Term 3 Flashcards
(126 cards)
1
Q
What is a community?
A
Set of all populations found in a given place
2
Q
How can interactions between individuals and populations be shown?
A
Food web
3
Q
What are the different trophic levels of a food web?
A
- Producers
- Consumers
4
Q
What happens at each trophic level?
A
There is a loss of energy
5
Q
What does the level of energy mean?
A
A lot of energy can sustain a lot of trophic levels and therefore a large community
6
Q
Describe what happens with 2 species in the same realised niche
A
Can’t maintain the same realised indefinitely one will drive the extinction of the other
- eg weasels
7
Q
Give an example of how there can be huge differences on a small spatial scale?
A
MEADOW - differences in soil and sunlight
DESERT - soil moisture varies greatly
8
Q
How do interactions differ on a temporal scale?
A
- Day and Night pollinators have different predators
- Species change activites and location seasonally
- Ckastal marine communities follow the rise and fall of the tide
9
Q
What is primary succession?
A
how a community forms from nothing to a climax community
10
Q
what are the stages of primary succession?
A
- bare rock and pioneer species
- intermediate species
- climax community
11
Q
what would be found at the bare rock stage of primary succession?
A
mosses lichens. die and decompose and soil forms. small plants grow eg grasses.
12
Q
what would be found at the intermediate stage of primary succession?
A
grasses, shrubs and shade intolerant trees
13
Q
what would be found at the climax community stage of primary succession?
A
shade tolerant trees eg oak. Larger animals
14
Q
what is secondary succession?
A
life has existed here before but a disturbance has occured
15
Q
describe secondary succession?
A
- a fiire
- colonised by r strategy species
- plants then shrubs then trees then climax
16
Q
what is cyclic succession?
A
communities can be subject to a continual distubance
- eg world without fire there would be huge areas of climax community in grasslands
17
Q
what are the natural sources of disturbances?
A
- abiotic: droughts, floods, hurricanes, fires
- biotic: invasions and extinctions
18
Q
what are the antropogenic sources of disturbances?
A
pollution, invasions, exploitation, global warming
19
Q
what are the two features of community stability
A
- resistance
2. resilience
20
Q
what is resistance of a community?
A
ability to not be disturbed
21
Q
what is resilience of a community?
A
how it recovers. elasticity (speed) and amplitude of change
22
Q
how to measure resistance?
A
How much does population abundance/community biomass change
How often are invasions are successful
How often do extinction occur
How much does biomass vary
23
Q
how to measure resilience?
A
How quickly does population abundance/community biomass return to normal
24
Q
describe the Exxon Valdez Oil Spill
A
11 million gallons of crude oil were spilled
Widespread spatially → all the way down the coast
Casualties
Seabirds, sea otters, harbour seals
Clean up costs
3.2 billion dollar
25
what was the recovery after the oil spill?
Unoiled shore (control)
Oiled then cleaned
Oiled and uncleaned
Rockweed populations returned to normals in 2 years (uncleaned) took 1 year longer than (cleaned)
26
what was the diversity of sediments 2 years after oil spill?
Uncleaned: reduced abundance but not diversity
Cleaved: reduced diversity and abundance
27
what are biological invasions?
- Populations entering a novel community
- often natural: process of speciation and extinction
- successful species expand in range
- could have no effect or a profound effect
28
What are the 4 different consequences of invasions?
1. Invader dies out before establishing original community is unaffected
2. Invader establishes and augments the community with no effect on the rest of the community
3. Invader establishes with one or more extinction ni the resident community
4. Invader establishes with one or more extinction in the resident community but eventually the invader dies out
29
what is ecesis?
the successful establishment of a plant or animal in a new habitat
30
what is an example of a natural invasion?
Collared dove
| Spread from asia minor across Europe to Britain in about 50 years
31
what is human induced invasions?
Most invasions are currently the result of human activity
Especially as a result of trade and colonisation
Ships provide many opportunities in cargo holds and ballast tanks
32
what are ballast tanks?
When a ship unloads cargo → to make up for weight it takes up huge volumes of water
Travels back
Expels the water
This water can contain: comb jelly, cholera, zebra mussels → invasive marine species
33
describe human induced invasions
Leading to a homogenization of the worlds iota
Human-dominated ecosystems are growing, dominated by a few crop species and a handful of ubiquitous commensal species
Greater proportion of land covered with human invasive species
34
what is a keystone sepcies?
species with a strong interaction with a disproportionate effect on communities
- species whose removal would lead to significant changes in the food web
35
what are ecosystem engineers?
actively shaping the physical environment, creating habitat that wouldn't otherwise exist
- eg beavers
36
what are keystone mutualists?
pollinators of ecologically dominant plants, or nitrogen fixing bacteria supporting legumes and hence a whole plant community and its reliant animals
37
what is an ecosystem?
community of organisms and physical environemnt
38
how is energy transferred to producers?
(photosynthetic and chemosynthetic organisms) take up inorganic carbon, nitrogen, phosphorus and other compounds form the environment and convert them into proteins, nucleic acids, lipids and more
39
how is energy trasnferred to consumers?
Primary producers directly
| and/or other consumers
40
what are decomposers and detritivores?
return nutrients back to the soil
41
describe a marine ecosystem
photosynthesis by plankton
repsiration
have carbon
42
how is ecosystem energy not recycled?
- energy must be continually harvested from the environment
- photosynthesis = key producer
- energy stored in organic molecules (bonds)
- lots of energy is lost
43
what happens to biomass at each trophic level?
- reduces
- a lot of the biomass prodcued at one level isn't consumed by the next level
- get a pyramid
44
how much is lost at each trophic level?
only about 10% of energy and biomass is passed on
45
what controls primary production?
- photosynthesis
- sunlight
- water
- nutrient availability
46
how does solar availability vary?
- intensity varies due to the curvature of the earth
| - seasonality as the earth is on a tilt
47
how can water availability limit photosynthesis?
- depends on water
- carbon dioxide that can be fixed in a certain time period relies on water
- irrigation
- high water stress where people are living
48
how does nutrient availability vary?
- plants, algae and photosynthetic bacteria also need nitrogen, phosphorus, sulphur, iron
- abundance of one nutrient cannot make up for the lack of another
49
what is liebigs law of the minimum?
primary production is limited by the nutrient that is least available relative to its use by primary producers
50
how does primary productivity vary around the globe?
- little or no water = little or no productivity
- apart from this seems to follow the solar radiation map
- have to factor in altitude
51
is biological diversity related to NPP?
greater primary production means that an ecosystem can support more plants
can support more herbivores
can support more predators
52
what does greater primary production mean?
ecosystem can support more and a greater variety
53
what are the main arguments for whether species richness and stability are linked?
- islands = small = vulnerable to invasions = a lot of extinctions
- cultivated land = susceptible to pest outbreaks
- rainforests = don't show these outbreaks
54
what are the arguments against species richness and stability being linked?
- continents (australia) - vulnerbale to invasions
- monoculture bracken appear stbal
- outbreaks do occur in rainforests
55
what happens when the prey community was more species rich?
predator community was more stable
| - eg paramecium
56
what happened when predators where introduced to stable producer and consumer communities?
caused extinctions
57
what was McNaughtons experiment 1?
Gnu exclusion in the Serengeti
Gnus were allowed in some areas and excluded from others
Plant biomass was monitored
Biomass changed more in the species poor system when grazed by gnus
58
what was McNaughtons experiment II?
Severe drought occured in 1988
Vegetation abundance was monitored before and after the drought
The most diverse systems showed the least change (resistance)
59
what was Tilman's long term diversity experiment in Minnesota?
200 plots were seeded with up to 22 grassland species
Water, nutrient availability and carbon dioxide was controlled, different disturbance regimes followed and primary production was measured annually for 23 years
Major drought perturbed the system in 1987-88
60
what were the results of of Tilman's experiment?
Species rich plots were more resistant to drought and after drought
Species rich plots had more variable average biomass over time
Species rich plots had greater biomass
61
what is the portfolio effect: the diversity - stability hypothesis?
By analogy to portfolio of shares - a portfolio tends to be less volatile than any single share
Diversity increases variability at the species level
Diversity enhances stability at the community or ecosystem level because there is more opportunity for the demise of one species to be compensated for by another species
62
what do species rich plots have a greater resistance to?
invasions → the available niches are more likely to be full already
63
describe species richness and stability
Individual populations may be more prone to fluctuation in the face of disturbance in more diverse communities
Community and ecosystem properties may become more stable as species richness increases
64
how are systems dynamic?
Individuals are dynamic; they are born, move and die
Populations are dynamic, increasing and decreasing in response to local physical and biological interactions of individuals
Communities and ecosystems may be dynamic with species arriving and departing as a result of invasion, disturbance and succession
Biomes are stable and distinctive assemblages of species found over broad regions of the earth
65
what is a biomes?
Terrestrial biomes have characteristic vegetation reflecting evolutionary adaptations to climate
Oceanic biomes are less well understood
66
how do biomes reflect the interaction of earth and life?
The distribution of biomes reflects local climate
Solar radiation, precipitation and wind vary with latitude and altitude
Plants need to balance CO2 intake with water loss by means of adaptations in shape and physiology
67
what is the evaporation ratio?
The amount of water evaporated directly from earth’s surface (from ponds, rivers and soils)
To the amount of water transpired by plants
68
what kind of vegetation can be supported in the desert?
Low annual precipitation
High evapotranspiration ratio
Soil moisture evaporates rapidly
Plants must keep transpiration and therefore photosynthesis to a minimum
69
what kind of vegetation can be supported in the rainforest?
High annual precipitation
Low evapotranspiration ratio
High precipitation allows almost unlimited transpiration
And therefore high photosynthetic rates → high growth
70
what kind of vegetation can be supported in temperate zones?
Moderate annual precipitation
| Intermediate evapotranspiration ratio
71
what are some examples of cnvergent evolution on functions?
C4 carbon fixation by plants using a different metabolic pathway to capture carbon dioxide with differences in leaf anatomy and cell biology
Carnivorous plants in nitrogen deficient areas to obtain nitrogen from insects
Tube like spurs contains nectar in flowering plants
Prickles thorns and spines to deter herbivores
72
what are the latitudinal gradients of diversity?
Species diversity peaks near the equator and declines towards the poles
73
why do the tropic contain so many species?
- Tropical biomes are older
- Tropical biomes are less variable
- There is more land in the tropics
- Tropical biomes have more enemies
74
what effect does tropical biomes being older have?
Tropical biomes have evolved over tens of millions of years
Climate change and ice ages have reshaped biomes closer to poles more recently
Rates of diversification are similar in tropical and temperate zones
75
what effect does tropical biomes being less variable have?
Individuals in temperate areas experience a wide range of temperatures over the year
Individuals in tropical regions experience similar conditions year round
Harder to adapt successfully to variable conditions, but species who do can have broad geographic ranges
76
what effect does tropical biomes having more land have?
More land surface area at low latitudes
| Species-area curve therefore suggests there will be more species
77
what effect does tropical biomes having more enemies have?
Insects and fungi designed to attack particular trees are more abundant in wet tropical forests
It benefits trees to be further apart from neighbours of the same species leaving more room for different species in the same unit area
78
what does high diversity mean for population density?
low population density
79
how far apart can individual plants be before population is no longer viable?
Depends on how far ranging are the animal pollinators
| Mutualisms contribute to diversity differences between tropical and temperate regions
80
what is the keeling curve?
monitors carbon dioxide levels in the atmosphere
- there are seasonal oscillations
- long term = increasing carbon dioxide
81
what causes atmospheric carbon dioxide to vary through the year?
billions of metric tons of CO2 entering and leaving the atmosphere every year
82
what causes atmospheric carbon to vary over decades?
summer removal of CO2 does not balance the winter increase
83
what are the inputs of carbon dioxide?
- geological eg volcanoes
- biological eg respiration
- human eg fossil fuels
84
what are the outputs of carbon?
- geological eg chemical weathering of rocks
- biological removal eg photosynthesis
- human removal eg bio energy with carbon capture
85
what is short term carbon cycling?
complementary metabolic processes of photosynthesis and respiration
86
how is carbon effected by photosynthesis?
Removal of CO2
Estimated that 700 billion tonnes of carbon is removed from the atmosphere by photosynthesis
About 25% of the total CO2 in the atmosphere is used in photosynthesis each year
87
how is carbon effected by respiration?
700 billion tonnes being put back into the atmosphere through respiration
Aerobic respiration converts chemical energy into ATP form use in cellular processes
88
how does carbon vary seasonally?
Global atmospheric carbon decliens through the northern summer then increases through the northern winter
Respiration is more or less constant through the year
Photosynthesis is seasonal with higher rates in summer and lower in winter
89
how can we measure the atmosphere in the past?
When snow falls on glaciers → gradually gets compacted down → spaces that were in contact with the atmosphere are sealed off → drilled through the ice → extract ice cores → can then date atmospheric samples in that ice → can see lighter summers and darker winters in the ice cor
90
what is the photosynthesis-respiration balance?
Air samples trapped in ice from law dome in antarctica allowed measurement of CO2 levels over the last 1000 years
91
what do longer term trends show?
Current changes in CO2 are unusual on the timescale of the last millenium
Atmospheric CO2 was approximately in balance until the start of the industrial revolution
There is correlation between increasing atmospheric CO2 and human activities
92
how can we prove that human activities have contributed to the increase of atmospheric CO2?
ooking at the chemical composition of the atmosphere
The proportion of 13C is declining because the CO2 being added to the atmosphere has less 13C than the CO2 already there
The proportion of 14C is declining because the CO2 being added to the atmosphere has less 14C than the CO2 already there
Suggests that the burning of fossil fuels is the reason why carbon is increasing
93
where is carbon stored?
750 billion tons are stored in the atmosphere
600 billion tons are stored in organisms on land
1,300 billion tons are stored in soils
40,600 billion tons are stored in the oceans
Mostly as dissolved inorganic carbon
3 billion tons as organisms
Deep in the ocean
100, 000, 000 billion tons are stored as CaCO3 (calcium carbonate) → limestone and organic matter
1600 billion tons in fossil carbon deposits (some is being released through human activities)
94
what are fluxes?
the rates at which carbon flows from one reservoir to another
95
what happens if there is a large flux?
size of the reservoir size can change rapidly
96
what is the flux in the atmosphere like?
about 25% of the atmospheric reservoir
| Makes the size of the atmospheric reservoir sensitive
97
how do physical/geological processes drive longer term changes?
Release of CO2 into the atmosphere by volcanism
CO2 combines with rain to form carbonic acid
Carbonic acid reacts with rocks
Carbon carried by rivers
Carbon is used to form animal shells
When animals die their shells form limestone
Subduction of carbonate rocks → plates, magma chamber back out into the atmosphere via volcanoes
98
how is CO2 related to temperature?
CO2 is a greenhouse gas → lets radiation in but traps heat
Fluctuations in CO2 coincide with fluctuations in glacier melting and reforming
As the glaciers go away → forests spread → why do we get an increase in CO2 and not oxygen → the oceans are responsible
99
breifly describe the carbon cycle?
When life began the atmosphere and oceans contained very little or no oxygen gas
The carbon cycle with the biological components of photosynthesis and respiration not quite in balance allowed accumulation of oxygen on a geological time scale
This provided an oxygen rich world with a remarkable diversity of species interacting to cycle carbon through the biosphere
100
what impact do humans have on the planet?
- no part is free from human infleunce
- plastic is a big problem
- get into bellies of aquatic creatures
101
why is the nitrogen cycle important?
- needed to synthesize proteins, nucleic acids and other molecules
- N2 is plentiful but can't be used unless fixed
102
what form does nitrogen need to be in?
NH3 (ammonia) or nitrate (NO3-)
103
where is nitrogen stored?
```
atmosphere, soil and organisms
Atmosphere → has the largest amount: 4 000 000 billion tons
Organisms have 35 billion tons
Soil has 95 billion tons
Water has 22 000 billion tons
```
104
describe the nitrogen cycle
- plants = nitrates from soil
- bateria = nitrogen fixing bacteria live in root nodules
- animals = eat plants
- decomposers
- nitrogen in atmosphere
105
what is the effect of lightning on nitrogen?
Lighting oxidised nitrogen in the air which are deposited in the air
106
where is nitrgoen available?
Microbial fixation and lightning move about 150 million tons into available nitrogen for biological organisms
Another 150 million tons comes from industrialisation
107
what happens to nitrogen?
ends up in the water
| - some used by bacteria
108
what are the pre industrial nitrogen fluxes?
Estimated at 90 - 150 million tons per year (from atmosphere to ecosystems)
About the same from ecosystems back to the atmosphere
109
what are the additional nitrogen fluxes?
80 million tons → fertilizers (extracted from the atmosphere)
40 million tons from biomass burning
110
what is soil depletiion?
Fertilised soil is nutrient rich, requiring the constant cycling of nutrients between organic and inorganic forms
When components contributing to fertility are removed and not replaced the conditions that support soil fertility are not maintained
Harvesting crops on a large scale → depletion of nutrients and degradation of the soil itself
111
how does nitrgoen fertilize soil?
When crops are grown in the same place year after year the amount of biologically available nitrogen goes down
To sustain high yields farmers must add nitrogen as fertilizer
Much of this is washed away
112
how are algae and cyaonbacteria boosted during eutrophication?
Essentially fertilizing the water
Algae and bacteria have a population increase
Eventually falls to the bottom of the water and its fed on by bacteria and other heterotrophic organisms
The demand for oxygen depletes the water of oxygen → drastic consequences for the rest of the organisms in the water
Eutrophication leads to dead zones → can see them from space
One of the worst is at the gulf of Mexico
Most of europe has an excess of nutrients
Only a tiny proportion of europe that doesn't have an excess of nutrients as a result of fertilizer
About 1-2% of the fossil fuels we use to create fertilizer → not just the placing of the fertilizer but also the production
The nitrogen is depositing oxides on the soil
Can destroy some of the fragile ecosystems created
113
why is the phosphorus cycle important?
Atmosphere, soil ,water and organisms
114
where is phosphate gained and lost from?
Biggest part is moving the phosphorous moving from the soil to the plants to the organisms and back to the soil
Process of erosion → breaking phosphorus rich rocks down
Addition of phosphates from fertilizers → run into the water
Phosphate runoff can affect areas that have adapted to low phosphate levels
115
what impact has phosphate had on the everglades in florida?
Huge specialised area → used to low phosphate
Phosphate fertilizers used have contributed to increase in phosphate in the everglades
Invasive species that can cope with phosphate better outgrow the native species
Impact the interaction between species to cause disturbance
116
in what way are phosphorus sources scarce?
No industrial method to create phosphorus fertilizers
Natural sources aren't enough to meet demand
We are currently mining phosphorus rock → huge disruption to landscapes
117
why is the water cycle important?
Water evaporates from the ocean and from land → condenses → falls as rain and back to the land
Have water stores under the land and also stored as ice and snow
The water cycle is BIG
118
how much water is appropriated by humans?
54%
119
how do humans use water?
70% of appropriated water is used for agriculture
30% is used for domestic, municipal and industrial purposes
In europe → agriculture only 33%
In arid countries → up to 90% of water
120
how does food use a lot of water?
In california:
1kg of wheat = 1.3 m3 of water
1kg of meat = 16 m3 of water
121
why is the demand for water high?
Every person requires 2000 m3 of water per year in soil moisture to produce food to survive
122
what is the ecological footprint?
Measures how fast we consume resources and generate waste
| Isn't enough land on the earth → if everyone lived like an American we’d need 5 planets
123
what global emissions have increased in the atmosphere?
methane and carbon dioxide
| - If we reduce our emissions, the situation for these gases could rapidly improve for CO and CH4
124
what is the atmospheric life of CO2?
100 years
125
what is the weather?
series of short term events and can be very variable and changeable - cold and warm years, wet and dry periods
126
what is the climate?
average weather over a long time period with evidence for change coming from records over decades or centuries
