Population size and ecosystems (C1) Flashcards
Ecology definition
the study of living organisms within a habitat and their interactions with both biotic and abiotic factors
Ecosystem definition
a characteristic community of interdependent species interacting with the abiotic components of their habitat
Habitat definition
the place in which an organism lives
- often contains a community of organisms
Population definition
a group of interbreeding organisms of the same species occupying a particular habitat
Community definition
interacting populations of two or more species within a particular habitat
i.e populations of different species living within the same habitat
Biotic factors
living factors within the environment including…
- competition for recourses
- predators
- disease/ pathogens
Abiotic factors
non living factors including…
- light intensity
- water/nutrients/o2 availability
- temperature
Niche definition
the specific role and position a species plays within a particular ecosystem
Random sampling
method of sampling when abiotic factors are uniform
Systematic sampling
method of sampling when there is a change is abiotic factors
What are population numbers dependent on?
population numbers will fluctuate, this is dependent on various factors, including…
- birth rates/cell division
- death rates
- immigration
- emigration
Name the shape of the graph of a usual pattern of growth of an equilibrium species
S-shaped
sigmoidal
What are the phases of the population growth curve for an equilibrium species and what happens?
*draw the graph
- LAG - slow rate of reproduction, cellular activity but not growth, a period of intense metabolic activity like enzyme synthesis i.e reaching sexual maturity in animals, time taken for yeast to hydrate in nutrient broth
- LOG/EXPONENTIAL - rapid increase in population, no factors limiting growth
- STATIONARY - birth rate/cell division is equal to death rate, factors are limiting further growth, pop has reached carrying capacity
- DEATH/DECLINE - environmental factors result in death rate greater than birth rate/cell division i.e glucose depleted in nutrient broth or yeast producing toxic waste ethanol
Carrying capacity definition
the maximum number of individuals a population can sustain within a particular environment
(the actual number fluctuates around the carrying capacity in response to environmental changes)
Where is environment resistance and where does it start to occur?
- any factors that may limit the growth of a population
- end of log phase
How do you calculate population changes when populations are plotted on a log scale?
number of bacteria at one specified day number of bacteria at the other day antilog10 those numbers take away from each other divide over the difference of days
i.e antilog10 ? - antilog10 ??
————————————–
day/time difference
What are density dependent factors affecting the size of a population?
- the larger the population size the greater the effect (more likely to slow down pop growth rate)
e.g…..
• disease and parasites
• food availability
• toxic waste build up
(often biotic)
What are density independent factors affecting the size of a population?
- factors have an effect regardless of population size, the effect is ‘independent’ to the population
(more likely to cause a population crash)
e.g…..
• natural disaster i.e volcanic eruption, eq, floods etc..
• sudden changes in temp
• hunting
(often abiotic)
How can competition affect population size, and the types of competition?
- by impacting potential breeding success (comp for mates) and survival of organism (comp for land, food, fight)
- INTRA - specific competition
- INTER - specific competition
Factors affecting population size (3)
- density dependent factors
- desntisy independent factors
- competition
What is INTRA specific competition?
(comp between the same species)
- between members of the SAME species, occupy same niche/specific habitat, compete for same recourses
- driving force behind natural selection ( as n.s is survival of fittest between that single species - pass on beneficial alleles, variation, adaption can occur)
- as pop of that species a greater proportion of individuals fail to survive because comp excels
What is INTER specific competition?
(comp between different species)
- competition for resources between members of different species
- in general one species will out compete the other
What is the definition of niche and its concept?
NICHE - the specific role and position a species plays within a particular ecosystem
• only one species can occupy a particular niche within an ecosystem - one species will always outcompete the other
e.g two different species of protozoan grown in lab flasks - grow well in flasks separately but when grown together one outcompetes the other for nutrients, the population of one grows and the other falls
What is the concept of an ecosystem?
ECOSYSTEM is a characteristic community of interdependent species and their habitat
*ecosystems range in size from very large to very
small
What is the source of energy for an ecosystem?
- the SUN is the source of energy for an ecosystem
- light energy, trapped by photosynthesis is the source of energy for most ecosystems (other than those based on chemosynthesis, e.g. hydrothermal vents)
What are trophic levels? energy between? biomass?
feeding levels within an ecosystem, the level at which an organism falls within the food web
- producers are the first trophic level i.e photosynthesising plants
- then a series of consumers (4/5 levels - only enough energy to support)
- flow is energy is shown between the levels from the initial energy source, the sun to producers and consumers
- energy is lost between trophic levels
- biomass decreases up the levels
What is gross primary productivity (GPP)?
Gross primary productivity (GPP) is the rate of
production of chemical energy in organic chemicals by
photosynthesis (in kJ m-2 year-1).
What is net primary productive (NPP) and its equation?
Net Primary Production is gross primary production minus the chemical energy generated in respiration and used up by the producers metabolism in the year (respiration = R)
(NPP = GPP - R)
*NPP represents the potential food/chemical energy available to heterotrophs in ecosystems.
Why is energy lost from the food chain at each level?
- energy is egested - mostly cellulose as indigestible
- energy lost as heat during respiration (farmers keep animals inside during winter - less energy lost regulating body temp)
- energy remains in inedible parts of the animal - fur, bones, horns
*INEFFICIENCY OF ENERGY TRANSFER BETWEEN TROPHIC LEVELS
Primary productivity vs secondary productivity
- primary productivity involves the producers
- secondary productivity involves the rate at which consumers accumulate energy from assimilated food in biomass in their cells/tissues
Why do carnivores have a more efficient energy conversion than herbivores?
protein is more rapidly and easily digested than cellulose which is lost in much of herbivores faeces
What is gross ecological efficiency? equation?
measure of how much energy is transferred from one trophic level to the next (often around 10% but oceanic food chains higher approx. 40%)
GEE = energy in that trophic level
——————————————– x 100
energy in previous trophic level
