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topic 10 Flashcards

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Biology 101 flashcards
1
Q

10.1 [the nature of ecosystems]

  1. What’s an ecosystem?
  2. Population?
  3. Community?
  4. Niche?
A
  1. Ecosystem: An environment including all the living + non-living factors with which they interact. can be many sizes (eg as small as a rock pool / very large)
  2. Population: Group of organisms of the same species that breed together in the same habitat
  3. Community: A group of populations of different species interacting in the same habitat
  4. Niche: The role of an organism in its community
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2
Q

Biotic v Abiotic factors

Biosphere?
Biomes?

A
  • Biotic - living elements of a habitat that affect ability of organisms to live there (availability of prey, bacteria)
  • Abiotic - non-living elements of a habitat (sunlight, temp, soil pH, rainfall, O2 in water)
  • Biosphere - all the areas of the surface of the earth where living organisms survive
  • Biome - the major ecosystems of the world
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3
Q

Trophic levels?

Different ways it can be represented?

A

Trophic levels

  • describe the position of an organism in a food chain or web
  • +describes its feeding relationship with other organisms

Can be represented by

  • pyramids of numbers
  • biomass (dry)
  • energy
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4
Q

Different trophic levels within a food web

A
  1. Producers - make food (plant + algae photosynthesise using sunlight to make food)
  2. Primary consumers - organisms which eat the producers (herbivores)
  3. Secondary consumers - animals that feed on herbivores (carnivores)
  4. Tertiary consumers - animals that feed on other carnivores
    (top predators, unless there’s a quarternary consumer)
  5. Decomposers - the final trophic level in any feeding relationship which digest dead organic material
    (miroorganisms [bacteria/fungi] that break down remains of animals + plants + return nutrients to soil)
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5
Q

+ / - of
pyramids of numbers
(counting)

as representation of ecosystem structure+ how biomass+energy transferred

A

ADV +

  • easiest to measure

DISADV -

  • least accurate
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6
Q

+ / - of
biomass
(weighing)

as representation of ecosystem structure+ how biomass+energy transferred

A

ADV +

  • More accurate

DISADV -

  • Don’t take into account rate of production of biomass
  • using dry mass = dehydration kills organisms
  • = use wet mass = less accurate
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7
Q

+ / - of
energy levels

as representation of ecosystem structure+ how biomass+energy transferred

A

ADV +

  • Most accurate

DISADV -

  • Hardest to measure
  • = rarely used in practice
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8
Q

Abundance?
Distribution?

Ecological techniques of measuring them?

A

Abundance

  • the relative representation of a species in a particular ecosystem
  • total number of individuals of a species present in a ecosystem relative to other organisms in same habitat

Distribution

  • Where species of organisms are found in the enviornment + how its arranged
  • how spread out the organisms are from eachother

Ecological techniques

  • Quadrat
  • Transect
  • ACFOR scales
  • Percentage cover
  • Individual counts
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9
Q

Unifrom V clumped V random
distribution

A

Uniform distribution

  • resources thinly but evenly spread

Clumped distribution

  • Distributed in groups (eg herds of animals)
  • groups of animals + plants which have specifc resource requirment = clump in areas where they’re found

Random distribution

  • A result of plentiful resources + no antagonism
  • ( eg dandelions in field)
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10
Q

Quadrats

  • individual counts
  • percentage count
A
  • square gridded frames placed at random
  • count the number of individual organisms inside (individual counts)
  • using divided grid, find area covered by the organism (percentage cover)
  • multiple readings = find mean
  • Issue about decisions on whether to include organisms partly covered by quadrat
  • = need to decide before u start if organisms on sides are in / out
  • point quadrat - wooden frame quadrat with holes in it placed and metal pins placed in each hole and count number of organisms which touch each pin
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11
Q

ACFOR scale

A
  • use ACFOR scale to measure abundance of organisms in a quadrat / area
  • used to describe abundancy in area as…

A = abundant
C = common
F = frequent
O = occasional
R = rare

ISSUE

  • it’s subjective. 2 ppl will not come up with same rating
  • No set definition of terms = hom much is ‘common’
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12
Q

Transects

-systemetic sampling method

A
  • line / belt transect which runs across area to be investigated sytemetically
  • stretch line transect between 2 points + record the number of each individual plant/animal that touch the tape
  • Belt transect = 2 tapes laid out + area between them surveyed using quadrats along a line
  • Interrupted belt transect - sample at regular intervals rather than recording a whole belt
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13
Q

Other measures of abundance that can be used

A
  • light traps to attract flying insects
  • capture / recapture techniques for animals that move around
  • beating of branches to collect what falls out
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14
Q

Making comparisons

Aspects of sampling techniques which can be compared..

A
  • transects + random sampling
  • belt + interrupted transects
  • different quadrat sizes
  • types of quadrat
  • individual count + percentage cover
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15
Q

statistical tests to analyse data

Statistical tests can indicate if differences in results (from sampling methods) are significant

  • observer value on table of critical values?
  • null hypothesis?
A
  • observer value on table of critical values = need to look up OV for each test to see which probability value this corresponds with to see if u should accept null hypthesis or not
  • significant = less than 0.05
  • = corresponds to the p < 0.05 level of significance
  • null hypothesis = hypothesis that any differences between data sets are simply due to chance
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16
Q

Statistical test 1

Spearman’s rank correlation coefficient

  • Why use it?
A
  • To measure correlation between two variables
  • (the extent to which changing one variable affects the other variable)
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17
Q

Spearman’s rank correlation coefficient

  • How to do it?
A
  1. State null hypothesis
  2. Give rank to each item in each set of measurements
  3. Find the differences (D) between ranks for each pair of measurements
  4. Add all the differences (squared individually) together + use formula to find correlation coefficient (r)
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18
Q

Explain how Spearman’s rank results are interpreted

A

Find correlation coefficient r between -1 to 1
= size of coefficient indicates how strong correlation is

  • Closer to 1= more positive correlation
  • Closer to -1= more negative correlation
  • Around 0 = no correlation
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19
Q

Deciding whether to accepy null hypothesis or not

A
  1. State the null hypothesis (variables do not correlate)
  2. Calculate ‘r’ coefficient
  3. Decide whether to accept / reject null hypothesis (by comparing it to 0.05 critical value)
  • If more than the critical value at 0.05 = significant = reject null hypothesis = less than 5% due to chance
  • If less than 0.05 = not significant
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20
Q

Statistical test 2

Student’s t-test
- why use it?

A
  • to test to see if there’s a significant difference between the means (averages) of two sets of data
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21
Q

Student’s t-test

  • how to do it?
A
  1. State null hypothesis
  2. Calculate observer value (t) using formula
  3. use a table to see if t is above or below p = 0.05
    for (n1 + n2) - 2 degrees of freedom
    decide whether to accept null hypothesis
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22
Q

explain how t-test results are interpreted

A
  • the t value obtained is compared to a critical value (found in a table) for a particular p value chosen by the researcher
  • Find degrees of freedom (total number of data - 2)
  • find probability (p) value that relates to observer value + degree of freedom
  • if p > 0.05 = difference is significant
  • T value should be higher than the critical value at 0.05 to be significant = reject null hypothesis
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23
Q

10.2 [energy transfer through ecosystem]

energy transfer

  • Gross primary productivity?
  • Net primary productivity?
A
  • Energy is transferred between trophic levels in an ecosystem

Gross primary productivity (GPP)

  • The rate at which producers make organic material / biomass through photosynthesis [using light]
  • units eg: g m2 year1 (grams of biomass pr area yearly)
  • plants use atleast 25% of material they produce for own metabolic needs + respiration
  • rest of material is stored as NPP

Net primary productivity (NPP)

  • The material produced by photosynthesis stored as new plant body tissues
  • NPP of different ecosystems depends on abiotic + biotic factors which affect plant growth
  • biomass/energy in producers which transfers to the primary consumers

NPP = GPP - R (respiration)

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24
Q

How is energy transferred between trophic levels?

A
  • source of energy for all living systems is light from sun = light intensity is limiting factor for ecosystems
  • Only a small amount of the energy available to an organism is transferred to the next trophic level
  • Some is never taken in, some is lost before being transferred
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25
Q

Why is some energy never taken in at each trophic level?

A

● Some parts of food are not eaten
● Some parts of food are indigestible
● Plants can’t use all light energy as some is in the wrong wavelength

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26
Q

Energy losses along a food chain

A
  • some energy lost as undigested + therefore unused material in the faeces
  • much of material is used to drive respiration = exothermic so energy lost to surrounding
  • = heat loss + energy used for movement
  • some of plant material is lost in metabolic waste products such as urea

=

  • only a small amount of chemical store of plant becomes new animal material + therefore part of the energy store of animal
  • the rest is dissipated to the surrounidings = increasing internal energy store of universe
  • process of making new animal biomass is known as secondary production
27
Q

Measure of the effeciency of energy transfer

A
  • similiar energy transfer occurs between animal trophic levels from herbivore to primary to secondary consumers etc up the food chain
  • energy store in biomass of 1 organism compared with energy store that ends up in organism in next trophic level is measure of effeciency of energy transfer
  • effeciency of energy transfer is the proportion of energy in 1 trophic level that is available to the next
  • effeciency of energy transfer is around 10% at each level in food chains
  • but its’s difficult to measure energy transfers
28
Q

Nutrient recycling

A
  • the nutrients needed by organisms to build new body cells are returned to the enviornment as waste or by decomposition
  • microorganisms are important in the recycling of nutrients within an ecosystem
  • plants need inorganic nutrients (CO2/ nitrates) to produce organic molecules
  • transferred between biotic + abiotic factors in nutrient cycle
  • plants take CO2 from air to use in photosynthesis to produce carbohydrates
  • plants take nitrates from soil water to produce amino acids + proteins + nucleotides used to build DNA + RNA
29
Q

why can’t plants use nitrogen in air?

A
  • plants cannot use nitrogen in air as its an inert gas = unreactive
  • only nitrogen in form of nitrates useful for plants from soil water
  • = taken up to make protein = protein passed along food chain
30
Q

decay of nitrogen

A
  • nitrates taken up from soil water by plants
  • used to make proteins = passed down food chains
  • nitrogen passed out through faeces / urea back into soil / when they die = body contains lots of protein
  • decomposers break proteins to form ammonium compounds
  • amounium compounds then oxidised by nitrifying bacteria = convert them to nitrates = reabsorbed by plants
31
Q

Nitrogen cycle

  1. Nitrogen Fixation
  2. Ammonification
  3. Nitrification
  4. Denitrification
A

1. Nitrogen Fixation

  • nitrogen-fixing bacteria in soil convert nitrogen compounds (from animal waste /dead organic matter) into ammonia
  • [ Legumes (plants - peas,beans) have nodules in roots with nitrogen-fixing bacteria - Mutualism = bacteria provide the plant with nitrogen compounds + plant provides the bacteria with carbohydrates ]

2. Ammonification

  • Saprobionts decompose nitrogenous waste into ammonium compounds

3. Nitrification

  • ammonia oxidised by nitrifying bacteria - converted to nitrates + nitrites

4. Denitrification

  • Denitrrifying bacteria break down nitrates (to power production of ATP)
  • producing nitrogen gas as waste product = making nitrogen unavailable for plants = not useful bacteria
32
Q

Bacteria in nitrogen cycle

  1. Nitrogen-fixing bacteria?
  2. Nitrifying bacteria?
  3. Denitrifying bacteria?
A
  1. Nitrogen-fixing bacteria
  • converts nitrogen frm soil into ammonia
  1. Nitrifying bacteria
  • oxidise ammonium compounds to form nitrites + nitrates
  1. Denitrifying bacteria
  • breaks down nitrates to power production of ATP, producng nitrogen gas as waste product
33
Q

Carbon cycle

A
  • CO2 removed from air by photosynthesis of green plants
  • used to make carbohydrates, proteins, fats = make up body of plant = passed through food chain as plants are eaten
  • green plants + animals respire = CO2 released back into environment/air/atmosphere
  • when plants + animals die = their body (which contains carbon) broken down by decomposers = release carbon into atmosphere as CO2 = cycle repeats
  • Combustion - burning of wood.fossil fuels etc - release CO2
34
Q

Carbon sinks

A
  • a reservoir where carbon is removed from atmosphere + ‘locked up’ in organic / inorganic compounds
  • removed from atmosphere through photosynthesis + stored in bodies of plants + animals
  • rocks, fossil fuels, chalk - hold carbon
  • oceans - massive reservoirs of CO2 - contain ALOT of dissolved inorganic carbon
35
Q

Human influence of balance of Carbon cycle?

A

humans use of

  • cars, burning of fossil fuels etc releasing alot more CO2 into atmosphere than before
36
Q

10.3 [changes in ecosystems]

Organisms cause changes to their enviornment = ecosystems develop overtime

Succession?

A
  • The process by which the communities of organisms colonising an area change over time = replaced by more varied + productive communities
37
Q

Primary succession?

A
  • Starts with an empty inorganic surface, such as bare rock / sand dune
  • Occurs when an area previously devoid of life is colonised by communies of organisms
  • eg after eruption of a volcano = led to the formation of a rock surface, then algae,mosses,fungi
  • = these organisms penterate rock surface + break it
  • = these inorganic rock grains start formation of soil
  • = soil allows other species (grass/ferns) to establush root systems
38
Q

Summarise the process of primary succession

A

● Colonisation - species grow that are capable of survivng difficult conditions of bare rock
● Pioneer species able to survive harsh conditions, colonise the area after colonisers made conditions bit better
● They die, decompose + add nutrients to the ground (add humus = organic component of soil)
● add niches/food/habitat for other organisms = tress grow
● Over time, this allows more complex organisms to survive
● = climax community can form when largest plants are able to grow + there’s no further succession

39
Q

Climax communities?

2 types?

A
  • The final stage of succession, where the ecosystem is balanced + stable
  • It is reached when the soil is rich enough to support large trees / shrubs + the environment is no longer changing
  1. Climatic climax communities - Initially thought that a given climate could support only one climax community - idea has been discredited
  2. A Plagioclimax - a stable community where there is human intervention such as grazing, atleast a part is aresult of human intervention
40
Q

Secondary succession

A
  • development of ecosystem from existing soil that’s clear of vegetation
  • occurs after fires + floods / disturbances by humans
  • The re-colonisation of a habitat after a disturbance
  • similiar to stages of primary succession except soil is already developed
41
Q

Biotic = living factors

biotic factors which affect population size

A
  1. Predator-prey relationships
  2. availability of reproductive partners
  3. territory
  4. Parasites + microorganisms
  5. Competition - intra v interspecific
42
Q

Biotic factors

  1. Predator-prey relationships
  2. availability of reproductive partners
A

1. Predator-prey relationships

  • Important for both populations
  • pop size of prey species affected by amount of predation
  • pop size of predators affected by prey availability
  • predator + prey populations oscillate as their numbers affect eachother

2. availability of reproductive partners

  • Availability of finding reproductive partners can increase/decrease population
  • Lack of species in an area = cannot find a mate to reproduce = population falls
43
Q
  1. Territory
  2. Parasites + microorganisms
A

3. territory

  • area held + defended by an animal (or group) from predators
  • necessary so breeding pairs have sufficient resources to raise young
  • can affect abundancy of organisms in habitat = the territory must be big enough to provide resources for a breeding group

4. Parasites + microorganisms

  • parasites + microorganisms that cause disease can affect population sizes
  • diseased animals = weak + cannot reproduce successfully
  • cannot hunt + more likely to get killed
  • parasites feed off living bodies of host + weakening it = can wipe out whole population
44
Q
  1. Intraspecific v Interspecific competition
A

Intraspecific competetion

  • competetion between members of same species for a limited resource
  • = some individuals may not survive / may not reproduce = population growth slows

Interspecific competetion

  • Competetion between different species within a community for the same resource
  • will reduce the abundance of the competing species that’s missing out on resource
45
Q

Abiotic factors = non-living

Abiotic factors which affect population size

A
  • light intensity
  • wind + water currents
  • temperature
  • water availability
  • oxygen availability
  • Edaphic factors (composition of soil - eg pH)
46
Q
  1. light intensity
  2. wind + water currents
A

1. light intensity

  • Affects plant structure + growth (photosynthesis)
  • Indirectly affects consumers = availability of food
  • Affect reproductive patterns
  • Affect circadian rhythms = controls animald physiology + behaviour

2. wind + water currents

  • Affects stability of enviornment
  • Wind affects water loss from body+ cooling
  • Hurricanes destroy habitats
  • water current= organisms have to flow with current, attach to surfaces, or be strong swimmers to survive
47
Q
  1. temperature
  2. water availability
A

3. temperature

  • Affects enzyme controlled reactions
  • Most organisms have a limited range in which they can reproduce successfully
  • Adaptations enabeling them to cope woth specific temp = those wothout adaptations = cannot survive

4. water availability

  • Very low water availabilty (water stress) = organisms will die unless adapted (eg camels)
  • Can cause severe change in habitat
  • affects photosynthesis
48
Q
  1. oxygen availability
  2. Edaphic factors
    (composition of soil - eg pH)
A

5. oxygen availability

  • can be in short supply in water + soil
  • if water cold = O2 dissolves in it = support life
  • if water temp rises = less O2 dissolves in it = affect ssurvival of populations in it
  • O2 in soil for respiration of plant roots
  • if derived of O2 (waterlogged) = plant die

6. Edaphic factors

  • relates to structure of soil - pH
  • Sandy soil = leaches minerals as water passes through quickly + drains quickly
  • Clay = gets waterlogged as difficult to drain + take too long to warm + hard to work
  • Ideal soil is loam which is a mixture of types
49
Q

Density dependent factors

Density independent factors

A

Population size can also be influenced by

density dependent factors:

  • predation, parasitism, food source, space and competition

Density independent factors:

  • climate, weather and natural disasters
50
Q

10.4 [human effects on ecosystems]

How have humans influenced ecosystems?

A

● Increased carbon dioxide and other pollutants causing climate change
● Depleted biological resources (overfishing)
● Destruction of habitats for buildings, farmland, resources

51
Q

climate change

Global warming?

A
  • global temperatures are increasing
  • will lead to permanent change in earth’s climate
  • = sea levels are rising, sea ice is melting, extreme weather conditions more common
52
Q

Evidence for climate change:

A
  • Records of CO2 levels

= increasing levels of CO2 in the atmosphere contribute towards climate change as CO2 is a greenhouse gas + involved in greenhouse effect

  • Temperature records

= enable analysis of changes in temperature
= upwards trend in world temp over years

  • Pollen in peat bogs

= Peat blogs preserve pollen to show how vegetation has changed + what kind of plants were present + compare their CO2 + O2 info/requirments

  • Dendrochronology

= the study of tree rings as the size of tree rings is affected by temperature

  • Ice cores

= reveal perserved of historical CO2 levels trapped in ice

53
Q

Greenhouse effect?

A
  • process by which gases in Earth’s atmosphere absorb + re-radiate the infrared radiation from the sun, which has been reflected from earth’s surface
  • = maintaining temperature at surface of earth which is warm enough for life to exist
  • Enhanced greenhouse effect occurs when there’s too many greenhouse gases (CO2, methane, water vapours) = trap too much infrared radiation = temp rises too much
54
Q

models of future climate change

A
  • data of Co2 + temperature changes can be extrapolated to make predictions
  • which can then be used in models of future climate change
  • limitation: do not include factors such as reduction in emission of greenhouse gases
  • correlation or causation?
55
Q

Impacts of climate change

A
  • changing rainfall paterns + seasonal cycles
  • Changes in distribuon of species – species would move to cooler areas = could potentially lead to the extinction of some species due to competition
  • increased risk of flooding from more ice melting = increased sea levels = can destroy habitats
  • temp has effect on enzyme activity = affects whole organism
  • development of embryos of some reptiles sensitive to temp = temp determines the sex of the crocodile = high temp = more females developing only
56
Q

depletion of biological resources

A
  • over fishing= fish stock in ocean becoming most depleted biological resource = unsustainable fishing
  • too many fished = dont have time to reproduce + replenish population = extinction of some fish species
  • Farming = remove crop before plant die + decompose = break nutrient cylce = soil mineral conc falls
  • Artificial fertilisers replace lost minerals in soil = soil structure overtime can become infertile even if fertilisers used
57
Q

Methods of conserving / protecting resources

issue?

A
  • use wide-mesh nets to release young fish
  • avoiding fishing during breeding seasons
  • imposing fishing quotas (limits)
  • encouraging methods that avoid damaging habitat
  • Increasing awarness about issues + ways to be more sustainable (provide decent living standards now without compromising need of future generations or ecosystems around us)
  • Conflict between needs of humans / growing population / making profit + exploitation of environment
58
Q

How to reduce CO2 levels in the atmosphere to reduce climate change?

A

● Growing plants to use as a fuel as biofuels which are carbon neutral
- CO2 released by burning the fuel is removed from atmosphere by the plants its made from (by photosynthesis)

● Reforestation to increase the rate at which carbon dioxide is removed

59
Q

Endangered + extinction?

Human causes of extinction?

A

Endangered - species facing high risk of becoming extinct
Extinction - permanent loss of all members of a species

Human causes of extinction

  • destroying habitats (deforestation)
  • pollution of seas, rivers, lakes with sewage + chemicals
60
Q

Conservation?
Preservation?

Why have international agreements been introduced?

A
  • Conservation = maintain or increase the biodiversity within a particular habitat by allowing sustainable use of natural resources
  • preservation = maintain the biodiversity levels + the habitat intact by minimising the effects of human activities on the particular habitat

International agreements to promote..

  • conservaton
  • sustainable use of resources
  • avoidance of extinction of species
61
Q

international treaties to support conservation + sustainability

[ CITES ]
Convention on International Trade in Endangered Species of Wild Fauna and Flora

Role of CITES?

A
  • protect endangered animals + plants by regulating trade in living organisms + products made by them
  • limits movements of them (imports + exports)
  • eg elephant tusks / entire groups of organisms (dolphins)
62
Q

Success of CITES in conserving biodiversity + preventing extinction?

A
  • banned international ivory trade = poaching levels fallen = elephant numbers increased in areas
  • bans on trade of any turtle products (meat / shells) = many turtle species brought back from brink of extinction
63
Q

Limitations of CITES

A
  • deals with trade only = doesn’t protect ecosystems / protect breeding areas / threatened habitats
  • many countries not signed up to CITES
  • there are no legal sanctions
  • market is still high in demand for these products
64
Q

human needs V protection of enviornment

How is evidence related to the climate change debate validated + evaluated?

A
  • peer- reviewed - Papers sent to other experts to check for validity = if data + conclusion seem reasonable = results are published in scientific journals
  • publication in scientific journals
  • debated at scientific conferences

= avoids bias + misleading conclusions

bio (alevel) (10 decks)

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