B2 | Mindmap

Classification
1. Grouping organisms
  1. Kingdom, phylum, class, order, family, genus, species
  2. As you move down to species the fewer organisms are found within each group as they share more similarities
  3. Classified in two ways; Artificial system- based on one or two characteristics that make identification easier. Birds by the sea- sea birds
    1. Natural system- bases in DNA enable scientists to know how much more closely related organisms are, can be reclassified
2. Species
  1. Group of organisms that can interbreed to produce babies
  2. Named by the binomial system- two parts to name, first is genus and second is species. Genus part starts with capital letter, and species part starts with lower case
3. Problems with classifying
  1. Living things are at different stages of evolution, new ones being discovered all the time. Makes difficult to place organisms into distinct groups. Archaeopteryx- had characteristics which puts into two different groups... Feathers(bird) and teeth and tail like a reptile
  2. Present specific problems- Bacteria do not interbreed, reproduce asexually, can't be classed into different species
  3. Mules- hybrids, produced when members of two species interbreed. Infertile, can't be classed as a species
4. Classification and evolution
  1. Organisms that are grouped together usually closely related and share ancestors but have different features if they live in different habitats
  2. When classifying, important to bear in mind similarities and differences. Dolphins and fish- live in same habitat however dolphins are mammals. Dolphins and bats live in different habitats but are both mammals
Energy flow
1. Pyramids of biomass
  1. Pyramids of numbers and pyramids of biomass can be both used to represent feeding relationships between organisms in a food chain or web.
  2. Show the dry mass of living material at each stage of a food chain
  3. May look different to pyramids of numbers if producers are large or a small parasite lives on a large animal
  4. POB are a better way of representing trophic levels they are difficult to construct
    1. Some organisms feed on others from different trophic levels
    2. Measuring dry mass is difficult as it involves removing all the water from an organism, which will kill it
2. Energy flow
  1. As energy flows along the food chain some is used in growth. However, at each trophic level much of the energy is transferred into other, less useful forms such as; heat from respiration; egestion; excretion
  2. Material that is lost at each stage is not wasted. Most is used by decomposers
  3. Each trophic level loses up to 90% of the available energy, an animal at the end of the food chain doesn't have a lot of food available to it
  4. efficiency = energy used for growth / energy output
Recycling
1. The carbon cycle
  1. Carbon- one element found in living organisms
  2. Needs to be recycled so it can become available for other living organisms
  3. Carbon dioxide is removed by photosynthesis
  4. Feeding passes carbon compounds along a food chain or web
  5. Released in the air by plants and animals respiring/soil bacteria and fungi acting as decomposers/the burning of fossil fuels
  6. Absorbed by the air by oceans, marina organisms make shells made of carbonate, which then become limestone
  7. Carbon in limestone can return to air as carbon dioxide during volcanic eruptions or weathering
2. The nitrogen cycle
  1. Plants take in nitrogen as nitrates from the soil to make protein for growth
  2. Feeding passes nitrogen compounds along a food chain or web
  3. Nitrogen compounds in dead plants and animals are broken down by decomposers and returned to soil
  4. Number of microorganisms are responsible for the recycling of nitrogen
    1. Decomposers- soil bacteria which convert proteins and urea into ammonia
    2. Nitrifying bacteria convert the ammonia to nitrates
    3. Denitrifying bacteria convert nitrates to nitrogen gas
    4. Nitrogen-fixing bacteria living in root nodules fix nitrogen gas

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