ECOSYSTEMS & ENERGY FLOW May 2014

2 Ecosystem  A community and its physical environment  Made up of two essential components:  Abiotic factors  Biotic factors

3 Abiotic factors  non-living components of an ecosystem  elements which may be found in the environment  May be:  Physical  Chemical

4 Physical factors  Sunlight and shade  Temperature and wind  Amount of precipitation  Altitude and latitude  Nature of soil

5 Chemical factors  Salinity of water  Level of dissolved O 2 and other gases  Level of plant nutrients  pH of soil and water  Level of natural or artificial toxic substances

6 Biotic factors  The organisms in an ecosystem are either:  Autotrophs  photoautotrophic  chemoautotrophic  Heterotrophs  include humans  animals and  microorganisms.

7 Autotrophs  Photoautotrophs – has chlorophyll and carry on photosynthesis.  Chemoautotrophs – bacteria that obtain energy from the oxidation of inorganic compounds such as ammonia, nitrites and sulfides.

8 Heterotrophs  need a source of pre-formed nutrients  consume tissues of other organisms.  consumers are classified according to the type of food they eat.

9 Types of Consumers  Herbivores feed directly on green plants.  Carnivores eat other animals.  Omnivores feed on both plants and animals.

10 Types of Consumers  Decomposers fungi and bacteria extract energy from dead matter, including waste return nutrients back to the soil.  Scavengers feed on dead matter.

How do organisms get food?  Producers (use photosynthesis)  Consumers (use cellular respiration) 11

12 Food Chain  illustrates how energy and nutrients move from one organism to another  shows transfer of energy from one trophic level to another

13 Food Chain

14 Trophic levels  A trophic level includes a group of organisms that obtain food in a similar manner. Producers Primary consumers Secondary consumers Tertiary consumers Quaternary consumers

16 Food Webs: Who Eats Whom?

17 Food Web  A complex network of interconnected food chains  The feeding relationship that actually exists in nature  May be:  Grazing food web  Detrital food web

19 Energy Flow  Ecosystems are dependent upon solar energy flow and finite pools of nutrients.  The primary source of energy for ecosystems is sunlight.  All energy content of organic matter is eventually lost to the environment as heat.

20 Laws of Thermodynamics  Energy can neither be created nor destroyed, but can be transformed into different forms.  When energy is transformed from one form to another, there is always some loss of energy from the system, usually as low grade heat.

21 10% Law of Energy Transfer  only 10% of energy at a particular trophic level is incorporated into the next trophic level.  rapid loss of energy explains why a food chain rarely has five links.

23 Energy Flow

24 Ecological Pyramids  Graphic representations of the relative energy amounts at each trophic level.  3 Types of Pyramids 1. Pyramid of Energy 2. Pyramid of Biomass 3. Pyramid of Numbers

25 Pyramid of Energy  Energy content of each trophic level  Unit of energy = Kilocalories/meter 2 /year  Pyramid has large base and gets significantly smaller at each level.  Organisms use energy for work and respiration, so less energy is available to each successive trophic level.

26 Pyramid of Energy  energy at each trophic level expressed in kcal/m2/yr.

27 Pyramid of Biomass  Biomass is a quantitative estimate of the total mass (amount) of living material…or …the amount of fixed energy at a given time.  Measuring biomass: total volume, dry weight, or live weight  A 90% reduction occurs between each trophic level

28 Pyramid of Biomass  Biomass also diminishes with the distance along the food chain from the autotrophs which make the organic molecules in the first place.

29 Pyramid of Numbers  Illustrates number of organisms at each trophic level  more individuals at the lower trophic levels.  BUT some number pyramids can be inverted.

30 Pyramid of Numbers  Small animals are more numerous than larger ones.  If the size of the individuals at a given trophic level is small, their numbers can be large and vice versa.

31 Identify the food chains and write the trophic level for each organism in this food web.

Food Web Activity: