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Biology > 23 - Ecosystems > Flashcards

23 - Ecosystems Flashcards

1
Q

Ecosystem

A

is made up of all the living organisms that interact with one another in a defined area, as well as the physical factors in that region

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2
Q

biotic factors

A

the living factors
- size of a population, competition

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3
Q

abioic

A

the non-living factors
- rainfall and temperature

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4
Q

light as an abiotic factor

A
  • plants are affected by light as it is needed for photosynthesis
  • plants do have adaptations eg wide leaves
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5
Q

temperature as an abiotic factor

A
  • effects enzyme controlled reactions
  • plants develop rapidly in warmer temps
  • activity of ectotherms also depends on temperature
  • can trigger migration and hibernations
  • trigger leaf-fall, dormancy, and flowering
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6
Q

water availability as an abiotic factor

A
  • lack of water means water stress, which can cause death
    -plants wilt
  • required for photosynthesis
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7
Q

oxygen availability as an abiotic factor

A
  • ## suffocation of aquatic organisms
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8
Q

three types of soil

A

clay- this has fine particles, is easily waterlogged and forms clumps when wet

loam- has different sized particles, it retain water but doesn’t become water logged

sandy- coarse, well-separated particles that allow free draining - does not retain water and can be eroded

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9
Q

what are food chains/webs

A
  • diagrams that show the transfer of biomass and therefor energy through the organisms of an ecosystem.
  • each stage is called a trophic level
  • first stage is always a producer
  • subsequent trophic levels are consumers
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10
Q

what is a producer

A

an organisms that converts light energy into chemical energy by the process of photosynthesis

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11
Q

what is a consumer

A

organisms that obtain their energy by feeding on other organisms

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12
Q

Explain why food chains rarely have more than 3-4 trophic levels.

A

as there is not sufficient biomass and stored energy left to support any further organisms

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13
Q

what are decomposers

A

break down dead organisms releasing nutrients back into the ecosystem

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14
Q

what is biomass

A

the living material present in a particular place of organism

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15
Q

how do you calculate biomass at each trophic level

A

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

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16
Q

way to measure biomass

A
  • measure the mass of fresh material
  • water content must be removed
    • or calculate dry mass
      -> place organism in an oven at 80’c until water has evaporated (shown by two identical mass readings)
      -> to minimise destruction only a small sample is used
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17
Q

units for biomass

A

land; grams per square metre
water; grams per metre

18
Q

unit for energy available at each trophic level

A

kilojoules per metre squared per year

19
Q

why is energy at trophic levels different

A
  • only a small proportion of food ingested is converted into new tissue - this biomass is what is consumed for the next trophic level
20
Q

what is ecological efficiency

A

the efficiency with which a biomass or energy is transferred from one trophic level to the next

biomass transferred/biomass intake x 100

21
Q

why do producers only convert 1-3% of light energy into biomass

A
  • not all solar energy is available is used for phs. 90% is reflected, some is transmitted through the leaf and some is not a usable wavelength
  • other factors can affect PHS
  • energy is lost as it is used for PHS
22
Q

what is gross production

A

total solar energy a plant converts to organic matter

22
Q

what is net production

A

energy available for the next trophic level

gross production - repiratory loses

23
Q

why is gross and net prodcution different

A

plant use some of the energy in the organic matter fir respiration

24
why is biomass of a consumer less than what they have consumed
- not all biomass is eaten - eg roots may root be eaten - some energy is transferred to the environment as metabolic heat due to respiration and movement - some part of an organism are eaten but not digestible - instead they are egested -some energy is lost in excretory materials like urine
25
what is decomposition- what is the point in it
when a compound is broken down into smaller molecules or constituent elements - often essential elements cannot be directly used by organisms when is it in dead or waste matter - so it has to be processed from organic to inorganic elements which are a more usable form - and are returned to the environment
26
what is a decomposer
organisms that feeds on and breaks down dead plant or animal matter, turning organic compounds into inorganic ones available to PHS producers un the ecosystems - primarily fungi and bacteria (microscopic)
27
why are decomposers saprotrophs
they obtain energy from dead or waste organic materials
28
how do decomposers digest food
- externally - they secrete enzymes onto dad matter - enzymes break down organic matter into simple soluble molecules - decomposer then absorbs these molecules - through this process they release stored inorganic compounds and elements back into the environment
29
what are detritivores
- they speed up the decay process by feeding on detritus - dead or decaying material - they break it down into smaller pieces of organic material, which increases the SA for decomposers - examples are woodlice and earthworms
30
steps of the nitrogen cycle
Nitrogen fixation Nitrification Denitrification Ammonification
31
why does nitrogen have to be recycled
Nitrogen in the air N2 cannot be taken in by plants. so to be used by organism nitrogen has to be combined with other elements - bacteria plat a role in this
32
nitrogen fixation
the combination of atmospheric nitrogen with hydrogen to produce ammonia N2 + H2 -> NH3 carried out by nitrogen fixing bacteria such as Azotobacter and Rhizobium. They contain the enzyme nitrogenase.
33
where are the bacteria for nitrogen fixation found, why is it beneficial for organisms
Azotobacter - free soil bacteria Rhizobium - inside root nodules, growths on leguminous plants like peas. - bacteria have a symbiotic relationship. the plant gains amino acids from Rhizobium which is produced by nitrogen fixing - bacteria gain carbohydrates from the plant from PHS, which is energy source
34
nitrification
process where ammonium compounds in the soil are converted into nitrogen-containing molecules that can be used by plants - oxidation R. so occurs in well-aerated soil 1) Nitrifying bacteria (Nitrosomonas) oxidise ammonium compounds into nitrates (NO2-) 2) Nitrobacter oxidise nitrites into nitrates (NO3-) Nitrate ions are highly soluble so can enter plants
35
Denitrification
- in the absence of oxygen denitrifying bacteria convert nitrates in the soil back into nitrogen gas - only happens in anaerobic conditions -Pseudomonas denitrificans use nitrates as a source of energy and nitrogen gas is released
36
Ammonification
decomposers convert nitrogen-containing molecules in dead organisms and faeces into ammonium compounds
37
transects
- a line or belt transect is used - a line transect involves laying out a line and taking samples at regular intervals - a belt transect is when two parallel lines are and samples are taken of the area between the specified points - examples of systematic non-random sampling
38
why does abundance of organisms change
- immigration and births increase number - emigration and deaths decrease number
39
how to measure plant abundance
- place quadrats in the area estimates N'= N' of individuals in sample/ area of sample(m2)
40
capture-mark-release
- capture as many organisms in sample area - mark each individual - release the marked animal into the area and allow them to redistribute throughout the habitat - recapture as many marked and unmarked individuals in sample area - record number of marked and unmarked present - use Lincoln index estimate pop = N' in first sample x second sample/measures of recaptures marked individuals
41
how to measure amount of diversity in a habitat
Simpsons diversity D= diversity index N= number of organisms in ecosystem n= number of individuals of each species 1=infinite diversity 0= no diversity

Biology (24 decks)

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