MRS COLVILLE MOD 4

• Why do scientists classify organisms?

  • to identify species
  • to predict characteristics
  • to find evolutionary links
  • A single classification system enables scientists worldwide to share their research.
• Classification – placing living things into groups according to their shared similarities
• Taxonomy – the study of differences between species. These differences can be used to classify species into groups. Similar species go in the same group.
• Phylogeny – the study of how closely related species are based on evolutionary relationships. Can be represented as an evolutionary tree.
• Species - A group of organisms, with similar morphological

   physiological, biochemical and behavioural  

  features, which can interbreed to produce fertile offspring.
• Species

  • They are capable of breeding to produce fertile offspring (i.e. they belong to the same gene pool)
  • They have common ancestry (i.e. they have arisen by adaptation of an existing species)
  • They have similar genes ( therefore closely resemble one another  biochemically & anatomically)
  • They occupy the same ecological niche.
• 8 levels (taxa) in current classification systems (largest to smallest)

  1. domain
  2. kingdom
  3. phylum
  4. class
  5. order
  6. family
  7. genus
  8. species
• Binomial naming

  • The first part indicates the genus to which the organism belongs
  • The second word is the species to which the organism belongs. This part of the name is never used on its own.
• • We can now classify organisms more effectively due to technological advancements, such as studying certain large biochemical molecules that are found in all living things. 
  • They perform the same function but vary slightly. These differences reflect the evolutionary history of the species.
  • Cytochrome c ( a protein used in respiration) and DNA are examples of 2 molecules that have been studied.
• Cytochrome c

  • Used in respiration 
  • so in all organisms
  • Can have different amino acid sequence
  • Shows evolutionary relationships between species
• Shared DNA

  • The percentage difference in coding DNA can be used to determine evolutionary history.
• Changes to Classification:

  New molecular comparisons  and other developments in technology have led to changes to the classification system.

  Originally there were just two kingdoms - plants and animals (Aristotle) based on differences visible to the naked eye.

  Improvements in technology, including microscopy and chemical analysis led to a higher level of organism being instated: Domains.
• Originally there was 2 domains which organisms were classified into:

  1. Prokaryotes
  2. Eukaryotes

  These 2 domains were divided into 6 kingdoms:

  1. Plants
  2. Animals
  3. Fungi
  4. Protists
  5. Eubacteria
  6. Archaebacteria
• 6 kingdoms

  A) bacteria

  B) archaea

  C) Eukarya

  D) Eubacteria

  E) Archaebacteria

  F) Protoctista

  G) plantae

  H) fungi

  I) animalia

  
• classification systems:

  A) Bacteria

  B) Archaea

  C) Eukarya

  D) Eubacteria

  E) Archaebacteria

  F) Protoctista

  G) fungi

  H) plantae

  I) animalia

  J) prokaryote

  K) Protoctista

  L) fungi

  M) plantae

  N) animalia

  
• Biodiversity is the variety of living organisms, over time the variety of life on Earth has become more extensive but now it is being threatened by human activity such as deforestation and agriculture as well as climate change.
• Biodiversity can be measured in:

  • Species richness is the number of different species in a community
  • Other methods of sampling include systematic sampling eg: transect
  • Opportunistic sampling, a sample is taken when a source is encountered, it is based on ease of access
  • Stratified sampling is where the population is divided into smaller groups known as strata based on common characteristics
  • Species evenness is a comparison of abundance of different species in a habitat
  • Genetic diversity is a measure of the genetic variation found in a species, number of alleles in a gene pool.
• Biodiversity can also be measured using the index of diversity (D) which can be calculated as following:

  D = Diversity index

  N = total number of organisms

  n = total number of organisms of each species

  
• Maintaining biodiversity is important for ecological, economic and aesthetic reasons such as protecting landscapes. There are various methods of conserving biodiversity including in situ methods such as marine conservation zones and wildlife reserves which serve to protect the wildlife. Whereas ex situ conservation methods include zoos, seeds banks and botanic gardens.
• Methods to conserve endangered species and genetic diversity


  • Scientific research
  • Captive breeding programmes
  • Reintroduction programmes
  • Education programmes
• Scientific research

  • Studying the behaviour of animals
  • Working on improving breeding success to increase population size
  • Controlling and eradicating diseases
• Captive breeding programmes

  • Endangered species are carefully bred to increase genetic diversity and population size
• Reintroduction programmes

  • Aim to release animals bred in captivity into their natural habitat and restore lost habitats
• Education programmes

  • Educate people about the importance of maintaining biodiversity, captive breeding programmes and illegal trade of animals
• Seedbanks store a large number of seeds in order to conserve genetic diversity and prevent plant species from going extinct. Storing seeds instead of plants means that a large variety of species can be conserved; it’s also cheaper than storing whole plants as it takes up less space. The seeds are stored in cool, dry conditions as this maximises the amount of time they can be stored for and they are periodically tested for viability.
• Classification

  A) Kingdom

  B) Phylum

  C) Class

  D) Order

  E) Family

  F) Genus

  G) Species

  
• Classification is the process of naming and organising organisms into groups based on their characteristics. Organisms can be grouped into one of the five kingdoms: animals, plants, fungi, prokaryotes and protoctists. They can then be grouped further into phylum, class, order, family, genus and species. Each species is named according to the binomial system, the first part of the name is the genus and the second part of the name is the species.
• The analysis of molecular differences in different organisms to determine the extent of their evolutionary relatedness is known as molecular phylogeny. The data obtained by molecular phylogeny (looking at DNA sequences, RNA sequences and protein structure) has been accepted by scientists and this gave rise to new taxonomic groupings – all organisms can be separated into one of the three domains: Bacteria, Archaea and Eukaryota.
• Evolution

  The niche of a species is its role within the environment. Species which share the same niche compete with each other and a better adapted species survive. The idea that better adapted species survive is the basis of natural selection.
• Organisms are adapted to their environment in various ways:

  • Anatomical adaptations are physical adaptations, either external or internal e.g. presence of loops of Henlé which allow desert mammals to produce concentrated urine and minimise water loss
  • Behavioural adaptations are changes in behaviour which improve the organism’s chance of survival e.g. mating calls
  • Physiological adaptations are processes inside an organism’s body that increase its chance of survival e.g. regulation of blood flow through the skin
• Natural selection is the process in which fitter individuals who are better adapted to the environment survive and pass on the advantageous genes to future generations. Evolution is the process by which the frequency of alleles in a gene pool changes over time as a result of natural selection.
• Evolution via natural selection:

  • There’s a variety of phenotypes within a population
  • An environmental change occurs and as a result of that the selection pressure changes
  • Some individuals possess advantageous alleles which give them a selective advantage and allow them to survive and reproduce
  • The advantageous alleles are passed on to their offspring
  • Over time (and many generations), the frequency of alleles in a population changes and this leads to evolution
• If two populations become reproductively isolated, new species will be formed due to accumulation of different genetic information in populations over time due to different environments and selection pressures.
• Evidence for Evolution

  Observations:

  Charles Darwin's observations have provided evidence for the theory of evolution. Darwin observed many different types of finch on the Galapagos Islands but he believed they must be related due to many similarities. He concluded a bird born with a beak more suited to the food available would be more likely to survive than one whose beak was less well suited. Those that survive pass the trait to their offspring. Alfred Wallace had very similar ideas to Darwin and they published their theory together.
• Evidence for Evolution

  Fossils – looking at the remains of extinct organisms and comparing to those alive today. Dating the rocks can give a timeline to the changes seen.
• Evidence for Evolution

  Molecular biology – looking at the similarities and differences between DNA sequences in different organisms

  Comparative anatomy – comparing the anatomy of different organisms by looking at homologous structures (do species share a similar physical structure?)
• Variation

  • Each population shows natural variation in characteristics.
  • Discontinuous variation is where there are no intermediates. These are represented by bar charts. Most characteristics showing discontinuous variation are controlled by a single gene.
  • Continuous variation is when a characteristic can take any value within a range (such as height of animals). These are represented by histograms and usually display a normal distribution curve. These characteristics tend to be controlled by more than one gene and are often influenced by environmental factors.
• A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance
• Species Diversity

  • the number of different species and individuals within each species in a community
• Genetic Diversity

  • the variety of genes amongst all the individuals in a population of one species