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Alevel Biology > 6.5 > Flashcards

6.5 Flashcards

1
Q

what is an ecosystem

A

any group of living and non-living things and the interrelationships between them, thye can be on large scale (african grassland), medium scale (playing field) or smaller scale (rock pool or laqrge tree)

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2
Q

what are 3 components to an ecosystem

A

habitat, population, community

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3
Q

what is a habitat

A

place where organism lives

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4
Q

what is population

A

all of the organisms of 1 species, who live in the same place at same time and who can breed together

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5
Q

what is community

A

all the populations of different species, who live in same place at same time, and who can interact w each other

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6
Q

what is a niche in terms of ecosystems

A

the role if each species in an ecosystem

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7
Q

Why is it hard to define niches specifically

A

esch organism interacts with both living and non-living things

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8
Q

what may a description of a niche include

A

how and what it feeds on, what it excretes, how it reproduces

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9
Q

can 2 species occupy the exact same niche in the same ecosystyem

A

no, 1 would out compete the other

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10
Q

what are biotic factors effecting ecosystems

A

producers, consumers, decomposers

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11
Q

what are producers

A

plants (and some photosynthetic bacteria) which supply chemical energy to all other organisms

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12
Q

what are consumers

A

primary consumers are herbivores which feed on plants, these can be eaten by carnivorous secondary consumers which can be eaten by carnivourous tertiary consumers

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13
Q

what are decomposers

A

decomposers (bacteria, fungi and some animals) feed on waste material or dead organisms

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14
Q

how do biotic facotrs effect an ecosystem

A

as these components of ecosystem require their own source of materials and energy they can effect other organisms’ food supply, they can also be responsible for predation asnd disease

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15
Q

what are abitotic factors in ecosystems + examples

A

effects of non-living components on an ecosystem: pH, relative humidity, temperature and polluatnt concentration

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16
Q

How do abitoic facotrs vary

A

they can vary in space and time

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17
Q

give an example of how abiotic facotrs can be effected by biotic factors

A

in rainforest, forest canopy infulences temp and hunidity of ecosystenm

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18
Q

What would a graph looking into the intensity of abotic facotrs and species peformance look like

A

bell shaped curve, at extreme values species may perform better, worse or even die, but every species for every abiotic factor has an optimum level and extremes on both ends can be lethal

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19
Q

what is an example of an abitoic factor only being lethal at 1 extreme and what would a graph for this look like

A

pollutant concentration only lethal at extreme high, extreme low will not effect species, so graph would be a straight line and then a rapid decline when concentration too high

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20
Q

why are ecosystems refered to as dynamic

A

as they change, non-living elements change and living elements grow and die, with populations of certain species rising and falling

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21
Q

why are ecosystems dynamic either very slightly or very noticeably

A

as living things in an ecosystem interact with each other and their physical environment, an small change in 1 can effect the other

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22
Q

what is an example of how ecosystems are dynamic

A

id predtor population size goes up, prey population will decrease as more eaten more quickly

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23
Q

what are the 3 changes to ecosystems that affect population size

A

cyclic changes, directional changes, erratic changes

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24
Q

what is a cyclic change

A

these changes repeat themselves in a rhythm, e.g. movement of tides. Way in which predator and prey species flucuate is cyclic

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25
Q

what is a directional change

A

non cyclic, go in 1 direction and tend to last longer than the organsisms within the ecosystem. Within this change, particular variables continue to increase or decrease. e.g. errosion of coastline

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26
Q

what is a erratic change

A

have no rhythm and no constant direction. e.g. effects of lightening or huurricanes

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27
Q

what is an example of how living things respond to changes in ecosystem

A

small mammals hibernate rhythmically to avoid cold temps in winter

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28
Q

what is constantly being recycled in ecosystems, give examples and what is not recycled

A

materials, e.g. nutrient cycles like nitrogen and carbon cycle, energy is not recycled but flows through the ecosystem

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29
Q

All living things need energy and materials, what do plants use it for

A

energy is captured by plants in photosynthesis to produce organic molecules like glucose from water and carbon dioxide, this energy is release from glucose during respiration, products of photosynthesis are used immediately for respiration and are also incorporated into tissues and organs (cellulose for cell walls). Mineral ions are absorbed through plants roots

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30
Q

what is a plants biomass made up of

A

organic components like glucose molecules and inorganic components like mineral ions (not water).

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31
Q

what happens when a plant is eaten by primary consumer

A

its biomass is consumed and when secondary consumer eats primiary consumer it will consume its biomass and so on

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32
Q

what is a trophic level

A

each level of the food chain

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33
Q

What does tracking how biomass changes in a food chain help

A

us to track movement of materials and energy through food chain, we do that for one food chain or whole food web in an ecosystem

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34
Q

whar happens to biomass at each new trophic level

A

some biomass is lost from food chain and therefire unavailable to organism at next trophic level

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35
Q

How is some biomass lost at each tropic level (1)

A

living organisms need energy to carry out life processes, respiration releases energy from organic molecules like glucose. Some of this energy is eventually converted to heat and materials are lost in carbon dioxide and water

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36
Q

How is some biomass lost at each tropic level (2)

A

biomass also lost from a food chain in dead organisms and waste materials which is then only avaliable to decomposers like fungi and bacteria, this waste material also includes parts of animals and plants that can’t be digested by consumers like bones and hair

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37
Q

what does the loss of biomass mean as trophic levels increase

A

biomass is less at higher level of food chain, when organisms in food chain are about same size, means there will be fewer consumers at higher levels

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38
Q

what did ecologists draw to show the loss of biomass higher up food chain

A

a pyramid of numbers, area of each bar in pyramid is proportional to number of individuals, as an aproximation for total biomass at that level, pyrimids can be drawn for individual food chains or whole ecosyste

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39
Q

does pyramid of numbers always work

A

no, counting number of organisms doesn’t always provide an accurate picture of how much biomass exists at each level

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40
Q

what is better than a pyramid of numbers

A

pyramid of biomass, where area of each bar is proportional to dry mass of all organisms at that trophic level

41
Q

how is pyramid of biomass calculated

A

collect all organisms and puts them in oven at 80degreesC until all water in them has been evaporated, check this by periodically finding mass of the organisms. Once mass stops reducing they can be certain all water removed.

42
Q

what is an issue with calculating biomass by removing water from all organisms

A

it is very destrucitve to an ecossytem

43
Q

what is a less destructive way of calculating biomass

A

calculate wet mass and then calcuklate dry mass from this based on reviously published data

44
Q

how do you calculate efficiency of biomass transfer between trophic levels

A

ecological efficiency=(biomass at higher trophic level/biomass at lower tropic level) x 100

45
Q

what is a measure of somethings productivity

A

the rate at which energy passes through each trophic level in food chain

46
Q

what is gross primary productivity

A

rate at which plants convert light energy into chemical energy by photosynthesis, even at start of food chain this is inefficient.

47
Q

why is gross primary productivity inefficient even at start of food chain

A

as photosynthesis produces glucose, entry of biomass into food chain is also inefficient, in optimal conditions only 40% of light energy from sun enters light reaction of photosynthesis and only half of this involved in glucose production, only 2/3 of this glucose is then used for production of starch, cellulose, lipids and proteins, contributing to growth, rest is respired, so only a small portion of energy from the sun remains in the food chain

48
Q

what is net primary productivity

A

amount of energy from sun that remians in the food chain

49
Q

how can humans increase amount of biomass incorporated into plants

A

manipulating environmental factors, humans make energy conservation more efficient, reduce energy loss and increase amount of biomass incorporated into plants

50
Q

what is 1 limiting facotr of photosynthesis and what does this mean for production of biomass

A

light levels limit rate pf photosynthesis which also limits production of biomass, some crops planted early to provide longer growing season to harvest more light and others grown under light banks

51
Q

how does creating drought resistant plants increase primary productivity

A

water is reactant in photosynthesis when glucose is produced so drought resistant crops have been bred in North Africa

52
Q

how does growing plants in greenhouse improve primary productivity

A

provides warmer temperature, increases rate of photosynthesis and increases rate of production of biomass, planting field crops early to provide a longer growing season helps avoid impact of temp on final yeild too

53
Q

how have humans overcome lack of avaliabkle nutrients which slows ratre of production of biomass through photosyntheis

A

crop rotation helps, grow different crop on each field on rotational cycle stops soild reduction of inorganic ions like nitrate

54
Q

how have humans overcome pest like insect removing biomass from food chain and lowering yield

A

spraying pesticides or bred plants to be pest resistant

55
Q

how have humans overcome fungual disease in plants which reduces biomass

A

fungal infections casn cause damage to roots, xylem, phloem, flowers and fruit. farmers can spray fungiicides or genetically modified or bred to be reisstant to some fugal infections

56
Q

how have humans overcome competition from weeds for light, water and nutrients which decrease NPP

A

use herbiicdes to kill weeds

57
Q

how is secondary producticity inefficient without human manipulation

A

transfer of biomass between trophic levels is insufficient, primary consumers dont make full use of plants biomass (not every part of plant eaten but it dies), and when food is digested and absorped much is respired with only small amount leading to increased biomass and being avaliable to next consumer in food chain

58
Q

what are ways humans can manipulate energy transfer (secondary productivity (1 and 2/4)

A

young animals invests a larger proportion of its energy into growht than an adult, harvesting animals just before adulthood minimises loss of enrgy from food chain, 2. selective breeding used to produce improved animaln breeds with faster growth rates, increased egg and milk production

59
Q

what are ways humans can manipulate energy transfer (secondary productivity (3 and 4/4)

A

animals may be treated with antibiotics to avoid unnecessary loss of energy to oathogens and parasites 4. mammals and birds waste energy by grazing, zero grazing reduces this by directly feeding cattle maximal energy allocated to mulch by stopping animals moving and this also maintains a constant temp

60
Q

what are welfare issues with modern farming practices

A

animals welfare, fine balance between need for efficient food prodution and modern farming breaching animals welfare

61
Q

what are decomposers

A

things that break down dead and waste organic materials, e.g baceria and fungi are decomposers

62
Q

why are decomposers decribed as saprotrophs

A

the feed saprotrophically, off other materials

63
Q

what are the 3 steps in saprotrophic decomposition

A
  1. saprotrophs screte enzymes onto dead and waste material 2. enzymes digest material into small molecules which are then absorbed into saprotrophs body 3. having been absorbed, molecules are stored or respired to release energy
64
Q

what would happen if bacteria and fungi didn’t break down dead organisms

A

energy and valuable nutrients would remian trapped within dead organisms, by digesting dead and waste material, microorganisms obtain supply of energy to stay alive and tapped nutrients are recycled

65
Q

what do living things need nitrogen for

A

making proteins and nucleic acids

66
Q

what is baceria involved in in recycling nitrogen

A

ammonification, nitorgen fixation, nitrification, denitrification

67
Q

can plants use nitrogen gas directly

A

no, even though it is so abundant it is unreactive, instead plants need fixed nitrogen like ammonium ions or nitrate ions

68
Q

how is some nitrogen fixed

A

when lightening strikes or in haber process of making fertiliser

69
Q

how is most nitrogen fixed

A

nitrogen fixing bacteria

70
Q

how does nitrogen-fixing bacteria work

A

azotobacter live freely in soil adn fix nitrogen gas which is in air within the soil, using it tp make amino acids. nitorgen fixing bacteria have a mutualisitc relationship woth plamnt (bacteria provides plant with fixed nitrogen adn recieves carbon compounds like glucose in return

71
Q

how are ammonium ions released

A

through ammonification by bacteria involved in putrefactionof proteins found in dead and waste organic matter, rather than gettin their energy from sunlight, some chemoautotrophic bacteria in soil obtain it by oxidising ammounium ions to nitrates whilst others obtain it by oxidising nitries to nitrates, called nitrification

72
Q

what does it mean for ammonification and nitrification thatoxidation requires oxygen

A

these reactions only happen in well-aerated soils, nitrates can be absorbed from soil by plants and used to make nucleotide bases and amino acids

73
Q

what is dentrification

A

other bacteria convert nitrates back to nitrogen gas, when bacteria involved are growing inder anaerobic conditions like in waterlogged soils, they use nitrates as a source of oxygen for their respiration and produce nitrogen gas and nitrous oxide

74
Q

how is carbon similar to nitrogen

A

they are both cycled through biotic and abiotic components of an ecosystem

75
Q

what is carbon cycle driven by

A

processes of respiration and photosynthesis, with carbon dioxide being main vehicle for cycling carbon between biotic and abiotic components of the cycle. animals, plants and microorganisms respire to release carbon dioxide, microorganisms esp important in decomposition of dead organisms and waste

76
Q

what is the difference in terrestrial plants and aquatic plants use of carbon

A

t=use gaseous carbon dioxide in photosynthesis a=used dissolved carbonates

77
Q

how does the carbon cycke work

A

carbon is exchanged between air and water when carbon dioxide dissolves in water and then reacts to form carbonic acid, carbon also enters rivers and lakes from weathering of limestone and chalk in form of hydrogen carbonate. Combustion of fossil fuels has increased across last century, so balance of carbon cycle has changed and atmospheric carbon dioxide levels are higher, this change is responsible for global warming.

78
Q

what is succession

A

any change in community of organisms can change their habitat and this can change make-up of community. A gradual directional change in a community overtime is succession

79
Q

What is island of Surtsey in Iceland formed from volcanic eruption an example of

A

primary succession, had bare ground and now home to a community of plants

80
Q

what are 3 stages to primary succession

A
  1. algae and lichens begin to live on bare rock (pioneer community), 2. erosion of rock and a build-up of dead and rotting organic material produce enough soil for larger plants like mosses and ferns to grow which replace or succeed algae and lichens 3. larger plants succeed these small plants until a final, stable community is reached (climax community), e.g. woodland community
81
Q

what is secondary succession

A

takes place on previously colonised but disturbed or damaged habitat (not always starting from bare ground)

82
Q

how do sand dunes show all the stages of succession

A

sea deposits sand on beach, sand nearest sea is deposited more recently than further away meaning sand just above high water mark is at start of process of succession whereas sand much further away already hosts its climax community

83
Q

what is stage 1 of succession in sand dunes

A

pioneer species like sea rocket colonise the sand just above high water mark, these can tolerate being sprayed with salty water, lack of fresh water and unstable sand

84
Q

what is stage 2 of succession in sand dunes

A

wind-blown sand builds up around the base of these plants, forming a mini sand dune, as plants die and decay, nutrients accumulate in this mini dune, as dune gets bigger, plants like sea sandwort and sea couch grass colonise it. As sea couch grass had underground stems it stabalises the sand

85
Q

what is stage 3 of succession in sand dunes

A

with more stability and accumulation of more nutrients, plants like sea spurge and marram grass strat to grow, Marram grass is special: its shoots trap wind-blown sand and the sand accumulates the shoots grow taller to stay above the growing dune, trapping more sand in the process

86
Q

what is stage 4 of succession in sand dunes

A

as sand dune and nutrients build up, other plants colonise the sand. Many are leguminous, like hare’s foot clover and bird’s foot trefoil which convert nitrogen to nitrate. With nitrate available, more species colonise the dunes, like sand fescue and viper’s bugloss, which stablisies them further

87
Q

why is it difficult to work out if some climates have reached climax community

A

landscapes can be heavily influenced by agriculture, esp in UK

88
Q

what is deflective succession

A

when succession is stropped or interfered with, the sub-climax community as a result is called a plagioclimax

89
Q

what is selected succession example

A

cutting grass on a golf course keeps land at one stage in succession, if grass wasn’t cut for many years, succession would continue and climax community could be reached (e.g. a woodland)

90
Q

what are ways succession can be deflected

A

grazing, burning, fertiliser, herbicides, exposure to excessive wind or human activity

91
Q

what is sampling

A

selecting a few samples from a habitat and studying them carefully to get a general idea of the whole habitat

92
Q

what is the 2 types of data you can collect using a quadratic

A

presence/absence of species (distribution), number of individuals (abundance) of each species - either estimated (%cover) or counted

93
Q

how is estimating made more accurate when using quadrat

A

by using a point frame

94
Q

what are the 2 most unbiased ways to sample a habitat

A

randomly position quadrats using random number generator and coordinates of the habitat or take samples at regular distance across habitat (systematic sampling)

95
Q

how do you know how many quadrates to sample

A

do pilot study, take random sample from across habitat, making a cumulative frequency table, plot cumulative frequency against quadrant number, the point where curve levels off tells you how many quadrats to use

96
Q

equation for population size of a species after sampling

A

mean number of individuals of species in each quadrat/fraction of total habitat area covered by a single quadrat

97
Q

what are the 2 approaches to using a transect

A

line transect- at regular intervals make not of what species touch the tape, belt transect- at regular intervals place quadrant next to the line (interrupted belt transect) or place quadrant next to line moving along line after looking at each quadrant (continuous belt transect)

98
Q

how would you plot data from transects

A

on a kite diagram

Alevel Biology (25 decks)

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