Zonation of Rocky Shores

Question 1

what is zonation?

Answer 1

patterns of organisms on sea shore

Question 2

what causes the vertical gradient of zonation?

Answer 2

• physical factors-> heat, stress, desiccation, wave shock
• biological factors -> reduced feeding time, gas exchange, competition, predation

Question 3

how does heat stress/desiccation affect zonation?

Answer 3

• varies on small spatial scales
• reduction of SA/vol = reduces heat gain and water loss
• evaporation cooling aids heat loss
• well-sealed exoskeleton aid in retarding water loss
• location affects which animals can survive

Question 4

what are the adaptations to prevent desiccation?

Answer 4

• shape (spherical retains moisture)
• aggregate (A. elegantissima)
• cover surface in sand and shells
• evaporative cooling

Question 5

how does wave shock affect zonation?

Answer 5

• abrasion: from particles in suspension
• pressure: breaking waves can crush structures
• drag: can pull organisms off surface and carry organisms from burrows

Question 6

what kind of organisms have less time to feed?

Answer 6

higher intertidal organisms

Question 7

what forms grow more slowly than lower intertidal organisms?

Answer 7

sessile

Question 8

what kind of organisms feed more effectively in lower intertidal regions?

Answer 8

mobile carnivores

Question 9

when can sessile animals not feed?

Answer 9

unless submerged

Question 10

what kind of animals cannot respire at low tide?

Answer 10

intertidal animals

Question 11

what state to respiratory organs need to be in order to acquire oxygen?

Answer 11

moist

Question 12

what do animals do at low tide?

Answer 12

reduce metabolic rate

Question 13

what do high intertidal animals do?

Answer 13

some can respire from air even at low tide if air is not too dry (mussels)

Question 14

what is the adaptation of Pacific sand bubbler crab?

Answer 14

• membrane on each leg for gas exchange

Question 15

what is the adaptation of Leather limpet?

Answer 15

carries air bubble into tide pools

Question 16

how is a vertical zonation physically formed?

Answer 16

physiological tolerance of diff species at diff levels of shore

Question 17

how is a vertical zonation biologically formed?

Answer 17

• larval and adult preference -> larvae may settle at high tide at high levels, mobile juv/adults have series of behavioral responses that keep them at certain levels of shore
• competition -> species may be capable of excluding others from certain levels of shore
• predation -> mobile predators more effective usually lower shore (affects distributions of vulnerable prey species

Question 18

what is the point of the Connell’s field experiment?

Answer 18

interspecific competition

Question 19

describe the Connell’s field experiment

Answer 19

• barnacle Chthamalus highest on shore
• barnacle semibalanus below that
• below mean low water, barnacles are rare
• mobile predators, gastropod snail Nucella are more common in lower regions

Question 20

what happened when transplanted newly settled Chthamalus to all tidal levels?

Answer 20

• took rock with barnacles and moved them to lower intertidal
• found another barnacle species (Semibalanus) grew over it or squeezed it off rocks

Question 21

what happens when some transplants are caged in lower intertidal zone?

Answer 21

• to exclude Nucella
• found Semibalanus grew fine in cages

Question 22

what were the results of Semibalanus and Chthamalus?

Answer 22

• semi not tolerant of higher zones
• chtha better recruiting to high intertidal zones
• chtha competed out of lower zones
• semi eaten by snails in lower zones

Question 23

what conclusions were drawn from the Connell experiment?

Answer 23

• physical factors control upper limit of distribution
• biological factors control lower limit of species occurrence -> predation important for lower intertidal

Question 24

what allows for recruitment into a lower zone?

Answer 24

• disturbance
• competition or predation will determine who survives

Question 25

what does predation do?

Answer 25

open up space for recruitment of competitively inferior species

Question 26

what maintains diversity?

Answer 26

predation

Question 27

what was Paine’s keystone species concept?

Answer 27

• removing Pisaster ochraceus allows for Mytilus californianus recruitment
• other species reduced in abundance bc M. californianus became dominant
  —–> P. ochraceus is keystone species

Question 28

what is a keystone species?

Answer 28

species presence has strong effects on community organization mediated by factors such as competition and predation

Question 29

what does a small disturbance on a mussel bed allow?

Answer 29

• allows the mussels to move and close off the opening

Question 30

what happens when there is a large disturbance to a mussel bed?

Answer 30

causes it to be colonized by other species and patch can last months of indefinitely

Question 31

what does a spatial scale disturbance affect?

Answer 31

spatial pattern of dominance of species, creating a mosaic of long-lived patches

Question 32

what happens when larvae recruitment is variable?

Answer 32

competitively superior species might not take over, owing to low rates of recruitment

Question 33

when does reduced recruitment occur?

Answer 33

• currents not favorable
• heavy rain washes larvae from shore
• warm temps mean poor year for phytoplankton = poor year for success of plankton feeding larvae

Question 34

what determines upper limit?

Answer 34

physical: physiological tolerance of species
- desiccation and wave action

Question 35

what determines lower limit?

Answer 35

biological: larvae and adult preference and competition and predation