A Level Biology > Ecosystems > Flashcards

Ecosystems Flashcards

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1
Q

Define an ecosystem?

A

All the living organisms that interact with one another in a defined area

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2
Q

Two factors that affect an ecosystem?

A

Abiotic and Biotic

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3
Q

Examples of biotic factors?

A

Competition, disease, food availability, territory

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4
Q

Examples of abiotic factors?

A

Light intensity, temperature, water availability, oxygen availability, soil mineral concentration

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5
Q

What produces the most energy for ecosystems?

A

The Sun

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6
Q

What is a trophic level?

A

Each stage in the food chain

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7
Q

The first trophic level is called what?

A

A producer

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8
Q

What is a producer?

A

An organism that converts light energy into chemical energy by the process of photosynthesis

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9
Q

What is a consumer?

A

Organisms that obtain their energy by feeding on other organisms

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10
Q

Why don’t food chains have more than 4 trophic levels?

A

Not sufficient biomass and stored energy left to support any further organisms

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11
Q

What is biomass?

A

The mass of living material present in a particular place of an organism

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12
Q

How do you calculate biomass?

A

Net production of biomass = gross production (initial energy) subtracted by the respiratory loss

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13
Q

What is the measurement for biomass?

A

gm-2yr-1
(grams per meter squared per year)

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14
Q

In a food chain diagram where are the producers always placed?

A

At the bottom of the pyramid

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15
Q

How much of biomass is consumed by an organism passed onto the next trophic level?

A

10 percent !!

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16
Q

Equation for the efficiency of trophic levels?

A

energy available after transfer/ energy available before transfer x 100

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17
Q

Where does the biomass go once entered into an organism?

A

The environment, lost in urine/excretion, movement, respiration

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18
Q

The unit for the efficiency of energy transfers between trophic levels?

A

kJm-2year-1

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19
Q

How much sun energy is captured by organic material?

A

1-3 percent

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20
Q

Why do organisms capture so little sun radiation?

A

Most hits the Earth and bounces back by clouds, dust and the atmospher

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21
Q

Ways that humans can manipulate biomass through an ecosystem?

A

Reducing competition by feeding them, using pesticides or fertilizers, destruction of habitat eg:deforestation, routine antibiotic application or heating

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22
Q

Name and describe what a scavenger is?

A

An organism that breaks/opens up the carcass. An example is hyenas or vultures

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23
Q

What is a decomposer?

A

An organism that feeds on and breaks down dead plant or animal matter by external digestion

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24
Q

An example of a decomposer?

A

Fungi or bacteria

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25
Detritivores are what?
Break down organic material by internal digestion, increases the SA for the decomposers
26
Examples of detritivores?
Woodlice, maggots, worms
27
Conditions needed for decomposition?
Optimum temperature for digestive enzymes, high oxygen availability, moist water availability
28
Examples of habitats with no decomposition?
Mountains, volcanoes, amber, peat bogs
29
How much of the atmosphere is nitrogen?
78%
30
Why is nitrogen essential?
Essential element for making amino acids and proteins
31
Why is the nitrogen cycle needed?
The nitrogen in the atmosphere cannot be taken up by plants. It needs to be combined with other elements such as oxygen and hydrogen
32
4 processes involved in the nitrogen cycle?
Nitrogen fixation, Ammonification, Nitrification and Denitrification
33
What is involved in nitrogen fixation?
Bacteria such as Rhizobium and Azotobacter combine Nitrogen with Hydrogen to make Ammonia
34
Where is Rhizobium found?
In the root nodules of leguminous plants, the bacteria has a mutualistic relationship with the plants
35
Describe ammonification?
Its the process of decomposers converting nitrogen-containing compounds into ammonium ions
36
Nitrification?
The ammonium ions from ammonification are converted into NITRITES and then become NITRATES used in plants
37
What is the name of the bacteria involved in nitrification?
Nitrosomonas
38
When and why does denitrification occur?
In the absence of oxygen (anaerobic conditions) Denitrifying bacteria uses the nitrates as a source of energy for respiration and nitrogen gas is released
39
What is succession?
The process in an ecosystem where abiotic factors change, causing the biotic factors to change
40
Primary succession?
Occurs in a newly found area of land, bare rock, no soil or organic matter
41
Secondary succession?
In areas of land where soil is present but has no plant or animal species (the bare earth after a forest fire)
42
Examples of primary succession occuring?
Volcano eruptions, sand blown by the wind, glaciers retreating
43
What causes fluctuations of carbon dioxide in the atmosphere?
It can occur naturally, lower in summer, higher in winter (photosynthesis rates are higher) or the combustion of fossil fuels and deforestation removing photosynthesizing biomass
44
What is a result of more carbon dioxide in the atmosphere?
More thermal energy, global warming
45
What is each stage of succession known as?
Seral stage (or sere)
46
What are the main seral stages?
Pioneer community, intermediate community and climax community
47
What is a pioneer community?
Colonizers of an inhospitable environment. Species arrive as spores or seeds carried by wind or in bird droppings flying over
48
Adaptations of a pioneer community?
Germinate rapidly, can produce large quantities of seeds/spores, can photosynthesize to produce own energy, can tolerate extreme environments, nitrogen fixation
49
What does the intermediate community include?
Secondary and tertiary consumers for example spores, seeds, ferns and moss
50
How does the community change from pioneer to intermediate?
Bare rock produces particles that form the basis of soil, releases organic components called humus. Helps make soil contain minerals such as nitrates, and help retain water
51
How are plants adapted to be tertiary consumers?
Waxy cuticle to prevent water loss, can survive in conditions without an abundance of water
52
Climax community?
Final seral stage, when the community is stable with little change over time, contains dominant plants and species (large trees. herbs or shrubs), biodiversity starts to decrease because of dominant species
53
Animal succession?
Primary consumers such as worms colonize, much slower than plant succession. Secondary consumers will arrive once suitable food source established, larger tertiary will colonize when biotic factors are favorable
54
Deflected succession?
Human activities can halt natural succession, agriculture is one of the main reasons.
55
What is the term for when succession is stopped artificially?
Plagioclimax
56
Reasons abundance of organisms changes?
Immigration and birth increase, emigration and deaths decrease
57
Abundance equation?
Number or individuals in sample divided by area of sample
58
What is carrying capacity?
The maximum population size that an environment can support
59
Difference between conservation and preservation?
Conservation is maintaining biodiversity through human action and managements, preservations is protection of an area by restricting human interference (newly discovered caves for example)
60
Small scale timber production?
Coppicing - where the tree trunk is cut close to the ground, leaves enough for new shoots to form, allows regrowth. Maintains biodiversity as trees never grow enough to block out light
61
Large scale timber production (sustainable)?
Selective cutting removing the largest trees, replanting waiting for natural regeneration, planting trees an optimal distance apart from each other to reduce competition
62
Sustainable fishing?
Overfishing has led to population of fish to decrease significantly, fisheries policies introduced. Also used nets with different mesh sizes so baby fish can escape, only fishing commercially ta certain times of the year, introduction of fish farming to supply protein
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