Topic 5 - IB Biology

• Binomial system of nomenclature

  Each species is given two names: the first is the genus name (uppercase first letter) and the second is the species name (lowercase first letter). If printed, italics are used. If handwritten, it is underlined.
• Levels in the hierarchy of taxa

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Bryophytes


  • No roots, instead they have structures similar to root hairs called rhizoids. Mosses have simple leaves and stems.
  • Maximum height: 0.5 m
  • Spores are produced in capsule. The capsule develops at the end of a stalk.
• Filicinophytes


  • Have roots, leaves and short non-woody stems. Leaves are usually pinnate (divided into leaflets) and curled up in a bud.
  • Maximum height: 15 m
  • Spores are produced in sporangia, usually on the underside of the leaves.
• Coniferophytes


  • Shrubs or trees with roots, leaves and woody stems. Leaves are usually narrow with thick waxy cuticle.
  • Maximum height: 100 m
  • Seeds are produced from ovules on the surface of the scales of female cones. Male cones produce pollen.
• Angiospermophytes


  • Many different characteristics but usually have roots, leaves and stems. Stems of flowering plants that develop into shrubs and trees are woody.
  • Maximum height: 100 m
  • Seeds are produced from ovules inside the ovaries. The ovaries are part of the flower. The fruits then develop from the ovaries and disperse the seeds.
• Porifera


  • No clear symmetry
  • Attached to a surface
  • Pores through body
  • No mouth or anus
  • Example: sponges
• Cnidaria


  • Radially symmetric
  • Tentacles
  • Stinging cells
  • Mouth but no anus
  • Example: jellyfish
• Platyhelminths


  • Bilaterally symmetrical
  • Flat bodies
  • Unsegmented
  • Mouth but no anus
  • Example: tapeworm
• Annelida

  • Bilaterally symmetrical
  • Bristles often present
  • Segmented
  • Mouth and anus
  • Example: earthworm
• Mollusca


  • Muscular foot and mantle
  • Shell may be present
  • Segmentation not visible
  • Mouth and anus
  • Example: slugs and snails
• Arthropoda


  • Bilaterally symmetric
  • Exoskeleton
  • Segmented
  • Jointed appendages
  • Example: spiders and insects
• Evolution


  The frequency of favourable traits in a individual change in a population over time
• Types of evolution

  • Mutation
  • Natural selection
  • Genetic drift
  • Gene flow
• Natural selection


  Differential survival and reproduction of an individual with favourable traits in the current population
• Survival of the fittest misconception: fitness refers to the ability of how a species can survive, ability to find a mate, produce an offspring not how big or strong it is
• Steps in natural selection

  1. Overproduction

  2. Genetic variation

  3. Selective pressure

  4. Natural selection

  5. Increased frequency of favourable traits in a population over time
• Discrete variation


  Traits that can be put into a distinctive qualitative category, caused by one or a few genes and the environment can also play a role, represented by a bar chart, e.g. which hand is used to write with (left or right)
• Continuous variation


  Traits that can vary on a qualitative continuum, caused by complex interactions between many genes and the environment plays a big role, represented by a histogram, e.g. wide variety of heights
• Mutation

  A change in the DNA sequence, caused by errors in DNA copying, mutagens, viruses, ionising radiation. Germline mutations are passed down, somatic mutations are not.
• Meiosis

  An exchange of chromosome segments between homologous chromosomes, reshuffles the existing genetic variation in the population
• Independent assortment

  Genes for separate traits located on different chromosomes are passed independently from one another from parent to offspring, reshuffles the existing genetic variation in the population
• Segregation of alleles

  A diploid pair possesses a pair of alleles, due to segregation during meiosis the parent diploid pairs randomly pass a random allele to a gene, reshuffles the existing genetic variation in the population
• Sexual reproduction

  Random mating of organisms, there is limitless genetic combinations a organism of a species can have as there is no limit to the amount of times you can reproduce with a mate, reshuffles the existing genetic variation in the population
• Random fertilisation

  A genetically unique sperm produced by a male fertilises with a genetically unique egg produced by a female, reshuffles the existing genetic variation in the population
• Gene flow


  When an organism moves to a new population with new alleles, brings in new alleles to the population
• Modes of natural selection

  • Stabilising selection
  • Directional selection
  • Disruptive selection
• Ecological niche


  A habitat supplies the factors necessary for the survival of a species of an organism, including the physical and environmental conditions, interactions with other species, and activity patterns
• Fundamental niche


  An environment and resources a species could theoretically use - bigger
• Realised niche


  An environment and resources a species can/actually uses - smaller due to competition
• Intraspecific competition


  Competition within the same species
• Interspecific competition

  Competition between different species
• Specialists


  • Narrow niche, less adaptable, require special resources, more advantageous when the conditions stay consistent, more likely to become extinct
• Generalists


  • Wide niche, more adaptable, use a wide variety of resources, more advantageous when the conditions are constantly changing, less likely to be extinct, high tolerability
• Structural adaptations


  Body and structural anatomy adaptations necessary for the survival of the species in the niche
• Physiological adaptations


  Processes in the brain that help with the survival of the species in the niche
• Behavioural adaptations

  Behavioural processes that help with the survival of the species in the niche
• Homologous structures


  Similarities in different species that result from having a common ancestor, including structural, embryological, metabolic, and molecular sequence homologies, as well as vestigial homologies
• Pentadactyl limb

  The basic pentadactyl limb found in tetrapods that is adapted to serve specialised locomotory functions
• Leaf and flower homologous structures

  Plants that have leaves could have functions which are developed from other leaves, and flowers have homologous structures like carpels, stamens, petals, sepals, and receptacle