A3.1 Diversity

• Organism


  Any biological system that functions as an individual life form. All organisms are composed of cells.
• Population


  A group of organisms of the same species in the same area. Even though they are the same species, the individual organisms of the population vary from each other.
• Community


  The populations of two or more different species occupying the same geographical area at the same time. There is great variation between different species.
• Variation


  Differences between members of a group. Variation can be discrete or continuous.
• Discrete variation


  • Traits that can be put into distinct qualitative categories, usually influenced by only one or a few genes, can also be influenced by the environment, although usually not significantly.
• Discrete variation


  • Hand used for writing (left or right)
  • Snapdragon petal colour (red, white or pink)
  • Blood type (A, B, AB or O)
• Continuous variation


  Traits that vary along a qualitative continuum, result from complex interaction between many different genes (polygenic) often with the environment playing a significant part in the expression of the phenotype.
• Continuous variation


  • Height
  • Body mass
  • Milk yield of cow
  • Root length of plant
• Levels of biological variation

  • Molecular, such as between genomes
  • Cellular, such as between specialised cells in multicellular organisms
  • Organisms, such as in the speed of nerve impulses
  • Ecosystems, such as between biomes
• Intraspecies variation


  Variation within a species, which is inheritable and transmitted from parents to offspring.
• Causes of genetic variation within a species

  • Mutation = the changes in the sequence of genes in DNA
  • Gene Flow = The movement of genes between different groups of organisms
  • Meiosis = formation of egg and sperm, which leads to the creation of new combinations of genes
  • Sexual reproduction= random fertilisation between egg and sperm
• Gene variation in a population of organisms

  Enables some organisms to survive better than others in the environment they live in, resulting in individuals being more likely to reproduce and pass on their beneficial variation
• Natural selection


  The differential survival and reproduction of organisms, which is a part of the process that drives evolution.
• The amount of variation between individual organisms depends on how closely related they are to each other. Individuals within the same species will have less variation than those classified as different species.
• Species


  A group of living things recognizably distinct from all others by their shared characteristics.
• The Latin word 'species' originated, meaning "a class of individuals or things of a particular sort, kind, or type".

  Late 14th century
• The reference to a group of living things recognizably distinct from all others by their shared characteristic came about.

  About 1600
• Linnaeus's system of classification

  The first formal system of grouping organisms.
• Carl Linnaeus, a Swedish botanist, zoologist, taxonomist, and physician, formalised a system of grouping and naming organisms.


  1707-1778
• Linnaeus and other naturalists of the time period grouped organisms into species based strictly on 'morphology', the clearly distinguishable shape and forms of organisms.
• Technological and scientific knowledge advanced, biologists understood the grouping of organisms based on morphology alone has limitations.
• Genetically diverging population may be hard to distinguish as unique species, and morphologically similar groups may be the result of convergent evolution and not actually the same species.
• Binomial nomenclature


  The system of naming species using two terms, the first indicating the genus and the second indicating the specific species.
• There are rules about the formation of binomial nomenclature, such as the genus name beginning with a capital letter and the species name beginning with a lowercase letter, and the name being in italics (or underlined if handwritten).
• Biological species concept


  Species are defined as members of a population that can interbreed in nature to produce fertile offspring.
• The biological species concept has challenges, as it doesn't really apply to all organisms that reproduce asexually.
• Niche


  Where an organism lives and what it eats, which is important for microbes.
• Genetics


  DNA sequence similarity.
• Evolutionary lineage


  Common ancestors.
• Speciation


  An event that produces two new species, which requires the population to become isolated from each other.
• As speciation happens gradually, it can be challenging to determine when it has occurred.
• Karyogram


  An image of the chromosomes in an organism.
• Karyotype


  Information about the species, number of chromosomes, and sex of an organism.
• Humans have 46 chromosomes, while chimpanzees have 48 chromosomes, and the last common ancestor was around 6 million years ago.
• The hypothesis that two ancestral chromosomes fused to form human chromosome 2 is supported by evidence from the structure, band patterns, centromere position, and gene sequence of the chromosomes.
• Genome


  All the genetic information in an organism.
• Gene sequencing


  The identification of the order of all the bases (A, T, C, G) in the genome of an organism, which allows for comparison of different species to understand evolutionary relationships and personalized medicine.
• Dichotomous key


  A tool used to identify a species based on observable traits, where each step gives two distinct choices that lead to the correct identification.
• Developing a dichotomous key

  1. Select species

  2. Pick a characteristic that could divide the selected organisms into two groups

  3. Pick a characteristic that divides the organisms in that group into an additional two groups

  4. Continue down the branching key until only one organism remains on each branch

  5. Add numbers to the branching key and create the written key by following the numbers