Biodiversity and Sampling
What are the three levels of biodiversity?
Genetic diversity, species diversity and ecosystem diversity.
What type of population growth produces a J-shaped curve?
Exponential growth.
What is the original source of energy for most ecosystems?
Light energy from the Sun.
What type of interaction occurs when both species benefit?
Mutualism.
What is ecological succession?
The gradual change in species composition and community structure of an ecosystem over time.
A quadrat contains 12 individual daisies, 6 clovers and 2 grasses.
What is the species richness of this quadrat?
3 species
What is the formula for the Lincoln index?
N=M x n/m
where:
What process converts light energy into chemical energy in producers?
Photosynthesis.
A tick obtains nutrients from a dog while harming the dog.
Parasitism.
What is the key difference between primary and secondary succession?
Primary succession begins where there is no soil, while secondary succession occurs where soil remains after a disturbance.
A researcher wants to investigate how plant species change from the edge of a forest into the centre of the forest.
Which sampling technique would be most appropriate?
A belt transect because it allows species abundance/distribution to be measured along an environmental gradient.
Researchers mark 40 fish in a lake. Later, they capture 50 fish, of which 10 are marked.
Estimate the total population
N = 40x50/10, N = 200
An ecosystem has a producer biomass of 20 000 kg and primary consumer biomass of 2 000 kg.
Calculate the percentage biomass transfer between these trophic levels.
2000/20000x100=10%
10% of the biomass was transferred
Two bird species live in the same forest and both feed on the same insects.
Explain how this could lead to interspecific competition.
Both species require the same limited food resource. Because the resource is limited, individuals of one species can reduce its availability to the other species, resulting in competition.
Give two characteristics of pioneer species that make them effective colonisers.
Possible answers include:
A researcher randomly places five 1 m² quadrats in a grassland. They find that most plant species occur in patches rather than being evenly distributed.
Explain why increasing the number of quadrats could improve the reliability of the investigation.
More samples are more likely to capture variation in the distribution of species and reduce the influence of unusually species-rich or species-poor quadrats, producing a more representative estimate
A population initially contains 800 individuals.
During one year:
Calculate the population growth rate as a percentage of the original population.
Population change=(120+30)-(70+50)
=150-120=+30
Explain why only a fraction of the energy stored in producers becomes available to primary consumers.
Energy is lost through processes including respiration and heat production, and some biomass is not consumed or is not completely digested. Therefore, only part of the producer's stored chemical energy becomes biomass available to the next trophic level.
What is the competitive exclusion principle?
Two species competing for the same limiting resources in the same niche cannot coexist indefinitely if their requirements are identical. One species will eventually outcompete the other, or the species will undergo niche differentiation.
After a bushfire, grasses and small plants rapidly colonise an area. Over time, shrubs and trees become more abundant.
Explain how this change could affect biodiversity and biomass
As succession progresses, habitat structure becomes more complex, potentially increasing the number of available niches and therefore biodiversity. Larger plants accumulate more organic material, causing biomass to increase
Two ecosystems each contain four species.
Ecosystem A:
Species A = 25, B = 25, C = 25, D = 25
Ecosystem B:
Species A = 85, B = 5, C = 5, D = 5
Which ecosystem has greater biodiversity? Justify your answer using species richness and evenness.
Both have the same species richness = 4, but Ecosystem A has much greater evenness because individuals are distributed equally among species. Therefore, Ecosystem A has greater overall species diversity.
A population initially contains 800 individuals.
During one year:
Calculate the population growth rate as a percentage of the original population.
Change=120+40-80-100=-20
Growth rate =-20/800 x 100= -2.5%
The population decreased by 2.5%.
A food chain contains:
Grass → Grasshopper → Frog → Snake
The grass stores 50 000 kJ of energy.
If the transfer efficiency is approximately 10% at each trophic level, approximately how much energy reaches the snake?
Grass → grasshopper:
50000 x 0.1 = 5000
Grasshopper → frog:
5000 x 0.1 = 500
Frog → snake:
500 x 0.1 = 50
Approximately 50 kJ reaches the snake.
A sea ecosystem contains sea urchins, algae, predatory fish and a particular predatory species that keeps sea urchin populations low.
The predatory species is removed.
Predict how this could affect the ecosystem.
Removal of the predator could cause sea urchin numbers to increase. Increased grazing could reduce algal abundance, potentially altering habitat availability and food resources for other species. This demonstrates how removal of a keystone species can cause disproportionate changes to community structure
A drought causes a major reduction in water availability in a grassland ecosystem.
Predict how the drought could affect:
A. carrying capacity
B. population size
C. competition
D. biodiversity
A. Carrying capacity: decreases because less water is available to support organisms.
B. Population size: may decrease as mortality increases and reproductive success decreases.
C. Competition: likely increases because organisms are competing for a more limited resource.
D. Biodiversity: may decrease because some species may be unable to tolerate the changed conditions.