7.4 Sampling and ecosystems

Question 1

what is an ecosystem

Answer 1

dynamic system consisting of a community and all the nonliving factors of its environment

Question 2

what is a population

Answer 2

groups of individuals of one species occupying the same habitat at the same time, which can interbreed to produce fertile offspring

Question 3

what is a community

Answer 3

all the populations of a different species occupying the same habitat at the same time

Question 4

what is a habitat

Answer 4

place where organisms live, characterised by the physical conditions and other species present

Question 5

what is a niche

Answer 5

describes how an organism fits into the environment. includes all the abiotic and biotic conditions to which an organism is adapted

Question 6

what is carrying capacity

Answer 6

the maximum population size a habitat can support over an extended period of time

Question 7

what determines a population’s carrying capacity

Answer 7

abiotic factors: temp, ligh, water etc.
biotic factors: intraspecific competition, interspecific competition, predation

Question 8

how can you avoid sampling bias

Answer 8

• random sampling
• systematic sampling

Question 9

how to estimate population size of not-motile organisms

Answer 9

• place quadrat and count individuals or estimate % cover
• Take a large number of repeats and calculate means
• Quadrat size dependent on size of organism and distribution (rare or unevenly distributed individuals - larger quadrat will give a more representative estimation)
• Multiply average population per m2 by area of habitat to estimate total population (or compare population densities - per m2

Question 10

how to estimate population size for motile organisms (MMR)

Answer 10

• Collect individuals in a fixed area for a fixed period of time & count
• Mark (non-toxic mark / in a way which avoids increased predation) and release into community
• Allow sufficient time to re-mix with population, e.g. 1 day
• Collect individuals in the same area for the same period of time - count total and number marked
• Estimate population using: equation

Question 11

what is the equation used for estimating motile organisms

Answer 11

Question 12

what are the assumptions of MMR

Answer 12

• proportions of marked individuals in sample 2 is representative of whole population
• marked individuals have completely re-mixed into population
• isolated population
• few births and deaths
• mark is not toxic or increase predation

Question 13

what is a succession

Answer 13

changes, over time, of the species which occupy a particular area

Question 14

what is a primary succession

Answer 14

from purely inorganic starting point

Question 15

what is a secondary succession

Answer 15

from area cleared of organisms, but with soil present

Question 16

how does conservation work

Answer 16

• Environment colonised by pioneer species
• These pioneer species alter the abiotic factors of the environment
• Environment becomes less hostile, allowing other species to survive
• Change in species over time as environment is modified by each community, resulting in an increase in biodiversity and biomass (due to an increase in number and variety of habitats and niches)
• Climax community reached