OCR 21st Century B3.2

OCR 21st Century B3.2

1. Life on Earth- Evolution &Biodiversity

   • Biodiversity and Sustainablility
     • Classification
       • organisms are classified into groups according to similarities and differences in characteristics including DNA and physical features (e.g. flowers in flowering plants and the skeleton in vertebrates)
         • Organisms are classified at different levels, and that these levels can be arranged in an order progressing from large groups containing many organisms with a small number of characteristics in common (e.g. kingdom) to smaller groups containing fewer organisms with more characteristics in common (e.g. species)
         • the classification of living and fossil organisms can help to:
           • make sense of the enormous diversity of organisms on Earth
           • show the evolutionary relationships between organisms
         • that biodiversity refers to the variety of life on Earth including:
           • the number of different species
           • the range of different types of organisms, e.g. plants, animals and microorganisms
           • the genetic variation within species
     • Why is biodiversity important?
       • The more plants we have, the more resources there are for developing new food crops
       • Many new medicines have been discovered using chemicals produced by living things. E..g digitalis, a drug used to treat heart disease was discovered by foxglove
     • Extinction
       • the rate of extinction of species is increasing and why this is likely to be due to human activity
         • maintaining biodiversity to ensure the conservation of different species is one of the keys to sustainability
         • hunting into extinction or introducing new predator
     • Sustainability
       • meeting the needs of people today without damaging the Earth for future generations
       • large-scale monoculture crop (one type of crop) production is not sustainable because it does not maintain biodiversity
       • How how sustainability can be improved
         • Using renewable materials
           • Packaging comes from non-renewable resources, e.g. plastic from crude oil. Materials like paper and card can be replaced once they've been used
         • Using less energy
           • Making packaging from recycled materials uses less energy than producing new materials. As less energy is required, less fossil fuels are burnt and so the environment isnt as dmaged
         • Creating less pollution
           • Plastics aren't biodegradable so microorganisms cannot break them down, therefore, they pollute the land for hundreds of years.
             • Even when biodegradeable materials are used, due to the lack of oxygen they take a while to break down. Less packaging
             • Also, making and transporting any packaging material uses up energy

2. Development of Life

   • Life on Earth began approximately 3500 million years ago
     • It evolved from very simple living things
       • there is variation between individuals of the same species
         • some of this variation is genetic so it can be passed on to offspring .
           • genetic variation is the result of changes that occur in genes (mutations)
             • mutated genes in gametes can be passed on to offspring and may occasionally produce new characteristics

3. Natural Selection

   • The resources living things need to survive are limited. Individuals must compete for these resources.
     • Some varieties of a species will have a feauture that gives them a better chance of survival
       • Those varieties are more likely to reproduce and pass on that gene
         • This means that a greater proportion of individuals in the next generation will have the characteristics that help organisms to survive
           • Over many generations, the species becomes better able to survive. the best features are naturally selected and the species becomes more adapted to its environment
             • The animal within the species that doesnt' have the beneficial feauture will die out as they can no longer compete

4. Selective Breeding

   • Deliberately choosing a feature they want to appear in the next generation and only breeding from plants or animals that have it
     • Selective breeding isn't done to aid survival, sometimes it can promote features that dont help survival
       • E.g. breed from cows that produce the most milk

5. Similarities

   • rely on the variation of individuals
     • ways of breeding animals
     • select ideal characteristics
       • the characteristics are passed onto offspring
   • rely on mutations
     • produce changes in characteristics
     • over time more individuals possess the characteristic

6. Differences

   • Selective breeding isn't natural
   • N.S takes longer
   • N.S selects traits to promote survival
   • S.B selects traits to help humans

7. Evolution

   • the combined effect of mutations, environmental changes, natural selection and isolation can produce new species in the process of evolution
     • mutations- create different new features
       • natural selection- beneficial features spread through each of the populations
         • environmental changes- If the climate changes in one are, but not another, then the organisms of the same species in the two areas will develop different adaptations to the different conditions that they live in
   • Evidence
     • evidence for evolution is provided by the fossil record and from analysis of similarities and differences in the DNA of organisms
       • The more closely related two species are, the more similar their DNA is.
     • Darwin’s theory of evolution by natural selection was the result of many observations and creative thought and why it is a better scientific explanation than Lamarck’s (e.g. fits with advances in understanding of genetics, no evidence or mechanism for inheritance of acquired characteristics).

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