19.0 Populations in ecosystems Flashcards
Define species
A group of similar organisms that reproduce to produce fertile offspring
Define population
All the individuals of a particular species in a particular place
Define community
All the populations of different species in a
particular place
Define niche
An organisms role in an ecosystem
Why can two species not occupy the same niche?
Interspecific competition
What is a limiting factor when talking about populations?
A factor which would limit the growth of a
population
Give an example of a limiting factor in a population
Nutrients, mineral ions, light, temperature,
predators, disease.
Give examples of abiotic conditions that could limit a population
Temperature, light, pH, water and humidity.
What is the name given to the maximum size a population can become?
Carrying capacity
Describe the steps in the predator-prey relationship
- prey increases in number so more food available
for predator, predator increases in number, - predator eats more of the prey, prey decreases,
less food for predator so predator number then
decreases this causes an increase in prey number
and cycle repeats. - slight timelag between prey
and predator events
Beside predator prey interactions, what else can cause fluctuations in populations?
Disease and climatic factors
Why do changes in conditions and number of predator as affect evolution?
hey create a selection pressure this means that the best adapted survive to reproduce
Define each type of competition
- Interspecific competition which occurs between
organisms of different species. - Intraspecific
competition which occurs amongst members of
the same species.
What are the two main types of quadrat?
Point and frame
What are the 3 factors to assess when using quadrants?
- Size of quadrat
- Number of quadrats
- The position of quadrats
How do you sample randomly?
Lay out 2 tape measures at right angles, create
random coordinates, place quadrat at
intersection.
What is a belt transect?
A method of systematic sampling. It measures
change of a certain distance. frame quadrats are
laid along a tape at set points.
What are the two methods of measuring abundance?
Frequency and percentage cover.
How is frequency measured in terms of populations?
This is the likelihood of a species to be present in
any quadrat. It is given as a percentage.
How is percentage cover measured in terms of populations?
This is an estimate of of the area a particular
species covers a quadrat. It is good for fast
measurements without measuring individual
organisms.
How are sampling results made more reliable?
Larger numbers of quadrats are used
How can you carry out the mark release recapture technique?
- capture animals over a certain period of time,
mark them (make sure tag does not affect
survival chances) - release them, wait for a time, capture animals again over same time period.
- Estimate population size by number in sample 1
x number in sample 2) / marked in sample 2
What assumptions does the mark release recapture technique have?
No births or deaths, no migration, mark does not
affect survival chances
What is succession?
How an ecosystem changes over time. Each
organism makes the environment less hostile and
is then outcompeted by better adapted species
What is the first stage in succession?
Pioneer species settle
What are the two types of succession?
Primary (occurs on new land) and secondary
(occurs on previously colonised land)
What is the final stage in succession known as?
Climax community
What is conservation?
Management of of the Earth’s resources by
humans so they can be used in the future
What conditions does conservation maintain?
Ecosystems and biodiverasity
Why does conservation take place?
Personal, ethical, economic, cultural and
aesthetic
