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ocr gateway a gcse biology > B4: Community level systems > Flashcards

B4: Community level systems Flashcards

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1
Q

what are ecosystems

A
  • dynamic systems consisting of communities of interacting living organisms and their physical environment
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2
Q

what is a community

A
  • all the organisms within the ecosystem - diff species living together in an area at a particular time
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3
Q

what is a population

A
  • all the organisms of a single species living in one area at a particular time
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4
Q

what is a predator

A
  • an animal which hunts + kills other animals
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5
Q

what is an adaptation

A
  • a feature which allows an organism to live successfully in its environment
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6
Q

what is a prey

A
  • an animal that is hunted + killed by other animals
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7
Q

what is biotic

A
  • the living organisms in an area and their interactions
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8
Q

what is abiotic

A
  • the non-living factors in an area
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9
Q

what is mutualism

A
  • a relationship where both organisms receive some benefit
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10
Q

what is parasitism

A
  • a relationship where only one of the organism gains and the other suffers
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11
Q

what is predation

A
  • a relationship where one organism eats another organism
    > the population sizes affect each other
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12
Q

what is competition

A
  • two or more organisms requiring the same source
  • plants + animals have to compete for resources if materials are limited
    > may result in weaker competitors dying or leaving that area (weaker plant species often die)
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13
Q

ecosystems can be ____ or ____

A
  • terrestrial
    > tundra, hot dessert, rainforest
  • aquatic
    > freshwater, coral reef, ocean
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14
Q

what are the two factors that affect an ecosystem

A
  • biotoic factors
  • abiotic factors
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15
Q

what are the biotic factors that affect ecosystems

A
  • competition - for food, water, shelter, partners, light, CO2, minerals
  • disease
  • food chains
    > predators
  • food availability
  • human activity
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16
Q

what are the abiotic factors that affect ecosystem

A
  • light intensity
  • temperature
  • moisture levels
  • soil pH
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17
Q

how does light intensity affect communities

A
  • light needed for photosynthesis
  • greater light availability, greater success of plant
  • plant evolve to grow successfully in diff light intensities
    > e.g. areas of low light, plants often have larger leaves
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18
Q

how does temperature affect communities

A
  • temp has greatest effect on enzyme controlling metabolic reactions
  • plants develop quicker in warmer temps as their metabolisms will be faster
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19
Q

how does moisture level affect communities

A
  • for most animals + plants lack of water leads to death
    > water is main component of blood plasma
    > plants wilt with less water as water is used to keep cells turgid which makes plants upright
    > water needed for photosynthesis
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20
Q

how does soil pH affect communities

A
  • pH of soil affects biological activity in soil + availability of certain minerals
  • some plants grow better in acidic soil (pH < 7)
    > rhododendrons + ferns
  • others grow better in alkaline soils (pH > 7> cucumber + cauliflower
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21
Q

how can you measure light intensity (equipment)

A
  • light meter
    > lux (units)
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22
Q

how can you measure availability of moisture (equipment)

A
  • humidity sensor
    > % (units)
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23
Q

how can you measure pH (equipment)

A
  • pH probe
    > no units
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24
Q

how can you measure temperature (equipment)

A
  • thermometer
    > degrees Celsius
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25
Q

what is interdependence

A
  • how different organisms depend on each other in a community
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26
Q

what are the interactions between organisms known as

A
  • ecological relationships
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27
Q

what are the 3 main types of ecological relationships

A
  • predation - relationship where predator feeds on prey
  • mutualism - both organisms gain from relationship
  • parasitism - only one organism (parasite) gains from relationship
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28
Q

why do animals need to eat

A
  • to get energy
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29
Q

what does the chemical energy from food allow us to do

A
  • to do respiration to make our cells work + keep our bodies warm
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30
Q

what is a producer

A
  • on organism that can make its own food (nutrients) by photosynthesis
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31
Q

what is a consumer

A
  • an organism that can’t make its own food
    > they have to eat other organisms to gain energy
  • all animals are consumers
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32
Q

what is a decomposer

A
  • an organisms that gets its energy from feeding on dead or decaying material
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33
Q

how is energy transferred between organisms - producers

A
  • energy from sun transferred by light to chlorophyll in cell of producer
  • here CO2 + water react producing glucose which stores energy within its chemical bonds
  • glucose then converted into carbs, proteins + fats, which are used as energy stores, growth + repair
  • as an organism grows it increases its biomass
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34
Q

what is biomass

A
  • the dry mass of material in living organisms
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35
Q

why is dry mass used for biomass

A
  • because wet mass varies as amount of water in organism varies
    > requires organism to be killed + dried in a kiln
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36
Q

how is energy transferred between organisms - consumers

A
  • consumers eat producers
  • when organism respires, energy stored in food is transferred to production of ATP
  • organism grows + biomass increases
37
Q

what are food chains

A
  • charts showing the flow of energy from one organism to the other
    > shows what an organism eats
38
Q

what is a trophic level

A
  • each step in a a food chain
  • the position of an organism in food chain
39
Q

what is always on the first trophic level

A
  • producers
40
Q

what are the 5 tropic levels

A
  • producer
  • primary consumer
  • secondary consumer
  • tertiary consumer
  • quaternary consumer
41
Q

what is a food web

A
  • series of interconnected food chains showing energy flow through part of an ecosystem
42
Q

why are food webs needed

A
  • food chain are too simple and show only ne organism eating one
  • in most communities animals eat more than one type of organisms + can be eaten by more than one
  • to show this, food webs are illustrated
43
Q

what is a pyramid of number

A
  • a chart showing the number of organisms at each tropic level
  • inverted pyramid
44
Q

what is a pyramid of biomass

A
  • just like pyramid of numbers with each tropic level on top of each other BUT
  • pyramid of biomass takes into the mass of each organism
45
Q

why is pyramid of biomass more accurate than pyramid of numbers

A
  • takes into account the number + size of organisms present
46
Q

why is biomass lost between different trophic levels

A
  • biomass is lost in waste
  • biomass is used to carry out respiration
47
Q

what are some of the ways that biomass is lost

A
  • in waste: undigested material in faeces, excess protein in urine, inedible parts
  • biomass used in respiration: resp produces ATP; muscles use ATP for movement - also used to maintain constant body temp
  • egestion: some parts of organism can’t be eaten - hair + teeth - so removed in faeces
  • excretion: waste products produced by body are lost through excretion > e.g. urea lost in urine
48
Q

how do you calculate the efficiency of biomass transfer

A
  • efficiency of biomass transfer = biomass available after transfer / biomass available before transfer x 100
    = after / before x 100
49
Q

how does the efficiency of biomass transfers affect the number of trophic levels in a biomass pyramid

A
  • the less efficient the transfers, the fewer trophic levels + the fewer organisms in higher trophic levels
50
Q

what is a primary consumer

A
  • an organism that feeds on producers
51
Q

what is a secondary consumer

A
  • an organism that feeds on primary consumers
52
Q

what do plants compete for

A
  • light
  • water
  • CO2
  • minerals
  • space
53
Q

what do animals compete for

A
  • food
  • water
  • breeding partners
  • space (territory)
  • shelter
54
Q

what are decomposers

A
  • microorganisms (bacteria + fungi) that break down/decay dead organisms + waste materials
55
Q

what is decomposition

A
  • process by which dead organisms + waste material are broken down by decomposers
56
Q

what happens through decomposition

A
  • decomposers use nutrients to live + grow
  • excess nutrients are released back into the environment for recycling
57
Q

what are saprophytes

A
  • organisms that feed on dead material
58
Q

what are detritivores

A
  • small animals
59
Q

what is the role of detritivores in decomposition

A
  • they speed up decomposition by breaking organic material into smaller pieces
    > this creates a larger surface area for decomposers to work on
60
Q

how do decomposers release nutrients

A
  • bacteria + fungi release enzymes on the dead remains
  • the enzymes digest the dead matter and make it soluble
  • the soluble products are absorbed by the bacteria / fungus (for growth + as an energy store)
    > many of the bacteria + fungi will be eaten by other organism, resulting in the nutrients being passed on
    > some of the nutrients are released directly into the soil or the environment
61
Q

what factors affect the rate of decomposition

A
  • temperature
  • moisture
  • oxygen levels - aerobic conditions
62
Q

how does temperature affect the rate of decomposition

A
  • most decomposers work best in warm conditions (rate highest at 50 degrees Celsius)
    > this is because decomposers contain enzymes which work best at higher temps
  • low temps: rate of decomposition slow - enzyme controlled reactions are reduced
  • higher temps: enzyme becomes denatured + decomposition stops (often results in death of microorganism)
63
Q

how does moist environments affect the rate of decomposition

A
  • decomposers need water for survival
  • if not enough water is available, the reaction slows down or is prevented
    > rate of decomposition inc in moist conditions
64
Q

how does aerobic conditions affect the rate of decomposition

A
  • oxygen needed for decomposers to respire
    > rate of decomposition inc with more oxygen
  • anaerobic conditions will prevent most forms of decomposition as decomposers can’t survive in this condition
    > some decomposers will respire anaerobically but it transfers less energy, so decomposers will work more slowly
65
Q

how do you calculate the rate of decay

A
  • rate of decay (g/day) = change in mass (g) / time (day)
  • rate = change in mass / time
66
Q

what is nutrient cycling

A
  • the process of material being passed between biotic + abiotic component of an ecosystem
67
Q

describe the nutrient cycle

A
  • plants get nutrients for growth from soil
  • nutrients get passed onto animals when plant is eaten
  • when plants + animals die, decomposers break down their bodies and this releases nutrients back into the environment
68
Q

where does the nutrients released by dead animals + plants go

A
  • many nutrients released into soil, for plants to absorb them
  • some are released into the atmosphere
69
Q

what materials are cycled in an ecosystem

A
  • carbon
  • nitrogen
  • water
70
Q

why is carbon important

A
  • all living things contain carbon
    > used to make: carbohydrates, fats, proteins and DNA
  • carbon present in atmosphere as CO2
    > plants use CO2 during photosynthesis to produce sugars
    > this can be converted to other molecules + can then be transferred to animals along food chain
71
Q

what is the carbon cycle

A
  • the process in which carbon is cycled through the atmosphere, the Earth, plants and animals
72
Q

how is carbon removed from the atmosphere + passed on

A
  • CO2 removed from environment during photosynthesis
    > occurs in green plants, algae, phytoplankton
    > CO2 + water —> glucose + oxygen
  • glucose simple sugar is converted to complex carbs
    > allows plant to grow + develop
  • when animals eat plants, carbon from plant is transferred to animal - can be used to make fats + proteins
73
Q

how is carbon released back into the atmosphere

A
  • respiration: releases CO2
  • decomposition: releases CO2
  • burning fossil fuels: fossil fuels are a store of carbon - when burned CO2 released
    > fossil fuels include: coal, oil, natural gas
74
Q

what can the carbon from dead organisms also forms

A
  • fossil fuels
  • sedimentary rocks e.g. limestones
    > these are long term carbon stores
75
Q

why does the level of atmospheric CO2 vary

A
  • photosynthesis only happens at daytime so CO2 is only removed then
  • respiration is carried out by all living organisms at all times, so CO2 is released at a consistent rate
76
Q

why has atmospheric CO2 concentration increased significantly in recent years

A
  • mainly due to human activities
    > combustion of fossil fuels
    > deforestation
  • inc level of CO2 is contributing to global warming
77
Q

why is nitrogen important

A
  • nitrogen makes up nearly 80% of atmosphere
  • nitrogen used to make amino acids (protein) + DNA + chlorophyll
  • most organisms can’t take nitrogen from air, but use it when it’s in a compound form e.g. nitrate
78
Q

how do plants take in nitrogen

A
  • they take nitrogen through their roots as the mineral nitrate (nitrate dissolved in water so can be taken up)
  • the nitrates are used to make proteins
79
Q

how do animals get nitrogen

A
  • animals eat plants
    > they get their nitrogen as protein which they have to digest + assimilate
    > protein then goes up food chain
80
Q

what happens in the nitrogen cycle when organisms die

A
  • waste material (uneaten pieces of plant, faeces, urine) gets broken down by decomposers
    > and they get turned into ammonium ions in the soil
81
Q

what happens to the ammonium ions in the nitrogen cycle

A
  • ammonium is no use to living things
  • a bacteria called nitrifying bacteria turns ammonium ions into nitrates for the plants
82
Q

what is nitrogen-fixing bacteria

A
  • a bacteria that converts nitrogen from the air into nitrate which is used in soil by plants to take up nitrogen
83
Q

what is nitrifying bacteria

A
  • bacteria which converts ammonium ions from waste / dead remains into nitrates for soil
84
Q

what is denitrifying bacteria

A
  • bacteria which converts nitrates in the soil back into nitrogen which gets releases into the atmosphere
85
Q

how does nitrogen get into the soil in he first place

A
  • nitrogen-fixing bacteria in soil
  • nitrogen-fixing bacteria in root nodules (plant roots)
  • nitrogen reacts with oxygen in air when high temps created by lightning - this dissolves in rainwater + soil gets nitrates from it
  • nitrogen turned into ammonia in Haber process which is then used as fertilisers - fertilisers can be used to enrich soil with nitrates
86
Q

how is water recycled in the water cycle

A
  • sun makes water evaporate from land + sea + transpiration from plants
  • water condenses as clouds
  • water is returned through precipitation
87
Q

what does the water cycle move

A
  • water + nutrients through atmosphere, soil, rivers, lakes and oceans
88
Q

how does the water cycle help

A
  • it bring fresh water to people + animals + plants (organisms) all around the word
  • transports nutrients to diff ecosystems

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