topic 4

• Biodiversity


  The variety of living organisms
• Over time the variety of life on Earth has become extete but is now being threatened by human activity such as deforestation
• Measures of biodiversity


  • Species richness - the number of different species in a habitat
  • Genetic diversity - the number of alleles in a gene pool
• Heterozygosity index


  The number of heterozygotes/number of individuals in the population
• Index of diversity (D)


  D = Σn(n-1)/N(N-1), where n is the total number of organisms of each species and N is the total number of organisms
• Endemism


  The state of a species being unique to a particular geographic location, such as an island, and not found anywhere else
• Ecological niche


  The role of a species within a community
• Species which share the same niche compete with each other; the better-adapted species will outcompete the other forcing it to alter the niche it occupies or it could die
• Types of adaptations


  • Anatomical - physical adaptations, either external or internal
  • Behavioural - changes in behaviour which improve the organism's chance of survival
  • Physiological - processes that increase an organism's chance of survival
• Natural selection


  Fitter individuals who are better adapted to the environment survive and pass on the advantageous alleles to future generations
• Evolution


  The process by which the frequency of alleles in a population changes over time as a result of natural selection
• A variety of phenotypes exist within a population due to mutation
• Evolution via natural selection


  1. Environmental change occurs

  2. Some individuals possess advantageous alleles which give them a selective advantage

  3. Advantageous alleles are passed on to offspring

  4. Frequency of alleles in population changes
• Hardy-Weinberg Equation


  Used to estimate the frequency of alleles in a population and to monitor changes in allele frequency
• Conditions of Hardy-Weinberg Equation

  • No mutations
  • Random mating
  • Large population
  • Isolated population
  • No selection pressure
• Speciation


  The formation of new species due to the accumulation of different genetic information in populations over time due to different environments and selection pressures
• Types of speciation


  • Allopatric - groups of organisms are geographically isolated
  • Sympatric - organisms are isolated by other means, within the same area
• Five kingdoms of classification

  • Animals
  • Plants
  • Fungi
  • Protists
  • Monera
• Binomial nomenclature


  The system of naming species, where the first part is the genus and the second part is the species
• Taxonomic levels


  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Molecular phylogeny is the analysis of molecular differences in different organisms to determine the extent of their evolutionary relationship
• Three-Domain model of classification

  The five kingdoms are sorted into one of the three domains: Bacteria, Archaea and Eukaryota
• The monera are split between the bacteria (eubacteria) and archaebacteria in the Three-Domain model
• Scientific evaluation of data

  1. Findings are published in scientific journals and presented at scientific conferences

  2. Scientists study the evidence in a process called peer review
• Plant cell structures


  • Cell wall
  • Plasmodesmata
  • Pits
• Thylakoid


  Contents of chloroplasts where chlorophyll is located
• Grana


  Stacks of thylakoid membranes in chloroplasts
• Stroma


  Colourless fluid surrounding the grana, contains enzymes required for photosynthesis
• Chloroplasts


  Organelles bound by a double membrane, contain chlorophyll
• Vacuole


  Contains cell sap, surrounded by a tonoplast, provides cell with strength and support
• Carbohydrates


  Molecules consisting of carbon, hydrogen and oxygen, long chains of sugar units called saccharides
• Types of saccharides


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Glycosidic bonds


  Formed in condensation reactions to join saccharides
• Cellulose


  Component of plant cell walls, composed of long, unbranched chains of beta glucose joined by glycosidic bonds
• Microfibrils


  Strong threads made of long cellulose chains joined by hydrogen bonds, provide structural support
• Components of plant vascular bundle


  • Xylem vessels
  • Phloem vessels
  • Cambium cells
  • Sclerenchyma fibres
  • Parenchyma cells
• Xylem vessels


  Transport water and minerals, provide structural support, made of dead tissue with open ends, thickened with lignin
• Phloem vessels


  Tubes made of living cells involved in translocation, movement of food substances and nutrients
• Cambium cells


  Undifferentiated cells between xylem and phloem, able to specialise as plant grows
• Sclerenchyma fibres


  Provide structural support, short structures made of dead cells with hollow lumen and end walls, thickened with lignin