19 populations in ecosystems

Question 1

what is ecology?

Answer 1

the study of inter-relationships between organisms and their environment

Question 2

what are biotic factors?

Answer 2

living factors of an ecosystem

Question 3

what is an ecosystem?

Answer 3

all the living and non living components of a particular area

Question 4

what is a population?

Answer 4

organisms of the same species living in the same habitat

Question 5

what is a community?

Answer 5

all the populations of different species in the same area at the same time

Question 6

what is a habitat?

Answer 6

part of an ecosystem in which particular organisms live

Question 7

what is a niche?

Answer 7

an organisms role within an ecosystem. their position on the food web and their habitat.
(each species occupies their own niche)

Question 8

what is population size?

Answer 8

the number of individuals in a population

Question 9

4 abiotic (nonliving) factors that influence the size of a population

Answer 9

• temperature
• light
• pH
• water and humidity

Question 10

what is interspecific competition?

Answer 10

competition between organisms of different species for resources such as food, water, light etc

Question 11

what is intraspecific variation?

Answer 11

competition between organisms of the same species for resources such as food, water, breeding sites etc.

Question 12

what is carrying capacity?

Answer 12

the size of population that an ecosystem can support

Question 13

what does population size vary as a result of?

Answer 13

• the effect of abiotic factors

- interactions between organisms: interspecific and intraspecific competition and predation

Question 14

what is predation?

Answer 14

when one organism is consumed by another

Question 15

what is the predator-prey relationship and what is its effect on population size?

Answer 15

1) predators eat there prey, thereby reducing population of prey
2) less prey available so more competition between predators
3) predator population decrease as some individuals unable to survive or reproduce
4) less predators so more prey survive and reproduce
5) prey population increases
6) more prey available so predators population increases

Question 16

why is the predator-prey relationship often less severe?

Answer 16

organisms eat a range of foods so not dependent on only one population

Question 17

what are the two types of quadrats?

Answer 17

point quadrat: horizontal bar through which a long pin is dropped, each species the pin touches is recorded

frame quadrat: frame divided into equally sized subdivisions, abundance of each species within the quadrat is recorded

Question 18

3 factors to consider when using quadrats?

Answer 18

• size of quadrat used
• number of sample quadrats to record within the study area
• position of each quadrat within the study area

Question 19

why is random sampling important?

Answer 19

to avoid bias so data is reliable

Question 20

when should systematic sampling be used?

Answer 20

where some form of gradual change takes place, e.g the distribution of organisms along a line of succession (sand dunes)

Question 21

what is abundance?

Answer 21

the number of individuals of a species within a given area

Question 22

how to measure abundance in motile organisms?

Answer 22

mark-release-recapture - a known number of animals are caught, makes and release back into the community. later, a given number of individuals are collected randomly and number of marked individuals is recorded

Question 23

equation for estimated population size

Answer 23

individuals in first sample x individuals in second sample / marked individuals recaptured

Question 24

4 assumptions made when using mark-release-recapture technique

Answer 24

• proportion of marked to unmarked in second sample is the same as the whole population
• no immigration or emigration
• few deaths and births
• method of marking is not toxic to the individual

Question 25

what is succession?

Answer 25

changes over time in the species that occupy a particular area

Question 26

3 features of pioneer species that suit them to colonisation

Answer 26

• asexual reproduction so can rapidly multiply
• tolerance to extreme conditions
• ability to photosynthesise

Question 27

summary of ecological succession on land

Answer 27

barren land - pioneer species - secondary colonisers - tertiary colonisers - climax community

Question 28

what is the pioneer species?

Answer 28

a species that can colonise bare rock or ground (e.g lichen)

Question 29

what is the climax community?

Answer 29

the organisms that make up the final stage of ecological succession (e.g woodland)

Question 30

4 main reasons for conservation

Answer 30

PEEC
personal - maintain planet
ethical - respect for living things
economic - long-term productivity is greater if ecosystems are maintained in their natural state
cultural and aesthetic - habitats. and organisms enrich our lives and add interest

Question 31

what are abiotic factors?

Answer 31

non-living conditions of an ecosystem

Question 32

examples of biotic factors

Answer 32

competition and predation

Question 33

what is a species?

Answer 33

a group of similar organisms that can breed together to produce fertile offspring