Biodiversity, Species Interactions and Population Control

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Transcript Biodiversity, Species Interactions and Population Control

Species Interactions, and
Population Control
Chapter 5
Where we’ve been…
Chapter 3
◦ Looked at ecosystem components and how energy cycles
within ecosystems
Chapter 4
◦ Defined biodiversity. Looked at factors affecting
biodiversity and how it is measured.
Where we are headed…
Chapter 5
◦ Look at how species interact with each other and how
ecosystems respond to changes in environmental
Species Interactions
Five Major Ways that Species Interact with one
◦ 1. Interspecific Competition
◦ 2. Predation
◦ Symbiosis (two species living closely together)
 3. Parasitism
 4. Mutualism
 5. Commensalism
Interspecific Competition
When two or more species interact to gain access to the
same limited resources (food, water, light, space)
◦ Intraspecific: same species competing for resources
◦ Resource partitioning: species evolve traits to minimize
competition with other species
◦ As our footprint grows larger, we are impacting species even
more (habitat loss)
 Humans competing with other species for space and access to
When one member of a species feeds on a
member of another species
◦ Predator-prey relationship
◦ Predators and prey often co-evolve traits that either allow
them to find prey or hide from predators better
◦ Predators play important roles in ecosystems (help to
keep other species in balance)
Symbiotic Relationships--Parasitism
When one organism lives on or inside of another
◦ Parasite benefits, host organism harmed (not immediately
 Parasite dies if host killed
Symbiotic Relationships--Mutualism
Interaction that benefits both species
◦ Unintentional exploitation of the other organism (not
Symbiotic Relationships-Commensalism
Interaction that benefits one species and has little
or no effect the other
Population Dynamics
Population: group of interbreeding individuals of the same
◦ Most organisms live together in clumps
Changes in population size influenced by:
◦ Births and deaths
◦ Immigration and emigration
◦ Population change= (births + deaths) – (immigration + emigration)
◦ Age structure diagrams can also be used to describe
organism populations
◦ -identify if population is growing, stable or declining
Limiting Factors
Populations have a range of tolerance. A set of physical
and chemical conditions that they will thrive under.
◦ Small variations in a population will exist due to genetic
◦ “optimal range of tolerance”—conditions in which most
organisms survive
◦ Limiting factor principle: too much or too little of any physical or
chemical factor can limit or prevent growth of a population
◦ Examples of limiting factors?
Range of Tolerance
Carrying capacity: maximum number of individuals
an ecosystem can support.
◦ Environmental resistance: combination of all limiting
factors determines carrying capacity
◦ Exceeding carrying capacity causes population to crash
 Overshoot and die off
Population density: number of individuals found in
a particular area
◦ Density dependent limiting factors
 Parasitism, infectious disease, competition
◦ Density independent limiting factors
 Weather events, fire, pollution, habitat destruction
Reproductive Strategies and
R-strategist (type 1)
K-strategist (type 3)
When graphed these two reproductive strategies produce
unique survivorship curves
◦ Many small offspring with little or no parental care
◦ Large losses of young offspring, so produce large numbers to
◦ Examples: algae, bacteria, insects, some fish species
◦ Reproduce later in life, few offspring
◦ Longer lifespan, mature slowly with parental care
◦ Examples: mammals, birds
◦ Classified as type 1, 2 or 3 depending on mortality rates
Type 1: low infant mortality and high survival
Type 2: constant decline
Type 3: high infant mortality few reach adult
Population Calculations
Annual Growth Rate
◦ (CBR-CDR)/ 10 = % growth
** Does not include immigration or emigration
Change in Population per year
Population Density
◦ Population change= (births + deaths) – (immigration + emigration)
(Number of individuals)
/ (area sampled)
Doubling Time
Birth and Death Rates
(births or deaths per year) / (Total Population)
**Crude birth and death rate multiply by 1000
◦ 70/ annual growth rate = doubling time of a population
Response to Ecosystem Change
Ecological Succession: gradual change in species
composition in an ecosystem after a significant
◦ Primary succession: gradual establishment of living
organisms in lifeless areas where there is no soil or
sediment (aquatic)
 bare rock, parking lots, new ponds or reservoirs, cooled lava
 takes a very long time
◦ Secondary succession: series of communities and
ecosystems develop in places containing soil or sediment
 abandoned farmland, burned/logged forests, polluted
streams, flooded land
 can relatively happen quickly
Succession increases species richness and complexity
of food webs
enhances energy flow and nutrient cycling which
promotes increased biodiversity
does follow an unpredictable path
resilience of ecosystems: ability through succession to
rebound to previous state after significant disturbance
◦ rainforests highly complex and diverse, very difficult to return to
previous state
 “Ecological tipping point”—ecosystems won’t recover when past this
Succession and Mt. St. Helens
May 18, 1980
erupted violently
Deadliest and most
destructive volcanic
eruption in US
Eruption reduced
the height of the
mountain by 1300
The Mt. St.
was created to
preserve the
volcano as
well as
provide the
land for
Article Reading and Questions
Read the article: Mt. St. Helens 30 Years Later
Answer the following questions.
◦ Describe the impact of the MSH eruption on the
surrounding ecosystem. Give specific details.
◦ Describe how succession is reshaping the MSH
ecosystem. What has been observed in the past 30+
◦ What are the concerns with the MSH ecosystem looking
toward the future?