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Biology unit 4 > Populations > Flashcards

Populations Flashcards

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1
Q

What is meant by abiotic?

A

Non-living components such as temperature and rainfall.

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2
Q

What is meant by biotic?

A

Living components such as competition and predation.

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3
Q

What is meant by the biosphere?

A

The life-supporting layer of land, air and water that surrounds the earth.

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4
Q

What is an ecosystem?

A

An ecosystem is made up of all the interacting biotic and abiotic features in a specific area.

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5
Q

What are the two major processes to consider within an ecosystem?

A

The flow of energy through the system and the cycling elements within the system.

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6
Q

What is a population?

A

A population is a group of interbreeding organisms of one species in a habitat.

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7
Q

What is a community?

A

All the populations of different organisms living and interacting in a particular place at the same time.

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8
Q

What is a habitat?

A

A habitat is the place where a community of organisms lives. Within an ecosystem, there are many habitats such as the leaf canopy of the trees in an oak woodland.

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9
Q

What is an ecological niche?

A

A niche describes how an organism fits into the environment. A niche refers to where an organism lives and what it does there. It includes all of the biotic and abiotic conditions required for an organism to survive, reproduce and maintain a viable position.

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10
Q

What is abundance?

A

The number of individuals of a species within a given space.

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11
Q

Give two sampling techniques used in the study of habitats.

A

Radnom sampling using frame quadrats of point quadrats, and systematic sampling along transects.

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12
Q

What are the three factors to consider when using quadrats?

A

The size of the quadrat to use, the number of sample quadrats to record within the study area, and the position of each quadrat within the study area.

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13
Q

Why does the size of the quadrat need to be considered?

A

Larger species require larger quadrats etc.

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14
Q

Why does the number of sample quadrats to record within the study area need to be considered?

A

The larger the number of sample quadrats, the more reliable the results will be. The greater the number of different species present in the area being studied, the greater the number of quadrats required to produce valid results.

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15
Q

Why does the position of each quadrat within the study area need to be considered?

A

To produce statistically significant results, random sampling must be used.

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16
Q

Why is random sampling important?

A

It prevents any bias in collecting data.

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17
Q

Why is it important to avoid bias?

A

Avoiding bias ensures that the data obtained is valid.

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18
Q

Give a method of random sampling.

A
  1. Lay out two long tape measures at right angles, along two sides of the study area.
  2. Obtain a series of coordinates by using random numbers taken from a table of generated by a computer.
  3. Place a quadrat at the intersection of each pair of coordinates and record the species within it.
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19
Q

When is systematic sampling along transects particularly useful?

A

Where some form of transition in the communities of plants and animals takes place, for example, the distribution of organisms on a tidal seashore is determined by the relative periods of time that they spend under water and exposed to the air, that is, by their vertical up the shore.

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20
Q

What is a line transect?

A

A line transect comprises a string or tape stretched across the ground in a straight line. Any organisms over which the line passes is recorded.

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21
Q

What is a belt transect?

A

A strip, usually a metre wide,, marked by putting a second line parallel to the first. The species occurring within the belt between the lines are recorded.

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22
Q

What ways can abundance be measured?

A

The frequency, or the percentage cover.

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23
Q

What is frequency?

A

The likelihood of a particular species occurring in a quadrat.

24
Q

What is the frequency of it’s occurrence if a species occurs in 15 out of 30 quadrats?

A

50%.

25
Q

What is percentage cover?

A

An estimate of the area within a quadrant that a particular plant species covers.

26
Q

What is the method of frequency useful for?

A

When a species, such as grass, is hard to count. It gives a quick idea of the species present and their general distribution within an area.

27
Q

What is the method of frequency less useful for?

A

It does not provide information on the density and detailed distribution of a species.

28
Q

What is the method of percentage cover useful for?

A

Where a species is particularly abundant or is difficult to count. The advantages in these situations are that data can be collected rapidly and the individual plants do not need to be counted.

29
Q

When is the method of percentage cover less useful?

A

When organisms occur in several overlapping layers (more probably plants).

30
Q

What must you do to obtain reliable results?

A

It is necessary to ensure that the sample size is large, that is, many quadrats are used, and the mean of all the samples is obtained. The larger the number of samples, the more representative of the community as a whole will be the results.

31
Q

What technique is required to estimate the abundance of most animals?

A

Mark-release-recapture techniques.

32
Q

What is the method of mark-release-recapture techniques?

A

A known number of animals are caught, marked in some way, and then released back into the community. Some time later, a given number of individuals is collected randomly and the number of marked individuals is recorded. The size of the population is then calculated as follows;
estimated population size = total number of individuals in the first sample x total number of individuals in the second sample
/ number of marked individuals recaptured.

33
Q

What assumptions does the mark-release-recapture technique rely on? (6)

A

The proportion of marked to unmarked individuals in the second sample is the same as the proton of marked to unmarked individuals in the population as a whole.
The marked individuals released from the first sample distribute themselves evenly amongst the remainder of the population and have sufficient time to do so.
The population has a definite boundary so that there is no immigration not or emigration out of the population.
There are few, if any, deaths and ‘births’ within the population.
The method of marking is not toxic to the individual nor does it make the individual more conspicuous and therefore more liable to predation.
The mark or label is not lost or rubbed off during the investigation.

34
Q

What needs to happen to collected data?

A

It needs to be analysed and interpreted.

35
Q

What is standard deviation?

A

The spread of data about the mean.

36
Q

What can be checked statistically?

A

Whether chance alone is the reason for the differences between two sets of data.

37
Q

What is a positive correlation?

A

Where an increase in the value of one variable is accompanied by an increase in the value of the other variable.

38
Q

What is a negative correlation?

A

Where an increase in the value of one variable is accompanied by a decrease in the value of the other variable.

39
Q

What is meant by population size?

A

The number of individuals in a population.

40
Q

What are the three phases for the usual pattern of growth for a natural population?

A
  1. a period of slow growth as the initially small number of individuals reproduce to slowly build up their numbers.
  2. a period of rapid growth where the ever-increasing number of individuals continue to reproduce. The population size doubles during each interval of time, as seen by the gradient of the curve which becomes increasingly steep.
  3. a period when the population growth declines until its size remains more or less stable. The decline may be due to the food supply limiting numbers or to increased predation. The graph therefore levels out with only cyclic fluctuations due to variations in factors such as food supply or the population size of predators.
41
Q

After a rapid increase in population size, why may it begin to slow or cease altogether?

A
  • The population becomes so large that they begin to get in the way of important resources, i.e. an increase in algae population size at the surface of the water may prevent light from reaching algae below the surface
  • Other species may be introduced which may eat them, or compete with them for resources. Inter and intraspecific competition.
  • Changes in seasons cause changes in temperatures and light intensities etc.
42
Q

What are the two basic types of various limiting factors that affect the size of a population?

A

Abiotic and biotic factors.

43
Q

Abiotic - how does temperature influence population size?

A

Each species has a different optimum temperature at which its best able to survive. The further away from this optimum temperature, the smaller the population that can be supported. In plants and cold-blooded animals, as temperatures fall below the optimum, the enzymes work more slowly. At temperatures above the optimum, the enzymes work less efficiently as they gradually denature. Again, the population grows more slowly.
The warm-blooded animals can maintain a relatively constant body temperature regardless of external temperature. The further the temperature of the external environment gets from their optimum temperature, the more energy these organisms expend in trying to maintain their normal body temperature. This leaves less energy for individual growth and so they mature more slowly and their reproductive rate slows. The population size therefore gets smaller.

44
Q

Abiotic - how does light influence population size?

A

Light is the ultimate source of energy for ecosystems. the rate of photosynthesis increases as light intensity increases. The greater the rate of photosynthesis, the greater the rate of growth in plants and the more seeds they produce. Their population growth and size is therefore potentially greater. In turn, the population of animals that feed on plants is potentially larger.

45
Q

Abiotic - how does pH influence population size?

A

This affects that action of enzymes. Each enzyme has an optimum pH. A population of organisms is larger were the appropriate pH exists.

46
Q

Abiotic - how does water and humidity influence population size?

A

Humidity affects transpiration rates in plants and the evaporation of water from the bodies of animals. In dry conditions, the populations will be adapted to tolerate them and those that can’t will be scarce.

47
Q

When does competition occur?

A

When two or more individuals share any resource that is insufficient to satisfy all their requirements fully.

48
Q

What is intraspecific competition?

A

When competition arises between members of the same species.

49
Q

What is interspecific competition?

A

When competition arises between members of different species.

50
Q

Give an example of intraspecific competition in oak trees.

A

In a large population of small oak trees, some will grow larger and restrict the availability of light, water, and minerals to the rest, which then die. In time, the population will be reduced to relatively few large dominant oaks.

51
Q

What is meant by competitive exclusion principle?

A

If one species has a competitive advantage over the other, and the conditions remain the same, this will lead to the complete removal of one species. This is known as the competitive exclusion principle.

52
Q

What is predation?

A

Predation occurs when one organism is consumed by another.

53
Q

Why is predation different in real life circumstances rather than lab conditions?

A

There are many more potential refuges and many of the prey can escape predation, so although the prey population falls to a low level, it rarely becomes extinct.

54
Q

What is the advantage of lab studies on predation?

A

It is difficult to obtain reliable data on natural populations because it is not possible to count all the individuals in a natural population. Its size can only be estimated from sampling and surveys.

55
Q

How does predator-prey relationship affect population size?

A

Predators eat prey which reduces the population of prey. With fewer prey available, predators have to compete for reminding prey. Predator population is then reduced as some individuals are unable to provide enough prey for their survival. With fewer predators left, fewer prey are eaten. The prey population therefore increases. With more prey now available as food, the predator population also increases.

56
Q

Why might the effects of predator-prey relationship often be less severe?

A

Because in natural ecosystems, organisms eat a range of foods rather than just one particular species.

Biology unit 4 (8 decks)

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