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Biology🧬 > Populations And Ecosystems🌍 > Flashcards

Populations And Ecosystems🌍 Flashcards

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1
Q

What is a fugitive species?

A
  • Large capacity for reproduction and dispersal
  • Pioneer species
  • Opportunistic - avoids competition
  • Continually invade new environments to survive
  • Boom-bust population growth
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2
Q

What is an equilibrium species?

A
  • Competition in habitat controls population size and drives adaptations
  • Fewer offspring - survive longer
  • Sigmoid growth curve
  • Populations stabilises
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3
Q

What is a pioneer species?

A
  • The first to colonise previously biodiverse ecosystems

* Able to withstand harsh conditions

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4
Q

Examples of density independent factors

A
  • Favourable light (increase pop)
  • Plentiful space (increase pop)
  • Sudden change of abiotic conditions (decrease pop)
  • Too little light (decrease pop)
  • Limited space (decrease pop)
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5
Q

Example of density dependent factors

A
  • Less parasitism (increase pop)
  • Inadequate food supply (decrease pop)
  • Disease as pathogens (decrease pop)
  • Increased predation (decrease pop)
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6
Q

What is an ecosystem?

A

A community of organisms that interact with each other and the abiotic factors of their habitat

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7
Q

What is a population?

A

A group of interbreeding individuals of the same species found in a particular habitat at a particular time

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8
Q

What is a community?

A

Populations of different species living in a particular habitat at a particular time

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9
Q

What is a habitat?

A

The physical environment where a particular population or community is found

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10
Q

What is an environment?

A

The set of external conditions (biotic and abiotic) that surround an organism

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11
Q

What is an ecological niche?

A

The role and position of a species in its environment, including all interactions/adaptations with the biotic and abiotic factors

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12
Q

What is an invasive species?

A
  • Species introduced to an area

* Can outcompete other species

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13
Q

Can ecologically similar species coexist?

A

Yes, if they have slightly different niches

- there will be more of one species than the other

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14
Q

What is the lag phase? (Phase 1)

A

•Slow increase to number in the population

  • adjusting to new environment
  • time needed to produce enzymes and switch on genes
  • few reproducing individuals
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15
Q

What is the exponential growth/log phase? (Phase 2)

A

•Population grows at biotic potential (max rate)
•No limiting factors
-plentiful nutrients
-low concentration of waste products

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16
Q

What is environmental resistance? (Phase 3)

A

•Environmental factors slow population growth
•Limiting factors inhibit further growth
-low food
-overcrowding
-competition
-toxic waste accumulation

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17
Q

What is the stationary phase? (Phase 4)

A
  • Carrying capacity is reached
  • Equilibrium is established
  • Death rate = birth rate
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18
Q

What is carrying capacity?

A

The maximum population size that an environment can support indefinitely

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19
Q

Boom and bust curve

A

•Sometimes, a population increases so rapidly during the exponential growth phase that it overshoots the carrying capacity
•As environment cannot support population, a population crash usually follows
•Overpopulation can damage the environment
-new, lower carrying capacity

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20
Q

Abiotic factors that increase/decrease a population size

A
  • Space
  • Water supply
  • Light intensity
  • Stability of abiotic factors
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21
Q

Biotic factors that increase/decrease a population size

A
  • Food supply
  • Disease resistance
  • Number of predators/ability to avoid
  • Reproductive rate
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22
Q

What are density dependent factors?

A

•As a population density increases, these factors have stronger effects
-affecting a larger proportion of the population
•Involves intraspecific competition
•Usually biotic factors

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23
Q

What are density independent factors?

A
  • Affect the same proportion of the population, no matter what density
  • Usually abiotic factors
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24
Q

How can abiotic factors indirectly affect organisms?

A

By affecting their food source

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25
Q

What is immigration?

A

Amount of movement into a population

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26
Q

What is emigration?

A

Amount of movement out of a population

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27
Q

What is competition?

A

When two or more individuals have to share resources in short supply
-one may be outcompeted

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28
Q

What is interspecific competition?

A

Competition between members of two different species

-predator-prey

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29
Q

What is intraspecific competition?

A 
Competition between members of the same species 
E.g.
-mate selection 
-food sources
-territory 
-nest sites
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30
Q

What is the competitive exclusion principle?

A
  • When the ecological niches of two species are so similar that they compete for the same similar resources
  • They cannot coexist together indefinitely
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31
Q

What is a realised niche?

A

Restricted by the presence of a competitor

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32
Q

What is a fundamental niche?

A

The larger, potential niche that would occur without the competitor

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33
Q

What is resource partitioning?

A

The division of environmental resources between two organisms/species

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34
Q

What is ecological succession?

A

The gradual change from one community type to another (structure and species composition)

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35
Q

What is primary succession?

A
  • Occurs in any newly formed area where no life previously existed
  • Is a slow process
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36
Q

What is secondary succession?

A
  • Occurs in areas where life is already present but has been altered in some way
  • The species recolonise the area
  • Faster process
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37
Q

Why is secondary succession faster?

A
  • The soil is already deep and rich in nutrients
  • There may be seeds/bulbs already in the soil
  • Pioneer stages are not needed
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38
Q

Explain the process of succession?

A

•Pioneer species colonise the area
-adapted to survive and reproduce in harsh conditions
•Pioneer species stabilise the substrate and alter the abiotic conditions
-erode rock, add nutrients/inorganic matter and upon death add organic matter to the soil
•Due to change in abiotic conditions, new species have advantages that allow them to outcompete the pioneer species (C.E principle)
•Process continues - as one community alters the abiotic environment, new species will migrate and outcompete those species, allowing a new community to take over
•Succession progresses through various seral stages before reaching a climax community

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39
Q

What is a climax community?

A
  • The final stage of succession
  • Stable
  • Long-living plants
  • Complex food webs
  • High biodiversity
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40
Q

What are seral stages?

A

The different stages in succession when particular communities dominate

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41
Q

How do the organisms differ from one stage to another?

A

Types of animals and plants will differ from one seral stage to another

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42
Q

How does succession affect biomass?

A
  • An increase in biomass occurs with succession
  • As soil becomes deeper and more rich with organic debris and nutrients, it an support a larger number of plants and animals
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43
Q

How does succession affect biodiversity?

A

An increase in plant and animal diversity

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44
Q

Why does a diverse plant community increase animal diversity?

A
  • It provides more resources/food/habitat

* It provides more ecological niches

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45
Q

What is climatic climax?

A

When a climax community is reached, it is in equilibrium with the climatic conditions

46
Q

Interference with a climatic climax

A

•Humans and other animals can interfere
-a different equilibrium, known as the biotic climax may be reached
•Management of land by intensive grazing, seasonal mowing, burning or weed spreading are all examples of this climax
-often referred to as a deflected climax

47
Q

What is deflected climax?

A

Plant succession deviating from its normal course due to direct or indirect human intervention

48
Q

What does succession lead to?

A
  • Increase in number of available niches
  • Increase in species diversity
  • Increase stability of ecosystem
49
Q

What’s a random sample?

A
  • Random numbers are generated to produce coordinates
  • A tape measure is used to create a sample area
  • A sample is taken at the coordinates
50
Q

What’s a systematic sample?

A

Sampling points are taken at regular intervals

51
Q

Why are transects useful?

A

Record changes in abundance and distribution of a species where a transition occurs

52
Q

What is a line transect?

A

Tape is put across the sample area and any species that touch it are recorded

53
Q

What is a belt transect?

A

Transect is put along tape at intervals and the species found within it are estimated

54
Q

What is a frame quadrat?

A
  • Laid down at sampling points within a sample area or at points along a transect
  • Organisms are estimated (often as % cover)
55
Q

What is a point quadrat?

A
  • 10 pins dropped through frame onto vegetation

* As each pin touches a plant of a particular species, a hit is recorded

56
Q

What is a problem with random sampling?

A

It may miss areas, so some species may be missed

-biodiversity is underestimated

57
Q

What are the different measures of abundance?

A

•Density
-mean number of individuals per unit area
•Frequency
-number/percentage of sampling units in which a particular species occurs
•Biomass (standing crop)
-dry weight of plants or animals in a certain area at a certain time
•Percentage cover
-% of ground covered by a species within the sampling unit

58
Q

Simpson’s diversity index

A

D=1-(En(n-1)/N(N-1))
•D=diversity
•n=total number of organisms of a particular species
•N=total number of organisms of all species

59
Q

Why take a sample?

A

•Time and cost
•Provides estimate
•More samples=more reliable mean and anomalies have less effect
-sample is more representative
•Large sample size minimised possibility that the sample may be unrepresentative
•Random to avoid bias

60
Q

What is a food chain?

A
  • Shows a sequence of organisms in which each organism is the food of the next one in the chain
  • Show direction of flow of energy
  • Each organism represents a trophic level
61
Q

What can food chains show?

A

How substances such as pesticides/insecticides are transferred in an ecosystem

62
Q

Limitations of a food chain

A
  • Do not reflect the complex feeding relationships that exist in most ecosystems
  • Give false impression that each organism only feeds on one other type of organism
63
Q

What is a food web?

A

Interconnected food chains

64
Q

Limitations of a food web

A

•Relationships can be complex
-related species with similar diets are grouped together
•Only a part of the ecosystem is usually shown
•Doesn’t say how much energy flows from one part of an ecosystem to another

65
Q

What is a pyramid of number?

A
  • Shows quantitative relationships between organisms at each trophic level
  • Represents the total number of organisms at each trophic level in a food chain at a given point in time
  • May be inverted
66
Q

What is a pyramid of biomass?

A
  • Takes into account the difference in size between organisms
  • Counts the number of individuals presents (in each trophic level) in a given area and multiplying it by the average mass of these individuals
  • Can be inverted
67
Q

What is biomass measured in?

A

kgm-2

68
Q

Why don’t pyramids of biomass give a meaningful comparison between masses of the same trophic level in different ecosystems/different trophic level, same ecosystem?

A
  • Usually refers to the standing crop

* Biomass of populations of small organisms may fluctuate throughout the year

69
Q

What is standing crop?

A

Amount of dry mass measured at any one time

-have to dry out organism or use estimate

70
Q

What is a pyramid of energy?

A
  • Represent a flow of energy through each trophic level in an ecosystem during a fixed period of time (kJm-2y-1)
  • Allow comparisons between the productivities of the trophic levels because a time period is involved
  • Never inverted
71
Q

How can energy flow be presented?

A
  • Pyramid of energy

* Energy flow diagram

72
Q

Efficiency of primary production

A
  • Proportion of solar energy converted into the chemical energy of plant tissues is low
  • GPP
  • NPP
73
Q

What is gross primary production? (GPP)

A

The total rate autotrophs synthesise organic material

74
Q

What is net primary production? (NPP)

A

The rate at which autotrophs store organic material as new plant tissue (available for primary consumers)

75
Q

Equation for NPP

A

NPP = GPP - energy lost during respiration

76
Q

Efficiency equation

A 
Efficiency = 
energy/biomass after transfer
/
energy or biomass before
x100
77
Q

Why isn’t the majority of light converted?

A

•Some light is reflected off the plant surface
•Some light fails to strike a chlorophyll molecule
-transmitted through the leaf
•Some light is of the wrong wavelength for photosynthesis

78
Q

What is secondary production?

A

•The rate at which energy from one trophic level is used to make new animal cells/tissue
•Approx 10% of energy passes between levels
-number of trophic levels is usually limited to 4/5 in an ecosystem

79
Q

What factors contribute to a loss of energy in a food chain?

A
  • Parts of the organism are not eaten
  • Parts of the organism are not digested
  • Energy is lost as heat to the surroundings during cellular respiration
80
Q

How to use log scales for drawing population graphs

A
  • log10(—) on the calculator
  • Find for all values - put values onto a graph
  • It tells you the number of times that 10 has been multiplied by itself to get a number
81
Q

How to read off a log graph

A
  • Press shift
  • Press log
  • Add number
82
Q

What is nitrogen used for by plants?

A
  • Produce amino acids
  • Produce DNA
  • Produce RNA
83
Q

Alternative ways nitrogen fixation can occur

A

•A little can occur during thunderstorms
-lightning provides energy to oxidise nitrogen to nitrogen oxides
•Artificially by industry
-produces nitrogen fertilisers

84
Q

What mostly carries out nitrogen fixation?

A

•Nitrogen fixing bacteria - nitrogenase
•Rhizobium
-mutualistic bacteria found in root nodules of leguminous plants
-plants obtain source of nitrogen, while bacterium gains a home and constant source of carbohydrates
•Aztobacter
-found living free in the soil

85
Q

How does ammonification/putrefaction occur?

A

•Ammonia is produced from organic nitrogen-containing compounds
-found in faeces, urine and dead organisms
•Carried out by saprophytic bacteria and fungi
-decompose/metabolise compounds
-release ammonium ions

86
Q

How does nitrification occur?

A 
•Under aerobic conditions
•Nitrifying bacteria (chemoautrophs)
•Nitrosomonas convert:
-ammonia to nitrites 
•Nitrobacter convert:
-nitrites to nitrates
87
Q

How does denitrification occur?

A
  • Denitrifying bacteria pseudomonas convert nitrates and ammonium ions into atmospheric nitrogen
  • Occurs in anaerobic conditions (waterlogged soils)
  • Removes nitrogen from ecosystems
88
Q

What is assimilation?

A

When an organism absorbs small soluble products and use them to synthesise it’s own organic molecules

89
Q

Equation of nitrogen fixation

A

Nitrogen + hydrogen
——>
Ammonia

90
Q 
Molecular formulae for:
•Atmospheric nitrogen
•Ammonium ion
•Nitrites
•Nitrates
A
  • N2
  • NH+4
  • NO-2
  • NO-3
91
Q

What is the main source of carbon for terrestrial and aquatic organisms respectively?

A

•Terrestrial: carbon dioxide
•Aquatic: hydrogencarbonate ions formed from dissolved carbon dioxide
-as CO2 conc increases in atmosphere, more becomes dissolved in water

92
Q

How is CO2 fixed?

A
  • Photosynthesis by photoautotrophs - convert it to complex organic molecules
  • CO2 is then returned to oceans and atmosphere by respiration
  • Carbon is also released during decomposition
93
Q

How is CO2 released into the atmosphere?

A
  • Combustion of fossil fuels

* Deforestation

94
Q

Effects of global warming

A
  • Altered rainfall patterns
  • Desertification
  • Rise in sea levels
  • Floods
  • Forest fires
95
Q

Effects of climate change

A
  • Affects distribution of species
  • Can lead to extinction of species
  • Can affect crop yields (can improve)
96
Q

What is a carbon footprint?

A

Individual contribution to CO2 emissions over a year period

97
Q

Effects of global warming on agriculture

A
  • Increased frequency of weather extremes
  • Loss of biodiversity
  • Loss of fertile coastal lands caused by rising sea levels
  • Dramatic changes in distribution and abundance of fish
  • Increase in incidence of pests and vector-borne diseases
  • More unpredictable farming conditions in tropical areas
98
Q

What is biological oxygen demand (BOD)?

A
  • Adding organic material to water stimulates the growth of microorganisms which feed on the material
  • As the density of microorganisms increases, their demand for oxygen also rises
  • mgdm3
99
Q

What is leaching?

A

When nitrates and phosphates enter water
-by sewage
-by agricultural runoff
Leads to eutrophication

100
Q

Process of eutrophication

A

•Nitrates enter water by leaching
•Causes algal blooms which:
-smother plants
-reduce light intensity (plants are unable to photosynthesise)
-produce toxins which kill organisms
•Algae and other organisms die and are decomposed by saprophytic bacteria
•Deoxygenation occurs due to bacteria multiplying
-causes more aerobic organisms to die

101
Q

Why might a farmer plough their field?

A
  • Adds oxygen to soil
  • Provides aerobic conditions
  • Aztobacter carry out nitrogen fixation
  • Adds ammonium ions to the soil
102
Q

Why might a farmer rotate crops with legumes?

A
  • Leguminous plants contain Rhizobium in their root nodules which carry out nitrogen fixation
  • Ammonium is added to the soil
103
Q

Why might a farmer add manure to the soil?

A
  • Manure is decomposed by saprophytes
  • Ammonification occurs
  • Ammonium is added to the soil
104
Q

Why might a farmer have good drainage?

A

•Waterlogged soil provides anaerobic conditions

  • prevents nitrogen fixation by Aztobacter
  • encourages denitrification which adds N2 to the atmosphere
105
Q

Equation for population growth

A

Population growth=
Births + immigration
-
Deaths + emigration

106
Q

What type of competition causes succession?

A

Interspecific

-plants competing for the same resources

107
Q

What is the benefit of intensive farming?

A

•Animals are kept indoors in high densities under temperature controlled conditions
•Increases efficiency of meat production (secondary productivity)
-reduces respiratory losses due to movement and regulation of body temperature

108
Q

Function of leghaemoglobin

A
  • High affinity for oxygen - binds with lots of oxygen
  • Lowers oxygen levels in the root nodules
  • Can fix atmospheric nitrogen without oxygen
109
Q

GPP = ?

A

Solar energy - energy not used

110
Q

NPP = ?

A

GPP - respiration

Biology🧬 (24 decks)

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