Bioknowledgy
questioning, investigating and understanding
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  • IB Biology
    • Syllabus
    • General Resources
    • Practical scheme of work >
      • Practical activities (Labs)
      • Individual investigation
      • IB Write
      • Group 4 project
  • Core
    • 1. Cell biology >
      • 1.1 Introduction to cells
      • 1.2 Ultrastructure of cells
      • 1.3 Membrane structure
      • 1.4 Membrane transport
      • 1.5 The origin of cells
      • 1.6 Cell division
    • 2. Molecular biology >
      • 2.1 Molecules to metabolism
      • 2.2 Water
      • 2.3 Carbohydrates and lipids
      • 2.4 Proteins
      • 2.5 Enzymes
      • 2.6 Structure of DNA and RNA
      • 2.7 DNA replication, transcription and translation
      • 2.8 Cell respiration
      • 2.9 Photosynthesis
    • 3. Genetics >
      • 3.1 Genes
      • 3.2 Chromosomes
      • 3.3 Meiosis
      • 3.4 Inheritance
      • 3.5 Genetic modification and biotechnology
    • 4. Ecology >
      • 4.1 Species, communities and ecosystems
      • 4.2 Energy flow
      • 4.3 Carbon cycling
      • 4.4 Climate change
    • 5. Evolution and biodiversity >
      • 5.1 Evidence for evolution
      • 5.2 Natural selection
      • 5.3 Classification of biodiversity
      • 5.4 Cladistics
    • 6. Human physiology >
      • 6.1 Digestion and absorption
      • 6.2 The blood system
      • 6.3 Defence against infectious disease
      • 6.4 Gas exchange
      • 6.5 Neurons and synapses
      • 6.6 Hormones, homeostasis and reproduction
  • Additional higher level (AHL)
    • 7. Nucleic acids >
      • 7.1 DNA structure and replication
      • 7.2 Transcription and gene expression
      • 7.3 Translation
    • 8. Metabolism, cell respiration and photosynthesis >
      • 8.1 Metabolism
      • 8.2 Cell respiration
      • 8.3 Photosynthesis
    • 9. Plant biology >
      • 9.1 Transport in the xylem of plants
      • 9.2 Transport in the phloem of plants
      • 9.3 Growth in plants
      • 9.4 Reproduction in plants
    • 10. Genetics and evolution >
      • 10.1 Meiosis
      • 10.2 Inheritance
      • 10.3 Gene pools and speciation
    • 11. Animal physiology >
      • 11.1 Antibody production and vaccination
      • 11.2 Movement
      • 11.3 The kidney and osmoregulation
      • 11.4 Sexual reproduction
  • Options
    • A. Neurobiology and behaviour >
      • A.1 Neural development
      • A.2 The human brain
      • A.3 Perception of stimuli
      • A.4 Innate and learned behaviour (AHL)
      • A.5 Neuropharmacology (AHL)
      • A.6 Ethology (AHL)
    • B. Biotechnology and bioinformatics
    • C. Ecology and conservation >
      • C.1 Species and communities
      • C.2 Communities and ecosystems
      • C.3 Impacts of humans on ecosystems
      • C.4 Conservation of biodiversity
      • C.5 Population ecology (AHL)
      • C.6 Nitrogen and phosphorus cycles (AHL)
    • D. Human physiology
  • BISV Revision
  • Giving back - BioKQQAnswers

Essential idea: Ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat.

The image above shows an eruption on the surface of the sun. Without a constant stream of solar radiation much of the life on Earth would not be possible. The sun's energy is the source of energy in the vast majority of the Earth's ecosystems.

Understandings, applications and skills

4.2.U1 Most ecosystems rely on a supply of energy from sunlight.
4.2.U2 Light energy is converted to chemical energy in carbon compounds by photosynthesis.
4.2.U3 Chemical energy in carbon compounds flows through food chains by means of feeding. [Pyramids of number and biomass are not required. Students should be clear that biomass in terrestrial ecosystems diminishes with energy along food chains due to loss of carbon dioxide, water and other waste products, such as urea.]
4.2.U4 Energy released from carbon compounds by respiration is used in living organisms and converted to heat.
4.2.U5 Living organisms cannot convert heat to other forms of energy.
4.2.U6 Heat is lost from ecosystems.
4.2.U7 Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels. [The distinction between energy flow in ecosystems and cycling of inorganic nutrients should be stressed. Students should understand that there is a continuous but variable supply of energy in the form of sunlight but that the supply of nutrients in an ecosystem is finite and limited.]
4.2.S1 Quantitative representations of energy flow using pyramids of energy. [Pyramids of energy should be drawn to scale and should be stepped, not triangular. The terms producer, first consumer and second consumer and so on should be used, rather than first trophic level, second trophic level and so on.]
[Text in square brackets indicates guidance notes]

Presentation and notes

The presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the development of student notes to aid revision.


Vocabulary

Correct use of terminology is a key skill in Biology. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.
Use the Cornell style template to collate your own notes for Topic 4.1 Species, communities and ecosystems.


Quick quiz

Use the BioK Quick Quiz on 4.2 Energy Flow (as directed) to check your understanding of the topic.

Nature of science

Use theories to explain natural phenomena—the concept of energy flow explains the limited length of food chains. (2.2)

International-mindedness:

The energetics of food chains is a factor in the efficiency of food production for the alleviation of world hunger.
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