Topic 2: Ecosystem Dynamics

Question 1

what are autotrophs

Answer 1

an organism that can feed itself – able to convert inorganic carbon-containing compounds into organic compounds – e.g. plants - done thru photosynthesis

Question 2

what are the two stages of photosynthesis

Answer 2

light dependent and light independent

Question 3

define biomass

Answer 3

the total amount of living tissue in a defined volume or area – often defined as the “dry weight”

Question 4

what is gross primary productivity - explain

Answer 4

the total biomass that autotrophs create through photosynthesis.

Question 5

what is net primary productivity

Answer 5

the biomass left over after the autotroph has used what it needs itself

Question 6

define heterotoph

Answer 6

organism that cannot manufacture its own food - eats plants/ animals

Question 7

what are trophic levels

Answer 7

feeding levels!! - a group of organisms within an ecosystem which share the same relationship to the producers in the ecosystem

Question 8

list a few different trophic levels

Answer 8

producers, primary consumers, secondary consumers (first level that feed on animals rather than producers), tertiary consumers

Question 9

what is a food chain

Answer 9

diagram that shows the linear flow of energy thru an ecosystem

Question 10

what is a food web

Answer 10

similar to a food chain, but includes many interconnected ones

Question 11

define what a biomass pyramid is

Answer 11

shows the total biomass of the organisms at each trophic level

Question 12

what is an ecological niche

Answer 12

the role a species plays in the ecosystem

Question 13

define carrying capacity

Answer 13

the pop. size that the environment is able to support - given the availability of food, water, shelter, etc

Question 14

define limiting factor

Answer 14

prevents something from increasing

Question 15

what are the factors that affect population size

Answer 15

immigration, emigration, births, deaths

Question 16

how to calculate population change

Answer 16

(births + immigration) - (deaths + emigration)

Question 17

what is succession

Answer 17

a change in the species structure of an ecological community over time

Question 18

what is a pioneer species

Answer 18

hardy species which are the first to colonise barren environments

Question 19

what is a sere

Answer 19

an intermediate stage found in an ecological succession - each stage of succession

Question 20

what is “the final sere” in ecosystem succession

Answer 20

the end result of succession is called a climax community
(stable, reaching equilibrium). They take a long time to become established and damage cannot be restored quickly (other terms: mature/ old growth)

Question 21

what is primary succession

Answer 21

succession that begins on lifeless ground where there is no soil, or the soil is incapable of supporting life – begins on newly exposed or created ground

Question 22

what are the features of a pioneer species

Answer 22

1. able to fixate nitrogen (or a symbiotic association with something that can)
2. tolerance to extreme conditions
3. rapid germination of seeds
4. ability to photosynthesise

Question 23

what is secondary succession

Answer 23

begins in an area where a disrupted community already exists (eg. after a fire)

Question 24

what are methods for estimating CO2 concentration in past ecosystems

Answer 24

1. stomatal density in plants - as CO2 level increases, density decreases
2. ice cores - one layer of ice per year - when the layers form, the ice traps samples of the atmosphere in tiny bubbles

Question 25

what are the methods for estimating temperatures in past ecosystems

Answer 25

1. ice cores - looking at the proportion of different oxygen or hydrogen molecules
2. diatoms (tiny algae) - found to be directly linked to ocean temperatures - the warmer the sea temp., the lower the diatom biodiversity

Question 26

what are methods for estimating the types of past ecosystems

Answer 26

1. pollen - shows the ecosystems of the past - like the diatoms of the land
2. other fossils (eg. trees)

Question 27

list the different ways in which humans impact biodiversity

Answer 27

• habitat destruction
• land and soil degradation (loss of quality)
• creation of monocultures (uniform quality produce - demand from food industry - favours genetic uniformity)
• selective breeding
• biotechnology (cross species genetic modification - superior to natural species - so used less and less for farming)