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IOB U2 > Populations > Flashcards

Populations Flashcards

1
Q

Define Biomagnification

A

The process by which chemicals are retained in the bodies of organisms becoming more concentrated at each trophic level

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2
Q

How does biomagnification occur?

A

Biomagnification occurs when the organisms at the next trophic level consume many contaminated individuals.

The high order consumers in a food chain are most affected by biomagnification

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3
Q

What is bioaccumulation?

A

The increase in the concentration of a substance in certain tissues of an organism and occurs at each trophic level.

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4
Q

What are 4 chemicals that accumulate in organisms?

A

hydrocarbons including pesticides such as DDT
Industrial polychlorinted biophenyls (PCBs)
Heavy metals such as lead and mercury
And biocides such as TBT tributyl tin.

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5
Q

Define density

A

Density - number of organisms per unit area.

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6
Q

Define abundance

A

Abundance- number of organisms in the population

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7
Q

Define Distribution

A

Distribution- where a population of a species is spread within an ecosystem

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8
Q

What are 3 different types of distribution?

A

Random distribution

Uniform distribution

Grouped/clumped distribution

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9
Q

What is random distribution?

A

Individuals are irregularly spaced in the environment.
Presence/absence of other members of the population does not influence distribution

Examples often are plants rather than animals

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10
Q

What is uniform distribution?

A

Even spacing of individuals in the environment.
The presence of other individuals often determines the position of others

Eg. penguins

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11
Q

What is grouped/clumped distribution?

A

Individuals are grouped together
presence of one individual increase the likelihood of finding another individual

Eg. herding animals and social animals

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12
Q

Overall population growth =

A

Overall population growth = (B+I) – (D+E)

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13
Q

Factors that affect populations (4 main)

A

Biotic
Abiotic
Density Dependent
Density Independent

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14
Q

Define Abiotic and give examples

A

Non living or physical and chemical factors that can affect the survival of an organism.

Include: temperature, light intensity, humidity, availability of water, presence of gases oxygen and carbon dioxide, pH (acidity of water), water turbidity or cloudiness etc.

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15
Q

Define Biotic and give examples

A

The living or biological factors that can affect the survival of an organism.
These include: competition (intraspecific and interspecific), predation, parasitism, disease, collaboration, commensalism and mutualism.

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16
Q

What are 2 different types of populations?

A

Natural: organisms in the wild

Artificial: organisms that are kept or planted on a farm, zoos and enclosures by humans such as sheep, cows and wheat

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17
Q

Define population size

A

Population size = the total number of organisms in the population.

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18
Q

Define population distribution

A

Population distribution = the location of organisms within an area.

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19
Q

Define population density

A

Population density = number of organisms per unit area (terrestrial) or volume (aquatic).

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20
Q

What are 8 factors affecting population?

A

Supply of resources which:
factors in an environment which an organism needs or depends upon, they are usually finite (a scarce amount of each, some cannot be replaced or recycled)
Examples include: food, water, light, minerals, oxygen and fuels.
Amount of waste products and pollution
Level of disease: including parasites
Predators: limit the population size and density
Breeding and nesting sites or areas: may depend upon the type of soil and presence of rocks or specific types of plants.
Climate: rainfall, wind, temperature
Availability of shelter
Competition: interspecific and intraspecific

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21
Q

What are density dependent factors influenced by?

A

Influenced by population density or the level of crowding in the population (biotic factors) eg. food supply, disease, parasites, competition and predation

These factors have greater effect when the population density is higher and less impact when the population density is low.

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22
Q

Give an example of how density dependent factors effect other biotic factors

A

If there is crowding (high density) there will be increased competition for food, shelter, mates and increased transmission of disease and parasites. As well, organisms are easily found by predators.

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23
Q

How does density independent affect organisms?

A

Affect all individuals in a population equally
Some organisms may be better equipped to cope with these factors than others (abiotic)

Rainfall, temperature, humidity and catastrophes such as droughts, fire and flood

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24
Q

Describe the factors contributing to the population growth of an introduced organism into a new environment

A

Result of the balance of two major opposing factors potential and environmental resistance

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25
Q

Define environmental resistance

A

Environment resistance is the effect of essential factors which reduce a population growth rate, when in short supply. eg. food, water, shelter, space

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26
Q

What is biotic potential?

A

Biotic potential is the maximum rate at which the population can increase, assuming ideal conditions. (other definition: unrestricted reproductive capacity of any population)

27
Q

What are 4 factors that affect biotic potential?

A

Several factors that affect biotic potential:

Age at which an organisms first reproduces
frequency with which reproduction occurs,

average number of offspring produced each time

Length of organisms reproductive life span

Death rate of individuals under ideal conditions

28
Q

What happens to biotic potential if there is no environmental resistance?

A

Without environmental resistance, biotic potential leads to exponential growth.

29
Q

What is carrying capacity?

A

Carrying capacity

The limit of biotic potential set by environmental resistance (point of stable population - some oscillation)

30
Q

What is population crash?

A

Population crash

when a population drastically exceeds carrying capacity causing a severe depletion

31
Q

What is exponential growth?

A

Exponential growth is a pattern of continuously accelerated increase in population size

32
Q

Environmental resistance can be caused by density dependent factors or density independent factors. Explain.

A

Environmental resistance can be caused by density dependent are biotic factors such as food supply and density independent factors are abiotic factors such as altitude, as these essential factors that affect population growth rate. If one of these effects are in short supply, this can cause a reduction in population growth rate.

33
Q

What happens when populations becoming established?

A

They undergo exponential growth, If resources of the new habitat are endless (inexhaustible), then exponential growth would continue.

34
Q

Why is exponential growth rare in natural populations?

A

This is rarely the case in natural populations which encounter environmental resistance. They may increase exponentially at first and the flattened out to an equilibrium (the carry capacity) around which it fluctuates

35
Q

Why do fluctuations occur in graph changes in population size?

A

Irregular up and down movements due to changes in conditions and organism activity
Appear to be random and can be caused by changes in predation, competition, climate and food supply

36
Q

Why do cycles occur in graph changes in population size?

A

Changes in the environment that recur regularly
eg. old and weak may tend to die in winter due to cold and because they find it hard to compete for limited food; on the other hand, births may occur in spring when water and food are abundant.

37
Q

When do S curves occur in graph changes in population size and what occurs?

A

Introduction of one or a few individuals into a new suitable area.

Population explosion occurs where initially, there are a few organisms and so reproduction is slow but accelerates in increase in population. Births exceed deaths.
In the next phase, there is an ample amount of food and space and the large number of reproducing organisms leads to rapid population increase. Many more are born than dying.
The last phase, food, space or build up of wastes become limited as the population size approaches the carrying capacity of the area.
When deaths equals births, the carrying capacity has been reached the curve is a straighten parallel to the X axis.

38
Q

What occurs in first phase of the S curve?

A

Population explosion occurs where initially, there are a few organisms and so reproduction is slow but accelerates in increase in population. Births exceed deaths.

39
Q

What occurs in the next phase of the S curve?

A

In the next phase, there is an ample amount of food and space and the large number of reproducing organisms leads to rapid population increase. Many more are born than dying.

40
Q

What occurs in the last phase of the S curve?

A

The last phase, food, space or build up of wastes become limited as the population size approaches the carrying capacity of the area.
When deaths equals births, the carrying capacity has been reached the curve is a straighten parallel to the X axis.

41
Q

What occurs in a J curve?

A

It starts as an S curve, but the population explosion is so rapid than an essential resource is used up, leading to a rapid decline in population size or die off.

Alternatively, a disease might strike a densely packed population, spreading easily, and so decimate the population; or the build-up of toxic wastes may poison the whole populations.

42
Q

What occurs in the first part of the Predator/prey cycles?

preY

A

Prey

  • Plenty of food
  • Birth rate increases
  • Population size increases
43
Q

What occurs in the second part of the Predator/prey cycles?

predator

A

Predator

- increase in prey/food supply, therefore more predators breed and increase in population size

44
Q

What occurs in the third part of the Predator/prey cycles?

preY

A

Prey

- More predators, therefore increase in predation of prey and decrease in prey population

45
Q

What occurs in the fourth part of the Predator/prey cycles?

predator

A

Predator

  • Decrease in prey/food
  • Therefore breeding of predators and decrease in populations
46
Q

What occurs in the fifth part of the Predator/prey cycles?

preY

A

Prey
- decrease in populations of predators as increase in prey as more prey can breed, therefore increase in population of prey

47
Q

What is ecological succession?

A

A transition in species composition of a biological community as species begin to inhabit barren ground or reclaim a disturbed community.
Succession occurs over a long period of time

48
Q

What is primary succession?

A

Colonisation of a sit that has never before sustained life

Eg. new volcanic island, sand dunes

49
Q

What are the firsts things that occur in primary succession?

A

Begins with few pioneer species inhabiting the area, usually being autotrophic prokaryotes.
These organisms the makes the conditions of the region suitable for the next colonisers (fungi, algae and lichen)

50
Q

What are the second things that occur in primary succession?

A

Lichens are then replaced by mosses and so on. These plants alter the environment conditions changing the abiotic factors, assisting in soil development.

Allows pioneer plants to be replaced by plants more adapted to less severe conditions, eg. Vascular plants such as grasses and herbs

51
Q

How do plants help with the soils distinctive characteristics in primary succession?

A

The roots of these plants bind the soil and the presence of decomposers etc increase the organic matter content, altering the soil pH and changing soil nutrients.

Thus the soil will develop with distinctive characteristics. This provides suitable conditions for the germination of the seeds of the larger plants.

52
Q

What do shrubs and then trees do the soil in primary succession?

A

They become established with roots pushing further down into the soil and breaking the deep rock layers.

The accumulation of plant debris helps form a deeper soil layer and eventually tree dominated community.

53
Q

What occurs in the early stages of primary succession?

A

Stages show great species diversity as new species arrive and become established. (high productivity)
As competition eliminates many of the early pioneers with shrubs and trees becoming more dominant, species diversity drops with a corresponding drop in productivity.

54
Q

What does primary succession lead to? And how is this defected by Plants and shrubs?

A

Primary succession leads to reduced erosion as the roots of plants bind soil and prevent wind erosion.

Plants also provide a windbreak, reducing the speed of the wind over the ground and thus making it harder for loose particles to become airborne.

Shrubs develop and the ground becomes shaded which reduces evaporation and allows the soil to hold more water.

55
Q

What is secondary succession?

A

Occurs when all life in an area has been destroyed e.g. due to fire, hurricane, tsunami or cleared for farming and then abandoned.

There are already seeds in the soil and some organic matter.

56
Q

What are going to be the first plants in the area?

A

Grasses are likely to be the first plants in the area, as the seeds could have been blown in by wind or carried by animals.
Some plants roots may have survived destruction and therefore can regrow.
Succession continues with shrubs and trees leading to a stable community at equilibrium. This results in a climate community

57
Q

Why is re-vegetation faster than in primary succession?

A

Re vegetation is much faster than in primary succession as the soil is already present in some cases. Bushfires often add ash which returns nutrients to the soil making it more fertile.

58
Q

What happens if the region is prone to frequent destruction (such as bush fires)

A

If the region is prone to frequent destruction such as bushfires, the composition of the community may change with fire resistant species becoming more common and becoming the dominant plant species.

59
Q

When does Primary and Secondary succession occur?

A

Primary: Begin with no life
Secondary: Follows the removal of existing biota

60
Q

Is soil present for Primary and Secondary succession?

A

Primary: No soil present
Secondary: Soil already present

61
Q

What type of area do primary and secondary succession occur on?

A

Primary: New area (volcanic island)
Secondary: Old area (eg. following a bush fire)

62
Q

What are the pioneer plants of each primary and secondary succession?

A

Primary: Lichen and moss comes first
Secondary: Seeds and roots already present

63
Q

Is biomass low or high for primary succession and secondary succession?

A

Primary: Biomass is low
Secondary: Biomass is higher

IOB U2 (8 decks)

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