Populations and ecosystems (BIOL4) Flashcards
Define population
All organisms of one species in a habitat
Define habitat
Part of an ecosystem in which organisms live
Define ecosystem
All organisms living in a particular area and all the non-living conditions
Define abiotic conditions
Non-living features of the ecosystem (temp, water availability)
Define biotic conditions
Living features of the ecosystem (predators, food)
Define niche
Role of a species within its habitat
Define adaptation
Feature that species have that increases their chances of survival and reproduction
Define abundance
No. of individuals of a species in an area
Define frequency
No. of samples species is recorded in
Define percentage cover
How much of an area is covered by a species
Define distribution
Where a species is within an area
What the the two types of sampling techniques?
Random and systematic
What is random sampling?
You don’t make a conscious decision of where samples are taken; prevents bias
How are random samples taken?
Divide land into grid, use random no. generator to select coordinates
What is systematic sampling?
Samples are decided
How is the number of individuals in an area estimated?
Mean x size area
What are the different types of quadrats?
Frame - square frames placed
Point - random no. generator to determine placement. Drop needle in hole, count what it touches
What are the different types of transects?
Line - record species touching tape at intervals
Belt - quadrats along belt, record percentage cover/abundance
What is the mark-release-recapture method?
Capture sample and count
Mark in harmless way
Release back into habitat
Take 2nd sample from same population
Count how many are marked
How do we estimate total population from mark-capture-release? (Lincoln Index!)
Total population = (no. caught in s1 x no. caught in s2) / no. marked in s2
What assumptions does the mark-release-recapture method rely on?
Sample had time to mix w/ population
Marking hasn’t affected chances of survival
Changes in population (deaths/births/migration) are small
What factors effect variation in population size?
Abiotic factors
Biotic factors
Predation
How do abiotic factors affect variation in population size?
When abiotic cond. ideal, organisms grow fast and reproduce or undertake metabolic reactions successfully
How do biotic factors contribute to variation in population size?
Interspecific competition - different species compete for same resources (food/space), results in out-competition due to one being better adapted
Intraspecific competition - same species; population inc. when resources plentiful; more organisms compete.
Resources become limited; population declines. Small population = less competition = population inc.
How does predation contribute to variation in population size?
Prey inc, more food for predators –> predator population inc.
More prey eaten –> prey population falls, less predator food –> predator population falls
Define species
Group of similar organisms that can reproduce to give fertile offspring
