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Biology A Level > Ecology > Flashcards

Ecology Flashcards

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1
Q

What is Ecology?

A

The study of organisms in their environment

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2
Q

What is an environment?

A

The conditions that surround an organism, including biotic and abiotic factors

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3
Q

What are Biotic factors?

A

The living parts of an environment

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4
Q

What are abiotic factors?

A

The non-living parts of an environment

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5
Q

What is an ecosystem?

A

The community of organisms and abiotic factors in a given area.

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6
Q

What is a habitat?

A

The location where an organism lives

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7
Q

What is a species?

A

Organisms that look similar and can breed to produce fertile offspring

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8
Q

What is a population?

A

All the members of the same species living together in the same place at the same time

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9
Q

What is a Community

A

A group of different species living together in the same place at the same time.

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10
Q

What is a niche?

A

The role a species has in its environment, governed by adaptation to both abiotic and biotic conditions.

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11
Q

Describe how one would use random sampling with a quadrat in four steps

A

Step 1– Divide the desired area into coordinates (this can be done with tape measures) Step 2- Use a random number generator to randomly choose coordinates Step 3- Place the quadrats in the area corresponding to the coordinates Step 4- Either calculate the % cover, count the organism or somehow measure abundance.

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12
Q

When is transect sampling used?

A

When organism distribution has spatial variation

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13
Q

Describe how one would use transect sampling with a quadrat in four steps

A

Step 1- Place a transect (line with marked intervals) across the desired area Step 2- Place a quadrat at each interval Step 3- calculate the percentage cover or count the number of organisms in each quadrat Step 4- Repeat while moving the transect and calculate the average number of organisms at each distance.

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14
Q

How can you make sure you have a representative sample of a population?

A

You must repeatedly test random samples.

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15
Q

Describe the mark-release-capture form of measuring population in four steps

A

1) Catch count and mark a sample of animals 2) After a period of time, catch a new sample 3) count the number of marked individuals in the new sample 4) Use the equation to calculate population size

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16
Q

What is the equation used in the mark-release-capture form of measuring population?

A

Total no. of individuals in sample 1 x total no. of individuals in sample 2 __________________________________________________ Number of marked individuals captured

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17
Q

What are the factors you must avoid/prohibit if using the mark-release-capture technique?

A

Between collecting samples 1 and 2, there must be little to no migration of the species, little to no reproduction and the marking must not influence behavior or increase vulnerability to predation.

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18
Q

What is an autotroph?

A

An organism that is able to make its own food

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19
Q

How much of the sun’s energy is converted into organic matter (glucose)?

A

1-3%

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20
Q

How much of the sun’s energy is reflected back into space?

A

90%

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21
Q

Name three reasons why light energy from the sun may not be converted to glucose

A
  • Not all wavelengths of light can be absorbed, different types of chlorophyll require different wavelengths - Light may not fall on a chlorophyll molecule - If there is a limiting factor, such as low carbon dioxide levels
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22
Q

What is the equation for the net production of chemical energy/carbohydrates formed in photosynthesis?

A

Net Production = Gross Production - Respiratory Losses

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23
Q

What is gross production?

A

The total amount of carbohydrates/chemical energy produced in photosynthesis.

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24
Q

What are respiratory losses?

A

The total amount of energy/carbohydrates from photosynthesis lost/used in respiration

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25
Q

Roughly how much of the gross production from photosynthesis is used in respiration?

A

20-50%

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26
Q

What is net production?

A

The amount of energy stored after respiratory losses that can be passed on to the next trophic level.

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27
Q

How much of the producers energy is used as useful energy by primary consumers after consumption?

A

5-10%

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28
Q

How much of the primary consumers energy is used as useful energy by secondary and tertiary consumers after consumption?

A

15-20%

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29
Q

Give four reasons why so little energy is passed down through each trophic level?

A
  • Some parts of the organism is not eaten - Some energy is lost in excretory materials e.g. urine - Some carbohydrates can not be digested so are simply lost in faeces. - Some energy losses occur as heat from respiration, especially in animals with high body temperature, as a lot of energy is needed to maintain their high body temperature
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30
Q

Why food chains only tend to have 4-5 trophic levels?

A

As energy transfer between the levels is relatively inefficient, the more levels there are, the less energy is passed on, to the point where there is too little energy passed on for any function.

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31
Q

Why are there less numbers of consumers at higher trophic levels?

A

As they receive less energy in the energy transfer chain.

32
Q

How do you measure the efficiency of energy transfer in trophic levels?

A

Efficiency = the energy available after the transfer //divided by// the energy available before the transfer x 100

33
Q

What are saprobionts?

A

Also known as decomposers, they are a group of organisms that break down the complex materials in dead organisms into simple ones.

34
Q

What is biomass?

A

The total mass of living material in a specific are at a given time

35
Q

Why are food webs a more accurate way of representing energy transfer?

A

Food webs are a better representation of feeding relations in an ecosystem as most animals do not rely on a single food source, but rather multiple food sources.

36
Q

What is fresh mass? Why is it not often used to measure energy in biomass?

A

Biomass in it’s living form. Fresh mass is easy to access, however, different plants/animals have varying amounts of water, which could make measuring its energy more difficult.

37
Q

What is dry mass?

A

A type of biomass ,usually used to measure the energy in biomass, which is dead.

38
Q

What is one positive and two negatives to using dry mass to measure the energy in biomass?

A

It is more reliable to measure than fresh mass as it does not have the same water retention However, the organisms have to be killed which makes the process more time consuming and can make the dry mass less representative of the real biomass.

39
Q

How is biomass measured?

A

In dry mass per given area (Kgm2)

40
Q

Describe how one can estimate the chemical energy in dry mass using calorimetry?

A
  • a sample of dry mass is burned with pure oxygen in a sealed chamber called a bomb - The bomb is surrounded by water bath and the heat of combustion causes the surrounding water to increase in temperature - As we know the energy needed to raise 1ml by 1 degree C, we can use the volume of water and the number of degrees C it increases by to calculate the energy released by the burning biomass.
41
Q

What is mycorrhizae?

A

Fungi that have a symbiotic relationship with the roots of plants - They act as an extension to the plants roots.

42
Q

Why is mycorrhizae symbiotic?

A

The fungi increase the surface area of the plant’s roots. They therefore increase the rate of absorption of water and nutrients. The fungus receives carbohydrates from the plant

43
Q

What is the Nitrogen Cycle and what is its purpose?

A

The nitrogen cycle helps turn nitrogen gas in the atmosphere into nitrate that can be taken up by plants (and combined with glucose to create amino acids) and then return the nitrate to nitrogen in order to re-enter the atmosphere.

44
Q

What is ammonification?

A

The production of ammonia from organic nitrogen-containing compounds. These are then converted into ammonium ions, which are then converted into nitrate ions, which can then be taken up by plants. This process is carried out by saprobionts and bacteria feeding on faeces and dead matter which contain these nitrogen containing compounds and converting this into ammonium ions that they release into the soil.

45
Q

What are four examples of the substances broken down in ammonification?

A

Urea, protein, nucleic acids and vitamins

46
Q

What is nitrification?

A

The converting of ammonium ions to nitrite ions and then to nitrate ions by nitrifying bacteria.

47
Q

Where do plants get most of their nitrogen? Why does this make nitrification very important?

A

From nitrate ions in the soil This then makes nitrification important as it replenishes the amount of nitrate ions in the soil.

48
Q

What is denitrification?

A

It is the process by which nitrogen ions are converted into nitrogen gas which is then released into the atmosphere.

49
Q

What sort of bacteria carry out denitrification?

A

Anaerobically respiring bacteria

50
Q

What conditions are usually typical for denitrification, why?

A

Denitrification tends to most commonly occur when soil has become waterlogged, therefore reducing the aeration/oxygen concentration and causing more anaerobically respiring bacteria to be present, which are the bacteria that carry out denitrification.

51
Q

What is nitrogen fixation?

A

The process by which nitrogen gas is converted into nitrogen-containing compounds. In nitrogen fixation, nitrogen-fixing bacteria will reduce gaseous nitrogen to nitrogen containing compounds..

52
Q

Name two ways that nutrients can be lost from the nutrient cycle How can these nutrients be artificially replaced?

A

Nitrates and phosphates can be lost from the nutrient cycle when crops are harvested/livestock removed or when nutrients from the nutrient cycle can not be released back into the soil. These nutrients can be replaced with fertilisers

53
Q

What is eutrophication

A

When rapid growth of algae occurs due to making it’s way into bodies of water, causing this algae to block light from reaching the plants below it, which then die as they can not photosynthesize. Aerobically respiring saprobionts then decompose the dead plant matter which then reduces the oxygen concentration in the water. This then leads to the death of aquatic organisms due to a lack of dissolved oxygen in the water ready for aerobic respiration.

54
Q

What happens in the phosphorus cycle?

A

Phosphate ions are released from rocks by erosion/weathering. The phosphate ions are then taken up by plants and incorporated into the biomass. These phosphate ions are then transported through the food chain Some of the phosphate ions are then released back into the soil via excretion and some from saprobionts digesting dead organisms.

55
Q

What happens in the phosphorus cycle on coasts?

A

Rocks from the coast release phosphate into the ocean, which is then taken up by algae which is then passed along the food chain to birds. The bird’s waste (and breaking down of the bird by saprobionts once it is dead) then returns the phosphate to the soil.

56
Q

Name four abiotic factors affecting population size?

A

Temperature (linked to denaturing of enzymes) Light (source of energy for most ecosystems) pH (affects enzyme action) Water and humidity (affects transpiration rate)

57
Q

Name three biotic factors that affect population size?

A

Competition Predators Parasites and disease

58
Q

When does competition occur?

A

Competition occurs when the niche of any two species overlap.

59
Q

What is intraspecific competition?

A

competition between two organisms of the same species . Because the organisms are the same species, they have the same niche. The population will therefore vary due to some organisms being able to better compete than others.

60
Q

What is interspecific competition?

A

Competition between organisms of different species. This occurs due as the organisms occupy part of the same niche. One population will have a competitive advantage over the other, so the superior population will grow.

61
Q

What is the competitive exclusion principle?

A

where populations of two species initially occupy the same niche one will normally have the competitive advantage.

62
Q

What occurs in the predator-prey cycle?

A

The predators eat the prey, therefore reducing the population of the prey. Fewer prey means that the predators are more in competition with each other. The predator population is therefore reduced as some predators are not able to obtain enough food to survive or reproduce. Therefore, fewer prey are predated, so more survive, so the population increases. With more prey available, there is more food available to the predators, the predator population then increases. This cycle then repeats.

63
Q

What are pioneer species? What features do these pioneer species tend to have (5 examples)?

A

Organisms that colonise inhospitable environment. They tend to have features that suit them to new colonisation, such as asexual reproduction, production of seeds/spores, rapid germination, nitrogen fixation and tolerance to extreme circumstances.

64
Q

what is a climax community?

A

The community that occurs after all the stages of colonisation. This community usually has high biodiversity, with a population made of both animals and plants.

65
Q

What happens during primary succession?

A

An abiotic environment becomes less hostile, resulting in a higher population, a greater number of habitats, increased biodiversity, more complex food webs and increased biomass

66
Q

What is secondary succession? How is this different from primary succession?

A

This occurs when the land is altered in some way, e.g. by fire, disease, grazing or agriculture. Recolonisation then occurs. This is usually a much more rapid process than primary succession and only involves the recolonisation of later colonies (e.g. tertiary consumers, shrubbery or woodland). Therefore, this can often lead to the climax community being slightly different

67
Q

What are the three methods by which genetic variation can take place?

A

Mutations. meiosis and the random fertilization of gametes in sexual reproduction.

68
Q

What are three factors that natural selection and evolution depend on?

A

-Organisms produce more offspring than can be supported by the available supply of food, light,space etc. - There is genetic variety within the population of the species - There is a variety of phenotypes that selection operates against.

69
Q

what is stabilising selection?

A

A process of selection that preserves the phenotypes around the mean of a population by favouring average individuals (and not favouring the extreme phenotypes)

70
Q

What is directional Selection?

A

When selection changes the phenotype of the population by favouring phenotypes that vray in one direction from the mean of the population. This is therefore selection for one extreme phenotype.

71
Q

What is disruptive selection?

A

Selection that favours individuals with extreme phenotypes rather than those with phenotypes around the mean of the population

72
Q

What is the Hardy-Weinberg principle?

A

A principle that states that allele and genotype in a population will remain constant from generation to generation in the absence of selection pressures and external influences.

73
Q

What are the four factors that can affect the Hardy- Weinberg principle?

A

Random Mating, Selection, Mutation and Small Population Size.

74
Q

How do you calculate net production from ingested food?

A

N= I-(F+R) Where N is net production, I is ingested food, F is what is lost in feces and urine and r is respiratory losses

75
Q

What is the equaion for standard deviation?

A

First, you find the mean of your numbers (Ẋ)

Then for each mumber (x) you subtract the mean and square the result

Then, you work out the mean of all those squares (the Σ divided by n part)

Then you square root all of this

Biology A Level (10 decks)

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