We are working with Cambridge International towards endorsement of this title. AS & A Level Marine Science COURSEBOOK Marine Science for Cambridge International AS & A Level COURSEBOOK Matthew Parkin, Melissa Lorenz, Claire Brown & Jules Robson Completely Cambridge Cambridge University Press works with Cambridge Assessment International Education and experienced authors to produce high-quality endorsed textbooks and digital resources that support Cambridge Teachers and encourage Cambridge Learners worldwide. To nd out more about Cambridge University Press visit cambridge.org/cambridge-international DRAFT Second edition Cambridge Elevate edition Original material © Cambridge University Press 2019. This material is not final and is subject to further changes prior to publication. We are working with Cambridge International towards endorsement of this title. Contents Contents How to use this series 00 Practical skills 1 Experimental planning including making How to use this book 00 estimates, predictions and hypotheses 00 Introduction 00 2 Presentation of data and observations 00 3 Evaluation of procedures and data 00 Introduction to command words 00 4 Analysis of data and conclusions 00 1 Water 6 Physiology of marine organisms 1.1 Particle theory and bonding 00 6.1 General cell structure 00 1.2 Solubility in water 00 6.2 Movement of substances 00 1.3 Density and pressure 00 6.3 Gas exchange 00 2 Earth processes 6.4 Osmoregulation 00 2.1 Tectonic processes 00 7 Energy 2.2 Weathering, erosion and sedimentation 00 7.1 Photosynthesis 00 2.3 Tides and ocean currents 00 7.2 Chemosynthesis 00 3 Interactions in marine ecosystems 7.3 Respiration 00 3.1 Interactions 00 8 Fisheries for the future 3.2 Feeding relationships 00 8.1 Life cycles 00 3.3 Nutrient cycles 00 8.2 Sustainable fisheries 00 4 Classification and biodiversity 8.3 Marine aquaculture 00 4.1 The classification of marine organisms 00 9 Human impacts on marine ecosystems 4.2 Key groups of marine organisms 00 9.1 Ecological impacts of human activities 00 4.3 Biodiversity 00 9.2 Global warming and its impact 00 4.4 Populations and sampling techniques 00 9.3 Ocean acidification 00 5 Examples of marine ecosystems 9.4 Conservation of marine ecosystems 00 5.1 The open ocean 00 Glossary 00 5.2 The tropical coral reef 00 Index 00 5.3 The rocky shoreDRAFT 00 5.4 The sandy shore 00 Acknowledgements 00 Original material © Cambridge University Press 2019. This material is not final and is subject to further changes prior to publication. We are working with Cambridge International towards endorsement of this title. Chapter 3 Interactions in marine ecosystems LEARNING OUTCOMES In this chapter you will learn how to: • describe the three main types of symbiotic relationship and describe examples of each one • represent feeding relationships as food chains or food webs and be able to describe the organisms in these relationships in terms of their trophic level • explain how photosynthesisDRAFT provides energy to the food chain and summarise the process as a word equation • give the word equation for respiration • define productivity and explain how high productivity can affect food chains • explain why energy is lost at each stage of the food chain Original material © Cambridge University Press 2019. This material is not final and is subject to further changes prior to publication. We are working with Cambridge International towards endorsement of this title. CAMBRIDGE INTERNATIONAL AS & A LEVEL MARINE SCIENCE: COURSEBOOK CONTINUED • draw pyramids of number, energy and biomass and be able to explain and interpret their shapes • explain what a nutrient is and be able to give the biological roles of nitrogen, carbon, magnesium, calcium and phosphorus • draw simple diagrams to show how carbohydrates, proteins and lipids are made up from smaller molecules • explain how nutrients in the ocean are depleted and replenished • describe the different stages in the carbon cycle including combustion, photosynthesis, decomposition, fossil fuels and the formation and weathering of rocks. BEFORE YOU START • In small groups, think of as many ways as you can in which organisms of different species can interact. Divide your list into positive and negative interactions. • In pairs, discuss what you already know about food chains. If you can, draw and label a simple food chain. • Write down any examples of nutrients you have heard of and the reasons you think they are needed by living organisms. THE IMPORTANCE OF PHYTOPLANKTON Around three billion people rely on marine the oxygen you breathe will have come from their ecosystems for their food. These people obtain the photosynthesis. majority of the protein in their diet from farmed or wild caught fish and other seafood. What they NASA, the United States’ civilian space programme, may not realise is that, ultimately, much of the monitors the levels of phytoplankton in the oceans energy in their food has come from tiny organisms using satellite imagery, comparing the colour called phytoplankton. This word comes from the of the water to the colour of chlorophyll and Greek meaning ‘drifting plants’ Phytoplankton other pigments. NASA has found that, overall, are tiny, microscopic organisms which float in the phytoplankton populations have declined over the upper sunlit layers of the water. Like land plants, last decade. This may be because the surface of they contain chlorophyll which enables them to the ocean is increasing in temperature. This in turn photosynthesise. They carry out more than half decreases the mixing between the nutrient-rich of all the photosynthesis on Earth, producing up to lower layers of water and the upper sunlit layers. 160 billion tonnes of carbohydrates every year. Fewer nutrients means less growth and reproduction of phytoplankton. In contrast, marine dead zones The ability of the phytoplankton to capture the are formed where excess fertilisers enter the water. energy in sunlight and to fix it into carbohydrates In these areas productivity reaches such a peak is essential to life in theDRAFT oceans. Many of the that the ecosystem becomes unbalanced. The consumers must gain their energy from either phytoplankton population initially increases very eating the phytoplankton directly, or from eating rapidly in a phenomenon known as an algal bloom. other animals who have eaten the phytoplankton. As the cells die and are decomposed by bacteria the Even if you do not eat seafood you are benefitting levels of oxygen fall. Eventually the oxygen levels from these tiny organisms, as more than half of become so low that little life can remain. 2 Original material © Cambridge University Press 2019. This material is not final and is subject to further changes prior to publication. We are working with Cambridge International towards endorsement of this title. 3 Interactions in marine ecosystems CONTINUED Questions done about this problem and the impacts on 1 Marine dead zones are often formed when land and ocean ecosystems. agricultural fertilisers enter the water. This 2 Think about why an organisation such as NASA reduces the population of fish available to catch might need to monitor the phytoplankton in the and use as food. However, if we do not use the ocean. Discuss, in groups, the reasons that this fertilisers there will be a reduction in the yield might be important and whether you think it is a of food crops. Discuss, in pairs, what should be good use of resources. to each other. The word comes from a Greek term which 3.1 Interactions means ‘living together’. The smaller organism is the symbiont and the larger organism is the host. There are Ecological interactions describe how a pair of organisms several different types of symbiosis including: living together in a community can affect one another. Some of these interactions are mutualistic and have • parasitism – where the symbiont benefits but a positive effect on both organisms. Others such as the host is damaged; for example, copepods and predation and parasitism are harmful to one of the marine fish species involved. Competition is harmful to both • commensalism – where the symbiont benefits but organisms as they are both trying to use the same the host remains unaffected; for example, manta resources. However, all of these relationships are vital to rays and remora fish the ecosystem as they allow the transfer of energy from one organism to the next. • mutualism – where both organisms benefit from the relationship, for example, boxer crabs and Symbiosis is a relationship between two or more anemones. organisms of different species which live physically close KEY WORDS phytoplankton: microscopic photosynthetic mutualism (mutualistic): a relationship between organisms that live in the upper, sunlit layers of water two different organisms where both organisms benefit chlorophyll: a pigment found in plants and algae that is used to absorb sunlight for photosynthesis predation: a relationship between two organisms where a predator hunts, kills and eats a prey animal photosynthesis (photosynthetic, photosynthesise): the process of using light energy to synthesise parasitism: a relationship between two organisms glucose from carbon dioxide and water where the parasite obtains benefit at the expense of the host carbohydrate: organic compounds occurring in living tissues that contain carbon, hydrogen and competition: a relationship between two organisms oxygen, for example, starch, cellulose and sugars; where both species are negatively affected as they carbohydrates can be broken down in the process are trying to use the same resources of respiration to release energy symbiosis: a relationship between two or more consumer: an animal which feeds on other organisms of different species which live physically organisms to gain energyDRAFT from food close to each other algal bloom: a rapid increase in a population of commensalism: a relationship between two algae organisms where one organism benefits and the other is neither harmed nor benefitted community: all the different populations interacting in one habitat at the same time 3 Original material © Cambridge University Press 2019.