Diversity of organisms

• When analysing markets, a range of assumptions are made about the rationality of economic agents involved in the transactions
• The Wealth of Nations was written

  1776
• Rational


  (in classical economic theory) economic agents are able to consider the outcome of their choices and recognise the net benefits of each one
• Rational agents will select the choice which presents the highest benefits
• Consumers act rationally by


  Maximising their utility
• Producers act rationally by


  Selling goods/services in a way that maximises their profits
• Workers act rationally by


  Balancing welfare at work with consideration of both pay and benefits
• Governments act rationally by


  Placing the interests of the people they serve first in order to maximise their welfare
• Groups assumed to act rationally


  • Consumers
  • Producers
  • Workers
  • Governments
• Rationality in classical economic theory is a flawed assumption as people usually don't act rationally
• Marginal utility


  The additional utility (satisfaction) gained from the consumption of an additional product
• If you add up marginal utility for each unit you get total utility
• Speciation can occur when gene flow does not occur between two populations of the same species
• The process of speciation occurs over very long time periods, and the differences between isolated populations accumulate incrementally
• In most cases it is likely that the ability of two populations to interbreed successfully declines gradually, rather than a sudden cut-off point occurring, meaning that it is difficult to pinpoint the stage at which two separate populations have become two new species
• The decision as to when to assign separate species status to two populations can therefore seem arbitrary, and is often down to the opinions of scientists, i.e. it is subjective
• Killer whales (Orcinus orca)


  • Show significant variation between populations, and are currently said to consist of several 'ecotypes', but some scientists believe that there could in fact be more than one species of orca
• Diploid cell


  A cell that contains two complete sets of chromosomes (2n)
• Haploid cell


  Contains one complete set of chromosomes (n), meaning that they have half the number of chromosomes compared to normal body cells
• In most cases these haploid cells are called gametes and they are involved in sexual reproduction
• During fertilisation the nuclei of haploid gametes fuse together to form the nucleus of a diploid zygote
• Both gametes must contain the same number of chromosomes in order for the zygote to be viable
• Every body cell that arises from the zygote will contain the same number of chromosomes
• Exceptions to this include red blood cells, which have no nucleus and so contain no chromosomes
• Chromosome number is halved in gametes, and restored to diploid after fertilisation
• The number of chromosomes possessed by different species varies and is dependent upon changes that have occurred during that species' evolution
• Each individual in a species always has the same number of chromosomes
• There are a few rare instances where a chromosome mutation has occurred, giving a different chromosome number
• Differences in chromosome number is one reason why organisms from different species are unable to breed together successfully
• The diploid number must always be an even number
• The number of chromosomes a species possesses is not linked to how 'advanced' a species is in evolutionary terms
• Humans have 46 chromosomes, while chimpanzees have 48
• Gorillas and bonobos also have 48 chromosomes
• A whole pair of chromosomes must be removed for 48 chromosomes (24 pairs) to become 46 (23 pairs)
• Testable hypothesis


  • There needs to be access to evidence that supports it or refutes it
  • The hypothesis needs to be a testable statement
  • The hypothesis should not contain vague statements that use terms like 'may' or 'could'
  • A hypothesis should not make predictions
  • A hypothesis should not draw causal conclusions
• Humans share around 99.9 % of their DNA with other humans
• Humans share around 99 % of their DNA with chimpanzees
• Humans in fact share all of their coding genes with other humans; the differences between individual humans are due to possessing different alleles of genes
• Single nucleotide polymorphisms (SNPs)


  Differences between DNA sequences that involve a single base change
• Mitochondrial DNA and chloroplast DNA


  Included in the genome of eukaryotic cells