predation pt 4 (herbivory->interrelation between plants, herbivores, carnivores)

how do predators select prey?

they select based on size + shape

→ this acts as a form a natural selection

the presence of a predator changes the behavior of prey. when prey reduce their activity to avoid being detected, what predator activity do they reduce? what does this reduction affect?

foraging activity

→ this affects prey growth + development

________ is a form of predation, but it does not kill the individual being fed on

herbivory

what interaction is a key component of all communities?

autotroph-herbivore interactions

what are the effects of herbivory (specifically grazing)?

1) biomass consumed → not necessarily the best measure

2) reduced vigor of the plant due to loss of foliage and subsequent loss of roots

3) reallocation of plant energy to replace leaves and shoots eaten by herbivores → less allocated to growth and reproduction

4) increased vulnerability to insects and disease

why are grasses generally tolerant to grazing?

their meristem is close to the ground, so they can continually grow by the bottom of the plant

how can grazing help grass?

can stimulate production by removing older tissue functioning at a lower rate of photosynthesis

what characteristics have plants evolved to prevent herbivory

1) structural defenses

→ hairy leaves, thorns, spines

2) chemical defenses/making themselves low-quality food

→ tannins, bad taste

→ high in cellulose or lignin makes it hard for herbivores to digest

secondary compounds

chemicals produced by plants that either reduce the ability of herbivores to digest plant tissue or deter herbivores from feeding

→ nitrogen-based compounds (alkaloids)

→ terpenoids (essential oils)

→ phenolics: aromatic compounds that include tannins + lignins

what are the 2 types of inhibitors of secondary compounds?

1) quantitative inhibitors

2) qualitative inhibitors

quantitative inhibitors

secondary compounds produced by the plant in large quantities to reduce digestibility

→ tannins + resins (make up 60% of the dry weight of leaves)

→ lignin (make up 5-35% of the carbon in leaves)

qualitative inhibitors

secondary compounds present in small/minute quantities + function as defenses against herbivores

→ cyanide by poisoning

→ alkaloids (nicotine, caffeine, cocaine, morphine, mescaline) by reducing appetite

what adaptations do herbivores have to avoid plant defenses?

1) detoxification + storage

2) behavioral changes

how do herbivores use detoxification + storage to avoid plant defenses?

some insects can detoxify themselves and store the plant’s poisons in their body so they can digest

what behavioral change have some insects developed so they can avoid plant defenses?

some insects sever the veins of the leaves BEFORE feeding on the plant to stop the flow of chemical defenses 

plants are consumed by herbivores → herbivores are consumed by what?

carnivores