Populations Flashcards
What is a population?
Group of interbreeding organisms of one species in a habitat
What is a community?
All the populations of different organisms living and interacting in a particular place at the same time
What is a habitat?
A place where a community of organisms live
What is a microhabitat?
Smaller units within each habitat
What is a niche?
How an organism fits into the environment (ie where it lives).
Includes both biotic and abiotic conditions required for it to survive, reproduce and maintain a populations
Name biotic factors
Human influence Competition Predation Dispersal Pollination Mimicry Antibiosis
Name climatic abiotic factors
Light Water Temperature Humidity Air currents Water currents
Name edaphic abiotic factors
Topography Mineral content Air content Biotic content Organic content Water content PH Temperature
How would you use a quadrat when counting moss?
Can’t count so estimate the percentage of the grid it covers
Describe how you would estimate the number of XXX in a small woodland?
Split area in sections Find random coordinates Count frequency in quadrat Calculate mean per quadrat Mean per quadrat x by number of sections
When do you use transects instead of guadrats
If you want to see changing conditions
If you’ve observed an area using a transect and want to see if it’s valid what could you do?
Repeat in a slightly different place e.g. A meter along
What are the problems when collecting data on animals?
They move
Their behaviour changes
Describe the mark, release and recapture method
Capture a sample Count them Mark them Release them Later, randomly select second sample Count how many marked
Estimated population = 1st sample xs 2nd sample divided by number of marked recaptured in 2nd sample
What could effect the mark, release recapture method?
If they don’t mix evenly when put back
Behaviour changes
Population changes (eg births/deaths)
Suggest how the shape of an animals mouth is an adaptation to its niche
Different shape mouth catches different foods
Competition between species reduced
What abiotic factors can effect the population size and how?
Water (not many species adapted for dry conditions & humidity effect transpiration rate & water evaporation from mammals)
Temperature (denture enzymes or slow down rate of reaction)
Light (increase photosynthesis so grow more so more food for animals)
PH (effect enzyme action)
What is the density dependence growth?
Population grows then remind stable after reaching a certain size
Limiting factors usually food and toxic waste accumulation
Describe the 3 parts to a graph of number of organisms against time
Slow growth Then Rapid growth (as plenty resources) Then No growth, stable state & possibly small fluctuations due to changes in factors eg food supplies
What is density independence growth?
Population grows and reminds stable until some factor causes dramatic reduction in size eg disease
What is intraspecific competition?
Same species compete for resources
What is interspecific competition?
Different species compete for resources
What is the competitive exclusion principle
2 species in the same niches compete
1 has an advantage so increases size
Other decreases in size
If conditions stay the same, 2nd species will be completely removed
Why can’t 2 species remain in the exact same niche?
Resources or limited
Competitive exclusion principle may occur
