Biology - M3

• Selection pressures are environmental factors that determine which traits are favoured for survival and reproduction within a population
• The frequency of alleles can change over time due to natural selection, genetic drift or gene flow
• Gene flow refers to the movement of genes between populations through migration or interbreeding.
• Mutation is a spontaneous change in DNA sequence that may result in new alleles being introduced into a population.
• Natural selection occurs when certain individuals with favourable traits survive and reproduce more than others, leading to an increase in those favoured traits in future generations.
• Bottleneck effect is when a large population experiences a sudden decrease in numbers, reducing its overall genetic diversity.
• Distribution of a species is where it is found. Abundance of a species determines how many individuals of that species within a certain area/ecosystem.
• Abiotic factors are non-living environmental conditions such as temperature, light intensity, water availability, pH level, etc.
• Biotic factors are living components of an ecosystem including other plants and animals.
• An environment is all biotic and abiotic factors that surround or affect an organism, species, or ecosystem.
• An ecosystem refers to a community of living things interacting with each other and also their physical surroundings in a specific area.
• Abundance is specifically the density or presence within a particular area - population is a total count of individuals of a species within a defined geographical area

  Essentially: 100 deer p/km2 of forest vs 10000 deer in the whole forest
• General to specific:

  Ecosystem → community → population → habitat → niche
• Adaptations: Any feature or characteristic that helps organisms survive. They can be divided into 3 categories:

  - Structural

  - Physiological

  - Behavioural
• Nastic movement - plant movement in response to environmental stimulus
• Tropism - movement in reaction to directional stimulus
• Halophytes - Plants that grow in high-salinity areas
• Dehydrin - Antifreeze protein. Stops water from freezing and damaging leaf.
• Plants that grow in areas with little to no water are called xerophytes.
• Thigmonasty - leaves move to protect themselves

  Photonasty - may be “following” sun

  Thermonasty - flowers open/close at certain times based on temperature needs
• Vasodilation - a physiological adaptation. Heat is released via dilated capillaries.
• Darwin's finches were an example of divergent evolution, more specifically; adaptive radiation. Adaptive radiation is generally smaller scale changes that create new species.
• Favourable trait = variation

  Environment = selection pressure

  Frequency of the allele = generational change
• Speciation - The formation of a new and distinct species in the course of evolution
• Species Rules - Same species can interbreed and offspring can reproduce
• Allopatric Speciation - Geographical boundary separates population and genes change too much
• Sympatric Speciation - Same area, different barriers. Can be separated into prezygotic and postzygotic
• Prezygotic

  - Behavioural isolation

  - Temporal Isolation - different breeding times

  - Habitat - different habitat

  Postzygotic

  - Offspring is very weak

  - Embryo can’t develop

  - Offspring can’t reproduce
• Microevolution is the small allele variations within a species whereas macroevolution is the allele changes at a species or above level

  - An accumulation of microevolutionary changes

  - Creation of new species - results in speciation (microevolution does not)
• Morphological Changes

  • Gradual change
  • Doesn’t always result in a new species
  • Slow constant
• Punctuated Equilibrium

  • Rapid change
  • No fossil record of evolution
  • No gradual change
  • Constant selection pressure
  • Equilibrium with their environment
• Divergent Evolution

  • Causes: genetic drift, natural selection
  • One common ancestor creates many new species → speciation
  • Creates favoured traits, traits chosen
• Convergent Evolution

  • Unrelated species, common selection pressure
  • Unrelated species evolve to become vaguely similar species because of their environmental selection pressure
• Biochemical Evidence

  • Study of structure + functions of chemicals found in living organisms; nucleic acids, proteins, amino acids, etc.
  • If organisms are closely related biochemistry shows proteins or DNA will be shared or similar
  • Amino acid sequences
• Comparative Anatomy

  • Similar basic structures
  • Implies a shared common ancestor and then divergent evolution
  • Evolved to survive selection pressures
• Comparative Embryology

  • Comparing Embryos
  • Also comparing developmental stages
  • All vertebrate embryos have gill slits or arches, notochords, spinal cords or primitive kidneys.
  • Vertebrates also have the same type of skin in the early stages of development. Depending on the species, the skin will develop into fish scales, reptilian scales birds will develop feathers, claws and nails on mammals.
  • Similar to comparative anatomy - basic structures seen in embryos
• Biogeography

  • Study of the distribution of living things
  • Looks at fossils from Pangea era - shows similar ones across continents
  • Also proof of Theory of Tectonic Plates
• Fossil Dating

  • Relative Dating
  • Index fossil - looking at fossils and using their timeframe of existence as a starting point to date a layer of the Earth/strata
  • Absolute Dating
  • Carbon dating - Measuring the amount of carbon-14 present and getting a rough idea of the object's age
• Antibiotic Resistance

  • Resistance happens because of natural selection → some bacteria just gets less doses of antibiotics
  • Large population → some are naturally resistant → survive and reproduce creating more resistant bacteria
  • Staphylococcus aureus (golden staff) was the first major resistant pathogen + first found to be resistant to penicillin