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B3 Life on Earth Bicester Community College Science Department B3 Key Questions How do different species depend on each other? How has life on Earth evolved? What is the importance of biodiversity? Bicester Community College Science Department How do different species depend on each other? species is a group of organisms that can breed together to produce fertile offspring. Adaptation of living organisms to their environment increases the species’ chance of survival by making it more likely that individuals will survive to reproduce. There is competition for resources between different species of animals or plants in the same habitat. Changes affecting one species in a food web may have an impact on other species that are part of the same food web. A Bicester Community College Science Department How do different species depend on each other? Bicester Community College Science Department How do different species depend on each other? A change in the environment may cause a species to become extinct, for example, if: the environmental conditions change beyond its ability to adapt a new species that is a competitor, predator or disease organism of that species is introduced another species (animal, plant or microorganism) in its food web becomes extinct Bicester Community College Science Department How do different species depend on each other? Nearly all organisms are ultimately dependent on energy from the Sun. Plants absorb a small percentage of the Sun’s energy for the process of photosynthesis. This absorbed energy is stored in the chemicals which make up the plants’ cells. Bicester Community College Science Department How do different species depend on each other? Energy is transferred between organisms in an ecosystem: when organisms are eaten when dead organisms and waste materials are fed on by decay organisms (decomposers and detritivores) Energy is lost from a food chain at each stage via heat, waste products and uneaten parts, limiting the length of food chains. Bicester Community College Science Department How do different species depend on each other? Bicester Community College Science Department How do different species depend on each other? Bicester Community College Science Department How has life on Earth evolved? Life on Earth began approximately 3500 million years ago. Life on Earth (including species that are now extinct) evolved from very simple living things. Bicester Community College Science Department How has life on Earth evolved? is variation between individuals of the same species. Some of this variation is genetic so can be passed on to offspring. Genetic variation is the result of changes that occur in genes (mutations) and may occasionally produce new characteristics. There Bicester Community College Science Department How has life on Earth evolved? Variation Inheritance Selection Time Adaptation Bicester Community College Science Department How has life on Earth evolved? New species can be produced by the combined effect of: mutations environmental change natural selection isolation Bicester Community College Science Department How has life on Earth evolved? Evidence for evolution is provided by the fossil record and from analysis of similarities and differences in the DNA of organisms. Bicester Community College Science Department What is the importance of biodiversity? Organisms are classified into groups according to similarities and differences in characteristics including: Classification of living and fossil organisms can help to: physical features DNA make sense of the diversity of organisms on Earth show the evolutionary relationships between organisms Organisms are classified at different levels. 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) Bicester Community College Science Department What is the importance of biodiversity? Biodiversity including: refers to the variety of life on Earth the number of different species the range of different types of organisms, e.g. plants, animals and microorganisms the genetic variation within species Bicester Community College Science Department What is the importance of biodiversity? Biodiversity is important for the future development of food crops and medicines Sustainability means meeting the needs of people today without damaging the Earth for future generations Maintaining biodiversity to ensure the conservation of different species is one of the keys to sustainability. Large-scale monoculture crop production is not sustainable because it does not maintain biodiversity. Sustainability can be improved, for example by considering the materials used, energy used and pollution created. Bicester Community College Science Department Common B3 mistakes… make sure you don’t do these! Students often: have difficulty in explaining how adaptation develops through evolution (e.g. in the beaks of 'Darwin's finches') have difficulty in explaining why crops might be genetically modified may not realise that for animal populations to rise or fall significantly there should be a change in a contributing factor may not recognise the concept of a common ancestor or divergence may report incorrectly that humans use natural selection to breed domestic animals Bicester Community College Science Department Links from B3 to other topics More about ecosystems in B7.4 Further biology Sustainable development in C2 Material choices Bicester Community College Science Department