F215:03:03 Manipulating energy transfer Flashcards Preview

F215:03 Ecosystems and sustainbility > F215:03:03 Manipulating energy transfer > Flashcards

Flashcards in F215:03:03 Manipulating energy transfer Deck (43):

Define primary productivity

the total amount of energy fixed by photosynthesis
The net flux of carbon from the atmosphere to plants per unit time. It is a rate and can be measured in terms of energy per unit of time.


Give an example of a measurement that can measure primary productivity



What is net primary productivity?

the rate at which carbohydrate accumulates in the tissue of plants of an ecosystem and is measures in dry organic mass, such as kg ha-1yr-1
(rate of production of new biomass available for consumption of heterotrophs)


How is net primary productivity calculated?

Net primary productivity = primary productivity - respiratory heat loss


What % of sunlight energy that reaches Earth is used for photosynthesis

Less than 1%


What happens to all the sunlight that reaches earth that is not being used for photosynthesis?

It is reflected by clouds and the Earths surface
used to heat the Earths atmosphere
To evaporate water
Or is of the wrong wavelength so is not captured by the chlorophyll


What is the energy captured by leaves for photosynthesis known as?

primary productivity


What does R stand for?

respiratory heat


When scientisist measures NPP 'in the field' what % is the actual levels for crop plants?



How can humans increase the NPP?

By manipulating environmental factors
By making energy conversion more efficient
By reducing energy loss
Increasing crop yields


How do light levels limit NPP?

As light level limits the rate of photosynthesis


How can light levels be increased to raise the NPP?

Some are planted earlier so the growing season is longer
Some are grown under light banks


How is a lack of water being prevented from reducing NPP?

Crops can be irrigated
Drought-resistance strains have been bred


Give 3 examples of drought-resistant strains being developed to increase the NPP of plants in places that lack water

barley in north africa
wheat in Australia
sugar beet in UK


How can temperature limit NPP?

As it limits the speed of chemical reactions in a plant


How have humans prevented temperature from limiting NPP as much?

By using green houses, which provide warmer temperatures for growing plants and therefore increase NPP
And planting crops early to provide a longer growing season helps to avoid the impact of temp on final yield


Why are crops planted earlier

So the growing season is longer
Allows more light to be harvested by the plants
helps avoid the impact of temp on the final yield


How can a lack of nutrients limit NPP?

As a lack of nutrients slows the rate of photosynthesis and growth


How do farmers prevent there becoming a lack of nutrients which would reduce the NPP?

Crop rotations can help
Particularly planting nitrogen fixing plants which replenishes nitrates in the soil
many crops have been bred to be more responsive high levels of fertiliser


What is crop rotation?

Growing a different crop in each field on a rotational cycle


Give two examples of nitrogen fixing plants



How can pests reduce the NPP of a crop?

as they eat the plantrs and reduce the amount of biomass and stored energy from the food chain and lower the yield


How have humans prevented pests from reducing the NPP of a crop?

By spraying the crops with pesticides
or some plants have been bred to be pest resistant
Or are genetically modified with a bacterial gene (Bt gene)


What does Bt stand for?

Bacillus thuringiensis


Give an example of when plants have been made to be pest resistant using Bt

In Bt-cotton in the USA, its resistant to bollworm and in maize against corn-borers


How do fungal diseases reduce NPP?

They cause root rot, damage to xylem vessels, damage foilage tubes ot damage flowers/fruit


How does root rot reduce NPP?

By reducing water absorption


How does damage to xylem vessels reduce NPP?

by interfering with water absorption


How does the damage of foilage roots reduce NPP?

interfering with the translocation of sugars


How does damage of flowers/fruits reduce the NPP?

interfers with reproduction


How do farmers prevent fungi from reducing NPP?

farmers spray crops with fungicides
Some have been bred to be resistant to fungal infections
Or genetically modified


Give an example of a plant that has been bred to be resistant to fungal infections

Rhizomania resistance in sugar beet


Give an example of how plants have been genetically modified to be resistant to fungal infections

potatoes have been genetically modified to be resistant to potato blight


How can weeds reduce NPP in crops?

They compete with plants for light, water, and nutrients


How do farmers prevent crops from having to compete with weeds for nutrients, water and light?

They spray herbicides on plants to kill the weeds


How efficient is the transfer of energy from producers to consumers?

very inefficient


Why dont primary consumers make full use of a plants biomass?

Some plants die
Consumers dont eat every part of the plant
they dont digest everything they eat, a lot is egested into their faeces
Even what it does digest, only a small amount is stored to use for growth, most is used to keep the animal alive


How do humans manipulate energy transfer from producer to consumer?

- Young animals invest a larger proportion of growth than an adult does, so they are killed earlier to reduce waste
- In the past, steroids have been used, but was outlawed by the EU years ago
- Selective breeding has been used to breed breeds with faster growth rates, increased egg/milk production
- Animals can be treated with antibiotics to reduce unnecessary loss of energy to parasites/pathogens
- mammals and birds waste alot of energy moving around to look for food, and keeping their body temperature stable.


As energy transfer is so inefficient, why don't we just eat the grain directly instead of feeding animals first?

As there are places where grain cannot be grown but animals can exist


Give an example of a place where animals can be grown but grain cant

Sheep can be bred on the mountainsides,
But they are usually infertile so cant be used to grow grain


Why is the balance between animal welfare and efficient food production so controversial?

As many people have serious concerns about modern farming practices.


Suggest which animals would be most efficient to farm:
endotherms like birds and mammals (with a constant body temp)
Ectotherms like worms, fish and reptiles (whose body term varies)

Ectotherms would be the most efficient, as they would not use energy to maintain body temp as endotherms need to.


Rainforests are an important source of biodiversity. Some rainforests are being cleared to grow crops for animal feed. Because of this some people have decided to adopt a vegetarian diet. Explain their reasoning in terms of energy loss from the food chain.

Across the world alot of land is allocated to meat, if this could be more efficiently used for wheat production (would be a shorter food chain, so more efficient, so less land would be needed)
If fewer people ate meat, then more land would be used for arable crop production and less rainforest would need to be felled.