3.7.4 populations in ecosystems

Question 1

define population

Answer 1

a group of organisms of the same species occupying a particular space at a particular time ( they can potentially interbreed)

Question 2

define community

Answer 2

all the populations of all the different species living in one habitat at the same time

Question 3

define ecosystem

Answer 3

a community and the non- living component of its environment

Question 4

define abiotic factor

Answer 4

non-living features of an ecosystem, such as the temperature and PH of the soil

Question 5

define biotic factor

Answer 5

living features of an ecosystem

Question 6

define habitat

Answer 6

place where an organism lives

Question 7

define interspecific competition

Answer 7

competition between different organisms

Question 8

define intraspecific competition

Answer 8

competition between the same species

Question 9

define carrying capacity

Answer 9

an ecosystem supports a certain size of population of a species

Question 10

define niche

Answer 10

an organisms role within an ecosystem, including their position in the food web and habitat

Question 11

give examples of abiotic factors

Answer 11

temperature
oxygen
carbon dioxide concentration
light intensity
PH

Question 12

what is the effect an abiotic factor has on a population

Answer 12

plants and animals become adapted to their ecosystem
these adaptations are developed through natural selection
the less harsh the abiotic factor the larger the population size

Question 13

explain what interspecific competition is

Answer 13

members of different species are in competition for the same resource that could be in limited supply
better adapted individual is more likely to succeed

Question 14

explain what intraspecific competition is

Answer 14

when members of the same species are in competition for resources AND a mate

Question 15

briefly outline the predator- prey relationship

Answer 15

size of the predator and prey both fluctuate
there will always be more prey than predator
the size of the population will always change in the prey and then the predators (lag time)

Question 16

in terms of niches, what is a specialist?

Answer 16

species with narrow niches

Question 17

in terms of niches, what is a generalist?

Answer 17

species with broad niches

Question 18

define adaptation

Answer 18

a feature an organism possesses that increases its chance of survival

Question 19

what is the competitive exclusion principle?

Answer 19

two species cannot co-exist in the same habitat if they have the same niche

Question 20

how does light intensity affect populations?

Answer 20

light intensity increases, the rate of photosynthesis increases
faster rate of photosynthesis means more plant growth
more spores and more seeds produced
extra longer photoperiod the more sunlight plants absorb
this means stomata stay open for longer and there is an increased transpiration rate

Question 21

how does temperature affect populations?

Answer 21

cold blooded animals
- decreased temp
- less kinetic energy
- less E/S complexes formed
- reduced metabolic rate
an increased temperature means denatured enzyme

Question 22

how does PH affect populations?

Answer 22

small change: alters charges on R groups of amino acids at active site so fewer E/S complexes formed due to induced fit

large change: h and ionic bonds break which changes the tertiary structure of the enzyme, this changes the shape of the active site meaning it is no longer complementary

Question 23

how does salinity affect populations?

Answer 23

increased salinity = decreased water potential = increase in osmosis
H2O moves out down a water potential gradient
plasmolysis = death

Question 24

how does water and humidity affect populations?

Answer 24

increase in humidity means a decrease in evaporation
animals: decrease in sweating and a decrease in cooling
plants: decrease in transpiration

Question 25

how does the concentration of mineral ions affect populations?

Answer 25

fe ions : haemoglobin = o2 transport = aerobic respiration = increased ATP synthesis nitrate ions : plants uptake amino acids + nucleotides e.g; ATP, DNA and RNA

Question 26

define predation

Answer 26

where an organism eats another organism

Question 27

suggest why ecologists may want to sample a species

Answer 27

- to find out what conditions a species needs for survival - determine the effects of different treatments - see how a range of species varies over time season

Question 28

why is it not possible to count every species in a particular location?

Answer 28

too time consuming

Question 29

what is a quadrat?

Answer 29

it is a sample area in a habitat marked off so organisms within it can be studied

Question 30

what is systematic sampling?

Answer 30

sampling the area in a regular pattern e.g.; at every 3rd metre square

Question 31

what is random sampling?

Answer 31

using a random number generator to assign coordinates to each square

Question 32

why is it so important that the quadrats are placed randomly?

Answer 32

- avoids bias - more representative data allowing for a valid conclusion

Question 33

why is it important that a large sample is taken?

Answer 33

representative of the population and therefore allows for a ore accurate mean or line of best fit and provides enough data for a statistical test

Question 34

explain how you would use random sampling with quadrats to estimate population sizes

Answer 34

1. grid the area 2. assign coordinates to the grid 3. randomly select two coordinates 4. place 1m^2 quadrat down at coordinates and then count the number of organisms/ measure percentage cover 5. repeat many times and find a mean average 6. calculate the area of the field 7. multiply the area of the field by the mean number of organisms in 1m^2

Question 35

what are transects?

Answer 35

a line through a habitat along which species can be sampled

Question 36

what are the three types of transect?

Answer 36

line belt interrupted

Question 37

what is a line transect?

Answer 37

a tape measure is placed along the transect and the species that touch the line are recorded

Question 38

what is a belt transect?

Answer 38

quadrats are placed next to each other along the transect to work out species frequency and percentage cover along the transect

Question 39

what are interrupted transects?

Answer 39

instead of investigating the whole transect of either line or belt you can take measurements at intervals

Question 40

explain how you would use systematic sampling along a transect to estimate population size

Answer 40

1. lay out a tape measure/ rope across the area of land to sample. The start of the transect should be placed at random 2. place quadrats at regular intervals and count the number of organisms/ measure percentage cover 3. repeat with many transects

Question 41

what is mark release recapture?

Answer 41

how you measure an abundance of mobile organisms

Question 42

what is a limitation of both quadrats and transects?

Answer 42

they can only record species that remain sessile (stationary)

Question 43

explain how you would use mark release recapture to estimate the population size of mobile organisms

Answer 43

1. capture a sample of a species using a trap 2. count the sample 3. mark the sample in non-harmful discrete way 4. release them back into their habitat 5. wait for a fixed period and collect a second sample 6. count them and count the number that were marked from the first sample

Question 44

what is the formula for calculating estimated population size?

Answer 44

estimated population size = total no. in sample 1 x total no. in sample 2 / number of marked animals in sample 2

Question 45

mark release recapture relies on assumptions, what does it assume?

Answer 45

- the marked sample has had enough time and opportunity to mix back in with the population - the marking has not affected the individuals chance of survival and the marking itself remains visible - there is no significant changes in population size due to birth

Question 46

what is the equation for chi squared test?

Answer 46

x2 = sum of ( O - E) ^2 / E O= observed frequency E = expected frequency

Question 47

what is succession?

Answer 47

how an ecosystem changes over a period of time

Question 48

why is bare rock such a hostile environment?

Answer 48

no soil extreme temperatures lack of water — dehydration

Question 49

what is the name of the first species to colonise a new area?

Answer 49

pioneer species

Question 50

what happens when a new species colonises?

Answer 50

abiotic factors are changed, they become more favourable more successful competitors outcompete previous species previous species is decomposed forms humus and more soil more soil means more nitrates and water retained

Question 51

at the end of succession what is formed?

Answer 51

climax community

Question 52

what are the three features of a climax community?

Answer 52

stable (food webs etc) abiotic factors mostly constant population size are stable

Question 53

what is secondary succession?

Answer 53

happens on land that’s been cleared of all plants

Question 54

what are the differences between primary succession and secondary succession?

Answer 54

primary : starts with bare rock can take thousands of years to reach climax community there’s no soil pioneer species needed secondary : starts with soil no pioneer species needed takes just tens of years to reach climax community

Question 55

what is conservation?

Answer 55

the protection and management of species and habitats in a sustainable way

Question 56

what does sustainability mean?

Answer 56

means that enough resources are taken to meet the needs of people today without reducing the ability of people in the future to meet their own needs

Question 57

what are the main reasons for conservation?

Answer 57

ethical economic culture and aesthetic

Question 58

what are some examples of conservation methods?

Answer 58

management of succession seed banks captive breeding fishing quotas protected areas

Question 59

what is the name of the community by which succession is stopped artificially?

Answer 59

plagioclimax

Question 61

**exam question** in chaffinches, the date of laying the first egg is determined by a number of factors. These include day length and temperature. What is the advantage to the bird of egg laying bejng determined by day length

Answer 61

birds do not start laying eggs when period of warm weather occurs early in the year