4º ESO. Unit 7: Matter and energy in ecosystems.

Study plan: 

Week 1:

Day 1 

Explanation of pages 118 and 119 of the book. 

A trophic level consist of all the organisms in an ecosystem which feed in the same way. These are:

• Producers.
• Consumers.
• Decomposers. 

Whatch these videos about trophic levels and their relationships in an ecosystem: trophic chains and trophic networks.  

• Later on watching the videos above do the activities of page 119 in your notebook.

Day 2 

Pages 120 and 121 of the book.

Transfer of matter and energy in ecosystems.

Main ideas:

MATTER flows in an ecosystem in a closed circuit.

1º) Plants and other photosynthetic organisms capture the sun's energy and use it to synthesize energy-rich molecules (mainly sugars). These organisms are called PRODUCERS.

2º) The organisms that consume the producers (called CONSUMERS) derive energy and materials from breaking down the producers’ molecules, use them to synthesize their own structures and then may be consumed by other organisms. 

3º) DECOMPOSERS (organisms that break down dead producers and consumers and organic waste) obtain the energy they need to live from the consumption of the dead and waste-matter. So decomposers transform organic remains into inorganic products that are used by producers.

ENERGY flows in an ecosystem in a open circuit. 

Unlike matter, as energy flows through an ecosystem in one direction, from photosynthetic organisms to herbivores to omnivores and carnivores and decomposers, less and less energy becomes available to support life. This loss of useable energy occurs because each energy transfer results in the dissipation of some energy into the environment as heat. Continual input of energy from sunlight is necessary to keep ecosystems organized and functioning. 

• After studing the transfer of matter and energy in an ecosystems do the activities of page 121 (1, 2 and 3). 

Day 3

Page 122 and 123. 

TROPHIC PARAMETERS.

Main ideas: 

They are used for understanding the food relationships between the organisms in an ecosystem. 

Biomass:

It is the amount of organic matter in each trophic level. It is expressed as mass of living matter per unit of surface or per unit of volume (if we are considering an aquatic ecosystem). We can distinguish between:

• Primary biomass.
• Secondary biomass.
• Residual biomass.

Production:

It is the fixation of energy (measured in biomass) during a period of time. 

• Primary production: it is the fixation of energy (measured in biomass) by autotrophs in an ecosystem during a period of time.

              - Gross primary production: total amount of energy fixed by autothrops.             

          - Net primary production: amount of energy left over after autotrophs have met their metabolic needs.

•  Secondary production: production of biomass by heterotrophic consumers during a period of time.

             - Gross secondary production: is the percentaje of the total amount of food consumed that is assimilated by a trophic level of consumers.

            - Net secondary production: is the energy that remains available for the following trophic level.

• Activities: working with pictures page 122 and working with pictures page 123 and activity 1 of page 123.
  

Week 2: 

Day 4

Page 124 and 125.

TROPHIC PYRAMIDS.

They are graphs that represent the trophic relationships between the organisms of the community in an ecosystem. Types:

• Pyramid of energy: in each level is represented the amount of energy that is available to that trophic level. With each step up, there is an energy oss of 90%.
• Pyramid of biomass: each level represents the amount of biomass (organic matter). 
• Pyramid of numbers: in each level is represented the number of organisms. 

 

• Now do the activities 1, 2 and 3. 

Day 5

Page 126 and 127.

BIOGEOCHEMICAL CYCLES.

They corresponds to the circulation of chemical elements through the ecosystem. There are two main types:

• Gaseous nutrient cycles, whose main reserve is the atmosphere.
• Sedimentary nutrient cycles, whose main reserve is the lithosphere (geosphere). 

In this video you will find two examples of biogeochemical cycles, the carbon and the nitrogen cycle. We are going to study the carbon one. 

 

Acitivities 1, 2, 3 and 4 of page 126.

Day 6: END OF THE UNIT.

Page 130. Review.

Activities 1, 3, 4 and 5.  

Week 3: 

Review and study the unit.  

Thursday 16th of April at 12:00 h.  Exam of the unit 6 and 7. 

For doing the exam you have to enter in your classroom (7dwdlyj), there, I will upload the exam at 12:00h, you will have to complete and send it to me before 13:45 h.  

We are going to study the next unit via classroom.