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Ecosystems Flashcards

1
Q

What is an ecosystem?

A

An ecosystem is made up of all the living organisms that interact with one and other in a given area as well as the physical factors in that area.

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2
Q

How big is an ecosystem?

A

Ecosystems can vary dramatically in size from 1 bacterial colony to the entire biosphere of he earth.

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3
Q

What determines the boundary or end of an ecosystem?

A

The person studying the ecosystem will determine where it ends. For example a rock pool, large oak tree, a section of a river or a playfield are all ecosystems.

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4
Q

What does it mean for an ecosystem to be dynamic?

A

The ecosystem is constantly changing due to the organisms that live within it and the environmental conditions.

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5
Q

What are biotic factors?

A

Living factors that have an impact on an ecosystem. For example the fluctuation in the population of a species affecting food availability.

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6
Q

What are abiotic factors?

A

Physical or non-living factors for example rainfall or temperature.

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7
Q

What can biotic factors also be known as?

A

The interactions between organisms that live and have once lived.

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8
Q

What is a common type of interaction between organisms?

A

Competition. Either within a population or between populations.

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9
Q

Why do organisms compete?

A

Food, space (territory) and breeding partners (mates).

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10
Q

How does light availability affect the success of plant organisms?

A

Light is required in photosynthesis which produces the simple sugars required for metabolic reactions and other processes.

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11
Q

How do plants overcome low light availability?

A

1) Larger leaves
2) Photosynthetic pigments that require lower light availability.
3) Reproductive systems that only work during optimum light conditions.

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12
Q

What kind of behaviours can changes in temperature due to season cause in plants?

A

1) Leaf fall
2) Dormancy
3) Flowering

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13
Q

What kind of behaviours can changes in temperature due to season cause in animals?

A

1) Migration

2) Hibernation

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14
Q

What does changes in temperature affect the most?

A

Metabolic reactions due to enzyme activity.

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15
Q

What is an ectotherm?

A

A species that is unable to regulate its own body temperature so its temperature is largely affected by environmental changes in temperature.

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16
Q

What will happen to plants and ectotherms in warmer temperature?

A

They will thrive and develop more tat cooler periods of time.

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17
Q

Why are endotherms not affected greatly by fluctuations in temperature?

A

They regulate their own internal temperatures, external changes will not have a great affect.

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18
Q

What does a lack of water lead to in plants and animals?

A

Water stress and eventually death.

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19
Q

Why do plants wilt when there is not enough water?

A

Water is required to keep cells turgid and upright.

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20
Q

Why is water important?

A

It is required in photosynthesis.

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21
Q

Why is it beneficial to have fast flowing cold water in aquatic ecosystems?

A

It contains high concentrations of oxygen.

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22
Q

What can happen to aquatic organisms of oxygen concentrations decrease?

A

THEY SUFFOCATE !!!!

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23
Q

What happens in water logged soil in terms of oxygen availability?

A

If the airspaces in the soil are filled with water this reduces the amount of oxygen available for the plants.

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24
Q

What are edaphic factors?

A

Soil factors

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25
What are he 3 main soil types?
Clay, loam and sandy.
26
What is clay soil like?
It has fine particles, is easily waterlogged and forms clumps when wet.
27
What is loam soil like?
It has different sized particles, it can hold water but does now become waterlogged.
28
What is sandy soil like?
It has coarse well separated particles that allows free draining. Sandy soil does not retain water but is easily eroded.
29
What is the source of energy for all ecosystems on earth?
The Sun.
30
How is energy from the sun transferred to non photosynthetic organisms?
The sun's light is turned into chemical energy through photosynthesis by plants and other photosynthetic organisms. It is transferred o the non-photosynthetic organisms as food
31
What is a food chain?
The sequence of feeding interactions between organisms in a given habitat.
32
What is a food web?
A system of interlinked food chains.
33
What is biomass?
Mass of living material.
34
What is a trophic level?
Each stage in the food chain.
35
What is a producer?
A producer will always be the first trophic level. It is an organism that coverts light energy into chemical energy through photosynthesis.
36
What is a consumer?
Organisms that obtain their energy by eating other organisms. All trophic levels other than 1 will be consumers.
37
Why do food chains rarely have more than 5 trophic levels?
The biomass and stored energy left is not enough to sustain another organism.
38
What are decomposers?
They are an important part of the food chain, they break down dead organisms and release nutrients back into the ecosystem.
39
Explain the pyramid diagram representation of a food chain?
The producers are always at he bottom with subsequent trophic levels above. The width of the block represents the number of organisms at each trophic level.
40
How do you calculate biomass at a trophic level?
Biomass present in each organism X the number of organisms in that trophic level.
41
What is the easiest way to measure biomass?
Measure the mass of fresh material present.
42
What needs to be considered when measuring mass of fresh material to calculate biomass?
Water content. With the water content being different across organisms this is difficult. Dry mass can be used instead
43
What are the issues with calculating dry mass?
1) Organisms have to be killed and placed into an oven a 80 degrees Celsius. 2) the small samples used may not be representative of your whole population.
44
Why is the biomass at a trophic level almost always less than the trophic level below?
Biomass is made up of all the cells and tissues of an organism. When an animal eats only a small amount of what they eat becomes new tissue. Only this small amount is included in the biomass calculation and available for the next trophic level to eat.
45
What is ecological efficiency?
The efficiency with which biomass is transferred from one trophic level to another.
46
What is a pyramid of energy?
A representation of the amount of biomasses or energy converted to new biomass by each trophic level in the food chain.
47
How much of the light energy that producers take up is converted into chemical energy?
1-3%
48
Why is only 1-3% of light energy converted to chemical energy by producers?
1) Not all solar energy is available for photosynthesis. ( incorrect wavelength, reflected or transmitted through leaves) 2) Other limiting factors of photosynthesis. 3) The energy is used for the photosynthetic raections.
49
What is net production?
The energy available to the next trophic level after respiration.
50
How to calculate net production?
Gross production - respiratory loss.
51
What is primary production?
The generation of biomass in a producer. It is known as secondary production in a consumer.
52
How much of biomass is converted into organic tissue in consumers?
up to 10%.
53
Why is only around 10% of biomass converted into organic tissue in consumers?
1) Not all biomass of an organism is eaten. 2) Energy transfer to the environment due to respiration and movement. 3) Excretion of indigestible parts of an organism. 4) Excretory materials such as urine.
54
Formula for ecological efficiency?
energy available after transfer/energy available for transfer. x100 for percentage
55
List some things humans do to optimise abiotic and biotic factors so that desired crops / livestock can succeed.
1) Adequate warmth and watering in greenhouses. 2) Removing competitions like using pesticides. 3) Removing threat of predators by installing fences.
56
Why does agriculture create simple food chains? Why is this important?
There are usually 2 or 3 species only involved, the crops and humans, or the grass, livestock and humans. It means that minimum energy is lost between trophic levels.
57
Why do nutrients have to be recycled through ecosystems?
They are used up by organisms and there is no external source to replenish the nutrients.
58
What is a decomposition?
A chemical process in which a compound is broken down into smaller molecules, or its constituent elements.
59
What is a decomposer?
An organism that feeds on and breaks down dead plant or animal matter, thus turning organic compounds into inorganic ones available for producers.
60
What do decomposers usually look like?
Decomposers are primarily microscopic fungi and bacteria but also include larger fungi such as toadstools and bracket fungi.
61
What are saprotrophs?
Organisms that obtain their energy from dead or waste organic material (saprobioitc nutrition).
62
How do decomposers digest their food?
They digest their food externally by secreting enzymes onto the dead organisms which break down the complex organic molecules into more simple soluble ones.
63
What are detritivores?
An organism which feeds on dead organic material, especially plant detritus.
64
How to detritivores help with decomposition?
They break down organic compounds into smaller pieces to increase the surface area for decomposers to work on.
65
Why is nitrogen important?
It is an essential element for making amino acids and nucleic acids in both plants and animals.
66
What differences do plants and animals have when it comes to nitrogen?
Animals can obtain nitrogen from the food they eat but plants have to take nitrogen from their environment.
67
What percentage of the earths atmosphere is made up of Nitrogen?
78%
68
What would happen without nitrogen fixing bacteria?
Nitrogen would soon become a limiting factor in ecosystems.
69
Give two examples of nitrogen fixing bacteria?
Azotobacter and Rhizobium
70
Where are Rhizobium bacteria found?
They grow on the roots of leguminous plants such as peas, beans and clover.
71
What kind of relationship do the Rhizobium bacteria have with the plants?
They have a symbiotic mutualistic relationship as both organisms benefit.
72
How do the plants benefit from the relationship with Rhizobium?
They gain amino acids which are produced by fixing nitrogen gas in the air into ammonia in the bacteria.
73
How do the Rhizobium bacteria benefit from the relationship with leguminous plants?
The bacteria gain carbohydrates produced by the plant during photosynthesis which they use as an energy source.
74
What is nitrification?
The process by which ammonium compounds in the soil are converted into nitrogen - containing molecules that can be used by plants.
75
What kind of reaction is nitrification?
It is an oxidation reaction so only occurs in well aerated soil.
76
What are the 2 steps of nitrification?
1) Nitrifying bacteria oxidise ammonium compounds into nitrates nitrates. 2) Nitrobacter oxidise nitrates into nitrates
77
What is denitrification?
Denitrifying bacteria converting nitrates in waterlogged soil ( an absence of oxygen) back to nitrogen gas.
78
what is ammonification?
The process by which the decomposer convert nitrogen containing molecules in a dead organism, faeces or urine into ammonium compounds.
79
What is the main source of carbon for land-living organisms?
The 0.04% of CO2 in the atmosphere.
80
Why do CO2 levels fluctuate throughout the day/
1) Photosynthesis only takes place in during daylight hours. This removes CO2 from the atmosphere 2) Respiration takes place all day in all organisms. This releases CO2 into the atmosphere. OVERALL CO2 LEVELS ARE HIGHER AT NIGHT
81
Can CO2 levels change seasonally?
Yes. Summer days have higher amounts of light and so more photosynthesis will occur removing CO2 from the atmosphere.
82
What are the 2 main reasons that global atmospheric CO2 levels have increased significantly over the past 2 years?
1) The combustion of fossil fuels - releases carbon that has been previously trapped in the fossil fuels back into the atmosphere as CO2. 2) Deforestation - The removal of significant amounts of photosynthetic biomass from earth meaning less CO2 is taken up overall during photosynthesis. The cleared forests are also burnt releasing CO2 into the atmosphere in similar ways to the combustion of fossil fuels.
83
What effect does increased CO2 levels have on temperature and what is this called?
The CO2 traps more thermal energy in the atmosphere which increases temperature. This is called the greenhouse effect.
84
What is the relationship between water temperature and the amount of CO2 dissolved in the ocean?
The higher the temperature the less CO2 dissolved. This means hat global warming reduces the amount of CO2 in the ocean sink.
85
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87
Why does succession occur?
They occur as a result of changes to the environment causing the plant and animal changes that are there to change.
88
What are the two types of succession?
Primary succession and Secondary succession
89
When does primary succession occur?
This occurs on an area of land that has been newly formed or exposed such as bare rock. There is no soil or organic material to begin with.
90
When does Secondary succession occur?
This occurs on areas of land where soil is present but it contains no plant or animal species. e.g the land after a forest fire.
91
Examples of primary succession?
Volcanoes erupting and depositing lava- the cooling of lava makes igneous rock. Sand is blown by the wind or deposited by the sea to create new sand dunes. Silt and mud are deposited at river estuaries Glaciers retreat depositing rubble and exposing rock.
92
What is a seral stage?
Each step of a succession.
93
What are the main seral stages?
1) Pioneer Community 2) Intermediate Community 3) Climax Community
94
What specifically determines a seral stage?
The abiotic factors especially the soil that make it more suitable for subsequent existence of species.
95
How does primary succession begin?
The colonisation of an inhospitable environment by organisms known as pioneer species representing the first serial stage.
96
How do the pioneer species reach the inhospitable environment?
They arrive as spores or seeds carried by the wind from near land masses or by the droppings of birds and animals
97
What are some of the adaptations that pioneer species have?
1) The ability to produce large quantities of seeds or spores which are blown by the wind and deposited on the ‘new-land’. 2) Seeds germinate rapidly. 3) Ability to photosynthesis to produce own energy. 4) Tolerance to extreme environments. 5) The ability to fix nitrogen from the atmosphere so adding to the mineral content.

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