Topic 4

• Middle lamella


  This forms the outermost layer of the plant cell and acts like glue to stick adjacent plant cells together

  It provides stability to the plant
• Pits


  These are very thin regions of the cell wall

  
  

  The pits in adjacent plant cells are lined up in pairs

  
  

  This facilitates transport of substances between cells

  
• Chloroplasts


  surrounded by a double-membrane

  
  

  Membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana (singular = granum)

  
  

  Chloroplasts are the site of photosynthesis:

  Certain parts of photosynthesis occur in thylakoid membranes, while other parts happen in the stroma

  
  

  Chloroplasts also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis

  
• Amyloplasts


  Small, membrane bound organelle containing starch granules

  They are responsible for storing starch in plants and converting it back to glucose when the plant needs it
• Vacuole and tonoplast


  The vacuole is a sac in plant cells surrounded by tonoplast

  Contains cell sap, mixture of different substances such as water, minerals,waste and enzymes

  Vacuoles functions: keep cells turgid,which stops the plant from wilting

  can break down and isolate unwanted chemicals in plant cells tonoplast controls what can enter and leaven the vacuole
• Abiotic factors


  Non living components of environment.
• biome


  major regions with a certain climate and therefore dominant organism
• Species


  a group of organisms with similar morphologies, physiology and behaviour which can interbreed and produce fertile offspring and which are reproductively isolated from other species
• Population


  a group of interbreeding individuals of the same species found in an area
• habitat


  Place where an organism lives
• Microhabitat


  A small part of an organisms environment where the conditions are suited to the animal
• niche


  the way an organism exploits its environment
• Endemism


  When a species is unique to a single place
• Species evenness


  the size of the populations relative to each other

  how many of each species are in a habitat
• species richness


  the number of species in a habitat
• ecosystem diversity


  the variety of different habitats within a given region
• Genetic diversity


  The difference in number and frequency of alleles in the gene pool of a population between a number of species.
• Species diversity


  the number of different species in a given area
• dominant organism


  a very common species in a habitat
• Heterozygosity Index


  = number of heterozygotes÷ number of individuals in the population
• Index of diversity


  = N(N-1) ÷ ∑n(n-1)
• Adaptation


  A trait or feature that helps an organism survive and reproduce
• behavioural adaptation


  organisms actions to allow survival or reproduction, usually in response to stimuli
• physiological adaptation


  where the internal workings of the organism help survival or reproduction
• anatomical adaptation


  structures observed or seen in dissection enabling the organism to survive
• Whats the competitive exclusion theory?

  If two species are fighting for the same resources, they cannot co-exist if other ecological factors are present. Even the slightest advantage can lead to dominate int he long term. this leads to the extinction of the submissive species
• Binomial system


  the way in which species are named

  a genus name + a definitive name
• Taxonomy


  the science of classifying organisms
• Taxonomic groups


  Kingdom

  Phylum

  Class

  Order

  Family

  Genus

  Species
• Natural Selection


  Struggle for existence results in winners and losers, winners survive as they, by chance, possess a characteristic that gives advantage

  
  

  The mechanism by which species change over time
• What's the process of natural selection?

  1. Organisms within a species show variation in their characteristics that are caused by differences in their genes

  
  

  2. Organisms whose characteristics are best adapted to a selection pressure have an increased chance of surviving and reproducing successfully. Less well adapted organisms die or fail to reproduce

  
  

  3. Successful organisms pass the allele encoding the advantageous characteristic onto their offspring. Organisms that possess the non-advantageous characteristic are less likely to pass it on

  
  

  4. This is repeated for every generation. Over time, the number with the advantageous adaptation increases. Therefore the frequency of the allele increases in gene pool

  
  

  5. Over very long periods of time & many generations, this can lead to the evolution of a new species
• Evolution


  A change in allele frequency in a population over generations
• Gene Pool


  all the alleles of all the genes present in a population. Some genes will be common, some will be rare
• Hardy-Weinberg equation


  p² + 2pq + q² = 1

  p + q = 1

  
  

  
  

  p = dominant,

  q= recessive

  
  

  2pq = heterozygous individuals

  
  

  p^2 = homozygous dominant

  
  

  q^2 = homozygous recessive
• limitation of Hardy-Weinburg


  Only valid if:

  population is large enough for no genetic drift

  no mutations

  random mating

  no natural selection

  the population is closed
• Genetic drift


  variation in the relative frequency of different genotypes in a population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.
• vacuole


  Cell organelle that stores materials such as water, salts, proteins, and carbohydrates
• Three domain classification


  Archaea, Eukaryotes, Prokaryotes

  Woese noticed a group of bacteria lacked RNA sequences typical of bacteria
• What's continuous variation?


  When the characteristic can have any value ( Length of hair)

  
  

  controlled by a few genes

  
  

  environment has little effect
• Whats discontinuous variation?


  When the characteristic can have only a limited set of values (Number of Legs)

  
  

  Controlled by many genes

  
  

  environment has significant effect