Topic 5: On the Wild Side Flashcards
(93 cards)
1
Q
5.1) Ecosystem
A
All the organisms living in a particular area, known as the community, as well as all the non-living elements of the particular environment (e.g. climate, nutrients being cycles etc.)
2
Q
5.1) Community
A
All of the populations of all the organisms living in a particular habitat at a particular time.
3
Q
5.1) Population
A
All of the organisms of a particular species living in a particular habitat at a particular time.
4
Q
Biotic Factors
A
Living factors such as: predators food availability, parasitism or disease, which control the numbers and distributions of organisms in a habitat.
5
Q
Abiotic Factors
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Non-living factors such as: light, oxygen or moisture levels, and temperature, which controll the numbers and distributions of organisms in a habitat.
6
Q
5.3) The niche concept
A
Each species has a particular role in its habitat, called its ecological niche. This consists of its biotic and abiotic interactions with the environment. Species distribution and abundance within a habitat will depend on the number and type of ecological niches available within the habitat.
The niche concept states that only one ogranism can occupy each niche in a given habitat at a given time - if two or more species have a niche that overlaps, the best adapted will out-compete the others in surviving to reproduce.
7
Q
CORE PRACTICAL 10) Ecology of a habitat
A
IV: Chosen abiotic factor (e.g. light intensity)
DV: Abundance of chosen species
CVs: Intervals on transect, size and type of quadrat used
Method:
1) Place transect down at a site with an obvious gradiant in an abiotic factor. Select a species that changes in abundance along the gradient.
2) Place quadrat at 1meter intervals along the transect.
3) Record the % cover for the chosen species. A square should only be counted if more that 1/2 of it is covered.
4) At each co-ordinate a measure of the IV should be taken. I.e use a photometer to measure light intensity at each coordinate.
5) Plot a graph of % cover against the chosen IV to investigate a correlation.
6) Carry out a statistical test on collected data
Risks assessment
Biohazard - allergies; soil; bacteria; contamination; wash hands after
Slippery surfaces; slip hazrad; wear appropriate footwear; don’t run
8
Q
Succession
A
Succession is the process by which an ecosystem changes over time. The biotic conditions change as the abiotic conditions change.
9
Q
Primary sucession
A
Occurs when an area previously devoid of life is first colonised by communities of organisms. This happens on land that’s been newly formed or exposed, e.g. by a volcanic eruption to form a new rock surface, or where sea level has dropped exposing a new area ofv land. There’s no soil or organic material to start with, e.g. just bare rock.
10
Q
Secondary succession
A
This occurs with existing soil that is clear of vegetation. This may occur after an event such as a forest fire or where a forest has been cut down by humans.
11
Q
Stages of succession
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1) Seeds and spores are blown by the wind and begin to grow. The first species to colonise the area are called pioneer species.
2) Pioneer species, e.g. lichens and marram grass, are specially adapted to cope with the harsh conditions e.g. there’s no soil to retain water.
3) The pioneer species change the abiotic conditions, as they grow they release acids that break down rocks. When they die, the organic matter of their remains decomposes, mixes with sediment from the fragmented rocks, and begins to form soil- As pioneer species die, microorganisms decompose the dead organic material (humus). This forms a basic soil.
4) The basic soil retains water, making conditions less hostile for new organisms, like grass and small plants, with different adaptions to move in and grow.
5) When these organisms die and decompose more organic material is added to the soil making it deeper and richer in minerals.
6) Larger plants like shrubs can then start to grow.
7) Some species make change the environment so that it becomes less suitable for previous species and so they are outcompeted by new species.
8) As succession goes on biodiversity increases.
9) Climax community is reached - the ecosystem is supporting the largest and most complex community of organisms it can - it’s in a steady state.
Secondary succession happens in the same way but just begins at a later stage.
12
Q
plagioclimax
A
When succession is stopped artificially, usually due to human activity e.g. lawnmowers prevent the growth of shrubs and trees in grassy fields.
13
Q
Global warming
A
A term used to describe a gradual increase in the average temperature of the Earth’s atmosphere and surface over a significant period of time.
14
Q
Climate Change
A
When the weather conditions in a region change significantly over a long period of time. Climate change can be caused by global warming.
15
Q
Evidence for climate change
A
- Records of carbon dioxide levels
- Temperature records
- Pollen in peat bogs
-Dendrochronology
16
Q
Records of carbon dioxide levels
A
- Atmospheric CO2 levels have fluctuated throughout earth’s history (due to events like volcanic erruptions), but recent increases have been faster + greater than ever. Together with the knowledge of CO2 as a greenhouse gas, there is strong evidence that CO2 released by human activities since the industrial rev. is contributing to increased global temps.
- CO2 levels can be measured by analysing the gas composition of bubbles in ancient ice cores. Ice is deposited as water freezes over time, so the deeper the ice, the older it is.
17
Q
Temperature records
A
- Thermomenters can be used to measure air temperature, and therometer records from different places around the world over extended periods of time can be put together to show average global temperatures change over time.
- Av. global temp records since the mid-1800s show some temp fluctuations but an overall trend of increasing temp overtime. This time periods corresponds with the time during which humans have been burning fossil fuel thus increasing CO2 into the atmosphere.
18
Q
Pollen in peat bogs
A
- under waterlogged and acidic conditions (which are poor for enzyme activity and therefore decomposition), partly decomposed dead plant metter accumulates, forming peat (the place where peat accumulates = a peat bog).
- Peat builds up in layers. Top layers = more recent, lower layers = older.
- Peat cores can be taken from a bog and the layer analysed to assess the pollen grains that have been perserved in the peat bogs.
- Because pollen grains are unique to each plant species, the plant species growing around the bog at dif. points in time can be indentified. Dif. plant species grow under dif. climactic conditions, thus we can use their presence to measure the climate of that time.
19
Q
Dendrochronology
A
- The study of tree rings as the size of tree rings in affected by temperature.
- Most trees produce one ring in their trunks every year and the thickness of the ring depends on the climate when the ring was formed - when it’s warmer the rings are thicker ( because the conditions for growth are better).
- Scientists can take cores through tree trunks then date each ring by counting them back from when the core was taken. By looking at the thickness of the rings, they can see what the climate was like each year.
20
Q
Sampling techniques
A
Frame Quadrats are normally 1m2 square frame divided into 100 squares. Each square represents 1% of the total area of the quadrat.
If an individual covers more than half of a square, it is counted as representing 1% of the quadrat.
Point quadrats is a horizontal bar on two legs with a series of holes at set intervals along its length. Pins are dropped through the wholes and every plant that each pin touches is recorded.
Quadrats are used to count the population size within a large area
Random sampling
Applied by dividing the area of interest into a grid and labelling the grid with coordinates. A random number generator provides a set of random coordinates. The quadrats can be placed using the coordinates.
Systematic sampling is a non-random sampling method where different areas within a habitat are sampled at regular intervals to avoid bias. It allows us to study of how species distributions change across different areas within a habitat.
Transects
A transect is a line across a habitat, usually placed using a tape measure. Transects are used when there is a change, or gradient, in abiotic conditions across the habitat and how this effects the abundance or distribution of a species across the environment (e.g. how abundance changes from open field to forest).
Line transect
A line transect records the species that makes contact with the tape measure at regular intervals along the transect.
Belt transect
A belt transect uses quadrats.
Quadrats are placed at regular intervals along the transect.
An abundance of different species in the quadrat can be measured by percentage cover or frequency.
Sample at least 10 times
21
Q
5.13) What is meant by anthropogenic climate change and what causes it?
A
Anthropogenic climate change is the term forclimate change caused by human activities.
It is thought that increasing levels of greenhouse gases (CO2 and methane) are entering the atmosphere as a result of human activities, leading to the greenhouse effect and increased rates of atmospheric warming.
22
Q
5.13) The greenhouse effect
A
- Short-wavelength UV radiation from the sun passes through the Earth’s atmosphere and is reflected from the Earth’s surface.
- The reflected rays are of a longer wavelength (infrared radiation (heat)). While some IR passes back through the atmosphere into space, some is absorbed by greenhouses gases, which re-emits heat in all directions so, trapping it in the Earth’s atmosphere.
- As a result the Earth’s atmosphere and the Earth’s surface become hotter.
23
Q
5.13) Carbon dioxide
A
CO2 is released into the atmosphere by:
- fossil fuel combustion
- Damaging or destroying carbon sinks (trees (deforestation), soils(oil degredation), peatbogs (peat harvesting), the ocean (ocean warming)).
Atmospheric CO2 has fluctuated throughout history due to events like volcanic erruptions. But since the Industrail rev. in the 1700s (when fossil fuel combustion began) they have been on the rise. There’s a strong correlation between increasing CO2 level since the IR and increasing global temp, providing evidence for the role of human activities in gloabl warming.
24
Q
5.13) Methane
A
Methane is produced naturally by some decomposing bacteria but levels have risen significantly in recent years due to human activties:
- released from the guts of ruminant mammals such as cattle. Intesive farming of animals has greatly increased their contribution to atmospheric methane.
- Landfill sites release methane when organic matter such as food waste decomposes.
- Extraction of fossil fuels from underground.
- Anearobic bacteria in waterlogged rice paddy fields
- Methane is trapped in ice, so as the Earth’s temp increases and Icy ground/glaciers begin to melt, natural stores of methane are released into the atmosphere.
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5.14) How can existing data related to global warming be used?
- It is possible to use existing data relating to global warming to make predictions about global temperatures in the future
- Using data in this way is known as **extrapolating** from data. Extrapolated data can be used to produce **models that show how the climate may change in the future**
- Global warming predictions can be used to: plan for the future e.g. flood defences and Encourage people to change their activities e.g. burn less fossil fuels.
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5.14 i) The Intergovernmental Panel on Climate Change (IPCC)
A group of climate scientists around the world that has **used existing data to extrapolate how global temperatures might change in the future under different human activity scenarios** producing **projection graphs**. e.g:
- If humans manage to immediately begin reducing fossil fuel use, global temperature change could be limited to around 1°C
- If humans do nothing to change their fossil fuel use, global temperature increase may exceed 4°C
The IPCC data can be added to other **computer models** on climate change to see how different parts of the world might be affected under the different scenarios
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5.14 ii) limitations to models for climate change based on extrapolated data
- The IPCC has produced models based on several emissions scenarios, and we do not know which of these scenarios is **most likely or most accurate**
- We do not know whether **future technologies** will be successful at removing greenhouse gases from the atmosphere.
- It is unknown exactly how atmospheric gas concentrations might affect global temperatures
- Global climate patterns are **complex** (they invlove a complex feedback system) and therefore predictions are difficult
- It is possible that a certain **tipping point** in global temperatures could lead to a **sudden acceleration** in global warming e.g. permafrost melting may cause a sudden increase in atmospheric methane
- We don't know exactly how factors other than human activities (**natural causes**) may affect climate in the future e.g. a volcanic eruption could increase ash in the atmosphere, reflecting radiation back into space and cooling the earth
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5.15) Effects of Climate change
Global warming can cause other types of climate change including:
1. **Changing rainfall patterns** This can affect the distribution of animals if they have to relocate due to flooding. The life cycles of organisms may be disturbed if their normal breeding sites are flooded or experiencing drought.
2. **Changing seasonal cycles** This can be problematic where organisms rely on each other for survival. (e.g. if caterpillars are hatching earlier in spring, hatching chicks miss the period when caterpillars are most abundant, and could starve.)
These changes will affect:
- The **development** of organisms (e.g. due to changes in food availability)
- The **life-cycles** of some animals (e.g. growth and reproduction is dependent on certain factors (i.e. temp and food availability), if these change so does the organisms ability to grow and reproduce).
- The **distribution of species** (If they aren't adapted to changing conditions, they may have to relocate to areas with more suitable conditions, otherwise they may die out.) This increases interspecific competition.
Changing temps affect enzyme activities
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5.16) What is the effect of temperature on enzyme activity and its impact on organisms?
An increase in temperature (due to global warming) will also affect enzyme activity. Initially, as temp increases the rate of reaction also increases. The rate of formation of enzyme-substrate complexes increase as the **kinetic energy** of molecules increases, leading to more frequent **collisions**. However, the rate of reaction decreases above the **optimum temperature**, as the enzyme molecules vibrate more, which breaks some of the **bonds** that hold the enzyme in shape. As a result, the shape of the **active site** changes, thus the enzymes become **denatured**.
Affects on organisms' Life cycles, development, and distribution:
Enzymes controll organisms metabolic reactions.
- An **increase** in temp, means that metabolic reactions will **speed up**, so their **rate** of **growth** will **increase**. This also means they'll **develop** and **progress** through their **life-cycle faster**.
- If the temp becomes **too high** for the organism, their metabolic reactions will **slow down**, so their **rate** of **growth** will **decrease**. This means they'll **progress** through their **life cycle slower**.
- GW will also affect the **distribution** of species - all species exist where their **ideal conditions** for survival are (e.g temp). So when these conditions change, they will have to move to a new area where conditions are better. If they can't move they may die out.
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Measuring abiotic factors
Temp - **thermometer**
Rainfall - **rain gauge**
Humidity - **hygrometer**
O2 availably in aquatic habitats - **oxygen sensor**
Light intensity - **Light meter**
Ph of soil - A sample of soil is mixed with water and an **indicator liquid** that changes colour depending on the Ph (measured against a chart).
Moisture content - The mass of soil is measured before and after being dried out in an oven at **80-100dc** (until it reaches a constant mass). The difference in mass as a % of the original mass of the soil in then calculated (this is the water content of the soil). Or use a **moisture probe**.
Topography
Relief (change in height of land) - take height readings using a **GPS**
Slope angle - **clinometer**
Aspect (direction of slope) - compass
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5.20) Why is there controversy among scientific conclusions as to the degree to which humans are affecting climate change?
The scientific consensus reached on climate change may depend on who is reaching the conclusions.
For example:
- Sceintists working for an oil company may be more likely to say humans aren't causing climate change because this would help keep their sales high
- Scientists working for a renewable energy company may be more likely to say that humans are cause climate change because this would increase their sales.
Ideas are validated and conclusions drawn via scientific conferences and publications in peer-review scientific journals, however conclusions scientists reach can be affected by the reliability of data, which is sometimes affected by bias.
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5.20) There is contoversy over what actions should be taken to reduce climate change.
a) Suggest one group of people who might support increasing the use of biofuels to reduce global warming and one group who might oppose the increase of biofuel.
b) Suggest one group of people who might support increasing the use wind turbines to reduce global warming and one group who might oppose the increase of wind trubines.
Increasing the use of biofuels:
- **Farmers** might support this strategy as some governments fund the farming of crops for biofuels.
- **Drivers** might suppoert this strategy as biofuels are usually cheaper than oil-based fuels.
- **Consumers** might oppose this strategy as it requires farmland, which could cause food shortages.
- **Conservationists** might oppose this strategy as forests have been cleared to grow crops for biofuels.
Increasing the use of wind turbines:
- **Companies** that make wind turbine would support this strategy as their sales would increase.
- **Environmentalists** would suppoert this strategy as wt's produce electricity without increasing atmopsheric co2 conc.
- **Local comminities** might oppose this strategy as some ppl think wt's reun the landscape.
- **Bird conservationists** might oppose this strategy as many birds have been killed flying into wind turbines.
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5.21) How can knowledge of the carbon cycle be applied to methods to reduce atmospheric levels of CO2?
The carbon cycle explains how carbon compounds are recycled between organisms and the atmosphere. Scientists can use this to come up with ways to reduce atmospheric CO2 concentration, either by:
- decreasing the amount of CO2 going into the atmopshere (due to respiration and combustion). Biofuels prevent combustion of fossil fuels.
- Increasing the amount of CO2 being taken out of the atmosphere (by photosynthesis). Reforestation adds more plants, increasing photosynthesis.
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5.22) Biofuels
Biofuels are fuels produced from **biomass material** that is or was recently living.
Atmospheric Co2 levels can be reduced by growing plants/crops to use as biofuels. These can be **regrown** after harvesting, making biofuels a **substainable** and **carbon neutral** resource (as the CO2 released by burning the fuel is removed from the atmosphere by the plants it is made from).
Limitations:
Requires farmland which could be used to grow food and clears forests which decreases biodiversity.
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5.22) Reforestation
Reforestation is the planting of new tress in existing forests or forests that have be depleted.
More trees means more **CO2 is removed** from the atmopshere by **photosynthesis** and conoverted into carbon compounds to be stored as plant tissues in the trees.
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5.9) Describe the structure of chloroplasts in relation to their role in photosynthesis
Chloroplasts and photosynthesis:
Granum: Light dependent stage
Stroma: Light independent stage
**Flattened organelles**: Provide **large surface area** to increase absorbtion of light.
**Chloroplasts migrate** in response to different light intensity's
Chloroplast structure:
- **Chloroplast envelope**: A double-membrane that surrounds the chloroplast. Keeps the reactants close to the reaction sites and controls want enters and leves the chloroplast.
- **Stroma**: A cytoplasm-like fluid that fills the chloroplasts. It contains the enzymes, substrates, sugars, ribosomes and chloroplast DNA needed for the light independent reaction.
- **Thylakoids**: A series of flattened, fluid-filled sacs. They provide are stacked in layers (grana) to provide a **large surface area** for absorbing light. They also contain chlorophyll to absorb light. Contain electron carrier molecules and lots of ATP synthase in their membranes for for ATP production.
- **Grana**: Stacks of thylakoids, connected by membranes called lamella.
- **Lamella**: Membraneous channels that connect grana, while keeping them apart to increase surface area, which increases rate of light absorption.
- **Photosystems**: Proteins embeded in the the thylakoid membranes that contain photosynthetic pigmentsm, such as chlorophyll, to absorb light energy.
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5.5) Describe the overal reaction of photosynthesis
Photosynthesis requires energy from light to split apart the strong bonds in water molecules, storing the hydrogen in a fuel (glucose) by combining it with carbon dioxide and releasing oxygen into the atmosphere.
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Give the word and symbol equation for photosynthesis
Carbon dioxide + water >>>(light)>>> glucose + oxygen
6CO2 + 6H2O >>>(light)>>> C6H12O6 + 6O2
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5.6) ATP as an enery source
- ATP (adenosine Triphosphate) is formed during respiration. ATP is a phosphorylated nucleotide it consists of: a nitrigenous base (adenine), a sugar and three phosphate groups.
- ADP consists of two phosphate groups.
- Dephosphodylation: ATP can be **hydrolised** to form ADP, this involves removing an inorganic phosphate (Pi) This releases energy for processes such as active transport, muscle contraction, and building new molecules (anaboitic reactions).
- Phosphodylation: ATP can then be regenerated from ADP and phosphate, which requires energy and the addition of an inorganic phosphate (Pi)
40
Define phosphorylation
Adding phosphates (ADP + Pi = ATP)
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Define photophosphorylation
Adding phosphates using light
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Define photolysis
Splitting up a molecule - using light energy
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Define Hydrolysis
Splitting up a molecule using water (ATP is hydrolysed to ADP)
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Define Reduction
When something is reduced it gains electrons, or it has gained hydrogen, or it has lost oxygen.
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Define oxidation
When something is oxidised it has lost electrons, or it has lost hydrogen, or it has gained oxygen.
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Define redox reaction
A reaction that involves reduction and oxidation.
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In the light-dependent reaction of photosynthesis, light energy generates ATP.
Describe how. (5)
In the light-dependent reaction of photosynthesis, light energy generates ATP.
Describe how. (5)
1. Light (energy) excites / raises energy level of electrons in chlorophyll;
2. Electrons pass down electron transfer chain;
3. (Electrons) reduce carriers / passage involves redox reactions;
4. Electron transfer chain in the thylakoid membrane
Example such as chemiosmosis;
5. Energy released / carriers at decreasing energy levels;
6. ATP generated from ADP and phosphate / Pi / phosphorylation of ADP
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Chemiosmosis
In chemiosmosis, energy from electrons passed through the electron transport chain pumps hydrogen ions (protons) through the thylakoid membrane, creating a proton gradient (concnetration of protons is greater in the thylakoid interior than in the stroma). Protons can only diffuse back into the stroma via an ion channel in **ATP Synthase**. This movement of protons is used by ATP synthase to generate ATP fron ADP and Pi.
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Desscribe the light dependent reactions in photosynthesis
1) Electrons are **excited** to a higher energy level using the energy trapped by **chlorophyll** molecules in the **thylakoid membranes**
2) The chlorophyll is found in complexes called photosystems. PSI absorbs light energy of 700nm wavelength, while PSII of 680nm wavelength.
2) Electrons are passed down the **electron transport chain** from one **electron carrier** to the next (through a series of redox reactions) and this process generates **ATP** from **ADP** and **inorganic phosphate** in a process called **chemiosmosis**. This whole process is called **photophosphorylation**, and it can either be cyclic or non-cyclic.
3) The final electron acceptor is NADP. When it accepts and electron is forms **reduced NADP** (NADP + H^+ + 2e- > reduced NADP).
4) Both ATP and recuced NADP are used in the light independent reactions.
Cyclic phosphorylation:
1. Photon hits chlorophyll in the **photosystem I (PSI)**
2. Electrons are excited
3. Electrons taken up by an electron acceptor
4. Electrons passed along an electron transport chain. Energy is released > chemiosmosis > ATP is synthesised
5. Returns to chlorophyll in PSI
Non-cyclic phosphorylation:
1. Photon hits chlorophyll in **photosystem II (PSII)**
2. Electrons are excited
3. Electrons are taken up by an electron acceptor, passed along an electron transport chain to PSI. Energy is released > chemiosmosis > ATP is synthesised.
4. **Photolysis** occurs in PII: light energy breaks apart the strong bonds in water molecules - forming hydrogen (used in the reduction of NADP), oxygen (a waste product) and electrons (H2O >>>(light energy)>>> 2e- + 1/2O + 2H^+). Electrons released replace lost electrons in chlorophyll of PSII.
5. Photon hits chlorophyll in PSI
6. Electrons are exited.
7. Electrons are taken up by an electron acceptor, passed along electron transport chain to NADP and, along with a H+ ion, forms reduced NADP.
50
Describe the light-independent reaction in photosynthesis
Takes place in the **stroma**, requires **ATP** and **reduced NADP** from the light-dependent reaction. **CO2** from the atmosphere and **RUBISCO** (an enzyme).
Calvin Cycle:
1) **CO2** enters the leaf through the **stomata** and into the **stroma** of the chloroplast.
2) It binds with a 5C molecule called **RuBP**. The carbon dioxide is **fixed**. The enzyme **RUBISCO** catalyses this reaction.
3) This makes a new 6C molecule which is very unstable and quickly breaks to from 2x 3C molecules called **GP**.
4) The **GP** molecules are **reduced** to for 2 different 3C molecules, called **GALP**. This requires **ATP** and **H+ ions** from the **reduced NADP** - these come from the light-dependent stage.
6) The NADPH+ becomes NADP and is recycled. GALP can be converted into many useful biological molecules e.g. glucose. However 5/6 of the carbons from GALP are used to **regenerate RUBP**. Therefore only 1/6 molecules of carbon from GALP can be used to make a hexose sugar. So to form 1 complete glucose molecule (C6H12O6), they cycle needs to occur 6x.
7) The regeneration of RUBP from GALP requires ATP.
51
Describe the light-independent reaction in photosynthesis
Takes place in the **stroma**, requires **ATP** and **reduced NADP** from the light-dependent reaction. **CO2** from the atmosphere and **RUBISCO** (an enzyme).
Calvin Cycle:
1) **CO2** enters the leaf through the **stomata** and into the **stroma** of the chloroplast.
2) It binds with a 5C molecule called **RuBP**. The carbon dioxide is **fixed**. The enzyme **RUBISCO** catalyses this reaction.
3) This makes a new 6C molecule which is very unstable and quickly breaks to from 2x 3C molecules called **GP**.
4) The **GP** molecules are **reduced** to for 2 different 3C molecules, called **GALP**. This requires **ATP** and **H+ ions** from the **reduced NADP** - these come from the light-dependent stage.
6) The NADPH+ becomes NADP and is recycled. GALP can be converted into many useful biological molecules e.g. glucose. However 5/6 of the carbons from GALP are used to **regenerate RUBP**. Therefore only 1/6 molecules of carbon from GALP can be used to make a hexose sugar. So to form 1 complete glucose molecule (C6H12O6), they cycle needs to occur 6x.
7) The regeneration of RUBP from GALP requires ATP.
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Anthropogenic climate change is linked to an increase in carbon dioxide in the atmosphere.
The World Meteorological Association recorded carbon dioxide levels of 405 ppm in 2017.
This is an increase of 46% since 1817.
Calculate the level of carbon dioxide in 1817.
405/1.46 = **277** (ppm)
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5.8 ii) What are the products from the Calvin cycle used for?
Calvin cycle products can be used to make **essential biological molecules**, including (but not limited to) carbohydrates, such as: Starch (for storage) Sucrose (for translocation around the plant) Cellulose (for making cell walls). used to build new plant **biomass**.
GP is used to produce:
- **Amino acids** - which can be used in protein synthesis to build polypeptides.
- **Fatty acids** which form the tails of lipid molecules such as triglycerides and phospholipids.
GALP is used to make:
- **Hexose sugars** which can be converted into other hexose sugars e.g. glucose can be converted into sucrose for transport in the phloem. Hexose sugars can be joined to make polysaccharides such as starch and cellulose.
- **Carbohydrates** - made from GALP molecules. Polysaccharides can be made by joining hexose sugars together. Glucose is needed for respiration to provide energy for biological processes.
- **Lipids** - made from glycerol, which is synthesised from GALP & fatty acids, which are synthesis from GP.
- **Nucleic acids** - Ribose is made using GALP. forms the basis of DNA.
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5.10 i) The grass in an ecosystem receives 950 000 KJm^-2yr^-1 of sunlight energy. It doesn't take in 931 000 KJm^-2yr^-1 of the energy recieved. The grass loses 8000KJm^-2yr^-2 using energy for respiration. Calculate the net primary productivity of the grass.
Gross Primary productivity: 950 000 - 931 000 = 19 000
NPP = GPP - R(respiration)
19 000 - 8000 = **11000** Kjm^-2yr^-1
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5.10 i) The grass in an ecosystem receives 950 000 KJm^-2yr^-1 of sunlight energy. It doesn't take in 931 000 KJm^-2yr^-1 of the energy recieved. The grass loses 8000KJm^-2yr^-2 using energy for respiration. Calculate the net primary productivity of the grass.
Gross Primary productivity: 950 000 - 931 000 = 19 000
NPP = GPP - R(respiration)
19 000 - 8000 = **11000** Kjm^-2yr^-1
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What is the equation for Net Primary Productivity?
NPP = GPP - R
Net Primary Productivity= Gross Primary Productivity - Respiration
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5.10 ii) Net Primary Productivity (NPP)
The rate at which energy from the sun is converted into organic molecules that make up new plant biomass, after accounting for respiration.
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Gross Primary Productivity (GPP)
The energy transferred to primary consumers
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Why is some energy lost at each trophic level?
Plants can't use all light energy that reaches their leaves because:
- Not all light falls on the (leaves, plants, producers).
- Some of the light is reflected (from the surface of the leaf).
- Some of the light misses the chloroplast (and passes through the leaf).
- Some of the light is (the wrong wavelength / not absorbed by the chlorophyll).
- Some parts of food (e.g. roots or bones) aren't eaten by organisms.
- Undigested matter
- Respiration (exothermic, transfers thermal energy to the surroundings)
- Some parts of food are indigestible so pass through organisms and come out as metabolic waste products like urea and faeces which pass to decomposers.
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What is the calculation used to work out the effeciency of energy transfer?
(Net Productivity / energy received) X 100
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The rabbits receive 20 000KJm^-2yr^-1, and their net productivity is 2000KJm^-2yr^-1. Work out the percentage efficiency of energy transfer.
(net productivity/energy recieved)x100
(2000/20,000)x100=10%
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Define Evolution
Evolution is change in the heritable traits of biological populations over successive generations. It occurs as a result of change in allele frquency, which in turn is affected by changing selection pressures.
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5.17) Describe the process of evolution via natural selection
1) A **variety of phenotypes** exist within a population due to **random mutations**.
2) An **environmental change occurs** and as a result of that the **selection pressure** changes.
3) Some individuals possess **advantageous alleles**, which gives them a **selective advantage and allow them to survive & reproduce**.
4) The advantageous alleles are passed on to their offspring.
5) Overtime, the frequenc of alleles in a population changes.
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Describe how reproductive isolation can lead to speciation
If two populations become reproducttively isolated and gene flow between the populations is reduced or stopped, accumulation of genetic differences in those populations will lead to new species being formed. When two populations can no longer interbreed to produce fertile offspring, they are said to be seperate species - speciation.
Reproductive isolaton occurs when there are changes in alleles & phenotypes of two populations which prevent them from successfully breeding together. These changes include:
- **Seasonal changes**: Individuals in the population develope new mating or flowring seasons or become sexually active at dif. times of the year.
- **Mechanical changes**: Changes in genitallia preventing successful mating
- **Behavioural changes**: A group of individuals develop courtship rituals that aren't attractive to the main population.
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Allopatric speciation
Where isolation is geographical
physical barrier seperates a population preventing interbreeding and gene flow. They become **reproductively isolated***. Populations adapt to new environments and become new species
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Sympatric Speciation
Isolation caused by non-geographical factors (e.g. random mutations) which prevent interbreeding & gene flow due to seasonal changes, mechanical changes or behavioural changes to individuals within the population.
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CP 11: The Hill Reaction
What is the function of dehydrogenase in chloroplasts?
It catalyses the acceptance of electrons by NADP in the light-dependent reactions.
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CP 11: The Hill Reaction
What is the purpose of DCPIP?
It is a redox indicator dye and acts as an alternate electron acceptor instead of NADP.
It turns from **blue to colourless** when it is reduced.
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CP 11: The Hill Reaction
Why is the plant extract chilled in an ice water bath?
The cells must first be placed in a cold, isotonic buffer solution to prevent damage to the organelles: the low temperature reduces enzyme activity that might break the chloroplasts down. The medium must have the same water potential as the leaf cells (so the chloroplasts don't shrivel or burst). A buffer maintains the pH to prevent proteins denaturing.
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CP 11: The Hill Reaction
How is the control set up?
Fill a cuvette with chloroplast extracts & distilled water.
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CP11: The Hill Reaction
How is light intensity controlled?
Adjust the distance of the lamp from the setup.
Perform the practical in a dark room so that the only light source is the lamp.
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CP11: The Hill Reaction
What is the function of the muslin cloth?
To filter out any debris in the ground leaf mixture but allowing chloroplasts to pass through.
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CP11: The Hill Reaction
Why are the stalks of the leaves removed before grinding?
The stalks do not contain many chloroplasts
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CP 11: Outline the procedure of investigating the effect of light intensity, after chloroplast extract has been obtained.
1. Set the colorimeter to the **red filter**. Zero using a cuvette containing chloroplast extract and distilled water.
2. Place the test tube in the rack 30cm from the light source and add **DCPIP**. Immediately take a sample and add to cuvette. Measure the **absorbance** of the sample.
3. Take a sample and measure its absorbance **every 2 mins for 10 mins**.
4. Repeat for different distances from the lamp up to 100cm.
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CP 11: What is the effect of light intensity on the hill reaction?
Conclusion:
AS light intensity **decreases**, the rate of photosynthesis **decreases**. This is because the lowered light intensity will **slow the rate of photoionisation** of the chlorophyll pigment, so the overall rate of the light dependent reaction will be slower. Less electrons are released by the chlorophyll, hence the DCPIP accepts less electrons, meaning it will take longer to go from blue to colourless. When DCPIP is blue, the absorbance is higher, a high rate of decrease (steep gradient) indicates that the dehydrogenase is highly active.
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Evidence of Evolution
- Fossil Records (show how organisms have changed + provide evidence for transitional species),
- Real Life Observations (e.g. the development of antibiotic resistance shows evolution by natural selection)
- Molecular evidence - Genomics & Proteomics
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Genomics
Evidence of evolution from **gene sequences**
Comparing the sequences of equivalent genes in different species can show:
- Common ancestry (If base sequences are very similar across dif. species)
- The level of similarity can give measures of how long ag two species diverged from each other (similar sequences = more recently diverged), which can be used to establish relationships between organisms (species that share a recent common ancestor = more closely related).
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Proteomics
The study of **proteins**, e.eg size, shape and **amino acid sequence** of proteins.
The sequence of amino acids in a protein is coded from by DNA sequence in a gene. Related organisms have similar DNA sequences and so similar amino acid sequences in their proteins. So organisms that diverged away from each other more recently should have more similar proteins as less time has passed for change to occur.
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How are theories validated by the scientific community?
1. **Scientific journals**
used to share new ideas, theories, experiments, evidence & conclusions. Allow other scientists to ***repeat** experiments using the same methods. If results are replicated over & over again that the scientific community can be pretty confident that the evidence is **reliable**.
2. **Peer Reviews**
Before work is published, other scientists who work in that area **read & review** the work to check it is **valid** & supports the conclusions. PR is used to try and ensure that only **valid** scientific evidence & experiments that are carried out to the **highest possible standards** are published.
3. **Scientific Conferences**:
- Meetings where scientists can present and discuss each other's work. Scientists can ask face-to-face questions. Allows the latest theories & evidence to be shared & discussed.
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Core Practical 13: Investigating the effects of temperature on the development of organisms
Method (Brine shrimps):
1. 2g of sea salt + 100cm^3 of dechlorinated water in beaker. Stir until dissolved.
2. Put brine shrimp egg cysts onto a sheet of paper.
3. Wet a piecce of graoho paper in salt water & pplace face-down onto the paper to pick up some eggs.
4. Use a microscope to count 40 eggs.
5. Place the graph paper with 40 eggs upside-down into the beaker & leave for 3 mins/until all eggs detach.
7. Incubate beaker at a set temperature for a set time (i.e. 24hrs).
8. Remove beaker from incubator and shine bright light on it. Any hatched larvae will swim towards the light & can be counted.
9. Return beaker to incubator and repeatedly remove & count hatched larvae every 5 hours.
10. Repeat all steps at a range of temps.
Plot graphh of temp against hatched larvae
Hatch rate = number of hatched brine shrimp in each water bath/number of hours
Controls: Number of eggs in each sample, Length of time incubated, volume of water, salinity of the water, O2 conc.
Conclusion:
As temp increases, the number of shrimp hatched increases up to an optimum of about 25dc. After the optimum temp, as temp increases, number of shrimp hatched will decrease. This can be explained in terms of enzymes & indicates that as climate change increases temp of sea water, the development of shrimps will decrease.
Seedling growth rate
1. Plant some seedlings (of same variety & age) in soil trays and measure the height of each.
2. Place in incubators at different temperatures for a set time and then record the change in height of each seedling
3. Average growth rate = average change in height in each tray/incubation period. Use this to craft a bar chart of avergae growth rate against temperature.
Conclusion: They show and increase in growth up to optimum temp (as rate of photsynthesis increases) & then decreases (as water loss will increase & crenation may occur). This indicates that plants are vulnerbale to climate change.
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Core Practical 13: Investigating the effects of temperature on the development of organisms (brine shrimps)
How can the organisms be treated ethically during this practical?
Minimise exposure to stressful testing conditions and release into salt water/their natural habitat when practical is complete
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Core Practical 13: Investigating the effects of temperature on the development of organisms (brine shrimps)
How can the organisms be treated ethically during this practical?
Minimise exposure to stressful testing conditions and release into salt water/their natural habitat when practical is complete
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CP12: Investigating the effect of temperature on the reate of an enzyme controlled catalysed reactions
What is the temperature co-effecient (Q10)
Q10 = The change in rate of reaction caused by a 10 degree increase in temperature
Formula: Rate at T+10/Rate at T
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CP12: Investigating the effect of temperature on the reate of an enzyme controlled catalysed reactions
How can you measure the rate of reaction using hydrogen peroxide and catalase?
1. Grind known mass of peas in distilled water, place into boiling tube and add 5cm^3 of hydrogen peroxide solution.
2. Measure the volume of gas produce in a given time (every 10 seconds for a minute) using a gas measuring syringe, clamps stand, delivery tube and bung.
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CP12: Investigating the effect of temperature on the reate of an enzyme controlled catalysed reactions
What is a limitations of Q10?
It can only be used up to the optimum temperature
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CP12: Investigating the effect of temperature on the reate of an enzyme controlled catalysed reactions
State the word equation for the reaction of catalase
Hydorgen peroxide >>>> Oxygen + water
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CP12: Investigating the effect of temperature on the reate of an enzyme controlled catalysed reactions
What are the controlled variables of this practical?
- Enzyme volume & concentration (pea solution)
- Subtrate volume & concentration (hydrogen peroxide)
- pH
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CP12: Investigating the effect of temperature on the reate of an enzyme controlled catalysed reactions
State the safety hazards and precautions invloved in this practical
- Hydrogen peroxide is an irritant. Wear eye protection & avoid contact with skin.
- Take care in handling hot water baths, and wash hands after handling peas/source of catalase.
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What does a Q10 value of 2 mean?
The rate **doubles** when temp is raised by 10dc.
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CP12: Investigating the effect of temperature on the reate of an enzyme controlled catalysed reactions
How would you work out Q10 from findings?
1. Draw graph for volume of O2 produced against time for each temp
2. Initial rate for each temp = Volume of gas/time
3. Draw a graph for rate of reaction against temperature
4. Q10 = Rate at T +10 degrees / rate at 10 degrees
Conclusion
For catalase Q10 is around 2; the rate double for every 10degree increase
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CP12: Investigating the effect of temperature on the reate of an enzyme controlled catalysed reactions
How would you work out Q10 from findings?
1. Draw graph for volume of O2 produced against time for each temp
2. Initial rate for each temp = Volume of gas/time
3. Draw a graph for rate of reaction against temperature
4. Q10 = Rate at T +10 degrees / rate at T degrees
Conclusion
For catalase Q10 is around 2; the rate double for every 10degree increase
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CP11) Describe how to isolate a chloroplast
Prepare leaf material:
Collect fresh leaves from a suitable plant (like spinach) and wash them thoroughly.
Grind in isolation buffer:
Place the leaves in a chilled mortar and grind them with a pestle in an ice-cold isolation buffer containing sucrose to maintain the integrity of the chloroplasts.
Filtration:
Filter the homogenate through a fine mesh sieve or muslin cloth to remove large cell debris and leaf tissue.
centrifugation:
Centrifuge the filtered homogenate to pellet large cell debris, carefully remove the supernatant.
Pellet collection:
Collect the chloroplast pellet at the bottom of the centrifuge tub
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Deflected succession
the interruption of natural ecological succession by human activities, preventing an ecosystem from reaching its natural climax community and resulting in a stable, but altered, community called a plagioclimax
