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Biology > topic 7 - ecology > Flashcards

topic 7 - ecology Flashcards

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1
Q

what is an ecosystem?

A

an ecosystem is the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment

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2
Q

what is a habitat?

A

the environment in which an organism lives

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3
Q

what is a population?

A

the total number of organisms of the same species living in the same geographical area

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4
Q

what is a community?

A

the populations of all the different species that live in the same habitat

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5
Q

what are the levels of organisation in an ecosystem?

A
  • individual
  • population
  • community
  • ecosystem
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6
Q

what are the factors that plants may compete for?

A
  • light
  • space
  • water
  • mineral ions from soil
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7
Q

what are the factors that animals may compete for?

A
  • food and water
  • mating partners
  • territory
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8
Q

what is interdependence?

A
  • when within a community, each species depends on other living organisms for food
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9
Q

what is a stable community?

A
  • a community where all the species and environmental factors are in balance so that population sizes remain fairly constant
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10
Q

how does the availability of food affect a community?

A
  • if the availability of food falls, then the number of organisms in that community will also fall
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11
Q

how does the arrival of a new predator affect a community?

A
  • this can cause the population of a prey species to fall
  • a new predator can also affect existing predators for example if they are competing for the same prey
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12
Q

how does the competition of species affect a community?

A
  • if a species is outcompeted then its population can fall so much that numbers are no longer sufficient to breed and the species may become extinct
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13
Q

how do new pathogens affect a community?

A
  • if an infectious disease emerges and then spreads it can wipe out the population of a species
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14
Q

what are biotic factors which can affect a community?

A
  • availability of food
  • new predators arriving
  • new pathogens
  • one species outcompeting another so the numbers are no longer sufficient to breed
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15
Q

what are abiotic factors which can affect a community?

A
  • light intensity
  • temperature
  • moisture levels
  • soil pH and mineral content
  • wind intensity and direction
  • carbon dioxide levels for plants oxygen levels for aquatic animals
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16
Q

how does light intensity affect a community?

A
  • all plants need light to carry out photosynthesis, however, if the light intensity is too low then the rate of photosynthesis falls and plants will grow more slowly
  • this can have a major impact on a community
  • this is because if plants grow more slowly, then animals which feed on plants may not have enough food
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17
Q

how does temperature affect a community?

A
  • if the temperature of an environment changes then this could cause the distribution of species to change
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18
Q

how does water affect a community?

A
  • both plants and animals need water to survive
  • many species are adapted to deal with low levels of water
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19
Q

how do the pH and mineral content of the soil affect a community?

A
  • many plants cannot grow on soil which is too acidic or too alkaline
  • plants also need certain minerals in the soil e.g nitrate which is used to make amino acids for proteins
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20
Q

how do the wind intensity and direction affect a community?

A
  • strong winds blowing inland from the sea can cause plants to lose water
  • so plants growing in sand dunes are often adapted to reduce water loss
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21
Q

how do carbon dioxide and oxygen affect a community?

A
  • carbon dioxide is needed for plants to photosynthesise and if carbon dioxide levels fall then the rate of photosynthesis can also decrease
  • oxygen is needed for aerobic respiration. The level of oxygen in the air stays fairly constant.
  • However, the level of dissolved oxygen in water can fall e.g. on hot days. This can be harmful to aquatic organisms such as fish
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22
Q

what are adaptations?

A

features that enable organism to survive in their living environment

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23
Q

what are extremophiles?

A

organisms living in extreme environments

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24
Q

what are 3 examples of extreme living environments?

A
  • high temperature
  • high pressure
  • high salt concentration
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25
Q

where can extremophile bacteria be found?

A

in deep sea vents

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26
Q

what do food chains show?

A
  • food chains show the feeding relationships of different organisms and the flow of energy between the organisms
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27
Q

describe a simple food chain

A

producer -> primary consumer -> secondary consumer -> tertiary consumer

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28
Q

why are producers important in food chains?

A
  • they synthesise complex molecules
  • the source of all biomass
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29
Q

what is biomass?

A
  • the total mass of living material
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30
Q

what is random sampling?

A
  • random sampling is used to compare the numbers of organisms in different areas
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31
Q

what is a quadrat?

A
  • a wooden or plastic square
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32
Q

how do you use a quadrat?

A
  • to use a quadrat, we place it on the ground and then count the number of organisms inside the quadrat
  • this technique can be used to sample plants or slow-moving animals
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33
Q

how do you calculate the total population size of a species in an area?

A

total population size = total area/area sampled x number of organisms of that species counted in sample

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34
Q

why is sampling along a transect used?

A
  • sampling along a transect is used to investigate whether the number of species changes as we move across a habitat
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35
Q

what is a transect?

A
  • a transect is simply a line such as a tape measure or a piece of rope
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36
Q

how do you use a transect?

A
  • place the transect so it runs across the habitat
  • use a quadrat to count the number of organisms at intervals on the transect
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37
Q

how to measure random sampling?

A
  • use a quadrat 0.5m by 0.5m
  • place two tape measures at right angles
  • these tape measures should be 20m in length
  • we then need two bags and each bag contains the numbers 1 to 20
  • the first student removes a number from the bag -> e.g. 8
  • this student now moves to the 8m point on one of the tape measures
  • the second student now selects a number from their bag and moves to that point on the other tape measure - e.g. 12
  • now the third student places a quadrant on the ground at the 8m by 12m point
  • the students now record the number of daisies in the first quadrat
  • the students then repeat this process nine more times
  • then calculate the total population size
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38
Q

how does carbon enter the carbon cycle?

A
  • by photosynthesis
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39
Q

how does the carbon cycle work?

A
  • plants and algae take in carbon dioxide from the atmosphere in photosynthesis
  • the carbon is used to make carbohydrates, fats and proteins which make up the cells of plants and algae
  • plants and algae respire so some of the carbon is released back into the atmosphere as carbon dioxide
  • plants and algae can be eaten by animals and then these animals can be eaten by other animals
  • at this point, the carbon in the plants becomes part of the carbohydrates, fats and proteins in the cells of animals
  • just like plants, animals respire, so some of the carbon is released back into the atmosphere as carbon dioxide
  • animals release waste products such as faeces and eventually all animals and plants die
  • now we have carbon in waste products and dead remains
  • the waste product and dead remains are then broken down by decomposing microorganisms e.g. bacteria and fungi
  • and when decomposers carry out respiration, the carbon in the waste and dead remains are returned to the atmosphere as carbon dioxide
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40
Q

why are decomposers important?

A
  • they cycle materials through an ecosystem
  • as well as returning carbon to the atmosphere as carbon dioxide, they also release mineral ions to the soil
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41
Q

what happens if decomposers cannot function effectively?

A
  • the carbon in dead remains can slowly be converted to fossil fuels
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42
Q

how does the water cycle work?

A
  • energy from the sun causes the water to evaporate from the surface of the sea
  • the water vapour now travels into the air and cools down
  • when it cools, the water vapour condenses to form clouds
  • the water in clouds then falls to the ground as precipitation
  • all forms of precipitation contain fresh water
  • once the water hits the ground, some of it evaporates back into the atmosphere as water vapour
  • some of the water passes through rocks and forms aquifers
  • and a lot of the water from rivers or streams
  • the water in rivers and streams eventually drains back into the sea
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43
Q

how do living organisms play a role in the water cycle?

A
  • plants take up water in their roots
  • this water moves up the plant in the xylem and passes out of the leaves through stomata as water vapour (transpiration)
  • animals take in water from drinking and eating, they then release water in their urine, in their faces and when they exhale
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44
Q

what is meant by decomposition?

A

the breakdown of dead materials into simpler organic matter

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45
Q

how do decomposers break down dead matter?

A

decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules

46
Q

what are the two types of decomposition?

A
  • aerobic decomposition
  • anaerobic decomposition
47
Q

what factors affect the rate of decomposition?

A
  • oxygen availability
  • temperature
  • water content
48
Q

why is oxygen required for decomposition?

A
  • most decomposers require oxygen for aerobic respiration
49
Q

how does the availability of oxygen affect the rate of decomposition?

A
  • as oxygen levels increase, the rate of decomposition increases
  • as oxygen levels decrease, the rate of decomposition decreases
50
Q

why can decomposition still occur in the absence of oxygen?

A
  • some decomposers respire anaerobically
  • however, the rate of decomposition is slower as anaerobic respiration produces less energy
51
Q

how does soil water content affect the rate of decomposition?

A

decomposers require water to survive
- in moist conditions the rate of decomposition is high
- in waterlogged soils there is little oxygen for respiration so the rate of decomposition decreases

52
Q

why does decomposition require water?

A
  • water is required for the secretion of enzymes and absorption of dissolved molecules
53
Q

how does temperature affect the rate of decomposition?

A
  • the optimum temperature at 50° C
  • lower temperatures, enzymes work too slowly, rate decreases
  • high temperatures, enzyme denature, decomposition stops
54
Q

how is the rate of change calculated when considering the decay of biological material?

A

rate of change = change in value/ change in time

55
Q

what is compost?

A
  • the nutrient-rich product of the rapid decay of waste biological material in optimum conditions set by gardeners and farmers
56
Q

how is compost used?

A
  • used as natural fertiliser to promote growth of crops or garden plants
57
Q

how do biogas generators work?

A
  • biogas generators provide methane gas for fuel through anaerobic decomposing that occurs in animal waste
58
Q

how do environmental conditions affect communities?

A
  • environmental conditions e.g. temperature, soil pH, and light intensity affect the abundance and distribution of organisms within communities
  • e.g. rising global temperatures have been linked to the extinction of frog species
59
Q

how can different temperatures be bad for certain communities?

A
  • if the temperature is too low, growth will be slower as organisms will use more energy to stay warm
  • if the temperature is too high, organisms can die and water will become limited as evaporation increases
60
Q

how can changes in water levels affect ecosystems?

A
  • animals may have to migrate to find water
  • melting ice caps may destroy the habitats of some animals
61
Q

how can atmospheric gases affect ecosystems?

A
  • some organisms cannot survive when certain gases are present
  • polluted water can cause illness to animals that drink it
62
Q

what detrimental impacts can sulfur dioxide have on the environment?

A
  • formed when fossil fuels containing impurities are burnt
  • sulfur dioxide can dissolve in water to form acid rain which can erode buildings and pollute water sources
63
Q

what detrimental impacts can carbon monoxide have on the environment?

A
  • carbon monoxide is formed from the incomplete combustion of fossil fuels
  • carbon monoxide binds irreversibly to haemoglobin which prevents it from carrying oxygen
  • too much exposure can cause unconsciousness and death
64
Q

what are 5 greenhouse gases?

A
  • water vapour
  • carbon dioxide
  • nitrous oxide
  • methane
  • CFCs
65
Q

what are 3 human activities that contribute to greenhouse gases?

A
  • burning fossil fuels
  • deforestation
  • large scale livestock farming
66
Q

how do greenhouse gases lead to global warming?

A
  • green house gases allow heat from the sun to enter the atmosphere
  • the gases act as a ‘blanket’ and trap the heat in the atmosphere
67
Q

what are 3 negative consequences of global warming?

A
  • sea level rise caused by melting icebergs
  • disrupted farming and agriculture
  • increased spread of diseases in warmer climates
68
Q

what is biodiversity?

A

the variety of the different species on earth or within an ecosystem

69
Q

what is the importance of biodiversity?

A
  • to maintain the stability of an ecosystem
70
Q

how does biodiversity ensure the stability of the ecosystem?

A
  • it reduces the dependence on particular species for resources, so that even if one species is removed other species can still survive
71
Q

why has humans’ consumption of resources and water production increased?

A
  • a rapid rise in the human population
  • increase in the standard of living
72
Q

where does pollution occur?

A
  • air
  • land
  • water
73
Q

what are examples of water pollutants?

A
  • sewage
  • fertiliser
  • chemicals
74
Q

how does eutrophication occur?

A
  • fertiliser from farms pollute the water, causing excessive algae growth, depleting the oxygen in the water, causing other plants and animals to die
  • dead plants are decomposed by bacteria and the oxygen level decreases further
75
Q

what human activities reduce the land available for animals and plants?

A
  • building
  • farming
  • quarrying
  • disposing of waste
76
Q

why have PEAT bogs been destroyed?

A
  • to produce compost to increase food production
77
Q

why does the contribution of PEAT bogs greatly contribute to the greenhouse effect?

A
  • PEAT bogs are stores of carbon and burning them releases a large volume of carbon dioxide into the atmosphere
78
Q

why have large-scale deforestation activities occurred?

A
  • to provide land for cattle or rice fields
  • to grow crops to produce biofuels
79
Q

what is the greenhouse effect?

A
  • greenhouse gases trap energy from the sun as heat in the atmosphere, keeping the temperature on earth suitable for life
80
Q

what is causing global warming?

A
  • the increase in levels of greenhouse gases causing the temperature on earth to increase
81
Q

what are the harmful effects of deforestation?

A
  • the destruction of many animals’ habitats
  • releases large amounts of greenhouse gases
82
Q

what are the consequences of global warming?

A
  • rising sea levels
  • melting polar ice caps
  • changing weather patterns
  • migration of animals to find suitable habitats
  • tropical diseases becoming more common
  • extinction of species
83
Q

what is taken to maintain biodiversity?

A
  • breeding programmes for endangered species
  • protection and rebuilding habitats
  • replanting field margins and hedgerows
  • reduce deforestation
  • reduce carbon dioxide emissions
    -recycling rather than disposing in landfills
84
Q

what is the purpose of replanting hedgerows and field margins?

A
  • there is higher biodiversity in the margins than the fields that they surround
85
Q

what are trophic levels?

A
  • the stages in a food chain
86
Q

what is trophic level 1?

A
  • plants and algae which make their own food (through photosynthesis) - called producers
87
Q

what is trophic level 2?

A

herbivores which eat producers - called primary consumers

88
Q

what is trophic level 3?

A
  • carnivores that eat herbivores - called secondary consumers
89
Q

what is trophic level 4?

A

carnivores that eat other carnivores - called tertiary consumers

90
Q

what is an apex predator?

A

a carnivore with no predators

91
Q

how do decomposers break down dead matter?

A
  • decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules
  • soluble small food molecules then diffuse into the microorganisms
92
Q

what is biomass?

A
  • the dry mass of all of the living organisms in an area
93
Q

why is dry mass used for biomass?

A
  • because the wet mass varies as the volume of water in the organism varies
94
Q

how do you calculate the efficiency of biomass transfer?

A

efficiency = (energy transferred / total energy available) x 100

95
Q

what percentage of the incident energy from light for photosynthesis do producers transfer?

A

1%

96
Q

what percentage of the biomass from one trophic level is transferred to the level above it in feeding?

A

approximately 10%

97
Q

why are biomass transfers not 100% efficient?

A

energy is lost through:
- egestion (removal of faeces)
- excretion (removal of waste products e.g. urine containing urea and water)
- respiration (loss of carbon dioxide and water) in which large amounts of glucose are used
- the production of inedible bones and shells

98
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 and the fewer organisms in higher trophic levels
99
Q

what is a biomass pyramid?

A
  • a pyramid that shows the total dry mass of organisms at each trophic level
100
Q

what is food security?

A
  • having enough food to be able to feed a population
101
Q

what are the biological factors threatening food security?

A
  • rising birth rates
  • changing diets in developed countries -> food is transported around the world
  • new pests and pathogens
  • environmental changes affecting food production
  • increased cost of agriculture
  • armed conflicts
102
Q

how does intensive farming increase the production of animals?

A
  • feed animals high-protein foods to increase growth
  • reduce their energy loss to the environment by limiting movement or regulating their surrounding temperature
  • feed animals antibiotics to prevent diseases
103
Q

what are the advantages of intensive farming?

A
  • higher yield of food
  • more efficient
  • allows easier quality control
104
Q

what are the disadvantages of intensive farming?

A
  • may lead to antibiotic resistance
  • cost is high
  • ethical objections
  • biodiversity may be reduced
105
Q

how can fish stocks be conserved?

A
  • control the size of gaps in fishing nets to prevent juvenile fish from being killed before reaching reproductive maturity
  • introduce fishing quotas
106
Q

what is a transgenic organism?

A
  • an organism that has been genetically modified to contain genetic material from another source
107
Q

what is an example of a genetically modified food?

A

golden rice

108
Q

why might crops be genetically modified?

A
  • to improve the nutritional value
  • to be pest resistant
  • to be pesticide resistant
109
Q

what are the advantages of golden rice?

A
  • it contains additional beta-carotene which can be converted to vitamin A in the body, supplementing people who do not obtain enough Vitamin A in their diet to prevent night blindness from forming
110
Q

what is mycoprotein?

A

a protein-rich substance used to make meat substitute food for vegetarians and vegans

111
Q

how is mycoprotein produced?

A
  • Fusarium, a fungus, is grown on glucose syrup, in aerobic conditions and the biomass is harvested and purified to get the mycoprotein

Biology (7 decks)

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