Populations Flashcards
(44 cards)
What is an ecosystem?
All of the living organisms and non-living components in a specific habitat and their interactions.
What are abiotic factors?
Non-living factors affecting organisms (e.g. temperature, light intensity).
What are biotic factors?
Living factors affecting organisms (e.g. food supply, predation).
What is a community?
All of the organisms of different species in a habitat.
What is a population?
All of the organisms of one species in a habitat.
What is a habitat?
The place where an organism lives
What is a niche?
The role of a species in an ecosystem, governed by adaptation to biotic and abiotic conditions (e.g. what it eats, what temp it can tolerate)
What is the biosphere?
The entire volume of the Earth’s surface where living things can be found.
What is a biome?
A large, naturally occurring community of flora and fauna occupying a major habitat.
How do you reduce the chance that a sample is not a true reflection of the population?
-Samples must be taken at random to avoid bias.
-Enough samples must be taken to get a representative result with a reliable mean, where anomalies can be calculated.
How is abundance measured?
By counting the frequency of a particular plant species (number of plants in a quadrat) or measuring % cover (area of a quadrat that is covered by a particular species).
What is the method for random sampling?
1) Place 2 long tape measures at right angles to each other as axes in the area to be studied.
2) Generate random numbers using a calculator etc.
3) Use these as coordinates on the axes to place the quadrats.
4) Count the number of plants of each species or estimate the % cover of each species in a quadrat. Do at least 10 quadrats.
What is the method for belt transect sampling?
1) Place a long tape measure across the sampling area.
2) Place quadrats at regular intervals.
3) Count the number of plants of each species or estimate % cover of each species in each quadrat. Do at least 10 quadrats.
When is belt transect sampling used?
To study the change in biodiversity across a habitat where there is an environmental gradient, e.g. wet to dry.
When is random sampling used and not used?
To avoid bias and study the biodiversity in an area where plants are randomly or uniformly distributed.
Not used if plants are grouped in clumps.
What is standard deviation?
A measure of the spread of data about the mean.
What does it mean if standard deviation bars overlap?
There is no significant difference in the 2 means, so they could be down to chance
What does it mean if standard deviation bars don’t overlap?
There is a significant difference between the 2 means
What does a null hypothesis suggest?
That there is no significant difference or significant correlation.
What does it mean if the p value is < 0.05?
The difference/correlation is significant because there is a less than 5% probability that the difference/correlation is due to chance.
Suggest 2 advantages of estimating % cover rather than counting plants
-It’s quicker
-It may be hard to define individual plants
Why are mobile animals hard to capture?
They move quickly and try to hide.
Explain the process of the mark-release-recapture technique to estimate population size
-Capture a large sample of animals using a trapping technique.
-Count all of the animals in the first sample (S1) and mark them using non-toxic paint etc.
-Release all the animals in the first sample and give them time to mix with the rest of the population.
-Capture a second sample of animals using the same trapping technique.
-Count all of the animals in the second sample (S2) and record how many of these are marked (R).
-Use the equation S1xS2 / R
What are the conditions for a valid estimate using the mark-release-recapture method?
-The mark does not affect survival.
-The mark persists during the investigation.
-The marked animals have enough time to mix randomly with the rest of the population.
-No births, deaths, immigration, or emigration between the first and second sample, so the population size remains constant.
