B10: Ecosystems

Question 1

define population

Answer 1

group of organisms of one species,

living and interacting in the same area at the same time.

Question 2

define community

Answer 2

all of the populations of different species interacting with each other in an ecosystem.

Question 3

define habitat

Answer 3

place where organisms live.

Question 4

define ecosystem

Answer 4

unit containing the community of organisms and their environment,
interacting together.

Question 5

living factors=

Answer 5

biotic

Question 6

non living factors=

Answer 6

abiotic

Question 7

abiotic factor example

Answer 7

availability of oxygen
availability of water
light intensity
pH (of water or soil)
pollution
temperature
mineral ions.

Question 8

biotic factor examples

Answer 8

competition
disease
food supply
predation.

Question 9

intraspecific competition

Answer 9

between organisms of the same species
for resources such as food, territory, a mate or a nesting site.
These factors would have a negative effect on population size if they were in short supply.

Question 10

interspecific competition

Answer 10

between organisms of different species
for resources such as food.
In this case, one species is often successful in forcing the other species out of the community.

Question 11

sufficient food for the population=

Answer 11

organisms will be more likely to thrive,
survive to breeding age and
then breed successfully to produce more offspring. The size of the population will grow.

Question 12

insuffiient food for population=

Answer 12

increase in deaths or
an increase in migration (emigration)
to find new sources of food.
The size of the population will be reduced.

Question 13

Factors that cause the size of the population to change includ

Answer 13

food supply
predation
disease.
human interactions:
pollution
climate change.
war

Question 14

lag phase of population growth

Answer 14

population is very small
and takes time to acclimatise new environment, become mature and start reproducing.
A doubling of small numbers does not have a big impact on the total population size,
so the line of the graph only rises slowly with time.

Question 15

log phase (exponential stage) of population growth

Answer 15

there are no limiting factors.
Rapid breeding occurs in the population,
resulting in significant increases in numbers.
There are far more births than deaths.

Question 16

stationary phase in population growth

Answer 16

Limiting factors such as shortage of food or a build-up of toxic materials in the environment start to have an effect,
slowing down population growth.
number of deaths equals the number of births,
so the line of the graph flattens to form a plateau.

Question 17

death phase in population growth

Answer 17

The number of deaths (mortality rate) becomes greater than the number of births
so the population numbers start to decrease.
may be due to lack of food, an accumulation of waste materials, disease spreading through the population, or an influx of predators.

Question 18

mutalism

Answer 18

close relationship between two organisms of
different species
where both organisms benefit.

Question 19

parasitism

Answer 19

only one of the two organisms involved gains any benefit.

The other is harmed.

Question 20

At each successive stage in a food chain, the amount of biomass…

Answer 20

decreases

Question 21

At each successive stage in a food chain, the amount of biomass… why?

Answer 21

the organisms use some of food obtained
for energy to move, respire and maintain their body temperature.
some of the material is not digested or even eaten

Question 22

largest bar at the base of pyramid

Answer 22

producer

Question 23

food chains have….

Answer 23

trophic levels

Question 24

The key processes in carbon cycle

Answer 24

photosynthesis, respiration, combustion and decomposition

Question 25

how do photosynthesis and respiration ….

Answer 25

balance each other,

maintaining the concentration of carbon dioxide in the atmosphere

Question 26

how is the balance disrupted

Answer 26

mass deforestation
by releasing carbon dioxide into the atmosphere by other processes such as combustion of fossil fuels,
the level of carbon dioxide in the atmosphere will increase.
can cause environmental problems such as global warming.

Question 27

When organisms die….

Answer 27

they provide food for detritus feeders

Question 28

detritus feeders

Answer 28

decompose (break down) 
the organic molecules 
in the dead plants and animals
 through the process of respiration
 to release energy. 
Again, carbon dioxide is released into the atmosphere.

Question 29

Some animals form…

Answer 29

shells or exoskeletons
from calcium carbonate, using carbon dioxide.
These can also become fossilised,
trapping the carbon in them.

Question 30

equation for complete combustion of carbon

Answer 30

C + O2 → CO2

Question 31

detrimental effects of deforestation

Answer 31

fewer trees photosynthesising,
so less carbon dioxide is removed from the air.
when the trees are cut down, the small branches and foliage are burned,
adding more carbon dioxide back into the air.

Question 32

which process doesnt release heat energy

Answer 32

photosynthesis

Question 33

Transpiration

Answer 33

plants release water vapour into the atmosphere, throughstomata in the leaves.
water evaporates inside the leaf before it is released.

Question 34

Evaporation

Answer 34

occurs from the surface of bodies of water

such as rivers, lakes and the sea.

Question 35

Condensation

Answer 35

the water vapour in the atmosphere condenses to form clouds.

Question 36

Precipitation

Answer 36

water in the clouds forms rain, snow, etc.
which falls to the land
and drains into water systems.

Question 37

Osmosis

Answer 37

process used by plant roots, bacteria and other organisms to take up water.

Question 38

Excretion

Answer 38

from animals.
Water is lost from animals in the form of
sweat, exhaled air and urine.
Faeces (a product of egestion not excretion) also contains some water.