Populations and Ecosystems Flashcards
Ecosystem
A group of inter-related organisms, their physical environments and interaction between living and non-living factors
Abiotic
Non-living, physical conditions
Biotic
Any living component that affects the population of another organism, or the environment
Population
Group of organisms of the same species living in the same habitat at one time
Community
All organisms of different species living in the same habitat at one time
Habitat
Place where a community of organisms live
Microhabitat
A small specialized habitat within a larger habitat
Niche
Role of a species in an ecosystem and its interrelationship between all the abiotic and biotic factors affecting it
Suggest how sudden changes in temperature can affect cold-blooded and warm-blooded organisms differently
- Can slow down or completely stop enzyme activity of cold-blooded organisms
- Warm-blooded organisms can maintain a constant body temperature but will have less energy for: growth (mature slowly) and reproduction
Suggest how light intensity can affect organisms
Impacts photosynthesis so growth of plants/ food source for other organisms
Suggest how sudden changes in pH can affect organisms
Impacts enzyme action so metabolic rates
Competitive Exclusion Principle
- if two competing species coexist they have different niches
- if there is no difference between niches of competing species then the least competitive will be eliminated
Suggest why it is difficult to prove that competition is the reason for variations in a population
- many abiotic factors affect population size
- time lag
- data on population size is difficult to obtain and not always reliable
Suggest why the population of prey is always greater than its predator
A single predator will eat several prey in order to survive
Suggest why predator-prey graphs have cyclic fluctuations
Disease and changes in abiotic factors
How to calculate population size of bacteria
Starting population x 2^n where n = no. of divisions
How to calculate growth rate
(no. of births - no. of deaths)/time
Carrying Capacity
Maximum population an ecosystem can support
Lag Phase
- not many individuals to start with
- not all individuals have reached breeding age
Exponential Growth
- no limiting factors, e.g. competition
- many organisms reproducing freely
Stationary Phase
- carrying capacity reached
- limiting factors provide environmental resistance to further growth
Death Phase
- resources exhausted
- accumulation of toxic waste
- arrival of new predator or disease
Succession
Changes over time in the species that occupy a particular area
Primary Succession
Process by which void and barren land becomes populated for the first time by a pioneer species
Pioneer species
- specially adapted to withstand a hostile environment
- first to colonise an ecosystem
- build up soil allowing larger, more complex organisms to survive
Features of pioneer species
- asexual reproduction by wind-dispersed seeds or spores which are easily dispersed
- wind resistant / adhere to rocks
- no cuticle so can absorb water over entire surface
- ability to fix nitrogen from air since no nutrients available
- tolerance to extreme temperature changes
- survive desiccation
- photosynthetic
Secondary Succession
Result of disturbance to landscape where species re-establish or change altogether to a new kind of biotic landscape
Suggest why succession is important
- creates new microclimates
- ensures high biodiversity
- results in many dominant species
Climax Community
- final stage of succession
- abiotic factors constant
- stable community / same types of species present
- population stable around carrying capacity
- (increased biodiversity)
- (great variety of habitats)
- (organisms fill almost all biological niches)
Hostile Abiotic Factors
- no water source
- windy (no shelter)
- lots of light
- extreme fluctuations in temperature
Explain why lichen is a pioneer species
Lichen (Algae and Fungus)
- Algae provides sugars from photosynthesis
- Fungus absorbs water and releases extracellular enzymes get minerals from rocks
Describe how to estimate population size using mark-release-recapture technique
- sample captured and marked with non toxic marking that does not affect their survival
- released into wild for long enough to disperse evenly amongst population
- (no. in first sample x no. in second sample)/ no. of marked recaptured
Suggest assumptions made when using mark-release-recapture technique
- proportion of marked to unmarked individuals => whole
- marked individuals distributed themselves evenly amongst population
- no immigration/emigration
- few deaths / births
- mark is not lost
- mark is non toxic and does impact survival of organisms, i.e. not noticeable to predators
Disruptive Selection
- selection against individuals with phenotypes around the mean
- favour individuals with both extreme phenotypes
Polymorphism
Different phenotype exist in the same (interbreeding) population of a species
Speciation
- formation of new species due to reproductive isolation in a species
- allele frequencies of demes become so different they can no longer reproduce to produce fertile offspring
Gene Pool
Alleles of all genes of individuals in a population at a given time
Allopatric Speciation
Populations become geographically isolated so cannot reproduce
Sympatric Speciation
Reproductive behavioural isolation that occurs while populations still occupy the same area
Genetic Drift
- change in allele frequency due to chance (e.g. natural disaster)
- impact greater on small populations
Explain why smaller populations evolve at a faster rate
- more genetic drift
- random mutations / elimination of individuals has a larger impact on allele frequency
Suggest reasons speciation occurs
- reproductive isolation
- geographically isolated
- different reproductive behaviours
- gamete incompatibility
Explain why larger mammals and birds are not found in a succession until the later stages
Vegetation not large enough to provide shelter (habitats) and food
Suggest why the number of plant species may be greater before the climax community is reached
- more open space
- less competition for light, nutrients etc
- plant species are outcompeted by dominant woodland
Suggest why organisms with more shared taxa have similar base sequences of DNA
- more shared taxa indicates more recent separation of ancestral species
- less time for accumulation of mutations in DNA
Suggest how organisms with similar niches could avoid competition
- alter their own niche to avoid competition
- by eating another prey / plant
Suggest why capture recapture is not suitable for larger mammal population
- dangerous / harm animal
- inaccurate with smaller populations
