CHAPTER 23 - ECOSYSTEMS Flashcards
1
Q
What is Ecology
A
The study of relationships between organisms and their environment
2
Q
What is an ecosystem made up of
A
All living organisms that interact with one another in a defined area
3
Q
What are the two types of factors that affect ecosystems
A
Biotic and Abiotic
4
Q
What are biotic factora
A
Living factors
eg. Forest ecosystem, shrews and hedgehogs are biotic factors as is the size of their populations - the competition between these two animal populations for a foot source
5
Q
What is an abiotic factor
A
The non-living or physical factors. eg. The amount of rainfall received and the average temperatrue
6
Q
Name some biotic factors
A
Most forms of competition eg. Competition for food, territory and breeding partners
7
Q
What are some abiotic factors
A
Light
Temperature
Water availability
Oxygen availability
Edaphic (soil) factors
8
Q
How is light an abiotic factor
A
Most plants are directly affected by light availability, as light is required for photosynthesis; greater light availability, the greater the success of the plant
9
Q
What strategies do plants use to cope with different light intensities
A
Areas of low light will have larger leaves, develop photosynthetic pigments which require less light, or reproductive systems that only act when light availability is at an optiumum
10
Q
How does temperature act as an abiotic factor
A
Affects rate of enzymes controlling metabolic reactions. Plants will develop more rapidly in warmer temperatures, and so will ectothermic animals
11
Q
How do changes in temperature affect an ecosystem?
A
Trigger migration in some species
Triggers hibernation in others
Triggers leaf fall, dormancy or flowering in others
12
Q
How does water availability act as an abiotic factor
A
Lack of water leads to water stress, which will lead to death
Causes plants to wilt as turgor pressure decreases and plant cannot stay upright or conduct photosynthesis
13
Q
What are plants called that have adapted to deal with low water availability
A
Xerophytes eg. cacti
14
Q
How does oxygen availability act as an abiotic factor
A
In aquatic ecosystems, it helps to have fast-flowing cold water which contains high concs of O2
If water becomes too warm, or flow rate too slow, the Oxygen conc will drop, leading to the suffocation of aquatic organisms
15
Q
How does waterlogged soil affect plants
A
Air spaces are filled with water, reducing oxygen availability for plants
16
Q
What are the types of soil size and how does it effect organisms
A
Clay - fine particles, easily waterlogged, and forms clumps when wet
Loam - This has different-sized particles, retains water but doesnt become waterlogged
Sandy - This has coarse, well-separated particles that allow free draining - sandy soil doesnt retain water and is easily eroded
17
Q
Explain what is meant by the term ‘dynamic ecosystem’
To which ecosystem does the term apply
A
Ecosystem whose biotic and/or abiotic factor(s) are constantly changing
all ecosystems are dynamic
18
Q
State two biotic and two abiotic factors in a pond
A
Biotic populations of (named) organisms
competition between (named organisms) for a
resource
Abiotic any two from (for example): temperature, light intensity, dissolved oxygen
concentration, pH
19
Q
Explain why abiotic factors often have a greater effect on plant species than on animal species in an ecosystem
A
Animals able to migrate, e.g., towards warmer/cooler temperatures, to search for alternative food
supplies
animals able to move, e.g., to find shelter, to search out water supplies
many animals able to regulate their internal temperature, so less affected by temperature changes
many animals able to survive using a range of food sources
20
Q
What is a trophic level?
A
A hierarchical level in an ecosystem, consisting of organisms sharing the same function in the food chain and the same nutritional relationship to the primary sources of energy
21
Q
What is always the first trophic level
A
The producers
22
Q
What is a producer
A
An organism that converts light energy into chemical energy by the process of photosynthesis
23
Q
What are the subsequent trophic levels after produces
A
Consumers
24
Q
What are consumers
A
Organisms that obtain their energy by feeding on other organisms
25
What are primary consumers
The consumer that easts a producer
26
How are consumers the labelled
Successively,
Secondary consumers consume primary consumers
Tertiary consumers consume secondary consumers etc...
27
What do decomposers do
Break down dead organisms, releasing nutrients back into the ecosystem
28
How is biomass represented
Biomass pyramids
(pg 611)
29
What is biomass
The mass of living material present in a particular place or particular organism
30
How do you calculate the biomass at each trophic level
Multiply biomass present in each organism by the total number of organisms in that trophic level
31
What is the flaw in calculating biomass
only calculates biomass present at a particular time, and doesn't take into account seasonal changes
32
What is the easiest way to measure biomass
Measure fresh material, discounting the water, so a dry mass is needed
33
How are organisms prepared to calculate dry mass
Killed, Placed in an oven at 80 degrees celsius until all the water has evaporated - when a constant mass is achieved
34
What units are biomass measured in?
Joules or Grams per metres squared of land, or cubed in water
35
Why is the biomass in each trophic level always less than the trophic less than the trophic layer below
When animals eat, only a small proportion of the food they ingest is converted to new tissue
36
How is the energy available at each trophic level calculated
kilokoules per metre squared per year
kJ m-2 yr-1
37
What is ecological efficiency
The efficiency at which biomass or energy is transferred from one trophic level to the next
38
What percentage of sunlight do producers convert into chemical energy and therefore biomass
1-3%
39
Why do producers only convert a small percentage of sunlight into biomass
Not all the solar energy available is used for photosynthesis - approximately 90% is reflected
Other factors may limit photosynthesis eg. water availability
A proportion of the energy is lost - as it is used for photosynthetic reactions
40
How can energy available at the next trophic level be calculated
Net production = gross production - respiratory losses
41
Why do consumers at each tropic level convert at most 10% of the biomass in their food to their own organic tissue?
Not all the biomass of an organism is eaten, eg. Bones and roots not eaten
Some energy is transferred to the environment as metabolic heat
Some parts of an organism are eaten but indigestible and egested as faeces
Some energy is lost from the animal in excretory processes
42
How do you calculate ecological efficiency
(Energy or biomass available after transfer/ energy or biomass available before transfer) x100
43
What impact can humans have on biomass in an ecosystem
Agriculture
44
How many trophic levels are in a livestock agriculture
Producer - Animal Feed
Primary consumers - livestock eg. Cow
Secondary consumer - Human
45
Describe how the biomass of a trophic level is measured
Wate removed from one organism by heating it in an oven at 80°C
the ‘dry’ organism is then
weighed to measure its mass in grams
this figure is multiplied by number of organisms present in
given area
46
Explain how human activities can manipulate the transfer of biomass through ecosystems
Through agriculture number of trophic levels in food chain is minimised
to maximise energy /
biomass transfer to humans
47
Explain why biomass decreases at each level in a food chain
Energy is lost from an organism because (any three from): not all of an organism may be eaten,
parts of an organism may be indigestible,
some energy is transferred to the environment through
metabolic heat, some energy is lost through excretion
48
How does energy flow through an ecosystem
Linearly
49
What is decomposition
A chemical process in which a compound is broken down into smaller molecules or its constituent elements
50
How are unusable forms of essential elements such as nitrogen or carbon, processed into being used
Turned into inorganic elements and compounds and returned to environment
51
What is a decomposer
An organism that feeds and breaks down dead plant or animal matter, thus turning organic compounds into inorganic ones (nutrients) available to photosynthetic producers
52
How big are decomposers
Primarily microscopic such as fungi and bacteria, but also include larger fungi such as toadstools and bracket fungi
53
Why are decomposers saprotrophs
Because the obtain their energy from dead or waste or organic material (saprobiotic nutrition)
54
How do decomposers eg. fungi digest their food
Secrete enzymes externally onto dead organisms or waste matter
Enzymes break down complex molecules into simpler soluble molecules - which are absorbed by decomposers which are then released into the environment
55
What are Detritivores
Another class of organism involved in decomposition
56
How do detritivores help speed up the decay process?
feeding on detritus - dead and decaying material
This breaks it down into smaller pieces of organic material, increasing Surface Area for the decomposers to work on
57
What are some examples of detritivores
Woodlice - break down wood
Earthworms - Break down dead leaves
58
How do detritivores digest matter
Performs internal digestion
59
How do animals obtain the nitrogen they need
Through food eaten
60
How do plants obtain the nitrogen they need
Take it from the environment
61
What is Nitrogen an essential element for?
making amino acids (consequently proteins) and amino acids
62
What percentage of the atmosphere is Nitrogen gas (N2)
78%
63
To be used by living organisms, what does nitrogen need to be combined with
Oxygen or Hydrogen
64
What organisms play a vital role in converting nitrogen into a useable form for plants
Bacteria
(without bacteria, Nitrogen would become a limiting factor in ecosystems)
65
What are the two nitrogen-fixing bacteria called?
Azobacter and Rhizobium
66
What do nitrogen-fixing bacteria contain to carry out the Haber process
The Enzyme Nitrogenase, which catalyses the combination of atmospheric nitrogen with Hydrogen to produce Ammonia, which can be absorbed by plants
67
What is Nitrogen fixation
the fixing of nitrogen to hydrogen to form ammonia, which can be absorbed by plants (hater process)
68
Where does the Azobacter bacterium live and what does it do
Lives in soil
Nitrogen Fixation
69
Where does the Rhizobium bacterium live and what does it do
Lives in Root nodules
nitrogen fixation
70
What are Root nodules
Growths on the roots of leguminous plants such as peas beans and clover
71
What relationship do Rhizobium and plant have and why
Symbiotic/ mutualistic
Plant gains amino acids from bacteria when the fix nitrogen into ammonia
Bacteria gains carbohydrates produced by the plant during photosynthesis which is used as an energy source
72
How do plants maximise their benefit with colonies of Rhizobium
Reward and Punishment
Beneficial colonies receive extra carbohydrates
Less-productive bacteria's supply of carbohydrates is cut off and that starves the nodule to death
(Natural selection)
73
What is Nitrification
The process by which ammonium compounds in the soil are converted into Nitrogen-containing molecules that can be used by plants
74
What type of reaction is nitrification and what type of soil can it only occur in
Oxidation reaction
Well-aerated soil
75
What are the two steps in Nitrification
Nitrifying bacteria (eg. Nitrosomonas) oxidise ammonium into nitrites (NO2-)
Nitrobacter oxidises nitrites into Nitrates (NO3-)
76
What is the formula for a Nitrite
NO2 -
77
What is the formula for a Nitrate
NO3 -
78
What property of Nitrate ions means that they enter plants easily
Soluble
79
What is Denitrification
In the absence of oxygen, Denitrifying bacteria convert nitrates in the soil back to nitrogen gas
80
What are the conditions in which denitrification takes place
An oxygen deficient (anaerobic) environment eg. Waterlogged soils
81
What do the Bacteria use the Nitrates for in denitrification
Source of energy for respiration, releasing N2(g)
82
What is ammonification
The process by which decomposers convert nitrogen-containing molecules in dead organisms, faeces and urine into ammonium compounds
83
What are the two types of bacteria involved in Nitrification
Nitrosomonas (NH3 -> NO2 -)
Nitrobacter (NO2 - -> NO3 -)
84
CARBON CYCLE
PAGE 619
85
Why do CO2 levels fluctuatee throughout the day?
Photosynthesis only takes place during the light - removing carbon dioxide form the atmosphere
Respiration happens constantly, releasing set volume of CO2
Therefore CO2 levels are higher during the night than in the day
86
How can carbon fluctuate during the seasons
CO2 levels are lower during a summers day than a winters day, as photosynthesis rates are higher
87
Why have global atmospheric carbon dioxide levels increased significantly over the last 200 years
Combustion of fossil fuels, which has released CO2 back into the atmosphere from carbon that had been trapped below the earths surface for millions of years
Deforestation - removed lots of photosynthesising biomass from earth, so less CO2 is removed. Some forests are cleared by burning, releasing more CO2
88
Why is CO2 a greenhouse gas
Increased levels of CO2 traps more thermal energy (heat) in the atmosphere
89
How does the amount of CO2 dissolved in the seas and oceans affect temperature
Higher temperature - less gas is dissolved, more is released into atmosphere, contributing to global warming
positive feedback loop
90
How can carbon dioxide level variation be measured over million-year scales
Sample taken deep within a glacier eg. Antarctic glaciers
Air bubbles trapped in ice reflect composition of atmosphere at that point of time
Analysed to reveal composition of atmosphere
91
State the main differences between a decomposer and a detritivore
Detritivores break down organic matter into small pieces, providing a larger surface area for decomposers to act on
detritivores carry out internal digestion whereas decomposers carry out external digestion
92
State and explain there ways in which atmospheric CO2 levels increase
Respiration carbon dioxide is released as a waste product of respiration and from the bodies of dead organisms through respiration of decomposers
Combustion burning of forests/fossil fuels releasing carbon dioxide as a waste product
Deforestation fewer trees and plants mean less carbon dioxide is removed from the atmosphere
93
Describe what is meant by saprobiotic nutrition
When a decomposer obtains its energy from dead organisms
by the process of external digestion/process
94
Explain how the scientific community have produced evidence that atmospheric carbon dioxide levels have varied over time
Ice core samples are collected from glaciers which have existed for many (tens/hundreds of) thousands of years
air bubbles trapped within these glaciers are representative of the atmosphere at a point in history
gas analysis of trapped air bubbles reveals atmospheric composition at this point in history
95
What is Succession
The process by which ecosystems change over time
96
Why does succession occur
Due to changes to the environment causing plant and animal species to change
97
What is primary succession
Occurs on an area of land that has been newly formed or exposed such as bare rock.
There is no soil or organic material present to begin with
98
What is secondary succession
This occurs on areas of land where soil is present, but it contains no plant or animal species.
Eg. Bare earth that remains after a forest fire
99
When does primary succession occur
When volcanoes erupt, depositing lava, lava cools and solidifies creating igneous rock
Sand is blown away by wind or deposited by the sea to create new sand dunes
Silt and mud are deposited at river estuaries
Glaciers retreat depositing rubble and exposing rock
100
What is a serial stage (or a sere)
A step of succession
101
What can be found at each seral stage which change abiotic factors such as the soil to make it more suitable for the subsequent existence of other species
A key species
102
What are the main seral stages
Pioneer community
Intermediate community
Climax community
(pg 621)
103
What is a pioneer species
The first species to colonise an inhospitable environment
104
How do pioneer species arrive at the inhospitable environment
As spores or seeds carried by the wind from nearby land masses
or Droppings of birds or animals passing through
105
What is an example of a pioneer species
Algae or Lichen
106
What are some adaptions pioneer species have to enable them to colonise the bare environment
Ability to produce large quantities of seeds or spores, which are blown by the wind and deposited on the 'new land'
Seeds that germinate rapidly
Ability to photosynthesise (only factors would be light, rainfall and air)
Tolerance to extreme conditions
Ability to fix nitrogen from the atmosphere, so adding to the mineral content of the soil
107
What is humus
The organic component of the soil when organisms of the pioneer species die and decompose
108
How is an intermediate community formed
Weathering of the bare rock produces particles that form the basis of the soil, which alone cannot support other species]
When organisms of pioneer species die and decompose, small organic products are released into the soil - Humus
Soil becomes able to support the growth of a new species of plant - secondary colonisers - supported by nitrates in soil and their ability to retain water
Arrive as spores or seeds eg. moss, provides source of food for animals
109
What is an example of a secondary coloniser
Moss
110
What are tertiary colonisers
Species that will arrives the environmental conditions continue to improve
111
What is an example of a tertiary coloniser
Fern
112
What are some adaptions of tertiary colonisers
Thick waxy cuticle to reduce water loss
HOWEVER
Gains water and mineral salts from soil
113
What happens at each stage of the intermediate community seral stages
Rock continues to be eroded
Mass of organic matter increases
Organisms decomposing contribute to a deeper, more nutrient-rich soil, retains more water
Allows for flowering plants such as grasses, shrubs and finally trees to grow
Plant and animal species are better adapted to the ecosystem, often outcompeting the species that were previously present
114
What is the final seral stage called
Climax Community
115
What are features of a climax community
Stable state - little change over time
A few dominant plant and animal species
A decrease in biodiversity from mid-succession due to dominant species outcompeting pioneer and other species
116
What are primary consumers in animal succession and why
Insects and worms, first to colonise an area as they consume and shelter in the mosses and lichen
117
Analogy for succession
Domino falling
Momentum needed for one to fall but eventually they all follow
118
What is plagioclimax
When succession is stopped artificially, by human activities
119
What are the some examples of deflected succession
Grazing and trampling of vegetation by domesticated animals
Removing existing vegetation to plant crops (crop becomes final community)
Burning as a means of forest clearance (can lead to an increase in biodiversity as it provides space and nutrient rich ash for other species to grow)
ALL AGRICULTURE
120
READ SUCCESSION ON A SAND DUNE - 624
121
State the difference between a climax community and a plagioclimax community
Climax community is the final stage of succession whereas plagioclimax community is the final stage of succession as deflected by humans or some other outside factor
122
Describe the difference between primary and secondary succession
Primary succession occurs on bare rock/sand without soil
whereas secondary succession takes place where soil is present but the area contains no plants or animals
123
State and explain the common developments that occur in succession in any ecosystem?
Abiotic conditions/non-living environment becomes less hostile as soil forms when organisms decay/ soil becomes more nutrient-rich/ soil retains more water
increased biomass supported
124
What is the distribution of organisms
Refers to where individual organisms are found within an ecosystem
125
What factors affect distribution of organisms
Organisms are found where abiotic and biotic factors favour them, so their survival rates are high and there are plentiful resources and low predation
126
How can distribution be measured
Belt transect
127
What is the abundance of organisms
The number of individuals present of a species present in an area at any given time
128
How would you estimate plant abundance
usually use a quadrat
Random sampling
Number of individuals/area of sample
can be scaled up
129
What method is used to measure animal abundance
Capture-mark-release-recapture
Est. population size = individuals in 1st sample x individuals in 2nd / Number of recaptured, marked individuals
130
What are some equipment that is used to measure animal abundance
Pooter, sweep net, dip net, pitfall trap, Longworth mammal trap etc...
131
What is Simpsons diversity index
D = 1-Sum of (n/N)2
D = Diversity indez
N = Total number of organisms in ecosystem
n= number of individuals in a species
Always a value between 0-1
132
State the difference between the abundance and distribution of organisms
Abundance is the total number of organisms whereas distribution refers to where individuals are found
133
Twenty woodlice captured area and marked and released back into the same sample area. A week later 15 woodlice were found in the sample area of which only two were marked.
A) suggest which piece of apparatus should be used to collect the woodlice
B) Use the Lincoln Index to estimate the woodlouse population
A) Pooter/pitfall trap
B) 20 × 15 / 2 = 150
134
What is the Lincoln index
Number marked in second sample / Total caught in second sample = Number marked in first sample / Size of whole population (N)
135
State and explain one advantage of the following technique is used to measure the distribution of organisms in an ecosystem
A) random sampling
B) non-random sampling
A) Removes sample bias / makes sample more reliable
B) Allows scientist to study how differing abiotic factors may affect the distribution of a species
136
Discuss the limitations of using the capture-mark-release-recapture technique to estimate population size
Doesn’t take into account births/deaths
immigration / emigration
mark may rub off
mark may make animals more visible to predators
animals don’t redistribute evenly
samples taken may not be representative of the whole population
137
PRACTICE SIMPSONS DIVERSITY INDEX
