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principles of ecology > module 2 > Flashcards

module 2 Flashcards

1
Q

why are there so few native species to Britain?

A
  1. glaciers have advanced south several times (clean slate each time)
  2. English Channel formed only 7500 years ago. sea levels rose and formed a barrier to plant migration.
  3. narrow range of habitats as no climatic variation and np great altitudes.
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2
Q

two types of fossils

A
  1. MACROFOSSILS - sometimes find charcoal remains, seeds and fruits, leaf impressions.
  2. MICROFOSSILS (pollen and spores) - have a very resistant outer coat, called exile, made up of sporopollenin.
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3
Q

Silurian fossils

A

They are about 7 mm tall.

◆ They all have names and a
taxonomic place

◆ They have spore bodies on
the end of stalks

◆ They do not have roots or
leaves

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4
Q

devonian fossils

A
  • A reconstruction of the Rhynie chert fossils
  • Very famous, because so well preserved – probably vertically in a swampy peat bed.
  • Chert is a soil type – fine crystalline quartz
  • They have primitive vascular systems.
  • This is how we know the age of vascular plants
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5
Q

the quaternary period

A
  • 2.5 million years ago to the present
  • at least 21 cycles of cold and warm
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6
Q

four major interglacials in the quaternary period

A

cromerian

hoxnian

ipswichian

flandrian (present)

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7
Q

names of glacial periods

A

the devensian - Britain

the weichselian - Northern Europe

the wurm - the alps

the wisconsinan - North America

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8
Q

what causes major changes in climate?

A
  • change in eccentricity - oval orbit
  • periphelion changes - suns distance to earth
  • obliqueness - tilt
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9
Q

principle of uniformity

A

assumes that the ecology of a species in the past was similar to its present ecology

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10
Q

what factors can influence pollen assemblage?

A
  • species differ in how well they preserve
  • pollen and spores are tiny (some more easily transported than others, so may be deposited far away from where they wee produced)
  • some species produce more pollen than others - relative abundance of plants difficult to assess.
  • more pollen produced by wind pollinated species
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11
Q

what does a pollen diagram display?

A

how vegetation has developed through the ages due to changes in climate

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12
Q

first Godwin zone

A

pre temperate zone

sea buckthorn and grasses present at the end of the previous glaciation.

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13
Q

Godwin zone 2

A

early temperate zone

mixed oak forest with some thermophiles species present

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14
Q

Godwin zone 3

A

late temperate zone

expansion of forest trees

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15
Q

godwin zone four

A

post temperate zone

boreal trees dominate again: betula and pinus

thinning of the forest occurs and non-tree pollen is frequent.

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16
Q

birk’s climate stages

A
  1. cryocratic
  2. protocratic
  3. mesocratic
  4. oligocratic and telocratic
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17
Q

Cryocratic phase

A

– Glacial stage, cold and dry

– Vegetation sparse, species poor arctic-alpine or steppe on thin skeletal mineral soils

– Frequent frost disturbance
(permafrost)

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18
Q

Protocratic phase

A

– Rising temperatures

– Species-rich grassland, scrub and open woodland

– Base-rich and fertile soils with low humus content and
little leaching

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19
Q

Mesocratic phase

A

– Climatic optimum

– Closed temperate deciduous woodland with
increasing species richness.

– Brown earth soils of high base status.

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20
Q

Oligocratic and Telocratic phases

A

– Climate warm at first, but begins to deteriorate.

– Soils become leached to podzols or acid peats
leading to acid, nutrient poor conditions.

– Vegetation becomes dominated by conifers,
heathers and plants of open sites.

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21
Q

the devensian glaciation

A

the last glaciation

began 73 ka bp to 14 ka bp

part of the country that wasn’t covered in ice had periglacial conditions (-20/30 degrees winters and 10 degrees summers. mineral soils)

sea level was 130-160 m below current

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22
Q

holocene interglacial

A

current interglacial

began 14 km bp.

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23
Q

glacial periods starting with lower dryas.

A

lower dryas
allerod
upper dryas
pre-boreal
boreal
atlantic
sub-boreal
sub-atlantic

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24
Q

lower dryas

A

14 - 12 ka bp.

ice retreated, still cool.

vegetation - low tundra grassland, grass, plantain and weeds.

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25
Q

allerod period

A

12,000 to 10,800 years bp

warmer - continental climate.

vegetation dominated by birch scrub, grasses and weedy species.

26
Q

upper dryas

A

10,800 - 10,300 yearsbp.

cold period.

ice re-advanced causing decline in birch and increase in some tundra.

27
Q

pre-boreal

A

10,300 to 9000 years bp.

warmer.

birch forest with increasing pine, elm, oak and hazel. decreasing grasses and herbs.

canopy closes.

28
Q

boreal period

A

9000-7500 years bp.

warm dry continental period.

elm, oak, hazel woodland.

pine and birch declining.

29
Q

atlantic period

A

peat accumulated because it was wetter.

7500 - 5000 years bp

warm wet oceanic climate.

30
Q

sub-boreal

A

5000 to 2500 years bp.

significant decline of elm.

31
Q

sub-atlantic period

A

2500 bp to present

progressive disturbance of the forest.

culture is neolithic crops of rye and barley planted and sheep and goats kept.

32
Q

tephra

A

volcanic air-fall material

33
Q

radiocarbon dating

A

when an organism dies, the proportion of c14 (radiocarbon) declines because it decays to normal nitrogen.

the ratio of radiocarbon to normal carbon gives the approximate age.

34
Q

what is succession and what three processes does it involve?

A

Succession is a directional non-seasonal
cumulative change in the types of plant
species that occupy a given area through time

  • colonisation
  • establishment
  • extinction
35
Q

steps in primary succession

A
  1. denudation
  2. immigration of species
  3. ecesis
  4. competition and interaction
  5. reaction
  6. stabilisation
36
Q

denudation (in primary succession)

A

pre-biotic changes occur before plant establishment can begin e.g. weathering of rock faces

37
Q

immigration of species (in primary succession)

A

arrival of species depends on:

  • dispersal mechanism (wind dispersal etc)
  • seed or spore size
  • distance to source of propagules
  • chance
38
Q

ecesis (in primary succession)

A

germination and early phase of establishment - depends on suitability of habitat.

39
Q

competition and interaction (in primary succession)

A

earliest colonists find little competition

populations expand exponentially until a resource is limiting

then interaction - stronger competitors may eliminate the earliest colonisers

40
Q

reaction (in primary succession)

A

presence of organisms changes the environment for others - creates new environments allowing the ecesis of other species

41
Q

stabilisation (in primary succession)

A

rate of change in the environment slows down

  • little immigration
  • little ecesis
42
Q

sere

A

the pathway of a succession. a successional sequence of communities.

43
Q

three types of lichen

A
  1. crustose - like a crust
  2. foliose - turned up edges like foliage
  3. fruticose - shrubby
44
Q

why are lichens often early colonisers

A
  • need little water
  • need no soil
  • are very hardy.
45
Q

example of succession in the lithosphere starting with lichen

A

lichen increases water retention allowing moss to invade.

moss breaks down rock and soil increases. moss penetrates rock cracks.

annual herbs and grasses

pioneering shrubs/trees

mixed deciduous forest

46
Q

sequence of succession on psammosere

A

COASTAL SAND DUNES

25 year old dunes
- marram grass is main plant

100 year old
- prairie bunch grass

150 year old
- conifer trees

225-400 year old
- mixed forest of pines

more than 400 years old
- deciduous trees

47
Q

sequence of succession in the hydrosphere

A

micro organisms.

submerged leaved macrophytes establish

floating leaved macrophytes

marsh

swamp

sedges

pond floor is raised by debris

Carr, willow and alder establish.

mixed oak woodland

48
Q

walkers hydrosphere succession

A
  1. Biologically unproductive open water
  2. Open water with micro-organisms
  3. Open water with submerged macrophytes
  4. Open water with floating leaved macrophytes
  5. Reedswamp
  6. Tussock Sedge swamp
  7. Fen (herbs on organic soil)
  8. Swamp carr (trees on
    unstable peat)
  9. Fen carr (trees on stable
    peat)
  10. Aquatic sphagnum species
  11. Sphagnum bog
  12. Marsh (herbs on mineral soil)
49
Q

why is there no progression to forests in the hydrosphere?

A
  • low nutrient content
  • low pH
  • anoxia
50
Q

secondary succession

A

The progression of communities where pre-existing vegetation has
been disturbed or destroyed and a soil (and possibly a seed bank) is already developed on the site.

51
Q

secondary succession stages

A
  • pioneer species - various annual plants
  • perennials and grasses
  • shrubs
  • softwood trees and shrubs
  • hardwood trees
52
Q

early successional plants (secondary succession)

A

pioneer species

high growth rate

small size

wide dispersal

fast population growth

53
Q

late successional plants (secondary succession)

A

lower rates of dispersal

lower rates of colonisation

slower growth rates

larger sizes

longer lives

54
Q

super-organism

A

Clements view of vegetation as one being. the whole was greater than the sum of the parts.

it is born, it develops and it reaches maturity.

it heals itself with secondary succession.

55
Q

climax community

A

slow rates of change

not static (not still)

56
Q

autogenic changes

A

succession driven by organisms themselves. organisms alter the habitat.

57
Q

allogenic changes

A

succession driven by changes in the environment

more common than autogenic changes.

58
Q

five main problems with Clements

A
  1. concept of suer-organism
  2. facilitation model
  3. climactic climax
  4. stable climax
  5. autogenic succession
59
Q

Gleasons individual model

A

individual species are struggling to maintain themselves not facilitating others.

species behave individualistically

composition determined by the availability of species locally.

succession does not lead to definite climax

60
Q

tolerance model

A

all species can colonise early on, but the most rapid colonisers and fastest growers dominate.

poor colonisers tolerate fast growers.

61
Q

inhibition model

A

each plant inhibits the establishment of other species by site pre-emption (do it before them)

62
Q

4 main sources of evidence of succession

A

direct observations through time

historical evidence

preserved biological evidence

spatial sequences

principles of ecology (5 decks)

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