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A level Biology > Unit 3.5 - Population and Ecosystems > Flashcards

Unit 3.5 - Population and Ecosystems Flashcards

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1
Q

Habitat

A

A place where an organism lives

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2
Q

Community

A

All the different species in a habitat

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3
Q

Environment

A

The abiotic factors in a habitat

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4
Q

Population

A

The number of individuals of a particular species in a particular time and place, able to interbreed

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5
Q

Species

A

Organisms that can interbreed to produce fertile offspring

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6
Q

Ecosystem

A

All the biotic and abiotic factors in a region and how they interact

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7
Q

Niche

A

The exact role an organism plays in a habitat. Can be thought of as an “n-dimensional hyper volume”

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8
Q

Why is a niche known as an n-dimensional hyper volume?

A

With all factors acting as a dimension, it creates a niche that only one species can fill

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9
Q

Fundamental niche

A

The species could occupy this niche

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10
Q

Realised niche

A

Given up what is already within another species niche

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11
Q

Competitive exclusion principle

A

Two species occupying the same niche can’t coexist at the same time in the same habitat

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12
Q

What does the competitive exclusion principle lead to?

A

No two niches are the same
Complete competitors can’t exist, since the niche would be taken over

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13
Q

Why can’t complete competitors exist?

A

The niche would be taken over, and no two niches are the same

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14
Q

Are P.Aurelia and P.candatum predator and pray?

A

No, they compete for the same food source

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15
Q

Graphs of P.Aurelia and P.candatum individually

A

One-step grown curves (S-shaped)

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16
Q

Another word for S-shaped graphs

A

One-step growth curves

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17
Q

What happens when P.Aurelia and P.candatum are grown together and why?

A

P.Aurelia is outcompeting, so P.candatum is pushed to of the niche, and the population density of P.Aurelia increases whilst the population density of P.candatum decreases

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18
Q

What are P.Aurelia and P.caudatum examples of?

A

Paramecium

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19
Q

Factors affecting population size

A

Birth rare
Death rate
Immigration
Emigration

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20
Q

Birth rate

A

The number of new individuals produced by sexual or asexual reproduction per unit time

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21
Q

Death rate

A

The number of individuals dying per unit time

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22
Q

Immigration

A

New individuals joining a population

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23
Q

Emigration

A

Individuals leaving a population

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24
Q

What phase do we need to include in the definitions for birth rate and death rate and why?

A

“Per unit time” since they’re rates

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25
Q

An increase in what causes an increase in the population size?

A

Birth rate and immigration

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26
Q

An increase in what causes a decrease in population size?

A

Death rate and emigration

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27
Q

How can we differentiate between species in this unit?

A

Depending on the way they colonise an area

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28
Q

Describe fugitive species

A

Cannot tolerate competition
To increase in numbers —> reproduce rapidly and have effective dispersal (spreading) mechanisms
Are able to invade new environments rapidly
E.g - algae and weeds

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29
Q

Examples of fugitive species

A

Algae and weeds

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30
Q

Species that cannot tolerate competition

A

Fugitive species

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31
Q

Equilibrium species

A

Control their population by competition within a stable habitat

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32
Q

Usual pattern of growth of equilibrium species

A

Sigmoid (s-shaped) curve called a one step growth curve

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33
Q

What type of species follow a one-step growth curve pattern of growth?

A

Equilibrium species

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34
Q

One-step growth curve

A

Sigmoid (s-shaped) curve

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35
Q

Examples of equilibrium species

A

Bacteria and rabbits

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36
Q

What do we need to do when describing, for example, rabbit and bacteria populations?

A

Use the correct terms for the specific scenario
Bacteria —> “cell division”, “cell death”
Rabbits —> “rate of birth”, “rate of death”

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37
Q

What happens during the exponential (log) phase?

A

The number of cells double per unit time

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38
Q

What fact do we use for any calculations on the number of cells produced during the exponential phase?

A

The fact that the number of cells double per unit time during the exponential (log) phase

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39
Q

How do we achieve the full amount of cells during the exponential (log) phase?

A

Would need…
Ideal conditions
To assume that none die
A huge amount of nutrients

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40
Q

Biotic factors

A

Factors that are living parts of the environment of an organism

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41
Q

Examples of biotic factors

A

Predation, parasitism, disease, intra-specific and inter-specific competition

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42
Q

What are intra-specific and inter-specific competition examples of?

A

Biotic factors

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43
Q

Intra-specific competition

A

During the stationary phase of the population growth:
Competition between individuals of the same species for the same food
(e.g - just rabbits for grass)

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44
Q

Inter-specific competition

A

Other species competing for the same food course (e.g - rabbits and sheep for grass)

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45
Q

Abiotic factors

A

Are some part of the organisms environment that is non-living

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46
Q

Examples of abiotic factors

A

Air temperature, oxygen availability, rainfall, light availability

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47
Q

What do density dependent factors tend to be?

A

Biotic factors

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48
Q

What do density independent factors tend to be?

A

Abiotic factors

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49
Q

Density dependent factors

A

Has an increasing effect on the rate of population growth with increasing population density

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50
Q

Explain why bacteria is a entity dependent factor

A

Disease has a greater effect on a larger population

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51
Q

Examples of density dependent factors

A

Predators, parasites, pathogens
Competition: food, mates, nesting sites

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52
Q

Density independent factors

A

Have the same effect on the rate of population growth regardless of population density

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53
Q

Examples of density independent factors

A

Wild fires, floods, climate change, sunlight (energy), temperature, rainfall

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54
Q

Carrying capacity

A

The maximum population size of a species that an environment can sustain

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55
Q

What’s important to notice about the carrying capacity definition?

A

Not have, but sustain over an extended period of time

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56
Q

What can carrying capacity be compared to?

A

The “stationary phase” for bacteria is the carrying capacity of a habitat in nature

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57
Q

What happens around the carrying capacity?

A

There’s fluctuation in the number of the population over time.
Numbers fluctuate about the carrying capacity.

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58
Q

Where do population numbers fluctuate about?

A

The carrying capacity

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59
Q

When would the carrying capacity of an environment decrease and why?

A

When a predator or parasite or disease is present
The environment can’t sustain the same numbers of the organism

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60
Q

What does introducing a predator, parasite or disease to an environment do to the carrying capacity and why?

A

Carrying capacity decreases
The environment can’t sustain the same numbers of the organism

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61
Q

Environmental resistance

A

Refers to environmental factors that slow down population growth

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62
Q

What may environmental resistance be?

A

Biotic or abiotic

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63
Q

Example of environmental resistance + why

A

A predator
Increases the environmental resistance = population lowers

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64
Q

Describe the graph comparing prey and predators populations and explain when this happens

A

If a predator is depending on this prey as its food source, the predator curve “lags” behind the prey curve

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65
Q

Explain why the predator curve lags behind the prey curve on the graph comparing the two

A

-predator number are low = less pressure on prey = numbers increase
-more prey for predators = numbers increase
-puts pressure on prey population in turn = more prey eaten by predators
-less food for the predator = numbers decrease
And repeat

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66
Q

Famous example of a predator/prey relationship

A

Lynx and snowshoe hare

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67
Q

Describe the snowshoe hare over the seasons

A

Brown in summer
White in winter

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68
Q

How much data needs to be collected to make a graph to compare prey and predators populations?

A

Decades of data

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69
Q

Describe the predator/prey relationship between the lung and the snowshoe hare

A

-when the prey population is large, intraspecific competition in the predator population is low =population grows
-this places more pressure on the prey population, which declines as a consequence
- this leads to greater intraspecific competition for the predators and their population declines, allowing the prey population to recover
-the cycle continues

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70
Q

What are the lynx and snowshoe hare essentially achieving with each other and how?

A

Sustaining each other over time
Maintaining an equilibrium between them

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71
Q

When is intraspecific competition in a predator low?

A

When the prey population is large

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72
Q

When is the intraspecific competition of predators large?

A

When the prey population is low

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73
Q

What happens to the competition of predators when the prey population is large?

A

Intraspecific competition is low

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74
Q

What happens to the competition of predators when the prey population is low?

A

Intraspecific competition is high

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75
Q

Name an animal population counting method

A

Capture, mark, re-capture

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76
Q

What is the capture, mark, re-capture method used for?

A

To estimate the size of populations of motile animals (moving animals)

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77
Q

Capture, mark, re-capture method

A
  1. An initial sample of the population in question is captured
  2. These individuals are then marked and released back into the wild, and the number caught is recorded
    (The mark must be all weather resistant)
  3. These marked individuals are released and are left for a period of time to allow them to randomly disperse throughout the habitat
  4. Then, a second sample is captured
  5. The total number captured in the second sample, and the number recaptured with the marking is recorded
  6. The size of the population is then estimated on the principle that the proportion marked in the second sample equals the portion of marked individuals in the population as a whole
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78
Q

How do we make the capture, mark, re-capture method more reliable?

A

Repeat

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79
Q

What does repeating an experiment do?

A

Makes it more reliable

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80
Q

Lincoln index equation and meanings

A

N = n1 x n2/m

N = total population size of animal of interest in sthe study ite
n1 = number of animals captured on the first day
n2 = number of animals captured on the second day
m = number of marked animals in the sample recaptured on the second day

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81
Q

Which principle does the capture, mark, re-capture method rely on?

A

That the proportion marked in the second sample equals the proportion of marked individuals in the population as a whole

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82
Q

Assumptions made using the capture, mark, re-capture method

A
  1. The organisms that have been marked mix randomly within the population
  2. Enough time is given for the marked individuals to mix randomly with the rest of the population
  3. The movement of the population as a whole is limited geographically
  4. Organisms are spread evenly within its geographical range
  5. Changes in population size due to birth, death, immigration and emigration are minimal
  6. Marking dos not make them more susceptible to predators or harm them in any way or make them more likely to be recaptured
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83
Q

How do we do the capture, mark, re-capture method with particularly big species?

A

Generally use features they already have to identify them instead of marking them

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84
Q

Study of the energy flow through ecosystems

A

Energetics

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85
Q

Energetics

A

Study of the energy flow through ecosystems

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86
Q

Ecosystem

A

A characteristic community of interdependent species and their habitat

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87
Q

What can an ecosystem be described as?

A

Dynamic (changes over time)

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88
Q

What is an ecosystem compromised of?

A

Living (biotic) and non-living (abiotic) elements

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89
Q

What does an arrow in a food web represent?

A

“Is eaten by”, or more instantly, the transfer of energy

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90
Q

What do food webs prove?

A

That ecological communities are dependent on each other for food

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91
Q

Energy source of most ecosystems

A

The sun

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92
Q

What do some ecosystems use as their energy source instead of the sun?

A

Chemicals

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93
Q

Name an ecosystem that uses chemicals instead of the sun as its energy source and why

A

Thermal vents, no sunlight

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94
Q

What type of organisms use chemicals as their energy source and for which process is this?

A

Used by chemosynthetic organisms for chemosynthesis

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95
Q

What does each food web start with?

A

Autotrophs (the producers)

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96
Q

What do autotrophs do?

A

Covert light energy into chemical energy to produce complex organic compounds using carbon from simple substances such as CO2

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97
Q

What does each food chain rely upon?

A

Autotrophs (photosynthetic organisms)

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98
Q

What is the energy produced by autotrophs then available for?

A

Heterotrophs

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99
Q

What do heterotrophs do?

A

Cannot procure their own complex organic molecules
Feed on autotrophs and each other

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100
Q

What is the final stage of a food chain?

A

The apex predator

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101
Q

What is the maximum number of steps from autotrophs to heterotrophs in a food chain??

A

About 6 steps

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102
Q

Why is the maximum number of steps from autotrophs to heterotrophs in a food chain never more than about 6 steps?

A

Energy losses when going from one stage to the next
The chain is unable to maintain another level beyond the apex predator

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103
Q

What are the names of the different stages in a food chain?

A

Tropic levels

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104
Q

Names for the organisms in a food chain in order

A

Producer
Primary consumer
Secondary consumer
Tertiary consumer
(e.t.c)

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105
Q

Producers trophic level

A

1

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106
Q

Producers

A

Autotrophic organisms (plants and algae) which absorb light energy to covert simple inorganic compounds into more complex organic compounds such as carbohydrates

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107
Q

Consumers

A

Heterotrophic organisms which cannot fix carbon from inorganic compounds like the producers do —> they must ingest it or absorb organic carbon from other organisms

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108
Q

Herbivores trophic level

A

2

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109
Q

Herbivores

A

Primary consumers, animals which feed on organic matter produced by the producers

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110
Q

Carnivores

A

Feed on other animals at lower trophic levels

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111
Q

Trophic level

A

An organism’s position within a food chain (steps in the food chain)

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112
Q

Detritivores examples

A

Earthworms, woodlice, maggots

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113
Q

Decomposers examples

A

Bacteria, fungi

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114
Q

Detritivores

A

Feed on dead organic matter (e.g - plants and fungi)

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115
Q

Decomposers

A

Break down organic compounds into simpler inorganic compounds which are soluble and can be absorbed by plant roots

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116
Q

Explain which elements can become part of the Decomposer system in a simple foo chain

A

Some grass dies, is available for detritivores and decomposers
Animal waste becomes part of the decomposers system

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117
Q

Trophic efficiency

A

The percentage of energy available at one trophic level which is transferred to the next trophic level to form new biomass

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118
Q

Describe the energy that’s passed from one trophic level to the next in a food chain

A

Only a small % of energy

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119
Q

Why is it only a mall % of energy that’s available to be passed on from one trophic level to the next?

A

Most of it is lost due to heat, waste products and uneaten parts

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120
Q

Ways energy is lost at each trophic level

A

Heat
Waste products
Uneaten parts

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121
Q

Name the different ways or representing the energy flow in food chains

A

Graphs
Pyramids
Energy flow diagrams

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122
Q

Why is the trophic efficiency so low between trophic levels 1 and 2 compared to between trophic levels 2 and 3?

A

Plants contain a lot of indigestible material

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123
Q

Name some indigestible materials in plants

A

Lignin in wood
Cellulose in cell walls

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124
Q

What do animals do with the parts of a plant that they can’t get the nutrients from?

A

Pass them through their systems, unabsorbed

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125
Q

Compare the % indigestible material in an animal vs a plant

A

The % of indigestible material in an animal is much lower than in a plant

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126
Q

Name some indigestible parts of an animal

A

Fur, nails

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127
Q

Which type of Pyramid to represent energy flow is worst?

A

Pyramid of numbers

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128
Q

Why are pyramids of numbers misleading?

A

Although 1 oak tree (for example) is shown, the amount of energy in it is massive, but it isn’t used much here. So, these pyramids don’t represent energy flow very well.

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129
Q

Biomass

A

The mass of biological/living material at each trophic level

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130
Q

What does biomass exclude and why?

A

Water since it can vary a lot in different organisms

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131
Q

How do we remove water to measure biomass and what does this do?

A

Dry them
Gives us more accurate results

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132
Q

What the most accurate pyramids to represent energy flow in a food chain?

A

Pyramid of energy

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133
Q

What does a pyramid of energy show?

A

The energy transferred from one trophic level to the next, per unit area or volume per unit time

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134
Q

What do energy flow diagrams show?

A

The energy harvested by the plant and used in photosynthesis to produce other molecules

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135
Q

Photosynthetic efficiency (PE)

A

A measure of the ability of a plant to trap light energy

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136
Q

What does photosynthetic efficiency depend on?

A

Light intensity and temperature

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137
Q

Photosynthetic efficiency equation

A

Quantity of light energy incorporated into product/quantity of light energy falling on the plant
X100

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138
Q

Products of photosynthesis

A

Glucose, carbohydrates

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139
Q

Gross primary productivity (GPP)

A

The rate at which products such as glucose are formed.
Or
The rate of production of chemical energy in organic molecules by photosynthesis in a given area, in a given time, measured in kJm^-2y-1

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140
Q

What is a large proportion of GPP used up in?

A

Respiration by the plant

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141
Q

A large proportion of what is used up in respiration by the plant?

A

Gross primary productivity (GPP)

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142
Q

Net primary productivity (NPP)

A

The quantity of GPP that is left over after respiration by the plant is accounted for. This represents the potential food available for the primary consumers.
= the energy in the plants biomass

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143
Q

Examples of potential food for primary consumers represented by the net primary productivity (NPP)

A

Fats
Glucose
proteins

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144
Q

Net primary productivity (NPP) equation

A

NPP = GPP - respiration

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145
Q

What does GPP equal?

A

NPP + respiration

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146
Q

Describe the value of gross primary production

A

Very small

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147
Q

Why is gross primary production such a small value?

A
  1. Only some wavelengths of light are absorbed by the leaf - some light will be of the wrong wavelength
  2. Lots of it is reflected off the leaf surface
  3. Lots will be transmitted through the leaf without hitting any photosynthetic parts
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148
Q

How are plants most easily sampled?

A

Using a quadrat

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149
Q

Quadrat

A

Square frames that are placed on the ground to provide a small, standard area for investigation

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150
Q

How do quadrats come?

A

In a variety of sizes (10cm, 50cm, 100cm)

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151
Q

What would 10cm quadrats be useful for?

A

Lichens on a tree trunk

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152
Q

What would a 50cm quadrat be useful for?

A

Small plants and grassland

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153
Q

What would 100cm quadrats be useful for?

A

In the wood

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154
Q

How may quadrats be subdivided?

A

Into 25 or 100 smaller squares

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155
Q

What is the smallest quadrat possible? Describe this

A

Point quadrat (pin quadrat)
A needle with the point of the needle being the actual tiny quadrat

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156
Q

Describe how we would find the best size of frame quadrat for a particular habitat

A

Need to do a preliminary experiment
“Nesting” different sized quadrats in the area to be studied and counting the number of species found
From the species-area graph, we can choose a quadrat size that is likely to catch all the species but without wasting unnecessary effort

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157
Q

2 main methods of sampling

A

Random
Systematic

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158
Q

What type of sampling do we do in an area where abiotic variables are uniform?

A

Random sampling

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159
Q

Example of an area where abiotic variables are uniform

A

An open field

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160
Q

What is used when random sampling in an open field is done?

A

A representative of the whole area, which is an “open frame quadrat”, a square frame with sides of e.g 0.5m, giving an area of 25m^2

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161
Q

Different ways in which a measurement for each species in a quadrat can be recorded after identifying the plants in the frame

A

A direct count
Percentage cover
A value using the ACFOR system

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162
Q

Explain the stages of setting up coordinates for sampling

A
  1. In a uniform grassland, set up a pair of 10m long axes at right angles to each other
  2. Use random numbers (e.g - from a random number generator) to find coordinates for the quadrat
  3. If it is difficult to count individual plants, estimate the percentage area cover
  4. Take readings at 10 pairs of random coordinates and calculate a mean for each species
  5. Compare with an area with different abiotic factors
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163
Q

How do we decide on exact coordinates of a quadrat?

A

Say our random numbers are 63 and 81 on a 10x10m axes, the coordinates are where the lines from 6.3m and 8.1m along the axes intersect

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164
Q

How can we ensure consistency with our quadrats for random sampling?

A

Always place the bottom left hand corner of the quadrat at the coordinate

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165
Q

Purpose of using a quadrat

A

Make sure that the sample size taken is constant

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166
Q

Purpose of sampling at random

A

To eliminate bias from our results for more reliable results

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167
Q

How can we get more reliable results whilst sampling?

A

Sample at Random
Take more samples

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168
Q

What does taking more samples do to our results?

A

Increases reliability

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169
Q

What do we want to ensure when doing random sampling?

A

Ensure that most factors are consistent between the 2 areas, With maybe 1 different abiotic factor to compare (e.g - same light intensities, different temperatures)

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170
Q

What do we also need to take into account when doing random samples?

A

The seasons
Ensure that the sampling for both areas is done at the same time of year

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171
Q

What are we assuming when doing sampling at random?

A

That the plants are evenly distributed in the habitat

172
Q

What must be true for plants to be evenly distributed in a habitat?

A

The environmental conditions are constant, with the same environmental gradient

173
Q

Word for environmental conditions being constant

A

Same environmental gradient

174
Q

What causes an environmental gradient?

A

A change in abiotic factor

175
Q

Why does a change in abiotic factor cause in an environment?

A

An environmental gradient

176
Q

When can’t we use random sampling?

A

When there’s a change in abiotic factor - an environmental gradient

177
Q

What type of sampling do we do in an area where there’s a change in an environmental factor?

A

Systematic sampling

178
Q

What is an environmental gradient? Give an example

A

A distinct change in an abiotic factor such as light intensity

179
Q

Give an example of light intensity changing in an environment

A

Under the shade of a tree of the edge of a woodland

180
Q

What is a transect?

A

A line along the environmental gradient

181
Q

What is used during systematic sampling on an environmental gradient?

A

A transect

182
Q

When is a transect used?

A

during systematic sampling on an environmental gradient

183
Q

How do you use a line transect?

A

Run a 20m tape measure into the wood and identify the plants touching the tape every 2m

184
Q

Why is using a transect systematic sampling?

A

We take a sample every 2m, which is in regular intervals

185
Q

How do we use a belt transect?

A

Place a 0.5m square quadrat every metre along the tape measure and estimate the density, percentage frequency or percentage area cover

186
Q

Two types of transect to use

A

Line
Belt

187
Q

What do we need to make sure we do when doing systematic sampling?

A

Make sure that the sampling area takes in all of the environmental conditions

188
Q

Example of a belt transect

A

Slope into water

189
Q

Why can’t we take a mean with systematic sampling?

A

This would assume that everything is the same all the transect

190
Q

What do we do instead of calculating a mean with systematic sampling?

A

Use a kite diagram

191
Q

Kite diagram

A

A visual representation of distribution

192
Q

What do kite diagrams show?

A

The effect of an environmental gradient

193
Q

How do we draw kite diagrams?

A

Each species have their own axes
X-axis = distance along transect
Y-axis = number of plants every 2m

194
Q

How would we show 10 plants on a kite diagram?

A

5 above, 5 below

195
Q

Succession

A

The change in structure and species composition of a community over time

196
Q

What does each stage of succession do?

A

Paves the way for the next stage

197
Q

Seral stages

A

The different stages in a succession when particular communities dominate

198
Q

Name for the different stages in a succession when particular communities dominate

A

Seral stages

199
Q

What happens to communities over time and why?

A

Change in response to changes in the environment

200
Q

When is a change in a community referred to as succession?

A

When changes are brought about by the species in the environment

201
Q

What does primary succession start from?

A

A new rock and no soil

202
Q

How could a new rock have formed for primary succession?

A

-after a volcanic eruption (lava solidifying and cooling)
-after the ice age (thick coating of ice retreated to give bear rock)

203
Q

Pioneer species

A

The first species to colonise a new environment (e.g - bare rock)

204
Q

The first species to colonise a new environment

A

Pioneer species

205
Q

What are pioneer species capable of doing? Why?

A

Growing where there’s no soil
No need for them to anchor roots in soil to absorb minerals

206
Q

What are lichens?

A

A group of symbiotic organisms (mutualistic symbiotic relationship between a fungus and an algae)

207
Q

What does a mutualistic symbiotic relationship between an algae and a fungus form?

A

Lichens

208
Q

What can lichens do?

A

Colonise bare rock

209
Q

Describe fungus

A

Heterotrophic

210
Q

Describe algae

A

Autotrophic and photosynthetic

211
Q

How can lichens colonise bare rock?

A

The fungus is able to absorb minerals from the rock
The alga can photosynthesise to produce sugars

212
Q

How does fungi provide an ideal environment for algae to live in?

A

Anchor themselves to the rock
Form a sense network of hyphae which can trap moisture

213
Q

How do fungus and algae have a mutualistic relationship in lichens?

A

Fungus is able to absorb minerals from the rock
The algae can photosynthesise to produce sugars
Fungi provides an ideal environment for the algae to live in

214
Q

How do mosses form?

A

Over time, bits of lichen die off and form a thin soil for mosses to grow

215
Q

What forms when bits of lichen die off? How?

A

Mosses
Form a thin soil

216
Q

Describe mosses

A

Small plants
Photosynthetic
Spread laterally over the surface of the ground
Grow best when there’s no taller plants to compete for sunlight

217
Q

How does a thin soil for grasses to grow come about?

A

Over time, more dead material from the lichens and mosses accumulate to form the thin soil

218
Q

How does a thin soil form for grasses and ferns to become established in?

A

Dead organic material from lichens and mosses collect in fissures in the rock surface
Together with minerals form the weathered rock, forms a thin soil

219
Q

How can larger plants grow in the soil formed during succession?

A

After several years, the soil becomes deeper and larger plants can grow in it

220
Q

Examples of larger plants that can grow in deeper soil formed during succession

A

Gorse, broom or heather

221
Q

What does what grows in the soil formed during succession depend on?

A

The climate

222
Q

What will eventually become established in the thickening soil formed during succession? Give an example

A

Small trees
Hawthorn

223
Q

Climax community

A

Where the process of succession stops and there’s no further stages

224
Q

When is a climax community established?

A

After years of the soil thickening

225
Q

Trees that lose their leaves in winter

A

Deciduous trees

226
Q

Deciduous trees

A

Trees that lose their leaves in winter

227
Q

Climax community in the UK

A

Deciduous trees (lose their leaves in winter)

228
Q

Climax community of the arctic circle

A

Fir trees

229
Q

Climax community of the tropics

A

Tropical rainforest

230
Q

What does secondary succession begin from?

A

Bare soil

231
Q

How could the bare soil for secondary succession be exposed?

A

after a wildfire

232
Q

When is the climax community achieved fastest - during primary or secondary succession?

A

Secondary

233
Q

What is there no need for in secondary succession?

A

The pioneer species

234
Q

Why is the climax community achieved faster during secondary succession compared to primary succession?

A

The soil is already present and it may contain viable bulbs, seeds and spores
No need for pioneer species

235
Q

What does a wildfire cause?

A

Loss of climax community down to bare soil

236
Q

How are seeds introduced to an area for secondary succession?

A

Blow in
Carried by animals

237
Q

What can human activity do about a climax community?

A

Prevent it from being achieved

238
Q

Examples of human activity preventing a climax community from being achieved

A

Grazing sheep
Heather moorland management by controlled burning (breed grouse for shooting)
Farming of land
Deforestation and soil erosion (roots will decompose)

239
Q

What does a greater species diversity lead to?

A

Greater stability

240
Q

Give some examples of what greater biodiversity offers

A

More food resources
More habitats
More resilience in face of environmental change

241
Q

Describe the relationship between biodiversity and productivity

A

Productivity increases with biodiversity until just before the climax community, where it drops

242
Q

Describe productivity in the climax community and explain this

A

Low
Trees don’t need to grow anymore once they’re mature

243
Q

What is happening when both productivity and biodiversity are increasing?

A

New material is formed all of the time

244
Q

What do plants need to grow?

A

CO2
Sunlight
Water

245
Q

What can plants make with CO2, sunlight and water?

A

Carbohydrates

246
Q

What do plants need to make important compounds for growth?

A

Minerals

247
Q

One of the minerals plants need for growth

A

Nitrogen

248
Q

5 different processes in the nitrogen cycle

A

Nitrogen fixation
Assimilation
Ammonification
Nitrification
Denitrification

249
Q

Why do plants require nitrogen?

A

For the synthesis of amino acids and nucleic acids (DNA, DNA, ATP AND NADP)

250
Q

Name all of the forms in which nitrogen is found in nature

A

Ammonia
Ammonium ions
Nitrite
Nitrate
Amino acids
Nucleic axisa
Urea and uric acid
ATP and ADP
free (gaseous) nitrogen

251
Q

When is nitrogen found as ammonia or ammonium ions?

A

Decomposition/decay

252
Q

In what form is nitrogen in soil?

A

Nitrate ions

253
Q

What is able to happen to the nitrate ions in soil?

A

Can be assimilated into its different compounds
(Amino acids, nucleic acids (DNA, RNA, ATP, NADP))

254
Q

What happens during nitrogen fixation?

A

70% of air is nitrogen, but plants can’t absorb this directly
Some bacteria can, which are free in the soil and in plant roots
These fix nitrogen in the atmosphere

255
Q

What does nitrogen fixation replace?

A

Nitrates lost in denitrification

256
Q

Describe the process of ammonification

A

Plants use nitrates
When they die, this goes back into the soil
Nitrogen is broken down by decomposers
Nitrogen released into the soil in the form of ammonium ions
Ammonium ions are also formed from animal wastes

257
Q

Why is nitrogen sometimes in the form of ammonium ions?

A

Nitrogen released into the soil in the form of ammonium ions (nitrogen from dead plants broken down by decomposers)
Ammonium ions are also formed from animal wastes

258
Q

Name 2 nitrogen fixing bacteria

A

Rhizobium
Azotobacter

259
Q

Rhizobium

A

Mutualistic bacteria which are found in the root nodules of leguminous plants

260
Q

Azotobacter

A

Free-living soil bacteria

261
Q

Where is rhizobium found?

A

In the root nodules of leguminous plants

262
Q

Where does Azotobacter live?

A

Free-living soil bacteria

263
Q

Leguminous plants + examples

A

Large family of plants
Beans, peas, clover

264
Q

What do leguminous plants have?

A

Nodules in roots that contain nitrogen fixing bacteria

265
Q

What’s in the nodules in the roots of leguminous plants?

A

Nitrogen fixing bacteria

266
Q

What do leguminous plants have a mutualistic relationship with?

A

Nitrogen fixing bacteria

267
Q

Describe the relationship between nitrogen fixing bacteria and leguminous plants

A

Mutualistic

268
Q

Equation for nitrogen fixation

A

N2 + 12ATP + hydrogen from water—> 2NH3 + 12ADP + 12PI
Nitrogenase

269
Q

Enzyme involved in nitrogen fixation

A

Nitrogenase

270
Q

Describe the process of nitrogen fixation

A

Very effective process

271
Q

What’s the issue with the process of nitrogen fixation?

A

It uses a lot of energy

272
Q

What’s proof that nitrogen fixation uses a lot of energy?

A

It takes 12ATP to provide sufficient energy

273
Q

Why does nitrogen fixation require so much energy (12ATP’s)?

A

To provide sufficient energy to break the strong triple covalent bond between the two nitrogen atoms of N2 gas

274
Q

Type o f bond between the two nitrogen atoms in N2 gas

A

Triple covalent bond

275
Q

What colour are the roots of clover root nodules and why?

A

Pink
Leghaemoglobin

276
Q

Describe leghaemoglobin

A

Protein similar to haemoglobin, found in the roots of clover root nodules

277
Q

What is inhibited by oxygen in the nitrogen cycle?

A

The process of fixing nitrogen in plant roots

278
Q

What is the process of fixing nitrogen in plant roots inhibited by?

A

Oxygen

279
Q

What does leghaemoglobin do in the roots of root nodules?

A

Buries the O2 in the root nodules, preventing it from interfering

280
Q

What is done about the fact that the process of fixing nitrogen in plant roots is inhibited by oxygen?

A

Leghaemoglobin buries the O2 in the root nodules, preventing it form interfering

281
Q

What type of relationship is there between the nitrogen fixing bacteria and the plant?

A

Mutualistic

282
Q

Why is there a mutualistic relationship between the nitrogen fixing bacteria and the plant?

A

Bacteria —> get an ideal environment and sugar from the plant
Plant —> get nitrogen produced by the bacteria

283
Q

How is ammonia produced on an industrial scale?

A

Using the haber process

284
Q

What does the haber process produce?

A

Ammonia

285
Q

Haber process equation

A

N2 + 3H2 ⇌ 2NH3

286
Q

What is ammonia produced for on an industrial scale?

A

For fertilisers

287
Q

Conditions of haber process (temperature, pressure, catalyst)

A

450 degrees Celsius
200 atm
Iron catalyst

288
Q

How does liquid ammonia come from the haber process?

A

Gases are cooled and ammonia turns to liquid

289
Q

Cons of the haber process

A

Expensive
Inefficient
Releases CO2

290
Q

Describe the conditions of the haber process

A

Extreme

291
Q

How are the conditions for producing ammonia using the haber process extreme?

A

Bacteria can do it 1atm, but the haber process is at 200atm

292
Q

Enzyme in nitrogen fixation

A

Nitrogenase

293
Q

2 types of bacteria in nitrificaion

A

Nitrosomonas
Nitrobacter

294
Q

Number of stages of nitrificaiton

A

2

295
Q

What can bacteria use ammonium to make?

A

Nitrates, which can be absorbed and used by the plant for growth

296
Q

What can use ammonium to make nitrates?

A

Bacteria

297
Q

What can happen to nitrates?

A

Can be absorbed and used by the plant for growth

298
Q

What release nitrogenous compounds during decomposition (decay)?

A

Bacteria and fungi

299
Q

Products f decomposition

A

Ammonium ions

300
Q

Another word for decomposition

A

Putrefaction

301
Q

When do bacteria and fungi release nitrogenous compounds during decomposition (decay)?

A

When an organism dies

302
Q

Stages of nitrification

A

Bacteria…
Convert ammonium into nitrite
Convert this into nitrate

303
Q

Nitrosomonas

A

Convert ammonium into nitrite during nitrification

304
Q

Nitrobacter

A

Convert nitrite into nitrate during nitrification

305
Q

What happens to nitrate once it’s been formed?

A

Absorbed into plan root hair cells by active transport

306
Q

Where is nitrate absorbed to and how?

A

Into plant root hair cells
Active transport

307
Q

What type of bacteria are both Nitrosomonas and Nitrobacter?

A

Free living
Obligate aerobe

308
Q

Denitrification

A

The loss of soluble nitrate compounds from the soil

309
Q

What can occur under anaerobic conditions (denitrification)?

A

Nitrate (produced by nitrifying bacteria) can be converted back into atmospheric nitrogen and lost from the soil

310
Q

Under what conditions can nitrate be converted back into atmospheric nitrogen and lost from soil?

A

Anaerobic

311
Q

What happens when nitrate is converted back into atmospheric nitrogen and lost from the soil?

A

Nitrate supplies will eventually run out
Decreases soil fertility

312
Q

How do farmers avoid denitrification and what does this do?

A

Plough the soil
Ploughing mixes the soil with air

313
Q

Why does ploughing soil work to stop denitrification?

A

The oxygen from the air inhibits the denitrifying bacteria Pseudomonas (grows best under anaerobic conditions) and encourages the growth of Nitrosomonas and Nitrobacter (aerobic nitrifying bacteria) and Azotobacter (aerobic nitrogen fixing bacteria)

314
Q

Denitrifying bacteria

A

Pseudomonas

315
Q

Describe Nitrosomonas and Nitrobacter

A

Aerobic nitrifying bacteria

316
Q

Describe Azotobacter

A

Aerobic nitrogen fixing bacteria

317
Q

Describe land that isn’t ploughed

A

Water logged soil
Lots of denitrification
Little oxygen in soil
Poor conditions for nitrification
=soil with little nitrogen

318
Q

Why can’t trees survive in water logged soil?

A

Limits O2 supply to the roots
Prevents CO2 from diffusing away

319
Q

How have plants evolved to live in soil with little nitrogen?

A

Make use of the free available source of nitrogen in insects

320
Q

2 examples of plants that have evolved to live in soil with little nitrogen

A

Sundew
Butterwort

321
Q

Describe how sundew work to obtain nitrogen form insects

A

Leaves with hairs
Secrete a sticky fluid onto the hairs = catch insects
Fluid contains enzymes to break the insects down
Absorb nitrogen from the compounds in the insect’s bodies

322
Q

Describe how butterwort work to obtain nitrogen form insects

A

Spectres a sticky fluid that catches insects
Absorbs nitrogen form the compounds in the insect’s bodies

323
Q

What’s the name for plant that absorb nitrogen from the compounds in an insect’s body?

A

Insectivorous

324
Q

What do farmers do when growing crops on land and why?

A

Add nitrates to the soil to make it more fertile

325
Q

What happens when we overuse nitric fertilisers?

A

The excess is washing away from the land and leaks into water courses

326
Q

Leaching

A

Soluble compounds and ions, like nitrate are washed out of the soil by rain water and can be carried into rivers and lakes

327
Q

Summary of eutrophication

A

Nutrient load up
Plants flourish
Algae blooms, oxygen is depleted
Decomposition further depleted oxygen
Death of the ecosystem

328
Q

What are these stages describing?

Nutrient load up
Plants flourish
Algae blooms, oxygen is depleted
Decomposition further depleted oxygen
Death of the ecosystem

A

Eutrophication

329
Q

Nutrient load up stage of eutrophication

A

Excessive nutrients from fertilisers are flushed form the land into rivers or lakes by rainwater

330
Q

Plants flourishing stage of eutrophication

A

These pollutants cause aquatic plant growth of algae, duckweed and other plants

331
Q

Algae blooms

A

Rapid increase in the growth of algae in the soil, stimulated by the high levels of nitrates

332
Q

Algae blooms, oxygen is depleted stage of eutrophication

A

Algae blooms, preventing sunlight reaching other plants
The plants die and oxygen in the water is depleted

333
Q

Decomposition further depleted oxygen stage of eutrophication

A

Dead plants are broke down by bacteria (decomposers) using up even more oxygen in the water

334
Q

Death of the ecosystem stage of eutrophication

A

Oxygen levels reach a point where no life is possible
Effects the whole ecosystem
Fish, insects and other organisms die

335
Q

During which stage of eutrophication do oxygen levels rapidly decrease?

A

Decomposition further depleting oxygen

336
Q

2 examples of pollution indicator species

A

Bloodworms
Rat-tailed maggots

337
Q

How are bloodworms and rat-tailed maggots (pollution indicator species) able to survive in low oxygen levels?

A

Adapted for surviving in low O2 concentrations and polluted conditions

338
Q

Pollution indicator species that are only present in clean waters

A

Mayfly larvae
Stonefly larvae
Daphnia

339
Q

When are mayfly larvae, stonefly larvae and daphnia (pollution indicator species) present and why?

A

Only in clean water
Very sensitive to O2 levels

340
Q

Humus

A

Dead organic matter in soil

341
Q

Describe an area that undergoes secondary succession

A

Has been colonised before

342
Q

What happens to the animal population when there’s more plants and why

A

Increases
More niches for the animals

343
Q

What type of conditions does leghaemoglobin provide and why?

A

Anaerobic
Nitrogen fixation only occurs under anaerobic conditions

344
Q

Another way of describing a climax community

A

Community has reaches equilibrium

345
Q

What cannot happen in waterlogged soil?

A

Roots unable to respire aerobically
No active transport of minerals

346
Q

Benefits to insectivorous plants catching prey instead of fixing nitrogen

A

It takes a lot of ATP to fix nitrogen
It’s more energy efficient to digest insects than to fix nitrates

347
Q

Why do fish die when introduced to a new fish tank?

A

Due to a lack of nitrogen cycle

348
Q

Explain why fish die when introduced to a new fish tank

A

Fish produce nitrogenous waste in the form of ammonium
Ammonium is toxic at high levels
Toxic water kills the fish

349
Q

Why do fish not die in their natural environment even though they produce nitrogenous waste in the form of ammonium which is toxic?

A

Due to the nitrogen cycle - bacteria carry out nitrification

350
Q

Describe ammonium

A

Toxic at high levels

351
Q

What do we need to do in a fish tank in order to form a nitrogen cycle?

A

Make a natural environment for the fish

352
Q

How do we make a natural environment for a fish in a fish tank and why?

A

Set up a few weeks before getting a fish
Put in plants
Natural bacteria will process nitrogen

Will make a nitrogen cycle

353
Q

Compare the carbon cycle to the nitrogen cycle

A

The carbon cycle is simpler than the nitrogen cycle, but is very influential on the environment

354
Q

Photosynthesis stage of the carbon cycle

A

Carbon dioxide in the atmosphere is fixed into carbohydrates and sugars and starches by the light independent stage of photosynthesis

355
Q

Respiration stage of the carbon cycle

A

In plants and animals, respiration releases CO2 into the atmosphere due to the action of decarboxylase in the link reaction and Krebs cycle

356
Q

How does respiration release CO2 into the atmosphere?

A

Due to the action of decarboxylase in the link reaction and Krebs cycle

357
Q

Microorganisms responsible for decay

A

Fungi and bacteria

358
Q

Describe the decomposition stage of the carbon cycle

A

Microorganisms responsible for decay (e.g - fungi and bacteria) are decomposers, which release CO2 into the atmosphere due to respiration
They decompose dead plants and waste from animals

359
Q

Describe the feeding stage of the carbon cycle

A

Carbon fixed in organic molecules by producers pass from trophic level to trophic level, along food chains, during feeding

360
Q

How are fossil fuels formed?

A

When conditions aren’t right for decomposition, so dead plants and animal waste end up not decomposing

361
Q

Describe conditions that aren’t right for decomposition

A

Too cold
Not enough oxygen
Water logged

362
Q

What are fossil fuels formed from?

A

The remains of dead plants and animals

363
Q

How long does it take for fossil fuels to be formed?

A

Millions of years

364
Q

Under which conditions are fossil fuels formed and why?

A

Anaerobic
Anaerobic conditions inhibit decay, so fossil fuels are formed instead of decomposition occurring

365
Q

What form fossil fuels from the remains of dead plants and animals?

A

Carbon rich biological molecules

366
Q

Examples of fossil fuels

A

Oil
Coal
Gas

367
Q

What happens during the combustion of fossil fuels?

A

Releases carbon in the form of CO2 into the atmosphere

368
Q

What’s the biggest problem with the carbon cycle?

A

There’s a net increase in CO2 in the atmosphere

369
Q

What happens to fossil fuels if not used for fuel?

A

Remain untouched for millions of years like a carbon store

370
Q

What does digging fossil fuels and burning it do?

A

Releases it in a short space of time

371
Q

How long have we been burning fossil fuels for?

A

About 200 years

372
Q

What does increasing CO2 levels cause?

A

Climate change and global warming

373
Q

What’s the issue with burning fossil fuels?

A

Releases more CO2 into the air than would be there originally

374
Q

What is these in the carbon cycle?

A

An imbalance

375
Q

Why is peat referred to as a fossil fuel?

A

It’s a carbon store that’s built up over millions of years

376
Q

Why has it taken so long for peat to build up as a fossil fuel?

A

Could have been…
Low O2 levels
Cold
Water-logged soil

377
Q

Draw the carbon cycle

A

(See notes)

378
Q

What is peat? Describe it

A

Thick layers of organic material
Spongey, dark, water-logged

379
Q

What can be done to peat to use it as a fuel?

A

When it’s dried out, it can form bricks of fuel

380
Q

How is positive feedback occurring with peat, a type of fossil fuel?

A

In the areas where peat is formed, due to the temperatures of the earth increasing, the peat is starting to decompose faster
= CO2 is released faster
This causes positive feedback as more CO2 leads to it being hotter still

381
Q

What is it referred to when, in the places where peat is formed, due to the temperatures rising, it’s decomposing faster to release CO2 faster?

A

Positive feedback

382
Q

What does increased atmospheric CO2 lead to?

A

An enhanced greenhouse effect, commonly referred to as global warming

383
Q

What drives what in terms of global warming and climate change?

A

Glad warming drives climate change

384
Q

What will climate change ultimately do?

A

Affect the distribution of species and increase extinction rate

385
Q

List 5 effects of climate change

A

Melting polar ice cap and rising sea levels
Increased frequency of extreme weather
Increased desertification and soil erosion
Increased extinction rates
Changes in the distribution of disease vectors such as mosquitos - found in areas where they weren’t before

386
Q

What do all of the effects of climate change have a global impact on?

A

Biodiversity and agriculture

387
Q

What does an increased extinction rate lead to?

A

Less biodiversity

388
Q

What does increased desertification and soil erosion lead to?

A

Agricultural problems

389
Q

Explain the greenhouse effect

A
  1. Radiation from the sun
  2. Some solar radiation is reflected by the earth and the atmosphere, but most is absorbed by the earth’s surface and warms it
  3. Some of the infrared radiation passes through the atmosphere. Some is absorbed and re-emitted in all directions by greenhouse gas molecules (e.g - CO2). The effect of this is to warm the earth’s surface and the lower atmosphere.
390
Q

Why is the greenhouse effect good?

A

There would be no life without it

391
Q

Name a planet where there’s no greenhouse effect and explain why this is true

A

Mars
Only a thin atmosphere

392
Q

What happens on mars due to there being no greenhouse effect?

A

Huge temperature swings

393
Q

What’s the problem with CO2 with the greenhouse effect?

A

Increasing CO2 levels enhances the greenhouse effect

394
Q

Why does increasing CO2 levels enhance the greenhouse effect?

A

CO2 absorbs heat radiating the earth’s surface and re-releases it in all direction, including back towards the earth’s surface

395
Q

Carbon footprint

A

The amount of carbon dioxide released into the atmosphere as a result of the activities of a particular individual, organisation or community over a period of one year

396
Q

What in our day-to-day lives increases our carbon footprint?

A

Driving cars
Heating Homs
Food eaten (the amount of carbon used in production)

397
Q

Over what time period is a carbon footprint a measure of?

A

A year

398
Q

How can we reduce our carbon emissions?

A

By lowering our carbon footprint

399
Q

Give reasons why agriculture has such a high carbon footprint

A

The production of farm tools
The production of insecticides, fungicides and fertilisers
Farm machinery, powered by fossil fuels
Transport of produce

400
Q

In which industry to big changes need to be made and why?

A

Farming
To reduce the carbon footprint

401
Q

Possible changes to farming practices to reduce the carbon footprint

A

Produce less meat
Crops should be grown for human consumption, not as animal feed
Alternatives to rice paddy fields
Packaging should be reduced to a minimum
Transport distances (food miles) should be reduced and more food produced locally for local people

402
Q

Why should we produce less meat?

A

Meat production requires more resources (land, chemicals and feed) than crop production and therefore has a larger carbon footprint

403
Q

What’s the issue with rice paddy fields?

A

Produce methane

404
Q

What’s the problem with methane?

A

It’s a greenhouse gas 25 times more potent than CO2

405
Q

Explain how deforestation could increase the concentration of CO2 in the atmosphere

A

Trees take in CO2 during photosynthesis
More CO2 used in combustion
More decomposition of dead roots = more CO2

406
Q

Describe how deforestation could decrease the concentration of atmospheric CO2

A

Trees respire, releasing CO2

407
Q

How does a soil actually form during succession?

A

Enzymes break down rock

408
Q

What does there have to be in a climax community?

A

Trees

409
Q

What happens to plants when they’re cold?

A

Not resistant to cold = die
Lower germination of certain species = less increase in number of species

410
Q

Why is there a net increase in CO2 in the atmosphere currently?

A

Increased combustion of fossil fuels (releases CO2)
Deforestation (less photosynthesis to absorb CO2)

411
Q

Measures that would reduce the effect of human activity on the carbon cycle

A

Reduce use of fossil fuels
Alternative energy sources
Carbon tax

412
Q

When does water logging of soil occur?

A

When there’s too much water

413
Q

What’s the issue with waterlogged soil?

A

No oxygen for roots to respire
No active uptake of minerals

414
Q

What conditions is water logged soil under and what does this lead to?

A

Anaerobic
Denitrification

415
Q

What are the risks with having lots of individuals of the same species in one area?

A

Predators
Intraspecific competition
Disease

416
Q

What are ammonium ions used for?

A

To make amino acids, proteins and DNA

417
Q

What does Leghaemoglobin do to O2?

A

binds it

418
Q

How do we create axes at right angles to each other for sampling?

A

With tapes

419
Q

What does secondary succession do to the environment and what does this lead to?

A

Changes in the environment
Allows other species to grow

420
Q

What is the carrying capacity of an environment determined by?

A

-biotic and abiotic factors (environmental resistance)
-predator/prey relationships
-inter/intraspecific competition

421
Q

What are decomposers?

A

Bacteria/fungi that respire

422
Q

First species to return during secondary succession

A

Pioneer species

423
Q

Causes of species extinction

A

Hunting
Invasive species/alien species introduced
Habitat loss
Fishing
Pollution
Competition from domestic animals
Global warming
Natural selection

424
Q

Why is it good to genetically modify plants for nitrogen fixation?

A

Higher yield = less land needed for crops = more land for increasing biodiversity
Less chemical fertilisers = less eutrophication

425
Q

Things to consider when reintroducing a species into the wild

A

Need a disease-free donor population
Receiving habitat needs to be suitable
Resources and expertise need to be available for their protection
When introducing, use ones that come from the same region (e.g - European) so that they have the correct genetics of the population and take up the correct niche

426
Q

What does ploughing soil encourage?

A

Nitrification (not nitrogen fixation)

427
Q

Why do warm blooded organisms need to eat more often than cold blooded organisms?

A

Since warm blooded organisms need to maintain body temperature and so use more food in respiration to produce heat

A level Biology (26 decks)

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