Populations Questions Flashcards
Define community (1)
Organisms of all species in an ecosystem/habitat
Give two conditions necessary for results from mark release recapture investigations to be valid (2)
No migration
No reproduction
Idea of mixing
Marking does not increase vulnerability to predation
Sample large enough
What is the formula for estimated population size in mark release recapture methods?
Number of marked individuals recaptured
Explain how you would use a quadrat to estimate the number of dandelion plants in a field measuring 100m by 150m (3)
Randomly place quadrants
Done by getting coordinates from random number generator
Calculate mean per quadrat
Multiply to give estimate for total field
Two species are thought to have evolved as a result of sympatric speciation. Suggest how this might have occurred (4)
Original population living in one area
Idea of genetic variability
Reproductive isolation
Gene pool becomes increasingly different
Until interbreeding does not produce fertile offspring
What is an ecosystem (1)
A self supporting system in which all organisms interact with the physical environment
Pygmy weed competes with naturally occurring plants. Suggest how the introduction of Pygmy weed may lead to a reduction in the diversity of the community in a natural pond. (3)
Pygmy weed competes for CO2, light, nutrients
Some of original plants species lost
Loss of food sources
Consumers die
Fur seals feed on krill. Many species of whale living in Antarctic seas feed on krill. Explain how an increase in whaling might have resulted in an increase seal population (2)
Fewer whales means more krill
More krill feeding fish
More food for seals
Give two advantages of collecting quantitative data about plant distribution as percentage cover (2)
Data can be collected rapidly
Does not require defining individual plants
A team of biologists investigated a method for measuring the abundance of shrews. They used plastic tubes called hair tubes. Some of the hairs from a shrew that enters one of these tubes stick to glue in the tube, these can be used to identify the species of shrew.
Funagoo glue remains sticky after wetting and drying. Explain the advantage of using this (1)
Will work in all weather conditions
A team of biologists investigated a method for measuring the abundance of shrews. They used plastic tubes called hair tubes. Some of the hairs from a shrew that enters one of these tubes stick to glue in the tube, these can be used to identify the species of shrew.
The biologists partly blocked the entrances to the tube with tape. Suggest why (1)
So shrews come into contact with glue
Biologists collected hairs from shrews of each species. Explain why they selected these hairs at random.
Avoids bias
Explain why it is important to check the repeatability of measurements (2)
It increases the reliability of the measurements.
If measurements are repeatable differences are less likely to be due to personal error / anomalies unlikely
You could use a scatter graph to check the reliability of measurements made by two observers. Describe how. (2)
Plot graph of one set of results against the other
Expect to see points lying close to the line
Define population (1)
Organisms of one species in an ecosystem/habitat
A team of biologists investigated a method for measuring the abundance of shrews. They used plastic tubes called hair tubes. Some of the hairs from a shrew that enters one of these tubes stick to glue in the tube, these can be used to identify the species of shrew.
Explain why they could not use the hair tubes to find the total number of shrews present (1)
Shrews may enter more than one hair tube
Many hairs from same shrew
Shrews enter without leaving hair
Explain why a statistical test was necessary in analysing the results for the common shrew. Use the terms chance and probability in your answer (2)
A statistical test determines the probability of the results being due to chance
Determines wether correlation is significant
Describe how you would decide the number of quadrants to use in order to collect representative data (2)
Calculate a running mean
When enough quadrants, this shows little change
A large number to make sure results are reliable
In June young birds leave their nests and join adults. Using mark release recapture to estimate the size of the blue tit population in June would not give reliable results. Explain why (2)
Population changes
As young birds leave their nest / join population
In March each pair of adult birds forms a separate territory. The pair stays in this territory while breeding. Using mark release recapture to estimate the size of a blue tit population in March would not give reliable results. Explain why (2)
Would be likely to catch all birds again in second sample
Birds in territories and not mixing with population
Territory sample not representative
When whales come to the surface to breathe scientists obtain small samples of their skin. The scientists find the base sequence in some of the DNA from these samples. The base sequence is different in each whale.
You could use information about the base sequence to estimate the size of the whale population by using mark release recapture. Explain why (2)
Recording base sequence is like marking the animal
Finding same base sequence would show animal has been recorded before
A scientist measured human disturbance by walking firm one end of the beach to the other. He recorded the number of people he encountered.
Site R - 2.2 (+/- 2.1)
Site G - 17.6 (+/- 9.6)
Site U - 34.6 (+/- 11.6)
What conclusions can you draw about the number of people visiting site R compared with the other sites?
Fewest people at site R as mean is lowest
Standard deviations do not overlap so significant / not due to chance
A scientist reported that the difference between the number of people visiting site R and the number visiting the other two sites differed significantly (p
There was a probability of less than 0.05
That the difference was due to chance
A scientist measured the dry biomass of seaweeds at sites R, G and U. He collected all the organisms of a particular species in a quadrat and incubated them in an oven at 80 degrees Celsius.
Suggest why incubating them at a higher temperature would not produce valid results (1)
Combustion would cause loss of dry mass
The ratio of the dry biomass of animals to the dry biomass of seaweeds is always a lot less than one. Explain why (2)
Seaweeds are producers
Loss of energy between tropic levels
As a result of respiration
Use the letters B (birth rate), D (death rate), E (emigration rate) and I (immigration rate) to show a population that stays the same size (1)
B + I = D + E
Use the letters B (birth rate), D (death rate), E (emigration rate) and I (immigration rate) to show a population that is increasing in size (1)
B + I > D + E
Suggest one reason for the increase in life expectancy since 1990 (1)
Improved medical care
Improved nutrition
Improved sanitation
Less disease
In 2007 the population was 107million
The birth rate was 20 per 1000
The death rate was 5 per 1000
Calculate the size of the population in 2008 (2)
107,000,000
————— x 15 = 1605000
1000
107,000,000 + 1605000 =108605000
If maximum life expectancy is 95. How could a graph be used to find average life expectancy (2)
Find value when 50% still alive
Use to calculate as a percentage of 95
In a demographic transition give one factor that might cause an increase in birth rate (1)
Better prenatal care
More people survive to reproductive age
Better nutrition of mother
In a demographic transition, give one factor that might cause a decrease in death rate (1)
Better nutrition
Better sanitation
Introduction of healthcare
Vaccination programmes
The population in 1851 was 18 million
The birth rate was 34.3 per 1000
The death rate was 22.0 per 1000
Calculate the size of the population in 1852 (2)
18,000,000
————– x 12.3 = 221400
1000
221400 + 18,000,000 = 18221400
One reason for the decrease in death rate between 1931 and 1951 was the introduction of mass vaccination. Explain how this would reduce death rate (2)
Creates herd immunity
Any individual has lower chance of meeting infected individual
Prevents spread of disease
What information is required in order to calculate the growth rate of a population (2)
Birth rate and death rate
Immigration and emigration
In a given time period
Ecologists could use the mark release recapture method to o estimate the number of one species of fish in a lake. Describe how (3)
Capture sample, mark, release
E.g. Mark with paint
Take second sample and count marked organisms
Population = (number in S1 x number in S2) divided by number marked in S2
A species of fish breeds at certain times during the year. During this season the mark release recapture method might not give a reliable estimate. Suggest why (1)
Population changes
Ecologists found that each species of fish had adaptations to its niche. One of these was the shape of its mouth. Suggest how this is an adaptation to its niche (2)
Specific mouth shape for specific food
Competition between species is reduced
What is interspecific competition (1)
Competition between species
What is intraspecific competition (1)
Competition within a species
Describe how you would place quadrats at random (2)
Split area into squares
Generate numbers from a computerised random number generator
Explain the importance of collecting lizards from a large number of sites when studying them (1)
Representative / identify anomalies
The population number of two species of lizard varied at different times of the year. Suggest two reasons why (2)
Temperature variation
Breeding
Food source
Scientists investigated the percentage of two lizard species infected with malaria at different sites on an island. They used the percentage of lizards infected at each site rather then the number. Explain why (2)
Number in sample varies
Allows a valid comparison
Newts are predators of the tadpoles of the spade foot toad. In a pond, suggest an explanation for the increased number of newts resulting in an increased percentage survival of the tadpoles of spring pepper frogs (2)
Newts feed on toad
Less competition for frogs
Feather mites are parasites found on the wings of many birds, they feed on the oil that the birds produce. This oil keeps the feathers in good condition. Birds unable to oil their feathers properly use more energy in maintaining body temperature. Suggest how feather mites could affect breeding in great tits (2)
Breeding less successful
Feathers in poor condition
So less energy for reproduction
Scientists located a large number of great tit nests. They sampled these at random, explain why they sampled the nests at random (2)
Avoids bias
Data representative
Allows use of a statistical test
Different fish species occupy different depths in a lake, suggest and explain one advantage of this to the fish (2)
Less competition
For food/prey/oxygen
