Herbivory Flashcards

1
Q

What is herbivory?

A

The consumption of whole plants (primary producers) or plant material, by animals known as primary consumers.

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2
Q

What is the total global biomass?

A

550 billion tonnes.

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3
Q

Why are plants not always the most nutritive food?

A

Plants have low nitrogen content and herbivores have to eat a lot of it and be efficient at digesting.

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4
Q

What are some adaptations that are required for herbivores to digest plants?

A

The right shape and size for best access to the plants, strong jaws and durable teeth and a large rumen to digest cellulose using symbiotic micro-organisms.

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5
Q

What is the difference between specialist and generalist herbivores?

A

Specialists feed on one type of plants whereas generalists can feed on multiple types of plant.

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6
Q

What impact do herbivores have on plant populations?

A

They can reduce plant growth rate and reduce plant reproductive output

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7
Q

How can herbivores reduce plant reproductive output?

A

They can directly reduce it as seed predators or indirectly reduce it by reducing plant biomass.

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8
Q

What is an example of herbivorous insects that can defoliate forests?

A

The spruce budworm.

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9
Q

What is an example of an area that was affected by cattle grazing?

A

Mauna Loa Volcano, Hawaii.

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10
Q

In what ways can herbivores affect diversity?

A

Herbivores that prefer dominant plants can increase diversity whereas herbivores that prefer subordinate plants can decrease diversity.

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11
Q

How do herbivores impact the ecosystem?

A

They produce a large amount of CO2.

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12
Q

What are some of the positive effects herbivores might have?

A

They can induce plant growth and be valuable controllers of invasive plants.

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13
Q

What is an invasive species?

A

A species new to an area where it grows unchecked - lack of competitors or/and parasites or/and herbivores.

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14
Q

What is an example of an invasive species?

A

The prickly pear cactus and cactus moth. The cactus moth controlled the prickly pear when it was introduced to Australia.

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15
Q

What is another example of an invasive species in California?

A

The Klamath weed that was controlled by a leaf beetle.

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16
Q

How can invasive species be brought under control?

A

A specialised herbivore.

17
Q

Why have all the plants in the world not been eaten already?

A

They have mechanical defences such as leaf toughness, spined leadf margins, thorns, spines and are covered by wax.

18
Q

What are some of the phenological defenses plants have?

A

Producing an excess of seeds (mast fruiting) so the predators become full before eating all of the seeds.

19
Q

What are some of the hormonal defences plants have?

A

Reproductive inhibition to prevent some insect herbivores from developing.

20
Q

What are some of the biochemical defenses plants have?

A

Secondary chemicals (not needed for development) such as THC in marijuana, mustards and tobacco that are nitrogenous secondary compounds to deter predators.

21
Q

Why do plants produce a combination of several chemical defenses?

A

Synergism (producing a greater effect) and there are many herbivores.

22
Q

What are constitutive defenses?

A

They are expressed at all times.

23
Q

What are induced defenses?

A

The expression is increased (or turned on) after attack.

24
Q

Are detrivores classed as herbivores?

A

No

25
Q

Example of how herbivores increase plant growth?

A

Clipping can induce fruit production - field gentians Gentianella campestris.

26
Q

What is the genetic basis of plant defence against herbivores?

A

Herbivores eat plants lacking defence genes - when a defense gene was silenced, 92% of the plants were attacked by herbivores.

27
Q

What is the problem with producing multiple defence chemicals?

A

It may be expensive.

28
Q

Why might plants have induced defences instead of constitutive defences?

A

The cost of defence is too high to maintain under light herbivory.