Biology A Level Unit 4: Energy And Ecosystems

Front 1

How is energy transferred?

Back 1

•Through consumption of organisms by other organisms.
•Energy locked up in parts that cannot be eaten (bones, faeces etc.) get recycled back into the ecosystem by decomposers.

Front 2

Why doesn't all energy get transferred to the next trophic level?

Back 2

Around 90% is lost in various ways.

•Around 60% of the energy isn't taken in, in the first place.
-plants can't use all light energy.
-bones, faeces, roots etc. aren't eaten by organisms.
-some parts of the food is indigestible and pass through organisms.

•40% absorbed energy called "gross productivity". This isn't all available to the next trophic level either.
-30% of total energy lost to the environment, maintains body heat, respiratory loss.
-10% of total energy becomes biomass, stored or used for growth, net productivity.

Net productivity = gross productivity / respiratory loss

Front 3

What is a natural ecosystem?

Back 3

An ecosystem that hasn't been changed by human activity.

Front 4

What is the energy input of an ecosystem?

Back 4

The amount of energy captured by the producers in an eco system.

Front 5

What is intensive farming?

Back 5

Involves changing an ecosystem by controlling the biotic and abiotic conditions to make it more favourable for crops and livestock.
Crops and livestock can have greater net productivity.

Front 6

How does intensive farming increase productivity?

Back 6

•Increase efficiency of energy conversion.
•Remove limiting growth factors.
•Increase energy input.

Front 7

How does intensive farming increase productivity?

Back 7

•Increase efficiency of energy conversion.
•Remove limiting growth factors.
•Increase energy input.

Front 8

What are pests?

Back 8

Pests are organisms that reduce productivity of crops. By reducing the amount of energy available for growth.

Front 9

What chemical pesticides are used?

Back 9

Herbicides - kill weeds that compete for energy.
Fungicides - kill fungal infections that damage crops, less energy used for fighting infection.
Insecticides - kill pests that eat and damage crops

Front 10

What are environmental and economic issues with chemical pesticides?

Back 10

Environmental:
•May Directly kill/damage non pest species, (butterflies etc.)
•Indirectly kill/damage non pest species. Secondary consumers eating poisoned primary consumers.

Economic:
•Expensive, may not be profitable for farmers to use them.

Front 11

What biological agents are used?

Back 11

Natural predators - eat pest species.
Parasites - live in/lay eggs on pest insect.
Pathogenic - bacteria and viruses used to kill pests.

Front 12

What are environmental and economic issues with biological agents?

Back 12

Environmental:
•Natural predators may become pests themselves
•Can affect other non-pest species.

Economic:
•May be less cost-effective than chemical pesticides.

Front 13

How are integrated systems useful for getting rid of pests?

Back 13

•Combined effect reduced pests more than either method alone.
•Reduce costs.
•Reduce environmental impact because less of either is used.

Front 14

What types of fertilisers are there?

Back 14

1.Natural fertilisers - organic matter (sewage /manure).
2.Artificial fertilisers - inorganic (pure chemicals).

Front 15

What are economic and environmental issues of using Fertilisers?

Back 15

Environmental:
•Can be washed into rivers and ponds, killing plants and fish.
•Changes balance of nutrients in soil, too much of one can cause plants to die.

Economic:
•Farmers need to get the amount of fertiliser they apply just right, too much and they loose money (fertilisers washed away). Too little and productivity won't increase.

Front 16

Why do some farmers intensively rear livestock?

Back 16

So that more of the energy can be used growth to increase biomass.

Front 17

How are livestock intensively reared?

Back 17

1.Kept in warm, indoor pens where movement is restricted. (Less energy wasted on keeping warm and moving around)

2. Animals fed higher energy feed, increases energy output so more available for growth.

Front 18

How are livestock intensively reared?

Back 18

1.Kept in warm, indoor pens where movement is restricted. (Less energy wasted on keeping warm and moving around)

2. Animals fed higher energy feed, increases energy output so more available for growth.

Front 19

What are the benefits of intensive rearing?

Back 19

More food in a shorter space of time at lower cost.
However some people believe it can cause the animals pain and distress and should not be done.