Download Water Resources

CHAPTER
5
Evolution and Community
Ecology
Lesson 5.1 Evolution
Scientists have identified
and described
over 1.5 million species.
Millions more
have yet to be discovered.
Objectives
• Describe the four primary mechanisms of biological
evolution
• Describe how speciation and extinction affect the
diversity of life on Earth
Lesson 5.1 Evolution
Evolution and Natural Selection
• Gene: A sequence of
DNA that codes for a
particular trait
• Gene pool: All the genes
present in a population
A starting population of fish. Genes control
the color and pattern of the fish’s scales.
• Biological evolution:
The change in a
population’s gene pool
over time
Lesson 5.1 Evolution
Mechanisms of Biological
Evolution: Mutation and Migration
Mutation
Accidental change in DNA
that can give rise to
variation among individuals
Migration (gene flow)
Movement of individuals into
(immigration) or out of (emigration)
a population
Lesson 5.1 Evolution
Mechanisms of Biological
Evolution: Genetic Drift and
Natural Selection
Genetic Drift
Evolution that occurs by chance
Natural Selection
Process by which traits useful for
survival and reproduction are passed on
more frequently than those that are not
Lesson 5.1 Evolution
Conditions of Natural Selection
(1) Organisms
produce more
offspring than can
survive.
(2) Individuals vary in
characteristics, some
of which are heritable.
(3) Individuals vary in
fitness, or reproductive
success.
Did You Know? Darwin privately
researched natural selection for two
decades before publishing On the Origin of
Species.
Conditions of Natural Selection
• Individuals vary in their fitness
• Fitness describes how reproductively successful an organism
is in its environment
• A heritable trait that increases an individual’s fitness is called
an adaptation
• Survival of the Fittest
• Individuals of high fitness produce more offspring and
therefore pass on its genes more frequently
• An organism that is “fittest’’ in one place and time may not be
the fittest forever
Checkpoint
• What is the connection between adaptations and
fitness?
Lesson 5.1 Evolution
Artificial Selection
• Selection under human direction
• Throughout history, humans have chosen and bred
animals and plants with beneficial traits.
Checkpoint
• What is the difference between artificial selection and
natural selection?
Lesson 5.1 Evolution
Speciation
•
Process by which new
species are generated
•
Can occur in a number
of different ways; the
most important way is
called allopatric
speciation (geographic
separation)
•
Has resulted in every
form of life on Earth—
today and in the past
Allopatric Speciation
Allopatric Speciation
• One population broken into multiple smaller isolated
populations
• Separation may be due to glacial ice sheets, rivers changing
course, dry climate, etc.
• Any mutations that arise in one population can’t
spread to the other; genetic divergence occurs
• Populations may become different enough that they
can no longer mate with each other; speciation has
occurred
Lesson 5.1 Evolution
Extinction
• The disappearance of species
from Earth
Trilobites
Marine arthropods that went extinct at
the end of the Permian period.
Did You Know? During the Permo-Triassic
extinction 250 million years ago, 70% of all
land species and 90% of all marine species
went extinct.
• Generally occurs gradually,
one species at a time, when
environmental conditions
change more rapidly than the
species can adapt
(background extinction rate)
• There are five known mass
extinction events, each of
which wiped out a large
proportion of Earth’s species.
Objectives Revisited
• Describe the four primary mechanisms of biological
evolution
• Describe how speciation and extinction affect the
diversity of life on Earth
Writing Prompts
• On a separate sheet of paper, complete the following
statements.
• The four primary mechanisms of biological evolution are…
• The three conditions needed for natural selection to occur
are…
• The process by which new species are generated is called…
• The disappearance of a species from Earth is called…
• MAKE SURE TO WRITE THE PROMPT ITSELF ALONG
WITH YOUR COMPLETION!
• Will be collected
Lesson 5.2 Species Interactions
The zebra mussel has completely
displaced 20 native mussel species in
Lake St. Clair.
Objectives
• Discuss the factors that influence an organism’s niche
• Compare and contrast predation, parasitism, and
herbivory
• Describe mutualism and commensalism
Lesson 5.2 Species Interactions
The Niche
•
Describes an organism’s use of resources and functional role in a
community
•
•
•
Includes organisms habitat, food it eats, how/when it reproduces,
and what other organisms it interacts with
Affected by an organism’s tolerance—its ability to survive and reproduce
under changing environmental conditions
•
Organisms with restricted tolerances – specialists
•
Organisms with wide tolerances - generalists
Often restricted by competition
•
Competition within a species – intraspecific competition
•
Competition among 2 different species – interspecific competition
QuickTime™ and a
decompressor
are needed to see this picture.
Lesson 5.2 Species Interactions
Competition
• Organisms compete when
they seek the same limited
resource.
• In rare cases, one species
can entirely exclude another
from using
resources.(competitive
exclusion)
QuickTime™ and a
decompressor
are needed to see this picture.
• To reduce competition,
species often partition
resources, which can lead to
character displacement.
Resource Partitioning
Competition
• The full niche of a species is called its fundamental niche
• Without competitors an organism can use its entire
fundamental niche
• A niche restricted by competition is called a realized niche
• Realized niche represents only a portion of what an
organism can do and what resources it can use.
• Resource partitioning – a process that allows different
species to share common resources.
• Character displacement – when resource partitioning leads
to the evolution of physical characteristics among
competing species that reflect their specialized roles in the
environment.
Checkpoint
• How does resource partitioning affect competition
between species?
Lesson 5.2 Species Interactions
Predation (+/–)
•
The process by which a predator hunts,
kills, and consumes prey
•
Causes cycles in predatory and prey
population sizes
•
Defensive traits such as camouflage,
mimicry, and warning coloration have
evolved in response to predator-prey
interactions.
•
Some predator-prey relationships are
examples of coevolution, the process by
which two species evolve in response to
changes in each other.
Rough-Skinned Newt
Did You Know? A single roughskinned newt contains enough
poison to kill 100 people.
Unfortunately for the newt, its
predator, the common garter
snake, has coevolved
resistance to the toxin.
Lesson 5.2 Species Interactions
Parasitism and Herbivory (+/–)
• Parasitism: One
organism (the parasite)
relies on another (the
host) for nourishment or
for some other benefit
Hookworm (a parasite)
Did You Know? One study of Pacific estuaries
suggests that parasites play an important role in
keeping these ecosystems healthy by controlling
host populations.
• Ex: tapeworms, ticks, etc.
• Symbiosis – a long-lasting
and physically close
relationship in which at
least one organism
benefits.
• Herbivory: An animal
feeding on a plant
Lesson 5.2 Species Interactions
Mutualism (+/+) and
Commensalism (+/0)
Lichen: a symbiotic relationship
between a fungus and a photosynthetic
partner, such as an alga
•
Mutualism: a
relationship in which two
or more species benefit
• Ex: pollination
•
Commensalism: a
relationship in which one
species benefits while
the other is unaffected
Did You Know? Symbiosis describes a longlasting and physically close relationship
between species in which at least one
species benefits.
Objectives Revisited
• Discuss the factors that influence an organism’s niche
• Compare and contrast predation, parasitism, and
herbivory
• Describe mutualism and commensalism
Lesson 5.3 Ecological Communities
The sun provides the energy for
almost all of the ecological
communities and species
interactions on Earth.
Objectives
• Explain the difference between a producer and a
consumer
• Explain the effect of inefficient energy transfer on
community structure
• Describe how feeding relationships can have both
direct and indirect effects on community members
Lesson 5.3 Ecological Communities
Primary Producers (Autotrophs)
• Capture energy from the sun or
from chemicals and store it in the
bonds of sugars, making it
available to the rest of the
community
• Energy from the sun is captured by
plants, algae, or bacteria through
photosynthesis.
• Sunlight used to convert carbon
dioxide and water into sugars,
releasing oxygen along the way
• Energy from chemicals is captured
by some bacteria through
chemosynthesis.
Did You Know? Deep-sea vents, far from
sunlight, support entire communities of fish,
clams, and other sea animals, which depend
on energy converted through
Checkpoint
• What is the primary difference between photosynthesis
and chemosynthesis?
Lesson 5.3 Ecological Communities
Consumers (Heterotrophs)
• Rely on other organisms for energy
and nutrients
• Herbivores: plant-eaters
• Carnivores: meat-eaters
• Omnivores: combination-eaters
• Detritivores and decomposers:
recycle nutrients within the ecosystem
by breaking down nonliving organic
matter
• Detrivores consume nonliving organic
material; decomposers break down
nonliving organic material
• Use oxygen to break bonds in sugar
and release its energy through cellular
respiration (primary producers do this,
too)
California Condor
Did You Know? Scavengers, such as
vultures and condors, are just large
detritivores.
Lesson 5.3 Ecological Communities
Energy in Communities
• An organism’s rank in a
feeding hierarchy is its
trophic level.
• Primary producers always
occupy the first trophic level
of any community.
• In general, only about
10% of the energy available
at any trophic level is
passed to the next; most of
the rest is lost to the
environment as heat.
• Eating at lower trophic
levels decreases
biological footprint
QuickTime™ and a
decompressor
are needed to see this picture.
Pyramid of Energy
Lesson 5.3 Ecological Communities
Numbers and Biomass in
Communities
• A trophic level’s
biomass is the mass
of living tissue it
contains.
• In general, there are
more organisms and
greater biomass at
lower trophic levels
than at higher ones.
QuickTime™ and a
decompressor
are needed to see this picture.
Checkpoint
• What happens to energy that is not passed from one
trophic level to the next, or used to power life
processes?
Lesson 5.3 Ecological Communities
Food
Chains
and Webs
• Food chain: Linear
series of feeding
relationships
• Food web: Shows
the overlapping and
interconnected food
chains present in a
community
QuickTime™ and a
decompressor
are needed to see this picture.
Checkpoint
• Why are most communities best represented with a
food web instead of a food chain?
Lesson 5.3 Ecological Communities
Keystone Species
• Species that have strong
and/or wide-reaching
effects on a community
• Removal of a keystone
species can significantly
alter the structure of a
community.
Lesson 5.4 Community Stability
A 2010 report on invasive
species suggests that they cost
the U.S. $120 billion a year in
environmental losses and
damages.
Invasive kudzu
Objectives
• Describe what happens to a community after a
disturbance
• Explain the conditions necessary for a species to
become invasive
Lesson 5.4 Community Stability
Ecological Disturbances
• A community in equilibrium
is generally stable and
balanced, with most
populations at or around
carrying capacity.
• Disturbances or changes in
the environment can throw
a community into
disequilibrium.
• Severe disturbances can
cause permanent changes
to a community and initiate
a predictable series of
changes called succession.
Forest fire
Lesson 5.4 Community Stability
Primary Succession
• Occurs when there are no traces of the original community
remaining, including vegetation and soil
• Bare expanse of rock, sand, or sediment is exposed for the first time
• Pioneer species, such as lichens, are the first to colonize.
• The environment changes as new species move in, adding
nutrients and generating habitat.
QuickTime™ and a
decompressor
are needed to see this picture.
Lesson 5.4 Community Stability
Secondary Succession
•
Occurs when a disturbance dramatically alters a
community but does not completely destroy it
•
•
•
At least the soil from the previous ecosystem remains
Common after disturbances such as fire, logging, or
farming
Occurs significantly faster than primary succession
QuickTime™ and a
decompressor
are needed to see this picture.
Checkpoint
• Why does secondary succession usually happen
faster than primary succession?
Lesson 5.4 Community Stability
Succession in Water
• Primary aquatic succession occurs when an area fills
with water for the first time.
• Disturbances such as floods or excess nutrient runoff
can lead to secondary aquatic succession.
QuickTime™ and a
decompressor
are needed to see this picture.
Lesson 5.4 Community Stability
Climax Communities
• Ecologists once thought
succession leads to stable
“climax” communities.
• Stable community that
completes the succession
process
• Today, ecologists see
communities as temporary,
ever-changing associations
of species.
• Communities are influenced
by many factors and
constant disturbances.
Beech-maple forest, a classic “climax community”
Lesson 5.4 Community Stability
Invasive Species
• Nonnative organisms that spread widely in
a community
• A lack of limiting factors such as predators,
parasites, or competitors enables their
population to grow unchecked.
• Not all invasive species are harmful.
Did You Know? Although the European honeybee is
invasive to North America, it is beneficial because it
pollinates our agricultural crops.
Checkpoint
• What is an invasive species?
Objectives Revisited
• Describe what happens to a community after a
disturbance
• Explain the conditions necessary for a species to
become invasive