Bio 13 - Ecosystems

Question 1

What is an ecosystem?

Answer 1

Includes all organisms living in a particular area

Question 2

What are producers?

Answer 2

Organisms that make their own food

Question 3

What is biomass?

Answer 3

The chemical energy stored in a plant

Question 4

How can biomass be measured?

Answer 4

It is measured in terms of the mass of carbon that an organism contains or the dry mass of its tissue per unit area

Question 5

How can you estimate the amount of chemical energy stored in biomass?

Answer 5

By burning the biomass in a calorimeter. The amount of heat given off tells you how much energy is in it.

Question 6

What us gross primary production?

Answer 6

Total amount of chemical energy converted from light energy by plants in a given area

Question 7

How much GPP is lost to the environemnt as heat when plants respire?

Answer 7

50%

Question 8

What is respiratory loss?

Answer 8

When heat is lost to the environment when the plants respire

Question 9

What is NPP?

Answer 9

Energy available to the plant for growth and reproduction

Question 10

What are consumers?

Answer 10

Organisms that obtain their energy by feeding on other organisms rather than using the energy of sunlight directly

Question 11

What are Saprobionts?

Answer 11

A group of organisms that break down the complex materials in dead organims into simple ones

Question 12

What is a food chain?

Answer 12

Describes a feeding relationship in which the producers are eaten by primary consumers

Question 13

What are food webs?

Answer 13

Many food chains linked together to form a food web.

Question 14

Where do consumers store chemical energy?

Answer 14

In their biomass

Question 15

How much total energy is lost in the consumers food?

Answer 15

90%

Question 16

How do consumers get energy?

Answer 16

By ingesting plant material

Question 17

Why is so much total energy lost in consumers food?

Answer 17

• Not all the food is eaten (roots, bones) so the energy they contain isn’t taken in
• Some of it is indigestible so released as faeces so that chemical energy is lost
• some energy lost through respiration or urine.

Question 18

What is consumers net production?

Answer 18

The energy left thats stored in the consumers biomass

Question 19

How do you calculate net production?

Answer 19

Chemical energy in ingested food - (chemical energy lost in faeces or urine+chemical energy lost in respiration)

Question 20

What are the two different ways to increase the amount of energy that is available for human consumption.

Answer 20

• the energy lost to the other organisms

- the energy lost through respiration

Question 21

What do insecticides do?

Answer 21

They kill insect pests that eat and damage crops.

Question 22

What do herbicides do?

Answer 22

Kill weeds.

Question 23

Why is killing weeds good?

Answer 23

Killing weeds can remove direct competition with the crop for energy from the sun
It can remove the preferred habitat or food source of the insect pests therefore reducing their numbers

Question 24

What do biological agents do?

Answer 24

Reduce the number of pests so crops lose less energy and biomass

Question 25

Explain the process of eutrophication. (5 stages)

Answer 25

1. Mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers
2. Large amounts of algae block light from reaching the plants below
3. Eventually the plants die because they’re unable to photosynthesise enough
4. Bacteria feed on the dead plant matter. The increased number of bacteria reduce the oxygen concentration in the water nu carrying out aerobic respiration
5. Fish and other aquatic animals organism die because there isn’t enough dissolved oxygen

Question 26

Why are nutrients lost when crops are harvested?

Answer 26

Crops take in minerals from the soil as they grow. When crops are harvested they are removed from the field and cannot decompose and die so the minerals are not returned to the soil.

Question 27

What does adding fertilisers do?

Answer 27

Replace lost minerals

Question 28

What are artificial fertilisers?

Answer 28

They are organic and they contain pure chemicals as powders or pellets.

Question 29

What are natural fertilisers?

Answer 29

They are organic matter. Includes manure, composted vegetables and crop residue

Question 30

What is leaching?

Answer 30

When water-soluble compounds the soil are washed away. This can lead to eutrophication

Question 31

Why is leaching of phosphate less likely than nitrates?

Answer 31

Phosphates are less soluble in water

Question 32

What is nitrogen fixation?

Answer 32

When a nitrogen gas in the atmosphere is turned into nitrogen-containing compounds.

Question 33

What is biological nitrogen fixation carried out by?

Answer 33

Bacteria such as rhizobium

Question 34

How do bacteria like rhizobium do biological nitrogen fixation?

Answer 34

They turn nitrogen into ammonia, which goes on to form ammonium ions to solution that can be used by plants

Question 35

Where is rhizobium found?

Answer 35

inside root nodules of leguminous plants

Question 36

What is ammonififcation?

Answer 36

When nitrogen compounds from dead organisms are turned into ammonia by saprobionts, which goes on to form ammonium ions

Question 37

What is nitrification?

Answer 37

When ammonium ions in the soil are changed into nitrogen compounds that can be used by plants

Question 38

How does nitrification work?

Answer 38

1. Nitrifying bacteria called Nitrosomonas change ammonium ions into nitrites
2. Then other nitrifying bacteria called Nitrobacter change nitrites into nitrates

Question 39

What is denitrification?

Answer 39

When nitrites in the soil are converted into nitrogen gas bu denitrifying bacteria- they use nitrates in the oil to carry out respiration and produce nitrogen gas

Question 40

What conditions does denitrification happen under?

Answer 40

Anaerobic conditions