U3 T2 - Ecosystem Dynamics

Question 1

Define Biomass

Answer 1

the total amount (dry weight) of biologicial matter of a group of organisms in a given area

Question 2

Define Autotrophs.

Answer 2

The main producers who use energy (sun) and inorganic molecules to produce organic molecules, which is the main energy source for all ecosystmes and organisms. (photosynthesis)

Question 3

Explain the transfer of energy between Photoautotrophs and heterotrophs

Answer 3

• Solar energy transformed into chemical energy (glucose) by the autotrophs.
• Glucose is then consumed by the heterotrophs and transform it into ATP for use by the cells. (Or consumed and left as biomass)

Question 4

Define Trophic level. Name the four main trophic levels.

Answer 4

An organisms level in the food chain of an ecosystem based on feeding relationships.
1st - autotrophs.
2nd - Primary consumer
3rd - Secondary consumer
4th - Tertiary consumer

Question 5

Describe the loss of energy from the sun to the autotrophs

Answer 5

Energy is lost through radiation, absorption, and reflection.
55% of light energy is refleccted by Earth’s atmosphere
95-99% of light reachin plants is relfected or absorbed by the plants
1-5% of light is used for photosynthesis

Question 6

Describe GPP and NPP

Answer 6

GPP - the rate at which solar energy is used to fix carbon into organic molecules
NPP - subtract the energy used in metabolism from the GPP

Question 7

Describe trophic level energy transfer efficiency

Answer 7

Only about 10% of the previos trophic level energy is transferred into the next levels biomass. Most energy is lost through:
-transformed to heat energy (80%)
-chemical energy of uneaten portion (10%)

Question 8

Describe the water cycle

Answer 8

-Evaporation from oceans and fresh water
-Condensation in clouds
-Precipitation as rain or snow
-Release from organisms through transpiration and respiration
-Run off from land into waterways

Question 9

Describe how carbon enters the ecosystem

Answer 9

-Combustion of fossil fuels
-Respiration of dead animals/plants
-Death and decay of living organisms
-Coming out of solution into water
-Volcanic activity

Question 10

Describe how carbon is taken up in the ecosystem

Answer 10

-Photosynthesis by plants
-Dissovling in water and forming carbonates
-Formation of fossil fuels
-Incorporation as biomass

Question 11

Describe how nitrogen enters the ecosystem (5 ways)

Answer 11

Dentrification
Ammonification
Nitrification
Lightning
Fertilizers

Question 12

Describe dentrification

Answer 12

decomposers break down faeces and dead organisms and return nitrogen to soil as ammonia

Question 13

Descibe Ammonification

Answer 13

bacteria in the soil of legumes fix nitrogen into ammonia

Question 14

Describe Nitrification

Answer 14

bacteria in soil converts ammonia into nitrite/nitrate ions

Question 15

Describe Lightning

Answer 15

making nitrogen and oxyegn react to form nitrogen dioxide which dissolves in the rain to form nitrate ions

Question 16

Describe how nitrogen is taken up in the ecosystem

Answer 16

Plants take up nitrogen through the soil to produce proteins
Animals consume plants and animals and obtain nitrogen compounds

Question 17

Define Ecological Niche

Answer 17

a role or space that an organism fills in an eocsystem, including all its interactions with the biotic and abiotic factors in an environment

Question 18

Describe Ecological Niche in termrs of habitat, feeding relationships and interactions with other species.

Answer 18

Habitat - how the organism uses the available resources in the habitat
Interactions - symbiotic relationships, competition
Feeding Relationships - Predation

Question 19

Describe the competitive exclusion principle.

Answer 19

Two species that require the same resources can live in the same environment together but cannot coexist in the same niche

Question 20

Define keystone species.

Answer 20

a species that plays a critical role in maintaining the structure and functioning of their ecosystem

Question 21

Name exapmles of Keystone species

Answer 21

Sharks, Bees, Wolf

Question 22

Define Carrying Capacity

Answer 22

the size of the population that can be supported indefinitely on the available resources and services of the ecosystem

Question 23

define limiting factor

Answer 23

any factor that limits the size of a population

Question 24

Give examples of both biotic and abiotic limiting factors.

Answer 24

Biotic - presence of predators, competition for resources, disease/parasite
Abiotic - space, natural dissasters, water availability

Question 25

Name the four processes that affects a population’s size

Answer 25

-Natality (birth)
-Mortality (Death)
-Immigration (moving in from another popualtion)
-Emigration (moving out to another population)

Question 26

What is the formula for population grwoth rate

Answer 26

PGR = (birth rate + immigration rate) - (death rate + emigration rate)

Question 27

Recall the Lincoln index formula

Answer 27

N = (Mn)/m

N=size of target population
M=no. caught, tagged and released in first sample
n=no. caught in second sample
m=no. tagged previously in second sample

Question 28

Name the two patterns of poulation growth

Answer 28

-Exponential
-Logistic (flattens out)

Question 29

Define Ecological Succession

Answer 29

the sequences of change in an ecosystem, where one kind of community is replaced by another moe complex one

Question 30

Describe seres, pioneer, and climax communities.

Answer 30

Sere - the successive community to the one before
Pioneer communities - the first/orginal sere
Climax Community - the final stable community which has no seres after it

Question 31

Describe Features of Pioneer Species.

Answer 31

-Ability to perform nitrogen fixation
-Ability to photosythesise efficiently
-Rapid seed or spore germination

Question 32

Describe the differences between Primary and Secondary succession.

Answer 32

Primary is the conolonization of a previously uncolonised area.
Secondary is the recolonization of a previously colinzed area that has been disturbed.

Question 33

Describe spatial and temporal changes.

Answer 33

Spatial - changes in the area
Temporal - changes over time

Question 34

Name the 3 considerations when making predictions based on human impact.

Answer 34

-Magnitude
-Duration
-Speed