Populations Flashcards
Give a definition for a species
A group of organisms that can interbreed and produce fertile offspring
What is a population?
All the organisms of a particular species living in a habitat at a particular time
Define community
All living organisms of all species found in a habitat at a particular time
Define ecosystem
All the living organisms found in a self contained area and their interactions with the non-living abiotic factors.
What is an abiotic factors and give two examples?
None living feature of an ecosystem
Light intensity, temperature, pH, wind speed, water availability, mineral availability, wavelength of light, oxygen concentration
What is a biotic factor and give two examples?
Living features of an ecosystem
Predators, food availability, pathogens
What is a habitat?
The place where an organism lives within an ecosystem
What is meant by the term niche
The role of a species in a habitat consisting of both its biotic interactions eg what it eats and abiotic interactions eg time of day it is active
Two species can not occupy the same niche
What is meant by carrying capacity
The maximum size of population an ecosystem can support
What is meant by intraspecific competition?
Competition for resources between organisms of the SAME species
What is meant by interspecific competition?
Compensation for resources between organisms of DIFFERENT species.
Name three resources organisms might compete for.
Food, water, space/territory/shelter, minerals, light, mates (intraspecific only)
Describe how you would use a quadrat to estimate the size if a non-motile species
Two tape measures placed at 90 degrees to each other to form a grid
Random number generator used to identify coordinates
Quadrat placed at coordinates
Count the number of species
Repeat large number of times to gain a representative sample
Calculate mean number of the species
Carry out appropriate calculations to estimate the population in the whole area under surveillance
Describe how to carry out mark release recapture for estimating the size of a motile population
Capture a sample of the population and count
Mark the organisms
Release back into the habitat
After a period of time capture another sample of the population and count the number of marked and unmarked organisms
Use a formula to estimate the population size
What is the equation for estimating the population size using mark-release-recapture?
Population =
no. of organisms in first sample x total no. of organisms in second sample
——————————————————————————–
No. of marked individual recaptured
What assumptions does mark-release-recapture method make?
Marked individuals are evenly distributed in population
No migration or immigration
Large sample size
Few deaths or births
Method of marking does not affect survival
Mark does not come off.
What is succession?
The changes in the community that occurs over time in an area
Summarise the process of primary succession
Pioneer species can survive hostile conditions and colonise the area
Change abiotic factors in the environment eg decomposition increases minerals and soil depth
Allows more complex organisms to survive
What is a climax community and how is it reached?
Final stage of succession.
Ecosystem is balanced and stable
Soil is rich enough to support large trees
Environment is no longer changing
What is meant by the term conservation?
Protection and management of species and habitats to maintain biodiversity
Why is a log scale used on a graph recording the population of bacterial cells?
LARGE RANGE in numbers.
Allows patterns and trends to be seen
Describe how you would determine the mean percentage cover of grass on a sand dune.
Two tape measures placed at 90 degrees to each other
Random number generator used to identify coordinates
Quadrat placed at interception of coordinates
Estimate the percentage cover of grass
Repeat a large number of times to gain a representative sample
Divide total percentage in all samples by the number of quadrats taken
What is a pioneer species and how is it adapted?
First organisms to colonise a hostile environment.
Can survive with few minerals, little water, lack of soil.
Vast amount of wind dispersed seed/spores that can reach isolated areas.
Rapidly germination
Ability to photosyntheise
Give an example of a pioneer species and state how it is adapted
Lichen
Consists of algae that photosynthesise to produce organic material and fungus which reduces water loss.
Reproduce by spores
Which species follows after lichens in succession?
Mosses
How do animal populations change during succession?
Also undergo successional change
Determined by the different types of plants available for food and habitats.
What are the common changes that occur during succession?
Abiotic environment becomes less hostile
Greater number of and variety of habitats and niches
Increased biodiversity
Increased VARIETY of food sources
More complex food webs
Increased biomass
What is the difference between primary and secondary succession?
Primary succession begins on bare rock, with no soil. Takes longer to reach the climax community
Secondary succession starts on land that already has soil. Climax community achieved quicker.
When would use a transect?
Looking for a change in the organisms present over a certain distance.
Use when there is a transition in conditions
eg up a hill, a tidal seashore, distance from a source of pollution
How would you carry out a transect on a sand dune?
Place a tape measure from the sea edge of the sand dune away from the sea.
Place a quadrat at REGULAR intervals eg every 2 metres
Record the species present and relative amounts.
Repeat transect several time
Succession is …
How an ecosystem changes with time
Give examples of human activities that prevent succession.
Mowing lawn, grazing animals, managed fires
