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Biology Year 13 > The Nature Of Ecosystems > Flashcards

The Nature Of Ecosystems Flashcards

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1
Q

What is an ecosystem?

A

A life supporting environment. It includes all of the living organisms which interact together, the nutrients that cycle throughout the system and the physical and chemical enviornment in which the organisms are living. An ecosystem consists of a network of habitats and the communities of organisms associated with them

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2
Q

What is a habitat?

A

The place where the organism lives.

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3
Q

What is a microhabitat?

A

Many organisms only occupy small parts of a habitat (e.g. a wasp lives in a fig in a tree). These are microhabitats

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4
Q

What is a population?

A

A group of organisms of the same species, living and breeding together in a habitat.

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5
Q

What is a community?

A

All the populations of all the different species of organisms living in a habitat at any one time

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6
Q

What are abiotic factors?

A

The non-living elements of the habitat of an organism. They include those related to climate (such as the amount of sunlight, temperature and rainfall) and those related to the soil (edaphic factors) including the drainage and the pH

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7
Q

What are Biotic factors?

A

The living elements of a habitat that affect the ability of a group of organisms to survive there. E.g. the presence of suitable prey species will affect the numbers of predators in a habitat

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8
Q

What is the biosphere?

A

All of the areas of the surface of the Earth where living organisms survive

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9
Q

What are Biomes?

A

The major ecosystems of the world

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10
Q

What is succession?

A

A process by which communities of animals and plants colonise an area and then over time are replaced by other, usually more varied species

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11
Q

How does Primary Succession take place?

A
  • starts with an empty inorganic surface such as bare rock or sand dune.
  • the first organisms are opportunists or pioneer species such as algae, mosses and fungi. These organisms can penetrate the rock surface, helping to break it into small grains, and trap organic material that will break down to form humus. The inorganic rock grains amd the organic humus are the start of the formation of soil
  • once there is soul other species such as grasses and ferns can establish root systems. The action of theirl roots and the humus they form when they die and decay, add to the soil
  • as the soil layer develops more water and nutrients are retained and become available for plant roots, and so less hardy species can survive
  • gradually larger plants can be supported and the diversity of species increases.
  • as plant diversity increases the biodiversity of animals that can be supported also increases
  • eventually a climax community is reached where the biodiversity and range of species are generally constant. A climax community is self sustaining and usually the most productive of organisms that the environment can support
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12
Q

What is a climax community?

A

A self-sustaining community with relatively constant biodiversity and species range. It is the most productive group of organisms that a given environment can support long term

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13
Q

What is a Climatic climax community according to Clements definition?

A

The only climax community possible in a given climate

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14
Q

What is a plagioclimax?

A

A climax community that is at least in part the result of human intervention. They are constant and self sustaining but wouldn’t have occured without humans changing the landscape, for example bh clearing woodland

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15
Q

What is a secondary succession?

A

The development of an ecosystem from existing soil that is clear of vegetation. The sequence of events is very similar to primary succession but because the soil is already formed amd contains seeds, roots and soil organisms the number of plants and animals present right from the beginning of the succession are much higher

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16
Q

When is primary succession usually seen?

A

After a volcanic erruption, or landslide or after the emergence of a new volcanic Island

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17
Q

When does secondary succession occur?

A

As rivers shift their courses, after fires and floods and after disturbances caused by humans

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18
Q

What are the stages of a secondary succession from bare earth to oak woodland?

A
  • Bare earth, grass, weeds
  • grass stage
  • grass and shrubs
  • young forest - pines, some young hardwoods
  • mature forest- mainly oak
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19
Q

What dies the time it takes to go from an area of bare earth to a climax community depend on?

A

• climatic factors:
- temperature
- rainfall and the underlying soil fertility
• the plants, animals and microorganisms that are within or able to colonise the area

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20
Q

Why is it not always easy to observe secondary succession?

A

Because it is a process that occurs over a long time

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21
Q

What an show a complete record of the stages of succession?

A

Sabd dunes

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22
Q

Why was it easy to observe primary succession in Surtsey?

A

A volcanic eruption burst through the surface of the sea off the coast of Iceland. The hot magma cooled rapidly to form a new Island. By 1967 whe tbe erruptions stopped the Island was 2.7km2. A huge area of volcanic rock

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23
Q

How did the primary succession take place in Surtsey?

A

The earliest colonisers were mould, bacteria and fungi, followed by flowering plants. Initially all the plants died over the winter but after permenant llant communities established gull colonies followed. The bird droppings added fertility to the soil. Many plant species flourished including willow trees and orchids and many species of invertebrates and birds live there now

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24
Q

What does the interaction of abiotic and biotic factors result in?

A

Different ecological niches which change as the factors change

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25
Q

What are microclimates and give an example?

A

A small area with a distincr climate that is different to the surroundings

E.g. logs placed for seating on a grass area. Underneath the log it will be damp and shady whereas in the grassy area it may be sunny and dry

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26
Q

Why does the amount of light in a habitat have a direct effect on the numbers of organisms found there?

A
  • plants are dependent on light for photosynthesis, so any plant populations that are going to thrive in these habitats must cope with this factor. (E.g. some plants reproduce early to avoid the shade caused by larger plants, other plants may havr extra chlorophyll or a different ratio of the photosynthetic pigments that are sensitive to lower light levels)
  • animals are affected by light levels indirectly as a result of the distribution of food plants. Seasonal light changes also affect the reproductive patterns in many animals and the 24 hour cycle of light and dark imposes order on the circadian rhythms that control much of animal physiology and behaviour
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27
Q

Why does temperature affect the number of organisms found in a habitat?

A
  • every organism has a range of temperatures within which it can grow and successfully reproduce. Reproduction does not occur above or below that range. The extremes of the temperature determine where an organism can live
  • it affects the rate of enzyme controlled reactions in plants and ectothermic animals. Organisms without adaptations for extreme temperatures in environments that call for them will not survive
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28
Q

Why does wind have a direct effect on organisms in a habitat?

A

Wind increases water loss from the body and cooling and so adds to the environmental stress of an organism. Whole woodlands may be destroyed in gales and hurricanes and the communities of plants and animal life within them lost.

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29
Q

Why does water current have a direct effect on organisms in a habitat?

A

In water currents organisms have to flow with the current, be strong swimmer or be able to attach to a surface and resist the force of the water. Currents are the most damaging to populations when the strength increases suddenly such as when flooding occurs

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30
Q

In a terrestial enviornment what is the availibility of water affected by?

A

The amount of precipitation, the rate of evaporation and edaphic factors such as the rate of loss by drainage through the soil

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31
Q

What will an increase and decrease in water availability do to the number of organisms in a habitat?

A
  • if the water stress is too severe organisms will die unless they have special adaptations to enable them to survive and reproduce in very dry conditions
  • an increase in water availability will lead to a huge change in habitat and massive increase in population size of some organisms. E.g. flowering of the desert
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32
Q

When will the oxygen content in water be high or low and what will this affect?

A
  • when water is cold or fast flowing sufficient oxygen dissolves in it to support life
  • if the temperature of the water rises or it becomes still and stagnant the the oxygen content will drop
  • this will affect the survival of the populations within it
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33
Q

When is the oxygen content in soil high and when is it low and what will this affect?

A
  • it is usually high as soil is well aerated and the spaces between the soil particles contain air so there is plenty of oxygen for the resipiration of plant roots
  • when the soil becomes waterlogged the air spaces are filled with water and the plants may be deprived of oxygen
  • this leads to death of the plants unless they have adaptations (e.g. the aerial roots of mandrakes)
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34
Q

What is the structure of sand?

A

It has a loose shifting structure

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35
Q

What plant populations can survive in sand and what do they do?

A

Plant populations that are linked by massive roots and rhizome networks such as marram grass. They bind the sand together making it more suited for colonisation by other species

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36
Q

How are Marram grasses adapted to survive in sand and the physiological drought conditions that occur on the seashore?

A

The leaves curl round on themselves with the stomata on the inside creating a microenvironment which reduced water loss.

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37
Q

What is leaching?

A

Leaching describes the loss of minerals from soil as water passes through rapidly

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38
Q

What is the problem with the leaching of minerals in sand?

A

It means that plants population densitys are reduced as they don’t get the minerals they need as the water flows by too fast

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39
Q

Why is it hard for plants to survive in clay?

A

Because water doesn’t pass through very easily and the clay becomes easily waterlogged so there is a lack of oxygen for the plants and they may not always be able to get the necessary minerals

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40
Q

Why is loam the ideal soil?

A

It has particles of a wide range of sizes. It is heavier and less prone to leaching than sandy soils, yet easier to warm and work than clay.

41
Q

Why does a mathematical model that describes the relationships between prey and predator relationships predict that the populations will oscillate in a repeating cycle?

A

As a prey population increases there is more food for the predators and so after an interval the predator population grows too. The predators will increase to the poing where they are eating more prey than are replaced by reproduction so the numbers of prey will fall. This will reduce the food supply of the predators so they will not produce as many offspring and their numbers will fall, allowing the abundance of prey to increase again and so on

42
Q

How does reproduction help to determine the organisms that are found in a habitat?

A

The likelihood of finding a mate or achieving pollination will help to determine the organisms that are found in any habitat. So if a single seed is dispersed to a new area, germinates, grows and survives that species of plant is unlikely to become a permenant resident unless other plants of the same species are found in that area. Similarly a single individual of an animal species in an area does not mean the species lives in that habitat. These must be malea and females so mates can be found

43
Q

What are territories?

A

An area held ans defended by an animal or group of animals against other organisms which may be of the same or different species

44
Q

What are territories used for in animals?

A

Almost always used in some way to make sure that a breeding pair has sufficient resourves to raise young. The type and size of territory will help to determine which species live in a particular community

45
Q

Why do diseases have a devastating effect on individuals?

A

Diseased animals will be weaked and will often not reproduce succesfully. Sick predators cannot hunt well and diseased prey animals are more likely to be caught. Some diseases such as bird flu are very infectious and can be spread without direct contact

46
Q

How do parasites affect their hosts?

A

Usually by feeding off the living body of their host and so weakening it

47
Q

Why will an infectious disease or parasite have a devastating effect if almost all of the organisms of an area are of the same species?

A

Parasites and other infectious diseases spread more rapidly when there is a high population density as individuals are in close proximity to eachother. If all the organisms of an area are of the same species it will affect most of the individuals directly or indirectly

48
Q

How does population size affect density-independent factors of the number of organisms occupying a particular nice?

A

It doesn’t. The effect of these factors is the same regardless of population size. E.g. extreme temperature will usually haave the same effect on all individuals

49
Q

What does the impact of a density dependent factor depend on and give an example

A

The impact of a density dependent factor will depend on how many organisms there are within a specific area. E.g. disease and parasitism are strongly density dependent as the more individuals there are in a given are the more likely it is that a disease or parasite can be transmitted between individuals

50
Q

When does competition occur?

A

When two organisms compete for a resource that is in limited supply

51
Q

What may competition be for?

A
  • Abiotic resources such as sunlight, minerals or oxgyen

* biotic resources such as territories, nest sites or mates

52
Q

What has competition for mates led to?

A

Sexual selection and to the evolution of sexual dimorphism

53
Q

What is intraspecific competition?

A

The competition between members of the same species for a limited resource

54
Q

What can be a result of intraspecific competition?

A

Some individuals may not survive or reproduce and so population growth slows.

55
Q

When does interspecific competition occur?

A

When different species within a community compete for the same resources.

56
Q

What will competition often do in terms of species or population abundance?

A

Intraspecific competition may decrease the size of the population of the species. Interspecific competition may reduce the abundance of a competing species and could even lead to extinction

57
Q

When scientists are considering the ecology of an area of natural habitat what will they measure?

A

The abundance and distribution of organisms in the area

58
Q

What is the abundance of an organism?

A

It refers to the relative representatuon of a species in a particular environment

59
Q

What does the distribution of an organism describe?

A

Where is species of organism is found in the environment and how it is arranged

60
Q

What are the three patterns of distribution that an organism in a habitat will usually fall into (one of these)

A

Uniform distribution, clumped distribution, randon distribution

61
Q

When does uniform distribution usually occur?

A

When resources are thinly but evenly spread, or when individuals of a species are antagonistic to eachother. The territories may be very large of very small. For example nesting penguins, polar bears and hawks

62
Q

What is clumped distribution?

A

This is the most common distribution seen with herds of animals or groups of plants and animals that have specific resource requirements and therefore clump in areas where those resources are found, e.g. a herd of sheep

63
Q

What is random distribution?

A

This is the result of plentifull resources and no antagonism, e.g. dandelions in a lawn

64
Q

What is the simplest way to sample an area?

A

To use a quadrat

65
Q

When is a quadrat particularly useful to use?

A

It is particularly useful for plants and animals that do not move much

66
Q

What is a frame quadrat?

A

Usually a square frame divided into sections that you lay on the ground to identify the sample area

67
Q

What is the size of quadrat we usually use and why?

A

Ones with side of 50cm or 25cm because they are easier to handle

68
Q

Why is using a quadrat a quantative sampling technique?

A

It allows us to quantify and meashre things such as the number of individual organisms in the area (individual counts) or using the divided grid, the area covered by the above ground parts of a particular species (the percentage cover)

69
Q

What are the limitations of frame quadrats?

A
  • limitations to the area you can sample
  • the randomness of the sampling sitee
  • decisions about whether to include or exclude organisms partly covered by the quadrat
70
Q

What is the ACFOR scale used for?

A

To measure the abundance of organisms in a quadrat or any other given areas

71
Q

What does the ACFOR scale describe the abundance of a given species as?

A 
A = Abundant
C = common
F = frequent 
O = occasional
R = rare
72
Q

What are the limitations of the ACFOR scale?

A
  • it is subjective
  • there are no set definitions of the terms
  • species can be easily rated on how obvious they are
73
Q

What is a point quadrat and how does it work?

A

A horizontal bar supported by two or three legs. At set intervals along the bar are holes through which a long pin is dropped. The species that the pins touch are recorded. They are often used to estimate the percentage cover by recording how many of the ten pins touch a particular species of plant. A number of readings are taken and a mean percentage is calculated (e.g. if 5 out of 10 pins touch the species the percentage cover is 50%)

74
Q

How are permanant quadrats used?

A

They are left in place all the time and the data is collected throughout the seasons or from year to year

75
Q

How can quadrats be used to randomly sample areas?

A

By placing them at random coordinates

76
Q

What is a line transect?

A

A way of gathering data more systematically. A tape is stretched out between two points and every individual plant (or animal) that touches the tape is recorded

77
Q

What is a belt transect?

A

When two tapes are laid out and the ground between them surveyed

78
Q

How do line transects work?

A

You record every individual plant or animal that touches the tape

79
Q

How can transects be used for systematic sampling?

A

When they are laid out along a tape to form a belt transect

80
Q

What can transects be used to investigate and how?

A

They can be used to investigate whether a change in the distribution of organisms is linked to a change in an abiotic factor. By sampling the abundance of organisms at regular intervals along the transect and also sampling and recording abiotic factors such as soil pH or light intensity, correlations between them may be found

81
Q

What are light traps and what are they useful for?

A

They are often used to capture night-flying insects that are attracted to the light. They are useful for measuring the abundance of an organism

82
Q

What are the limitations of using light traps?

A

You do not know where the insects have travelled from so it is hard to measure distribution

83
Q

How does the mark, release, recapture method work?

A

You capture animals on one occasion, marking them in a way that does not affect their survival chances and releasing them. Subsequent captures are examined to find out how many of the marked animals have been recaptured and these data can be used to estimate population numbers in the area

84
Q

What is the mark, release, recapture method good for measuring?

A

Distribution of a population in a particular area

85
Q

How are animals in tree canopies often collected?

A

By beating the branches and collecting what falls out

86
Q

What are the limitations of the method of tree beating?

A

This method misses many populations that live at the top of trees including birds.

87
Q

What is the fogging method and what are it’s limitations?

A

Spraying an entire tree with anaesthetic gas and collecting the stunned organisms that fall out. It’s linitations are that bark dwellers are not affected by the gas because they are protected by the bark they live under

88
Q

What are the two statistical tests we need to know?

A

Spearman’s rank correlation coefficient and the students T test

89
Q

What is a null hypothesis?

A

the hypothesis that any difference between data sets are the result of chance

90
Q

What are the things you do for all tests?

A
  • you need to come up with a null hypothesis
  • you then need to compare the value you calculated against a critical value from a given table. You should always compare against the numbers in the p=0.05 column
  • if your value is higher than the critical value then you reject the null hypothesis. If it is lower then you accept it
91
Q

What would the format be for the null hypothesis for a student t test?

A

There is no significant difference between …and…

92
Q

How do you calculate the degrees of freedom?

A

(Data set - 1) + (data set -1)

93
Q

What does s, n and _ mean that are found in the

X t test formula?

A

_
X = mean
S = variance (square of standard deviation)
N = number in data set

94
Q

How do you work out standard deviation and so then variance?

A

Standard deviation: (x - _x)2. Then add up all these values, divide by the data set and then square root it

With variance the same but just don’t square root at the end

95
Q

How would you write the conclusion for a succesful t test?

A

My t value of (…) is larger than the critical value of (…) at the p-0.05 confidence lecel. Therefore ai can reject the Null hypothesis and conclude there is a difference between … and … and I can be 95% sure that this did not occur by chance

96
Q

What are the steps for a student t test?

A

1) state the null hypothesis
2) calculate your observed value, t
3) decide whether to accept or reject your null hypothesis

97
Q

What are the steps for a correlation coefficient test?

A

1) state the null hypothesis
2) calculate the correlation coefficient rs (the observed value)
3 decide whether to accept or reject the null hypothesis

98
Q

With the spearmans rank correlation coefficient what do value of +1, 0 and -1 mean?

A
  • a value of +1 indicates that there is perfect positive correlation
  • a value of 0 indicates that there is no correlation between the variables
  • a value of -1 indicates that there is perfect negative correlation

Biology Year 13 (16 decks)

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