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Ecotoxicology > Lecture 5 - DA > Flashcards

Lecture 5 - DA Flashcards

1
Q

Name 6 advantages of pesticides.

Name 4 disadvantages.

A 
Advantages
-Effective
-Fast
-Easy to use
-Cheap
-Broad spectrum
-Increases productivity
Disadvantages
-Toxic to humans
-Toxic to non target organisms
-Persistent in the environment
-Pests develop resistance
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2
Q

Name the 5 groups of pesticides.

A 
Organochlorines
Organophosphates
Carbamates
Botanicals
Biologicals
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3
Q

What is the solubility (in water and lipids) of organochlorines like? What about its toxicity? Is it likely to persist in the environment?

A

Low solubility in water, high in lipids.
Toxicity is low-moderate.
Will bioaccumulate due to lipid solubility.

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4
Q

Which is more toxic, organochlorines, or organophosphates?
Which is more persistent?
Which degrades easier (and how)?

A

Organophosphates are more toxic.
However, they do degrade easier.
Organochlorines persist more.

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5
Q

Which is more water soluble, organochlorines or organophosphates?

A

Organophosphates.

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6
Q

Are carbamates more toxic than organochlorines/phosphates?

A

No, less toxic.

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7
Q

Do carbamates take long to degrade? What does this suggest about its persistence?

A

No, they degrade rapidly. Therefore, there are no problems with persistence.

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8
Q

What is the solubility of carbamates like?

A

Is variable.

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9
Q

Where are botanicals derived from?

A

Are pesticides derived from plants.

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10
Q

Are botanicals moderately toxic, or highly toxic?

A

Highly toxic.

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11
Q

Name 3 examples of botanicals.

A

Nicotine, pyrethrum, and pyrethroid.

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12
Q

What are 2 forms of pyrethrin?

A

Pyrethrum - natural form

Pyrethroid - synthetic form

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13
Q

What is one way pesticides can be classified?

A

By their mode of action.

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14
Q

How can analogues of juvenile growth hormones be used as pesticides?

A

Prevents the completion of the life cycle - perpetually in juvenile form.

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15
Q

What are 3 advantages of using juvenile growth hormones as pesticides? Name a disadvantage.

A

Is highly selective
Rapid degradation
Essentially non-toxic to other organisms

However, it will still affect bees.

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16
Q

What do antimetabolite pesticides prevent? What is a consequence of this? Are they highly specific or is there non-target toxicity?

A

Chitin synthesis. Failure to survive moulting.

There is some non-target toxicity.

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17
Q

Name 3 examples of biological pesticides (ie parasites, bacteria etc).

A

Fungi
Nematodes
Bacillus

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18
Q

What are some disadvantages of using biological pesticides?

A

Toxicity of ecotoxins, and affecting non-target insects like bees.
May also affect genetic stability.

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19
Q

Name 3 kinds of herbicides.

A

Triazine herbicides
Urea herbicidea
Phenoxy herbicides

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20
Q

What kind (in terms of persistence and selectivity) and dose of herbicide is needed for permanent removal of all vegetation?

A

High dose of a non-selective persistent herbicide.

21
Q

What kind (in terms of persistence and selectivity) and dose of herbicide is needed for temporary removal of all vegetation?

A

Moderate dose of a non-selective non-persistent herbicide.

22
Q

What kind (in terms of persistence and selectivity) and dose of herbicide is needed for selective removal of some plants, while leaving others?

A

Low-moderate dose of a selective herbicide.

23
Q

How are herbicides taken in by plants? What characteristics are needed by the herbicide to be effectively taken up, and why?

A

Taken in via the leaves and stems above ground, and roots below ground.
Plant is covered by a lipid based cuticle, so the herbicide must be somewhat lipophilic.
Must also be slightly water soluble to be transported once through the cuticle.

24
Q

What are the 3 selectivities of herbicides?

A

Differential uptake
Differential detoxification
Differential root growth habit.

25
Q

What are diuron and linuron herbicides, and what kind of herbicide selectivity do they fall under?

A

Diuron - binds rapidly at soil surface
Linuron - not intensely bound to soil surface
They fall under differential root growth habit selectivity

26
Q

What kind root systems are diurons toxic to? What about linurons? Do they leach?

A

Diurons - shallow root systems. Does not leach.

Linurons - deep root systems. Leaches rapidly.

27
Q

What are triazine herbicides applied to, where are they taken in, and where are they transported to?

A

Applied to the soil, taken in by roots, and transported to the leaves.

28
Q

What effect do triazines have?

A

Accepts electrons produced during photosynthesis, causing lipid peroxidation, and necrosis.

29
Q

How are triazine herbicides detoxified?

A

C1 is replaced with an OH group.

The ring is cleaved.

30
Q

Where are urea herbicides applied to, and what kind of transport does it utilise?

A

Applied to soil, utilises apoplastic transport.

31
Q

What is the binding capacity of urea like?

A

Different types have different capacities.

32
Q

The mode of action of herbicides is most similar to what other herbicide?

A

Similar to triazine herbicides.

33
Q

Name 2 ways urea herbicides are degraded.

A

Bacterial demethylation

UV degradation

34
Q

Are urea herbicides selective or non-selective?

A

Typically non-selective.

35
Q

Are urea herbicides diurons or linurons?

A

Mostly diurons.

36
Q

Phenoxy herbicides are used to control what weed amongst what crop?

A

Controls dicot weeds amongst monocot crops

37
Q

What weed are phenoxy herbicides selective for?

A

Broadleaf weeds.

38
Q

What is the mode of action for phenoxy herbicides?

A

mimics auxin, but isnt degraded.

39
Q

What is the half-life of phenoxy herbicides? After what period of time will there be negligible amounts left?

A

Half-life - days to weeks.

Negligible after a year.

40
Q

Name 2 ways phenoxy herbicides are degraded.

A

Via microbes and UV light.

41
Q

Do chlorophenols degrade? What is a problem with degrading them?

A

They do degrade, but are toxic once degraded.

42
Q

Order in terms of sensitivity to phenoxy herbicides.

Invertebrates, fish, algae

A

Algae - resistant
Invertebrates - more sensitive
Fish - sensitive

43
Q

Is glyphosate toxic to animals? Why/why not?

A

Is non-toxic, as they lack the pathway it affects.

44
Q

Is glyphosate volatile? What is its selectivity and solubility?

A

Non-volatile
Water soluble
Non-selective action

45
Q

Why was glyphosate once considered to be toxic? Why isnt it anymore?

A

Early formation was very toxic. Later found to be due to the surfactants and solvents used, which was removed upon discovery.

46
Q

Can dioxins be degraded by bacteria?

A

Yes, but a long half-life.

47
Q

Do dioxins bind tightly to soil? Does it leach?

A

Binds tightly, and doesnt leach.

48
Q

Where do dioxins accumulate?

A

The liver.

49
Q

What is the major problem with dioxins?

A

Bioaccumulation, and biomagnification.

Ecotoxicology (22 decks)

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