Herbivores

Question 1

what is herbivory

Answer 1

consumption of whole plants/plant material

Primary consumers

Question 2

Herbivores important

Answer 2

Pass energy from plants to rest of the community

Question 3

Why aren’t all animals herbivores

Answer 3

• plants have low N content, herbivores have to eat lots and v inefficient at digesting
• herbivores have to run from carnivores
• hard to find food

Question 4

why is it different for humans

Answer 4

food selected has high nutritional value and digestability

Question 5

special adaptions of herbivores

Answer 5

• right size and shape of mount appendages
• limb appendages enable organism to access best part of the plant
• strong jaw, durable teeth, bill
• large rumen ( food goes around multiple times)eg in cows to digest cellulose, using symbiotic microorganisms

Question 6

specialists

Answer 6

eat only specific plants

Question 7

generalists

Answer 7

eat whatever plants are available

Question 8

herbivores effect on plants

Answer 8

reduce plant growth rate
reduce plant reproductive output:
- seed predators
-indirectly decr biomass, reduce amount of energy plants can invest in reproduction

Question 9

herbivores that prefer dominant plants

Answer 9

incr diversity bc attack most common species , so other plants have opportunity to grow

vice versa for less common species

Question 10

crops high in nutrition value attract

Answer 10

pests, hence herbivores have an impact on our ability to grow crops

Question 11

positive effects of herbivores

Answer 11

• link shown - herbivores incr production of crops
• because plants have adapted to the fact that they will be eaten eg plants evolving to save reproduction for later the season/ produce branches later, when fewer people pests present

Question 12

herbivores as biological control

Answer 12

can be valuable controllers of invasive plants

invasive plants new to areas can often go unchecked because no plants/ parasites/ herbivores

Question 13

in the case of biological control it’s v important to use

Answer 13

specialised herbivores

Question 14

phenological defence

Answer 14

mast fruiting- produce fruit every 3/5 years
swamps seed predators
don’t flower every year- herbivores die and can’t specialise, so by the time the plants produce lots of fruit the herbivore pop is low

Question 15

hormonal defence

Answer 15

produce chemicals resembling hormones which crash populations of insects eg by ensuring larvae don’t develop into adults

Question 16

biochemical defence

Answer 16

secondary chemicals produced by the plant which aren’t useful to the plant except to fight insects- however some insects have found ways use the chemicals to benefit themselves

Question 17

GM

Answer 17

genes are being identified to reduce plant attacks
knock out certain genes- see what causes more herbivore damage
Introduction of beneficial genes into plants to incr survival / decr damage

Question 18

Bt crops

Answer 18

very effective but have a selective pressure on insects so correlation between use of bt crops and and number of insects resistant to toxins over time

Question 19

constitutive

Answer 19

being expressed all the time

Question 20

induced

Answer 20

expression turned on after attack