Coral Ecology
Coral reefs
• Coral reefs are hard, wave-resistant structures composed of individual
coral animals (polyps)
• Individual coral polyps:
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Are about the size of an ant
Are related to jellyfish
Feed with stinging tentacles
Live attached to the sea floor in large colonies
Construct hard calcium carbonate structures for protection
Contain symbiotic photosynthetic zooxanthellae algae
Coral reef distribution and diversity
Coral reef zonation
Coral Ecology
• Ecology = the study of the interaction of organisms with their
environments.
• It involves understanding biotic and abiotic factors influencing the
distribution and abundance of living things.
• The word "ecology" coined from Greek word "oikos", which means
"house" or "place to live”.
The Scope of Ecology
• population growth
• competition between species
• symbiotic relationships
• trophic (=feeding) relationships
• origin of biological diversity
• interaction with the physical environment
Population Growth
Idealized models predict patterns of population growth
▪ The rate of population increase under ideal
conditions is called exponential growth. It can be
calculated using the exponential growth model
equation, G = rN, in which
• G is the growth rate of the population,
• N is the population size, and
• r is the per capita rate of increase (the average
contribution of each individual to population growth).
▪ Eventually, one or more limiting factors will restrict
population growth.
Population size (N)
500
450
400
350
300
250
200
150
100
50
0
0 1 2 3 4 5 6 7 8 9 10 11 12
Time (months)
Idealized models predict patterns of population growth
• The logistic growth model is a description of
idealized population growth that is slowed by limiting
factors as the population size increases.
• To model logistic growth, the formula for exponential
growth, rN, is multiplied by an expression that
describes the effect of limiting factors on an
increasing population size.
• K stands for carrying capacity, the maximum
population size a particular environment can sustain.
(K − N)
G = rN
K
Breeding male fur seals
(thousands)
10
8
6
4
2
0
1915
1925
1935
Year
1945
Multiple factors may limit population growth
• The logistic growth model predicts that population
growth will slow and eventually stop as population
density increases.
• At increasing population densities, densitydependent rates result in
• declining births and
• increases in deaths.
Multiple factors may limit population growth
• Intraspecific competition is
• competition between individuals of the same species for
limited resources and
• is a density-dependent factor that limits growth in natural
populations.
Multiple factors may limit population growth
• Limiting factors may include
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food,
nutrients,
retreats for safety, or
nesting sites.
100
Survivors (%)
80
60
40
20
0
20
40
60
80
100
120
Density (beetles/0.5 g flour)
Multiple factors may limit population growth
• In many natural populations, abiotic factors such as
weather may affect population size well before
density-dependent factors become important.
• Density-independent factors are unrelated to
population density. These may include
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fires,
storms,
habitat destruction by human activity, or
seasonal changes in weather (for example, in aphids).
Number of aphids
Exponential
growth
Apr May Jun
Sudden
decline
Jul Aug Sep Oct Nov Dec
Month
EVOLUTION CONNECTION: Evolution shapes life histories
• The traits that affect an organism’s schedule of
reproduction and death make up its life history.
• Key life history traits include
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age of first reproduction,
frequency of reproduction,
number of offspring, and
amount of parental care.
Evolution shapes life histories
• Populations with so-called r-selected life history
traits
• produce more offspring and
• grow rapidly in unpredictable environments.
• Populations with K-selected traits
• raise fewer offspring and
• maintain relatively stable populations.
• Most species fall between these two extremes.
© 2012 Pearson Education, Inc.
K-Selected Species
• Poor colonizers
• Slow maturity
• Long-lived
• Low fecundity
• High investment in care for the young
• Specialist
• Good competitors
r-Selected Species
• Good colonizers
• Reach sexual maturity rapidly
• Short-lived
• High fecundity
• Low investment in care for the young
• Generalists
• Poor competitors
Competition Among Species
• Ecological Niche Concept
• Ecological niche = the "role" a species "plays" in the ecosystem.
• Contrast the ecological niche with the "habitat" which is the physical
environment in which the organism lives.
• The ecological niche of a species, therefore, includes not just the
species’ habitat, but also the ways in which it interacts with other
species and the physical environment.
Competition Among Species
• Competitive Exclusion Principle
• No two similar species occupy the same niche at the same time.
• Possible outcomes of competition
• extinction of one species
• resource partitioning: splitting the niche
• character displacement: two similar species evolve in such a way as
to become different from each other by accentuating their initial
minor differences
Keystone Species
• A species whose presence in the community exerts a significant
influence on the structure of that community.
Keystone Species
Keystone Species
Human as Hyperkeystone
Ecological Succession
• The progressive change in the species composition of an ecosystem.
Ecological Succession
• Bare Substrate
• Colonizing Stage Successionist Stage
• Climax Stage
Trophic Levels
• 1st Trophic Level = Primary Producers
• 2nd Trophic Level = Herbivores or Primary Consumers
• 3rd Trophic Level and Higher = Carnivores or Secondary (or higher)
Consumers
• Highest Trophic Level = Top Carnivore
• Decomposers
Some Feeding Types
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Algal Grazers and Browsers
Suspension Feeding
Filter Feeding
Deposit Feeding
Benthic Animal Predators
Plankton Pickers
Corallivores
Piscivores
Omnivores
Scavengers
Overview: Chemical Cycles
Biogeochemical cycles_________________
The various material circuits, which involve both the nutrient
and physical components of an ecosystem.
Carbon, Nitrogen, Phosphorous and Water are needed by
every organism on Earth. C is needed to build organic
molecules. N is needed for nucleic acids. P is needed for
energy molecules. Water is needed to maintain life. How
does every organism on Earth have access to these limited
resources?
Chemical Cycling
Carbon cycle
Nitrogen cycle
Phosphorous cycle
Water cycle