Lecture 2

Question 1

name some biotic factors which structures communities?

Answer 1

competition, predation, parasitism, disease, behavioural interactions

Question 2

name some abiotic factors which structures communities?

Answer 2

physical disturbance and controls on distribution

Question 3

physical factors which affect stream communities scales of influence?

Answer 3

potential for colonization
trophic related to catchment
species related to microhabitat

Question 4

trophic structure?

Answer 4

relationships between feeding groups

Question 5

when does competition?

Answer 5

when individuals compete for a resource in limited supply

Question 6

2 forms of competition?

Answer 6

• exploitation and interference

Question 7

Exploitation competition

Answer 7

where food or space are limited

Question 8

Interference competition

Answer 8

aggressive interactions between competitor species/individuals

Question 9

Resource partitioning

Answer 9

when species co exist by portioning a resource but not in direct competition

Question 10

what type of species is Baetis?

Answer 10

• a fugitive species

- good colonizer, poor competitor

Question 11

why do some prey only drift at night?

Answer 11

to avoid being seen by predators

Question 12

snags?

Answer 12

woody material fallen into rivers e.g. branches

Question 13

where are predators found?

Answer 13

in all predators

Question 14

relationship between midgefly and caddisfly?

Answer 14

• decreased no. caddisflies, increase in midgefly

Question 15

what factors affect prey selection?

Answer 15

• size
• activity
• time of drifting
• contrast/visibility
• prey vulnerability

Question 16

How do prey reduce encounter rates? (4)

Answer 16

• spatial segregation
• use of refuges
• temporal segregation
• low movement rates

Question 17

how do prey reduce attack and capture rates?

Answer 17

• detect and flee, see the predator and move very quickly

Question 18

Name some postcontact morphological features of prey?

Answer 18

• armor, hardened plates and spine

Question 19

Name some postcontact behaviourall features of prey?

Answer 19

• aggressive response

- thanotsosis

Question 20

what is thanotosis?

Answer 20

a behavioural mechanism by prey organisms where they play dead in hope the predator will release them

Question 21

What is aposematism?

Answer 21

the advertising by an animal to potential predators that it is not worth attacking or eating

Question 22

How does baetis avoid being attacked?

Answer 22

• moves very rapidly so can flee when attacked

Question 23

How do water mites use aposematism?

Answer 23

• use of bright red body colouration to war predators

Question 24

where are gerridae (water striders found)

Answer 24

• in vegetation where fish present

- on open water where fish absent

Question 25

The effects of tout presence on baetis mayflies risk of predation?

Answer 25

- accelerate larval development, - resulting in metamorphosis of younger and smaller individuals - minimizing the risk of predation at the expense of fecundity

Question 26

fecundity?

Answer 26

- number of offspring

Question 27

Issue of organisms emerging more quickly at a smaller size?

Answer 27

- adults will produce less eggs

Question 28

order of energy in pyramaid?

Answer 28

- plants at base, providing all energy - fed on by herbivores - predators - top predators

Question 29

What occurs in the absence of predators?

Answer 29

- herbivores aren't under pressure, more of them | - no. plants decrease

Question 30

influence of grazing on periphyton growing on stones

Answer 30

- reduce amount of vegetation ons tone surface - opens up new patches - algae move in - range of species

Question 31

when is the peak production of periphyton?

Answer 31

when intermediate amount of grazing occurs

Question 32

What does the 'harsh-benign' concept of Peckarsky?

Answer 32

- gradient of streams form harsh to benign physically

Question 33

describe a benign environment?

Answer 33

lower levels of disturbance, environment allows for well developed competition/predation effecs

Question 34

what is understood by disturbance?

Answer 34

any relatively discrete event in time that removes organisms and opens up space that can be colonized by individuals of the same or different species e.g flood, pollution

Question 35

How are species diversity and level of disturbance related?

Answer 35

the higher the level of disturbance, the species richness decreases

Question 36

What is the effect of moderate disturbance on species diversity?

Answer 36

you find both competitive and fugitive species | maximum species diversity

Question 37

what is the patch dynamics concept (PDC)?

Answer 37

- disturbance continually opens up patches for colonization and succession and this turnover of patches explain the function of ecosystems

Question 38

Competitive dominant species?

Answer 38

poor colonizers, good competitors

Question 39

Ruderal species features (5)

Answer 39

weed species produce lots of species grow very rapidly similar to fugitive

Question 40

What is a fugitive species?

Answer 40

- good colonizer | - poor competitor

Question 41

What is a subsidy?

Answer 41

- a subsidy of energy or material between different environments e.g. terrestrial> freshwater

Question 42

Effects of salmon on pristine glacial streams formed by retreating?

Answer 42

- inputs of nutrients C,N and P | - causes growth of alga, riparian vegetation

Question 43

Effects of carcasses on the bank?

Answer 43

- decay enriches the soil with nutrients and potentially enhances riparian vegetation

Question 44

terrestrial invertebrates preferences in the year?

Answer 44

more abundant and active in summer months

Question 45

terrestrial invertebrates preferences in the day?

Answer 45

the afternoon

Question 46

What type of source are terrestrial invertebrates?

Answer 46

allochonous source

Question 47

What is the effects of availability of allochtonous food source on predation?

Answer 47

- can lead to predator increase or predator switching

Question 48

Human intervention on reciprocal subsidies?

Answer 48

- removal of riparian vegattaion | - channel modification

Question 49

limitation of TBI and BMWP biological monitoring methods?

Answer 49

only for organic pollution

Question 50

benefit of WHPT biological monitoring method?

Answer 50

used as a general measure of pollution (not specific for just organic)