3.5 POPULATION Flashcards
(135 cards)
1
Q
definition of population
A
- an interbreeding group of organisms of the same species occupying a particular habit
2
Q
why do organisms live in population
A
- more successful in breading and rearing their young
- gaining protection from predators by living in groups (safety in numbers)
- working as a group to locate new food sources
3
Q
problems with living in a population
A
-intraspecific competition (food/space)
-could make the group more vulnerable
some individuals better adapted than others and more likely to survive
4
Q
what increases population sizes
A
more births
immigration
5
Q
what decreases population sizes
A
death
emigration
6
Q
what’s an equillibrium species
A
where the control of their population is by competition within a stable habitat
7
Q
carrying capacity
A
the maximum number around which a population fluctuates in a given environment
8
Q
what should a growth curve for an equilibrium species look like
A
sigmoid shape curve
9
Q
what;s environmental resistance
A
environmental factors that slow down population growth
10
Q
explain negative feedback in terms of population size
A
regulates population sizes. it is a change in response to a first change to bring numbers back to the original levels. negative feedback always brings about change to return levels to optimum. always be fluctuations in population numbers but around the set points
11
Q
density
A
number of species in a particular area
12
Q
what type of factors affect population size
A
biotic/abiotic factors
13
Q
what are biotic factors
A
living and are part of the environment of an organism
e.g predators, parasites and competitors
density-dependent
14
Q
what are abiotic factors
A
non-living parts of the environment of an organism
e.g. temperature, oxygen, shelter, pollution
15
Q
what does being density-dependent mean
A
they affect a higher proportion of the population when there is a high population density
16
Q
affect of abiotic factors
A
the same regardless of the size of the population
17
Q
interspecific vs intraspecific
A
inter = between different species
intra = between the same species
18
Q
four stages of the one-step growth curve
A
lag phase
log (exponential) phase
stationary phase
death (decline) phase
19
Q
what’s a fugitive species
A
they cannot tolerate competition. to increase in numbers they reproduce rapidly and have effective dispersal mechanisms. they are able to invade new environments rapidly
20
Q
example of a fugitive species
A
algae and weeds
21
Q
what type of growth is the usual patter for equilibrium species
A
usual pattern is a sigmoid (S-shaped) curve called a one-step growth curve
22
Q
example of population that show a one-step growth curve
A
bacteria and rabbit
23
Q
explain lag phase
A
preparing/adapting for growth
need to reach sexual maturity (find mates)
enzymes synthesised
DNA replicated
24
Q
explain log phase
A
bacteria divides at a constant rate, population doubles per unit of time (increase logarithmically
nutrients are abundant
exponential growth
25
explain stationary phase
competition for nutrients mean reproduction rate is the same as the death rate
reached carrying capacity for that environment
26
why can the population not continue to grow indefinitely
due to environmental resistance
(food, waste, space)
27
why does population fluctuate in the stationary phase
as a response to an envirionmental change
28
explain the death phase
the death rate is greater than the reproduction rate due to nutrient depletion and and toxic accumulation.
29
what is carrying capacity
the maximum number around which a population fluctuates in a given environment
30
why have the numbers of rabbits on rabbit island been able to exceed carrying capacity
due to the visitors on the island feeding the rabbits
31
what is abundance
the number of individuals of the same species in a given area or volume
32
how could you sample animals
capture-mark-recapture-lincoln's index
kick sampling in a stream
33
how could you sample plants
quadrat- random sampling
transect
34
what is distribution
describes the area or volume in which a species is found
35
how could distribution be measured when the habitat is not uniform
line transect- shows which organism lie on the line at regular intervals
belt transect- quadrats placed along the line
36
how to do %frequency
(transects)
count how many squares the plant appears in
express as a %of the total
37
how to work out plant density
transects
count the individuals of a particular species and calculate a mean over 10 quadrats
38
what does a kite diagram show
the percentage cover of the species across the belt transect
show the abundance and distribution of species along a transect
39
define a community
interacting populations of 2 or more species living in the same habitat at the same time
40
define succession
the change in structure and species composition of a community over time
41
an example of succession
when bare rock or barren land is first colonised
42
what is each stage of succession called
a sere
43
example of a sere
xerosere
hydrosere
44
what is xerosere
succession that starts in a dry area
45
what is a hydrosere
succession that starts in water
46
what is primary succession
occurs on an entirely new habitat which has never been colonised
e.g. bare rock
47
what is a pioneer species
the first organism to colonise a habitat. they are found in the first seral stage e.g. lichens, moss, algae
they change the rock surface by allowing humans to accumulate
48
what is secondary succession
the series of changes in a community which takes place on a disturbed or damaged previously inhavited/colonised habitat
e.g. bare soil after a fire
some soild, spores and seeds will remain from the previous community and so the area can be rapidly re-colonised by plants and animal
49
what is a climax community
the stable community which has reached equilibrium (undergoes no further succession) e.g. mature woodland. it is the final seral stage
50
pioneer stage
plant species
animal species
lichens
no animal
51
characteristics of primary colonisers/ pioneer stage
ability to withstand dry conditions and colonise bare rock. release nutrients when they die and decompose
52
small plants/ secondary colonisers
plant species
animal species
mosses
detritus feeding mites
53
characteristics of secondary colonisers
soil and nutrients have been left by dying organisms to support further communities
54
medium plants
plant species
animal species
ferns
insects, millipedes and worms
55
characteristics of medium plants
thicker layer of soil has built up due to increase in organic matter from dying plants
56
tertiary colonisers/ small flowering plants
plant species
animal species
grasses
centipedes (secondary consumer)
butterflies and moths
57
characteristics of tertiary colonisers
even thicket layer of soil has built up due to increase in organic matter from dying plants
58
larger flowering plants/ tertiary colonisers
plant species
animal species
shrubs
reptiles mammals and birds
59
tertiary colonisers characteristics
soil continues to improve due to increase in organic matter from dying plants
60
climax community
plant species
animal species
deciduous oak
reptiles mammals and birds
61
climax community
characteristics
stable state with a balanced equilibrium of species. established plants are rarely replaced. animals exist as well as plants
62
6 succession stages
-pioneer stage/ primary colonisers
- small plants/ secondary colonisers
- medium plants
- small flowering plants/ scrubland
-climax community
63
why is secondary succession a more rapid process compared to primary succession
- spores and seeds remain alive in soil
- influx of animals and plants through dispersal and migration from surrounding areas
succession doesn't start with pioneer species
(starts with tertiary colonisers)
64
factors affecting succession
immigration
competition
facilitation (mutualism and commensalism)
65
what imigration affects succession
imigration of
spores
seeds
animals
non-native species
66
what do plants compete for
light, space, nutrients
67
what do animals compete for
shelter, food , water, mates
68
when can competition happen
at all seral stages. two species cannot occupy the same niche
one with competitive advantages survives
69
what is a niche
the place and role of each species within an ecosystem
70
what is disclimax
disruptive climax. when human activity maintains a stable community and can prevent the formation of a climatic climax community
71
what is facilitation
allowing something to happen through positive interactions
72
benefit of facilitation in an ecological community
it provides better resource availability and refuge from physical stress, predation and competition
73
what is symbiosis
the broad term to describe relationships between organisms
74
what is mutualism
interaction benefiting both species
75
example of mutualism
flowering plants and pollinators
76
what is commensalism
one organism benefits and the other is unaffected
hard to define
77
example of commensalism
cactus and shrubs
78
what can affect the natural stages of succession
examples
human interference
grazing by sheep
deforestation
using land to grow crops
deliberate burning of heather moors to prevent a climax community stage being reached
79
what's a microhabitat
areas of varying characteristics within a habitat
e.g, habitat found in a stream in a woodland
80
what is a species
a group of similar organisms that can breed together to produce fertile offspring
81
what is an ecosystem
a community of organisms which together with their physical environments form a self perpetuating ecological unit
82
define population
a group of interbreeding organisms of one species in a habitat
83
define community
the sum total of the organisms within a habitat and their interactions
84
define a habitat
the particular area where a community of organisms lives
85
what is ecology
the stufy of the inter-relationships between organisms and their environments
86
what is a biosphere
the life-supporting layer of land, air and water that surrounds the earth
87
what is an equilibrium species
one that controls their population by competition rather than by reproduction and dispersal
88
what is population size regulated by
negative feedback
89
explain negative feedback to regulate a population size
e.g if the population falls below a set point, environmental resistance is temporarily relieved so that the population rises again
90
how can you measure abundance (animals)
capture-mark-recapture
kick sampling in a stream
91
how can you measure abundance (plants)
quadrats
estimating percentage cover and percentage frequency
92
what is an ecosysytem
an area that has a particular community of plants and animals interacting with their environment
93
order of energy flow along food chains in an ecosystem
sunlight
producers
primary consumers
secondary consumers
94
what does a habitat provide
means of survival
food water
soil
appropriate temperature etc.
95
what is the photosynthetic efficiency usually
2%/5%
96
what do photoautotrophs do
use light energy from the sun to fix CO2 into organic molecules by photosynthesis. (GPP)
97
what is GPP
all the energy that is used to make new products
98
what happens to lots of GPP
used for protein synthesis and lost to the environment as heat
99
what is NPP
GPP-respiration
100
what is a saprobiaont
a micro-organism that obtains its food from the dead or decaying remains of other organisms
e.g. fungi
101
what is a detrivore
feed on dead organic material such as faeces/fallen leaves and remains of dead organisms
102
how is NPP transferred
when the organism is consumed by a consumer
death/urine and faeces and loss of organic tissue allows energy to be passed on from decomposers
103
example of interacting factors that can affect the length of a food chain
if energy is transferred more efficiently through trophic levels, the food chain can be longer
larger ecosystems can support larger food chains
104
what is secondary productivity
the rate at which consumers convert the chemical energy of their food into biomass
105
why is energy transfer between trophic levels inefficient
not all the organism is eaten and not all can be digested
some lost in faeces and urine
some lost as heat in respiration
106
what do a pyramid of numbers show
number of species in each stage of a trophic level
107
issues with pyramids of numbers
can be inverted
difficult to draw to scale
not taking the size of the organism into account
108
what do pyramid of biomass show
the total dry mass of the organism at each trophic level
109
issues with the pyramid of biomass
difficult to accurately measure
difficult to obtain dry mass
species with similar biomass may have different lifespans
doesn't show energy flow
110
explain the process of primary succession
pioneer species colonises bare rock, lichens arrive at the rock (by wind or by animals)
the lichens arode the rock as the grow and decompose as they die. this builds up soil. when the eroded rock builds up in cracks the mosses can colonise. this allows enough soil to accumulate to allow grasses to establish then herbaceous plants then shrubs and finally woodlands (this is the climax community)
111
2 reasons CO2 has increased
burning fossil fuels
deforestation
112
how does burning fossil fuels lead to an increases CO2
releases previously locked up CO2 into the atmosphere
113
how does deforestation lead to an increase in CO2
removes large quantities of photosynthesising biomass, less CO2 being removes)
114
describe the process of the carbon cycle
1. plants take in CO2 and use it in photosynthesis to make organic molecules that are passed through the food chain
2. plants and animals respire and excrete CO2
3. combustion releases CO2
4. decomposers respire releasing CO2
5. formation of fossil fuels
115
what is a carbon footprint
the total amount of CO2 generated by an individual, product or service over the course of a year
116
what is decomposition
the breakdown of organic material into simpler compounds by saprotrophic micro-organisms (e.g. bacteria and fungi)
117
what is the rate of decomposition affected by
temperature; slower when cold
pH; slower when acidic
O2 availability ; slower when less is available
118
what does saprotrophic nutrition describe
how decomposers obtain their energy
-they release hydrolytic enzymes from their hyphae (break down complex carbon-containing organic molecules)
-digested products can then be absorbed and used for respiration
119
affects of global warming
affects species distribution, artic and antarctic species are at risk of becoming extinct
melting polar ice resulting in flooding
increasing frequency of forest fires
120
affects of global warming on farming
-agriculture likely to be affected
may have to alter their practices to accommodate climate change
some areas may become drier and need drought resistance plants
121
4 processes of the nitrogen cycle
ammonification
nitrification
nitrogen fixation
denitrification
122
explain ammonification
bacteria and fungi decompose dead animals and plants, faeces and urine into ammonium ions
123
explain nitrification
addition of nitrogen into the soil
ammonium ions formed in ammonification are converted
ammonium ions converted to nitrite by nitrosomonas
nitrite to nitrate by nitrobacter
124
what do the conversions in nitrification require
aerobic conditions
125
explain nitrogen fixation
atmospheric nitrogen converted directly into nitrogen compounds by nitrogen fixing bacteria. free living bacteria include Azobacter (most of the nitrogen fixation)
sympiotic nitrogen fixing = rhizobium
126
where is Rhizobium found
in the root nodules of legumes (peas, beans, clover)
127
explain denitrification
loss of nitrate from the soil
anaerobic bacteria (pseudomonas) convert nitrate ions to nitrogen
128
what conditions do farmers encourage
aerobic conditions (leads to nitrification)
discourage anaerobic conditions (leads to denitrification)
129
what non-biological processes have an impact in the nitrogen cycle
-fertilisers add nitrogen to the soil
- nitrogen fixation can also be done by lightning
- leaching of minerals removes nitrogen from the soil
130
what are some of the human influences on the nitrogen cycle
by fixing atmospheric nitrogen artificially using chemical processes that convert it into fertilisers
large amounts of animal waste from stock rearing is used as manure
farming practices e.g. ploughing fields in order to improve aereation of the soil
131
what is eutrophication
artificial enrichment of aquatic habitats by excess nutrients (often by fertilisers)
132
explain the process of eutrophication
nirate is readily leached from soil and washed into rivers. algal bloom blocks light which causes plants to die. the decomposer population increases and there is an increased biological oxygen demand.
133
what does eutrophication lead to
reduced nitrate to nitrite
134
define trophic level
where an organism fits in a food chain
135
suitable units for energy transfer across an ecosystem
KJ/m2.year
