Chapter 4: Energy and Matter in Ecosystems

Question 1

what is a biogeochemical cycle

Answer 1

the cycling of matter through the abiotic factors such as rocks and atmosphere and biotic factors such as plants and animals

Question 2

what is the geochemical cycle

Answer 2

matter cycled through the lithosphere through chemical reactions in the earths crust

Question 3

what is a chemotrophic organism

Answer 3

organism that are autotrophic that live below the zone where light can penetrate

Question 4

what is biomass

Answer 4

the total amount of dead or alive biological matter in a given area at a given time.

measured g/m^2

Question 5

what is primary productivity

Answer 5

the amount of energy turned into biomass by producers

Question 6

what is photosynthetic efficiency

Answer 6

how well a producer turns light energy into carbs

factored by temperature, season and altitude

Question 7

what is primary productivity measured in

Answer 7

kj/m^2 year^1

Question 8

what role do herbivores serve

Answer 8

they are able to break down cellulose

Question 9

what is detritus

Answer 9

dead animal or plant matter

Question 10

when would an inverted pyramid of numbers occur

Answer 10

when a parasite feeds on the apex predator

Question 11

when would a pyramid of biomass be inverted

Answer 11

when an efficient producer such as phytoplankton has a short life cycle but produces a lot of energy for it’s size.

Question 12

key phrases of carbon cycle

Answer 12

moving through reservoirs rapidly

most abundant element in living things

circulate through biotic and abiotic

carbon cycle

mainly carbon dioxide gas

Question 13

why are nitrogen fixing symbiotic relationships important

Answer 13

no free nitrogen particles in the soil

all of it is fixed into an organism

doesn’t get eroded away

extra nitrogen can kill earthworms and cause algal blooms when soil erosion carries it away

Question 14

what are nitrogen-fixing bacteria symbiotic with legumes called

Answer 14

azotobacter

Question 15

define ecological niche

Answer 15

an organisms function in an environment - the time they feed, what they feed on, habitat etc

Question 16

explain fundamental vs realised niche

Answer 16

the fundamental niche is the niche a species would fill if there was no outside competition - theoretical

the realised niche is narrower and is more practical as this accounts for competition from outside species

such as an ideal situation for a bilby is they would be able to be diurnal and nocturnal but due to excess competition during the day it has adapted to the realised niche

Question 17

explain what resource partitioning is

Answer 17

resource partitioning is when multiple species adapt to exploit different niches of an area to reduce competition

e.g birds adapt different beak shapes and sizes to exploit different areas of the tree

Question 18

what is the competitive exclusion principle

Answer 18

multiple species cannot fill the same niche for an extended period of time

one species will out compete the other

Question 19

explain what a keystone species is

Answer 19

little abundance compared to the effect they have on the ecosystem

seed dispersal, predation, nutrient cycling

Question 20

what is the role of decomposers

Answer 20

they break down complex organic materials into simple inorganic nutrients so that they can reenter the foodchain via producers

Question 21

explain what nitrifiers, denitrifiers and nitrogen fixers are

Answer 21

nitrifiers turn organic waste like faeces into nitrites

denitrifiers turn nitrates in the soil into nitrogen gas

nitrogen fixers turn atmospheric nitrogen into nitrates and nitrites