either by photosynthesis, ingestion of other organisms or some are parasites.
fungi
Can be unicellular or multicellular, have a nucleus and membrane-bound organelles, no chloroplasts, cannot move, have a body made of threads or hyphae.Nutrients are absorbed from dead and decaying matter (they are saprobionts).
Food can be stored as glycogen.
plantae
Multicellular, have a nucleus and membrane-bound organelles, have chloroplasts and don’t move. Nutrients are absorbed by photosynthesis and food is stored as starch.
animalia
Multicellular, have a nucleus and membrane-bound organelles, no chloroplasts and
they can move using cilia, flagella or muscles. Nutrients are obtained by ingestion and food can be stored as glycogen.
changes of classification systems
Advances in technology have improved the accuracy of classification, and therefore some classification systems have changed.
• Classification used to be just based on observable characteristics.
This can be misleading as members of the same species can look very different if they live in different habitats with very different environmental conditions.
• Members of different species can also look very similar if they share a habitat and are exposed to very similar environmental conditions.
• The accuracy of classification improved due to advances in immunology and genome sequencing.
changes of classification systems
DNA base sequences.
The DNA base sequence of organisms for common genes can now be compared as a measure of how closely related organisms are.
The more closely related the species, the higher the degree of similarity in the base sequences.
This is because mutations accumulate over time, and those species must have evolved from a common ancestor longer ago and therefore have had more time to
accumulate different mutations resulting in more different
The sequence of amino acids
The sequence of amino acids in a polypeptide chain of proteins can also be compared because this sequence is determined by the sequence of DNA bases.
changes of classification systems
Carl Woese proposed a change to the classification system in 1977, introducing an extra taxa, domain.
In 1990 three domains were added to the clarification system: archaea, bacteria and eukaryota (eukaryote). Organisms are split into these three domains based on the type of rRNA and ribosomes they have and the cell membrane structures.
Under this system, there are six kingdoms.
The prokaryotae kingdom is split into eubacteria (true bacteria) and archaebacteria.
• Eubacteria are found everywhere and most bacteria within this kingdom.
• Archaebacteria live in extreme environments, such as thermal hot springs and anaerobic environments.
evolution
• Natural selection is the process that leads to evolution.
• Initially proposed by Wallace in 1858, when he submitted his ideas to Darwin to be peer-reviewed.
• Darwin had been aboard the HMS Beagle prior to this, conducting his own studies into the theory (Darwin’s finches on each Galapagos Island)
• As Wallace’s ideas were so similar to Darwins, they worked together to publish scientific journals in 1858 on this, and later Darwin independently published ‘On the Origin of Species’ in 1856.
evidence for the theory of evolution
Darwin’s theory was very controversial and it wasn’t widely accepted as it went against the current societal beliefs and religious beliefs. However, it is now widely accepted due to fossil, DNA and molecular evidence.
• Fossils are imprints or remains of dead animals and plants in rocks from and evolution in a range of ways.
and evolution in a range of ways. the fossi record provides evileetice of how species have changed over time and how species have evolved.
• By comparing DNA base sequences of common genes, or other molecular evidence (RNA or amino acid sequences we can examine how closely related different species are. This has enabled scientists to
scentists to
estimate the point in history when two species shared a common ancestor. Cytochrome C is a protein found in mitochondria, which a large number of species have. This is often the protein or gene that is compared.
adaptations
Evolution results in a species that is better adapted to its environment. Adaptations can be classified as either anatomical, physiological or behavioural.
Anatomical adaptations are internal or external physical features.
Behavioural adaptations are changes in the ways organisms act. These can be genetic in cause or learnt from parents.
Physiological adaptations are processes that take place within an organism.
• Organisms from different taxonomic groups may have similar anatomical adaptations. For example, the marsupial mole and the placental mole. This is due to convergent evolution. When different species are exposed to similar selection pressures (eg environmental conditions) then they will undergo natural selection for similar alleles and therefore become more genetically similar.
