Ecosystem

1. Ecosystem F.6 geography

2. Biosphere • The biosphere is made up of the living organisms of the earth , and their environments • Ecology - Ecology is the study of the relationship between organisms and their environment

4. The Ecosystem and the food chain • An ecosystem is a system describing the interactions between living organisms • 1. Components of an ecosystem Abiotic components - inorganic nutrients ,e.g water,carbon, gases and minerals - organic nutrients in leaves, fruit and meat

5. Biotic components • A) Producers are green plants which convert simple inorganic matter such as CO2 , water and minerals into organic compounds • B) Consumers are the different types of animals that eat producers • primary consumers: herbivores that feed on plants • Secondary consumers: carnivores • Tertiary and quarternary consumers • Omnivores • Detritivores

6. C) decomposer • like bacteria and fungi • They recycle nutrients by breaking down dead organisms into inorganic compounds again for absorption by green plants

7. Inputs and outputs of ecosystems • Ecosystems have inputs of matter and energy used to build the biological structures ,to reproduce, and to maintain necessary internal energy levels. • Matter and energy are also exported from an ecosystem • The inputs to, and outputs from , any ecosystem represent a link with other parts of the environment. Some of the outputs from one area become inputs into adjacent areas

8. Inputs • Solar radiation : supplies energy to the ecosystem • Water : supplied by rainfall, irrigation,etc • Nutrients : supplied by rock weathering or by man’s use of fertilizers • Animals : animals migrate into the areas • Plants and seeds : wind and streams may carry seed which germinate into plants, and man also introduce seeds or seedlings

9. Outputs • Water : lost through evapotranspiration, runoff of drainage • Animals: migrate away • Plants and seeds : carried away by winds or removed by man through harvest or lumbering • Gases and heat : escape back to the atmosphere

10. Food chains and food web • Autotrophs : make their own food • Heterotrophs : get their energy from the autotrophs. They are the consumers and decomposers • The food chain is a specific pathway of food transfer in which one kind, or one level of organisms feed upon another in a sequence of levels

12. The trophic levels( 營養層次） • The primary producers- plants and algae which use light energy to converts CO2 and H2O to carbohydrates which support life through the process of photosynthesis • Primary consumers • Secondary consumers • Tertiary consumers • Decomposer • Simple food chain rarely occur. Instead there are many interconnections of linear food chains into food webs

13. Photosynthesis and respiration • Photosynthesis is the production of carbohydrates, consisting of the elements carbon, hydrogen and oxygen. It is the process by which the autotrophs convert solar energy ,in the form of sunlight, to chemical energy • Water + carbon dioxide + sunlight energy > carbohydrates + oxygen H2O + CO2 + sunlight energy > CHOH + O2 The energy is released through the process of respiration

14. Respiration • The process of respiration is actually an oxidation process in which the carbohydrate breaks down to simpler molecules, carbon dioxide and water, releasing energy in the process • -COHO- + O2 > H2O + chemical energy + CO2

15. The cycle of photosynthesis and respiration • This involves both the primary producers and the decomposers • Water is drawn up into the body of a living plan • In the green leaves of the plants, photosynthesis takes place • Light energy is absorbed by the leaf cell • Carbon dioxide is brought in from the atmosphere • Oxygen is liberated and begins its atmospheric cycle

16. The plants tissue dies and falls to the ground • It is acted on by the decomposer • Through respiration, oxygen is taken out of the atmosphere or soil air and combined with the decomposing carbohydrates • Energy is now liberated • Both carbon dioxide and water enter the atmosphere as gases • The materials components- hydrogen, oxygen and carbon – are recycled within the system • Plant nutrients are recycle in the same way • The earth does not lose or gain matter and the materials never leave the system, they are just stored in other ways.

17. Net Primary Production • 1. Biomass • The net production by photosynthesis is measured in terms of biomass per unit surface area • Biomass is the dry weight of the organic matter and of all ecosystem

18. Net Primary production • This is the number of grams of dry organic matter produced annually from a square metre of surface • Equatorial forest – 2000gm/m²/year Mid- latitude grassland – 500gm/m²/year desert - 3 gm/m²/year

19. Net primary production and climate • Climatic factors such as light intensity, temperature and availability of water control the net production • The highest production is in TRF • There is low production in desert climates and at high latitudes • The Arctic has no production, because of the combination of short growing season and low temperature

20. The flow of energy in the biosphere 1. The energy flow system of a green plant • Solar short wave energy falling on a green leaf is partly reflected and partly absorbed through photosynthesis • The short wave energy is converted into chemical energy and stored in plant tissues • By respiration,chemical energy is converted to sensible heat • The stored sensible heat is evaporated away leaving the plant as latent heat,or lost to the atmosphere through longwave radiation or direct conduction

21. Energy flow along the food chain • Solar energy is absorbed, reflected and scattered in various way in the atmosphere • Less than half is received by plants and a small proportion is processed into organic compounds through photosynthesis • Respiration also reduces the gross primary production leaving the net primary production which is a small proportion of the energy absorbed by the green plants

22. The net primary production becomes an input for the next trophic level though not all energy from net primary production is usuable • Some is toxic or indigestible parts may not be consumed at all • Some is consumed and then excreted as faeces, and some are discharged as metabolic wastes such as urine

23. A small proportion of net primary production is held in the biomass ,after respiration – net secondary production • The same processes of energy transfer operate at the higher trophic levels, with energy being lost during each step • About 10-50% of the energy stored in organic matter at one level can be passed up the chain to the next level

24. The normal limit is four levels of consumers • The biomass also decreases with each upward step in the chain – the number of individuals of the consuming species is lower at each higher level

25. Implications of the decrease of energy up the food chain • As we go up the food chain, less and less energy is available in a unit area • Organism feeding at highest levels must find food over a wide area, to find enough to sustain themselves • A larger population can be supported by feeding at a lower level For example: far more energy could be make available if the food chain was shortened ( human eat more plants rather than cattle )

26. Man’s impact on energy flow in the ecosystem • Many man’s activities change the energy flow to maximize net primary productivity • The fossil fuel which run tractors, and farm machinery use energy inputs similar to light and chemical energy

27. The use of pesticides alters the energy flows in agricultural ecosystems by reducing the number of primary consumers • Bringing food to animals in feedlots save them from expending stored energy in looking for food, thus allowing them to rapidly gain weight

28. The Flow of matter/ materials in the Biosphere The three principal components of carbohydrates (-CHOH-): hydrogen (H), carbon (C ), and oxygen (O) ,are called macronutrient Six other macronutrients are : nitrogen (N) , Calcium (Ca), Potassium (K), magnesium (Mg), sulphur (S), and phosphorus (P)

29. The macronutrients are all required in substantial quantities for organic life to thrive • Matter in cycle includes water and a wide range of mineral substance • They are referred to as nutrients, and their transfers from one part of the ecosystem to another make up the nutrient or biogeochemical cycle

31. The Carbon cycle • All life is composed of carbon compounds • It exist in two forms : carbon dioxide and organic carbon ( carbohydrates , fat , protein ) • Carbon dioxide is a minor constituents of the atmosphere • A larger amounts of CO2 is dissolved in the water in the ocean • The greatest amount lies in storage as carbonate sediments

32. The process • Plants use solar energy,CO2 from the atmosphere,and water and minerals from the soil to change inorganic nutrients into organic compounds such as carbohydrates, proteins and fats • The fixation of carbon means carbon is fixed into solid carbohydrate

33. Through respiration, organic carbons is oxidized to become CO2, yielding energy. • Thus changes in state are form gas to solid and back to gas • Green plants not only provide food, but also give out oxygen, vital to the lives of animals and men