topic 4

• biodiversity 


  the variety of living organisms

  over time the variety of life has become extensive but it now being threatened by human activity such as deforestation
• endemism


  the state of a species being unique to a particular geographic location, such as an island and not found anywhere else
• how can biodiversity me measured within a habitat?


  using species richness =the number of different species in a habitat
• genetic diversity


  a measure of the genetic variation found in a particular species/ the number of alleles in a gene pool
• how can biodiversity be measured within a species ?


  the Heterozygosity index:

  H= number of heterozygotes/ number of individuals in the population
• how can biodiversity be compared between habitats?


  using the diversity index (D):

  D= diversity index

  N= total number of organisms

  n= total number of organisms in each species

  
• niche 


  the ecological niche of a species is its role within the community

  • Species which share the same niche compete with each other; the better adapted will outcompete the other, forcing it to alter the niche it occupies - or it could die
  • the idea that better adapted species survive is the basis of natural selection
• anatomical adaptations 


  physical adaptations, either internal or external

  • e.g. presence of long loops of Henle which allow desert mammals to produce concentrated urine and minimise water loss
• behavioural adaptations 


  changes in behaviour which improve the organisms chance of survival

  • e.g. mating calls
• physiological adaptations 


  processes that increase an organism's chance of survival

  • e.g. regulation of blood flow through the skin
• natural selection 


  the process in which fitter individuals who are better adapted to the environment survive and pass on the advantageous allele to future generations.
• evolution 


  the process by which the frequency of alleles is a gene pool changes over time as a result of natural selection
• evolution through natural selection:


  • a variety of phenotypes exist within a population due to mutation
  • an environmental change occurs and as a result, 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 onto their offspring
  • over time the alleles frequency in the population changes
• The Hardy-Weinberg equation


  can b e used to estimate frequency of alleles in a population and to monitor changes in allele frequency

  
• conditions of the hardy Weinberg equation:


  • no mutations
  • random mating
  • large population
  • isolated population
  • no selection pressure
• allopatric speciation


  groups of organisms are geographically isolated
• sympatric speciation


  groups of organisms are isolated by other means within the same area
• classification


  a means of organising the variety life based on relationships between organisms using differences and similarities in phenotypes and genotypes and is built around the species concept
• 5-kingdom model for classification


  • animals, plants, fungi, protists, monera
  • within each kingdom they can then be further grouped into phylum, class, order, family, genus and species
• binomial naming system


  first part of name is the genus, second part of them name is the species

  e.g. Homo sapiens
• molecular phylogeny 


  the analysis of molecular differences in different organisms to determine the extent of their evolutionary relationship is known as molecular phylogeny

  • the data obtained by molecular phylogeny has been accepted by scientists and this gave rise to new taxonomic groupings - the 3-domain classification
• 3-domain classification


  • bacteria
  • archaea
  • eukaryota
  • monera are split between bacteria and archaebacteria
• how does the scientific community evaluate data:


  • the findings are published in scientific journals and presented at scientific conferences
  • scientists then study the evidence in a process called peer review
• plant cells 


  eukaryotic cells meaning they have a nucleus and membrane bound organelles. they also possess structures that aren't present in animal cells
• cell wall 


  made of cellulose.

  The cell wall is made of the middle lamella, which is made of calcium pectate and holds adjacent cells together and cellulose microfibrils and microfibres
• plasmodesmata 


  an extension of cytoplasm between the cell wall of adjacent cells involved in the transport of substances between them
• pits 


  thin sections of the cell wall which also allow communication between adjacent cells
• chloroplasts 


  the site of photosynthesis

  They contain stacks of thylakoid membranes called grana containing chlorophyll. The grana are connected by extensions of thylakoid membranes called lamellae. Grana are surrounded by fluid called the stroma which contains all of the enzymes required for photosynthesis. Chloroplasts are bound by double membrane called the envelope
• amyloplasts 


  organelles surrounded by a double membrane, which contain amylopectin (starch)
• vacuole


  contains cell sap and is surrounded by a tonoplast (single membrane) provides cell with strength and support
• structure of plant cell


  :

  
• carbohydrates 


  molecules that only consist of carbon, hydrogen and oxygen

  They are long chain of sugar units called saccharides: monosaccharides, disaccharides and polysaccharides

  Monosaccharides can join together to form disaccharides and polysaccharides by glycosidic bonds which are formed in condensation reactions
• cellulose 


  component of cell walls in plants and is composed of long, unbranched chains of beta glucose which are joined by glycosidic bonds.

  • microfibres formed of microfibrils are strong threads which are made of long cellulose chains joined together by hydrogen bonds and they provide structural support in plant cells
• vascular bundle 


  plants have a vascular bundle containing various components for transport and support
• xylem vessels 


  transport water and minerals, and provide structural support.

  • they are one cylinders made of dead tissue with open ends
  • xylem vessels are thickened with lignin
• phloem vessels 


  tubes made of living cells which are involved in translocation, which is the movement of food substances and nutrients from leaves to storage organ
• cambium cells 


  between xylem and phloem, are undifferentiated and able to specialise as plant grows
• schlerenchyma fibres 


  provide structural support

  • short structures made of dead cells with a hollow lumen and end walls. They are thickened with lignin
• parenchyma cells (pith)


  act as packing between other cells and vessels
• structure of vascular bundle 


  :