populations Flashcards
(50 cards)
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12
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define population
A
a group of organisms of
the same species
13
Q
whats the equation for a stable population?
A
births + immigration = deaths + emigration
14
Q
define density dependent factors
A
Density dependent factors are biotic and affect population growth based on population size
15
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define density independent factors
A
Density independent factors are abiotic and affect population growth regardless of population size
16
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define carrying capacity
A
the maximum number of individuals of a species that the environment can support indefinitely
17
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describe lag phase for a bacterium/ yeast
A
Enzymes are synthesised;
DNA is replicated
18
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describe exponential phase for a bacterium/yeast
A
Population doubles every
unit of time; nutrients
abundant
19
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describe stationary phase for a bacterium/yeast
A
Competition of nutrients
means death and cell
reproduction happen at
the same rate
20
Q
describe death phase for a bacterium/yeast
A
Nutrient depletion and
toxin accumulation mean
death rate is higher than
cell reproduction
21
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describe lag phase for animals
A
population is limited by low numbers to reproduce
22
describe exponential phase for animals
doubling of numbers with abundant resources
and low predation
23
describe stationary phase for animals (predator prey relationships)
- as the population increases, competition
for resources and predation increases
- death rate is higher than birth rate
-The population decreases, which reduces competition
and the population can increase again
- This continues
indefinitely
24
define ecosystem
an area that has a particular community of plants and animals interacting with their
environment
25
define community
all of the organisms of
all species in an ecosystem
25
define habitat
The place in an ecosystem where an organism lives
26
define photoautotroph
use light energy from the sun to fix carbon dioxide into organic molecules by photosynthesis
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define niche
An organism’s role in the ecosystem
27
define succession
the change in structure
and species of a community over time
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define primary succession
starts from bare rock, where no organism lives
29
define secondary succession
starts from cleared
land where communities have lived before (recolonisation of previously colonised land)
30
describe the stages of primary succession
- Pioneer species colonise bare rock. Lichens blown in as spores arrive
at the rock.
- They erode the rock as they grow and decompose when they die, building up a little soil.
- When the eroded rock builds up in cracks, mosses
can colonise.
- Enough soil accumulates to allow grasses to become established, then herbaceous plants, then shrubs then woodland
- The climax community is the stable end point of succession; no further changes take place
31
describe the steps to carry out a random sampling technique (quadrats)
- Use when the area is uniform like a field
- Grid the area
- To avoid bias, generate random numbers to select co-ordinates
- Place quadrat at co-ordinates and use to count organisms
32
define climax community
the stable end point of succession
33
describe the steps to carry out a random sampling technique (transects)
- Use when there is a change in conditions
- place quadrats at regular
intervals along the line and use to count organisms
- assess vegetation by continuous quadrats along the line
34
define carbon footprint
the total amount of CO2 released attributable to an
individual, product or service over the course of a year
34
define autotrophs
use energy from sunlight
or chemicals to convert inorganic compounds into organic ones
34
define decomposers
(bacteria or fungi) use organic molecules and
convert them to inorganic compounds
35
describe the carbon cycle
- Plants take in CO2 and use it in photosynthesis to make organic molecules passed through food chains
- Plants and animals respire and excrete CO2
- Combustion releases CO2
- Decomposers respire excreting CO2
- The formation of fossil fuels
35
what is the significance of water logged soils ?
- Water-logged soils lack O2
- this favours denitrification and slows nitrification.
-This leads to nitrate poor soil.
36
define leaching
soluble ammonium, nitrite and nitrate ions dissolve in ground water and drain
away
37
how are water logged soils treated in agriculture?
- ploughing introduces air
to the soil, encouraging nitrification
- Drainage ditches reduce waterlogging and denitrification
38
what are the nitrifying bacteria and what do they do?
Nitrosomonas – convert ammonium to nitrite
Nitrobacter – convert nitrite to nitrate
39
what are the nitrogen-fixing bacteria and what do they do?
convert nitrogen gas to ammonium
Azotobacter – free living in soil
Rhizobium – in root nodules of legumes, symbiotic
40
what is the significance of rhizobium?
- Rhizobium has a symbiotic relationship
with legumes
- It fixes nitrogen gas
into ammonium ions and makes amino acids which it exports to the
legume
- The legume makes a root
nodule for the Rhizobium and provides micro anaerobic conditions needed for nitrogen
fixation
40
what is the denytrifying bacteria and what does it do?
convert nitrate to nitrogen gas
Pseudomonas – thrive in water-logged soils
41
describe eutrophication
- algae undergo an algal bloom
- This blocks light from bottomdwelling plants which die
- the decomposer population increases. As they are aerobic, more
oxygen than usual is utilised out of the water
- Fish and aquatic
invertebrates die and decompose
