Download Lesson 5.3 Ecological Communities

CHAPTER
5
Evolution and Community
Ecology
Black and White, and Spread
All Over
• Zebra mussels and quagga mussels were accidentally
introduced into Lake St. Clair in the late 1980s. This
means they are NON-NATIVE.
• They have since spread throughout the Great Lakes
system and connecting rivers. This means they are
INVASIVE.
• The invasive mussels have a high economic and
ecological cost.
Talk About It The Great Lakes are home to more than
20 native mussel species. Why are the zebra and
quagga mussels so much more destructive than the
lakes’ native mussels?
Lesson 5.1 Evolution
Scientists have identified
and described
over 1.5 million species.
Millions more
have yet to be discovered.
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.
Lesson 5.1 Evolution
Artificial Selection
• Selection under human direction
• Throughout history, humans have chosen and bred
animals and plants with beneficial traits.
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
•
Has resulted in every
form of life on Earth—
today and in the past
Allopatric Speciation
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
• There are five known mass
extinction events, each of
which wiped out a large
proportion of Earth’s
species.
Lesson 5.2 Species Interactions
The zebra mussel has completely
displaced 20 native mussel species in
Lake St. Clair.
Lesson 5.2 Species Interactions
The Niche
•
Describes an organism’s use of resources and functional
role in a community
•
Affected by an organism’s tolerance—its ability to survive
and reproduce under changing environmental conditions
•
Often restricted by competition
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.
• To reduce competition,
species often partition
resources, which can lead to
character displacement.
Resource Partitioning
Lesson 5.2 Species Interactions
Symbiosis-describes a long lasting relationship between
species, in which at least one species benefits
•
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
• Herbivory: An animal
feeding on a plant
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.
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
•
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.
Lesson 5.3 Ecological Communities
The sun provides the energy for
almost all of the ecological
communities and species
interactions on Earth.
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.
• 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 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
•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.
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.
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
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
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
• Pioneer species, such as lichens and mosses, are the first to
colonize.
• The environment changes as new species move in, adding
nutrients and generating habitat.
Lesson 5.4 Community Stability
Secondary Succession
•
•
•
Occurs when a disturbance dramatically alters a
community but does not completely destroy it
Common after disturbances such as fire, logging, or
farming
Occurs significantly 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.
Lesson 5.4 Community Stability
Climax Communities
• Ecologists once thought
succession leads to stable
“climax” communities.
• 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.