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Biology > Module 6- ecosystems > Flashcards

Module 6- ecosystems Flashcards

1
Q

Define ecology

A

the study of the relationship between organism sand their environment

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2
Q

Define ecosystem

A

is made up of all living things that interact with each other in a defined area but also the physical factors present in a region. They vary in size and are all dynamic as they are constantly changing.

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3
Q

Define biotic factors

A

living factors which often compete for food or space

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4
Q

How does light affect ecosystems?

A

plants are directly affected by the light availability for photosynthesis.
in areas of low light plants may have larger leaves
they may also develop photosynthetic pigments that require less light

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5
Q

How does temperature affect ecosystems?

A

plants will develop more rapidly in warmer conditions as will ectothermic animals
changes in temperature can trigger migration or hibernation in some animal species.

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6
Q

How does water availability affect ecosystems?

A

lack of water leads to water stress which can cause death
lack of water causes most plants to wilt

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7
Q

How does oxygen availability affect ecosystems?

A

if water becomes too warm or the flow rate too slow the resulting drop in oxygen concentration can lead to suffocation in aquatic organisms.

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8
Q

What is the first trophic level and define it?

A

A producer- organism that converts light energy into chemical energy by photosynthesis

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9
Q

What are consumers and what trophic levels are they?

A

-organisms that obtain their energy by by feeding on other organisms
-the subsequent trophic levels after the producer are all consumers

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10
Q

Why do food chains rarely go beyond the quaternary consumer?

A

as there isn’t sufficient biomass and stored energy left to support any further organisms

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11
Q

What do decomposers do?

A

break down dead organisms releasing nutrients back into the ecosystem

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12
Q

What is biomass?

A

-the mass of living material present in a particular place or organism

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13
Q

What can biomass be equated to?

A

energy content

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14
Q

How do you calculate the biomass present at each trophic level?

A

multiply the biomass present in each organism by the total number of organisms at that trophic level

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15
Q

What does the calculation of biomass not account for?

A

seasonal changes

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16
Q

What is the easiest way to measure biomass? How can this be difficult?

A

-measure the mass of fresh material present and discount water content
-the water content is different for each individual

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17
Q

How do scientists usually calculate the dry mass of an organism? How can this be inaccurate?

A

-organism needs to be killed and placed in an oven at 80 deg C until all the water has evaporated- this point is indicated by 2 identical mass readings
-for this only a small sample is taken so may not be representative

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18
Q

Why is biomass transfer inefficient?

A

-only a small proportion of the food animals ingest is converted into new tissue and it’s only this part of the biomass which is available for the next trophic level to eat
-some energy is transferred to the environment as as metabolic heat as a result of respiration

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19
Q

What is the energy available at each trophic level measured in? Why?

A

KJm^(-2)yr(-1)
kilojoules per metre squared per year
-to allow for changes in photosynthetic production and consumer feeding patterns throughout the year

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20
Q

What can the amount of biomass in trophic levels be represented by?

A

a pyramid of energy

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21
Q

What percentage of sunlight do producers convert into chemical energy and hence biomass? Why is this?

A

1-3%
not all solar energy is available for photosynthesis, other factors may limit photosynthesis e.g water availability, a proportion of the energy is lost due to photosynthetic reactions

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22
Q

How do you work out net production?

A

gross production - respiratory losses

23
Q

How do you calculate the efficiency of biomass transfer?

A

biomass transferred/biomass intake x 100

24
Q

How many trophic levels are there when cultivating plants for human consumption?

A

2- producer and primary consumer which means minimum energy is lost since there are fewer trophic levels present than in the natural ecosystem

25
Q

Define decomposition

A

chemical process where a compound is broken down into smaller molecules

26
Q

What is a decomposer?

A

-organism that feeds on and breaks down dead plant or animal matter, thus turning organic compounds into inorganic ones

27
Q

Why are decomposers saprotrophs?

A

because they obtain their energy from dead organic material
-they digest their food externally by excreting enzymes onto dead organisms which break down the molecules for the decomposer to then absorb

28
Q

How do detrivores speed up the decay process?

A

by feeding on detritus (dead and decaying material) and breaking it down into smaller pieces of organic material to increase the SA for decomposers to work on
-they perform internal digestion

29
Q

Give examples of detrivores

A

woodlice, earthworms

30
Q

Give examples of decomposers

A

microscopic fungi and bacteria

31
Q

Describe the process of ammonification

A

-when an organism dies or produces waste, it is decomposed by saprobiants which releases the nutrients contained inside
-saprobiants decompose the organisms biomass by extracellular digestion and inorganic ammonium ions are released into the soil

32
Q

Describe the process of nitrification

A

-the process by which ammonium ions in the soil are converted nitrates by nitrifying bacteria oxidising ammonium ions into nitrites
-another bacteria e.g nitrobacter oxidises nitrites to nitrates
-nitrate ions are highly soluble so is the form most nitrogen enters the plant

33
Q

Describe the process of dentrification

A

in the absence of oxygen e.g in waterlogged soils, dentrifying bacteria convert nitrates in the soil back to nitrogen gas

34
Q

What happens if there is an accumulation of dead organic matter with no decomposers?

A

-the carbon they contain may become trapped and over millions of years these remains form fossil fuels

35
Q

What happens to the carbon when animals fall to the ocean floor?

A

due to cementation and compression they form into a sedimentary rock where crude oil and natural gases may form

36
Q

Why is there less CO2 in the atmosphere in the summer?

A

due to increased photosynthesis

37
Q

Define succession

A

changes in an ecosystem overtime

38
Q

Define climax community

A

ecosystem that results from succession

39
Q

What is primary succession?

A

takes place on newly exposed land that is initially colonised by living things

40
Q

What is secondary succession?

A

takes place where part of an ecosystem is disturbed and remnants of the previous community remain

41
Q

Describe the stages of primary succession

A

1)pioneer species- are the first species to colonise the newly exposed land and are specialised to live in the harsh conditions e.g marram grass
2)soil formation- pioneer species help to break down substances on the exposed land to form soil. When the pioneer species die, they are also decomposed which contributes to soil formation
3)colonisation by new species- the formation of soil makes the environment less hostile and when the new species die the organic matter within the species is released into the soil by decomposition
4)altering abiotic conditions- when species die the composition of the soil is changed. New species colonise the area which could alter the environment so the pioneer species can no longer survive

42
Q

Describe the stages of secondary succession

A

1)pioneer species- colonise the damaged land and tend to be larger in secondary than primary succession. The environment in secondary succession is more nutrient rich than in primary succession because there is a nutrient layer
2)colonisation by new species- as pioneer species die, the soil becomes more nutrient rich and stable. New species outcompete the older species and become more dominant as they cause a shift in the organisms present in the ecosystem
3)increased complexity- as more species colonise the land, the complexity of an ecosystem increases making it more biodiverse
4)climax community- the ecosystem eventually reaches an equilibrium point (where species composition is no longer changing and resembles the community that existed before it was disturbed)

43
Q

What is depleted succession? Give an example

A

-ecosystems are disturbed by humans so succession can’t take place
-e.g grazing of farm animals on grasslands prevents it from becoming a woodland

44
Q

Define ‘distribution of organisms’

A

-where individual organisms are found within an ecosystem

45
Q

What are 2 ways of measuring distribution?

A

-a line transect
-a belt transect

46
Q

How does a line transect work?

A

it records the species that make contact with the tape at regular intervals along the transect

47
Q

How does a belt transect work?

A

-2 parallel lines are marked and samples are taken of the area between these specified points

48
Q

What is systematic sampling?

A

different areas within an overall habitat are identified which are then sampled separately.

49
Q

Why is systematic sampling used?

A

allows scientists to study how the differing abiotic factors in different areas affect the distribution of organisms

50
Q

What is the ‘abundance of organism’?

A

number of individuals of a species present in an area at any given time

51
Q

What are 2 things that will increase the abundance of organisms in an area?

A

immigrations and birth

52
Q

How do you measure the abundance of plants?

A

quadrats are placed randomly in an area

53
Q

How do you measure the abundance of animals?

A

capture-mark-release-recapture technique
-capture as many individuals as possible in the sample area
-mark them
-release them back into the sample area and allow time for them to redistribute themselves
-recapture as many individuals as possible in the sample area
calculate using=
number in 1st sample x number in second sample / number of recaptured marked individuals

Biology (17 decks)

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