topic 9 Ecosystems and material systems

Question 1

what is an ecosystem?

Answer 1

An ecosystem is the interaction of a community with non-living (abiotic) parts of the environment.

Question 2

name 4 things that plants may compete for?

Answer 2

light
space
water
and mineral ions

Question 3

name 4 things animals may compete for?

Answer 3

space
food
water
and mating partners

Question 4

what is an abiotic factor?

Answer 4

a non-living factor that can affect a community.

Question 5

what is a biotic factor?

Answer 5

a living factor that can affect a community.

Question 6

name the 7 abiotic factors that can affect a community

Answer 6

light intensity
temperature
moisture levels
soil PH and mineral content
wind intensity and direction
carbon dioxide levels
Oxygen levels for aquatic animals

Question 7

explain how light intensity as an abiotic factor affects a community?

Answer 7

light intensity is required for photosynthesis
the rate of photosynthesis affects the rate at which a plant grows
plants can be food sources or shelter for many organisms

Question 8

explain how temperature as an abiotic factor affects a community?

Answer 8

temperature also affects the rate of photosynthesis

Question 9

explain how moisture levels as an abiotic factor affects a community?

Answer 9

Both plants and animals need water to survive

Question 10

explain how soil PH and mineral levels as an abiotic factor affects a community?

Answer 10

soil PH affects the rate of decay and therefore how fast mineral ions return to soil.
Different species of plants thrive in different nutrient concentration levels.

Question 11

explain how wind intensity and direction as an abiotic factor affects a community?

Answer 11

wind affects the rate of transpiration in plants
transpiration affects the tempreture as a plant, and the rate of photosynthesis because it transports water and mineral ions in leaves.

Question 12

explain how carbon dioxide levels as an abiotic factor affects a community?

Answer 12

CO2 affects the rate of photosynthesis in plants.

It also affects the distribution of organisms as some thrive in high CO2 environments

Question 13

explain how oxygen levels as an abiotic factor affects an aquatic community?

Answer 13

levels in water vary greatly, unlike oxygen levels in air.

most fish need a high concentration of oxygen to survive aswell.

Question 14

Name the 4 biotic factors that affect a community

Answer 14

Food availability
new predators
new pathogens
competition

Question 15

what is interdependence?

Answer 15

interdependence describes how organisms in a community depend on other organisms for vital services

Question 16

name some benefits of having a stable community

Answer 16

population sizes remain roughly consistent
when they are lost it is very hard to replace them
examples are tropical rainforests and coral reefs.

Question 17

what is a stable community?

Answer 17

a stable community is a community in which all biotic and abiotic factors are in balance.

Question 18

what is a parasitical relationship?

Answer 18

a parasitical relationship is one that involves one species taking nutrients to the detriment of another species.

Question 19

what is a parasite?

Answer 19

a parasite is the smaller species that lives directly within or on a larger species and benefits at the expense of the other species.

Question 20

what is a mutualistic relationship?

Answer 20

A mutualistic relationship is where a smaller species that lives directly within or on a larger species it provides some benefit or resource to the other species, for instance providing nutrients

Question 21

give an example of a parasitical relationship?

Answer 21

In humans, the ​tapeworm ​is a parasite that lives inside the gut. It ‘steals’ nutrients from the host and can lead to ​malnutrition.

Question 22

give an example of a mutualistic relationship?

Answer 22

algae and fungi live together to form lichens. ​Algae can photosynthesise to provide sugars for the fungi, whereas the fungi allow the algae to live in more extreme conditions than those under which it would normally thrive.

Question 23

how can we calculate the number of certain living organisms in a given area?

Answer 23

by using quadrats and transects.

Question 24

how do you complete a transect/

Answer 24

• Divide the field into 100 equal 1m x 1m squares.
• Use a random number generator to randomly select a single square.
• Take a 1m x 1m quadrat and place it in the selected square.
• Count the number of clover in the square. - Repeat with a different square 4 times, and average the 5 results.
• Multiply the average by 100 to estimate the number of clover in the field.

Question 25

Name some Positive human interactions with ecosystems

Answer 25

Maintaining rainforests, ensuring habitats here are not destroyed. Raising awareness among the public about how to protect ecosystems - e.g through large scale community projects Reducing pollution and monitoring changes over time. Reserving areas of scientific interest by stopping humans from going there. Replanting hedgerows and woodlands to provide habitats which were previously destroyed

Question 26

Name some Negative human interactions with ecosystems

Answer 26

Production of greenhouse gases leading to global warming. Introducing non-indigenous species into the environment, which prey on native species. Producing sulfur dioxide in factories which leads to acid rain – affects habitats. stopping humans from going there. Chemicals used in farming leak into the environment - if they leak into a lake, this can cause ​eutrophication - ​excessive growth of plant life which can deplete the body of water of oxygen (making it less able to sustain other species such as fish) Clearing land in order to build on, reducing the number of habitats Overfishing ​which reduces biodiversity and can lead to endangerment of some species

Question 27

What measures have been put in place to maintain biodiversity?

Answer 27

1. Breeding programs: to stop endangered species from becoming extinct. 2. Protection of rare habitats: to stop the species here from becoming extinct, if damaged they may even be regenerated to encourage populations to live here 3. Reintroduction of hedgerows and field margins around land where only one type of crop is grown: maintains biodiversity as the hedgerows provide a habitat for lots of organisms (because a field of one crop would not be able to support many organisms) and field margins provide areas where wild flowers and grasses can grow. 4. Reduction of deforestation and carbon dioxide production: reduces the rate of global warming, slowing down the rate that habitats are destroyed 5. Recycling rather than dumping waste in landfill: reduce the amount of land taken up for landfills, and slows the rate we are using up natural resources.

Question 28

Explain the stages of the carbon cycle

Answer 28

● CO​2 ​is REMOVED from the air in photosynthesis by green plants and algae – they use the carbon to make carbohydrates, proteins and fats. They are eaten and the carbon moves up the food chain. ● CO​2 ​is RETURNED to the air when plants, algae and animals respire. Decomposers (a group of microorganisms that break down dead organisms and waste) respire while they return mineral ions to the soil. ● CO​2 ​is RETURNED to the air when wood and fossil fuels are burnt (called combustion) as they contain carbon from photosynthesis.

Question 29

Explain stages of the water cycle?

Answer 29

● The sun’s energy causes water to evaporate from the sea and lakes, forming water vapour. ● Water vapour is also formed as a result of transpiration in plants. ● Water vapour rises and then condenses to form clouds. ● Water is returned to the land by precipitation (rain, snow or hail), and this runs into lakes to provide water for plants and animals. ● This then runs into seas and the cycle begins again. ● In areas of drought, we can harness the water cycle to produce ​potable ​(drinkable) water. For example, ​desalination​ is the process by which we remove salt and other minerals/impurities from seawater to make it drinkable. It is performed by a process called ​reverse osmosis ​and generally occurs on a large scale.

Question 30

Nitrates

Answer 30

● Nitrogen gas in the atmosphere is too unreactive so cannot be used directly by plants. ● Nitrogen-fixing bacteria present in the root nodules of legume plants convert nitrogen gas into nitrates that can be used for growth. ● Lightning ​can convert nitrogen gas into nitrates ● The ​Haber process ​converts the hydrogen gas into ammonia. ● Plants ​absorb nitrates​ through the roots by active transport.

Question 31

Define population

Answer 31

All organisms of the same species living | with one another in a habitat

Question 32

Define community

Answer 32

All of the populations of different species | living together in a habitat

Question 33

Organisms within a community are described as being ‘interdependent’. What does this mean?

Answer 33

● Organisms are dependent upon each other. ● A change in the population of one species can affect other populations within a community

Question 34

Give some examples of interdependence in a | community

Answer 34

● Plants depend on pollinators e.g. bees ● Herbivores are dependent on plants ● Animals are dependent on mates

Question 35

Describe how communities are affected by | environmental conditions

Answer 35

● Environmental conditions (e.g. temperature, light intensity, water availability) affect the abundance and distribution of organisms within communities ● e.g light intensity affects the rate of photosynthesis in producers which serve as a source of food and shelter for other organisms

Question 36

Describe how communities are affected by pollutants

Answer 36

● Toxic chemicals (e.g. pesticides) bioaccumulate in food chains to deadly concentrations at higher trophic levels, killing tertiary and quaternary consumers ● Fertilisers that contaminate water sources can cause eutrophication, killing multiple populations within a community ● Air pollution can affect the ability of some plant species to survive

Question 37

Describe how competition affects communities

Answer 37

● The presence of competitors affects population distribution and size ● If one species is better adapted to survive in a certain environment, it will outcompete other species, causing their populations to decline

Question 38

Describe how predation affects communities

Answer 38

● Predation affects prey populations within a community ● e.g. if the number of predators decreases, the number of prey will increase as fewer are killed ● Populations of all other organisms within the food chain will also be affected

Question 39

What piece of apparatus is used to measure the | abundance and distribution of organisms in an area?

Answer 39

A Quadrat

Question 40

What piece of apparatus is used to study the | distribution of organisms across a gradient?

Answer 40

A Belt Transect

Question 41

What is biodiversity?

Answer 41

he variety of living organisms in an | ecosystem

Question 42

How does fish farming impact biodiversity?

Answer 42

● Food used to feed the fish and waste can leak into water sources, causing eutrophication ● Parasites from fish farms may spread and contaminate surrounding ecosystems ● Other organisms may become tangled in netting

Question 43

How does the use of fertilisers affect biodiversity?

Answer 43

Excess fertiliser can wash into water sources causing eutrophication and death of many species. This reduces biodiversity.

Question 44

Describe how fertilisers can cause eutrophication

Answer 44

1. Fertiliser run-off into rivers and lakes 2. Nutrients build-up in water 3. Algal bloom blocks sunlight 4. Aquatic plants cannot photosynthesise ∴ less oxygen produced 5. They die and decompose 6. Decomposers further deplete oxygen levels 7. Animals can no longer respire aerobically so die.

Question 45

How does the introduction of non-indigenous species affect biodiversity?

Answer 45

● They may out-compete native species, causing a reduction in population numbers ● Native species may become the prey of non-indigenous species ● They may bring new diseases which could kill large numbers of native species, reducing biodiversity

Question 46

How can humans more positively impact | biodiversity?

Answer 46

● Protection of endangered species e.g. making hunting illegal, breeding programmes increase population sizes ● Conservation schemes e.g. national parks, seed banks, zoos ● Reforestation ● Sustainable farming e.g. fewer pesticides ● Minimising global greenhouse gas production

Question 47

What is reforestation?

Answer 47

The Replanting of trees to help restore biodiversity.

Question 48

How do conservation schemes protect biodiversity?

Answer 48

They prevent species from becoming extinct and increase population numbers, maintaining biodiversity.

Question 49

Outline the benefits of maintaining biodiversity.

Answer 49

● Ensures future food requirements can be met, reduces damage to food chains ● Increases the likelihood of species adapting to future environmental change ● Many plant species are yet to be discovered and may contain chemicals that could be used in future medicines ● Safeguarding valuable future resources e.g. fuels, paper ● Aesthetics - culture, ecotourism etc. ● Jobs provided by ecotourism, reforestation and conservation schemes

Question 50

What are the three types of nutrient cycle?

Answer 50

● Carbon cycle ● Water cycle ● Nitrogen cycle

Question 51

Why are the nutrient cycles important?

Answer 51

● Carbon, water and nitrogen are essential to life ● There is a fixed amount of nutrients on Earth which must be constantly recycled

Question 52

Describe how materials cycle through the living and | non-living components of an ecosystem

Answer 52

● Organisms take in elements from their surroundings e.g. soil, air ● Elements converted to complex molecules which become biomass ● Elements transferred along food chains ● Elements returned to environment during excretion and decomposition of dead organisms

Question 53

Describe the stages of the carbon cycle

Answer 53

1. Photosynthesising plants remove CO2 from the atmosphere 2. Eating passes carbon compounds along a food chain 3. Respiration in plants and animals returns CO2 to the atmosphere 4. Organisms die and decompose. Decomposers (bacteria and fungi) break down dead material and release CO2 via respiration 5. Combustion of materials (e.g. wood, fossil fuels) releases CO2

Question 54

Describe the stages of the water cycle

Answer 54

1. Energy from the sun evaporates water from sources such as lakes and oceans. Transpiration also releases water vapour. 2. Water vapour rises, cools and condenses forming clouds 3. Precipitation occurs 4. Water is absorbed by the soil and taken up by roots. Some is used in photosynthesis or becomes part of the plant, entering the food chain. 5. Excretion returns water to the soil 6. Surface runoff returns to streams, rivers and eventually the sea

Question 55

What is potable water?

Answer 55

Drinking water

Question 56

How can potable water be prepared?

Answer 56

Desalination

Question 57

What is desalination?

Answer 57

A process that removes salts from saline | water

Question 58

Name two methods of desalination

Answer 58

● Thermal desalination | ● Reverse osmosis

Question 59

Describe thermal desalination

Answer 59

Salt water is boiled. Water evaporates, rises and condenses down a pipe. This separates pure water from salts.

Question 60

Describe reverse osmosis

Answer 60

● Saline water pumped into a vessel containing a partially permeable membrane at high pressure ● High pressure forces water molecules to move from an area of low water concentration (high salt concentration) to an area of high water concentration (low salt concentration) ● Pure water separated from salts

Question 61

What do plants use to make proteins?

Answer 61

Nitrates

Question 62

Why can’t nitrogen be used directly by plants to form | proteins?

Answer 62

Nitrogen is unreactive

Question 63

Name the four types of bacteria involved in the | nitrogen cycle

Answer 63

● Decomposers ● Nitrogen-fixing bacteria ● Nitrifying bacteria ● Denitrifying bacteria

Question 64

What is the role of decomposers in the nitrogen | cycle?

Answer 64

● Break down proteins and urea into ammonia ● Ammonia dissolves in solution forming ammonium ions

Question 65

What is the role of nitrogen-fixing bacteria in the | nitrogen cycle?

Answer 65

● Convert nitrogen gas into ammonia ● Ammonia dissolves in solution forming ammonium ions

Question 66

Where are nitrogen-fixing bacteria found?

Answer 66

● Soil | ● Root nodules of legumes

Question 67

What type of relationship is exhibited between | nitrogen-fixing bacteria and legumes?

Answer 67

● Mutualistic relationship ● Plants receive ammonium ions from bacteria ● Bacteria gain sugars from the plant

Question 68

What is the role of nitrifying bacteria in the nitrogen | cycle?

Answer 68

● Convert ammonium ions into nitrites | ● Convert nitrites into nitrates

Question 69

What is the role of denitrifying bacteria in the | nitrogen cycle?

Answer 69

Convert nitrates into nitrogen gas

Question 70

Where are denitrifying bacteria commonly found?

Answer 70

Waterlogged soils

Question 71

Describe the stages of the nitrogen cycle

Answer 71

1. Lighting and nitrogen-fixing bacteria convert nitrogen gas to ammonia which dissolves to form ammonium ions 2. Nitrifying bacteria convert ammonium ions to nitrate ions which are taken up by plants and used to build proteins 3. Feeding passes nitrogen through the food chain 4. Organisms die and decompose. Decomposers break down proteins and urea to form ammonia which dissolves to form ammonium ions 5. Denitrifying bacteria convert nitrates in the soil back to nitrogen gas

Question 72

How can the amount of nitrates in the soil be | increased?

Answer 72

● Using fertilisers e.g. animal manure, compost, artificial fertilisers ● Crop rotation replenishes nitrates that may have been depleted by the previous crop e.g. planting a nitrogen-fixing crop

Question 73

What is meant by decomposition?

Answer 73

The breakdown of dead materials into | simpler organic matter

Question 74

How do decomposers break down dead matter?

Answer 74

Decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules.