Biology topic 4

• Describe the Process of Evolution

  Natural genetic variation creates diversity in a species

  a selection pressure makes the allele advantageous

  organisms with the advantageous allele are more likely to survive and reproduce

  the allele is passed onto offspring

  over generations, the advantageous allele frequency increases
• Anatomical Adaptation 


  structures which are observed / dissected which help with survival and reproduction
• Behavioural Adaptation 


  an action by an organism which helps them survival and reproduce
• Inbreeding Depression

  Closely related individuals breed resulting in an increase of recessive alleles and reduced genetic diversity
• Genetic Diversity / Variation

  measures number of different alleles present in a gene pool
• Taxonomy

  The process of grouping organisms based on similarities

  Kingdom > Phylum > Class > Order > Family > Genus > Species
• Autotroph 


  an organism which can produce its own food
• key features of plant kingdom organisms

  multicellular eukaryotes which are autotrophs ; have cell walls
• Archaea

  one of the 3 domains (Carl Woese) closely related to the Eukaryota domain
• Species evenness

  distribution of abundance across a species in a community
• Species richness

  total number of different species present in a habitat
• Describe the structure and role of xylem

  Hollow dead tubes carrying water and mineral ions.

  Lignin makes them strong and waterproof.

  Pits are for lateral water movement and perforated ends for water movement.
• Describe the structure and role sclerenchyma fibres

  hollow, dead, lignified tubes for structural support
• Describe the structural role of lignin

  Strong waterproof material in xylem and sclerenchyma.
• Retting

  Plant stems are submerged under water, microorganisms break down soft tissues leaving the cellulose.
• Clinical trial phase 2

  A small group of patients, used to test for effectiveness of the drug.
• Starch gelatinisation

  Starch molecules absorb water and swell when heated
• Seed banks

  clean dry and store seeds at -20C to store them

  drying prevents damage from water expansion when frozen

  prevent growth of microorganisms
• Seed Banks uses

  restore habitats

  study medicinal properties of plants

  conserve endangered species
• Source cell 


  cells which are photosynthesizing and make photosynthesis products e.g. a leaf cell
• Sink cell 


  cells which store of use photosynthesis products e.g. root cells
• Speciation process 


  Reproductive isolation e.g. via geographical isolation

  Gene flow is prevented between populations

  Different selection pressures act on populations

  Advantageous alleles more likely to survive and reproduce

  Over time 2 populations become genetically different

  New species when no longer can interbreed to produce fertile offspring
• 3 phases of clinical trials

  1 = small group of healthy volunteers test for side effects

  2 = small group of patients test effectiveness of drug

  3 = large group of patients in a double-blind randomised trial including a placebo
• Double-blind randomised trial

  Neither the researcher nor patients know which treatment they are getting - reduces bias
• Peer Reviewing 


  A scientific journal is checked by other scientists to check reliability and validity of conclusions - before publishing
• Binomial system

  First name: genus

  Second name: species
• Species 


  Organisms which can interbreed and produce fertile offspring.
• Niche


  the way in which an organism is adapted to its ecological community or ecosystem
• Physiological adaptation


  the inner workings of an organism are adapted to help them survive and reproduce
• 3 domains classification system (Carl Woese)


  Based on similarities/differences in DNA and RNA sequences

  Archaea, Eukarya, bacteria
• gene pool


  the total number of different alleles present in a population
• Describe the structure of cellulose


  Polysaccharide made of Beta Glucose containing 1,4 glycosidic bonds only and every other glucose is inverted

  Parallel cellulose chains have hydrogen bonds to form microfibrils
• Properties and role of cellulose

  makes cell walls strong
• Placebo 


  a version of a drug which contains no active ingredient
• control in an investigation

  there is no independent variable, it is used as a comparison to check the independent variable affects the dependent variable
• Allele Frequency

  the total number of times an allele is present within a population
• Genetic Drift 


  When some alleles are not passed onto offspring by chance, resulting in a loss of genetic variation over time.
• Phenotype 


  the set of observable characteristics of an individual due to interaction of the genotype with the environment
• Genotype


  the combination of alleles inherited from parents
• Phloem

  comprised of sieve tube elements and companion cells

  hollow tubes which carry sugars in a plant by translocation