UNIT 13
Chapter 50: An Introduction to Ecology & the Biosphere
Chapter 51: Behavioral Biology
Chapter 52: Population Ecology
Chapter 53: Community Ecology
Chapter 54: Ecosystems
Chapter 55: Conservation Biology
Introduction

Ecology is the scientific study of the
interactions between organisms and their
environment


Ecologists make predictions of what should be
observed in the environment
Environment of any organism includes the
following components:
–
–
Abiotic factors: non-living chemical and physical
factors (temperature, light, water, and nutrients)
Biotic factors: the living components
Levels of Ecology

Organismal: behavioral and physiological
ways individuals
interact with the
environment

Population: a population is a group of
individuals of the same species living in a
particular geographic area
–
Population ecology examines factors that
affect population size and composition

Community:
a community consists
of all the organisms of
all the species that
inhabit a particular
area
–
Community ecology
examines the interactions
between populations

predation, competition,
and disease

Ecosystem: an ecosystem consists of all
the abiotic factors in addition to the
entire community of species that exist in
a certain area
–
Ecosystem ecology:


energy flow
cycling of chemicals
Temperature & Water

Climate is the prevailing weather conditions
in an area
–

Temperature, water, light, and wind are major
components of climate
Climate determines the makeup of biomes
–
Major types of ecosystems

Ex. Desert, tundra, tropical rain forest, grassland, etc.

Annual means
for temperature
and rainfall are
reasonably well
correlated with
the biomes we
find in different
regions

The tropics between 23.5° north latitude and 23.5° south
latitude experience the least seasonal variation and have the
highest biodiversity
END
Introduction
 Ethology is the study of how animals behave
in their natural environment
 Behavior results from both genes and
environment

Innate behaviors are fixed, the result of genetics
Learning
 Learning is based on experience and
results in modification of behavior


Maturation: changes resulting from growth
and development
Habituation: desensitization to unimportant
stimulus
 Imprinting is a short
period of learning
early in life


Usually involves
young recognizing
(and becoming
attached to)
parents
Konrad Lorenz
experimented with
geese
 Classical conditioning is a type of
associative learning

Animals learn to associate one stimulus
with another
 Ivan


Pavlov experimented with dogs
Ring bell and spray powdered meat in their
mouths caused salivation
Eventually, the bell alone caused salivation
 Operant conditioning involves trial and
error

Association with a punishment or reward
Cognition
 Cognition is the ability to perceive, store,
process and use information from
sensory receptors



Kinesis: change in activity based on
random behavior
Taxis: movement/orientation based on a
stimulus
Migration: long-distance movements that
occur regularly
Organism Interactions
 Social behavior is any interaction
between animals (usually the same
species)


Agonistic: conflict, usually no harm done
Dominance hierarchies: involve ranking of
individuals
 Alpha
organism dominates group
 Courtship consists of behaviors that lead
to copulation


Monogamous – strong bond between male
and female
Polygamous – multiple mates exist
– female with multiple males
 Polygyny – male with multiple females
 Polyandry

Promiscuous – no lasting bond between
males and females
Inclusive Fitness
 Most social
behaviors are
selfish, but some
involve helping
others

Altruism decreases
individual fitness,
but increases
fitness of group
 Related individuals will often help each
other survive and/or reproduce

Kin selection: individuals help relatives
raise young
END
Introduction
A population is a group of the same
species that inhabit the same general
area
 Density and distribution are influenced
by organisms’ interactions with the
environment

Survivorship Curves

Demography is the study of the factors
that control the growth and decline of
populations
– Survivorship curves reflect births and deaths
in a population
 Curve
types: Type I, Type II, Type III
Population Growth
The exponential model reflects unlimited
resources for growth
 The logistic model incorporates limiting
factors into population growth

– N is the number of individuals
– Carrying capacity (K) is the maximum
number of individuals that can be supported
naturally

Two basic types of species exist based
on reproductive traits
– K selection

organisms live/reproduce around K
– Long maturation, long lifespan, low deathrate, few
offspring, several reproductions in life
– r selection

populations fluctuate well below K
– Short maturation, short lifespan, high deathrate,
many offspring, one reproduction

Limiting factors fall into two categories
– Density dependent
factors increase their pressure as population
grows
 type of negative feedback

– Density independent


factors unrelated to population size, no feedback
Negative feedback prevents unlimited
population growth

Some populations go through regular
“boom and bust” cycles
– Common with predator/prey interactions

Age structure is the relative number of
individuals at each age
END
Introduction
• A community is a collection of species living
closely enough for potential interaction
• Interspecific
interactions
involve
relationships
between
species
• An organism’s niche is its biotic and abiotic
requirements from its environment
• Its role in the environment
• Organisms with identical niches cannot coexist
(competitive exclusion principle)
Interspecific Interactions
• Competition, mutualism, commensalism and
predation (parasitism) are examples of
interspecific interactions
• Predator/prey interactions have “forced”
evolution to develop ways to protect prey
species from their predators
• Coloring, camouflage, toxins, mechanical
defenses, etc.
• Herbivory is a type of predation
• Coloration and camouflage are frequently
used by nature to aid prey avoid being
eaten
• Aposematic
Cryptic coloration
Batesian
Müllerian
mimicry
mimicry
coloration
–– atraditional
two
harmless
– (or
warning
more)
camouflage,
species
colors
“dangerous”
to
deceptive
indicate
resembles
species
have
the
markings
apresence
harmful
evolvedone
of
to a
resemble
toxin
one another
Trophic Structure
• Food chains and
food webs are
used to trace the
path of energycontaining carbon
compounds
Disturbance & Succession
• Disturbances affect community structure
and stability
• Stability is the ability of a community to persist
• Events like fire, weather, natural disasters
and human activity can disturb a community
• Some events are routine, while others occur
randomly
• Usually considered to have a negative impact,
but actually necessary for development and
survival
• Humans are the most widespread source of
disturbance and it usually results in a
decrease in species diversity
• Succession is the sequence of changes that
occur after a disturbance
• Primary succession – occur in a lifeless area
• Soil needs to be created first by mosses and lichens
• Secondary succession – occur when an area is
cleared by an event
• Soil still exists, grasses and small shrubs grow
END
Trophic Relationships
• Trophic
relationships involve
the cycling of
carbon in an
ecosystem
• Primary producers
are photosynthetic
• All consumers
depend on
photosynthetic
output
Primary Production
• Amount of light energy converted to
chemical energy in a given time period
is called primary production
• Ecosystems vary in their productivity
Secondary Production
• Amount of chemical energy converted
into a consumer’s biomass is secondary
production
• Joules (J) are unit
of energy
• Trophic efficiency is typically ~10%
• Amount of energy passed to next trophic
level
• Trophic efficiency has important
implications for humans
Human Impact
• Human activity disrupts biogeochemical
cycles
• Nutrients removed from one part of
biosphere and placed in another
• Agriculture and
eutrophication
• Acid precipitation threatens plants and
aquatic organisms
• Caused by burning fossil fuels
• Toxins
introduced
into a food
web become
more
concentrated
in successive
trophic levels
• Biological
magnification
• Human activities
were depleting
atmospheric
ozone (O3)
• Ozone protects
Earth from UV
radiation
• Use of CFC’s is
likely cause
• Climate change
occurs due to
rising CO2
levels in the
atmosphere
• Greenhouse
effect causes
global warming
END