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7- Genetics, populations, evolution, and ecosystems > Populations and ecosystems > Flashcards

Populations and ecosystems Flashcards

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1
Q

What is ecology

A

The study of the inter-relationships between organisms and their environment

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2
Q

What are abiotic factors

A

Components of the non-living parts of an ecosystem

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3
Q

What are biotic factors

A

Components of the living parts of an ecosystem.

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4
Q

What is an ecosystem

A

An ecosystem consists of the living (biotic) and non-living (abiotic) components of an area and the interrelationships between them.

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5
Q

What are the two major processes we need to consider within an ecosystem

A

1) The flow of energy through the system
2) The cycling of elements within the system.

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6
Q

Define population

A

A population is a groups of individuals of one species that occupy the same habitat at the same time and are able to interbreed.

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7
Q

What is an ecosystems carrying capacity

A

The size of a population of a species that an ecosystem can support.

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8
Q

What two key things does the size of a population vary as a result of

A

1) The effect of abiotic factors
2) Interactions between organisms, for example intraspecific and interspecific competition and predation.

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9
Q

Define community

A

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

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10
Q

What is a habitat

A

The physical place where an organism lives and the conditions that it lives in (abiotic factors)

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11
Q

What are microhabitats

A

Smaller units within a habitat that each have their own microclimate.

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12
Q

What is an ecological niche

A
  • The specific position occupied by an organism in a particular ecosystem, dependant upon the resources it uses.
  • It includes all the biotic and abiotic conditions to which an organism is adapted in order to survive, reproduce and maintain a viable population.
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13
Q

What is the competitive exclusion principle

A

No two species occupy exactly the same niche.

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14
Q

What type of growth curve do we plot when a population grows in size slowly over a period of time

A

A graph of numbers of individuals in a population against time.

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15
Q

Why can’t we plot a graph of numbers in a population against time for a population such as bacteria that grow rapidly over a short period of time

A

The graph will be an exponential that increases rapidly and makes it difficult to interpret as the graph will quickly run off the scale.

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16
Q

What type of growth curve do we plot for populations that increase in size rapidly such as bacterial populations

A

You plot time against log of bacterial population numbers.

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17
Q

List some factors that may slow the reproduction of bacterial colonies

A
  • Mineral ions are consumed as the population becomes larger.
  • The population becomes so large that the bacteria at the surface are recent light reaching those at deeper levels.
  • Other species are introduced into the pond, carried by animals or the wind, and some of these species may use the bacteria as food or compete for light or minerals.
  • Winter brings much lower temperatures and a much lower light intensity of shorter duration.
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18
Q

What is the carrying capacity of a population

A

The size of the population that can be sustained over a relatively long period

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19
Q

Name the four key abiotic conditions that determine the size of a population

A

1) Temperature
2) Light
3) PH
4) Water and humidity

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20
Q

Describe the effect of temperature not being optimum on the carrying capacity of cold-blooded animals and plants

A
  • In plants and cold blooded animals, as temperature falls below the optimum, the enzymes work more slowly and their metabolic rate is reduced.
  • Populations therefore have a smaller carrying capacity.
  • At temperatures above the optimum, the enzymes work less efficiently because they gradually undergo denaturation.
  • Again, this reduces the populations carrying capacity.
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21
Q

Describe the effect of the temperature not being optimum on warm blooded animals

A
  • Warm blooded animals can maintain a relatively constant temperature regardless of the external temperature.
  • However, the further the temperature of the external environment gets from their optimum temperature, the more energy the organisms expend in trying to maintain their normal body temperature.
  • This leaves less energy for individual growth so they may mature more slowly and their reproductive rate slows.
  • The carrying capacity of the population is therefore reduced.
22
Q

Describe how light affects the carrying capacity of all organisms

A
  • Light is the largest source of energy for most ecosystems.
  • The rate of photosynthesis increases as light intensity increases.
  • The greater the rate of photosynthesis, the faster plants grow and the more spores or seeds they produce.
  • Their carrying capacity is therefore potentially greater.
  • In turn, the carrying capacity of animals that feed on plants is potentially larger.
23
Q

Describe how PH affects populations of organisms

A
  • PH affects the action of enzymes.
  • Each enzyme has an optimum PH at which is operated most effectively.
  • A population of organisms is larger where the appropriate PH exists and smaller, or nonexistent, where the PH is different from the optimum.
24
Q

Describe how humidity affects populations of organisms

A
  • Humidity affects the transpiration rates in plants and the evaporator of water from the bodies of animals.
  • Again in dry air conditions, the populations of species adapted to tolerate low humidity will be larger than those with no such adaptations.
25
Q

What is intraspecific competition

A

Competition between members of the same species.

26
Q

What is interspecific competition

A

Competition that arises between members of different species

27
Q

What are some example of things that individuals may compete for

A
  • Food
  • Light
  • Space
  • Water
  • Light
  • breeding sites
28
Q

What is the competitive exclusion principle

A

The competitive exclusion principle states that where two species are competing for limited resources, the one that uses these resources most effectively will ultimately eliminate the other: no two species can occupy the same niche indefinitely when resources are limiting.

29
Q

What is predation

A

Predation occurs when one organism consumes another.

30
Q

Why are the prey usually exterminated when a predator and its prey are brought together in a laboratory

A

The range and variety of the habitat is limited due to being in a lavatory so the prey is easily caught

31
Q

Why do prey survive predators in the wild when they don’t in the laboratory

A
  • The area over which the population can travel is far greater- the variety of the environment is much greater.
  • This means there are many more potential refuges.
32
Q

Explain the predator-prey relationship

A
  • Predators each their prey, thereby reducing the population of prey.
  • With fewer prey available the predators are in greater competition with each other for the prey that are left.
  • The predator population is reduced as some individuals are unable to obtain enough prey for their survival or to reproduce.
  • With fewer predators left, fewer prey are eaten so more survive and are able to reproduce.
  • The prey population therefore increases.
  • With more prey now available for food,
    The predator population in turn increases.
33
Q

What other factors cause cyclic fluctuations in populations aside from predator-prey relationships

A

Disease and climactic factors

34
Q

Why are periodic population crashes important in evolution

A
  • There is a selection pressure which means that those individuals who are able to escape predators or withstand disease are more likely to survive and reproduce.
  • The population therefore evolved to be better adapted to the prevailing conditions.
35
Q

What is abundance in ecology

A

The number of individuals of a species in a given space. It is often needed to study habitats.

36
Q

What are two key sampling techniques used to study habitats

A
  • Random sampling using frame quadrants or point quadrants
  • Systematic sampling along a belt transect
37
Q

Name the two types of frequently used quadrat

A

1) Point quadrat
2) Frame quadrat

38
Q

Describe what a point quadrat is

A
  • A point quadrat consists of a horizontal bar supported by two legs.
  • At set intervals along the horizontal bar are ten holes, through each of which a long pin may be dropped.
  • Each species that the pin touches is then recorded.
39
Q

Describe what a frame quadrat is

A
  • A frame quadrat is a square frame divided by string or wire into equally sized subdivisions.
  • The quadrat is placed in different locations in the area being studied and the abundance of each species within the quadrat is then recorded.
40
Q

List the three factors to consider when using quadrats

A

1) The size of quadrat to use
2) The number of sample quadrats to record within the study area.
3) The position of each quadrat within the study area.

41
Q

Explain why the size of quadrat to use is important to consider

A
  • The size of the quadrat depends on the size of the plants or animals being counted and how they are distributed in the area.
  • Larger species require larger quadrats.
  • Where a population of species is not evenly distributed through an area, a large number of small quadrats will give more representative results than a small number of large ones.
42
Q

Explain why the number of sample quadrats to record within the study area is important to consider

A
  • The larger the number of sample quadrats, the more reliable the results will be.
  • As the recording of species within a quadrat is a time-consuming task a balance needs to be struck between the reliability of results and the time available.
  • The greater the number of different species present in the area being studied, the greater the number of quadrats are required to produce reliable results for a valid conclusion.
43
Q

Why is the position of each quadrat within the study area important to consider

A

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

44
Q

Describe how to take a random sample with a quadrat

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 or generated by a computer.
3) Place a quadrat at the intersection of each pair of coordinates and record the species within it.

45
Q

Describe how to carry out systematic sampling

A
  • A belt transect can be made by stretching a string or tape across the ground in a straight line.
  • A frame quadrat is laid down alongside the line and the species within it recorded.
  • It is then moved it’s own length along the line and the process is repeated.
  • This gives a record of species in a continuous belt.
46
Q

Describe the two ways of measuring abundance of a species that doesn’t move (when using a quadrat)

A

1) Frequency: The likelihood of a particular species occurring in a quadrat. It is worked out as a percentage of the number of quadrats containing the species over the number of quadrats used.
2) Percentage cover: This is an estimate of the area within a quadrat that a particular plan species covers. It is useful where a species is particularly abundant or is difficult to count.

47
Q

Describe the advantage and disadvantage of using percentage cover as a measure of abundance

A
  • Advantage: Data can be collected rapidly and individual plants to do not need to be counted.
  • Disadvantage: does not work where organisms occur in several overlapping layers.
48
Q

What technique do we use to measure the abundance of moving species

A

Mark-release-recapture

49
Q

Describe the technique of mark-release-recapture

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 individuals in the first sample x total individuals in the second sample) / number of marked individuals recaptured.
50
Q

Describe the assumptions that Mark-release-recapture relies on

A
  • The proportion of marked to unmarked individuals is the same as the proportion 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 into 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.

7- Genetics, populations, evolution, and ecosystems (4 decks)

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