ecology stuff

Question 1

advantages generally

Answer 1

less competition

Question 2

features of succession that would bring about an increase in the index of diversity

Answer 2

Initial environment is hostile as few organisms adapted, these organisms change the environment pioneer speices, more niches more habitats allowing other organisms to become established

Question 3

two reasons why a species of seed did not grow succesfully in a climax community

Answer 3

too little food in seeds to become established, not enough light for psynth or small size

Question 4

how to use a transect to get a MEAN percentage cover( to get a mean you flipping repeat it)

Answer 4

Create a grid by placing 2 transect tape measures at right angles, use a random generator to produce coordinates. Place quadrats at coordinates and estimate percentage cover of…
Reapeat many times. calculate mean percentage cover by adding up all the percentages and dividing them by the number of quadrats.

Total population = Average number per quadrat × Total area/Area of quadrat.

Question 5

explain how something has evolved

Answer 5

geographical isolation, seperate gene pools, variation occurs due to mutations, different selection pressures pass on alleles due to mutations and this leads to an increased allele frequency of that gene

Question 6

how to do mark release recapture- how to estimate the pop of anguirelas angathon

Answer 6

capture the organisms in a safe way, leave sufficient time for them to distribute randomly within the population, collect a second sample and count the number of marked invididuals. population=number in first sample times second sample/ number of marked individuals in the second sample

Question 7

can mutations spread to other insects

Answer 7

no because mutations are random and only the rate of them can be affected by the environment, different species do not interbreed to produce fertile offspring, so mutations cannot be passed from one species to another.

Question 8

anything about why something is high frequency

Answer 8

the people with that allele reproduce and over many generations it becomes the most common gene in the gene pool

Question 9

benefits of woodlands

Answer 9

protects niches and habitats, conserves endangered species, reduces global warming, sources of medicine, reduces erosion

Question 10

why do scientists measure the o2 produced to measure the rate of psynth

Answer 10

faster oxygen production means that more made in the ldr which means that more psynth occurs as o2 is a waste product

Question 11

limits of transect lines

Answer 11

may avoid certain areas.

Question 12

describe how you would determine the mean percentage cover for beach grass on a sand dune

Answer 12

randomly determine coordinates, large sample size and then divide total percentage by the number of quadrats

Question 13

explain the decrease in gross productivity as the woodland matures

Answer 13

less light more competition for light, reduced psynth

Question 14

succession, why does biomass increase

Answer 14

pioneer species, less hostile conditions, increase in niches or animals or whatevre

Question 15

Explain the increase in the diversity of birds as the woodland developed.

Answer 15

greater variety of plants, more food sources, more habitats and niches

Question 16

explain why co2 uptake is a measure of gross productivity

Answer 16

as it shows productivity minus respiration

Question 17

explain how the shade plant is better

adapted than the sun plant to growing at low light intensities.

Answer 17

has lower respiratory losses

Greater (net) productivity of glucose used / more

Question 18

Use the information in the graph and your knowledge of net productivity to explain
why biomass shows little increase after 100 years.

Answer 18

Net productivity = gross productivity minus respiratory loss;
2. Decrease in gross productivity

Question 19

Explain why the scientists sterilised the surfaces of the seeds and grew them in soil that had been heated to 85 °C for 2 days.

Answer 19

To kill any bacteria on surface of seeds or in soil

2. So only the added fungus has any effect.

Question 20

Explain why it was important that the soil contained no mineral ions useful to the
plants.

Answer 20

So that only type of fertiliser affects growth

Question 21

Suggest what the scientists should have done during the drying process to be sure that all of the water had been removed from the plant samples.

Answer 21

Weigh samples at intervals during drying;

2. To see if weighings became constant

Question 22

Can you conclude that the insect pest resistant to Bt toxin found in the years 2002
to 2005 was the same insect species? Explain your answer.

Answer 22

graph shows number of specices not the name of the species

Question 23

There was a time lag between the introduction of Bt crops and the appearance of
the first insect species that was resistant to the Bt toxin.
Explain why there was a time lag.

Answer 23

Initially one / few insects with favourable mutation / allele;
2. Individuals with (favourable) mutation / allele will have more offspring;
3. Takes many generations for (favourable) mutation / allele to become the
most common allele (of this gene).

Question 24

what is meant by uniformally distributed

Answer 24

equally spread number of organisms in a region

Question 25

Use the letters A, R and S to write an equation showing how proportional sampling
is used to estimate the total size of a population, P. Show your working.

Answer 25

p= AS/R

Question 26

How do the assumptions made in proportional sampling differ from those
made in mark-release-recapture?

Answer 26

No assumption that organisms are uniformly distributed;

Size of total area sampled not required;

Question 27

Give one assumption about the animals caught that is made in both methods

Answer 27

We assume the animals are from the same population

Question 28

The ecologists captured insects from a number of sites on the island. Suggest how
they decided where to take their samples.

Answer 28

Draw grid over (map of) area;

2. Select squares / coordinates at random.

Question 29

Suggest the advantage of using the fluorescent powder in this experiment.

Answer 29

Only glows brightly with UV, so doesn’t make insects more visible;
2. So doesn’t affect / increase predation;

Question 30

Use the information provided to suggest one way in which the method used by the
ecologists might have caused the increase in their estimates of the size of the insect
population.

Answer 30

Scientists removed large numbers of insects (which were not returned)
from same area / same population;
2. Affecting ratio of marked to unmarked.

Question 31

p values

Answer 31

greater than 5 percent due to chance when its >0.05 not <0.001 which is likely that it is not due to chance and the results are significant

Question 32

Suggest how this student would obtain data to give a more precise value for the
index of diversity of this habitat.

Answer 32

Take more samples and find mean;

2. Method for randomised samples described.

Question 33

describe how you would use quadrats to determine whether a particular species has a clustered or random distribution

Answer 33

use of random numbers to place quadrats, individuals counted and if little variation then random, if large variation clustered

Question 34

advantages generally

Answer 34

less competition

Question 35

standard answer for succession

Answer 35

intial environment hostile, these pioneer species change the environment, more niches or habitats, allows other organisms to become established

Question 36

as age of trees increase why does less light pen

Answer 36

as trees block sunlight

Question 37

quadrat investigation

Answer 37

Set up grid system with coordinates;

2. Place large number of quadrats (at coordinates) selected at random;
3. Count number of / estimate percentage cover of native plant in quadrats;
4. Repeat at same time each year (for many years);

Question 38

2 reasons why a plant can become dominant

Answer 38

outcometes other plants, less predators, ideal niche, better competes for abiotic resources

Question 39

2 reasons why a plant can become dominant

Answer 39

outcometes other plants, less predators, ideal niche, better competes for abiotic resources

Question 40

2 economic consequences for the spread of hydrilla

Answer 40

cost of removal, cost of restoring habitat,

Question 41

why reheating and weighing till they found a constant mass of plant is good

Answer 41

to remove water content as plants each contain a diff amount of water

Question 42

why is uniformly distributed plants a good thing

Answer 42

less comeptition for water or nutrients

Question 43

why is the climax community the most stable

Answer 43

more species present, more complex food webs

Question 44

explain what limits the size of a population in a climax community

Answer 44

named nutrient availability;

2. numbers of producers providing energy (for a food chain) / light intensity affecting the rate of photosynthesis;
3. disease killing (weaker) members of species / predation described;
4. space for nest building / niches;
5. competition for a named limited resource / (intra and interspecific) competition explained;

Question 45

explain succession

Answer 45

species with the largest population initially are the pioneer species. This dies and decomposes creating increased soil depth and adding nutrients into the soil. The change in ABIOTIC conditions allowed the next species to colonise and outcompete beach grass. Less hostile conditions created. This adds more humus content to the soil increasing soil depth further. Further improves conditions for the climax community to colonise and increase in numbers outcompeting the other species.

Question 46

why conservation is important

Answer 46

Conserving / protecting habitats / niches;
2. Conserving / protecting (endangered) species / maintains / increases
(bio) diversity;
3. Reduces global warming / greenhouse effect / climate change / remove /
take up carbon dioxide;
4. Source of medicines / chemicals / wood;
5. Reduces erosion / eutrophication.

Question 47

How do the assumptions made in proportional sampling differ from those
made in mark-release-recapture? and give one made in both

Answer 47

In mark–release-recapture
1. No assumption that organisms are uniformly distributed;
2. Size of total area / size of sampled region not required;
Marking point 1 or marking point 2 do not have to start with
the same technique
In this case, allow difference by implication i.e. do not
penalise if the two techniques are not compared
2
(ii) Animals are from / all part of the same population