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Population Size and Ecosystems C1 Flashcards

1
Q

what is a population?

A

a group of interbreeding organisms of the same species, occupying a particular habitat

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2
Q

what four factors cause ecosystems to be dynamic and population numbers to fluctuate?

A

birth rate
death rate
immigration
emigration

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3
Q

define birth rate

A

the reproductive capacity of a population

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4
Q

define death rate

A

the proportion of individuals dying per unit time

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5
Q

define immigration

A

the movement of individuals into a population of the same species

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6
Q

define emigration

A

the movement of individuals out of a population of the same species

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7
Q

when describing population growth of bacteria and yeast, would it be correct to use the term ‘birth rate’? If not, what could be used instead?

A

No
we can use rate of cell division instead

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8
Q

how is a population of an equilibrium species controlled?

A

within a stable habitat through competition

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9
Q

what is the pattern of growth if conditions of temperature and nutrients are favourable?

A

sigmoidal (S-shaped)

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10
Q

give the 4 labels of the phases of the population growth curve and what they mean

A

1) lag phase - reproduction rate ≥ death rate
2) log phase - reproduction rate > death rate
3) stationary phase - reproduction rate = death rate
4) death phase - reproduction rate < death rate

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11
Q

what are the axis labels of the population growth curve?

A

number of organisms (x) and time (y)

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12
Q

describe lag phase

A

slow rate of reproduction
period of intense metabolic activity such as enzyme synthesis
in sexually reproducing organisms this represents the time for individuals to reach sexual maturity
for yeast placed in nutrient broth it represents the time it takes for them to hydrate

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13
Q

describe log phase

A

rapid increase in population numbers as more individuals available for reproduction
no factors limiting growth
bacterial cells double per unit time
rapid rate of reproduction can’t be maintained indefinitely
environmental resistance occurs at the end of log phase

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14
Q

what environmental resistance will occur for rabbits on a new island?

A

predation, parasitism and disease and competition for food/habitats

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15
Q

what environmental resistance will occur for bacteria in a flask?

A

run out of space, lack of oxygen/nutrient availability, competition for nutrients eg glucose and oxygen and toxic waste build up

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16
Q

describe stationary phase

A

birth rate or cell division is equal to death rate
factors limiting further growth
population reached carrying capacity
actual number of individuals will fluctuate around carrying capacity in response to environmental changes
yeast change from asexual to sexual reproduction as they reach stationary phase and some individuals survive as spores

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17
Q

define carrying capacity

A

the maximum number of individuals a population can sustain within a particular environment

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18
Q

describe death phase

A

environmental factors result in death rate greater than birth rate eg glucose running out in a nutrient broth or build up of ethanol when growing yeast

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19
Q

how to calculate population increase from a graph

A

when increase is very large, the range of numbers is too great to plot a graph on a linear scale
therefore a log10 scale is used so each mark on the population scale is 10x the previous mark

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20
Q

what are two factors that distinguish what will slow down population growth and what might cause a population crash?

A

density dependent factors and density independent factors

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21
Q

describe density dependent factors and give examples

A

factors that have a greater effect the larger the population size and more likely to slow down the population growth rate
eg: disease and parasitism, food availability and toxic waste build up

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22
Q

describe density independent factors and give examples

A

factors that have an effect regardless of the size of the population and is more likely to cause a population crash
eg: floods, fires and sudden temperature changes

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23
Q

describe predator-prey relationships

A

as the population density of a particular prey increases, more are eaten by the predator
as a result, the prey population decreases
when the prey population increases there is more available food for the predator
as a result, the predator population increases

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24
Q

describe competition and give the two types of competition

A

it has large impact on the potential breeding success and survival of an organism

intra-specific competition
inter-specific competition

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25
what is the difference between intra and inter specific competition?
intra-specific is competition between members of the same species inter-specific is competition between members of different species
26
define the concept of niche
the ecological role and position that an organism takes within an ecosystem, dependant on the resources it uses only one species can occupy a particular niche within an ecosystem, one species will always outcompete another
27
how can the concept of niche be demonstrated?
by growing two species of the protozoan 'Paramecium' in flasks in a lab both species can grow well in flasks when grown separately but when grown together 'P-aurelia' outcompetes 'P-caudatum' for food so the population of 'P-caudatum' falls
28
what is the type of competition demonstrated in the protozoan experiment?
inter-specific
29
what is the study of abundance and distribution called?
biogeography
30
what is the sampling technique in an area where abiotic variables are uniform?
1 - set up a 10m x 10m grid and use random numbers to generate coordinates to determine where to place the 1m^2 quadrat 2 - count the number of species or percentage cover in each quadrat 3 - repeat at 10 random coordinates 4 - calculate a mean for each species
31
why is percentage cover used instead of counting?
it is quite difficult to count individual plants such as grass or moss using a gridded quadrat can give a better estimation a quadrat divided into 10 x 10 squares would mean each square is represented by 1%
32
what is the sampling technique if you wanted to sample the change in species over time within an area?
set up a permanent area within the habitat and create a 10m x 10m grid generate random coordinates for quadrat placement and record the number/percentage cover of plant species review/visit periodically to gain results for comparison
33
what is the sampling technique in an area where there is a change in an abiotic factor?
random placement of quadrats is unsuitable if there is an environmental gradient such as altitude or light intensity a line transect is used
34
describe a line transect
it would be used to describe the difference in plants as you enter a wood etc record the species touching the transect at each point
35
describe a belt transect
provides more data than a line transect place a quadrat at regular intervals along the transect estimate the density/percentage cover of plant species in each quadrat since an environmental gradient is involved, it is useful to measure the varying abiotic factor
36
describe how to set up a transect
1 - run a 20m tape measure along the area to sample 2 - for a line transect, identify the species touching the transect every half metre along the tape measure 3 - for a belt transect, place a quadrat down every half metre along the tape measure and calculate percentage cover 4 - repeat multiple times within an area to ensure a representative sample and for a belt transect, calculate a mean
37
describe kite diagrams
they can be drawn when looking at percentage cover usually presented in a table and end diagram looks similar to a 'kite'
38
give examples of abiotic factors
light intensity, amount of water and nutrients, temperature and altitude
39
give examples of biotic factors
living bacteria, competition for resources, the amount of predators and disease
40
define ecosystem
a characteristic community of interdependent species interacting with abiotic components in their habitat can be large or small
41
what is the source of all energy for an ecosystem?
the sun - light energy trapped by photosynthesis
42
define habitat
the place in which an organism lives often contains a community of organisms
43
define community
it is populations of different species living within the same habitat
44
define trophic levels
feeding levels within an ecosystem
45
which organisms are in the first trophic level?
producers
46
where does energy flow through?
the sun, producers and consumers
47
what happens to energy on the death of organisms?
some remains locked up as organic material
48
what is detritus?
dead particulate organic matter
49
why are decomposers not classed as a trophic level?
they feed from every level
50
draw out a trophic level diagram
https://www.khanacademy.org/science/ap-biology/ecology-ap/energy-flow-through-ecosystems/a/food-chains-food-webs
51
why does an ecosystem rarely support more than 5 trophic levels?
a lot of energy is lost at each level eg heat from respiration, excretion/indigestion and inedible parts
52
what is photosynthetic efficiency?
a measure of the ability of a plant to absorb light energy
53
give the formula of photosynthetic efficiency
energy incorporated into photosynthetic products ÷ total light energy falling on the plant x 100
54
why isn't all light energy that falls on a plant absorbed by photosynthetic pigments?
wrong wavelength reflected hits non-photosynthetic parts of plant transmitted straight through the leaf
55
what is gross primary productivity (GPP)?
it is the rate of production of chemical energy in organic chemicals by photosynthesis (KJ m-2 year-1)
56
what is net primary productivity (NPP)?
it is the gross primary productivity minus the energy used up by the producers in respiration in a year therefore the energy in the plants' biomass/rate at which producers convert energy into biomass
57
what does NPP represent?
the potential food energy available to heterotrophs in ecosystems
58
why don't consumers take all of this potential energy?
some parts of the plant are inedible eg roots and bark some parts are indigestible eg cellulose some lost as heat by respiration
59
what is primary productivity only for?
producers!
60
define biological productivity
the rate at which biomass accumulates in an ecosystem
61
define biomass
the dry weight of organic matter comprising a group of organisms in a particular habitat
62
what do ecologists do to find the dry mass of plants?
dry samples in an oven at 65°C
63
describe how the ecologists would be confident that all the water had been removed but none of the organic matter had been lost?
repeat until constant mass recorded and ensure there is no combustion
64
what is secondary productivity?
the rate at which consumers accumulate energy from assimilated food in biomass in their cells/tissues
65
explain why carnivores have a more efficient energy conversion than herbivores
protein is more rapidly and easily digested than cellulose a lot of cellulose is lost in the faeces of a herbivore
66
explain why farmers keep animals in barns during the winter
they won't have to use as much energy maintaining their body temperature so more energy is available to produce biomass (meat)
67
what is gross ecological efficiency?
a measure of how much energy is transferred from one trophic level to the next
68
give the formula of gross ecological efficiency
energy in trophic level ÷ energy in previous trophic level x 100
69
how do values for gross ecological efficiency differ in different ecosystems?
they are often around 10% oceanic food chains can have high values of around 40% food chains involving birds and mammals may be as low as 1%
70
why is there a difference between aquatic GEE and birds/mammals GEE?
many aquatic organisms don't regulate their body temperature and so save a lot of energy birds and mammals maintain a high body temperature and this uses up a lot of energy and is therefore less efficient
71
describe pyramids of energy
can be used to give a quantitative account of the feeding relationships in a community shows the quantity of energy transferred from one trophic level to another per unit area or volume per unit time (eg; KJ m2 in one year)
72
why can a pyramid of energy never be inverted?
energy is always lost from one trophic level to the next it cannot be produced
73
what aspect of a pyramid of energy overcomes problems associated with pyramids of numbers and biomass?
it can never be inverted
74
what causes ecosystems to be dynamic and subject to change?
interactions of the organisms and their environment
75
what is succession?
the change in structure and species composition of a community over time
76
what is primary succession? and give an example
the introduction of plants/animals into areas that have not previously supported a community e.g bare rock
77
what is a sere?
each stage during succession when particular communities dominate
78
what are pioneer species?
the first organisms to colonise the rock e.g lichens
79
describe the process of primary succession
pioneer species arrive these organisms slowly erode the rock, and the accumulation of dead and decomposing organic material leads to the formation of primitive soil as the soil develops, grasses become established as the soil builds up and nutrient levels increase, deep-rooted shrubs appear over a very long period, trees and woodlands become established this results in a stable, long-lived community known as the climax community
80
what is secondary succession?
the reintroduction of organisms into a bare habitat previously occupied by plants and animals that may have been damaged by fire or tree felling
81
what 4 things is succession affected by?
migration competition facilitation commensalism
82
describe migration
the arrival of spores, seeds and animals is vital for succession to progress immigrating non-native species may spread themselves widely, altering communites
83
describe facilitation
positive interactions between species that become increasingly significant as succession progresses
84
describe mutualism/commensalism
an interaction between two species that is beneficial to both e.g flowering plants and their pollinators
85
give two factors that assist in the colonisation of a habitat
the seeds previously dispersed by flowering plants and spores from fungi may remain in the soil and begin to germinate migrating animals produce droppings which improves nitrate levels in the soil
86
give six ways human interference can affect the natural development of the climax community during succession and how?
grazing - livestock such as sheep eat the grasses and other plants moorland management - heather colonisation is controlled by burning farming - ploughing and growth of crops by monoculture stops trees and shrubs from getting established deforestation - trees are cut down and this can cause erosion of the soil industry - e.g coal mining and quarrying of stone urban development - building of new roads and buildings

biolala (32 decks)

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