Mr P bio 1 Populations in Ecosystems Flashcards
what is a population?
all the individuals of a given species living together in the same area at the same time
what is a community?
a community is all the individuals of all the species living together in the same area at the same time
what is a habitat?
the place where an organism lives within an ecosystem
what is a niche?
the role of an organism within its community including its biotic interactions (like what it eats) and its abiotic interactions (like temp range an organism can live in)
what is an abiotic factor?
a non-living factor which affects the distribution of an organism
what is a biotic factor?
a living factor which affects the distribution of an organism
what affect does temperature have on an organism if it is too cold?
the enzymes will not have enough kinetic energy to catalyse reactions quickly enough. The organism’s overall activity will drop and may not be sufficient for survival.
what affect does temperature have on an organism if it is too hot?
the enzymes may start to denature and the overall activity will decrease, again reducing ability to survive. n particularly hot environments, the organism may also experience problems with excess water loss and dehydration.
how can temperature be measured?
using a thermometer or data logger with temperature probe
how does light intensity affect a population?
Light is needed for photosynthesis, therefore the more light available, the greater the rate of photosynthesis. As plants photosynthesise more, the more energy that they will have for seed / spore production and the more the population will grow.
how can light be measured?
light meter
what affect will humidity have on an organism?
The lower the humidity of the environment, the more this water loss will occur. Again, different species have different tolerances to this water loss.
how does the pH of the environment affect an organism?
The pH of the environment can affect extracellular enzymes and surface proteins. The more extreme the pH, the more an organism will be affected and the lower the population size and range of species present.
pH may also affect the availability of mineral salts in the soil and therefore can affect growth of plants.
what are biotic factors?
These are factors affecting the distribution and size of populations which are related to presence of other organisms.
what are the two different types of competition?
interspecific and intraspecific
what is intra and inter specific comp?
intra= between members of the same species
inter= between members of different species
what happens if two species occupy the same niche?
, one species tends to out-compete the other. Eventually, the niche will be occupied by only the one species (this is known as the competitive exclusion principle).
how are the populations of predators and prey linked?
The populations of predator and prey are linked. As the prey population increases, there is more food for the predators and intra-specific competition is reduced. The population of the predator increases.
More and more of the prey are consumed, so the prey population falls. Intra-specific competition now increases in the predator population as there is less food available. The predator population starts to reduce again. The prey population starts to recover and the cycle repeats.
what is the estimate for the population size of a species called?
the abundance of the species
what 3 methods ensure estimating an abundance is accurate and reliable?
- to ensure no bias, selection must be random
2.large sample size= representative and suitable for statistical analysis (reliability is improved by repeats)
3.method of collection = appropriate to the species
how can you check that you have enough samples during an investigation?
calculate a running mean and if it shows little change then it is representative
what organisms can quadrats be used to sample?
slow moving or immobile organisms
what 3 ways can the abundance of a species be measured within a quadrat?
1.population density (count of species)
2.percentage cover
3.frequency (proportion of quadrats that contain a particular species)
what is the method of estimating abundance using a quadrat?
1) Two measuring tapes are arranged at right angles to each other to form the axes of a grid.
2) Obtain a series of coordinates by using random numbers generated using a random number generator such as on a calculator. A quadrat is placed at the intersection of these coordinates.
3) Take a large sample by repeating many time or until the running mean stabilises around the same number.
Then, abundance can then be estimated using a quadrat by:
measuring population density, frequency or percentage cover