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A-level biology component 1 (+immunology) > Populations and Ecosystems > Flashcards

Populations and Ecosystems Flashcards

1
Q

What is a population?

A

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

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2
Q

What factors is the fluctuations in populations dependent on?

A

birth rate
death rate
immigration
emigration

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3
Q

What is the birth rate?

A

The reproductive capacity of a population

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4
Q

What is the death rate?

A

the proportion of individuals dying per unit time

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5
Q

What is immigration?

A

the movement of individuals into a population of the same species

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6
Q

What is emigration?

A

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

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7
Q

What would happen to the population size if birth rate and immigration> death rate and emigration?

A

It would increase

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8
Q

When describing population growth of bacteria and yeast, would it be correct to use the birth rate? If not, what could be used?

A

Cell Division

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9
Q

how is the population of an equilibrium species controlled within a stable habitat?

A

through competition

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10
Q

What happens if conditions of temperature and nutrients are favourable in a population?

A

the usual pattern of growth is sigmodal (S-shaped)- e.g. bacteria placed into a fresh nutrient solution or rabbits newly introduced to an island

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11
Q

What happens on the lag phase?

A

-Slow rate of reproduction
-Period of intense metabolic activity such as enzymes synthesis

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12
Q

What does the lag phase represent in sexually reproducing organisms such as rabbits?

A

the time it takes for individuals to reach sexual maturity

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13
Q

What does the lag phase represent for yeast placed into a nutrient broth?

A

the time it takes for them to hydrate

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14
Q

What happens in the exponential/log phase?

A

-rapid increase in population numbers as more individuals are available for reproduction
-no factors limiting growth
-this rapid rate of reproduction cannot be maintained indefinitely

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15
Q

what occurs at the end of log phase?

A

environmental resistance

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16
Q

what is environmental resistance?

A

all factors that may limit the growth of a population

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17
Q

what happens in the stationary phase

A

-birth rate or cell division is equal to death rate
-factors are limiting any further growth
-the population has reached it’s carrying capacity and the actual number of individual will fluctuate around this in response to environmental changes

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18
Q

what is carrying capacity?

A

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

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19
Q

What happens to yeast as they reach stationary phase?

A

change from asexual reproduction to sexual reproduction and some individuals survive as spores

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20
Q

what environmental resistance will occur for bacteria in a flask?

A

-glucose availability
-overcrowding
-competition
-toxic waste build up

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21
Q

what environmental resistance will occurs for rabbits in a new island?

A

predation, parasitism and disease, competition for food

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22
Q

What happens in the death phase?

A

Environmental factors now result in death rate becoming greater that birth rate e.g. glucose running out of nutrient broth or build up of ethanol (toxic) when growing yeast

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23
Q

How is a population increase calculated from a graph?

A

A log10 scale

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24
Q

When is a log10 scale used?

A

used when a population increase is too large (e.g. in a population of bacteria in a test tube, the range of numbers is too great to plot on a linear scale)

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25
Q

What is a log10 scale?

A

each mark on the population scale is 10x the previous mark

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26
Q

what is the formula for a log scale?

A

no of…at day… - no of…at day… / …-…
antilog10… - antilog10…/ …-…

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27
Q

How is the size of a population regulated?

A

-by the balance between the birth and death rate

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28
Q

what are the sizes of populations like?

A

-populations do not remain constant in size, although the fluctuations are normally small

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29
Q

where do most species in a population lie?

A

near an equilibrium- the carrying capacity

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30
Q

What are the factors that affect population size?

A

-Density dependent factors
-Density independent factors

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31
Q

What are density dependent factors?

A

Factors that have a greater effect the larger the population size (more likely to slow down population growth rate)

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32
Q

What are examples of density dependent factors?

A

-Disease and parasitism
-Food availability
-Toxic waste build up

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33
Q

What are density independent factors?

A

Factors that have an effect regardless of the size of the population (more likely to cause a population crash?- e.g. floods, fires, and sudden changes in temp

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34
Q

What happens as the population density of a particular prey (e.g. snowshoehare) increases?

A

more are eaten by the predator (e.g. lynx), as a result the prey population then decreases

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35
Q

What happens when the prey population increases?

A

there is more food available for the predator, as a result the predator population increases

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36
Q

What does the two types of competition do?

A

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

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37
Q

What are the two types of competition?

A

intra-specific competition
inter-specific competition

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38
Q

what is intra-specific competition?

A

competition between members of the same species

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39
Q

what is inter-specific competition?

A

competition between members of different species

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40
Q

What is the concept of niche?

A

only one species can occupy a particular niche within an ecosystem, one species will always outcompete the other

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41
Q

How can the concept of niche be demonstrated?

A

-by growing two different species of the protozoan Paramecium in flasks in a lab
-both grow well in flasks when grown separately, but when grown together P.aurelia P.caudatum for food, so the population of P. C falls

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42
Q

What type of competition is demonstrated in the experiment including the protozoan Paramecium?

A

Interspecific as only one species can occupy one niche

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43
Q

What is biogeography?

A

the study of species abundance and distribution

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44
Q

How do you work out biogeography in an area where abiotic variables are uniform?

A

-set up a 10 m x 10 m grid and use random numbers to generate coordinates to determine where to place the 1m2 quadrat
-count the number of species or percentage cover in each quadrat
-repeat at 10 random coordinates
-evaluate a mean for each species

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45
Q

what must i say when mentioning random sampling in the exam?

A

say how I would ensure my sampling is random, e.g. through generation of random coordinates

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46
Q

What should you do for consistency when placing down a quadrat?

A

always place the bottom of the quadrat at the coordinate

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47
Q

How is density calculated?

A

Count the number or individuals in 10 quadrants and calculate a means, data may be represented as a bar graph

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48
Q

why is it useful to estimate percentage cover?

A

it is difficult to count individual plants such as grass or moss

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49
Q

What would you do if you wanted to sample the change in species over time within an area?

A

-Set up a permanent area within the habitat and create a 10m x10m grid
-Generate random coordinates for quadrat placement and record the number or percentage cover of plant species
-This grid would be visited periodically (every 10 years) to gain results for comparison

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50
Q

What would you do if you wanted to sample in an area where there is a change in an abiotic factor?

A

-Random placement of quadrants are unsuitable if there is and environmental gradient such as altitude or light intensity
-A line along the gradient is used instead
-This is called a transect

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51
Q

What does a line transect do?

A

-Used to describe the difference in plants as you enter a wood.
-Simply record the species touching the transect at each point

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52
Q

What does a belt transect do?

A

-Provides more data than a line transect
-Place a quadrat at regular intervals along the transect
-Estimate the density or percentage cover of plant species in each quadrat.
-As there is an environmental gradient, it is useful to also measure the varying abiotic factor, e.g. light intensity

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53
Q

How is a transect set up?

A

-Run a 20m tape measure along the area to sample
-For a line transect, identify the species touching the transect at every half metre along the tape measure
-For a belt transect, place a quadrat down every half metre along the transect and calculate percentage cover
-Repeat multiple times within an area to ensure a representative sample. For a belt transect repeat and calculate a mean

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54
Q

When can kite diagrams be drawn?

A

when looking at percentage cover

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55
Q

What is the distribution of a species determined by?

A

A range of different variables which can be grouped into abiotic (non-living) factors and biotic (living) variables.

56
Q

What are the abiotic factors?

A

-light intensity
-amount of water and nutrients
-temperature

57
Q

What are the biotic variables?

A

-bacteria which are living
-competition for resources
-the amnount of predators and disease

58
Q

What type of factors are density dependent factors?

A

biotic

59
Q

What type of factors are density independent factors?

A

abiotic

60
Q

What are the three sampling techniques I must be familiar with?where fit th

A

-Random quadrat sampling within a given area where the abiotic factors are uniform
-Interrupted belt transects and line transects where you want to estimate the densities across an area where biotic factors my vary
-Mark-Release-Recapture- for animals that move within

61
Q

What is the equation for mark capture release?

A

number of first captured x number of captured/ and marked/ number of marked when recaptured

62
Q

What is an ecosystem?

A

-A characteristic community of interdependent species interacting with abiotic components in their habitat
-Can be large or small

63
Q

What is the source of energy for an ecosystem?

A

Light energy from the sun trapped by photosynthesis provided the energy for almost all ecosystems (other than those based on chemosynthesis)

64
Q

What is a habitat?

A

A place where in which an organism lives -often contains a community of organism

65
Q

What is a community?

A

populations of different species living in the same habitat

66
Q

What is photosynthetic autotrophic?

A

organisms with the ability to make complex organic molecules like glucose from simpler inorganic ones like CO2 and H2O, using energy from sunlight

67
Q

What are trophic levels?

A

Feeding levels within an ecosystem

68
Q

What are the first trophic level?

A

producers

69
Q

How does every flow in trophic levels!

A

between the sun, producers and consumers

70
Q

What happens on the death of organisms (tropic levels)?

A

some energy remains locked up as dead organic material

71
Q

what is detritus?

A

dead particulate organic matter

72
Q

Why are decomposers not classed as a trophic level ?

A

They feed from every level

73
Q

What are the trophic levels?

A

-1. producers (plants)
-2. primary consumers (herbivores)
-3. secondary consumers (carnivores)
-4. tertiary consumers (top carnivores)

74
Q

Why does an ecosystem rarely support 5 levels?

A

-some energy is released at each trophic level- e.g. during respiration (lost as heat) and excretion (urea with energy will in it or lost in egested material
-because energy is lost between each trophic level, very little energy remains at level 5 (not enough to sustain another trophic level)

75
Q

what does photosynthetic efficiency depend on?

A

external factors such as light intensity and temperature

76
Q

What is photosynthetic efficiency?

A

a measure of the ability of a plant to absorb light energy and convert this light energy to chemical energy

77
Q

Why doesn’t all light energy that falls on a plant get absorbed by photosynthetic
pigments?

A

-Wrong wavelength to be absorbed by pigments light outside the visible spectrum e.g. infrared/UV isn’t used in photosynthesis
-Green light is reflected by chlorophyll pigment (even if it hits the chlorophyll pigment)
-Transmitted straight through the least (does not hit chlorophyll pigment)

78
Q

What is gross primary production (GPP) ?

A

the rate of production of chemical energy in organic chemicals by photosynthesis (kJ m-2 year-1).

79
Q

What is net primary productivity? (NPP)

A

gross primary productivity minus the energy used up by the producers in respiration in a year. It is therefore the energy in the plants biomass.

80
Q

What does NPP represent?

A

the potential food energy available to heterotrophs in ecosystems.
l

81
Q

on average what is gpp and npp?

A

l GPP is 0.2% of incident global sunlight energy and NPP is 0.1%.

82
Q

What does NPP also represent?

A

represents the potential food/chemical energy available to heterotrophs in ecosystems

83
Q

How is NPP calculated?

A

Net primary productivity = GPP – Respiration

84
Q

Why don’t consumers take all of this potential energy? (NPP)

A

Some parts of a plant are inedible – roots and bark.
Some parts of a plant are indigestible – cellulose

85
Q

What is primary productivity all about?

A

producers

86
Q

What does the gpp in the npp calculation represent?

A

the rate at which products of photosynthesis are formed (glucose)

87
Q

what does npp represent in the npp calculation?

A

energy left over after respiration is used to make make plant dry carbon biomass (stored as starch /lipids or is used to make new cells e.g. phospholipids/ dna/proteins)= energy available to primary consumers

88
Q

What does respiration represent in the npp equation?

A

A large amount of glucose is used up in respiration by plant/ energy lost in heat

89
Q

What is biological productivity?

A

the rate at which biomass accumulates in an ecosystem

90
Q

what is biomass?

A

the dry weight of organic matter comprising a group of organisms in a particular habitat

91
Q

what is npp (in terms of rate)?

A

rate at which producers convert energy into biomass.

92
Q

What is the NSP equation?

A

NSP = GSP - R
NSP= (ingested- (Egested + excreted))- respiration

93
Q

What is nsp in the nsp equation?

A

new biomass in consumer (dry mass of carbon molecules =new cells/tissues)

94
Q

what is gsp in the nsp equation?

A

food consumed - fibre/cellulose not digested/absorbed

95
Q

what is r in the nsp equation?

A

glucose used up in respiration = energy lost as heat

96
Q

What do ecologists do to find the dry mass of plants?

A

dry samples in an oven at 65°C.

97
Q

how would the ecologists be confident that all the water had been removed but none of the organic matter had been lost? (dry samples in an oven)

A

Repeat until constant mass recorded and ensure there is no burning or combustion

98
Q

What is secondary productivity?

A

the rate at which consumers accumulate energy from assimilated food in biomass in their cells or tissues.

99
Q

What causes the loss from the food chain at each level as energy is passed along it from one trophic level to another?

A

Energy in egested molecules – mostly cellulose.
Energy lost as heat generated in respiration.
Energy remains in inedible parts of animals e.g. horns, bones and fur.

100
Q

why do carnivores have more efficient every conversion that herbivores?

A

Protein is more rapidly and easily digested than cellulose.
A lot of cellulose is lost in the faeces of a herbivore.

101
Q

why do farmers keep animals in barns during the winter?

A

They won’t have to use as much energy maintaining their body temperature, so more energy is available to produce biomass (meat). (endothermic metabolism)

102
Q

What is gross ecological efficiency?

A

a measure of how much energy is transferred from one trophic level to the next.

103
Q

What is the GEE equation?

A

GEE= energy in trophic level/energy in previous trophic level x 100

104
Q

what are fish’s blood like?

A

ectothermic (cold blooded)- don’t need heat from respiration

105
Q

What are the values for GEE in different ecosystems?

A

•They are often around 10%.
•Oceanic food chains can have high values, around 40%.
•Food chains involving birds and mammals may be as low as 1%.

106
Q

What is the difference in the values for GEE because of?

A

-many aquatic organisms don’t regulate their body temperature and so save a lot of energy.
-birds and mammals maintain a high body temperature (endothermic) and this uses up a lot of energy and is therefore less efficient

107
Q

what are the units for npp?

A

KJ-2 . year-1

108
Q

What is the equation for photosynthetic energy?

A

energy incorporated into photosynthetic products/total light energy falling on the plant

109
Q

What causes ecosystems to change over time?

A

Interactions of the organisms and their environment

110
Q

What are nitrate ions needed for?

A

synthesis of DNA, RNA, amino acids, protein

111
Q

What is primary succession?

A

The introduction of plants/animals into areas that have not previously supported a community e.g. bare rock.

112
Q

What is a sere?

A

Each stage during succession when particular communities dominate

113
Q

What is the process of primary succession into a climax community?

A

-Pioneer species are the first organisms to colonise the rock e.g. lichens.
-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 of time trees and woodlands become established.
-This results in a stable, long-lived community known as the climax community.

114
Q

What are the features of a climax community?

A

-doesn’t change further over time (succession has finished)
-community in equilibrium consisting of a stable community of dominant species

115
Q

What is Secondary Succession?

A

The reintroduction of organisms into a bare habitat previously occupied by plants and animals that may have been damaged by fire or tree felling.

116
Q

What is succession affected by?

A

migration
competition
facilitation

117
Q

What is migration in succession?

A
  • the arrival of spores, seeds and animals is vital for succession to progress. Immigrating non-native species may spread themselves widely, altering communities.
118
Q

What is facilitation in succession?

A
  • positive interactions between species that become increasingly significant as succession progresses.
    -Mutualism is an interaction between two different species that is beneficial to both, e.g. flowering plants and their pollinators.
119
Q

What is competition in succession?

A

interspecific competition

120
Q

As succession occurs, what happens to species diversity?

A

Increases

121
Q

How do primary and secondary succession differ?

A

Secondary succession is much more rapid as soil is already present.

122
Q

What are factors that assist in the colonisation of a habitat?

A

-The seeds previously dispersed by flowering plants and spores from fungi may remain in the soil and begin to germinate.
-Migrating animals produce droppings. This improves nitrate levels in the soil.

123
Q

What can human interference affect and what are the examples?

A

affect natural development of the climax community during succession e.g.
•Grazing
•Moorland
•Farming
•Industry
•Urban Development

124
Q

What is grazing?

A

Grazing: livestock such as sheep eat the grasses and other plants.

125
Q

What is moorland management?

A

•Moorland management: heather colonisation is controlled by burning.

126
Q

What does farming do?

A

ploughing and growth of crops by monoculture stops trees and shrubs from getting established.

127
Q

What does deforestation do?

A

trees are cut down and this can cause erosion of soil

128
Q

What is industry?

A

coal mining and quarrying of stone.

129
Q

What is urban development?

A

building of new roads and buildings

130
Q

What can pyramids be used to do?

A

give a quantitative account of the feeding relationships in a community

131
Q

What does a pyramid of energy show?

A

quantity of energy transferred from one trophic level to another per unit area/volume per unit time. e.g. kilo joules per square metre of an ecosystem in one year (kJ/m2/yr).

132
Q

How is energy lost at each trophic level?

A

Heat through respiration, excretion, egestion

133
Q

Why can a pyramid of energy never be inverted?

A

Energy is always lost from one trophic level to the next, cannot be produced

134
Q

What aspect of a pyramid of energy overcomes problems associated with pyramids of numbers and biomass?

A

never inverted

135
Q

What is the definition of ecology ?

A

The study of living organisms within a habitat and their interactions with both biotic and abiotic factors.

136
Q

What is the detention of niche?

A

The specific role and position a species plays within a particular ecosystem.

137
Q

What is random sampling?

A

Method of sampling when abiotic factors are uniform

A-level biology component 1 (+immunology) (7 decks)

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