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OCR AS/A Level Biology Context > module 6.3.2: populations and sustainablility > Flashcards

module 6.3.2: populations and sustainablility Flashcards

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1
Q

what is the carrying capacity

A

the maximum stable population size of a species that an ecosystem can support

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2
Q

every individual within a species population has the potential to reproduce and have offspring which contribute to population growth. what does this ensure

A

the population size of each species is limited at some point (i.e. the carrying capacity of that species is reached)
- this is why no single species has a population size that dominates all other species populations on Earth, with the possible exception of humans

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3
Q

what is environmental resistance

A

the combined effects of limiting factors that prevent the further increase of a population

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4
Q

what are some examples of abiotic factors that act as limiting factors of population size

A

light availability
water supply
water mineral content
temperature
amount of space available
soil pH

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5
Q

what happens to a population of mammal if the temperature of their surroundings in significantly higher or lower than optimum. what does this result in

A

individuals will have to use up a significant amount of energy to maintain their optimum body temp (via homeostasis)
- as each individual now has less energy available for growth and reproduction, fewer individuals reach reproductive age and successfully reproduce, meaning that population growth is limited

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6
Q

what are 3 groups of the biotic factors affecting population size

A

interspecific competition
intraspecific competition
predation

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7
Q

what is interspecific competition

A

competition for resources between individuals from different species

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8
Q

what is an example of interspecific competition

A

red squirrels and grey squirrels in the UK compete for the same habitat, nesting sites and food resources

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9
Q

what can happen as a result of competition between species

A

the sizes of both populations are limited
- this can occur as each species has access to fewer resources and therefore less chance of survival and reproduction

competition between species can lead to a decrease in the population size of one of the species and an increase in the population size of the other
- this can occur if one species is able to out-compete the other for resources and therefore has a greater chance of surviving and reproducing

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10
Q

explain 2 factors that limit the stable population size

A
  • interactions between one population and another (of the same species) will limit the size of those populations through intraspecific interactions
    • interactions between one species and another can also limit the size of populations through interspecific interactions such as competition and predation
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11
Q

what is intraspecific competition

A

when individuals from the same species compete for the same resources

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12
Q

explain an example of intraspecific competition

A

when resources are plentiful, the population of grey squirrels increases
- as the population increases, however, there are more individuals competing for these resources (e.g. food and shelter)
- at some point, the resources become limiting and the population can no longer grow in size - the carrying capacity has been reached

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13
Q

explain an example of interspecific competition

A

between the grey squirrel (Sciurus carolinensis) and the red squirrel (Sciurus vulgaris)
- the introduction of the grey squirrel into the southern UK caused the native red squirrel to be outcompeted for food and shelter
- the grey squirrel also carries a disease, parapoxvirus, that is harmless to itself but can be fatal to the red squirrel

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14
Q

what are the conservation efforts in northern England and Scotland that have slowed down the spread of grey squirrel

A

protecting the red squirrels’ habitats and food
giving the red squirrel legal protection
reintroducing the pine marten, a natural predator of the grey squirrel

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15
Q

explain competitive exclusion

A
  • two organisms occupy very similar niches, then competition can exist between them for resources
    1 species may be slightly better adapted to compete than the other, so the other species could starve or not find a habitat
    The second species would then move to find a different niche
    • possibly evolve over generations to adapt to its new niche
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16
Q

explain resource partitioning

A

a particular resource eg. a fruit tree is divided up (partitioned) to satisfy the needs of different feeders
the fruit may be grazed by one species, the leaves by another
the two species are not competing directly for the fruit tree but coexisting on different parts of it

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17
Q

what are predators

A

consumers that kill and eat other animals

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18
Q

what is prey

A

those that are eaten

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19
Q

what happens to the number of predators and prey in a stable community

A

rise and fall in cycles, limiting the population sizes of both predators and prey

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20
Q

what are the stages of predator-prey cycle

A
  1. initially, the number of predators increases as there is more prey available
  2. the number of prey then decreases as there are now more predators
  3. then the number of predators decreases as there is now less prey available
  4. as a result, the number of prey increases as there are now fewer predators
  5. the cycle now repeats
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21
Q

humans have been successful in colonising every continent and many harsh habitats. what happens as a result of this

A

the human population has grown and is still in its logarithmic growth phase

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22
Q

what do humans have to do in order to avoid outcompeting many species and forcing extinction of other species

A

humans have to adopt the role of environmental custodian
- this places a responsibility on humans to manage habitats and species in a way that ensures sustainability and biodiversity for the good of future generations

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23
Q

what is conservation and explain

A

maintaining biodiversity and sustainability
by allowing changes to the profile of organisms in an ecosystem
allowing human activity alongside other species in a managed way

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24
Q

describe and explain preservation

A
  • maintaining habitats and populations exactly as they are now
    • making no allowance for usage by humans
    • this takes place in small geographical areas with little or no human population but allows no human intervention eg. areas of Arctic tundra where mineral mining has been prohibited
    • humans’ efforts to maintain a sustainable biosphere have focused on conservation rather than preservation
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25
Q

what are the reasons for conserving biological resources

A
  • people believe that humans have a moral obligation to prevent the manmade loss of biodiversity
    • the supply of important natural resources such as wood for construction and paper
    • employment
    • the supply of food for the human population
    • economic benefits to individual countries
    • as humans are the most intelligent species on the planet the responsibility falls upon their shoulders to protect and value all of the organisms on the planet
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26
Q

what is an example of biodiversity having a major effect on the stability of an ecosystem

A

if the temperature of a species-rich lake rises due to global warming:
- some species of fish in the ecosystem are unable to cope with the change while others can
- the fish that are able to cope will survive, reproduce and keep contributing to the ecosystem

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27
Q

what are keystone species

A

have a larger impact on the ecosystem than others

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28
Q

what is an example of a keystone species and explain

A
  • they graze in a very extreme way, knocking over and eating several species of tree
    - helps to maintain the ecosystem
  • elephant dung also provides a habitat for many important fungi and insect species
  • when elephants were hunted legally for their ivory, their numbers reduced and scientists observed a major negative impact on the savannah
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29
Q

what are some environmental reasons

A

humans need diverse ecosystems because of the essential environmental services they provide
- plants absorb carbon dioxide from the atmosphere and help to reduce the greenhouse effect and climate change
- microorganisms digest and break down the masses of organic waste that are produced by larger organisms
- humans have irrigation and drinking water thanks to the transpiration of plants and their contribution to the water cycle
- different fungi and bacteria species are a major part of the nutrient cycle that allows for nutrients to re enter the soil for further plant growth
- plants are producers in food webs. they are both a direct and indirect energy source for humans through fruit, vegetables and meat

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30
Q

what are some economic reasons

A

ecosystems have a lot of economic value
many of the medicines used today have originated from plants, fungi and bacteria
- (eg. the cancer-fighting drug paclitaxel is sourced from Pacific and Himalayan Yew Trees. the Himalayan Yew has declined in numbers due to over-harvesting for fuel and medicine. due to the large number of drugs that have already been sourced from nature it is reasonable to assume that there are other drugs, yet to be found in nature, that could be used in the future

ecotourism a major source of income for many countries
- any tourists travel to and spend money in National parks so they can see wildlife
- increased tourism in a country contributes to the economy and provides jobs

ecosystems have also made major contributions to the field of science and technology
- the specific enzyme used in DNA sequencing was first discovered in thermophilic bacterium found in a hot spring in Yellowstone National Park, USA

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31
Q

what are some aesthetic reasons

A

humans find great joy and pleasure in the beauty of nature
it provides inspiration for creatives such as photographers, poets, musicians and artists
there is a strong argument for preserving biodiversity because of its aesthetic benefits

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32
Q

what are ethical reasons

A

many people believe that humans have a moral obligation to prevent the loss of biodiversity that results from human activities
humans share the planet with millions of others species and they have no right to cause the extinction of other species
as humans are the most intelligent species on the planet the responsibility falls upon their shoulders to protect and value all of the organisms on the planet

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33
Q

what are some social reasons

A

many people enjoy spending time in the natural environment

there are many activities that people can do together in nature
- e.g. birdwatching, walking, climbing

such environments may be lost if they are not conserved, with the loss of the social benefits that they can bring

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34
Q

what is sustainability

A

the ability of an ecosystem to maintain (or ideally increase) its biodiversity whilst simultaneously providing humans with the resources they need over a long period of time

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35
Q

what are 2 examples of managed ecosystems for sustainability

A

commercial fishing
timber production

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36
Q

what does sustainable fishing means

A

leaving enough fish in the ocean
protecting habitats and marine food webs that fish rely on
human communities that catch and process fish can maintain their livelihoods

37
Q

how can the governmental regulations be enforced

A
  • establishing fishing quotas
    • agreeing areas of the ocean where fishing is banned (eg. spawning grounds) and permitted (eg. within a country’s territorial waters)
    • regulating mesh size of nets (to allow undersized/juvenile fish to escape)
    • limiting the size of the fishing fleet by issuing licenses
    • inspecting the catch as a fishing boat returns to port
      Banning certain practices eg. gillnets (static nets that catch anything that swims by, and the fish struggle and die in distress)
    • promoting sustainable practices such as trolling (different to trawling) that reduces bycatch
38
Q

what is bycatch

A

the unwanted fish and other marine creatures trapped by commercial fishing nets during fishing for a different species

39
Q

why is a lot of commercial fishing carried out illegally

A

there is a very wide area of ocean for the authorities to patrol
high demand and profit potential has made poachers more daring and willing to break the law

40
Q

what happens when timber production occurs

A

human demand for wood and timber products fluctuates
- in the mid-20th century UK forests were reduced to 5 % of the land area; today it’s back up to around 12 % through afforestation efforts

there is pressure on natural woodland to be felled and used as grazing land or for crop production, particularly in developing countries

41
Q

what are the 2 main group of tree crops used in commercial logging

A

fast growing conifers
slower growing broad leaf trees

42
Q

what are examples of fast growing confiers

A

spruce
pine
fir
larch

43
Q

what are examples of slower growing broad leaf trees

A

oak
beech
hazel

44
Q

conifers are grown in low grade agricultural land. what does this create

A

creates an effective monoculture

45
Q

what work has been done to increase the biodiversity of the areas where conifers are grown

A
  • the use of felling methods other than clear-felling introduces pockets of variety into a plantation
  • creation of clearings, firebreaks, selective felling, strip felling, edge habitat creation and in-situ leaving of naturally dead trees all attract other species and boost biodiversity
  • genomic research has identified suitable sub-species
    - e.g. of Sitka spruce that can grow faster and shorten the tree breeding process
  • recreation and public education projects now form part of the remit of forestry authorities
46
Q

what are coppicing and pollarding examples of

A

felling techniques that can be used to sustainably manage slower growing broadleaf trees

47
Q

what happens during coppicing

A

involves felling trees close to the ground and leaving the stump of the tree in the ground; new shoots can grow from the stump and can be harvested again after around 7 years
- woodlands can be divided into regions and coppiced on rotation so that only small areas of the woodland will be lacking in mature growth at any one time

48
Q

what is coppicing

A

means that trees remain relatively small and light can always reach the ground; this leads to more diverse woodland

49
Q

what happens during pollarding

A

similar to coppicing but the trees are cut 2-3 metres above the ground, leaving the mature tree trunk in place
- this brings many of the same benefits of coppicing but means that herbivores are less likely to be able to reach and consume the new shoots as they grow

50
Q

why are not all tree species suitable for coppicing or pollarding

A

eg. very few conifers will grow back in this way after being coppiced or pollarded

51
Q

what has industrialisation led up to

A

the more rapid consumption of natural resources by humans

52
Q

humans need food, space for infrastructure, grazing land for livestock, clean water, and natural resources. what does this create

A

created selection pressures on many other species, who are being outcompeted

53
Q

what is extinction

A

a natural biological process that happens on Earth and studies of fossils and ancient DNA have shown that millions of species have become extinct in the past

54
Q

what are examples of mass extinction events

A

ice age
asteroid striking the earth

55
Q

what happens to the rate of extinction during mass extinction events

A

it is very high

56
Q

scientists have been studying the current rates of extinction in recent years and many believe that the Earth is undergoing a current mass extinction. what is found to be the main cause

A

humans

57
Q

what are possible reasons for extinction

A

climate change
competition
introduction of non-native species
hunting by humans
mass agriculture
degradation and loss of habitats

58
Q

what levels increases in the atmosphere and what does it cause

A

carbon dioxide
- creates greenhouse effect

59
Q

what has an increase in carbon dioxide conc in atmosphere affected

A

increase in the mean global temperature
- ice caps are melting
- sea levels are rising, causing flooding and salination of soil in coastal areas
- this reduces agricultural productivity
Ocean temperatures and acidity are rising

60
Q

what does competition reduce and example

A

the population size of a species
- millions of years ago there were many different species of wild dog that lived in North America. when several cat species spread from Asia into North America there were high levels of competition between these carnivores. as a result, there are only nine species of wild dog that exist in North America today

61
Q

what are non native species

A

ehen humans colonised new land they would often exchange animal and plant species between their home country and the new land
- these introduced species are non-native

62
Q

why can non native species be highly problematic

A

they often have no natural competitors, predators or pathogens that help limit population growth
- without these natural population checks, non-native species can massively increase in number
- the large numbers of non-native species can negatively affect the native species through factors such as competition and disease

63
Q

explain hunting by humans

A

the development of livestock and the food processing industry has negated the need for many humans to hunt wild animals
- some humans in underdeveloped countries still have to hunt animals for survival
- the hunting of wild animals is still common and has become a sport for some individuals
- the rarer and more vulnerable species are often more desirable for a sport hunter
- if too many individuals within a species are killed then the population will become so small that it is no longer able to survive

64
Q

what is the main cause of species extinction

A

degradation & loss of habitats

65
Q

over recent years humans have aggressively destroyed animals habitats by cutting down forests, draining wetlands and polluting the water, soil and air. why is this highly problematic

A

species are adapted to survive within their specific habitat that has particular environmental conditions

without their habitat organisms will not get the resources they need to survive

as their habitat area gets reduced a species will:
- search for other suitable habitats
- compete with others for the remaining habitat

eventually the range of habitat can become so small or non-existent that a species is not able to survive and becomes extinct

66
Q

what type of ecosystem is Snowdonia National Park, Wales

A

renowned for its heathlands and woodlands of oak, ash, birch that harbour a wide variety of mosses, liverworts and lichens

67
Q

what is the name of the unique species found in Snowdonia National Park, Wales

A

Snowdon Lily

68
Q

what was the non native species introduced in Snowdonia and when was it introduced

A

Rhododendron ponticum
- introduced by humans in the mid-18th century

69
Q

what is Rhododendron ponticum

A

an attractive, pink-flowering shrub that grows to around 5 metres in height

70
Q

where does Rhododendron ponticum originate from

A

Spain, Portugal and Turkey

71
Q

R. ponticum has become a pest species that has colonised Snowdonia aggressively since its introduction by humans. what happened

A

it outcompetes, smothers and shades native species, such as oak and birch, by forming a thick understorey in which tree saplings cannot capture enough light
- the soil also becomes acidic
- mature trees die and are not replaced by new growth

72
Q

how does climate change help R. ponticum

A

as UK temperatures rise to become more like those in the Mediterranean and the Middle East
- it is able to live in its original climate

73
Q

what is conservation

A

the protection and management of species and habitats (i.e. ecosystems) in a sustainable way

74
Q

not everyone agrees with sustainable and conservation practices because

A

this may appear to limit them in certain ways (e.g. financially) in the short-term

75
Q

what does the sustainable use of ecosystems mean

A

means using these resources in a way that meets the needs of humans alive now, without reducing the ability of future humans to meet their own needs

76
Q

what is required to ensure humans use them sustainably but in a way that still fulfils their current needs

A

careful management of natural resources

77
Q

what are some examples of modern farming practices

A
  • farms became more specialised so they grew only one crop or raised one type of livestock ( monoculture)
    • there was a switch to growing cereal crops rather than vegetables
    • fields were made bigger to accommodate large machinery by the removal of hedgerows and stone walls
    • more land was turned to arable use by draining wetland and filling in ponds
    • the use of pesticides and fertilizers increased massively
78
Q

some modern farming techniques have had …..

A

a major negative impact on the level of biodiversity present in farming areas

79
Q

how have conservationists made strong efforts to try and maintain or improve biodiversity around farmlands

A
  • rewilded areas by removing all human interference and reintroducing native species
  • organic farming has been largely promoted and encouraged
  • re-establishment of hedgerows
  • planting of wildflower field margins
80
Q

improving grazing land

A

farmers deliberately fertilise and drain the land and sow the seeds of these two plant species
- other plant species are either outcompeted or the changes to the land mean it is no longer a suitable habitat for them - there is low species richness

natural grazing land that hasn’t been interfered with has a large variety of plant species present which can support a much greater range and number of insect species and bird species

wet grasslands have declined steeply in the last 100 years and are now regarded as biodiversity hotspots

81
Q

what does ploughing do

A

brings invertebrates to the surface

82
Q

what does harvesting do

A

provides spilt grain from the crops and seeds from weeds, as well as making invertebrates more accessible by removing their cover

83
Q

traditionally, crops were sowed in the …

A

spring
- the soil was ploughed in March
- grains were sown in late April
- harvest took place in September
- the gap between harvesting and ploughing was significant - five or six months

84
Q

modern farming has switched to sowing crops in ….

A

autumn
- the soil is ploughed in August
- grains are sown in September
- harvest takes place in July
- the gap between harvesting and ploughing is very short - one or two weeks

85
Q

what does the smaller gap between harvesting and ploughing mean

A

there is a very short period of time during the year when food is plentiful for birds however there is less time where the soil is redundant for the farmer

86
Q

what do scientist believe the switch from spring to autumn sowing will do

A

will greatly reduce the diversity of farmland birds in the future

87
Q

what does the reduction in the use of pesticides and inorganic fertilisers do

A

boost biodiversity in and around organic farms

88
Q

organic farming is more ………. than intensive farming, though less ……

A

sustainable
productive

89
Q
A

OCR AS/A Level Biology Context (24 decks)

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