Classification

• Classification

  The process of placing species into groups according to their evolutionary origins and relationships
• Binomial system

  A system that uses the genus name and the species name
• Binomial system - example


  Homo (genus) + sapiens (species)

  
• Taxonomic Hierarchy

  Smaller groups can fit into a larger group and there is no overlap

  
• (DOMAIN) King Phillip Came Over For Good Soup - Taxonomic Hierarchy


  (DOMAIN) Kingdom, Phylum, Class, Order, Family, Genus, Species

  
• Species

  Group of organisms that can reproduce to produce live, fertile offspring. For example, horses and donkeys are separate species as they can reproduce, but do not produce fertile offspring (mule)
• Why do scientists classify organisms?

  - To identify specifics

  - Predict characteristics

  - Find evolutionary links
• Phylogeny

  Evolutionary relationships and history between organisms
• Relationship between phylogeny and classification

  Classification uses knowledge of phylogeny to confirm the classification groups are correct or need to change
• The Five Kingdoms

  Prokaryotae, protoctista, fungi, plantae, animalia
• Prokaryotae


  - No nucleus

  - Circular loops of DNA

  - No membrane-bound organelles

  - Smaller than eukaryotes

  - Have 70s ribosomes

  - Absorb nutrients from the environment or photosynthesise
• Animalia

  - Eukaryotic

  - Multicellular

  - Has membrane-bound organelles

  - Heterotrophic (ingest/eat other organisms)

  - No cell wall

  - Uses glycogen as a store of glucose

  - Move usually through muscle contraction (but also cilia waft)
• Plantae

  - Eukaryotic

  - Multicellular

  - Cellulose cell wall

  - Autotrophic (photosynthesise)

  - Contain chlorophyll

  - Uses starch as a store of glucose

  - Do not usually move (but venus flytrap do, for e.g.)
• Fungi

  - Can be multicellular or unicellular

  - Eukaryotic

  - Walls made out chitin

  - Saprophytic: They cause decay of organic matter

  - Uses glycogen as a store of glucose

  - Cannot move
• Protoctista

  - Eukaryotic

  - Mostly single-celled (some can be multicellular)

  - Have autotrophic or heterotrophic feeding - some photosynthesise and some ingest prey
• Carl Woese

  Proposed domain which is higher than kingdom. This system has a 3 domain name system:

  - (Domain) Bacteria, (Kingdom) Eubacteria

  - (Domain) Archaea, (Kingdom) Archae bacteria

  - (Domain) Eukarya, (Kingdom) Prokaryotae, Animalia, Plantae, Fungi, Protoctista
• Changes in classification system

  - Classification used to be based off observable characteristics.

  - However, this is misleading as members of the same species can look very different, if they live in different habitats and different environments and conditions.

  Just as well, members of different species can look very similar if they share a habitat and/or are exposed to similar environmental conditions.

  - This has led to the 3 domain name system
• Accuracy of classification has improved due to...

  Advances in immunology and genome sequencing
• DNA Base Sequence


  The more closely related the species are, the higher degree in similarity of the base sequence.

  - Due to accumulation of mutations over time as all species have a common ancestor
• Evidence for Evolution

  Natural selection is the process that leads to evolution in organisms.

  Charles Darwin went on an expedition on the HMS Beagle to South America and the Galapagos Islands. He collected lots of plant and animal specimens to send to the UK, these included finches. Darwin proposed that the shape of the beak evolved depending on the food available. For example if there was a habitat where there are lots of hard seeds and a bird with a short large beak for cracking open the seeds. The bird is more likely to survive and reproduce in this habitat compared to a bird with a thin beak. The offspring are more likely to inherit large beaks and over time finches with a large beak become common in that habitat

  Wallace was interested in the warning colours of insects and how species form. He proposed a similar theory to Darwin
• Why was Darwin's theory controversial and why is it now accepted?

  Darwin's theory was very controversial and wasn't widely accepted due to religious beliefs. However it is now widely accepted due to fossil, DNA and molecular evidence
• Fossils


  Fossils Imprints or remains of organisms usually embedded in rock

  - Fossil records provide evidence to how species have changed over time and how they have evolved.

  - They also show how complex organisms have evolved from simple organisms
• DNA


  By comparing DNA base sequences of common genes we can examine how closely related the species are. This has allowed scientists to estimate the point in history when 2 species shared a common ancestor
• Divergent Evolution

  A process by which groups of organisms from the same common ancestor evolve and accumulate differences. This results in the formation of new species
• Adaptations


  Evolution results in species that have better adapted to an environment.

  - Anatomical

  - Physiological

  - Behavioural
• Anatomical Adaptations


  Internal or external physical features. For example the streamlined shape of dolphins (to help move rapidly in water)
• Behavioural Adaptations


  The way behaviour changes in an organisms. This can be genetic (web-building in spiders) or learnt from parents (some species of primates use sticks to probe for insects)
• Physiological Adaptations


  Processes that take place within an organism
• Convergent evolution


  The process in which unrelated species are exposed to similar selection pressures and they undergo natural selection for similar alleles and become more genetically similar
• Genetic and Environmental Variation

  - Genetic: Random fertilisation, mutations, crossing over, independent assortment

  - Environmental: Could be scars from operations (not inherited) and in plants it could depend on the soil
• Intraspecific variation


  Genetic variation between the same species. This can be through mutations, crossing over, random fertilisation. For example, variation in cat fur.
• Interspecific variation


  Genetic variation between different species
• Continuous variation


  Traits controlled by many genes and the environment can have an impact
• Discontinuous variation


  Traits are controlled by a single gene and the environment has no impact
• Selection Pressures


  Factors that affect the survival of organisms in an environment
• Evolution by natural selection

  1) Random mutations create new alleles for a gene

  2) If the new allele increases the chance of survival of an organism (a new, advantageous allele), they are more likely to reproduce and survive

  3) The new, advantageous allele is passed onto offspring

  4) As a result, over many generations, the new allele increases in frequency in the population
• Evolution by natural selection - Context (Snowshoe hare)

  In any population of organisms, there will be genetic variation. Every snowshoe hare will be slightly different from others. Mutations constantly take place in a population and many are harmful. However in some cases, a mutation can lead to a new, advantageous allele. For example, a mutation that allows a hare to have better hearing, this would allow them to detect predators. This means the hare is more likely to survive and reproduce (the hare without the advantageous allele is more likely to be killed by the predator).

  When the hare with the advantageous allele reproduces, the allele will be passed onto their offspring and the offspring is more likely to survive and reproduce. Over time the advantageous allele will become widespread over the population (increasing the gene pool) and natural selection can lead to the development of new species.
• Natural selection: Antibiotic resistance

  Natural selection led to the development of antibiotic bacteria. The presence of antibiotics was the selection pressure that drove natural selection
• Natural selection: Insects treated with pesticides


  Over time the presence of pesticides is the selection pressure that drove natural selection. This has led insects to be resistant to many different chemical pesticides.