U1T4 - Ecosystems (1)

Question 1

How do populations change depending on resources?

Answer 1

If enough, stay high + reproduce. Not enough, intra specific competition occurs.

Question 2

Give an example of population growing in closed conditions.

Answer 2

Bacteria growing in nutrient medium in beaker.

Question 3

How is the pattern of population growth measured?

Answer 3

Change in num of organisms.

Question 4

What are the 4 basic phases of population growth in closed conditions?

Answer 4

Lag phase, exponential phase, stationary phase + decline phase.

Question 5

What type of curve is the curve detailing population growing in closed conditions?

Answer 5

Sigmoidal curve. e.g. colonising new area, time to reach sexual maturity. Most stay in stationary + don’t reach decline.

Question 6

Where might you find a J-shaped curve for population growth?

Answer 6

Yeast growth in open/continuous culture where waste + dead cells constantly removed + fresh medium added or pop of mammals protected from natural predators to encourage pop growth. Represents biotic potential. Many protoctistan pops have it.

Question 7

Describe the common curve of protoctista.

Answer 7

J shaped curve. Rapid Spring growth as abundant nutrients in water, temp + light increase + few herbivores. Midsummer pop crash (no stationary) as nutrient supply exhausted + herbivores + waste increase.

Question 8

Why does temperature influence population growth patterns?

Answer 8

Determines metabolic rate in organisms + so rate they develop. Rate of increase in exponential phase rises at higher temps but doesn’t influence size of max pop in stationary phase which is determines by resources.

Question 9

Why has there been no human population crash even though there is a lack of resources in some parts of the world?

Answer 9

Aid, healthcare. Reduced infant death + higher life expectancy.

Question 10

What are 4 factors affecting population growth + size?

Answer 10

Birth rate, immigration, death rate + emigration.

Question 11

What is the formula to estimate change in population size?

Answer 11

(Births + Immigration) - (Deaths + Emigration)

Question 12

What are the equations of:
A population in equilibrium
A growing population
A decreasing population

Answer 12

B + I = D + E
B + I > D + E
B + I < D + E

Question 13

How can the effect of seasonal changes on population growth be represented?

Answer 13

Survivorship curves.

Question 14

Why might population sizes change from year to year?

Answer 14

Normal predator-prey relationships, changes in food supply or abiotic factors such as severe temp changes.

Question 15

Give some examples of R Selected Species’.

Answer 15

Bacteria. protoctista, weeds.

Question 16

Give some examples of K Selected Species’.

Answer 16

Large mammals, humans, elephants, oak trees.

Question 17

What are 3 different types of population interactions?

Answer 17

Competition (-/-), Grazing, Parasitism + Predation (+/-) + Mutualism (+/+)

Question 18

When will competition occur?

Answer 18

When there is a limit to the availability of resources such as food, space + water + therefore not enough for all.

Question 19

What is the effect of competition?

Answer 19

It reduces the growth rate of individuals + their repro capacity. Influences carrying capacity.

Question 20

What are the characteristics of competition?

Answer 20

Both species’ do less well when competing for same resource, 1 is eventually eliminated from habitat, winner may utilise resource more efficiently and so be more successful or it may enable it to compete more efficiently, outcome may be determined by environmental conditions.

Question 21

What happens in grazing, parasitism + predation interactions?

Answer 21

One species gains whilst the other loses.

Question 22

Why is it advantageous for a parasite not to kill its host?

Answer 22

This would result in the parasite being required to find a new host to survive, often it provides the ideal conditions for reproduction + survival.

Question 23

Give examples of parasites.

Answer 23

Flea, tapeworm, malarial parasite, common tar spot fungus + Dutch elm disease parasite.

Question 24

Give examples of mutualism.

Answer 24

Bacteria in cattle intestine, lichens (made of fungi + algae) + nitrogen fixing bacteria (bacteria live in nodules of legume roots + gain carbs from plants who get amino acids)

Question 25

What are 3 types of organisms which are natural enemies of insect pests?

Answer 25

Predators, parasitoids + pathogens.

Question 26

Why are broad spectrum pesticides bad?

Answer 26

Don’t work particularly well with pest, may kill many beneficial organisms including natural enemies of pest. Pest can experience pest resurgence.

Question 27

What are the 2 types of succession?

Answer 27

Primary + Secondary Successsion

Question 28

What are 3 species types throughout a succession?

Answer 28

Pioneer species, intermediate species + climax community.

Question 29

Describe the stages of primary succession.

Answer 29

Pioneer plants arrive, colonisers modify abiotic environment during subsequent growth, repro, death + decomp cycles (humus development), habitat can now support more advanced species’ as less hostile as soil forms + plant growth provides shelter for other organisms, larger plants thrive so vegetation height + biomass increases + finally climax community formed as K-Selected species’ present form stable environment.

Question 30

What are some trends as succession develops?

Answer 30

Soil depth + fertility increases, species diversity increases (may decrease at maturity), plant biomass increases, more niches, more complex communities + more stable food chains + food webs.

Question 31

What can zonation in sand dunes represent?

Answer 31

Development of community over hundreds of years.

Question 32

Why do most successions occur?

Answer 32

When normal succession is interrupted by fire, flooding or human activities. Known as secondary succession.

Question 33

Describe secondary succession.

Answer 33

Development of community is more rapid as soil already present to support larger plant species’ + some can regenerate or germinate when abiotic conditions become favourable. Many soil organisms still present so climax community reached much faster.

Question 34

What scale can be used to represent the change in nums of microbes over time + why?

Answer 34

A logarithmic scale. As increase can be over several orders of magnitude, Time (x) is scaled normally but num (y) has log scale. Special semi log graph paper can be used.

Question 35

Why does the stationary phase and rapid fall of decline phase occur?

Answer 35

Resources being non-renewable as nutrients aren’t replaced.

Question 36

Are all predator-prey curves normally so extreme?

Answer 36

As the predator usually has multiple sources of prey, it is generally smoother.

Question 37

Why is biological control better than pesticides?

Answer 37

No chemical damage to environment or bioaccumulation, only targets pest species, resistance unlikely, resurgence unlikely + needs little add action + saves money on continued use of pesticides if successful.

Question 38

Why does pest resurgence occur when pesticides are used?

Answer 38

There are a small num of resistant pests. When pesticide sprayer, not resistant pests all die, resistant reproduce and create an entirely resistant population.

Question 39

What are the limitations of biological control?

Answer 39

Pest not totally eliminated, only works if predator can survive in that environment + introduced species must not outcompete native species as causes harm to non target species.

Question 40

What are 4 differences between parasites + predators?

Answer 40

Parasites don’t kill the host, whilst predators do.
Parasite lives in/on host whilst predator doesn’t.
Predators have populations which fluctuate more.
Parasites are usually small than host.

Question 41

What is the equation to estimate population size?

Answer 41

(N1 x N2) / n
N1 = first total collected
N2 = second total collected
n = number from first in second

Question 42

Why do sand dunes continue to develop?

Answer 42

Sand blown by wind/force of sea forms new dunes close to high tide mark.

Question 43

What are dune slacks?

Answer 43

Small areas of grassland with degree of protection + rich in moss, ground hugging plants, snails. Best biodiversity. Further inland is heather, then bracken + gorse, then woodland.

Question 44

Why would a scientist use an exponential curve to represent an r selected species population growth?

Answer 44

Their growth is unlimited due to plentiful resources and little competition.

Question 45

Why might students get different numbers when counting using a haemocytometer?

Answer 45

Flask mightn’t have been swirled properly before they took samples or added too much solution to haemocytometer or samples not obtained from same depth. Counted dead cells.

Question 46

How might a scientist justify the killing of a population of reindeer in an area where they have been introduced for whalers?

Answer 46

They’re not native or endangered, species diversity decreased due to them. Whalers don’t need them. Only a few species successful.

Question 47

How might a farmer increase carrying capacity for a crop species?

Answer 47

Fertiliser or draining.

Question 48

If scientist are considering designating an area as a nature reserve because it contains a new species of grasshopper, what should they further investigate first?

Answer 48

Whether they migrate away at diff seasons, sample diff habitats to see if they are anywhere else, analyse repro rates, determine if they’re a pest.