5. Energy And Ecosystems Flashcards Preview

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Flashcards in 5. Energy And Ecosystems Deck (50)
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What are producers?

Photosynthetic organisms which manufacture organic substances using light energy, water and carbon dioxide


What are consumers?

Organisms that derive their energy from eating plants and other organisms rather than through photosynthesis


What is a decomposer?

Organisms such as detritivores that break down complex molecules into simple components


What is each stage in a food chain called?

Trophic level


What do the arrows on food chains represent?

The flow of energy


What is the source of energy in all ecosystems?

The sun


How much of the sun's energy available to them do plants convert into organic matter by photosynthesis?

Why is so little converted into organic matter?

Between one percent and three percent.

-Over 90% of the sun's energy is reflected back into space by clouds and dust or absorbed by the atmosphere
-Not all wavelengths of light can be absorbed for use in photosynthesis
-Light may not fall on a chlorophyll molecule
-There may be factors limiting the rate of photosynthesis such as carbon dioxide concentration


What is the total amount of energy plants in a community convert to organic matter called?

Gross production


What is the rate at which plants store energy called?

Net production


What is the equation for net production?

Net production = gross production - respiratory losses


Why is there such a low percentage of energy transferred at each stage?

-Not all of the organism is eaten
-Not all of the organism can be digested (therefore lost in faeces)
-Energy lost in excretory materials such as urine
-Energy losses as heat from respiration


How is the efficiency of energy transfer calculated? (equation)

Energy transfer = (energy available after the transfer)/ (energy available before the transfer) x100


What are the drawbacks of using a pyramid of numbers to describe a food chain?

-No account is taken of size (eg oak tree is massive but still only counts as 1)
-Number of individuals can be so great that it is hard to represent them on the same scale as other organisms


Why can pyramids of biomass be unreliable if done incorrectly?

-The fresh mass can be easily calculated however in different organisms there are different levels of water so the mass will vary
-Therefore you must use the dry mass by heating in an oven
>However organisms must be killed so therefore only a few measurements can be taken which means the results may not be representative of the population.

-Only valid at the time of sampling- doesn't take into account seasonal changes


What is the unit for biomass in the context of pyramids of biomass?

or gm^-3 when a volume is being sampled


What is the most accurate representation of flow through an ecosystem?

Pyramids of energy (measuring energy stored in organisms)


What is the unit used for energy flow in the context of pyramids of energy?



Why are the results of a pyramid of energy much more reliable than a pyramid of biomass?

Organisms with the same dry mass may contain different amounts of stored energy eg fat stores more energy than carbohydrate, even though their biomasses are equal


What is the purpose of an agricultural ecosystem?

Ensure as much of the available energy from the sun is transferred to humans (increasing the productivity of the human food chain)


What factors is net productivity affected by?

-Efficiency of the crop carrying out photosynthesis
-Area of ground covered by the leaves of the crop


In which ways does an agricultural ecosystem differ to a natural ecosystem?

-There is additional energy input into an agricultural ecosystem (eg energy from food (labour) and fossil fuels (machinery and transport))
-Higher productivity
-Less species diversity
-Less genetic diversity within a species
-Populations are controlled both by natural means and by use of pesticides and cultivation
-Prevented from reaching a climax community
-Natural recycling limited and supplemented by the addition of artificial fertilisers


What are the qualities of a good pesticide?

-Cost-effective because development costs are high an pesticides only remain efficient for a limited amount of time as pests become resistant
-Does not accumulate (eg bioaccumulation)
-Biodegradable- break down into harmless substances in the soil
-Specific- only toxic to the pest that it is trying to control- harmless to humans and other organsisms


What is the aim of a biological control?

To reduce the numbers of the pest below the economic injury level but NOT eradicate the pest


What are the advantages of using biological control rather than chemical pest control?

Biological control
-Very specific
-Once introduced the control organism reproduces itself
-Pests to not become resistant


What are the disadvantages of chemical pest control?

-May affect species other than the target species
-Must be reapplied regularly (expensive)
-Pests develop genetic resistance and so new pesticides need to be developed.


What are the disadvantages of using biological pest control?

-The control species may become a pest itself
-Do not usually act very quickly- lag between the time of application and the reduction of the pest.


What is an integrated pest control?

Using all forms/ a combination of pest controls


How can maximum yield of product be achieved through intensive farming?

-Limiting movement (keeping in confined spaces)
-Keeping environment warm to reduce heat loss
-Optimum food quantity and food type so there is as little waste as possible
-Predators excluded so no loss to other organisms in the food web
This all limits the energy losses through respiration so there is more energy available for growth/ milk production etc...


Describe ways other than intensive farming that can increase the energy conversion rate.

-Using hormones to increase growth rate
-Selective breeding to produce varieties that are more efficient at converting the food they eat into body mass.


(5 marks)
The Amazonian forest today contains a very high diversity of bird species.

-Over the last 2 000 000 years, long periods of dry climate caused this forest to
separate into a number of smaller forests.
-Different plant communities developed in each of these smaller forests.
-Each time the climate became wetter again, the smaller forests grew in size and
merged to reform the Amazonian forest.

Use the information provided to explain how a very high diversity of bird species has
developed in the Amazonian forest.

1. No interbreeding / gene pools are
separate / geographic(al)
2. Mutation;
3. Different selection pressures /
different foods/niches/habitats;
4. Adapted organisms survive and
breed / differential reproductive
5. Change/increase in allele