Chapter 23- Ecosystems

Question 1

definition of population

Answer 1

group of organisms of the same species living in the same habitat at the same time

Question 2

definition of habitat

Answer 2

part of an ecosystem in which particular organisms live

Question 3

definition of community

Answer 3

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

Question 4

Ecosystem definition

Answer 4

The community of organisms (biotic) and non living (abiotic) components of an area and their interactions.
ecosystems can range in size from very small to very large.

Question 5

niche definition

Answer 5

an organisms role within an ecosystem, including their position in the food web and habitat. each species occupies their own niche governed by adaptation to both abiotic and biotic conditions.

Question 6

carrying capacity

Answer 6

the maximum population size that an ecosystem can maintain sustainably.

Question 7

abiotic factors definition

Answer 7

the non living aspects of an ecosystem

Question 8

list examples of abiotic factors

Answer 8

light
temperature
water availability
oxygen content
soil ph

Question 9

biotic factors definition

Answer 9

living components of an ecosystem

Question 10

biotic factors examples

Answer 10

food availability
breeding partners
pathogens
predators

Question 11

list examples of three varying sizes of ecosystem

Answer 11

rock pool-small
large tree- bigger than rock pool
playing field- bigger than large tree

Question 12

biomass definition

Answer 12

the total mass of organic material, measured in a specific area over a set time period. this can be calculated as dry mass.

Question 13

biomass is transferred through an ecosystem.
what are the producers in a food web and how do they produce their own food

Answer 13

plants are the producers in a food web and they are able to produce their own carbohydrates from carbon dioxide in the atmosphere or in the water (co2 dissolved in water)

Question 14

explain what happens to energy between trophic levels in the food web

Answer 14

-majority of energy is lost through respiration and excretion between each trophic level in the food web.
the remaining energy is used to form biomass.

Question 15

how can biomass be measured

Answer 15

measured as mass of carbon or as dry mass of tissue per given area.
how productive an ecosystem is depends on abiotic and biotic factors. plenty of water, light, warmth and green plants will maximise the rate of photosynthesis and therefore results in more carbohydrates being produced by plants

Question 16

efficiency of biomass formula

Answer 16

efficiency- biomass transferred/ biomass intake x 100

Question 17

how can humans manipulate the transfer of biomass through ecosystems by reducing energy lost at each trophic level.

Answer 17

1) restricting movement (therefore respiration) of animals
2)providing animals with high energy food, (increasing energy input)
3)keeping animals indoors reduces energy transferred as heat.
4) Removing competition and predators (growing indoors and providing animals and plants with all they need)

Question 18

why is the nitrogen cycle important

Answer 18

-air is 78% nitrogen however plants and animals cannot obtain nitrogen through gaseous exchange because nitrogen has a triple bond between nitrogen atoms N—N.
microorganisms are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb.

Question 19

which biological molecules contain nitrogen

Answer 19

proteins
ATP
nucleic acid

Question 20

list the four stages of the nitrogen cycle

Answer 20

1) Nitrogen fixation
2) Ammonification
3) Nitrification
4) Denitrification

Question 21

Outline process of nitrogen fixation and state the names of the nitrogen fixing bacteria

Answer 21

nitrogen (from atmosphere N2) + 3h2——–> 2NH3 (ammonia)
nitrogenases from nitrogen fixing bacteria (rhizobium and azotobacter) found in legume root nodules)

Question 22

Outline process of Ammonification and state the microorganisms needed

Answer 22

NO3/NO2- ————> NH4+ (NH3)
decomposers- aerobic and anaerobic bacteria and fungi
saprobiotic nutrition- bacteria and fungi (microbes) release enzymes that break down larger products into smaller absorb-able nutrients.

Question 23

Outline the process of nitrification and state the names of nitrifying bacteria

Answer 23

NH4+———–> NO2- ———–> NO3- (oxidation reactions)
from ammonia to nitrites- nitrosamonas
from nitrites to nitrate ions- nitrobacter
nitrates are then actively absorbed into soil, plant will use those nitrates to make atp, proteins and DNA

Question 24

Outline process of Denitrification and state the name of the bacteria needed

Answer 24

NO3- ——-> N2
nitrogen enters the atmosphere and used for nitrogen fixation
denitrifying bacteria- pseudomonas
requires anaerobic condition, occurs in waterlogged soil.

Question 25

Describe the carbon cycle

Answer 25

Plants photosynthesise, to fix carbon from the atmosphere (carbon dioxide) into carbohydrates which can be ingested by animals.
All organisms respire and this converts the carbon in carbohydrates back into carbon dioxide in the atmosphere or oceans. When organisms die or excrete, the carbon is broken down to carbon dioxide by decomposers that respire using the carbohydrates within dead or waste matter.
An imbalance in this cycle leads to ocean acidification and global warming . imbalance is caused by deforestation and burning too many fossil fuels this means less co2 being used in photosynthesis and more being produced by combustion of fossil fuels.

Question 26

what can an imbalance in the carbon cycle lead to

Answer 26

-too much co2 could lead to ocean acidification and global warming

Question 27

what is an imbalance in the carbon cycle caused by

Answer 27

• deforestation and burning of too many fossil fuels
  deforestation- less co2 being used in photosynthesis
  burning too many fossil fuels- more co2 being produced by combustion of fossil fuels.

Question 28

Definition of succession

Answer 28

change in an ecological community over time

Question 29

definition of pioneer species

Answer 29

first species to colonise a new area, examples are lichen which are adapted to harsh abiotic conditions

Question 30

Describe process of primary succession

Answer 30

starts with pioneer species colonising bare rock or sand.
the pioneer species are adapted to survive harsh abiotic factors and with their death and decomposition, they change the abiotic conditions to become less harsh and form a thin layer of soil called humus.
mosses and smaller plants can now survive, they further increase the depth and nutrient content of the soil. this pattern continues and as the abiotic factors become lass harsh and so larger plants can survive and change environment further.
each new species changes the environment in a way that makes it less suitable for existing species, newer species outcompete the pioneer species
increased biodiversity and a more stable environment as abiotic factors less harsh.

Question 31

how does succession change biodiversity

Answer 31

increases biodiversity and so more a stable environment formed
species richness and number of organisms increases.

Question 32

what is the final stage of succession known as

Answer 32

the climax community- this is dominated by trees

Question 33

what is secondary succession

Answer 33

succession is disrupted and plants and animals may be destroyed
succession starts again but soil is already formed, succession does not start at bare rock seral stage

Question 34

as succession occurs larger animals and plants can…

Answer 34

colonise the area

Question 35

what is deflected succession, give examples

Answer 35

deflected succession is when human activities can disrupt the progress of succession
a climax community cannot be reached if animals are grazing or grass is being trampled on by humans
controlled burning or removal of vegetation can also prevent a climax community from being formed.

Question 36

what human activities can prevent a climax community from forming

Answer 36

-vegetation removed
-trampling on grass by humans
-animals grazing
-controlled burning

Question 37

why would we want deflected succession to occur

Answer 37

by maintaining earlier stages of succession and preventing a climax community, a greater variety of habitats can be conserved and therefore a greater range of species can survive.

Question 38

there can be conflict between human needs and conservation in order to maintain the sustainability of natural resources.
what is an example of a compromise made in order to manage this conflict

Answer 38

forests can be coppiced to provide timber for fuel and furniture while still allowing the tree to survive.

Question 39

why might an ecologist want to measure the size of a population

Answer 39

to measure the impact of changing environments and to protect plants and animals.

Question 40

what are a few common aspects of taking population sizes

Answer 40

for the sampling to provide an accurate estimate that is representative of the population size. many samples 30+ need to be taken and sampling should be random to avoid bias.