Lecture 11: Community ecology: trophic relationships and plant-animal interactions Flashcards
Tropic levels in order
Primary producers
Primary consumers
Secondary consumers
Tertiary consumers
Primary producers
Plants
Primary consumers
Herbivores
Secondary consumers
Predators carnivores who eat herbivores
Tertiary consumers
Carnivores eat secondary consumers
Decomposers
Organism who eat deed organic matter
Food chain vs food web
Food chains show linear path of energy flow
Food web more complex shows all different paths of energy flow
Parasoids
Herbivores of plants
Indirect effect
When affect of one species on another is mediated by third species
Exploitative scramble competition
When organism compete for resources that are in short supply in an ecosystem
Tropic cascades
Interactions between two tropic levels cascade to third tropic level
Why is the world green according to Hairston?
Carnivores keep down herbivores so herbivores do not limit plant growth
Effects of tropic cascades
Affects alternate across tropic levels
Can drastically affect communities
Top down control
Abundances kept low because of predation
Bottom up control
Abundances kept low because of resource limitations
Solids lines on tropic cascade diagrams represent
Direct affects
Dashed lines on tropic cascade diagrams represent
Indirect affects
Take home message from tropic cascade and indirect affects(2)
Indirect affects can be as strong as direct affects
Outcomes not fundamentally predictable rely on strength of interactions
Long term experiment needed
what are the most described species?
plants and animals
why its is hard to be a herbivore
plants tissue is hard to convert to animal tissue
why are plants tissue is hard to convert to animals tissue
Cellulose and lignin are tough, only be digested with help of microbial symbionts
Plant tissues heavily defended against
herbivores
what is responsible for much of biodiversity in terms of plants and insects?
Coevolutionary race
between plants and insect
herbivores
example of how plants defend themselves against herbivores
milkweed
What are Milkweed-feeding specialist? What do they do? why do they do this?
monarch butterfly larva,
cutting leaf midrib to reducesap pressure before eating
how do caterpillars get white sap from milkweed? benefit of this?
sequester it in their
cuticle, making themselves
poisonous and distasteful
Describe Plant herbivore interactions as an arms race.
Plants evolve toxins to reduce herbivore predation
Insects evolve detoxification or other mechanisms to overcome plant defended
Why do we think plants taste okay
Food crops have been artificially selected for low toxicity
Are Secondary chemicals very potent or only a little bit potent?
Especially potent eg alkaloids
What causes arms race
Escalation in defences
What is the coevolutionary race between plants and animals responsible for?
Much of biodiversity
What is the benefit of vertebrate herbivores having mixed diet?
Os they don’t have an over accumulation of one toxin from
the same plant
