Mr P bio 1 Populations in Ecosystems

Question 1

what is a population?

Answer 1

all the individuals of a given species living together in the same area at the same time

Question 2

what is a community?

Answer 2

a community is all the individuals of all the species living together in the same area at the same time

Question 3

what is a habitat?

Answer 3

the place where an organism lives within an ecosystem

Question 4

what is a niche?

Answer 4

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)

Question 5

what is an abiotic factor?

Answer 5

a non-living factor which affects the distribution of an organism

Question 6

what is a biotic factor?

Answer 6

a living factor which affects the distribution of an organism

Question 7

what affect does temperature have on an organism if it is too cold?

Answer 7

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.

Question 8

what affect does temperature have on an organism if it is too hot?

Answer 8

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.

Question 9

how can temperature be measured?

Answer 9

using a thermometer or data logger with temperature probe

Question 10

how does light intensity affect a population?

Answer 10

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.

Question 11

how can light be measured?

Answer 11

light meter

Question 12

what affect will humidity have on an organism?

Answer 12

The lower the humidity of the environment, the more this water loss will occur. Again, different species have different tolerances to this water loss.

Question 13

how does the pH of the environment affect an organism?

Answer 13

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.

Question 14

what are biotic factors?

Answer 14

These are factors affecting the distribution and size of populations which are related to presence of other organisms.

Question 15

what are the two different types of competition?

Answer 15

interspecific and intraspecific

Question 16

what is intra and inter specific comp?

Answer 16

intra= between members of the same species
inter= between members of different species

Question 17

what happens if two species occupy the same niche?

Answer 17

, 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).

Question 18

how are the populations of predators and prey linked?

Answer 18

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.

Question 19

what is the estimate for the population size of a species called?

Answer 19

the abundance of the species

Question 20

what 3 methods ensure estimating an abundance is accurate and reliable?

Answer 20

1. 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

Question 21

how can you check that you have enough samples during an investigation?

Answer 21

calculate a running mean and if it shows little change then it is representative

Question 22

what organisms can quadrats be used to sample?

Answer 22

slow moving or immobile organisms

Question 23

what 3 ways can the abundance of a species be measured within a quadrat?

Answer 23

1.population density (count of species)
2.percentage cover
3.frequency (proportion of quadrats that contain a particular species)

Question 24

what is the method of estimating abundance using a quadrat?

Answer 24

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

Question 25

how do you calculate population density?

Answer 25

count total no. of individuals in quadrat area, add up total and divide by no. or quadrats to get mean, multiply mean by no. of quadrats that could fit in total area sampled

Question 26

what does systemic sampling allow us to investigate?

Answer 26

They allow us to investigate how the species abundance varies across an area,

Question 27

what is a transect?

Answer 27

A transect is a line across the area and sampling is performed at set predetermined intervals along the line e.g. every 5 metres.

Question 28

what are the 3 ways of sampling systematically?

Answer 28

1.recording what species touching line at each sampling point
2. two parallel lines a metre apart and recording what species between them (belt transect)
3.interrupted belt transect- one line + quadrat at equally spaced intervals, recording abundance of species in each

Question 29

what is the method of mark, release and recapture?

Answer 29

1. Animals of a particular species are collected (usually by a netting or trap technique) and counted.
2. The animals are then marked in some way (paint dots, tagged, etc.). This must not harm them or affect their survival.
3. The animals are then released and left to redistribute into the population.
4. A second capture is carried out and the total number caught is recorded, as well as how many of those captured are marked.
5. population size = no. caught 1st time x no. caught 2nd time all divided by no. caught 2nd time which were marked

Question 30

what are 4 assumptions that are made with the mark, release and recapture method?

Answer 30

1. The population size does not change between the two capture times
2. The marking should not make the marked animals more susceptible to predators or harm the animals.
3. The marking should not rub off or be lost.
4. sufficient time should be left for the released, marked individuals to fully disperse equally through the rest of the population