populations and ecosystems content

Question 1

population

Answer 1

group of organisms of the same species in the same habitat.

Question 2

habitat

Answer 2

part of ecosystem where certain organisms live

Question 3

community

Answer 3

all populations of all species living in the same area at the same time.

Question 4

ecosystems

Answer 4

can range in size from very small to very large.
community and non living aspects of environment (biotic and abiotic factors)

Question 5

niche

Answer 5

an organisms role within the ecosystem including their position in the food web and habitat.
each species has its own niche governed by adaptations to biotic and abiotic factors.

Question 6

carrying capacity

Answer 6

maximum population size that an ecosystem can support.

Question 7

abiotic factors

Answer 7

non living conditions of an ecosystem

Question 8

biotic factors

Answer 8

impact of interaction between organisms.

Question 9

factors influencing population size

Answer 9

biotic and abiotic factors
inter and intraspecific competition

Question 10

abiotic factors

Answer 10

e.g. light intensity, carbon dioxide and oxygen concentration, temperature, pH, soil conditions.

plants and animals are adapted to the abiotic factors in their ecosystem due to natural selection over many generations.

the less harsh the abiotic conditions e.g. plenty of light and water, the larger the population size and range of species.

Question 11

interspecific competition

Answer 11

competition between different species for resources in short supply e.g. a habitat, food and water.
organisms that are better adapted to their environment are more likely to survive.

Question 12

intraspecific competition

Answer 12

competition between organisms of the same species for resources and a mate.
fitter individuals have more energy to perform impressive courtship ritual
fur or feathers to attract mate.

competition for a mate is due to courtship rituals being similar/ the same

Question 13

predator prey relationship

Answer 13

graph shows relationship between predators and prey in a food web.

regardless of species- same pattern-

decrease in prey population first, lag time and then decrease in predator population
there is always more prey than predators
size of predator and prey population fluctuate.

Question 14

what is succession?

Answer 14

changes in ecological community over time

Question 15

seral stage
final seral stage

Answer 15

eaech stage is called a seral stage.
the final seral stage is the climax community.

Question 16

primary succession

Answer 16

pioneer species colonises bare rock/sand
e.g. lichen are adapted to survive in harsh abiotic conditions and when they die and decompose, there is a thin layer of soil, hummus added.
this makes the abiotic factors less harsh, enabling moss and other small plants to colonise- further increases depth and nutrient content of the soil.
the pattern repeats and the environmental conditions continue to change.
smaller plants colonise.
-organisms make changes to abiotic environment- less harsh and greater biodiversity.

final seral stage- climax community- dominated by trees.

Question 17

secondary succession

Answer 17

succession is disrupted and plants are destroyed

succession starts again but as soil is already created, it does not start from bare rock seral stage.

Question 18

conservation of habitats

Answer 18

destruction of habitat, especially due to human activity
species do not have enough food or resources- may become extinct
to conserve habitats, succession is often managed.

Question 19

conservation of habitats

Answer 19

habitats are being destroyed, especially due to human activity so management of succession is needed to conserve habitats.
by maintaing each seral stage and preventing the climax community- this conserves a wide range of habitats and hence wide range of species

conflict between balancing human needs and conservation for sustainable use of resources e.g. coppicing from forests for furtniture/timber for fuel, while still allowing the tree to survive.

Question 20

how can we ensure that the sample is representative?

Answer 20

large sample
random sampling e.g. using random number generator to generate coordinates

Question 21

what is a transect line used for?

Answer 21

to look at change over an area

Question 22

what are the advantages of sampling?

Answer 22

time efficient
if conducted correctly, more efficient.

Question 23

what type of sampling should be used?

Answer 23

for slow/non moving organisms- quadrat
moving organisms- mark, release, recapture method.

Question 24

unequal distribution
equal distribution

Answer 24

unequal distribution- transect line
equal distribution- random sampling

Question 25

how to measure frequency for equal distribution

Answer 25

-use a grid sytem
-use random number generator to generate coordinates
-place quadrats at coordinates and measure frequency
-multiply by e.g. area of field
-large sample/repeat and calculate average.

Question 26

types of transects

Answer 26

belt transect- quadrats placed at every position along tape measure
interuppted belt transect- quadrats placed at regular intervalas along tape measure.

Question 27

methods to estimate abundance of species.

Answer 27

local frequency- % of squares in quadrat where species is present

density- number of species in a given area
-percentage cover- % of ground surface occupied by species.

Question 28

things that need to be considered when marking organisms during mark, release, recapture method

Answer 28

-not toxic
-must not increase predation chances
-must not reduce reproduction chances.

Question 29

why may the estimate not be accurate?

Answer 29

the esimate of population size may not be accurate in mark, release, recapture as it makes the following assumptions:
-population size is constant (no birth, death or migration)
-animals redistribute evenly.