Chpater 19 - Populations In Ecosystems Flashcards
(40 cards)
What do the terms biotic and abiotic refer to?
Biotic = a factor that makes up part of an organism living environment (e.g. competition and predation with other living organisms)
Abiotic = a factor that makes up part of an organism’s non living environment (temp, pH, rainfall)
What do the terms biosphere and ecosystem refer to?
Biosphere = the regions of the earths surface and atmosphere that support life
Ecosystem = a dynamic system involving interactions between all the living and non-living components of a particular area
What does the term niche mean in regards to environment and the term carrying capacity?
Niche = describes how an organism fits into an environment
- it refers to where an organism lives and what it does/ the role it has there.
Carrying capacity = the maximum population size of a species that an ecosystem can support
List the abiotic factors affecting population size [4]
- Temperature - each species has an optimum temp for survival
- Light - the ultimate source of energy for ecosystem (affects rate of photosynthesis for producers)
- pH - every species has an optimum pH which it operates most effectively as pH affects enzyme action
- Water and humidity - water is required for life, where water is scarce, populations will consist mainly of species adapted for dry conditions. Humidity affects transpiration rates in producers
What is the term used to describe bacterial cells multiplication?
Exponential
What’s the formula for calculating number of bacterial cells if a culture of bacteria increase by a factor of 2 in each generation?
N = No x 2^n
No = initial number
n = number of divisions
When is a log scale used on y axis?
When numbers increase rapidly and become so large
What do the terms immigration and emigration mean?
Immigration - where individuals join a population from outside
Emigration - where individuals leave a population
How is population growth calculated?
= (births + immigration) + (deaths + emigration)
How is population growth rate as a % calculated?
Population change during period / population at start of period x 100
What does the term competition mean and what are the 2 types?
Competition = when 2 or more individuals share any resource that is insufficient to satisfy all their needs fully
- intraspecific = when individuals of SAME species compete for resources. The availability of resource determines size of population
- interspecific = when individuals of DIFFERENT species compete for resources. One species will have competitive advantage over other causing it to increase in size and others diminish
What is the link between predators and prey?
When predators population size increase, the preys population size decreases
HOWEVER
When the predators population size decreases, the preys population size increases
Describe binary fission [3]
- Replication of circular DNA
- Replication of plasmids
- Division of cytoplasm to produce daughter cells
What are quadrats in terms of investigating populations?
They are square frames of a known size that are divided into smaller segments that can be used to investigate populations of non-motile species
What are the factors to consider when using a quadrat?
- size of the quadrat
- number of quadrat samples to record
- positions of each quadrat within the study area
Describe how you would use a quadrat to measure population size through random sampling [6]
- Divide the area that you want to sample into a grid and use a random number generator to select coordinates in that chosen area
- Find each coordinate and place a quadrat on the ground in that position
- Use quadrat to measure the abundance of the organism of interest
- Repeat using many randomly generated coordinates to obtain a large sample
- Calculated the mean number of organisms per m²:
= total number of organisms/ number of quadrats - Calculate population size:
= mean number x total area
What are the two ways for measuring population size of a specific organisms in an area?
- Count number of a particular organism in the quadrat
- Estimate the % of the quadrat that was covered by the organism.
- Count number of squares that are more than half covered and divide that number by total number of squares in quadrat and x100
What is a belt transect?
Transects are used to study the effect of a factor on the distribution of a species across an area, in a straight line.
How is systematic sampling done along a belt transect?
- Lie out a tape measure across the area that is being studied
- Place a quadrat at regular intervals along the tape measure (eg. every 2 metres) and the abundance of organisms is counted at each
What are the 3 main statistical tests?
- students T test
- chi-squared
- Spearman’s rank correlation coefficient
What are the null hypothesis’ for each statistical test?
- Students T test = no statistically significant differences between the means of sample x and sample y
- Chi-squared = no statistically significant difference between the observed and expected frequencies
- Spearman’s rank correlation coefficient = no statistically significant correlation between x and y
How does Spearman’s rank correlation coefficient work?
- rank the number of (?) from highest to lowest
- if two numbers are the same, then find the difference (e.g 7 and 8 = 7.5)
- then skip the next number (8 skipped so go to 9)
What is the rs equation for Spearman’s rank correlation coefficient?
Rs = 1- 6∑D² / n(n² - 1)
Rs = spearman’s rank correlation coefficient
D = difference between rankings for two variables being investigated
n = number of pairs of observations
After calculating Spearman’s rank correlation coefficient, what is done next?
Use table to find critical value:
- Df = number of pairs - 2
- then look along the p value of 0.05
