Topic 5 - On The Wild Side Flashcards
1
Q
What is a biosphere?
A
The part of the Earth and its atmosphere that is inhabited by living organisms.
2
Q
What is the biosphere made up of?
A
Many ecosystems
3
Q
What is an ecosystem?
A
The biotic community together with the abiotic environment that is described as being a functional unit that tends to be fairly self-sustaining.
4
Q
What is a biotic factor?
A
A living factor
5
Q
What is an abiotic factor?
A
A non-living factor
6
Q
What is a habitat?
A
The particular place where a community of organisms is found.
7
Q
What is a population?
A
A group of organisms, all of the same species, and all of whom live together in a particular habitat.
8
Q
What is a community?
A
The total of all populations living together in a particular habitat.
9
Q
What is a niche?
A
The way an organism exploits its environment.
10
Q
What happens if two species that live in the same habitat and have the same ecological niche compete with one another?
A
Sooner or later the better adapted outcompetes the other and it excludes it from the habitat.
11
Q
What determines where a species habit is?
A
A particular species lives in a particular habitat because it is adapted to it, and is able to survive and reproduce there.
12
Q
What are the abiotic factors?
A
- Solar energy input
- Climate
- Topography
- Oxygen concentration
- Edaphic factors
- Pollution
- Catastrophes
13
Q
How is solar energy input an abiotic factor?
A
Light is vital to plants as it is the energy for photosynthesis. Light has a role in initiating some flowering and in some species is required for seed germination. In animals light affects behaviour. Affected by latitude, season, cloud cover and changes in Earth’s orbit.
14
Q
Climate is an abiotic factor. What does this include?
A
Includes rainfall, wind exposure and temperature.
15
Q
Topography is an abiotic factor. What does this include?
A
Includes altitude which affects the climate, slope aspect (which direction the land faces) and drainage.
16
Q
Oxygen concentration is an abiotic factor. Where is this particularly important?
A
In aquatic systems
17
Q
Edaphic factors are an abiotic factor. What does this mean?
A
These are factors that relate to the structure and composition of soil. This includes; soil pH, mineral ion concentration, soil texture, underlying geology of the area.
18
Q
Describe the conditions of sandy soil in relation to edaphic factors.
A
Sandy soil are well drained (dry out easily in drought) but are rarely waterlogged in wet weather.
19
Q
Describe the conditions of clay in relation to edaphic factors.
A
Clay gets easily waterlogged, but retains water well, an advantage in a drought.
20
Q
What types of pollution are there?
A
Air, water and land
21
Q
What are catastrophes?
A
Infrequent events that disturb conditions considerably.
22
Q
Give examples of catastrophes.
A
Earthquakes, floods, volcanic eruptions and fires.
23
Q
What are the biotic factors?
A
- Competition for resources like food, light, water and space which can be interspecific (between species) or infraspecific (within species).
- Grazing, predation, disease and parasitism are all relationships between two organisms where one benefits at the other’s expense.
- Mutualism is a relationship in which both partners benefit.
24
Q
Biotic factors are usually density dependent. What does this mean? Give an example.
A
The effects are related to the size of the population relative to the area available. The larger the population density, the greater the competition for food, space, etc.
25
What controls the abundance and distribution of organisms within a habitat?
A complex interaction of biotic and abiotic factors.
26
What is an anthropogenic factor?
A factor that arises from human activity.
27
How can species survive in a habitat?
Species survive in a habitat because they have adaptations that enable them to cope with both the biotic and abiotic factors in their niche.
28
Describe the process of primary succession.
1) It starting point is a bare ecosystem.
2) Pioneer species, usually lichen, moss or algae which can penetrate the bare surface and trap organic material.
3) Mosses build up more organic matter in the soil, which can then hold water.
4) Over several generations soil begins to form.
5) Development of soil enables seeds of small, shallow-rooted plant species that have reached the habitat to form.
6) Gradually larger and larger plants occupy the ecosystem along with a diversity of animals.
7) Climax community is reached which is a stable and often remains unchanged.
29
Describe secondary succession.
1) On bare soil where an existing community has been cleared, secondary succession occurs --> fire, flood, volcanic eruption.
2) Pioneer species tend to be grasses and fast growing plants.
3) Bare soil does not stay bare for long. Seeds of many species are either lying dominant and others will be brought by the wind or animals.
4) Groundsel is an example of a Pioneer species adapted to take advantage of newly bare soil where there is little or no competition.
30
What are the groundsel adaptations?
- Seeds widely dispersed by the wind
- Rapid growth
- Short life cycle
- Abundant seed production
31
What is deflected succession?
A community that remains stable only because of human activity prevents succession from ruining its course.
32
What are the ways used to deflect succession?
- Grazing
- Mowing
- Burning
33
Give examples of deflected succession.
- Sheep grazing prevents many grasslands from developing into woodlands.
- Dredging (clearing the bed of mud/weeds) a pond or lake prevents the succession from open water to terrestrial woodland. As sediment deposits decrease water depth creating swamp and marshland, and eventually woodland as conditions dry out.
34
What is a Pioneer species?
The first organisms to colonise bare rock.
35
Give examples of pioneer species to primary succession?
Lichen and algae
36
Define primary succession.
Starts in newly formed habitats where there has never been a community before.
37
What is colonisation?
Species which come from another area.
38
What is a climax community?
As succession occurs bigger plants grow which overtime reaches a limit like a rainforest or a normal forest.
39
What does the climax community depend on?
- Climate
- Soil
- Species
40
What is a dominant species?
The dominant species of a community is the one that has an overriding influence over the rest of the plant, microbe and animal species. Several species can share the role of dominant/c0-dominant. Dominant species is usually the largest species in the community.
41
As succession progresses, what happens to the number of niches and species?
The number of niches and species increases.
42
What happens to the biodiversity as succession progresses?
The biodiversity of gets lower as dominant species outcompete other species.
43
Are all climax communities full of trees?
No. There are areas where succession has occurred yet the conditions are not suitable for trees to grow e.g. Tundras.
44
What is primary productivity?
The rate at which the energy is incorporated into organic molecules in an ecosystem.
45
What are autotrophs?
Organisms that can make their own organic compounds from inorganic compounds (they make their own food).
46
What are examples of autotrophs?
Green plants, algae and some bacteria.
47
What is a photosynthetic autotrophs?
An organism that gets its food from photosynthesis by using light energy and transferring it into chemical energy.
48
What is a chemosynthesis autotrophs?
Organisms that can make organic molecules using energy released from chemical reactions.
49
What are the types of autotrophs?
- Photosynthetic
| - Chemosynthetic
50
What is the word equation for photosynthesis?
Carbon dioxide + water ---> Glucose + Oxygen
51
What is the balanced symbol equation for photosynthesis?
6CO2 + 6H2O ---> C6H12O6 +6O2
52
Why are the products of photosynthesis at a higher energy level than the reactants?
More energy is required to break the bonds within carbon dioxide and water compared to the energy released when glucose and oxygen are formed.
53
When energy is required in a cell what happens to the hydrogen?
The hydrogen stored in the carbohydrate reacts with oxygen during respiration releasing energy.
54
How is hydrogen released from water?
Photolysis which uses light energy to split the strong OH bond in water.
55
How is hydrogen stored in carbohydrates?
Hydrogen reacts with carbon dioxide which 'stores' the hydrogen. Carbon dioxide is reduced to form the carbohydrate fuel glucose, which can be stored as starch or used to make other organic molecules such as cellulose.
56
Using enzymes what is glucose converted into?
- Starch
- Cellulose
- Fats
- Amino acids/proteins
- Nucleic acids
57
What are the two photosynthesis reactions?
- The light-dependent reaction
| - The light-independent reaction
58
What is the light dependent reaction?
These reactions use energy from the light and hydrogen from photolysis of water to produce reduced NADP, ATP and the waste product oxygen. The oxygen is either used directly in respiration or released into the atmosphere.
59
What is the light independent reaction?
These reactions use the reduced NADP and ATP from the light-dependent reactions to reduce carbon dioxide to carbohydrates.
60
What is the loss of reactions known as?
Oxidation
61
What is gaining electrons known as?
Reduction
62
A substance in an oxidised form has ... electrons
Lost
63
A substance in a reduced form has ... electrons?
Gained
64
What is the co-enzyme NADP?
It acts as an electron carrier.
65
Can a hydrogen ion be used in reduction?
No because it is a proton and does not carry an electron. Either a hydrogen atom or electron can carry out reduction.
66
Do the CO2 and H2O have direct contact?
Carbon dioxide and water never come into direct contact during photosynthesis. Instead the hydrogen, electrons and energy needed for the reduction (gaining of electrons) of CO2 are transferred indirectly using reduced NADP and ATP.
67
What are the two types of chlorophyll molecules?
PSI and PSII
68
What is the difference between the photosystems?
- Oxidise different sources of the low-energy electron supply
- Deliver their electrons to different places
- Respond to different wavelengths of light
69
What are electron carriers?
Molecules that are capable of accepting one or two electrons from one molecule and donating them to another in the process of electron transport. As the electrons are transferred from one electron carrier to another, their energy level decreases, and energy is released.
70
What is an electron transport chain?
An electron transport chain is a series of redox reactions that transfer electrons from one electron carrier molecule to the next.
71
How does NADP become Reduced NADP?
The electrons from the electron transport chain, which have lost the majority of their energy to synthesise ATP, and also the hydrogen ion form the photolysis of water, which bind to the NADP to form reduced NADP.
72
What is photophosphorylation?
In the process of photosynthesis, the photophosphorylation of ADP to form ATP using light energy.
73
Describe the process of the light dependent reaction?
When light is absorbed by PSI and PSII, the following events occur:
1) Energy from light (protons) raises two electrons in each chlorophyll molecule to a higher energy level.
2) The electrons leave the excited chlorophyll molecules and pass along a series of electron carrier molecules which are embedded in the thylakoid membranes. These molecules form the electron transport chain.
3) The electrons from PSII chlorophyll pass from carrier to the next in a series of oxidation and reduction reactions in which energy is lost.
4) Energy is used in the synthesis of ATP (photophosphorlyation)
5) Electrons from PSII replace those lost from PSI.
6) Electrons lost from PSII must also be replaced.
7) Within the thylakoid space an enzyme catalyses the splitting of water (photolysis) which produces oxygen gas, hydrogen ions and electrons. Electrons replace those that were emitted from the PSII.
8) The electrons from the PSI chlorophyll which were passed along the transport chain combine with the co-enzyme NADP and hydrogen ions -> forms reduced NADP.
74
What is a photosystem?
Either of two biochemical systems active in chloroplast that are part of photosynthesis.
75
What is the role of a photosystem?
Each photosystem plays a key role in capturing the energy from sunlight by exciting electrons.
76
Where does the light-independent reaction take place?
It takes place in the stroma of the chloroplast
77
What is the function of the NADP?
NADP acts as a hydrogen carrier; using a carrier prevents the hydrogen reacting with the oxygen released by photolysis.
78
Describe the process of the light-independent reaction/Calvin-cycle.
1) CO2 combines with a 5 carbon compound called ribulose bisphosphate (RuBp)using the enzyme ribulose bisphosphate carboxylase (RuBISCO).
2) An unstable 6 carbon compound is formed which immediately breaks down into two 3-carbon compounds, glycerate 3-phosphate (GP)
3) This 3 carbon compound is reduced to a form a 3 carbon sugar called glyceraldehyde 3-phosphate (GALP) using energy from the ATP and the hydrogen comes from the reduced NADP.
4) Two out of every 12 GALPs formed are involved in the creation of a carbon sugar (hexose) which can be converted to other organic compounds (amino acids/lipids).
5) Ten out every 12 GALPs are involved in the reaction of RuBP. The ten GALP molecules rearrange to form 6 5 carbon compounds which are then phosphorylated using ATP to form RuBP.
79
What are the cells in the middle layer of leaf tissue?
Mesophyll
80
What are on the surface of the leaves that let in carbon dioxide and let oxygen diffuse out?
Stomata
81
What does a palisade mesophyll cell contain?
As many as 50 chloroplasts.
82
What are the structures within a chloroplast?
- DNA loops
- Inner membrane
- Outer membrane
- Stroma
- Granum
- Thylakoid space
- Thylakoid membranes
- Starch grains
83
What is the function of the DNA loops within the chloroplast?
They are made up of genes which makes proteins
84
What is the function of the inner membrane of the chloroplast?
It contains transporter molecules which move substances in and out of the cell.
85
What is the function of the outer membrane?
It allows freely permeable molecule such as CO2 and H2O.
86
What is the the stroma?
It is the fluid surrounding the thylakoid membranes
87
What is the function of the stroma?
It contains all the enzymes needed to carry out light-independent reactions.
88
What is the thylakoid membrane?
A system of interconnected flattened, fluid filled sacs. The membrane contains the chlorophyll and electron carrier proteins which are embedded.
89
What is the function of the thylakoid membrane?
It is where the light-dependent reaction takes place due to the chlorophyll and electron carrier proteins embedded in the membranes.
90
What is the thylakoid space?
Fluid within the thylakoid membrane sacs.
91
What is the function of the thylakoid space?
Contains enzymes for photolysis.
92
What are starch grains/what is their function?
Stores the product of photosynthesis
93
What is the granum?
It is a stack of thylakoids joined to one another.
94
What makes the transferring of electrons efficient?
The thylakoid membranes due to the electron carrier proteins embedded in the membrane
95
What does a high concentration of enzymes cause?
A high rate of reaction
96
What is photosynthesis?
Process in which light energy is converted to chemical energy in the form of sugars.
97
What does the glucose from photosynthesis provide? Explain.
- Energy - chemical energy (from the glucose) can be converted through processes like cellular respiration and fermentation which generate ATP.
- Fixed carbon - Carbon dioxide can be incorporated into organic molecules in a process called carbon fixation.
98
What is the ecological importance of photosynthesis?
Humans and other organisms which are heterotrophs cannot convert carbon dioxide to to organic compounds themselves and must eat other organisms. Photoautotrophs are the base of food chains and provide the needed energy and fixed carbons.
99
What do photoautotrophs provide?
- Energy
- Fixed carbon
- Oxygen
100
What is ATP?
It is the most important energy transfer molecule within cells. It moves around the cell from energy-yielding reactions to energy-requiring reactions.
101
How is the third phosphate attached to the ATP?
The third phosphate group is loosely attached (loosely bonded to the second phosphate group) so is easily removed.
102
What happens when the third phosphate group is removed?
ADP (Adenosine diphosphate) forms. The phosphate group becomes hydrated, forming bonds with the surrounding water molecules resulting in lots of energy being released.
103
What is the word equation for ATP in water?
ATP in water ---> ADP + hydrated Pi + Energy
104
What catalyses the breakdown of ATP to ADP?
ATPase
105
How is ATP produced?
ATP is produced from ADP by the addition of inorganic phosphate (Pi). Addition of phosphate to ADP in water is known as phosphorylation. The phosphate must be separated from water which requires energy.
106
What is a fundamental niche?
It describes the abiotic factors in which a species could exist.
107
What is a realised niche?
It describes where it actually does exist; the realised niche takes into account other species.
108
What are primary consumers?
Herbivores/heterotrophs that eat plant material.
109
What are secondary consumers?
Carnivores that feed on primary consumers.
110
What are tertiary consumers?
Eat other consumers. The carnivores at the top of the food chain are sometimes called the top carnivores.
111
What are predators or carnivores?
Animals that kill and eat others animals.
112
What is the order of energy transfer?
Producer -> Primary consumer -> Secondary consumer -> Tertiary Consumer
113
What is a food chain?
A series of organisms each dependent on the next as a source of food.
114
What is a trophic level?
The position a species occupies in a food chain.
115
What is a detritivores?
Primary consumers that feed on dead organic material called detritus.
116
Name examples of detritivores.
- Woodlice
- Earthworm
- Freshwater shrimp
117
What are decomposers?
Species of bacteria and fungi that feed on the dead remains of organisms and animal faeces. They secrete enzymes and digest their food externally before absorption takes place.
118
What is the importance of decomposers and detritivores?
They play an important role in the recycling of organic matter from dead remains and waste.
119
What is the productivity of an ecosystem determined by?
Productivity of an ecosystem is determined by how much energy is captured by the producers and how is transferred to the higher trophic levels.
120
Not all light energy is absorbed by the leaf, what happens to the rest of the light energy?
- Energy not absorbed by chlorophyll but used in evaporating water from leaves.
- Transmitted straight through leaf
- Reflected
121
What are the limiting factors that reduce the rate of photosynthesis?
- Temperature - Cooler conditions reduce the rate of photosynthesis
- CO2 concentration
- H2O concentration
122
What is Gross Primary Productivity (GPP)?
The rate at which energy is incorporated into organic molecules.
123
What are the units for GPP?
KJm-2y-1 or MJha-1y-1
124
How do you calculate the percentage efficiency of photosynthesis?
(GPP / Amount of energy from light arriving at plant surface) x 100
125
What is the net primary productivity?
The rate at which energy is transferred into the organic molecules that make up the new plant biomass.
126
How do you calculate NPP?
NPP = GPP - R
127
How do you calculate GPP?
NPP + R
128
Why is only 2-10% of energy transferred to new biomass from producers to primary consumers? Explain each reason.
- Not all the available food gets eaten -> only parts of an organisms are eaten. For example, some parts of plants such as roots, twigs or parts protected by thorns or spines which are not eaten.
- Some undigested food remains in faeces -> e.g. Mammals struggle to break down cellulose (no enzymes to break it down). So the energy it contains is not transferred to the primary consumers.
- Much of the food absorbed by the consumer is used in respiration -> energy used for movement and chemical reactions in the body and some energy is lost to the environment.
129
Why is the transfer of energy more efficient from primary consumers to secondary consumers rather than producers to primary consumers?
Transfer is more efficient from herbivores to carnivores because most of the herbivore can be eaten by the carnivore and the protein rich diet is easily digested -> less lost in faeces.
130
Other than energy being transferred to the next trophic level where is the other energy transferred to?
It is transferred to the surroundings in respiration and it is transferred to decomposers.
131
Why do food chains rarely have more than 4 or 5 trophic levels?
There comes a point where there is insufficient energy remaining to support another trophic level.
132
What are the three pieces of evidence for climate change?
- Temperature records
- Pollen in peat bogs
- Dendrochronology (tree-ring studies)
133
What is anecdotal evidence?
Evidence from personal memory
134
How do temperature records support climate change?
They show slightly increasing temperature since the 1600s.
135
What is preserved inside peat bogs?
The plant and insect remains that have been preserved.
136
What is peat?
An accumulation of partially decayed organic matter -> mainly the remains of dead plants.
137
What is used to determine the climate conditions of the past using peat bogs?
Pollen because it is particularly well preserved.
138
Why is pollen useful for reconstructing past climates?
- Produce pollen in vast amounts -> lots enter the surface of peat bogs.
- Pollen grains have a tough outer layer that is very resistant to decay.
- Each species of plant has a distinctive type of pollen -> easy to identify.
- Peat forms in layers: the deeper the layer, the older the peat. Carbon-14 dating allows the age of a particular peat layer to be established.
- Each species of plant has a particular set of ecological conditions in which it flourishes best.
139
If pollen is found in a layer of peat from a species that favours warmer conditions, what does this show?
We can infer that the peat was laid down when the climate was warmer.
140
How can dendrochronology be used to show different climate conditions?
Every year trees produce a new layer of xylem vessels by the division of cells underneath the bark. The diameter of the xylem vessels varies. Each year a tree ring is made which can be seen from the xylem vessels which go from big to very narrow, marking the end of the year. By looking at the size of a tree ring it provides information about the weather conditions for that year. A wide ring represents warm and wet conditions, which are favourable for trees. Narrow rings represent dry and cold conditions.
141
How does the size of xylem vessels change across a year?
The vessels produced are wide in spring and become narrow in summer. There is little or no growth in autumn or winter. Therefore they start big and get smaller and smaller marking the end of the year.
142
Does dendrochronology cause deforestation?
No because a core sample is taken from trees preventing the cutting down of trees.
143
Which ring of a tree is the oldest?
The central ring.
144
How do you work out the age of a tree?
By counting the rings (count inwards).
145
How are trees dated?
Experts find common patterns of tree-ring growth that allow cross-dating. They are also carbon dated.
146
What is dendrochronology?
The science or technique of dating events, environmental change, and archeological artefacts by using characteristic patterns of annual growth rings in tree trunks.
147
How do you read a skeleton plot?
The taller the bar, the narrower the tree ring.
148
When do the temperature records date back too?
1650s
149
When do tree-ring studies date back to?
3000 years in some cases.
150
How far back does pollen give us information about climatic conditions?
20,000 years
151
What is the oldest form of evidence used of climate change?
Ice cores
152
How can ice cores be used to determine temperature conditions?
As water freezes, bubbles of air become trapped within ice. The ratio of different oxygen isotopes in the trapped air is measured giving an estimate of the average air temperature when the ice was formed. Carbon dioxide concentrations can also be determined from these bubbles.
153
Describe the changing rainfall patterns in the UK.
- Increased amount of rainfall in the UK winter due to a small increase in the number of wet dats and larger amount of rainfall on those days.
- Decrease in rainfall in the spring.
- Decrease in rainfall in the summer -> fewer wet days and less rain on those days.
154
What is the atmosphere?
Thin layer of gases extending 100km above the Earth's surface, held in place by gravity.
155
Why is the atmosphere important?
The temperature of the Earth's surface would fluctuate between very hot days and very chilly nights. Therefore the atmosphere keeps the Earth's average temperature stable and suitable for living organisms.
156
What is solar radiation in the form of?
Visible and ultraviolet light which is emitted from the sun.
157
What is infrared radiation emitted from?
It is emitted from the earth.
158
What is the stratosphere?
The layer above the earth's atmosphere.
159
What is the troposphere?
The lowest region of the atmosphere, extending from the Earth's surface.
160
Describe what happens to the energy emitted by the sun?
The sun radiates energy, mainly visible light, and the Earth absorbs some of this energy. The Earth warms up and in turn radiates energy back into space as infrared radiation. Some of the infrared radiation is absorbed by gases in the atmosphere which causes the Earth to warm up. Not all the energy emitted from the sun is absorbed; some is reflected by the clouds, some visible radiation is reflected by the Earth, most of the ultraviolet light is absorbed by the ozone layer in the stratosphere.
161
What are greenhouse gases?
The gases in the atmosphere that stop the infrared radiation from escaping.
162
What is the greenhouse effect?
Caused by increased quantities of gases which trap heat from the sun, and cause a gradual rise in the temperature of the Earth's atmosphere.
163
List the greenhouse gases in order of global warming potential (smallest to largest)
- Nitrogen (N2)
- Oxygen (O2)
- Argon (Ar)
- Carbon dioxide (CO2)
- Methane (CH4)
- Nitrous oxide (NOx)
- Chlorofluorocarbons (CCI3F)
164
What is the global warming potential?
Measure of the greenhouse effect caused by that gas relative to the same amount of carbon dioxide over a given time, which is given a value of 1.
165
Why is carbon dioxide associated with having the highest impact on the greenhouse effect?
It is so much more abundant than the more potent greenhouse gases, therefore having the largest effect.
166
How is methane produced?
-Produced by anaerobic decay of organic matter in waterlogged conditions.
-Produced through the decay of the domestic waste in landfill sites and the decomposition of animal waste.
-Produced in the digestive system of animals such as cattle released when they belch or fart.
Produced by the incomplete combustion of fossil fuels.
167
Which of these molecules absorbs more infrared radiation, methane or carbon dioxide?
Methane
168
How could methane emissions be reduced?
- Better waste recycling
| - Using it as a biofuel because when burnt it creates CO2 and water vapour which are less serious greenhouse gases.
169
Why has there been a significant increase in carbon dioxide concentrations in the atmosphere?
It is due to the combustion of fossil fuels.
170
Does an increase in CO2 cause global warming?
There is a strong correlation between temperature and carbon dioxide concentration it is a widely excepted theory that a current rise in global temperatures is due to rising concentrations of greenhouse gases.
171
Define theory.
A well tested and widely excepted idea or principle supported by a great deal of evidence.
172
Why is climate change controversial?
- Science cannot prove theories they can only disprove them. This means if results disprove the idea it is rejected but if results support the idea it does not actually prove it.
- An incomplete knowledge of how the climate systems of our planet work and the data sets used in making predictions about climate change have their limitations. For example there is no way to precisely measure how much carbon dioxide is added to the atmosphere by fossil fuel combustion.
173
What are some people's views on global warming?
Some people believe that the changes in temperature currently observed are part of a natural cycle of climate variations or are due to changes in the Sun's activity.
174
What are the ethical arguments that are often quoted when considering the issue of global warming?
- We all have the right to choose for ourselves whether or not we use fossil fuels to achieve a good standard of living.
- We have a duty to allow others to improve the standard of living (often equated with industrialisation).
- We have a duty to preserve the environment for the next generation.
175
What is extrapolation?
Extending a line on a graph.
176
In extending the line (extrapolation) we make the assumption that
- we have enough data to establish the trend accurately
| - present trends continue
177
Other than carbon dioxide what other factors affect climate change?
- other greenhouse gases, such as methane, CFCs and nitrous oxide
- aerosols which are extremely small particles or liquid droplets found an atmosphere
- The degree of reflection from those parts of the Earth surface that are free of ice and snow
- The fraction of the Earth covered with ice and snow
- The extent of cloud cover
- changes in the Sun's radiation
178
Why are predictions of climate change sometimes incorrect?
- Limited data
- Limited knowledge of how the climate systems work
- limitations in computing resources
- failure to include all factors affecting the climate
- changing trends in factors, for example greater carbon dioxide emissions
179
The changes attributed to climate change can be divided into two categories. What are these categories?
- Changing distribution of species
| - Altered development and life cycles
180
How can climate change affect the distribution of species?
Within any community, some species will cope with the change while others will fare less well. Climate change will therefore cause the balance between species in the community to shift. Some species may benefit from the new conditions and become dominant, while others may be lost from the community altogether due to competition with existing or invading species. If they are mobile or have good seed dispersal they may migrate to more favourable conditions.
181
How can climate change cause the invasion of alien species and what impact does it have?
A particular problem for some communities may be the invasion of exotic or alien animal or plant species from other regions of the world. Species from Mediterranean regions might take advantage of warmer conditions and invade southern England pushing out the current inhabitants. Pests and diseases may also spread to new areas and act to reduce crop yields.
182
How does climate change affect the development of organisms, particularly plants?
Faster photosynthesis equals faster growth. Scientists have established a few degrees of warming will lead to an increase in temperate crop yields, but greater temperature rises could reduce crop yields. The rate of photosynthesis is determined by a number of limiting factors including both carbon dioxide concentration and temperature. In cooler climates where photosynthesis is temperature limited, a rise in temperature will result in faster photosynthesis as the enzyme catalyse catalyse reaction of photosynthesis occurs more quickly. However the situation is a little more complicated because above an optimum temperature plant enzymes work more slowly.
183
What is the ratio known as the temperature coefficient or Q 10?
It mathematically describes what happens to the rate of reaction as temperature increases by 10°C
184
How do you calculate Q 10?
Rate of reaction at temperature T + 10°C / rate of reaction at temperature T
185
How does global warming disrupt the development and life cycles of organisms?
Animals are likely to be affected if the temperature acts as an environmental cue or trigger for their development or behaviour. For example, the egg incubation temperature of some reptiles determines the sex of the offspring. In leatherback turtles, higher temperatures in the nest result in females.
186
What is phenology?
It is the study of seasonal events in the lives of animals and plants, such as the time of flowering or fruiting or the time of egg laying or hatching.
187
How can phenology be an indicator of the impacts of global warming on species?
It has been recognised that the timing of such events is a useful biological indicator of global climate change. Many long-term records exist that allow us to see how much change has been experienced in natural systems, particularly those associated with the onset of spring.
188
What did Darwin observe while on the Galapagos Islands?
- Organisms produce more offspring than can survive and reproduce.
- Numbers in natural populations stay much the same over time.
- He also observed that there is a huge amount of variation within a species.
189
Organisms produce more offspring than can survive and reproduce. Numbers in natural populations stay much the same over time. What did Darwin conclude from his observation?
There is a struggle for existence-competition for survival between members of the same species. As the population increases in size, environmental factors halt the increase. Many individuals die due to predation, competition for food and other resources, or due to the rapid spread of disease resulting from overcrowding.
190
Darwin observed that there is a huge amount of variation within a species. What did he conclude from this?
Those individuals that are best adapted to conditions in their environment are more likely to survive and breed. They have a selective advantage: natural selection is acting and their is survival of the fittest. Individuals with these adapted features will be more common in the next generation. Those organisms that are not well adapted are more likely to die before maturity and so do not produce many offspring. Over a period of time, the character of the species will change to the more adapted form.
191
What is evolution?
A change in allele frequency in the population of organisms over time.
192
What is DNA hybridisation?
When DNA is heated it separates into two components strands as the hydrogen bonds between the base pairs break. If we do this to human DNA and chimpanzee we can then mix them to make a hybrid DNA, made up of a strand of the human DNA and a strand of the chimp DNA. Since chimp and human DNA will have some different base sequences, not all the bases will be able to complimentary base pair. Therefore when heated the hybrid DNA will separate at a lower temperature than pure human or pure chimp DNA. DNA relatedness is therefore measured by the temperature need to denature the hybrid DNA. The more similar the organisms the higher temperature needed to denature the DNA hybrid.
193
What are the forms of molecular evidence that can be used to see how similar two organisms are?
- DNA hybridisation
- DNA profiling
- DNA and protein sequencing
- DNA molecular clocks
194
How can DNA profiling be used to see how closely related two species are in evolutionary terms?
Restriction enzymes cut DNA at specific sequences which produce a series of different sized DNA fragments, which can be visualised as a series of bands or peaks on the DNA profile. The DNA profile of two species can be compared and the more bands on the profile which match the more closely related they are.
195
How can DNA and protein sequencing be used to identify how closely related in evolutionary terms two species are?
By comparing the sequence of bases in DNA or the amino acid sequence in proteins of different species, it is possible to determine how closely related organisms are in evolutional terms. If two species have very few differences in the DNA or amino acid sequence, they evolved from a common ancestor more recently than those organisms with more differences.
196
What are molecular clocks?
The molecular clock is a technique that uses the mutation rate of a species to pinpoint events in evolution. As species evolve, it is assumed that they accumulate random mutations at a regular rate becoming genetically more different. For a given gene, the mutation rate is fairly constant. Evolutionary trees based on molecular clocks can be produced.
197
Define speciation
The formation of a new species.
198
What is an isolating mechanism?
And isolating mechanism is something that prevents successful interbreeding between populations of the species.
199
Define reproductive isolation
Two populations are described as being reproductively isolated when and they are unable to breed with each other or they produce offspring which fail to survive. Reproductive isolation is crucial to speciation because it prevents gene flow.
200
What are the two types of speciation?
- Allopatric speciation
| - Sympatric speciation
201
What is allopatric speciation?
This occurs when populations are geographically isolated from one another, preventing the groups from mating with each other, and so the population becomes reproductively isolated.
202
What is sympatric speciation?
This occurs when the two populations become reproductively isolated in the same environment without any geographical barrier, due to other isolating mechanisms.
203
Explain allopatric speciation
The most common method of speciation is isolation of populations by some geographical feature that prevents a group of individuals from breeding with the rest of the population, such as a high mountain range, a river or a stretch of ocean. Over time, the two groups will become less like each other as they respond to different selection pressures within their local habitats and as random mutations occur. Since mutations will accumulate independently in each population, allele frequencies will change in each. Also, when the population is relatively small, there will be random changes in allele frequency called genetic drift. When the members of the two groups meet again, they may not be able to interbreed if these differences are great enough. Once the two populations are unable to breed and produce fertile offspring they are considered to belong to two different species, and there is no reproductive isolation between them (no gene flow).
204
List the forms of sympatric speciation
- Ecological isolation
- Temporal isolation
- Behavioural isolation
- Physical incompatibility
- Hybrid inviability
- Hybrid sterility
205
What is ecological isolation?
The species occupy different parts of the habitat.
206
What is temporal isolation?
The species exist in the same area, but reproduce at different times.
207
What is behavioural isolation?
The species exist in the same area do not respond to each other's courtship behaviour (e.g. flashing pattern in different species of fireflies, mating calls in different frogs species).
208
What is physical incompatibility?
Species coexist, but there are physical reasons that prevent them from copulating (e.g. size or shape of genitals in some insects).
209
What is hybrid inviability?
In some species, hybrids are produced, but they do not survive long enough to breed.
210
What is hybrid sterility?
Hybrid survive to reproductive age but they cannot reproduce (e.g. mules are a cross between donkeys and horses but cannot reproduce).
211
The carbon cycle is no longer in balance. What are the two main factors responsible for this?
- Combustion of fossil fuels
| - Deforestation
212
Other than the combustion of fossil feels and deforestation what else increases the amount of CO2 in the atmosphere?
- Volcanoes may release CO2 - an increase in volcanic activity in the future could make a big difference
- An increase in acid rain might increase the rate at which CO2 is released by erosion of limestone
213
What are the ways in which we can maintain the carbon dioxide balance?
- Use of sustainable resources including biofuels
| - Reforestation
