DIVERSIFICATION: biotic/abiotic interactions: MARINE REEFS

Question 1

symbiosis between algae and corals

Answer 1

• reef building corals require light because of their symbiotic relationship with unicellular eukaryotic algae living in their tissue
• provides corals with resources they invest in calcification
• stressed corals expel their symbionts, results in coral bleaching

Question 2

encrusting (calcification form)

Answer 2

occurs in turbulent water, sturdiest against waves

Question 3

Branching (calcification form)

Answer 3

occurs in quiet waters, form stacks of plate-like structures

Question 4

Eukaryotic Sex

Answer 4

Lots of effort is spent searching for and winning over a mate, putting the organism at risk of predation.

Only half of the population is capable of generating offspring.

Question 5

mitosis

Answer 5

2 daughter cells identical to the parent

Question 6

benefits and costs of sexual reproduction

Answer 6

benefits: more variation so if if environment fluctuates a population is more resilient

cost: may disrupt beneficial genetic combinations and lower the mean fitness of offspring.
- also there are separate sexes they must find mates and only half the population generates offspring

Question 7

coral growth

Answer 7

Most coral grow as a colony of clones ,

where a single larva that is the product of sexual reproduction settles to the seafloor and clones asexually.

After reaching a state of maturity, these coral can reproduce sexually as well.

• after violent storms fast growing colonies can grow back as clonal colonies from broken fragments
• more sturdy and massive corals are less easily damaged by storms and damage by storms is not as easily repaired

Question 8

wide dispersal corals

Answer 8

• corals that are good dispersers release huge numbers of gametes into the water, the larvae carried by currents to new areas
• some species, the larva can survive 10-12 weeks of transport

Question 9

brooding corals

Answer 9

• produce fewer sperm and eggs
• but more often than wide dispersal
• hold fertilized eggs within the community
• release larvae that settle close to the parent colony

Question 10

How do reefs cope with dropping sea level change?

Answer 10

Corals reproduce sexually and disperse oceanward forming a “red layer”.

Reefs that are exposed to open air die, but can be recolonized as the sea level rises again.

Question 11

In steady sea level conditions: (what do reefs do)

Answer 11

reefs advance “oceanward” but are limited by the muddy seafloor.

Their ultimate growth is fostered by colonizers who pave the way for them by making crusty outcrops on the mud where corals can calcify.

Question 12

what do recent reefs tell us?

Answer 12

-reefs have successfully coped with the rapid sea level and climate change of glaciations

-some species bleach (lose symbionts) when seawater warms and many do not recover
BUT: some acquire new symbionts to cope

-precarious future, hard to predict, likely that rare species will go extinct

Question 13

How does reef building over geological time illustrate major themes of this course?

Answer 13

–Physical factors: (wave energy, light) impose natural selection for similar growth shapes in very different reef-building organisms (e.g. cyanobacteria, sponges and corals). The match of form to function is a broadly predictable outcome of natural selection.

–History: specialization (growth forms, requirements of well-lit water, water temperature, salinity, pH) limits the potential of most reef building organisms to colonize or adapt to a rapid change in their environment. They compensate by reproducing and dispersing to new areas.

–Chance: through time, new organisms may be quicker to take advantage of this marine ecological niche when environmental change drives reef-builders to extinction.