Biology Topic 5

Question 1

What is interspecific competition?

Answer 1

1. When organisms of different species compete with one another for same resources.
2. So resources available for both populations are reduced. So both populations will have less energy for growth and reproduction, so the population sizes will be lower for both species.

Question 2

What is intraspecific competition?

Answer 2

When organisms of the same species compete with each other for the same resources

1. The population of a species increases when resources are plentiful. As population increases, there’ll be more organisms competing for the same amount of space and food.
2. Eventually resources become limited and population begins to decline.
3. Smaller populations means less competition for resources, so population begins to grow again.
4. Maximum stable population size that an ecosystem can support = carrying capacity.

Question 3

Explain how predator and prey population sizes are linked.

Answer 3

1. As prey population increases there’s more food for predators, so the predator population grows.
2. As predator population increases, more prey is eaten so prey population begins to fall.
3. This means less food for the predators, so their population decreases, and so on.

Question 4

Name some abiotic factors that affect distribution.

Answer 4

Some plants only grow on south-facing slopes in the northern hemisphere, where light intensity is greatest.

Some plants don’t grow near to shoreline because the salt is too saline.

Large trees can’t grow in polar regions because temperature is too low.

Question 5

Biotic factors that can affect distribution?

Answer 5

Interspecific competition can affect species distribution. If two species are competing but one is better adapted to its surroundings, the less well adapted species will be out-competed and unable to exist alongside better adapted species.

Question 6

Define niche.

Answer 6

A niche is the role of a species within its habitat, including biotic and abiotic interactions.

Every species has its own unique niche and a niche can only be occupied by one species.

Question 7

Explain random and non-random sampling.

Answer 7

To avoid bird in your results, the sample should be random. Eg dividing field into grid and using random number generator to select coordinates.

However sometimes necessary to take a non-random sample. Non-random samples can be used in habitats where there’s lots of variety in abiotic features and distribution of species and you want all areas and species to be sampled.

Systematic sampling= type of non-random sampling when samples are taken at fixed intervals often along a line. E.g. quadrats placed along a line called a transect in a sample where abiotic factors gradually change along the transect.

Question 8

Explain point quadrats

Answer 8

Used to investigate plant populations

1. Point quadratic = horizontal bar on two legs with a series of holes at set intervals along its length.
2. Pins dropped through holes in frame and every plant that that each pin touches is recorded.
3. Number of individuals of each species is recorded in each quadrat.
4. Percentage cover= number of pins that touch given species÷ total number of pins x100
5. Useful in areas where there’s lots of dense vegetation close to ground

Question 9

Explain how transects are used

Answer 9

Used to investigate distribution of plant populations

1. Line transects- a tape measure is placed along the transect and species that touch the tape measure are recorded.
2. Belt transects - data is collected along the transect using fram quadratic placed next to each other.
3. Interrupted transects: taking measurements at intervals. E.g. by placing quadratic every 2 metres.

Question 10

Measuring climate within a habitat?

Answer 10

1. Temperature is measured using a thermometer

2.Rainfall is measured using a rain gauge - a funnel attached to a measuring cylinder

3. Humidity can be measured using an electronic hygrometer.

Question 11

1. Measuring oxygen availability in a habitat?
2. Measuring solar input in a habitat?

Answer 11

1. Only neede to be measured in aquatic habitats. The amount of oxygen dissolved in the water is measured using a light sensor.
2. Measured using a light sensor

Question 12

Measuring edaphic factors (soil conditions) in an ecosystem?

Answer 12

pH is measured using indicator liquid - a sample of the soil is mixed with water and an indicator liquid that changes colour depending on pH. The colour is matched against a chart.

Moisture content- the mass of a sample of soil is measured before and after being dried out in an oven at 80-100 degrees Celsius. The difference in mass as percentage of original soil mass = water content of soil.

Question 13

Measuring topography (shape and features of the Earth’s surface) in a habitat?

Answer 13

Relief (how the height of the land changes across a surface) can be measured by taking height readings using a GPS device at different points across the surface. You can also use contour lines on a map.

Slope angle is measured using a clinometer. A simple clinometer is just a piece of string with a weight on the end attached to the centre of a protractor. You point the flat edge of the protractor up the hill, and read the slope angle of the protractor.

Aspect ( the direction a slope is facing) is measured using a compass.

Question 14

Difference between primary and secondary succession?

Answer 14

1. Primary succession- this happens on newly formed or exposed land e.g. where a volcano has erupted to form a new rock surface, or where sea level has dropped exposing new area of land. There’s no soil or organic material to start, just rock.
2. Secondary succession- this happens on land that’s been cleared of all the plants, but where the soil remains, e.g. after forest fire or deforestation.

Question 15

Describe primary succession

Answer 15

Primary succession starts when species colonise new land surfaces. Seeds and spores are blown by wind and begin to grow. First species to colonise = pioneer species.

The abiotic conditions are hostile e.g. no soil to retain water. Only pioneer species grow because they’re adapted to cope with harsh conditions.

Pioneer species change the abiotic conditions- they die and microorganisms decompose the dead organic material. This forms basic soil.
This makes conditions less hostile so new organisms can move in. Who then die and are decomposed making the soil richer.

Some new species may change the environment so that it becomes less suitable for the previous species.

Question 16

Describe secondary succession

Answer 16

Secondary in same way as primary, but because there’s already a soil layer it starts at later stage. Pioneer species are therefore larger plants.

At each stage different plants and animals better adapted to conditions move in and out-compete species currently there , so they become the dominant species.

As succession goes on, ecosystem becomes more complex. New species move in alongside existing species, increasing biodiversity.

When ecosystem is supporting largely community it can it won’t change much more. This called the climax community.

Question 17

Describe the succession of bare rock to woodland.

Answer 17

1. Pioneer species colonise the rocks e.g. license grow on and break down rocks, releasing minerals.
2. Lichens die and are decomposed to form thin soil. So other species like mosses can grow.
3. Larger plants that need more water can move in as the soil deepens.
4. Shrubs, ferns and small trees grow, out-competing smaller plants to become dominant species. Diversity increases.
5. Finally soil is deep and rich enough to support large trees. They become the dominant species, and the climax community is formed.

Question 18

Describe role of ATP.

Answer 18

Cell can’t directly fron glucose

During respiration glucose is broken down. This releases energy for ATP which carries energy to where is needed in the cell.

It is synthesised by the phosphorylation of ADP

It is broken down via hydrolysis back into ADP and PI catalysed by ATPase, the releases energy.

ADP and PI are recycled and the process repeats itself

Question 19

Describe structure of chloroplasts.

Answer 19

Double membrane

Thylakoids have large SA to allow as much light to be absorbed as possible. They’re stacked up in the chloroplast to form granum. The grana are linked together by bits of thylakoid called lamellae. Thylakoid membranes contain lots of ATP synthase to produce ATP in the light dependent reaction.

Chloroplasts contain photosynthetic pigments attached to proteins to form photosystems. Photosystem I = 700nm photosystem II = 680nm

Stroma surrounds thylakoids this is where the light independent reaction takes place.

Question 20

Describe the light dependent reaction of photosynthesis.

Answer 20

1. Light energy excited electrons in chlorophyll.
   Light energy is absorbed by PSII.
   Light energy excites electrons in chlorophyll making them enter a higher energy level. This causes them to move along the electron transport chain to photosystem I.
2. As excited electrons from PSII to move along the ETC, they must be replaced. Light energy splits water into protons (H+), electrons and oxygen. This is called photolysis.
3. Excited electrons lose energy as they move along ETC. The energy is used to transport H+ into the thylakoids so there is a greater concentration of H+ than the stroma. Protons move down their concentration gradient into the stroma, via ATP synthase. The energy from this movement combines ADP and PI to ATP.
4. Light energy absorbed by PSI, exciting electrons to even higher energy level. The electrons are transferred to NADP along with a H+ ion to form NADPH ( reduced NADP).

Question 21

How does cyclic phosphorylation differ from non cyclic (normal)?

Answer 21

Only uses PSI

Electrons not passed onto NADP, but passed back to PSI via electron carriers.

So ATP is only product produced and in small amounts.

Question 22

Describe the light independent reaction ( calvin cycle).

Answer 22

1. CO2 enters leaf through the stomata and diffuses into the stroma of the chloroplast.
   -Here it combines with RuBP, catalysed by RUBISCO. This gives an unstable 6 carbon compound which quickly breaks into two molecules of GP.
2. Breakdown of ATP from light-indepenent reaction provides energy to convert GP to form GALP. Reaction also needs H+, which comes from NADPH which is recycled to NADP.
3. Two molecules of GALP can be used to make a hexose sugar e.g. glucose.

However 5 out of 6 molecules of GALP produced are used to regenerate RuBP. This uses rhe remaining ATP produced by the light dependent reaction.

Question 23

Investigating photosynthesis using extract of chloroplasts core practical.

Answer 23

1. Cut a few leaves into pieces.
2. Grind up leaf pieces with chilled isolation solution. Filter the liquid into beaker using funnel lined with muslin cloth. Transfer the liquid into centrifuge tubes and centrifuge at high speed for 10 minutes. This will make the chloroplast gather at bottom of tube in a ‘pellet’.
3. Re-suspend pellets in chilled isolation solution. This is your chloroplast extract.
4. Set up colorimeter with red filter and zero it using cuvette with pellet and distilled water.
5. Set up test tube at a set distance from a lamp. Turn the lamp on.
6. Place test tube in rack and add set volume of chloroplast extract and DCPIP and mix.
7. Immediately take sample of mixture and add to cuvette. Measure the absorbance every 2 mins for 10 mins. Faster the absorbance decreases the faster the hill reaction as DCPIP is reduced by electrons, losing its blue colour.
8. Repeat experiment, ensuring the tubes are exposed to the light source for same amount of time at same distance.

Question 24

Equation for net productivity?

Answer 24

NPP = GPP - respiration loss

Question 25

Why is energy lost down trophic levels?

Answer 25

Not all taken in in first place: e.g. plants can't use all light energy that reaches their leaves as some is wrong wavelength, reflected or passes straight through. Some light hits non-photosynthetic parts of plant such as bark. Some parts of food e.g. roots and bones aren't eaten by organisms so that energy isn't passed on. Some parts of food are indigestion so pass through organisms and come out as waste. From the energy that is absorbed roughly 75% is lost due to respiration and the rest is absorbed to become biomass which is stored or used for growth.

Question 26

How is energy transfer between trophic levels measured, and what are the limitations?

Answer 26

Measure the difference in biomass between levels. Biomass = dry mass of organisms, which reflects stored energy. Obtain dry mass by drying in oven at low temp until mass remains constant. Multiply dry mass by total population in the area. Difference in energy between two levels tells you how much energy has been transferred. Limitations: organisms may gain energy from other sources To make more accurate, include all organisms in each trophic level.

Question 27

How do temperature records provide evidence for climate change?

Answer 27

1. Average global temp gm fluctuated around 13.6 degrees between 1850 and 1910. 2. Steadily increased from 13.6 in 1910 to 14.4 degrees today. 3. General trend of increasing global temperature over the last century is evidence for climate change.

Question 28

How does dendrochronology provide evidence for climate change?

Answer 28

Dendrochronology = method of figuring out how old a tree is using tree rings. Most trees produce one ring within their trunks every year. Thickness of ring depends on climate- when it's warmer rings are thicker because conditions are better for growth. Scientists can take cores through tree trunks then date each ring by counting them back from where the core was taken. By looking at the thickness of the rings they can see what the climate was like each year.

Question 29

How can pollen in peat bogs provide evidence for climate change?

Answer 29

Pollen in peat bogs can be used to show how temperature has changed over thousands of years. 1. Pollen is often preserved in peat bogs. 2. Peat bogs accumulate in layers so the age of the preserved Pollen increases with depth. 3. Scientists can take cores from peat bogs and extract Pollen grains from the different aged layers. Because plant species vary with climate the preserved Pollen will vary as climate changes. 4. So, gradual increase in Pollen from a plant species more successful in warmer climate would show a rise in temperature.

Question 30

CO2?

Answer 30

Atmosphere CO2 conc had increased by over 100 ppm since mid 19th century. CO2 conc is increasing as more fossil fuels are burnt, releasing CO2. CO2 conc also increased by destruction of natural carbon sinks such as trees, which release CO2 when burnt of decomposed and respired.

Question 31

CH4?

Answer 31

Atmospheric methane conc bas doubled since mid 19th century Methane conc is increasing because more methane is being released into the atmosphere e.g. from cattle. Methane can also be released from natural stores e.g. frozen ground. As temperature increases, these stores will thaw and release large amounts of methane into the atmosphere.

Question 32

How can climate change affect organisms?

Answer 32

Increasing temp increases enzyme activity Warmer water increases cyanobacterial growth rate which may lead to harmful algal blooms. Above about 25 degrees Celsius wheat develops few grains and yields fall. Affects distribution e.g. alpine plants move higher up mountains where it is cooler as temperature increases.

Question 33

What other types of climate change affect plants and animals?

Answer 33

1. Changing rainfall patterns: will affect life cycle and development of certain organisms, as well as distribution. 2. Season cycles: global warming changes the timing if mating seasons. Changing development, life cycles and distribution of some organisms.

Question 34

Investigating effect of temperature on organisms using seedling growth rate?

Answer 34

1. Plant some seedlings of same variety and age in soil trays and measure the height of each seedling. 2. Put trays in incubators at different temperatures. 3. Keep other variables such as light intensity the same for each tray. 4. After a period of incubation record the change in height of each seedling. Average growth rate can be calculated by dividing average change in seedling height in each tray by incubation period.

Question 35

Investigating effect of temperature on organisms using brine shrimp hatch rate?

Answer 35

1. Put equal number of brine shrimp eggs in water baths set a different temperatures. 2. Make sure all other variables e.g. volume of water is same for each water bath. 3. Record number of hatched brine shrimp in each water bath every 5 hours. The hatch rate can be calculated by number of hatched brine shrimp in each water bath ÷ number of hours.

Question 36

Measuring how temperature effects the initial rate of enzyme-catalysed reactions?

Answer 36

1. Set up boiling tubes containing same volume and conc of hydrogen peroxide. Add buffer to each tube to keep pH constant. 2. Set up gas syringe. 3. Put each boiling tube in water bath Set at different temps e.g. 15,20,25,30,35 degrees. 4. Use pipette to add same volume and conc of catalysed to each boiling tube. Then quickly attach the bung and delivery tube. 5. Record how much oxygen produced every 10 seconds for first minute of reaction. Use a stopwatch to measure time.

Question 37

What is Q10 and how can it be calculated?

Answer 37

Shows how much the rate of a reaction changes when temperature raised by 10 degrees Example Q10 = rate at 40 degrees / rate at 30 degrees Most enzyme controlled reactions Q10 = about 2

Question 38

Give 2 examples of how research conclusions of causes of climate change could be biased.

Answer 38

Scientist working for oil company may be more likely to say humans aren't causing climate change to keep oil sales high. Scientist working for renewable energy company may be more likely to say humans are causing climate change to increase sales of energy produced from renewable sources.

Question 39

2 ways to decrease atmospheric CO2 concentration?

Answer 39

1. Biofuel: no net increase of CO2 as CO2 given off when burnt is same as CO2 absorbed by crops when they're growing. 2. Reforestation: planting of new trees in existing forests that had been depleted. More trees means more CO2 removed from atmosphere by photosynthesis.

Question 40

Disagreements about reducing climate change?

Answer 40

Biofuel: farmers may support as some govts fund farming of crops for biofuels. Drivers might support as price of biofuel cheaper than oil based fuels. Consumers may oppose as using farmland to grown biofuel could cause food shortages. Conservationists may oppose as forests have been cleared for biofuels. Wind turbines: Companies that make wind turbines would support Environmentalists support this strategy. Local community may oppose and bird conservationists

Question 41

What is allopatric speciation?

Answer 41

Requires geographical isolation Populations that are isolated in slightly different conditions so diff selection pressures so diff mutations are advantageous. Changes in allele frequency over time makes the two populations genetically distinct - unable to breed to produce fertile offspring.

Question 42

What is sympatric speciation?

Answer 42

Does not require geographical isolation Includes 1.Seasonal changes e.g. diff flowering or mating seasons or sexually active at diff times of year. 2. Mechanical changes: changes in genitalia preventing successful mating. 3. Behavioural changes - develop courtship rituals unattractive to main population.

Question 43

What is genomics?

Answer 43

Branch of science that uses DNA technology to determine the base sequence of an organisms genome. This allows scientists to make comparisons between organisms DNA - closely related species diverged more recently so should have similar DNA sequences.

Question 44

What is proteomics?

Answer 44

Study of proteins Sequence of amino acids in a protein is coded for by the DNA sequence in a gene. Related organisms have similar DNA sequences and so similar amino acid sequences in their proteins. So organisms that diverged more recently should have more similar proteins, as less time has passed for changes to occur.

Question 45

How does the scientific community validate evidence about evolution?

Answer 45

1. Scientific journals : allow scientists to repeat experiments and see if they get same result. 2. Peer review: checks work is valid and that it supports the conclusion. 3. Conferences: easy way for latest theories to be shared and discussed.