Struggle for Existence pt. 9

Question 1

Autotrophs

Answer 1

also called primary producers, collectively constitute the first trophic level of a community, make their own energy

Question 2

Heterotrophs

Answer 2

consumers

Question 3

second trophic level

Answer 3

herbivorous animals that eat plants (secondary producers or primary consumers)

Question 4

Carnivores

Answer 4

prey on live herbivores, called tertiary producers or secondary consumers

Question 5

Omnivores

Answer 5

consume from more than one trophic level

Question 6

Detritivores

Answer 6

decomposers, extract their carbon from dead organisms

Question 7

The earth is mostly a….

Answer 7

closed system.

Question 8

Where can elements on earth be found?

Answer 8

Oxygen, nitrogen, and carbon are highly mobile elements that are closely tied up with the metabolisms of organisms. Phosphorus and others are trapped in stable insoluble abiotic forms (sedimentary rocks at bottom of ocean)

Question 9

HSS

Answer 9

Green earth hypothesis - because the earth is still green, the third trophic level must inhibit the second so that the first doesn’t get wiped out

Question 10

Counterpoints to Green earth hypothesis

Answer 10

• maybe not all leaves are edible
• only applies to whole trophic levels (does not allow for nuances within trophic levels)
• its actually pretty difficult to identify which trophic level an organism resides on

Question 11

How can we quantify organismal trophic level?

Answer 11

measuring ratios of stable isotopes in its tissues (carnivores almost always turn out to be omnivores)

Question 12

trophic cascades

Answer 12

measurable, important, indirect relationships between two trophic levels that are mediated through a third level (level three indirectly causes increase in level one by depressing level two)

Question 13

Tiffany Knight

Answer 13

dragonfly experiment

Question 14

Why are isolated communities used to test trophic cascades? What are some issues with this?

Answer 14

Small isolated communities allow for removal experiments (top down; actually getting all the secondary consumers out) or bottom up (removing primary producers). Some problems
- negates metapopulation structure and interpatch migration

Question 15

Microcosms and mesocosms

Answer 15

experiment environments (small vs large scale ish)

Question 16

Where are trophic cascades more likely?

Answer 16

Aquatic environments because the habitat is not separated into discrete patches (one homogenous solution with few dispersal barriers). Behave as populations not metapopulations.

Question 17

Folivory

Answer 17

leaf eating

Question 18

Structural defences

Answer 18

thorns, spiky hairs, abrasive silica, physical toughness of sclerophyllous leaves

Question 19

chemical defences

Answer 19

metabolic poisons or deterrents

Question 20

Secondary compounds/metabolites

Answer 20

chemicals not involved in primary processes of a plant (photosynthesis, respiration, etc) rather act as a defence against herbivores

Question 21

Why do some plants lack protective chemicals? What happens to these plants?

Answer 21

Artificial breeding for palatable crops or knockout genes. Makes them highly susceptible to attack

Question 22

Which came first: herbivory or diversification?

Answer 22

Herbivory. Evolutionary arms race between plants and herbivorous insects can lead to local specialization and thus eventually speciation.

Question 23

Developing resistance often leads to

Answer 23

specialization- sometimes the harmful compound even becomes a chemical cue to find the plant, feeding stimulant, a cue for egg-laying, or is incorporated into the insect’s tissue (monarchs)

Question 24

Erlich and Raven

Answer 24

Studied herbivory and diversification. Looked at parallel adaptive radiations.

Question 25

Which is more specialized: interactions that are hostile or not?

Answer 25

Hostile interactions lead to specialization and thus speciation more so than (insects eating or harming plants) milder interactions which are typically more generalized (pollinators and flowering plants).

Question 26

Which lineages have produced more species: carnivorous or herbivorous?

Answer 26

Herbivorous. We can see branching points in the phylogeny of insects where one became herbivorous and one remained carnivorous. Herb. lineages produced more species in same amount of time.

Question 27

Why doesn’t specialization occur in large bodied herbivores?

Answer 27

They can move around in their habitat and make choices as to what it eats (mixed diet/generalists which avoids worst poisons) thus they do not have highly specific detox pathways. Many insects are born and die on same plant thus they must be able to handle plant defences or they will die!!