Module 6 Flashcards
sampling should be module 4
Distribution
Where individual organisms are found within an ecosystem. Is usually uneven throughout the ecosystem as they are generally found where abiotic factors favour them, so their survival rate is high due to having all the resources they need and low predation.
Measuring distribution by systematic, non random sampling
- A line transect is where a line of surveyor’s tape if layed on the ground and samples are taken at regular intervals and describing organisms which touch the line or are are a certain distance away
- A belt transect provides more information and 2 parallel lines are marked and samples are taken in the area between these specific points.
What is an advantage of systematic sampling?
Systematic sampling identifies different areas within the overall habitat to sample separately which allows scientists to study how the differing abiotic factors in different areas of the habitat affect the distribution of species. Can show how plant species changes you move inland from the sea.
Abundance
The number of individuals of a species present in an area at any given time. This may fluctuate daily dur to immigration and births, and emigration and deaths.
What is a population?
Why is abundance hard to measure and how can you make it more accurate?
- A population is a group of similar organisms living in a given are at a given time. They can rarely be counted accurately as not all can be caught and it can be time consuming to count all the members, or the counting process could damage the environment. We therefore estimate using sampling techniques.
- To increase accuracy, use as large a sample size as possible as there is a lower probability that chance will influence the result. Random sampling should be used to reduce bias.
How do you measure plant abundance?
Quadrats are placed randomly in an area and the number of individuals contained in the quadrat are counted.
The number of individuals and area of sample are all the quadrat samples added together

Why can you measure aniamls with quadrats?
What do you need to ensure when handling animals?
How do you measure abundance of animals?
- Animals move so can’t measure with quadrats
- Handle carefully and for as short time as possible
Capture-mark-release-recapture is used to estimate population size
- Capture as many individuals as possible in a sample area
- Mark or tag each individual in a way that doesn’t harm them- toxic paint or reverse camo. Can clip small part of fur or mark snails inside shells
- Release the marked animals back into the sample area and allow time for them to redistribute themselves throughout the habitat
- Recapture as many individuals as possible in the original sample area
- Record the number of marked and unmarked individuals present in the sample (release all individuals back into their habitat.)
- Use Lincoln index to estimate the population size

What is the equation to estimate population size for capture-mark-release-recapture?
What does a greater number of marked individuals captured mean?
How can you compare species eveness?
How do you calculate biodiversity from this?
(SS)
smaller population.
compare the total number of each organisms present
use the Simpsons index of diversity (SS) where D is the chance that any 2 individuals picked at random will be from different species

How is species frequency and species density calculated with quadrats?
Species frequency- calculate the percentage of quadrats that included each species
Species density- the number of individual organisms within a quadrat
How do you identiy organisms?
identification key are used which can contain images to identify the organism into a particular species based on the presence of a number of identifiable characteristics
Why is random sampling used?
How is it done with quadrats?
What is ACFOR?
How are aniamls measured by random sampling?
Reduces bias
- Can place tape measures at right angles to each other along the 2 sides of the sample area and random numbers are generated using an app to give coordinates of where to put the quadrats
- Count number of individuals in the girds. Often have to do % cover for plants as its hard to see the individual plants by estimating or by counting the number of squares the species is present in and converting to a %
- Calculate mean then multiply by total area
- Sometimes species are too numerous to count and plants cant always be isolated to an abundance scale like ACFOR is used (abundant, common, frequent, occasional, rare). First you decide how many plants/ animals have to be present to be considered common…. This speeds up recordings.
Animals are harder as they can be small, and lots just appear at night. Instead of quadrats they use:
- Beating trays- a large white sheet is placed on the ground or supported by struts and held below a tree. The tree is shaken to dislodge animals.
- Pooter- scientists can use this to suck small animals into a gall or plastic tube. Can use it to collect animals from a beating tray.
- Sweep net- large nets catch flying insects and insects that live in long grass
- Pond net- stronger nets lift water from pond and rivers and the water drains through to leave vegetation and animals behind
- Pitfall traps- cans or jars buried in the ground filled, with paper or cardboard to provide shelter, and covered with a lid or stone to keep out rain. Collects ground dwelling insects which are often nocturnal. Deep enough they cant crawl out
- Kick sampling- study organisms in a river to disturb the substrate. Net downstream for set period of time captures organisms
- Slow moving like muscles can be measured using quadrats
- Tullgren funnel
Why can non-random sampling be good?
What are the types of non random sampling?
Random sampling can take too long
Opportunistic sampling:
Walk around until you find an area convenient to sample. However, the area you chose may not be representative of the area. If you don’t have time to look anywhere else, often students pick places easy to reach, safe and don’t involve walking too far.
Stratified sampling:
In ecosystems there may be different habitats occupying different proportions of the total area. To get a fair representation of the biodiversity in the ecosystem, its bets to estimate the proportion of total area occupied by these habitats and then sample accordingly. If 10% if woodland, then 10% of samples should be taken from woodland.
Systematic sampling:
If there is an abrupt change from 1 habitat to another or a gradual change in conditions across the area random sampling won’t reflect the distribution. Transects. Line transect results are converted into a drawing which shows distribution. Shows change down a gradient, like a slope or changing abiotic feature. Belt transects can be continuous or is the distance is long then at regular intervals. Results are converted into a kite diagram. Is biased as you choose where to put the transect and this area may not be representative but is easier as don’t have to measure coordinates.
Why are abiotic factors measured?
What is the advantage of being measured with sensors?
How are the measured?
Needed to draw conclusions about the organisms present and the conditions they need for survival so measured at every sampling point
Can be measured quickly and accurately with a range of sensors which are good because;
Rapid changes can be detected
Human error in taking readings is reduces
A high degree of precision can be achieved
Data can eb stored and tracked on a computer
- Needed to draw conclusions about the organisms present and the conditions they need for survival so measured at every sampling point
Can be measured quickly and accurately with a range of sensors which are good because:
- Rapid changes can be detected
- Human error in taking readings is reduces
- A high degree of precision can be achieved
- Data can eb stored and tracked on a computer
(SS)

Describe this population growth curve
What is the population growth curve of organisms that reproduce asexually?

2- no constraints act to limit the population explosion
3- fluctuations due to fluctuations in limiting factors like predators
Organisms that reproduce asexually can produce a J shaped curve as they exploit the resources when they become available. They reach a peak and then crash often before carrying capacity is reached. They are often controlled more by abiotic factors
Examples of limiting factors for population growth
EG. Competition for resources, build-up of toxic by-products of metabolism, disease
Abiotic- non-living like temp, pH, water availability, oxygen availability, humidity. Remain constant when population density changes.
Biotic- living like predators, disease, competition. Have greater affect when population density increases.
Carrying caacity
the maximum population size an environment can support
Envrionemtnal resistance
the combined effect of that prevent the further increase of a population
Why can migration happen and what are the types?
Can happen when an area reaches its carrying capacity
Immigration- movement into an area increases population size
Emigration- individual organisms move away from a particular area and decrease population size
What are density independent factors?
factors that have an effect on the whole population regardless of size. They can dramatically change the population size. EG- earthquake, fires, volcanic eruptions, storms. They can even remove whole populations of a species from a region.
What type of factor is competition?
Interspecific competition
Intraspecific competition
biotic
competition between different species
competition between members of the same species
Interspecific variation
example
Results in a reduction of the resource they are competing for for both populations. EG food, means less energy for growth and reproduction so smaller populations result.
If 1 is better adapted, then the less well adapted one is likely tot be outcompeted and f conditions remain the same then the less well adapted species will decline in number until it no longer exists in that habitat- competitive exclusion principle
EG. Grey squirrel native to N America was introduced to UK causing the native red squirrel to disappear in many areas as the grey can eat a wider range of food and is larger so can store more fat so has better chance of survival and ability to reproduce An increasing population of greys further reduces food supply for red
Intraspecific variation
Greater availability of resources means larger population size can be supported. This creates fluctuations in number of organisms over time
(SS):
1- plentiful resource for all organisms to survive and reproduce causes population size to increase
2- due to increased population, the resources are limited so population decreases as not enough for all to survive
3- less competition due to smaller population so more survive and reproduce

Niche
the role of a species in a habitat, including its trophic level, its interactions with the abiotic environment and interactions with other species eg as a predator, host or a symbiont, parasite or pollinator. Species with similar niches the competition will be more intense
Competitive exclusion
when individuals of different species compete for the same resources, one species may succeed and the other be excluded from the niche and completely disappear






