Advanced Higher Biology Unit 2

Front 1

What losses are made in every energy conversion?

Back 1

Some energy is lost as heat.

Front 2

What are autotrophs?

Back 2

Otherwise known as producers, they belong in the first trophic level, and use inorganic molecules to form complex organic molecules (e.g. via photosynthesis).

Front 3

What are heterotrophs?

Back 3

Any organism which has to gain energy by consuming organic molecules. They are otherwise known as consumers.

Front 4

What are saprotrophs?

Back 4

A group of heterotrophs that get their energy by feeding on dead organisms or waste material (detritus).

Front 5

What are the two types of saprotrophs?

Back 5

Detritovores and decomposers.

Front 6

What are detritovores?

Back 6

Invertebrates such as the earthworm which take in the material and digest it using enymes inside their body - they have internal enzymatic digestion.

Front 7

What are decomposers?

Back 7

Bacteria and fungi which secrete enzymes onto the material and digest it outside their cells - they have external enzymatic digestion.

Front 8

How is energy fixated in autotrophs?

Back 8

Photosynthesis.

Front 9

What is biomass?

Back 9

All the organic molecules in an organism together.

Front 10

What does primary productivity measure?

Back 10

The rate of accumulation of biomass by plants.

Front 11

What is gross primary productivity?

Back 11

The total yield of organic matter from photosynthesis.

Front 12

What is net primary productivity?

Back 12

The biomass remaining after photosynthesis.

Front 13

What is secondary production?

Back 13

The use of energy to make organic materials for the growth of the animal.

Front 14

What happens to the food that can't be converted into biomass?

Back 14

Some of it is indigestible, and is passed out of the body as faeces. Food material that does get digested and absorbed is used mainly for respiration, so a great deal of energy is lost from the animal as heat and movement.

Front 15

What are homeotherms?

Back 15

Animals such as birds or mammals that use energy to regulate their own body temperature and thus have less energy to use on secondary production.

Front 16

What are poikilotherms?

Back 16

Animals such as invertebrates or fish that have more energy to use on secondary production as they do not use energy from their metabolism to regulate body temperature.

Front 17

What is ecological efficiency?

Back 17

The proportion of energy taken in by one trophic level that is converted into new biomass and so is available to the next trophic level.

Front 18

What happens to faeces?

Back 18

Saprotrophs use it as a food source, resulting in energy flow through saprotrophic food chains.

Front 19

Why are food webs so complex?

Back 19

Because most organisms feed on a wide range of organisms.

Front 20

What are pyramids of energy flow (pyramids of productivity)?

Back 20

Show the energy built into biomass at each trophic level in a unit area in a year. Give an accurate representation of ecological efficiency.

Front 21

Why is the information for a pyramid of energy flow so difficult to gather?

Back 21

Organisms must be burnt to assess energy content and the data has to be collected for a full year.

Front 22

What are pyramids of numbers?

Back 22

They show the number of organisms at each trophic level.

Front 23

What are the limitations of pyramids of numbers?

Back 23

Because the count is made at one point in the year, it is not accurate over the whole year. No account is taken over the size of the organism, so food webs with tree as a producer, for example, can be highly unbalanced.

Front 24

What are pyramids of biomass?

Back 24

Show the total dry mass of organisms at each trophic level.

Front 25

What are the limitations of pyramids of biomass?

Back 25

It does not take into account the energy content of the biomass (so a fatty animal, for example, could be under represented). It also does not allow for changes in biomass present over a year.

Front 26

What happens to the detritus that the detritovores cannot digest?

Back 26

It becomes fragmented into smaller pieces and passes out as faeces, which forms humus. This fragmentation increases the surface area for decomposers to work on.

Front 27

What is decomposition?

Back 27

The chemical breakdown or organic matter in detritus by decomposers.

Front 28

What is the role of soil microorganisms?

Back 28

They make mineral nutrients available again for use by plants.

Front 29

What are the limiting factors on the rate of decomposition?

Back 29

Temperature: Low temperatures cause enzymes to work slowly.

Availability of nitrogen: The microbes need nitrogen to make enzymes and other cell proteins.

Front 30

What can decomposition also be known as?

Back 30

Mineralisation.

Front 31

Why must nutrients be recycled?

Back 31

Because chemical elements are a finite resource.

Front 32

How are nutrients generally recycled?

Back 32

They are fixed into organisms, transformed into various compounds as they pass along the food chain, and then are broken down into simple forms that can be fixed again.

Front 33

How is carbon dioxide recycled?

Back 33

It is fixed by photosynthesis and then recycled back into the atmosphere by respiration.

Front 34

What are the three stages of nutrient cycling?

Back 34

1. Fixation

2. Transformation

3. Loss

Front 35

What happens during the fixation stage?

Back 35

The nutrient is taken from the abiotic environment and fixed into a food web as an organic compound.

Front 36

What happens during the transformation stage?

Back 36

The organic compound can be changed into other molecules.

Front 37

What happens during the loss stage?

Back 37

The organic compounds are lost from the food web; they are broken down to release simple inorganic units back to the abiotic environment.

Front 38

How can nitrogen be fixed with lightning?

Back 38

The lightning provides the high energy to combine atmospheric nitrogen with oxygen from water to form nitrates.

Front 39

In which industrial process can nitrogen be fixed?

Back 39

Haber process.

Front 40

What does biological nitrogen fixation involve?

Back 40

The use of the nitrogenase enzyme which is able to fix nitrogen into ammonium.

Front 41

What are the limitations of the nitrogenase enzyme?

Back 41

1. It needs a lot of energy (16 ATP molecules for every nitrogen molecule fixed).

2. It is competitively inhibited by oxygen.

Front 42

What are the two main types of nitrogen fixing bacteria?

Back 42

1. Cyanobacteria

2. Rhizobia

Front 43

What are cyanobacteria and how do they work?

Back 43

Free living bacteria in soil and water that live as chains of cells. Some of these cells form cysts that are impervious to oxygen, creating anaerobic conditions for the nitrogenase. The other cells are able to supply aerobically to produce the large amount of ATP needed.

Front 44

What are Rhizobia and how do they work?

Back 44

They form a mutualistic relationship with legume plants, living in the root nodules that the plant fills with leghaemoglobin. This molecule binds to the oxygen in the nodule to create the anaerobic conditions necessary for nitrogenase function. Oxygen is then released slowly for aerobic respiration, so that the large amount of ATP needed can be produced.

Front 45

What happens in the transformation stage to the ammonium formed by cyanobacteria?

Back 45

Some diffuses into the soil and is absorbed by plant roots. Some is converted to nitrate ions before being absorbed by plants.

Front 46

What happens in the transformation stage to the ammonium formed by Rhizobia?

Back 46

The ammonium is converted to simple amino acids, some of which are absorbed directly into the legume plant. Once inside plants, the nitrogen is assimilated through the metabolic reactions that form proteins and nucleic acids.

Front 47

What is ammonification?

Back 47

The decomposition of proteins by bacteria to release ammonium.

Front 48

What happens to the ammonium that is not absorbed by plant roots?

Back 48

It is converted into nitrates in the process of nitrification.

Front 49

What are the two types of nitrifying bacteria?

Back 49

1. Nitrosomonas

2 Nitrobacter

Front 50

What does nitrosomonas do?

Back 50

Convert the ammonium to nitrite ions.

Front 51

What does nitrobacter do?

Back 51

Convert the nitrite to nitrate ions, which can then be absorbed by plants.

Front 52

How can nitrogen be lost?

Back 52

By leaching out of the soil ecosystem in water or through denitrification.

Front 53

What happens in the process of denitrification?

Back 53

Nitrate is converted to nitrogen gas by bacteria such as pseudomonas that use the oxygen from nitrate ions for respiration.

Front 54

When does denitrification happen?

Back 54

When soil is water logged and anaerobic (denitrifying bacteria are only active in anaerobic conditions).

Front 55

What happens in the phosphorus cycle?

Back 55

1. Plants absorb phosphate ions from the soil and fix them during production of ATP, nucleic acids, and phospholipids.

2. Animals get their phosphates by eating plants.

3. Decomposers mineralise phosphates back into the soil from dead organisms.

Front 56

Why are phosphates readily lost from aquatic ecosystems?

Back 56

In aquatic ecosystems, phosphate deficiency is a major limiting factor in productivity as the insoluble compounds that phosphate ions form when they combine with other substances settle to the bottom and the phosphate ions cannot be utilised.

Front 57

What is phosphate enrichment and what does it cause?

Back 57

When phosphates are added to an aquatic ecosystem, usually by fertiliser. It is also known as eutrophication.

Front 58

What is predation?

Back 58

A + / - interaction. The consumption of a prey organism by a predator that results in the former's death.

Front 59

What are predator-prey cycles?

Back 59

In an ecosystem with low biodiversity and a simple food web, there are strong links between predator and prey. This means that any change in the abundance of one species will have a density dependent effect on the other.

Front 60

Name an example of organisms who exhibit predator-prey cycles.

Back 60

The lynx and the snowshoe hare.

Front 61

What is grazing?

Back 61

A + / - interaction. The consumption of green plants or algae by herbivorous animals.

Front 62

How has grazing affected the evolutionary process of plants?

Back 62

There is a strong evolutionary selection pressure on plants with basal meristems, as they can tolerate grazing better than plants with aerial meristems.

Front 63

What happens to plants at low grazing intensity?

Back 63

The plant community is dominated by a small number of competitive grass species.

Front 64

What happens to plants at medium grazing intensity?

Back 64

The more competitive species are kept in check, so a wider variety of less vigorous species get a chance to grow too.

Front 65

What happens to plants at high grazing intensity?

Back 65

Many species are unable to recover from frequent grazing. Only the few species that can cope with this damage can survive.

Front 66

What is crypsis?

Back 66

A type of camouflage where the prey species blends into the background.

Front 67

What is disruptive coloration?

Back 67

A type of camouflage where the pattern breaks up the outline of the prey, making it difficult for predators to distinguish the animal's body shape.

Front 68

What does aposematic colouration do?

Back 68

Deter predators through the use of bold or conspicuous patterns combined with a distasteful or toxic nature. The warning coloration usually involves contrasting patterns of black with yellow and red.

Front 69

What is Mullerian mimicry?

Back 69

The resemblance between two harmful or unpalatable species.

Front 70

What is Batesian mimicry?

Back 70

When a harmless species closely resembles a harmful species with aposematic coloration.

Front 71

What kind of interaction is competition?

Back 71

- / -

Front 72

When does competition occur?

Back 72

When two organisms attempt to utilise the same resource.

Front 73

What is intraspecific competition?

Back 73

Competition between organisms of the same species.

Front 74

What is interspecific competition?

Back 74

Competition between different species competing for the same resources.

Front 75

Which of intra and interspecific is more intense?

Back 75

Intra, because members of the same species have identical resource requirements.

Front 76

What is exploitation competition?

Back 76

When competitors do not interact directly - one individual uses a resource before another has a chance.

Front 77

What is interference competition?

Back 77

When the behavoiour of one organism actively prevents another from accessin a resource (e.g. territorial behaviour).

Front 78

What is an ecological niche?

Back 78

The multidimensional summary of an organism's tolerances and requirements, including abiotic and biotic factors.

Front 79

What is the fundamental niche?

Back 79

The set of resources that an organism is capable of using in the absence of competition.

Front 80

What is the realised niche?

Back 80

The set of resources that an organism can actually use in the presence of competition.

Front 81

What is the competitive exclusion principle?

Back 81

Two different species with the same realised niche cannot coexist in a community for any length of time. The population of one species will tend to die out within several generations.

Front 82

What is resource partitioning?

Back 82

When competing species leads one or both species to exploit different components of the resource, reducing competition (e.g. different beak lengths and types allow waders to exploit food of different types in their shared habitat).

Front 83

What are exotic species?

Back 83

Species that are introduced into a community as the result of human activity.

Front 84

How can exotic species have an advantage over native species?

Back 84

Lack of local predators or pathogens.

Front 85

How can addition of exotic species into a community be damaging?

Back 85

Can induce loss of diversity and death of native species.

Front 86

What is symbiosis?

Back 86

The intimate associations between individual organisms of different species. This relationship usually provides at leat one of the species with a nutritional advantage.

Front 87

What type of symbiosis is parasitism?

Back 87

A + / - symbiosis.

Front 88

What is parasitism?

Back 88

When a parasite uses a host's resources for growth and reproduction.

Front 89

What is host-parasite specificity?

Back 89

When coevolution exists between a parasite and host, resulting in a stable relationship between them. The fittest parasites are those that maximise reproduction and transmission rather than kill their hosts, and the fittest hosts will be those that can best tolerate parasitic damage.

Front 90

What are obligate parasites?

Back 90

Parasites that can only survive within the parasitic relationship.

Front 91

What are facultative parasites?

Back 91

Parasites which can survive either within out without their symbiotic relationship/

Front 92

How can obligate parasites be transmitted?

Back 92

Must be transmitted by direct contact. Human tapeworms shed resistant eggs which are passed out in the faeces. Tapeworms return to the human host by growing and developing within the tissues of secondary hosts, species that are likely to feed in areas where there is human faeces, and are often eaten by humans.

Front 93

How else can parasites be transmitted?

Back 93

By vectors which move the parasite from one host to the next.

Front 94

What kind of symbiosis is commensalism?

Back 94

A + / 0 symbiosis.

Front 95

What is commensalism?

Back 95

When one species (the commensal) gets a nutritional benefit, while the other species is unaffected.

Front 96

What kind of things do commensals utilise?

Back 96

Dead parts of the host, the host's waste, or disturbances made in the environment by the host.

Front 97

What kind of symbiosis is mutualism?

Back 97

A + / + symbiosis.

Front 98

What is mutualism?

Back 98

A type of symbiosis where both species get a nutritional benefit. Coevolution often generates a structural compatibility and an exchange of metabolic products often occurs.

Front 99

Name an example of mutualism.

Back 99

Lichen: Algae receive minerals from fungal breakdown of substrate and fungi receive sugars from algal photosynthesis.

Front 100

What is population density?

Back 100

The number of individuals of a species per unit space.

Front 101

What kind of factors make population density change?

Back 101

Birth rate, death rate, immigration, emigration.

Front 102

What are density dependent factors?

Back 102

Those with an impact intensity that increases as the population density increases.

Front 103

Name some examples of density dependent factors.

Back 103

Disease, competition, predation.

Front 104

What is ecological homeostasis?

Back 104

The regulatory effect of biotic influences on population density.

Front 105

How can plant competition be managed?

Back 105

Plant competition is often managed through the use of herbicides. Herbicides can be selective to destroy specific types of species.

Front 106

How can herbicides be destructive?

Back 106

They can result in loss of diversity.

Front 107

How is disease managed?

Back 107

Through the use of pesticides such as fungicides, antibiotics, or antiparasitic drugs

Front 108

How can predation and grazing be controlled?

Back 108

The use of pesticides and insecticides. The use of agents of biological control such as the introduction of a predatory beetle to control the population of a grazing insect.

Front 109

What are abiotic factors?

Back 109

The non living components of the habitat.

Front 110

What are osmoconformers?

Back 110

Organisms that allow their water concentration to be the same as their surroundings.

Front 111

What is tolerance?

Back 111

The ability of an organism to function within a narrow range of conditions.

Front 112

What happens when the conditions are outwith an organism's tolerance?

Back 112

The organism becomes stressed and its chances of survival are reduced.

Front 113

What is avoidance behaviour?

Back 113

When an organism changes its habits to move itself back within the ranges of its tolerance.

Front 114

What is resistance?

Back 114

It is shown by conformers who have adaptations that isolate them from environmental change.

Front 115

What is regulation?

Back 115

When organisms use homeostatic mechanisms to maintain a constant internal environment despite changes in the habitat.

Front 116

What are osmoregulators?

Back 116

Organisms that are able to control their water balance.

Front 117

What is the main benefit of regulation?

Back 117

Regulating organisms can occupy a far wider range of habitats.

Front 118

What is dormancy?

Back 118

When an organism's metabolism is reduced, promoting survival during adverse conditions.

Front 119

What is predictive dormancy?

Back 119

When the change occurs in a regular way, such as seasonally.

Front 120

What is consequential dormancy?

Back 120

Dormancy which only begins after the onset of adverse conditions.

Front 121

What are resting spores?

Back 121

The organism survives long periods of drought or low temperatures inside a structure that only germinates when suitable conditions return.

Front 122

What is diapause?

Back 122

Shorter photoperiods trigger insects to suspend their metabolism to survive the low temperatures of winter. They stay fixed in one developmental stage until conditions improve.

Front 123

What is hibernation?

Back 123

Some smaller thermoregulators switch off their temperature regulation in cold conditions, leading to a slower metabolic rate, so their body temperature falls. They can survive a period of food shortage as they are not using food energy to generate heat.

Front 124

What is aestivation?

Back 124

The organism responds to very hot or dry conditions by going into a state of torpor or inactivity. This means that its metabolic rate is greatly reduced until suitable conditions return.

Front 125

What is succession?

Back 125

The gradual and sequential change in the communities present in an area over a long period of time, starting with the pioneer community, and ending with the climax community.

Front 126

What is autogenic succession?

Back 126

Succession that is caused by the biological processes of the organisms themselves.

Front 127

What is facilitation?

Back 127

When a community alters the conditions so they favour other species and not themselves.

Front 128

What constitutes the pattern of changes in autogenic succession?

Back 128

1. Increase in species diversity.

2. Increase in food web complexity.

3. Increase in niche and habitat variety.

Each successive stage is more stable than the previous.

Front 129

What is primary succession?

Back 129

Occurs on areas that had no organisms living on them previously.

1. Colonisation of barren land. Soil is formed by producing humus, which helps to increase soil depth, soil nutrient content, and soil stability.

2. Pioneer species are lichens and mosses which can attach to the surface of bare rock. They can survive in very unfavourable conditions.

3. The action of the lichens and mosses open up crevices. Small pockets of soil build up in the crevices. The decaying materials form humus which can hold water and contains nutrient ions.

4. This facilitates the growth of more complex plants like leguminous plants which increase the nitrogen content of the soil.

5. This facilitates colonisation by grasses, which stabilise the soil.

6. Eventually the climax community may be able to colonise.

Front 130

What is secondary succession?

Back 130

Succession on soil that has already formed, but which has been cleared of plant life.

Front 131

Why can secondary succession happen quickly?

Back 131

Because the nutrient rich soil is already present and only needs to be stabilised by grass roots.

Front 132

What is allogenic succession?

Back 132

The replacement of one community by another is caused by forces outside the plant community.

Front 133

What is degradative succession?

Back 133

The sequence of detritovore organisms associated with the breakdown and decomposition of a dead animal or plant. It happens in a much shorter time frame than other forms of succession. No plants are involved.

Front 134

How can high yields be achieved?

Back 134

1. Use of high yield crops.

2. Optimal nutrients for rapid growth provided.

3. The cultivation of crops as monocultures.

4. Pest and competitor control.

5. Mechanisation of soil and crop management.

Front 135

What is the impact of intensive farming on ecosystem complexity?

Back 135

Reduced species diversity, loss of ecosystem complexity, lower stability. Risk of pest proliferation.

Front 136

What is the impact of intensive farming on soil condition?

Back 136

Single species cropping (which exhausts the supply of certain nutrients) combined with mechanisation (which compacts the soil crumb texture, increasing erosion and soil loss) results in poorer soil quality.

Front 137

How can nutrients from fertilisers be lost?

Back 137

1. Leaching, when dissolved nutrients wash through the soil.

2. As run off, when nutrients become dissolved in surface water and are washed away.

Front 138

What happens when inorganic nutrients are washed into freshwater ecosystems?

Back 138

Eutrophication may occur, which can lead to environmental damage by algal bloom.

Front 139

What kind of issues do algal blooms cause?

Back 139

1. Death of algae.

2. Death of plants due to lack of light because of blocking by the blanketweed.

3. Death of animals due to disrupted food chains and toxic algae.

Front 140

What do all of these issues contribute towards?

Back 140

Biodegradable organic pollution from these sources provide food for decomposers. These have a biochemical oxygen demand, and thus there is a resultant oxygen depletion in the water, killing the most sensitive species, resulting in loss of diversity.

Front 141

What is BOD?

Back 141

The amount of oxygen required by the aerobic organisms to decompose the organic matter in a sample of water or pollution.

Front 142

What is significant about the specificity of toxic pollutants?

Back 142

Some toxins are specific and only affect certain organisms. However, some are non-specific, nd these are considered more hazardous to the environment.

Front 143

What are persistant toxic pollutants?

Back 143

Ones that are not easily broken down in the environment because they contain non-biodegradable molecules and are resistant to the actions of consumer and degradative enzymes.

Front 144

What is bioaccumulation?

Back 144

The higher concentration of pollutants within an organism (especially in the fatty tissues), trophic level, or community compared to the concentration in the environment.

Front 145

What is biological magnification?

Back 145

The accumulation of pollutants to higher and higher concentrations in successive trophic levels within an ecosystem, often until they become lethal to top predators.

Front 146

What is biotransformation?

Back 146

The changes a toxic pollutant can undergo once it is in an organism. This can result in degradation, or even in the formation of another toxic substance.

Front 147

What is DDT?

Back 147

A non-specific insecticide:

-persistent pollutant

-long half life

-almost non biodegradable

-bioaccumulates, and biological magnification also occurs

-dangerous to top level birds

Front 148

What are acidic gases?

Back 148

Sulphur dioxide, nitrogen oxides, carbon dioxide. Dissolve in atmospheric water to form acid rain which lowers the pH of water ecosystems and soil.

Front 149

What are greenhouse gases?

Back 149

Carbon dioxide and water enhance the greenhouse effect leading to climate change.

Front 150

What is the greenhouse effect?

Back 150

The maintenance of the Earth's temperature through the reflection of outgoing heat by water vapour and carbon dioxide.

Front 151

How is the enhanced greenhouse effect caused by us?

Back 151

CFCs and methane.

Front 152

How can global warming affect organisms?

Back 152

The increase in temperature will affect the distribution of many species.

Front 153

Describe coral bleaching.

Back 153

Coral polyps form a mutualistic relationship with a type of alga called zooxanthellae. The algae gain CO2 and ammonium from the coral polyp, and the polyp gains sugars from algal photosynthesis. Sea temperature increases upset the balance of this relationship, causing the build up of harmful algal metabolites. The polyp expels its now toxic partner and dies, leaving behind only its limestone skeleton.