Introduction

Question 1

give four examples of why nature is complicated

Answer 1

1. so much diversity of organisms that all have different life histories, feeding or environmental requirements, morphology, behaviours, etc.
2. diversity is embedded in complex abiotic conditions that include variation in light, nutrients, temperature, etc.
3. nature exists within a variety of time and space - seasonal, decadal trends and migrations, endemism, etc.
4. anthropogenic change creates variation

Question 2

What is a food web?

Answer 2

a scheme that represents feeding relationships of organisms

Question 3

Why are food webs important?

Answer 3

almost all ecological interactions are founded in feeding (trophic) ecology
- all organisms require energy and the acquisition of nutrition drives an organism’s ecology and behaviour
- provides information about energy and nutrient flows in ecosystems

Question 4

What 2 things does understanding food web structure help us with?

Answer 4

1. understanding ecosystem change
2. creating management and conservation guidelines

Question 5

how come removing one species changes an entire ecosystem?

Answer 5

ex. sharks, wolves, sea otters

ecosystem collapse

Question 6

What are some classic methods for determining who eats whom?

Answer 6

1. gut content analysis
2. gastric lavage
3. scat analysis
4. direct observation

Question 7

What are the downsides of using gut content analysis?

Answer 7

gut contents are mostly just ‘piles of goo’ - difficult to handle and look at

some food will be digested more quickly than others and leave less trace behind = may not be that informative

partial digestion

takes a lot of time to look through microscope images

just tells you what the organism last ate, not what it always eats = ex. doesn’t correct for opportunistic feeding

invasive and fatal

animal size creates a potential issue

Question 8

What are the pros of gut content analysis?

Question 9

What are the pros and cons of the gastric lavage method?

Answer 9

PROS:
non-lethal , but still stressful (capturing, anaesthetics)

CONS:

invasive - stomach is pumped

only really useful for larger animals (mammals, seabirds)

same issues as gut content analysis
- only shows organisms last meal = not necessarily representative of diet

Question 10

What are the pros and cons of the scat analysis method?

Answer 10

PROS:
- non-invasive and non-stressful for the animals

CONS:
- focus on terrestrial only
- indicates only what the organism got rid of (excreted), not necessarily what they ingested - not everything leaves a trace in excrement
- digestion is not the full picture
- only works for some organisms

Question 11

What are the pros and cons of the direct observation method?

Answer 11

PROS:
- eye witness is helpful for determining what organisms are ingesting
- non-invasive

CONS:
- can’t follow an organism around 24/7
- only applicable for some organisms (ex. deer, but not deep sea fish)

Question 12

What are the 2 things are important for newer methods of food web ecology?

Answer 12

1. food web tracers to track interactions in the food web
2. frameworks for summarizing complex information

Question 13

What are the pros and cons of the food web tracers?

Answer 13

PROS:
- easy and cheap to measure
- provide meaningful information - diet, trophic levels, etc.
- applicable to wide range of organisms, regardless of size
- non-invasive, non-lethal
- they can be obtained regardless of age, life history, taxonomy

CONS:
- can be complicated

Question 14

What are some examples of new methods?

Answer 14

1. stable isotope tracers
2. fatty acid tracers
3. ecological stoichiometry - framework
4. metabolic theory of ecology - framework
5. nutritional geometry - framework
6. nutritional physiology - framework

others exist like molecular techniques and genomics (both tracers and frameworks)