Download Chapter 19

Ecology
• The study of how organisms interact with each
other and their environment
Key Elements of the Environment
• Temperature – most organisms require a
narrow range (humans excluded)
• Water – very important, much more diversity
in rainforest than in desert
• Sunlight – where almost all energy originates
from
• Soil – pH, minerals, nitrogen, phosphorus
affect the ability of plants to grow
Population properties
• Population size – number of individuals
• Population density – number of individuals in a
given unit
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Los Angeles – 7544 people/square mile
South Sioux City, NE – 2725 people/square mile
Manila, Philippines – 111,576 people/square mile
New York City – 27,012 people/square mile
• Population dispersion
clumped
uniform
random
Population growth
• Population at current time = population from
past time + births during that time – deaths
during that time + immigration – emigration
– Simulation of population growth – start off with
10 people (5 couples) – each couple has 4 kids
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•
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How many offspring? - 20
20 children become adults and each couple has 4 kids
How many offspring? – 40
Doubles each generation – so let’s draw a graph
Population growth
• Exponential growth – the larger
the population, the more it will
grow
• Eventually this has to stop
– Space
– Availability of resources
• Carrying capacity – the max
population
• This type of growth is called
logistic growth (sometimes called
a sigmoid curve)
Factors that influence population density
• Density-independent events
– Severe weather (floods, drought, etc.)
– Severe geological disturbances (volcanoes,
earthquakes, etc.)
• Density-dependent events
– Aggressive behaviors (defending territory)
– Emigration
Maximizing population productivity
• Demand for fish has increased due to general health benefits and increase in
global population
• Overharvesting has caused population decline in wild salmon
• Salmon farms have helped alleviate the problems of overharvesting
• Farms have negative health and ecological impact
– Toxins in fish
– Fish lice and viruses are becoming common if farmed salmon, which are passing
them on to wild salmon
overharvesting
Wasting resources
Maximum sustainable
yield
Demography
• The study of populations using statistics
• Cohort – A group of individuals that are the
same age
• Fecundity – Number of offspring produced in
a standard time (for example, a year)
• Mortality – The number of individuals that die
in that time
• Proportion of males to females is called the
sex ratio
Survivorship curve
• Type I – Most live a long
time, then suddenly die
• Type II – constantly die
off
• Type III – many die off
young, the ones that
survive live for quite
some time
Community and Ecosystem
• Community - all the species in a given area
• Ecosystem – all the species and all the nonliving components in a given area
The Niche and Competition
• Niche – all the ways in which an organism uses
its habitat
• Habitat – the place where an organism lives
• Competition – when two organisms attempt
to use the same resource
– Interspecific – between two different species
– Intraspecific – between the same species
Fundamental Niche vs. Realized Niche
Fundamental Niche – where a given species is ABLE to live
Realized Niche – where a given species actually lives because of competition
Competition
Population
• Competitive exclusion - If two species are competing for the same
resource, the one that uses it more efficiently will out grow the
other
Time
P. Bursaria grown separately
• No two species can occupy the same niche if resources are limited. If two
species coexist…
• Resources are not limited
• They do not occupy the same niche
Resource partitioning
• Competition between two species is rare in
nature because of 2 reasons:
– One would outcompete OR
– A new niche would be formed by dividing up
resources – resource partitioning
• Sympatric – closely related species that divide up resources
– must live close to each other
• Allopatric – closely related species that do not divide up
resources – so usually do not live close to one another
• Allopatric species look more alike than sympatric species –
called character displacement
Character Displacement
• Character
displacement is not
the same as
disruptive selection
Coevolution
• Symbiosis – two organisms that live together
and whose existence is altered because of this
relationship
– Mutualism – both benefit
– Commensalism – one benefits, other is unharmed
– Parasitism – one benefits, other is harmed
• Sometimes parasitism can be considered a predatorprey relationship
Predator/Prey cycles
• Predation – the consuming of one organism by
another
– Predator – the one doing the eating
– Prey – the one being eaten
Defense against predators
• Plants
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–
–
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Thorns
Spikes
Prickles
Chemicals (pungent tastes usually associated with toxicity)
Many others
• Animals
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–
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–
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Poisons
Warning coloration
Camouflage
Speed
Many others
Mimicry – a type of defense
• Batesian mimicry – non-harmful organism mimics the look
of a harmful organism
• Mullerian mimicry – similar pattern development between
harmful organisms
• Self-mimicry – one body part looks like another body part
Mullerian
Batesian
poisonous
Non-poisonous
venomous
Mullerian
Ecological succession
• Succession – more complex communities
replace simpler ones as time goes on
– Primary Succession – occurs on a substrate that
never had life prior
• Examples: volcanoes, rocks, lakes left by glaciers
– Secondary Succession – occurs on a substrate that
had life prior, but was almost completely wiped
out
• Deforestation, flood, fire